Electrical Energy Conversion System for
Pumping Airborne Wind Energy
Jeroen Stuyts
Wouter Vandermeulen
Thesis voorgedragen tot het behalen
van de graad van Master of Science
in de ingenieurswetenschappen:
energie
Promotoren:
Prof. dr. M. Diehl
Prof. dr. ir. J. Driesen
Assessoren:
Prof. dr. ir. W. Dehaene
Prof. dr. ir. J. Meyers
Begeleider:
Dr. ir. A. Wagner
Academiejaar 2012 – 2013
© Copyright KU Leuven
Without written permission of the thesis supervisors and the authors it is forbidden
to reproduce or adapt in any form or by any means any part of this publication.
Requests for obtaining the right to reproduce or utilize parts of this publication
should be addressed to Faculteit Ingenieurswetenschappen, Kasteelpark Arenberg 1
bus 2200, B-3001 Heverlee, +32-16-321350.
A written permission of the thesis supervisors is also required to use the methods,
products, schematics and programs described in this work for industrial or commercial
use, and for submitting this publication in scientific contests.
Zonder voorafgaande schriftelijke toestemming van zowel de promotoren als de
auteurs is overnemen, kopiëren, gebruiken of realiseren van deze uitgave of gedeelten
ervan verboden. Voor aanvragen tot of informatie i.v.m. het overnemen en/of
gebruik en/of realisatie van gedeelten uit deze publicatie, wend u tot Faculteit
Ingenieurswetenschappen, Kasteelpark Arenberg 1 bus 2200, B-3001 Heverlee, +3216-321350.
Voorafgaande schriftelijke toestemming van de promotoren is eveneens vereist voor het
aanwenden van de in deze masterproef beschreven (originele) methoden, producten,
schakelingen en programma’s voor industrieel of commercieel nut en voor de inzending
van deze publicatie ter deelname aan wetenschappelijke prijzen of wedstrijden.
Preface
Designing, selecting, calculating, buying, implementing, testing and affecting. The
things we learned, we did and were trusted with, have been an incredible experience
for us. A very important reason we were able to do this is due to the people that
helped us on this journey.
First of all we would like to thank our promoters prof. Johan Driesen and prof.
Moritz Diehl. Their input has been greatly appreciated and always helped us to get
a clear view of the greater picture.
Next a great amount of thanks goes to Andrew Wagner and Kurt Geebelen. Their
daily dose of help, explanations, patience and experience was of extreme importance
to this work. Without them this master’s thesis would not have been the same. The
entire HIGHWIND team needs to be thanked as well for their warm welcome and
introduction to the project. Especially Greg Horn, who helped us a lot with the
optimization, needs to be mentioned.
We would also like to thank Roland Reekmans and the other people from the
ELECTA lab. Their experience and help with implementing the test set-up is deeply
appreciated. Also Harm Leenders needs to be thanked. His help and answers to all
our questions throughout the entire year have been of the utmost importance. We
owe him a lot.
Working on this master’s thesis has taught us a lot of things and it would not
have been possible if it wasn’t for the good teamwork. Doing a master’s thesis with
two isn’t obvious but it worked out really well for us. Therefore we would also like
to thank each other. And finally we would like to thank those who are dearest to
us: our family, friends and girlfriends, who have supported us not only during this
master’s thesis, but during our entire life and education.
Jeroen Stuyts
Wouter Vandermeulen
i
Contents
Preface
i
Abstract
iv
Samenvatting
v
List of Figures
vi
List of Tables
viii
List of Abbreviations
x
1 Introduction
1.1 Airborne wind energy . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 HIGHWIND project Leuven . . . . . . . . . . . . . . . . . . . . . . .
1.3 Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1
2
4
2 From System Requirements
2.1 System requirements . . .
2.2 Modeling the power flows
2.3 First design . . . . . . . .
2.4 Conclusion . . . . . . . .
to
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First Design
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3 Selection and System Procurement
3.1 ABB . . . . . . . . . . . . . . . . .
3.2 Siemens . . . . . . . . . . . . . . .
3.3 WEG . . . . . . . . . . . . . . . .
3.4 Other Suppliers . . . . . . . . . . .
3.5 Choice of the drive supplier . . . .
3.6 Risk analysis and safety . . . . . .
3.7 Conclusion . . . . . . . . . . . . .
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19
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4 Powering the Plane
4.1 Design of the plane power electronics
4.2 Implementation . . . . . . . . . . . .
4.3 Testing . . . . . . . . . . . . . . . .
4.4 Possible improvements . . . . . . . .
4.5 Conclusion . . . . . . . . . . . . . .
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30
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49
5 The Final System
5.1 The drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
50
50
ii
Contents
5.2
5.3
5.4
5.5
5.6
Assembly . . . . . . . . .
The switchboard . . . . .
Communication . . . . . .
Mistakenly tripping of the
Conclusion . . . . . . . .
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RCD
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during testing
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53
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60
61
Results
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62
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81
7 Conclusions, Leading to the Future
7.1 Concluding the design . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2 The future of testing . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3 Beyond testing: electricity production . . . . . . . . . . . . . . . . .
82
82
83
85
A The Full Siemens Quote
89
6 Testing the Drives and Implementation of the
6.1 Testing of the carousel drive . . . . . . . . . . .
6.2 Testing of the winch drive . . . . . . . . . . . .
6.3 Power loss calculation . . . . . . . . . . . . . .
6.4 Curve fit . . . . . . . . . . . . . . . . . . . . . .
6.5 Implementation . . . . . . . . . . . . . . . . . .
6.6 Conclusion . . . . . . . . . . . . . . . . . . . .
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B Datasheets
98
B.1 Carousel motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
B.2 Winch motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
C The Full MAT
102
D Reliability Calculations
109
E Other Information
E.1 Contact information . . . . . . .
E.2 IP rating . . . . . . . . . . . . .
E.3 The full Vandecappelle NV quote
E.4 Used test equipment . . . . . . .
E.5 Losses in the components . . . .
113
113
114
115
117
118
Bibliography
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119
iii
Abstract
Airborne wind energy offers great opportunity to harvest wind energy, with much
advantages over traditional wind turbines. To fully develop this technology, advanced
test set-ups are required. In this master’s thesis an electrical energy conversion
system is designed to convert the harvested mechanical energy and to power the
test set-up. This means selecting and purchasing the correct converters, motors,
generators, electronic components, safety gear etc. Since this master’s thesis fits
in a bigger research group that tries to optimize the amount of energy that can be
harvested, also the effect of the electrical energy conversion on that optimization is
researched.
To achieve this, system requirements were translated to a real world system. A
Siemens drive system, containing among others converters and motors, was tailored
and combined with all the other electrical components to create an electrical system
design. While doing this, safety was always kept in mind; this means protecting
against all faults, electrical and non-electrical, that could harm people or the set-up
itself. This was then all combined in an initial, non-final, test set-up. The performance of this set-up was measured and turned into analytical curves, which could
be implemented in the optimization program.
The results show that the electrical system has a significant influence. Overlooking or simplifying it by means of a single efficiency or simple models, results in a
suboptimal outcome. The difference between the optimized mechanical output and
optimized electrical output is already a couple of percentage points. However it is
shown that by (slightly) overdimensioning, the influence will further increase. It is
also shown that designing an electrical energy conversion system is a complex task
which should not be rushed. The effect on the overall operations of the system and
the impact on safety is substantial.
The effect of the electrical energy conversion on an actual set-up and on an
optimization program is very important, even for a mechanical problem like wind
energy harvesting. It is surely this form of energy that will be used by all the people
and companies enjoying green energy.
iv
Samenvatting
Airborne wind energy biedt interessante mogelijkheden om windenergie te oogsten.
Bovendien zijn er ook vele voordelen ten opzichte van traditionele windturbines. Om
deze technologie te ontwikkelen, zijn geavanceerde testopstellingen nodig. Voor deze
masterproef werd een elektrisch omvormingssysteem ontwikkeld om de geoogste mechanische windenergie om te zetten en om de gehele testopstelling van elektriciteit te
voorzien. Hiertoe dienden geschikte convertoren, motoren, generatoren, elektronica,
veiligheden etc. geselecteerd en aangekocht te worden. Omdat deze masterproef
kadert in een groter onderzoeksproject, dat tot doel heeft de hoeveelheid geoogste
energie te optimaliseren, werd ook de invloed van het elektrisch omvormingssysteem
op deze optimalisatie onderzocht.
Om dit te bereiken, werden systeemvereisten vertaald naar een reëel systeem.
Een drive systeem van Siemens, bestaande uit o.a. convertoren en motoren, werd
afgestemd en gecombineerd met alle andere elektrische componenten om zo een
totaal elektrisch ontwerp te bekomen. Hierbij is veiligheid, zowel elektrische als
niet-elektrische, altijd een prioriteit geweest. Dit houdt in dat er bescherming wordt
geboden tegen alles wat personen of de opstelling zou kunnen schaden. Het geheel
werd geïmplementeerd in een eerste testopstelling welke volledig werd gekarakteriseerd en in analytische curves gegoten. Deze curves werden nadien geïmplementeerd
in het optimalisatieprogramma.
De resultaten tonen aan dat het elektrische systeem een niet-verwaarloosbare
invloed heeft op het geheel. Dit over het hoofd zien of vereenvoudigen, door een enkele
efficiëntie of eenvoudige modellen, leidt tot nonoptimale resultaten. Het verschil
tussen de geoptimaliseerde elektrische waarden en de geoptimaliseerde mechanische
waarden bedraagt al enkele procentpunten. Er wordt ook aangetoond dat bij een
(licht) overgedimensioneerd systeem de invloed nog veel groter is. Er wordt ook
aangetoond dat het ontwerpen van een elektrisch omvormingssysteem een complexe
taak is die grondig moet worden uitgevoerd. Het effect op de algemene werking en
de veiligheid is immers substantieel.
Het effect van de elektrische omvorming op de opstelling en de optimalisatie is
dus heel belangrijk, zelfs bij een voornamelijk mechanisch proces zoals het oogsten
van windenergie. Het is immers de elektrische energie die door mensen en bedrijven
gebruikt zal worden als groene stroom.
v
List of Figures
1.1
The ground station of HIGHWIND: the carousel [9] . . . . . . . . . . .
2.1
Torque-rotational speed characteristic for the winch motor according to
simulations of one cycle . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power flow according to simulations of one cycle . . . . . . . . . . . . .
The required torque-rotational speed and power-rotational speed
characteristic of the carousel motor [9] . . . . . . . . . . . . . . . . . . .
Power flow based on Figure 2.2 with an additional 1kW of losses, used
for the model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Model results for the power flow for a generator and a braking chopper
Model results for the power flow for a generator, a battery and a braking
chopper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
First electrical design based on a DC bus . . . . . . . . . . . . . . . . .
First electrical design based on an AC bus . . . . . . . . . . . . . . . . .
2.2
2.3
2.4
2.5
2.6
2.7
2.8
3.1
3.2
3.3
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
The working principle of the ABB proposal . . . . . . . . . . . . . . . .
The modular Siemens proposal, a schematic overview can be found in
Figure 5.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Possible testing location with a 300 m range from a local grid connection,
source: Google Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transmission power loss for a system which needs 80 W and is connected
with a 42 Ω cable. The red vertical line indicates the required minimal
voltage for this case. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Plane power circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AC/DC converter top 100-112 . . . . . . . . . . . . . . . . . . . . . . . .
OPEN UPS board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuration of all components . . . . . . . . . . . . . . . . . . . . . .
Resistance measurement cable . . . . . . . . . . . . . . . . . . . . . . . .
Temperature measurement cable on cardboard with 200 W load and
230 V input. The load is switched off at t = 11,5 min. . . . . . . . . . .
Temperature measurement cable on aluminum with 200 W load and
230 V input. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reliability of the original system . . . . . . . . . . . . . . . . . . . . . .
Separate DC bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
6
7
8
12
13
13
15
17
20
22
26
34
35
36
37
38
39
40
40
42
43
vi
List of Figures
4.11 Reliability of separate DC bus. Two ‘groups’ and thus two OPEN UPS
boards are used to calculate this. . . . . . . . . . . . . . . . . . . . . . .
4.12 Secured DC bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.13 Power switch of the secured DC bus . . . . . . . . . . . . . . . . . . . .
4.14 Reliability of the secured DC bus - calculated for two OPEN UPS boards
4.15 Switched DC bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.16 Switchboard of the switched DC bus . . . . . . . . . . . . . . . . . . . .
4.17 Reliability of the full switchboard system . . . . . . . . . . . . . . . . .
44
45
46
46
47
48
48
5.1
5.2
5.3
5.4
Schematic
Schematic
Schematic
Schematic
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51
56
57
58
6.1
6.2
6.3
Efficiency map of the carousel drive in motor mode . . . . . . . . . . . .
Efficiency map of the winch drive . . . . . . . . . . . . . . . . . . . . . .
Predicted maximal efficiency for a certain mechanical power of the drives,
derived from the data provided by Siemens . . . . . . . . . . . . . . . .
Efficiency curve of the carousel drive . . . . . . . . . . . . . . . . . . . .
Efficiency curve of the winch drive . . . . . . . . . . . . . . . . . . . . .
Mechanical and electrical power during a pumping cycle. . . . . . . . . .
Mechanical optimized orbit (a) and electrical optimized orbit (b) for
4 m/s wind speed in a rotational speed - torque map . . . . . . . . . . .
Mechanical optimized orbit (a) and electrical optimized orbit (b) for
10 m/s wind speed in a rotational speed - torque map . . . . . . . . . .
Optimized orbits for 10 m/s wind speed without winch drive constraints
in a rotational speed - torque map . . . . . . . . . . . . . . . . . . . . .
64
66
6.4
6.5
6.6
6.7
6.8
6.9
7.1
7.2
overview
overview
overview
overview
of
of
of
of
the
the
the
the
drives . . . . .
plane, reworked
switchboard .
final system .
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version of
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4.2 . . .
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Implementation of the drives for the test set-up . . . . . . . . . . . . .
The effect on power fluctuations by phase shifting, the cycles are for an
electrical power optimization at 4m/s wind speed . . . . . . . . . . . . .
70
75
76
78
79
80
81
83
86
E.1 Losses in the partial load range for Active Line Modules and Smart Line
Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
E.2 Losses in the partial load range for Motor Modules . . . . . . . . . . . . 118
vii
List of Tables
2.1
2.2
2.3
2.4
Maximal winch motor characteristics based on [9] . . . . . . .
Maximum winch motor characteristics based on simulations . .
Nominal winch motor characteristics based on a group decision
Nominal carousel motor characteristics . . . . . . . . . . . . . .
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6
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9
The quote made by ABB (price without VAT) . . . . . . . . . . . . . .
The quote made by Siemens, the full quote can be found in Appendix A
(price without VAT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 The quote made by WEG (price without VAT) . . . . . . . . . . . . . .
3.4 The quote made by Vandecappelle NV, the full quote can be found in
Appendix E.3 (price without VAT) . . . . . . . . . . . . . . . . . . . .
3.5 Comparison between the drive suppliers via a scoring system on 100 . .
20
4.1
4.2
4.3
4.4
4.5
4.6
System requirements . . . . . . . . . . . . . .
Battery data for powering the plane . . . . .
Comparison of the different designs . . . . . .
Properties of Top 100-112 [36] . . . . . . . . .
Properties of the OPEN UPS board [22] . . .
Summary table, comparing the effect of faults
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31
32
35
36
37
47
6.1
6.2
6.3
Holding torque measurement . . . . . . . . . . . . . . . . . . . . . . . .
Power losses of the set-up . . . . . . . . . . . . . . . . . . . . . . . . . .
The highest measured efficiency of the carousel drive in motor mode for
a certain mechanical power demand is compared with the highest
maximal calculated efficiency. . . . . . . . . . . . . . . . . . . . . . . . .
The efficiency of operating points with the same mechanical power is
compared with the maximal calculated efficiency at that mechanical
power for the carousel drive (in this case 500 W). . . . . . . . . . . . . .
The highest measured efficiency of the winch drive in motor mode for a
certain mechanical power demand is compared with the highest maximal
calculated efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The highest measured efficiency of the winch drive in generator mode for
a certain mechanical power demand is compared with the highest
maximal calculated efficiency . . . . . . . . . . . . . . . . . . . . . . . .
67
68
3.1
3.2
6.4
6.5
6.6
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for
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. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
the different designs
23
24
26
28
71
71
71
72
viii
List of Tables
6.7
6.8
6.9
6.10
6.11
6.12
6.13
6.14
6.15
6.16
The efficiency of operating points with the same mechanical power is
compared with the maximal calculated efficiency at that mechanical
power for the winch drive in motor mode (in this case 500 W). . . . . .
The efficiency of operating points with the same mechanical power is
compared with the maximal calculated efficiency at that mechanical
power for the winch drive in generator mode (in this case 1000 W). . . .
Solution of the least squares method for the carousel drive . . . . . . . .
Solution of the least squares method for the winch drive . . . . . . . . .
The efficiency of operating points with the same mechanical power is
compared with the curve fit efficiency at that mechanical power for the
carousel drive (in this case 500 W). . . . . . . . . . . . . . . . . . . . . .
The efficiency of operating points with the same mechanical power is
compared with the curve fit efficiency at that mechanical power for the
winch drive in generator mode (in this case 1000 W). . . . . . . . . . . .
Results for the mechanical optimized orbit at 4 m/s . . . . . . . . . . .
Results for the electrical optimized orbit at 4 m/s . . . . . . . . . . . . .
Results for the mechanical optimized orbit at 10 m/s . . . . . . . . . . .
Results for the electrical optimized orbit at 10 m/s . . . . . . . . . . . .
72
72
74
74
75
76
78
78
80
80
B.1 Datasheet of carousel motor and gearbox provided by Siemens . . . . . 99
B.2 Datasheet of the winch motor and gearbox as found in [31] . . . . . . . 101
E.1
E.2
E.3
E.4
Important contacts for this thesis . . . . . . .
Meaning of the IP rating [19] . . . . . . . . . .
The full Vandecappelle NV quote . . . . . . .
Test equipment used in testing the drives at the
ESAT . . . . . . . . . . . . . . . . . . . . . . .
. . .
. . .
. . .
‘labo
. . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
grote machines’ of
. . . . . . . . . . .
113
114
115
117
ix
List of Abbreviations
Abbreviations
AREI
AWE
EMC
GPS
HSE
IM
IMU
LiPo
MAT
MCB
MTBS
MTTF
OLE
OPC
PB
PE
PLC
PLC
PN
PMSM
PV
RC
RCD
SMC
TCP/IP
UPS
VPM
XML
General regulations for electrical installations (Dutch: Algemeen reglement
op de technische installaties)
Airborne wind energy
Electromagnetic compatibility
Global position system
Health - Safety - Environment
Induction machine
Inertial measurement unit
Lithium polymer
General risk assessment for the acquisition and handling of Machines,
Apparatuses en Test-set-ups
Miniature circuit breaker
Mean time between failure
Mean time to failure
Object linking and embedding
OLE for process control
PROFIBUS
Protective earth
In the context of PN: Programmable logic controller
In the context of the plane: Power line communication
PROFINET
Permanent magnet synchronous machine
Photovoltaic
Radio controlled
Residual-current device
Sensor module cabinet-mounted
Transmission control protocol and internet protocol
Uninterruptible power supply
Voltage protection module
Extensible markup language
x
Chapter 1
Introduction
During the last decade climate change and global warming have become a hot topic.
Increasing greenhouse gas concentrations in the atmosphere is one of the causes. The
source of this increase is most likely human, like transport and energy generation.
Therefore in 2010 the European Commission proposed the ‘Europe 2020’ package.
This package states three objectives considering the greenhouse gas emissions and
energy production/usage for 2020 [12]:
• A 20 % reduction in emission of greenhouse gasses
• A 20 % improvement in energy efficiency
• A 20 % share of renewable energy sources in energy consumption
The third point, a larger share of renewable energy, will result in an increase of hydro
plants, PV installations, wind power installations and other renewable energy sources
like geothermal plants. For this master’s thesis, the wind power installations are
the most interesting. In 2012 wind power installations covered 7 % of the European
energy consumption [13]. Most of these wind power installations are the regular
horizontal axis wind turbines, but alternatives are available: vertical axis wind
turbine Savonius type, vertical axis wind turbine Darrieus type and airborne wind
energy (AWE). In this master’s thesis the electrical energy conversion system of an
AWE system will be discussed.
1.1
1.1.1
Airborne wind energy
Introduction to airborne wind energy
AWE refers to the harvesting of wind energy with the use of flying objects. This
object can be a soft kite, an airplane or even some sort of balloon. AWE has some
advantages when compared to regular wind turbines:
• Absence of a large tower: this results in a lower material cost and will lower
the total installation cost considerably
1
1.2. HIGHWIND project Leuven
• Higher heights are easier to reach (only a long cable is required instead of a
large tower): this will give the AWE system access to higher wind speeds and
a more uniform wind
• Less visible: due to the long tether instead of a tower an AWE system is less
visible and therefore less visually distracting
These advantages make it an attractive alternative to regular wind turbines. However
there are some disadvantages which may not be ignored:
• Planes and kites require constant monitoring: if there is no wind the plane/kite
will not be able to stay in the air by itself; it is intrinsically unstable
• Planes and kites have to be controlled in order to generate power (for instance
by flying a certain trajectory), this requires fast and accurate control
AWE is as an interesting possibility for wind energy harvesting if the disadvantages
can be omitted. Fast, accurate, reliable and stable control techniques can achieve
this.
1.1.2
Different strategies
Different strategies exist for AWE: onboard generation versus ground based generation.
Onboard generation systems use (an) onboard turbine(s). By flying crosswind
the kite/plane flies in high speed loops perpendicular to the wind. The onboard
turbine(s) can then generate power and this power is sent to the ground via a power
cable (e.g. MAKANI POWER [21]).
Ground based systems have a generator in a ground station. The pulling force on
the tether, connecting the kite/plane to the ground station, when flying crosswind is
used to generate power (strategy of the HIGHWIND project).
Apart from the difference in generation principles, the flying objects can also
differ: flexible wing versus fixed wing systems. A kite (e.g. SkySails [33]) is an
example of a flexible wing and a model glider plane (strategy of the HIGHWIND
project) is an example of a fixed wing.
1.2
HIGHWIND project Leuven
The HIGHWIND project is a fixed wing ground based airborne wind energy project
with rotating start. The project will use a glider model plane connected via a tether
to a ground station (the carousel).
The ground station (see Figure 1.1) has two main functions: launching the plane
and generating power. Launching the plane is realized by the carousel drive. This
drive (electrical motor ‘carousel motor’ + motor controller) will make the T-shaped
part of the carousel rotate. This will make the plane fly in a circular trajectory
around the carousel. The speed on this trajectory is specified by both the carousel
2
1.2. HIGHWIND project Leuven
Figure 1.1: The ground station of HIGHWIND: the carousel [9]
motor’s rotational speed and the tether length. This tether is wound on a winch, of
which the rotational speed is controlled by the winch drive (electrical motor ‘winch
motor’ + motor controller).
When a sufficient high speed is reached, the plane will use its kinetic energy to
change its circular trajectory into a power orbit. This power orbit is a crosswind
loop which will generate a large pulling force on the tether and thus a large torque
on the winch and winch motor. If this torque is combined with reeling out the tether,
power can be generated (reel-out phase). Of course the tether has a finite length and
at some point the tether should be reeled back in (reel-in phase). During this reeling
in, the plane will change its trajectory (no longer crosswind) in order to minimize
its drag and thus the energy cost of the reel-in phase. On average these trajectories
(reeling in and out) should have a positive energy balance: energy is generated. Such
a cycle is called a pumping cycle.
The practical realization of the carousel is only a small part of the HIGHWIND
project. The aim of the project is threefold:
• Finding the most optimal power orbit for an AWE system.
• Finding a safe take-off and landing procedure for the plane.
• Development of a feedback control system ‘model predictive control’, which
should allow to control the plane in the unpredictable outdoor conditions.
3
1.3. Thesis
1.3
1.3.1
Thesis
Goal of the thesis
In the original master’s thesis proposal, the initial goal of this thesis was stated as:
“A pair of master’s students will be responsible for selecting, purchasing, installing,
and testing the power electronics for the motor driving the winch that reels the kite
in and out, the power electronics for the motor driving the carousel arm, as well as a
petrol powered generator of sufficient capacity”. During the master’s thesis, this goal
was changed considerably. Some important aspects that are treated are:
• Designing, selecting, purchasing and testing the carousel drive (motor + motor
controller)
• Designing, selecting, purchasing and testing the winch drive (motor + motor
controller)
• Designing, selecting, purchasing and testing the power electronics for the plane
• Designing, selecting and purchasing a full electrical power system for the entire
set-up
• Integrating the drives in the optimization software and finding the effect on
the most optimal power orbit
Hence the title: Electrical Energy Conversion System for Pumping Airborne
Wind Energy.
1.3.2
Modus operandi
The modus operandi of the master’s thesis is: the initial system requirements are
translated into a preliminary design (chapter 2) which leads to an actual design after
consulting with the industry (chapter 3). The same is done for the plane’s power
electronics (chapter 4). These designs are then implemented and combined in a full
electrical power system (chapter 5). The drives are then tested and are integrated in
the optimization of the power orbits (chapter 6). Finally some future improvements
are worked out (chapter 7).
4
Chapter 2
From System Requirements to a
First Design
In this chapter the system requirements are discussed. Since it is a non-trivial task
to give detailed system requirements for such a test set-up, several requirements were
given at the start of this thesis and in previous ones that all differ in some aspects.
These are then combined to form a first electrical design. This design is the basis of
the thesis and was initially used to contact suppliers.
To have a better understanding of the energy flows in this system, a model was
developed. Based on this, some preliminary conclusions can be drawn. Partially
based on this model, it was decided that a generator is not (yet) required.
2.1
System requirements
Based on the carousel designed by Mathias Clinckemaillie during his master’s thesis [9],
some major components can be identified and dimensioned. Another input to
dimension the components, is the data received from simulations from other team
members. These simulations provide a great deal of detail for torque and rotational
speed characteristics. They however do not provide a correct order of magnitude
due to mismodeling of the system (the exact size and model of the plane was not
yet chosen at that moment). Furthermore this data is subject to variables like the
wind speed. This data is thus only used in an upscaled version and to give an idea
about the relative differences. Throughout the year the system requirements were
gradually changed so correct dimensioning was always very difficult. A maximum
budget was not stated, but it is preferred that the total cost stays under €30 000.
2.1.1
Winch drive
The winch drive consists of the winch motor and the winch converter (motor controller). The winch motor is used to rotate the winch, which controls the tether
length. The winch converter is used to provide power to the winch motor.
5
2.1. System requirements
30
25
Torque (Nm)
20
15
10
5
0
−400
−200
0
200
400
Rotational speed (rpm)
600
800
Figure 2.1: Torque-rotational speed characteristic for the winch motor according
to simulations of one cycle
Nominal characteristics
Based on [9] the winch motor should be able to cope with a force of 1800 N at a
tether velocity of 6 m/s (generator mode). It should also be able to pull 500 N at
8 m/s (motor mode). The winch has a radius of 10 cm. The nominal parameters for
the winch motor are then calculated and stated as in Table 2.1. The values used
by [9] are however very rudimentary and are thus very uncertain.
Table 2.1: Maximal winch motor characteristics based on [9]
Maximal rotational speed
Maximal torque
Maximal power
764 rpm
180 Nm
10,8 kW
The simulation shows something completely different. These simulations are
based on an optimization for the entire power generating cycle. They however still
have a lot of degrees of freedom left, for instance the aerodynamic model of the plane
is not yet correct. Based on the torque-speed characteristic (Figure 2.1) and the
power flow (Figure 2.2) Table 2.2 is found. The large difference with the previous
values is thus due to mismodeling and variables that are not yet known.
Another important comment is that the maximal rotational speed of 773 rpm is
not a real maximum. It occurs when the plane is retracting (reel-in phase), the actual
system requirement is that the plane should retract as fast as possible. 773 rpm is
thus an indication but not a constraint. Because of the great amount of uncertainty a
decision was made together with professor Diehl, Kurt Geebelen and Andrew Wagner
6
2.1. System requirements
400
← Maximum = 361 W
200
Power (W)
0
−200
−400
−600
−800
← Minimum = −890 W
−1000
0
1
2
3
4
5
6
7
Time (s)
Figure 2.2: Power flow according to simulations of one cycle
Table 2.2: Maximum winch motor characteristics based on simulations
Maximum rotational speed
Maximum torque
Maximum power
773 rpm
28 Nm
890 W
Table 2.3: Nominal winch motor characteristics based on a group decision
Nominal rotational speed
Nominal torque
Nominal power
1000 rpm
95 Nm
10 kW
to use the values in Table 2.3. These values are definitely an overestimation and
therefore future proof.
Because the winch converter should supply power to the winch motor, its nominal
power is also 10 kW. Furthermore it should also be able to send power back, assuring
four quadrant operation of the winch motor.
Other requirements
The winch motor should have some holding torque and since torque is needed at
low speeds, external cooling is required as well. Because rapid jumps in torque and
speed setpoints will be present, as can be seen in Figure 2.1, the motor should also
be dynamic. Since it is the main generator it should be efficient. Furthermore a
lightweight motor is preferred because it will be mounted in a rotating cage. An
7
2.1. System requirements
Figure 2.3: The required torque-rotational speed and power-rotational speed
characteristic of the carousel motor [9]
encoder with homing function should be included to provide feedback and it is also
needed to run the main control software.
A very important remark is that because the motor is mounted in a rotating
cage, its cables must go through a slipring. This might have consequences on the
encoder accuracy because sliprings are a source of noise.
Because of all these requirements a Permanent Magnet Synchronous Machine
(PMSM) is a suitable option. It is lightweight, efficient and dynamic at the same
time.
2.1.2
Carousel drive
The carousel drive consists of the carousel motor and the carousel converter (motor
controller). The carousel motor is used to rotate the carousel. The carousel converter
is used to provide power to the carousel motor.
Nominal characteristics
According to [9] the carousel motor should be able to deliver 170 Nm at 60 rpm,
which equals 1 kW. This can be seen in Figure 2.3. These values were calculated
using the drag of a plane with a 2 m wingspan at 5 m from the center of the carousel.
An additional 20 % loss is included to account for the drag of the carousel itself and
losses in the transmission and bearings. Since the plane might be bigger in the future
and a stronger motor will get the rotating construction up to speed faster, it was
decided to use the nominal values in Table 2.4 as a basis. The change to 100 rpm is
because a gearing system with a ratio i = 2/3 is going to be used.
8
2.1. System requirements
Table 2.4: Nominal carousel motor characteristics
Nominal rotational speed
Nominal torque
Nominal power
100 rpm
382 Nm
4 kW
Because the carousel converter should supply power to the carousel motor, its
nominal power is also 4 kW. Sending power back isn’t a necessity for this converter
since it is operated in only one quadrant. However the energy recuperated in braking
the carousel can be sent back, otherwise it should be transferred to heat using a
braking chopper.
Other requirements
An encoder should be included since the inertia of the system will constantly change
while the nominal speed should be maintained. The encoder data is also needed to
run the main control software. This motor should preferably be simple and robust;
therefore an induction machine (IM) is a suitable option.
2.1.3
Power source
In the original thesis draft it is stated that a generator is required to supply the
requested power. However as will be explained later (Section 2.2) there are better
alternatives. The reason for using a generator is to be able to do islanding. This
means that tests could be done at very remote locations where safety is ensured.
The generator should be able to supply the power for the drives, which will need
a three phase 400 V connection. Auxiliaries will need a single phase 230 V outlet.
The issue with choosing a generator is the correct dimensioning, which depends
on all connected devices. With the winch motor dimensioned at 10 kW and the
carousel motor at 4 kW a generator of 18 kW should have enough reserves to power
all the auxiliaries.
2.1.4
Plane
The plane needs power for onboard electronics as well as power for the servos that
drive its flight control surfaces. It is estimated that the total power draw will be 80 W.
This power is delivered via a single phase 230 V connection. The communications
between the plane and the ground station also occur over this line using power line
communication (PLC). The detailed system requirements for the plane can be found
in Section 4.1.1.
9
2.1. System requirements
2.1.5
Others
Weather proofing
Since all the equipment will be mounted on a trailer for outdoors testing, it should
be dust and water proof. The standard way of quantifying this is using an IP rating.
Appendix E.2 shows the meaning of the numbers based on [19]. Equipment that is
outdoors without any protection needs to be at least IP54. Other equipment that
can be mounted in a cabinet (that should then be IP54 as well) needs to be at least
IP20.
Safety components
Safety components should be included to ensure safe operation of the system under
nominal load as well as the possibility to shut off everything quickly when something
goes wrong. Furthermore protection against direct and indirect contact should be
ensured. This is achieved by incorporating differential breakers (or residual-current
devices: RCDs) 1 and circuit breakers (or miniature circuit breakers: MCBs) 2 into
the design. Also, physical protection for all parts under voltage should be included 3 .
For mechanical safety a brake should be included in the drives such that everything
is secured in place if something should go wrong.
The plane will be a flying lightning target, but this cannot be avoided (connecting
a grounding cable and lightning antenna to the plane would increase the weight
drastically). The only solution is to avoid flying in electrical storms.
Auxiliaries
Several auxiliary devices will be attached to the carousel and draw power. These
include multiple computers for control and monitoring, sensors and cooling for certain
components. It is very difficult to predict the power draw of all these components
(most of which have not been chosen yet), but it is estimated they will not draw
more than 4 kW.
Grid connection
A grid connection is required to connect to the local grid, either to draw power or
to send generated power back to the grid. This connection might be useful if the
generator fails or to test more easily and rapidly. The grid also provides a more
reliable and robust connection that is able to take power back. When looking at a
stand-alone system however, a grid connection is not required.
An RCD protects against direct contact with parts that shouldn’t be under voltage. It detects
if a small current flows to the earth.
2
An MCB protects against indirect contact by detecting short circuit currents.
3
Physical protection protects against direct contact with parts under voltage.
1
10
2.2. Modeling the power flows
Measurement equipment
For monitoring and control actions, measuring equipment might be included in the
set-up. Measuring equipment is also a part of the safety components, but is usually
included in the safety device itself.
Sliprings
Because multiple rotating and stationary parts have to be electrically connected,
sliprings are required. These are also used to transfer data signals.
A first slipring is installed between the carousel and the box that holds the winch,
so all the cables required for the winch motor need to go through here. However,
most of the time the winch motor is operating, the carousel will be stationary. It is
thus important that the sliprings can cope with high currents while stationary, so
that a burn-in is avoided.
A second slipring is installed between the winch (the drum on which the tether is
wound) and the tether. This is used to connect the electronics and communication
signals of the plane (a single phase 230 V connection).
2.2
Modeling the power flows
To get a better understanding of all the power flows and peak power in a stand-alone
system (islanding), a model was developed. This model simulates the power flows
between the batteries and/or generator and the braking chopper for a given power
demand. This power demand is based on the cycle shown in Figure 2.2 plus some
additional auxiliary losses equal to 1 kW. This simulates the effect of the auxiliary
components. The total modeled power can be seen in Figure 2.4. Different scenarios
were modeled to understand which components are the most important. Since the
value of the powers involved isn’t precise, conclusions should be drawn from the
relative differences and trends, not the actual values. The braking chopper is always
present, since this will be the case in reality as well. For all figures positive power
means a power flow from the component and negative power means a power flow to
the component.
2.2.1
Only batteries
In this scenario only a battery and a braking chopper are considered. A battery
would be able to cope with all power fluctuations if its maximum power is higher
than the maximum power of the cycle. Depending on the net energy output of the
cycle, a battery could either be depleted or be charged by one cycle. In the latter
case (net energy production per cycle) the battery would constantly be charged and
once it is full the excess power needs to be burned in the braking resistor. This way
an infinite testing time could be achieved since all needed energy is produced by the
cycle itself. If the battery were to be depleted (net energy consumption of the cycle),
testing time is limited by the battery size.
11
2.2. Modeling the power flows
1.4
1.2
Power (kW)
1
0.8
0.6
0.4
0.2
0
0
1
2
3
4
5
6
7
Time (s)
Figure 2.4: Power flow based on Figure 2.2 with an additional 1kW of losses, used
for the model
2.2.2
Only generator
In this scenario only a generator and a braking chopper are considered. Contacts
with Antec (a generator supplier, see Section 3.4.1) show that power fluctuations
decrease the service life of a generator. It is particularly harmful to operate the
generator below 0, 4Pnominal . Antec advises to overdimension the generator, this
will make power fluctuations smaller (relative to the nominal power), and still make
sure that the generator is always loaded above 40 % of its nominal load. The model
accounts for this by overdimensioning the generator by 40 % and by limiting the
operation of the generator to a load between 40 % and 100 %.
The results are shown in Figure 2.5 and as expected the generator does not go
under its limit. The braking chopper thus burns all excess power.
2.2.3
Batteries and generator
In this scenario all components are present: a generator, a battery and a braking
chopper. The generator is dimensioned as before but the battery now also has a
limited power to be able to show the braking chopper kicking in.
The results are shown in Figure 2.6. The generator still runs continuously and
does not go under its limit. The battery charges when there is an overproduction
due to the generator’s limit and the braking chopper kicks in when the power flow
to the battery is too big. Since the battery is again continuously being charged, all
excess power will have to be burned in the braking resistor once the battery is full.
12
2.2. Modeling the power flows
1.5
Total power demand
Generator
Braking chopper
Power (kW)
1
0.5
0
−0.5
−1
0
5
10
15
20
25
Time (s)
Figure 2.5: Model results for the power flow for a generator and a braking chopper
1.4
Total power demand
Generator
Battery
Braking chopper
1.2
1
Power (kW)
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
0
5
10
15
20
25
Time (s)
Figure 2.6: Model results for the power flow for a generator, a battery and a
braking chopper
13
2.3. First design
2.2.4
Conclusions
When comparing the different scenarios it is clear that a battery alone is a suitable
option. When correctly dimensioned, it is able to cope with all fluctuations. When
a generator is used, with or without batteries, it is subject to power fluctuations.
To cope with these, overdimensioning of the generator is required. Furthermore the
battery needs to be able to cope with the excess power flows, otherwise the braking
chopper needs to be dimensioned bigger as well. This also means that an abundance
of petrol/diesel is being wasted.
A grid connection is another solution. The system is then no longer a stand-alone
system, which limits its testing locations. The grid however is able to cope with
all power fluctuations. It is also able to cope with power generation and power
consumption. This means no battery or generator is required and the braking
chopper can be downsized, since it will only be used for safety purposes. It is also
the only solution that could achieve true power production. A disadvantage however
is a significant voltage drop for long distances with a high current draw.
Because of the disadvantages of a generator and the advantages of a grid connection, it was decided that a generator will not be used. Later on it will also become
clear that using batteries is very expensive (Section 3.4.2). A grid connection with a
long enough cable will provide all the capabilities required, while still being able to
test in remote locations. The only limit is that there should be a grid connection
nearby, which is the case for the selected location were the tests will occur during
the first years (see also Section 3.4.3).
2.3
First design
Based on the requirements listed in Section 2.1 an initial electrical system was
designed. Since most of the power is drawn by the motor and carousel drives (10 kW
and 4 kW), their electrical connection is the basis of the design. There are two
possibilities: a DC bus (Figure 2.7) or an AC bus (Figure 2.8). Both AC and DC
bus systems have advantages and disadvantages, which are outlined in the next two
sections.
2.3.1
DC bus
Description
As can be seen on Figure 2.7, all components are connected to one single DC bus.
The DC bus gets its power from a main (active) rectifier (Converter 1 ), which the
generator and/or grid (Transformer) is connected to. The two motor controllers are
then connected to generate the three phase voltage required to drive the motors.
A second converter (Converter 2 ) is connected to generate the single phase 230 V
grid, required for the auxiliaries and the plane (Plane). An energy storage system
(Battery and/or Supercap) is also included for balancing of the DC bus or energy
storage, as explained in Section 2.2. Finally a braking chopper and resistor (R) are
present, mainly for burning all excess power in case of an emergency.
14
Slipring 1
R
Winch
Motor
R
Slipring 1
Slipring 2
Plane
R
550V DC
Battery
Supercap
Converter 2
Converter 1
Figure 2.7: First electrical design based on a DC bus
Carousel
Motor
Transformer
Auxiliaries
230V AC
400V AC
Generator
2.3. First design
15
2.3. First design
Other components are the sliprings required to connect the rotating to the
stationary parts (Slipring 1 and Slipring 2 ), 230 V outlets for connecting auxiliaries
(Auxiliaries) and safety equipment:
• Fuse or MCB:
• RCD:
• Emergency Button:
• Switch:
Advantages
Practically all common drive systems use an internal DC bus. This design takes
that DC-bus and connects it to the other components. This is a potential money
saver as most of the components are already available in the drive. A DC bus is very
modular since you can connect an off-the-shelf converter and generate any voltage,
AC or DC, that is required.
Since for each connection a converter is required, this can act as a regulator.
This has the advantage that everything is balanced. For the generator and/or grid it
means that the power flow in each phase is the same.
Another advantage is robustness to voltage drops and peaks on the DC bus as
well as on the AC grid (in case of an active rectifier). This is because there is an
intelligent block creating the voltages required, it can thus act on the deviations it
notices.
The battery and/or supercapacitor has the potential to be directly connected to
the DC bus. Chargers and controllers for these components that connect to DC are
however very expensive.
Disadvantages
Since all voltages are created with power electronics, power quality may become
an issue. This could be solved with the correct filters, which eliminate the high
frequency noise.
The components required for this scheme are not mainstream. Most of them
will be sold together (which isn’t necessarily a disadvantage) and especially a DC
battery charger is extremely hard to find. Also DC fuses/circuit breakers and RCDs
are hard to find.
16
2.3. First design
DC
AC
AC
DC
DC
AC
Battery
M
M
Figure 2.8: First electrical design based on an AC bus
2.3.2
AC bus
Components
As can be seen on Figure 2.8 the two drives are connected to an AC bus. This AC
bus can be connected directly to the generator and/or grid or it can be connected via
a central block as drawn here. This block, existing of multiple converters internally,
is basically a three phase uninterruptable power supply (UPS) with an extra 230 V
outlet for the plane and auxiliaries. The usage of this block isn’t required, not even
when there is a need to connect a battery (a separate charger can be used), but
it offers multiple advantages as will be outlined next. Safety components are not
included on this figure, as they would be very similar to the DC bus scheme.
Advantages
The main advantage of this scheme is that the components are far more mainstream.
While they are not necessarily less complex, they are often cheaper. AC battery
chargers for example are far more common than DC ones. Also safety components
for AC systems are far more common. The advantages of using a UPS system, as
drawn in Figure 2.8 are very similar to the advantages of a DC bus. This is because
internally a UPS uses a DC bus to connect its batteries. The main difference is that
17
2.4. Conclusion
this component can be bought as one piece and hence requires no extra programming
or safety analysis. Furthermore compatibility is ensured.
Disadvantages
Since the drives are now only connected to the other components via an AC connection,
an active front end is a necessity (at least for the winch drive) to be able to send
power back. This was not the case for the DC bus, since those DC connections are
always active. If no UPS is used, the system is more sensitive to frequency and
voltage variations. This is particularly a disadvantage for the sensitive components
as they draw their power from the same grid as the drives, which may cause a lot
of variation and (electrical) noise. If a UPS is used, there is a lot of duplication
of components. A three phase grid is now transformed to an (internal) DC grid,
which is then used to build an artificial three phase grid. In the drives this is then
transformed back to a DC-grid. This seems like a waist of components and thus
money. A UPS system is also very expensive as will be outlined in section 3.4.2.
2.4
Conclusion
The system requirements, based on previous work, are a basis for the rest of this
thesis. The uncertainty in the values are however very difficult to cope with. This is
solved by overdimensioning. To get a better understanding of everything, a model
is developed. The power flows are analyzed, together with different ways to buffer
power. This shows that using a grid connection instead of a generator is a better
option, while sacrificing the idea of islanding. Based on the model and the system
requirements an initial design can be developed. Two possibilities emerge: a DC bus
and an AC bus. Both options can be used to contact suppliers and to get their view
on our system. In the next chapter this is done and the designs are thus translated
to reality.
18
Chapter 3
Selection and System
Procurement
Based on the first design explained in Chapter 2 potential suppliers were contacted.
Different suppliers were contacted because of the need for competitive bidding. For
the drives a quote was received from ABB, Siemens and WEG. For the main power
cable and various other electrical components Vandecappelle NV was chosen as
supplier. For the energy storage system SMA was contacted and for the generator
Antec was contacted, however both of these are not required. All contact information
can be found in Appendix E.1.
To choose between the drive suppliers, objective as well as subjective criteria
were used. The head of the ESAT ‘labo grote machines’ was also contacted, as he
frequently buys these items and thus has lots of experience.
Another very important issue is safety. A risk analysis is required to assess the
possible hazards of the system and the correct measures have to be taken accordingly.
3.1
3.1.1
ABB
ABB’s proposal
ABB proposed a main converter design of which the working principle can be seen
on Figure 3.1. The winch motor would be connected to a large active front-end
converter of 15 kW. This is then coupled via a DC connection to a second 5 kW
converter. The specific codes of the components can be found in table 3.1.
For the winch motor an induction machine (IM) with an appropriate gearbox was
proposed. According to them an IM should be dynamic enough, while being much
cheaper than a permanent magnet synchronous machine (PMSM). The proposed
motor is an 11 kW 4-pole IM which weighs 83 kg (without gearbox) and has a 90,4 %
efficiency at full load (without gearbox). [3]. The specific code can be found in Table
3.1.
19
3.1. ABB
Figure 3.1: The working principle of the ABB proposal
Table 3.1: The quote made by ABB (price without VAT)
Component
Winch motor + gearbox
Component proposed
M3AA132SMB4-B5 +
RX77AM132ML
Winch controller
ACS800-11-0016-3 + E200 + K466 +
L502
Carousel motor + gearbox
M3ARF112M4-B5 + R77AM1112
Carousel controller + brak- ACS800-01-0011-3 + E200 + K466 +
ing resistor
L502 + SACE15RE22
Total
Price
€1 748,41
€3 172
€2 041,88
€1 525
€8 487,29
For the carousel motor an IM with an appropriate gearbox was proposed as well.
This one is modified for braking duties, meaning that a special electromagnetic disk
brake is included. The proposed motor is a 4 kW 4-pole IM which weighs 40 kg
(without gearbox) and has an 84,5 % efficiency at full load (without gearbox). [2]
The specific code can be found in Table 3.1. The contact information for ABB can
be found in Appendix E.1.
20
3.2. Siemens
3.1.2
Objective criteria
Table 3.1 shows the prices proposed for the components. The total order would cost
€8 487,29. This includes both motors and all components required to make them
work. When put besides our initial designs (Figure 2.7 and 2.8), various components
come back and only the energy storage system and configuration for the separate
230 V net should be added.
The proposed winch motor is barely capable of delivering the required nominal
torque at the required rotational speed. Therefore a gearbox is proposed to further
raise the motor’s rotational speed and decrease the torque (or to decrease the outgoing
speed and increase the outgoing torque). Since this IM has four poles, its nominal
rotational speed is 1500 rpm. A six pole IM was also available, but it would increase
the weight by 26 kg (while still having the same size). Other criteria like holding
torque, dynamics, efficiency . . . were assured by ABB to be more than adequate. The
only potential problem is the encoder signals going through the sliprings. Previous
experiences had learned them that this might not work. The motor is IP55, which
means it is dust protected and can handle water jets [19].
The proposed carousel motor is easily capable of delivering the required torque at
the required rotational speed, with the correct gearbox fitted. The IM is also robust
enough and can handle the slowing down of the carousel, since it has a specially
adapted brake (braking torque is three times bigger than the nominal torque) and
an extra braking resistor attached to its controller. It is IP55, which means it is dust
protected and can handle water jets [19].
3.1.3
Subjective criteria
Contact with ABB was very sluggish from the start. The entire process took very
long. It was already expressed from the beginning that they had no interest in
supporting a research project. They also stated that the components we were going
to buy were way too cheap and small for them to make any reasonable profit. It
was therefore clear that once we had bought the proposed system, support would be
minimal.
3.2
3.2.1
Siemens
Siemens’s proposal
Siemens proposed a modular system as can be seen on Figure 3.2. An active rectifier
builds up a DC bus which is connected to two motor modules. Each motor module
is connected to its motor with a power cable. The encoder signals from the motor
are sent to an encoder module, which is connected to the motor module as well.
All modules are controlled by a single control unit. The system is therefore very
modular, as adding a component is as simple as connecting to the DC bus and to
the control unit.
21
3.2. Siemens
Figure 3.2: The modular Siemens proposal, a schematic overview can be found in
Figure 5.1
For the winch motor a permanent magnet synchronous machine (PMSM) was
selected. Included are a resolver, a brake and a gearbox. The motor is an 8.2 kW
Simotics PMSM which weighs 51,6 kg (with brake and gearbox) and has a 91 %
efficiency at full load (with gearbox) [31]. The full datasheet is available in Appendix
B.2.
For the carousel motor an IM was selected. Included are an encoder and a
gearbox. The motor is a 4 kW 4-pole IM which weighs 52 kg (with gearbox) and has
an 86,60 % efficiency at full load (with gearbox). The full datasheet is available in
Appendix B.1.
The entire Siemens system is discussed in far more detail in Chapter 5 and the
full quote with all the component numbers is available in Appendix A. The contact
information for Siemens can be found in Appendix E.1.
3.2.2
Objective criteria
Table 3.2 shows the prices of the components. The total order costs €10 146,95.
This includes both motors and all components required to make them work. The
proposed system resembles the DC bus design (Figure 2.7), as one central block
22
3.2. Siemens
Table 3.2: The quote made by Siemens, the full quote can be found in Appendix A
(price without VAT)
Component
Winch motor + accessories
Carousel motor + accessories
Active rectifier + accessories
Component proposed
1FK7105-2AF71-1SH0 + . . .
2KJ1103-1GJ13-1FL1-Z + . . .
6SL3130-7TE21-6AA3 + . . .
Total
Price
€4 917,21
€2 066,77
€3 162,97
€10 146,95
builds up the DC bus, which is then used by the other components. Only the energy
storage system and configuration for the separate 230 V net should be added.
The proposed winch motor requires a gearbox. The nominal outgoing rotational
speed then becomes 1000 rpm, however the machine can go faster, being limited by
the gearbox’s input speed, up to 1600 rpm. This PMSM is a servo motor and is thus
very dynamic. The holding torque and efficiency are also very good. An additional
holding brake is included for safety. The issue with sending an encoder signal over
sliprings was brought up by Siemens as well. They had the best results using a resolver
instead of an encoder.1 Therefore this is being used. The proposed winch motor
is not capable of delivering the required nominal torque at the required rotational
speed. With an added gearbox the nominal output torque becomes 78 Nm, which is
still lower than the estimated required 95 Nm. A PMSM however is capable of very
much overloading [14] and since the required nominal values are an overestimation,
this is not considered a problem. The proposed 8.2 kW machine is the biggest of its
kind; otherwise a larger and heavier form factor would have been necessary which
is also not available with a reliable resolver. Therefore this lightweight machine
was preferred. It is IP64, which means it is dust tight and can handle splashing
water [19].
The proposed carousel motor is easily capable of delivering the required torque at
the required rotational speed, with the correct gearbox fitted. The IM is also robust
enough and should be able to slow the carousel down, as the power can be sent back
to the grid and to an additional braking resistor. It is IP55, which means it is dust
protected and can handle water jets [19].
3.2.3
Subjective criteria
Contact with Siemens was very good from the beginning on. Everything was discussed
via one person, who was always prepared to answer our questions and help us out.
It was already expressed from the beginning that they were interested in supporting
our research project. It was also clear that we would get the support we needed long
after we had bought the components. The level of interaction and interest was truly
remarkable.
A resolver uses analogue signals while an encoder uses digital pulses. A resolver is therefore
more robust to noise, since a lost pulse in an encoder could lead to an error.
1
23
3.3. WEG
Table 3.3: The quote made by WEG (price without VAT)
Component
Carousel motor
Carousel gearbox
Carousel converter
Winch converter
3.3
3.3.1
Component proposed
04B2400400A5ZV
TMCT090020A
FRQWEG00400/400CFW11
FRQWEG01500/400CFW11
Total
Price
€692,87
€529,69
€557,15
€1 088,14
€2 867,85
WEG
WEG’s proposal
The proposal of WEG is very similar to the AC bus design (Figure 2.8). It uses
two separate frequency converters that both connect to the three phase grid. It is
possible to interconnect the machines’ internal DC bus, but it is not required for
operation. Both converters have a passive rectifier on the grid side. Power thus
cannot be sent back and has to be dissipated in a braking resistor. WEG’s product
line in Belgium is limited to small IM’s. Regrettably the size required for the winch
motor cannot be delivered. For the carousel motor a 4 kW 4-pole IM is proposed. It
weighs 44 kg and has an 83,5 % efficiency at full load [38]. The contact information
for WEG can be found in Appendix E.1.
3.3.2
Objective criteria
Table 3.3 shows the prices proposed for the components. The total order would cost
€2 867,85. In this price however, the price of the winch converter is included. It
makes more sense to leave this out and order it together with the winch drive from
another supplier. The total order would then cost €1 779,71. This thus includes the
carousel motor and all components required to make it work.
The proposed carousel motor is easily capable of delivering the required torque at
the required rotational speed, with the correct gearbox fitted. The IM is also robust
enough and can handle the slowing down of the carousel, since it is a brake motor
and also has a braking resistor attached. It is IP55, which means it is dust protected
and can handle water jets [19].
3.3.3
Subjective criteria
Contact with WEG was very good from the beginning on. Our contact expressed
that he wanted to help us in the programming of the frequency drives, so support
would be fine. The product line of WEG is also very simple and clearly organized,
which really helped us in selecting the required drive.
24
3.4. Other Suppliers
3.4
3.4.1
Other Suppliers
Antec
Before it was decided that no generator is required, Antec was contacted. They
provided us with their entire price list and conscientiously answered our questions.
Should a generator be required in the future, it might be worthwhile to give this
company another look.
3.4.2
SMA
SMA was contacted to provide the required components for a full battery powered
system. Based on the information on their site a set-up was configured very similar
to the UPS integrated in the AC bus design, as can be seen on Figure 2.8. Three
converters would be required to build up the three phase AC grid for the motors.
Another converter would be required to build up the single phase AC grid for the
auxiliaries and the plane and a fifth converter would be required to charge up the
batteries. Based on the price information found on their site [34] and the information
acquired from a PhD student this would cost around €18 000 for the converters
alone, batteries thus not included. Therefore the UPS idea was put to rest.
3.4.3
Vandecappelle NV
Vandecappelle NV provided us with the main power cable, electrical cabinets and
accessories and various other electrical components required to make the system
work. The total order can be seen in table 3.4 and adds up to €3 854,81. The full
order can be found in Appendix E.3 and the contact information in Appendix E.1.
The main power cable provides the three phase connection for the drives as
well as power for auxiliaries which are then connected to one of the phases. The
nominal current of the AC-DC converter is 27 A and the nominal power of the drives
is 12,2 kW, which translates into 17,6 A. A 32 A cable was then chosen, since the
next smaller size is 16 A, which would not be sufficient. 32 A should be plentiful for
normal operations with all the possible auxiliaries connected. It is estimated that
300 m is enough for all early tests; Figure 3.3 shows a possible test location for which
it is sufficient. The cable weighs 47,5 kg/100 m, so three pieces of 100 m would be
far more manageable than one cable of 300 m. Since these cables are now basically
extension cords, it is very simple to order extra pieces if longer connections should
be required.
The cabinets are used for mounting the drives and the electrical gear (one for
each). The third cabinet ordered will be used for mounting a computer. The electrical
cabinet accessories include necessary options for these cabinets like locks, ventilation
and also signalization. The cable routing gear includes everything required to connect
the electrical gear and make the necessary electrical connections. The safety gear
includes all necessary MCBs and RCDs to protect the system from direct and indirect
contact. The main RCD is special because it can cope with the residual current of
the filters of the drive (see Section 5.5).
25
3.4. Other Suppliers
Table 3.4: The quote made by Vandecappelle NV, the full quote can be found in
Appendix E.3 (price without VAT)
3 × 100m cable fitted with 1 male and 1 female plug
Electrical cabinets
Electrical cabinet accessories
Cable routing gear
Safety gear
Total
€355,00 per piece
€806,54
€629,57
€406,93
€932,88
€3854,81
Figure 3.3: Possible testing location with a 300 m range from a local grid connection,
source: Google Maps
26
3.5. Choice of the drive supplier
3.5
Choice of the drive supplier
The choice of the drive supplier is very important. Therefore a comparison is made
using the objective and subjective criteria stated above. The objective criteria are
further split in three groups, while the subjective criteria are split in two groups. To
ensure simplicity and compatibility all components are bought from one supplier.
3.5.1
Criteria
Each criterion gets a weighting factor such that the sum adds up to 25. Each supplier
then gets a score (- - , - , + or ++). By multiplying the score with the weighting
factor, a total score on 100 is derived.
Objective criteria
Price The price of the components is an obvious criterion. It is however not
extremely important. As stated before in Section 2.1 the maximum budget is around
€30 000. All of the quotes stay well below that price.
Suitability The suitability criterion states how well the quote fills our needs and
how well it follows the system requirements as stated in 2.1. This is therefore a very
important criterion and thus gets a very high weighting factor.
Technical advantages The technical advantages criterion is included to account
for a variety of advantages that one company might have over another. For example
in the Siemens drives all the control logic is fed from a separate voltage source and
physically separated from the high voltage hardware. This is a huge advantage should
a fault occur. Also future extensibility is included here.
Subjective criteria
Feedback The feedback criterion is the first subjective criterion and describes how
well the company has interacted with us. This is especially important for future
troubleshooting.
Response time The response time criterion is the final (subjective) criterion and
accounts for how long it takes for a company to get back to us. Since this is a
master’s thesis with strict deadlines, we cannot afford to wait very long for an answer.
Already during first contact it was discovered that this is very important.
3.5.2
The results
The results of this comparison can be found in table 3.5. It is obvious that Siemens
has the best result since it scores excellent on all criteria except the price. While
ABB has a clear technical advantage over WEG and it scores similar to Siemens, it
was very difficult and painstaking to contact them. WEG on the other hand lost
27
3.6. Risk analysis and safety
Table 3.5: Comparison between the drive suppliers via a scoring system on 100
Criteria
Weighting
factor
Price
3
Suitability
8
Technical advantage
3
Feedback
6
Response time
5
Total score on 100
Company
ABB Siemens WEG
+
++
+
--56
++
++
++
++
94
++
-+
++
69
on the technical criteria, since it is not able to deliver all components. While their
products are very simple and robust, they cannot cope with the weight, size and
versatility advantages of ABB and Siemens.
3.6
Risk analysis and safety
While some safety components are included in the initial design, it is not clear how
effective these will be in reality. To get a clear view of all the risks and solutions,
the safety department HSE of the KU Leuven was contacted. Together with them
we discussed the safety from an electrical point of view, while also keeping in mind
the entire mechanical system.
The procedure for electromechanical safety was started by filling in a ‘General
risk assessment for the acquisition and handling of Machines, Apparatuses en Test
set-ups’ (MAT) form. The full MAT file (in Dutch) can be found in Appendix C.
The most important hazards are:
• There is a risk of hearing loss
• There is risk of crushing, squeezing, being grasped
• There is a risk of falling and stumbling
• There is a risk of electrocution (direct or indirect)
• There is a chance of burns
The most important solutions based on these hazards are:
• Physical blocking of the motors and all other electrical components
• Electrical screening of all wires and contacts
• Using MCBs
• Using RCDs
28
3.7. Conclusion
A very important remark is that because of the intrinsic danger of the arm
and rotating tethered aircraft, the physical blocking of all mechanical parts during
operation is infeasible. Everybody involved should be kept from the set-up during
operation. It is thus critical that control actions (safety or regular) can be done from
a considerable distance.
Other important things that were brought up by the MAT and that need to be
addressed on the final set-up are:
• Hazards need to be visually marked
• Important instructions need to be present
• All team members should be briefed on the hazards, safety equipment and
normal operation of the electrical system
3.7
Conclusion
This chapter makes the transition from system requirements to reality. Various
companies were contacted to get a clear view of the market. Based on the acquired
information a well motivated decision was made to select Siemens as the drive
supplier. Both on a technical level and a subjective level the company stood out.
As for other components, Vandecappelle NV is able to deliver almost everything
with a good service. Should a generator be required in the future, Antec can be
contacted again.
Last but not least are the safety aspects of the system. With the correct use of
MCBs, RCDs, physical and electrical blocking and adequate documentation, the use
of the system will be made safe.
29
Chapter 4
Powering the Plane
One of the goals of the HIGHWIND project is the development of new control
strategies for AWE. In order to control the plane, actuators for flight control surfaces
are required. These actuators need power in order to be able to work, and there
exist some options on how to get power on the plane. The control of the plane will
be done from the ground station, this means that a way of communication from the
plane to the ground station should exist. The different solutions to the power and
communication problem will be explained in this chapter. First the design of the
plane power electronics will be explained and the different design choices will be
addressed. After that the actual implementation will be discussed. And finally some
possible improvements of the system will be presented.
4.1
4.1.1
Design of the plane power electronics
System requirements
The plane used in the experiments is a Stingray [39]. This is a glider type plane, so
no means of propulsion is present. The plane is equipped with 7 servo-actuators. Six
of them control the different control surfaces. The last one is used for disconnecting
from the tether. The characteristics of the actuators that have been installed are
shown in Table 4.1. The power system has to be able to provide these actuators
with power at all times. Apart from these actuators, some sensors (IMU, GPS, pitot
tube. . . ) and a controller will also be present onboard the plane. These devices need
5 volt DC to function, which adds another demand for the plane power system. Table
4.1 illustrates the system requirements. It is expected that the actuators will not be
requiring maximal power continuously. It is therefore assumed that the actuators
together will not draw more than half of the maximal current at any time. The
total power requirement is thus around 80 W. Since all power electronics have to be
mounted inside the plane, they should be as light, sturdy and small as possible.
30
4.1. Design of the plane power electronics
Table 4.1: System requirements
Actuator aileron 1
Actuator aileron 2
Actuator flap 1
Actuator flap 2
Actuator elevator
Actuator rudder
Actuator tether
PC 104/Lisa & sensors
Total
4.1.2
Voltage (V)
Power (W)
4,8-8,4
4,8-8,4
6-7,4
6-7,4
6-7,4
4,8-8,4
6-7,4
5
4,8-8,4
9
9
18
18
28
14
25
15
75,5
Different designs
Three different power sources are considered:
• With only an onboard battery (design A)
• With a cable connection through the tether (design B)
• With an onboard battery and cable connection through the tether (design C)
These solutions differ in the needed components, the safety of the plane and the time
the plane can fly without landing. In the following sections these different solutions
will be explained and compared in order to select the best solution.
4.1.3
Design A: battery only
General idea
In this design the onboard power is provided by a single battery. This is the standard
solution for radio control (RC) planes. In those planes LiPo batteries are normally
used. They have a large capacity and are capable of delivering considerable power.
Table 4.2 shows the capacity and the power of some LiPo batteries. Since this is the
standard in the RC world, connecting the battery to the servos will not be an issue.
Advantages
The advantage of such a system is the simplicity: all of the power onboard the
plane is supplied from one source (the battery) without the need of transforming
the voltage or frequency. The situation is similar to a normal RC plane so no extra
components have to be installed for the actuators.
31
4.1. Design of the plane power electronics
Disadvantages
The main disadvantage of the battery solution is the limited testing time: a battery
is a finite energy source. After a certain time (depending on the capacity of the
battery) the plane will have to land and the battery will have to be replaced or
recharged. As can be seen in Table 4.2 this flying time is in the order of tens of
minutes. This might be enough for early testing phases but it is far too low for the
eventual goal of generating energy. Of course more (or larger) batteries can be used,
but this will increase the weight considerably and the batteries will still have to be
replaced after a certain time which makes an autonomous system impossible.
Table 4.2: Battery data for powering the plane
Battery
number
Voltage
(V)
Total energy
(Wh)
Discharge
power(W)
Weight
(g)
Flight time at
80 Watt (min)
1 [16]
2 [15]
3 [17]
11,1
11,1
7,4
24,42
6,771
16,28
1098,9
135,42
651,2
201
50,9
119,6
18,315
5,078
12,21
Apart from the limited testing time, there remains a problem with the voltage
onboard the plane. The sensors and the micro-controller need 5 volt DC which is
not a standard voltage of LiPo batteries. Some sort of DC/DC converter has to be
present onboard to supply this 5 volt voltage. There exist a number of solutions for
this:
• Diodes: the required (lower) voltage is created by using the voltage drop over
a diode. A correct diode has to be selected in order to create the required
voltage. This is a fixed voltage drop, the created voltage is only correct if the
input voltage remains the same at all times. This is inefficient because all
excess voltage (and thus power) is transferred to heat in the diode.
• Linear regulator: the required voltage is created by adjusting a voltage divider.
This is an active component, if the input voltage changes between some limits,
the output voltage remains at the required value. This is a more robust solution
than the diodes, but the efficiency remains low: the difference between input
voltage and output voltage is lost in heat.
• Switched-mode: this is truly a DC/DC converter (e.g. buck-boost converter),
the power is transformed from one DC voltage to another. Because of this, the
efficiency is higher than the two previous solutions and this will help reduce the
weight and volume of the power supply. The only problem with this solution is
the production of EMC (electromagnetic compatibility) (due to the switching
of this component) that might interfere with the sensors and micro controller
onboard.
32
4.1. Design of the plane power electronics
4.1.4
Design B: cable connection only
General idea
In this design the onboard power is provided by the carousel: inside the tether there
are two electrical conductors. This allows power to be sent to the plane. Onboard
the plane, this voltage can be used to power all the equipment. The voltage that
will be supplied to the cable can be AC or DC and of any magnitude. AC or DC
both have their advantages and disadvantages as will be discussed below.
Advantages
The main advantage of this system is the unlimited testing time, since the power can
be provided continuously. Furthermore, since there is an electrical connection from
the plane to the carousel, this can double as a communication channel. Without this
physical connection the communication between the plane and the carousel has to
be wireless which might not be as robust.
Disadvantages
If for some reason the electrical connection with the carousel is lost, the plane will
not be powered anymore. This will make the plane uncontrollable and it will most
likely crash and be damaged. The tether/conductor is the single point of failure
of the system; if this fails the plane will fail too. From a safety point of view this
system might also be somewhat dangerous: if the isolation of the conductor breaks
down (might be from the constant reeling out and reeling in) some part of the tether
becomes ‘on voltage’. This might create a short-circuit if the tether falls on the
ground or a person who touches the tether might get an electric shock. Sufficient
safety measures have to be installed on the carousel to make sure these dangerous
situations will not occur. For instance, installing a miniature circuit breaker (MCB)
will eliminate all short circuits and installing a residual current device (RCD) will
protect people against electric shocks.
Decision on the voltage
Including two electrical conductors inside the tether will increase the weight of this
tether. Smaller conductors will result in a lower added weight to the tether. But a
smaller conductor means a higher electrical resistance, which means higher losses in
the conductor. A solution for this problem is the usage of higher voltages.
The usage of a higher voltage will decrease the current (Pload = Uload × I) and
this will decrease the power loss in the cable (Ploss = Rcable × I 2 ). Because of this
simple electrical reasoning a ‘high’ voltage will be selected. Figure 4.1 shows a
simple example: Pload is equal to 80 W, the resistance of the conductor is 42 Ω. The
input voltage is varied and the power loss due to the conductors is calculated. From
this figure it can be seen that there exists a lower limit for the input voltage: if
the input voltage is below 116 V, the demanded power cannot be delivered. The
figure also shows that increasing the input voltage over 116 V will decrease the losses
33
4.1. Design of the plane power electronics
80
Transmission power loss [W]
70
60
50
40
30
20
10
0
0
50
100
150
200
250
Input voltage (V)
300
350
400
Figure 4.1: Transmission power loss for a system which needs 80 W and is connected
with a 42 Ω cable. The red vertical line indicates the required minimal voltage for
this case.
considerably, but increasing the input voltage over 250 V does not provide a large
gain in efficiency. The ideal input voltage for this system will be located between
116 and 250 V.
DC has the advantage that only the magnitude of the voltage will have to be
changed on the plane in order to provide power to the equipment. While AC still has
to be rectified and the plane thus needs an extra component. It is however harder to
find a high voltage (200 V conductor or more) step down DC/DC converter than a
step down AC/DC converter with the same characteristics (200 V or more input).
Aside from this availability issue there is another benefit of using AC: if the standard
AC voltage (230V) is used, power line communication (PLC) can be used as a means
of communicating with the plane. This leads to the choice of 230 V AC as the voltage
that will be provided to the plane via the conductors inside the tether. The different
levels of DC voltage needed on the plane can be solved in the same way as with
design A: diodes, linear regulator or switched-mode.
4.1.5
Design C: battery and cable connection
General idea
The combination of a battery and a cable connection offers the benefits of the previous
designs and most of the problems are solved. The cable connection will be used as
the main provider of the power. As with design B a higher AC voltage is preferred
(lower transmission losses and communication). If for some reason the electrical
connection with the carousel is lost, the battery will be able to provide the required
power. The battery serves in this design as a back-up, it will be responsible for a
safe landing of the plane. The limited time that batteries can provide power is of
little concern, since the battery will only have to provide power during the landing
of the plane, which will take less than a minute. This design is then basically an
interruptible power supply (UPS) for the plane.
34
4.2. Implementation
Advantages and disadvantages
The advantages of this system are a combination of the design A and B: the cable
connection allows a very long testing time and the presence of the battery ensures a
safe landing if the main power connection is lost. The disadvantages of this design
are the safety issues with a cable connection and the increased complexity (which
also adds weight to the plane).
4.1.6
Comparison and decision
The different designs have their advantages and disadvantages. They differ in the
needed components, the possible testing time without landing and the reliability
of the design. These differences can be seen in Table 4.3. Possible scores are
+ + / + / − / − −.
Table 4.3: Comparison of the different designs
Simplicity of the design
Testing time
Reliability
Design A
Design B
Design C
++
−
+
−
++
−
−−
++
++
This table clearly shows that design C has the best characteristics. It scores well
in the aspects that are important for testing the plane: long testing time and high
reliability of the plane. For this reason design C (cable and battery) is selected.
4.2
Implementation
Design C can now be implemented in actual electronics. The selected power electronics
should follow the system requirements as stated before. Figure 4.2 shows the electrical
circuit. It consists of an AC/DC converter (Top 100-112), a DC/DC converter (OPEN
UPS) and a battery. The AC/DC converter is connected to the grid by a cable (two
conductors) inside the tether. Two PLC devices are connected to this cable. These
devices are responsible for the communication between the carousel and the plane.
AC
230 Volt
PLC
DC
12 Volt
Cable
PLC
Top 100-112
OPEN UPS
Actuators
Battery
Figure 4.2: Plane power circuit
35
4.2. Implementation
4.2.1
Components
AC/DC converter
The Tracopower Top 100-112 is the selected AC/DC converter (see Table 4.4 for its
properties). It rectifies the incoming AC voltage to 12 volt DC and is capable of
providing 100 Watt. This component does produce some EMC that might interfere
with some circuits onboard the plane. For this reason a casing is bought, which
should reduce EMC and improves the robustness of the component. Figure 4.3a
shows the component without casing, Figure 4.3b with the casing. It was selected
over other AC/DC converters because of its small size and low weight.
Table 4.4: Properties of Top 100-112 [36]
AC input
voltage (V)
DC output
voltage (V)
Output
current (A)
Efficiency
(%)
Weight
(g)
187-264
12-13
8,3
90-92
140
(a) without case
(b) with case
Figure 4.3: AC/DC converter top 100-112
36
4.2. Implementation
DC/DC converter
The DC/DC converter is an OPEN UPS board (Figure 4.4). This board allows
DC/DC conversion as well as UPS behavior: a battery can be connected to this
board and if the main supply fails the battery will serve as the power supply for the
actuators and other components. The battery is charged if the board is reconnected
to the main power supply. The board can be connected with a mini USB connection
to a PC and the following settings can be changed:
• The output voltage
• The input voltage at which the battery should start working
• The input voltage at which the input voltage should be used as the main supply
• The battery specifications: type, number of cells, over- and undervoltage
limits. . .
All these settings allow the behavior of the board to be optimized for our project.
The properties of the board are listed in Table 4.5. This board is usually used as a
UPS system for PCs, where it is connected to the motherboard and is capable of
sending signals to the PC that the main supply has failed and that the PC should
initiate a safe shutdown.
Table 4.5: Properties of the OPEN UPS board [22]
Input voltage (V)
6-34
Output voltage (V)
Peak output current (A)
6-24
10
Li-ion, LiPo,
LiFePO4, Lead Acid
Supported batteries
Figure 4.4: OPEN UPS board
37
4.2. Implementation
Cable
The two electrical conductors are surrounded by a braided dyneema sleeve [10] that
carries the mechanical load and protects the conductors. The datasheet for the
conductors can be found in [7]. The electrical resistance of the conductors is not
negligible and a certain amount of power will be dissipated in the tether which might
lead to overheating of the tether. The advised long duration temperature limit of
the tether is equal to 70◦ C [10]. Some tests were done to verify this limit is not
exceeded (section 4.3).
Communication
Taking the electrical resistance of the conductors into account (and the resulting
voltage drop), the PLC devices should be able to function at a voltage of 200 V. This
can be guaranteed by using devices that can be used on the US and European grid,
since the voltage is only 110 V in the US. This assumption was verified by testing
(section 4.3).
Configuration
Figure 4.5 shows the configuration of power system components of the plane. The
cable and tether are not included on the figure.
• A: Grid connection (connects to the conductors in the tether)
• B: AC/DC converter (top 100-112)
• C: OPEN UPS board
• D: USB cable that allows programming of the open-ups board
• E: Battery that is connected to the OPEN UPS board
• F: DC output
B
D
C
F
A
E
Figure 4.5: Configuration of all components
38
4.3. Testing
4.3
Testing
In order to verify the assumptions and to ensure everything would work as intended,
some tests were done.
Verifying cable resistance
The two electrical conductors inside the tether have a conductive area of 0, 079 mm2 .
The conductors’ electrical resistance was measured by connecting a load to it: a
200 W lamp was used and the input voltage was gradually increased to the nominal
voltage, see Figure 4.6. The measured resistance of the cable was equal to 42 Ω.
This value is consistent with the datasheets of the conductors [7] (the cable length is
roughly 200 meter).
50
45
Resistance of cable (Ohm)
40
35
30
25
20
15
10
5
0
100
120
140
160
180
Input voltage (V)
200
220
240
Figure 4.6: Resistance measurement cable
Verifying temperature limits
The electrical resistance of the conductors is not negligible and a certain amount of
power will be dissipated in the tether which might lead to overheating of the tether
(the advised long duration temperature limit is equal to 70◦ C [10]). Two experiments
were done to ensure this temperature limit is not exceeded.
In the first test the tether is rolled up on a piece of cardboard and the temperature
is measured with a 200 W light bulb connected to the conductors. Figure 4.7 shows
the results for this experiment, as can be seen the temperature rises very quickly
and comes close to the operating limit of the tether. The test had to be aborted at
11,5 minutes to avoid damaging the tether.
In a second test the tether is rolled up on the aluminum winch and the temperature
is measured with a 200 W light bulb connected to the conductors. Figure 4.8 shows
the results of this test: the temperature rises very slowly.
39
4.3. Testing
The conclusion of these two experiments is that during normal operation of the
carousel (tether is rolled up on the winch with no multi layering of the tether) no
dangerous temperatures of the tether are likely to occur and the electrical conductors
are correctly dimensioned.
60
Temperature (°C)
50
40
30
20
10
0
0
5
10
Time (min)
15
20
Figure 4.7: Temperature measurement cable on cardboard with 200 W load and
230 V input. The load is switched off at t = 11,5 min.
30
Temperature (°C)
25
20
15
10
5
0
0
2
4
6
8
10
Time (min)
Figure 4.8: Temperature measurement cable on aluminum with 200 W load and
230 V input.
40
4.4. Possible improvements
Communication via PLC
In order to assure the PLC devices will work while the cable is loaded and a voltage
drop is present, this situation was tested. Two PLC devices 1 were connected to the
cable while a 200 W light bulb was connected to one side of the cable and the 230 V
grid to the other side. No problems occurred and data transfer speeds were normal.
System test
Finally also the top 100-112, OPEN UPS, battery and some servos were combined
to test their operation. Following situations were recreated:
• Fully charged battery and grid connection while servos are being used
• Fully charged battery and sudden grid failure while servos are being used
• Reconnecting the grid to initiate battery charging
• Battery charging and servo loading while connected to the grid
Everything worked as intended.
4.4
Possible improvements
A number of improvements are possible concerning the plane’s power supply. The
two most promising improvements will be discussed in this section: a redundant
power supply and onboard generation.
4.4.1
Redundancy of the power supply
As explained in the requirements, the plane has to power seven actuators, some
sensors and a micro controller. In the current design a problem on the DC bus, to
which the actuators are connected, will result in a failure of all the actuators. If
the actuators are supplied from different DC buses, a problem on one DC bus does
not affect the other buses and the plane will still be controllable (be it in a reduced
operating mode). This design can be further upgraded if a switchboard is present on
the plane: that way it is possible to switch actuators from a damaged DC bus to a
working DC bus and the plane remains fully operational.
Possible failure of the system
Several situations will result in a failure of the power supply system. This will result
in a plane that is not controllable and this will, in all likelihood, destroy the plane.
Some situations that may cause failure of the power supply: malfunctioning of an
OPEN UPS board, a short circuit in one of the actuators and a short circuit on the
DC bus. Making the power supply fault tolerant will reduce the severity of these
situations.
1
Devolo dLan
41
4.4. Possible improvements
Solution
Multiple designs with different levels of redundancy are considered:
• Single DC/DC converter (Design 1: the original system)
• Separate DC buses (Design 2)
• Secure DC bus (Design 3)
• Full switchboard (Design 4)
These different solutions will be explained in the following sections. The reliability of
these improvements will be compared to the reliability of the system that is installed
on the plane. Detailed calculations of the reliabilities can be found in Appendix D.
Design 1: the original system
The reliability of the original power system is equal to the reliability of the OPEN
UPS board: if the OPEN UPS board fails, the plane fails. Using the OPEN UPS
board already includes one layer of redundancy, as the grid connection or the battery
can fail. As this is the base case, this is not included in the following calculations.
Unfortunately the producers of the OPEN UPS board have not included a mean
time to failure (MTTF) in the datasheet, so exact calculations are not possible. For
this reason all the figures will be expressed dimensionless (in time/MTTF). The
reliability of the system can be calculated and is shown in Figure 4.9.
1
Reliability of the original system
0.9
0.8
Reliability
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
8
time (hours) /MTTF
10
12
Figure 4.9: Reliability of the original system
42
4.4. Possible improvements
Design 2: separate DC buses
A number of ‘groups’ are created that will be powered independently from each other
by use of another OPEN UPS board. This will ensure that a fault on one ‘group’
will not affect the functioning of the other ‘group’. A possibility for the ‘groups’ is to
divide the actuators into 2 groups, each group will be able to control the plane (e.g.
group one = rudder. . . , group 2 = ailerons. . . ). This design is shown in Figure 4.10.
The comparison between this design and the original design (design 1) can be
done in two ways:
• Comparison with the plane in complete operation: all the ‘groups’ are functional
which implies that all the OPEN UPS boards are working. The reliability
is equal to the product of the reliabilities of the OPEN UPS boards. By
consequence the reliability of the total system will be lower than that of the
original system.
• Comparison with the plane in diminished operation: some ‘groups’ are not
functional anymore but the plane remains controllable, be it in a diminished
way, as long as one OPEN UPS board is functional. The reliability of the plane
will be higher than that of the original system since either of the OPEN UPS
boards can fail.
Figure 4.11 illustrates this.
DC
OPEN UPS
Group 1
Battery
AC
Top 100-112
OPEN UPS
Group 2
Battery
Figure 4.10: Separate DC bus
43
4.4. Possible improvements
1
Reliability of the original system
Reliability of the separate dc bus system − complete operation
Reliability of the separate dc bus system − diminished operation
0.9
0.8
Reliability
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
time (hours) /MTTF
8
10
12
Figure 4.11: Reliability of separate DC bus. Two ‘groups’ and thus two OPEN
UPS boards are used to calculate this.
44
4.4. Possible improvements
Design 3: secure DC bus
The actuators are connected to same DC bus and this DC bus can be fed by two (or
more) OPEN UPS boards. These OPEN UPS boards will not work at the same time.
If the board that is connected to the DC bus fails, the ‘Power switch’ will switch the
DC bus to another (functioning) OPEN UPS board. By doing this the DC bus is
‘secured’ against failures of the OPEN UPS board. Figure 4.12 shows the design of
such a system and Figure 4.13 shows an example of a power switch.
The reliability of the secured DC bus system is the same as the reliability of the
diminished operation of the separate DC bus: only one of the OPEN UPS boards
has to work in order to have a functional plane. The difference with the separate DC
bus in diminished operation is that in the secured DC bus system all functionality
is still available on the plane. However the switchboard is a single point of failure
and intelligence is required to operate this. Figure 4.14 illustrates the difference in
reliability between this design and the original design.
DC
OPEN UPS
Actuators 1
Battery
AC
Power
Switch
Top 100-112
OPEN UPS
Actuators 2
Battery
Figure 4.12: Secured DC bus
45
4.4. Possible improvements
Figure 4.13: Power switch of the secured DC bus
1
Reliability of the original system
Reliability of the secured bus system
0.9
0.8
Reliability
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
8
time (hours) /MTTF
10
12
Figure 4.14: Reliability of the secured DC bus - calculated for two OPEN UPS
boards
46
4.4. Possible improvements
Design 4: full switchboard
In this design the actuators are divided into groups as in the separate dc bus design.
The difference with the separate DC bus design is the presence of a switchboard
between the OPEN UPS boards and the groups. If an OPEN UPS board fails, the
switchboard will act and will switch the failed OPEN UPS board and switch to the
working OPEN UPS board. Figure 4.15 shows a design of this system and Figure
4.16 shows an example of the switchboard.
The reliability of the full switchboard system is equal to that of the secured DC
bus system: the plane is functional if one of the OPEN UPS boards is working.
The difference between the two designs is the difference in power rating: in the
secured DC bus, the power is limited to the power of an OPEN UPS board. In
the full switchboard this is only true if all but one of the OPEN UPS boards have
failed. Otherwise each ‘group’ will have the power of one OPEN UPS board available.
Furthermore a short-circuit on the DC bus or in one of the actuators will not evolve
in a full system failure. Figure 4.17 illustrates the reliability of a two OPEN UPS
boards full switchboard system. The switchboard is now a single point of failure and
intelligence is required to operate this.
DC
OPEN UPS
Actuators 1
Battery
AC
SwitchBoard
Top 100-112
OPEN UPS
Actuators 2
Battery
Figure 4.15: Switched DC bus
Summary table
Table 4.6 summarizes the consequences for the two most likely faults: an OPEN
UPS failure or a short circuit in one of the actuators.
Table 4.6: Summary table, comparing the effect of faults for the different designs
Fault
Design 1
Design 2
Design 3
Design 4
Single OPEN UPS fails
crash
diminished operation
OK
OK
Actuator fails and shorts
crash
diminished operation
crash
diminished operation
47
4.4. Possible improvements
Figure 4.16: Switchboard of the switched DC bus
1
Reliability of the original system
Reliability of the switchboard system
0.9
0.8
Reliability
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
8
time (hours) /MTTF
10
12
Figure 4.17: Reliability of the full switchboard system
48
4.5. Conclusion
4.4.2
Onboard power generation
At this moment the plane is being powered from the ground: its main power supply
is a grid connection. If the plane could generate its own power, the conductors inside
the tether could be left out and the plane would be independent of the carousel for
its power. In this section we will suggest some possible power systems and address
their viability.
Propeller
A possibility is to use a ‘propeller’ connected to a simple DC motor. The speed of
the plane would make the propeller rotate and this will generate a DC voltage. This
will be a very fluctuating DC voltage and matching the power consumption with the
power generation will be challenging. It can be partly solved by using the OPEN
UPS board: it can handle a range of input voltages and it has the capacity to buffer
energy in its battery. This buffering of energy is essential for onboard generation:
during start-up, the plane will be moving slowly and it will not be able to generate
sufficient power for its actuators. This will make the plane uncontrollable and it will
be hard to launch it without control capabilities.
PV
Another possibility is using photovoltaic panels (PV): the plane could carry some PV
panels that can generate power. This option will not allow to use the plane at night
or in situations with low light. Apart from that, the weight will also be considerable.
Regular PV panels that are installed on rooftops have a power to weight ratio of
9,25 W/kg and a power to surface ratio of 128,5 W/m2 [35]. For a power demand of
80 W this would translate to an additional weight of 8,6 kg and a required surface of
0,62 m2 . From these numbers it is clear that PV as a means of onboard power is not
a good solution.
4.5
Conclusion
The system requirements for the plane power system have been met. The unique
requirements of the tethered aircraft required some creative repurposing of off-theshelf products intended for other uses (home networking, PC power backup. . . ). A
robust and reliable system has been designed and tested that will enable the project
to use the plane in long duration tests and that minimizes the risk of damaging
the plane in case of a power cut of the main power supply while also enabling
reliable communication. This is achieved by using a combination of power line
communication devices, an AC/DC converter and an OPEN UPS board with a
LiPo battery. Other configurations of the power supply are suggested that can
further increase the reliability or make the plane’s power supply independent from
the carousel.
49
Chapter 5
The Final System
When combining the designs from Chapter 3 and 4 the final system can be configured.
In this chapter important components from that system and their interactions are
discussed. The Siemens drive system is discussed first in two parts. Then the plane
and auxiliaries are integrated to form the final system. After that the communication
with the drives is discussed and finally an important fault during testing is covered.
5.1
The drives
Figure 3.2 already showed an overview of the proposed Siemens drive system. The
final implementation of the drives is schematically shown in Figure 5.1. This
implementation can then be split up into two main parts and other components.
The first part is the AC/DC conversion of the three phase voltage and the second
part can be identified as going from the DC bus to the actual rotation. The detailed
information of all the components can be found in the Sinamics S120 Booksize Power
Unit Manual [28]. Most of the information in this section is derived from this manual.
The detailed list of components and their order codes can be found in Appendix A,
the order codes will be shown in footnotes.
5.1.1
AC to DC
The rectification of the three phase grid to the DC bus happens in the Active Line
Module 1 . This generates a constant, regulated DC voltage. It begins precharging
the moment the grid is connected and only starts regulating to 600 V once (one of)
the drives are (is) enabled. Only when the capacitors are charged and the voltage is
regulated, the drives can start operating.
An active line module was selected over a basic line module and a smart line
module because of its feedback capabilities (not present on the basic line module)
and its regulation capabilities (not present on the smart line module). Feedback
(making use of the active front end) is required to send excess power back to the grid
and to be able to generate electricity once the system is fully operational. It allowed
1
order code 6SL3130-7TE21-6AA3
50
5.1. The drives
AC / DC
converter
Control
Unit
Drive Electronics
Resistor
Active
Line
Module
Braking
Module
Active
Interface
Module
Basic Line
Filter
Drives
Sensor
Module
2
Motor
Module 2
Motor
Module 1
Sensor
Module
1
Brake
cable
M
M
Carousel Motor
Winch Motor
High power connection (400V AC or 600V DC)
Low power connection (24V DC)
DRIVE-CLiQ cable
Encoder/resolver cable
Figure 5.1: Schematic overview of the drives
us to test the generating efficiency of the system, of which the importance is shown
in Chapter 6 and also adds to the safety and the flexibility of testing.
The difference between a smart line module and an active line module is the level
of regulation of the DC bus voltage. While the smart line module is also capable of
sending power back to the grid, it does not actively control the DC bus. This means
that the voltage will show the typical current and voltage waveforms of a 6-pulse
diode rectifier bridge. The original idea was that some additional components might
be connected to the DC bus. Especially batteries (when directly connected) would
suffer under a pulsating voltage. Despite a small drop in efficiency, an active line
module was thus selected.
Because power can now be sent back to the grid, additional components are
required. The first component is an Active Interface Module 2 . This contains line
reactors and low-frequency/switching frequency filters. The second component is a
Basic Line Filter 3 , which is mainly effective in the frequency range from 150 kHz
to 30 MHz. Both these filters assure limited pollution of the grid voltage and the
correct level of electromagnetic compatibility (EMC) as set by EN 61800-3.
5.1.2
DC to rotation
On this DC bus we can now connect the motor modules, to which we can connect
the motors.
2
3
order code 6SL3100-0BE21-6AB0
order code 6SL3000-0BE21-6DA0
51
5.1. The drives
The Winch Motor 4 was selected based on the requirements stated in Section 2.1
and was selected over other motors based on its weight, size, efficiency and cooling.
In Section 3.2 it was already mentioned that the motor is an 8.2 kW Simotics PMSM
which weighs 51,6 kg (with brake and gearbox) and has a 91 % efficiency at full load
(with gearbox) [31]. The full datasheet is available in Appendix B.2. Another reason
for choosing this drive, which was also stated in the system requirements, is cooling.
This servo motor requires no active cooling. Its temperature is limited by the gearbox
housing to 90 ◦ C. This means that heating up due to stationary torque production is
no problem, as it is designed for high temperatures and passive cooling. This motor
is also fitted with a resolver, which is more robust with respect to noise due to the
slip ring connection.
The winch motor is fed by Motor Module 1 5 as this is the motor module that
belongs to this motor. It is over dimensioned (45 A nominal current of the motor
module versus 18 A nominal current of the motor) because the winch motor is capable
of tremendous overloading. When accelerating the current can go up as high as 85 A.
The Carousel Motor 6 was also selected based on the requirements stated in
Section 2.1. The possibilities with Siemens’s induction motors are so vast that this
motor was tailored. In Section 3.2 it was already mentioned that the carousel motor is
a 4 kW 4-pole IM which weighs 52 kg (with gearbox) and has an 86,60 % efficiency at
full load (with gearbox). Included are an encoder and a gearbox. The full datasheet
is available in Appendix B.1. The motor is cooled by a fan mounted to the internal
shaft (thus spinning at 1500 rpm nominal). This is a simple and robust solution, but
it doesn’t allow the motor to be cooled when stationary. Since the motor will not
deliver torque while stationary, this is not considered a problem.
The carousel motor is fed by a 9 A motor module (Motor Module 2 7 ) as this is
the motor module that belongs to this motor.
5.1.3
Other components
The Control Unit 8 is the drives’ brain. Almost all components are connected to this
unit via Siemens’s proprietary DRIVE-CLiQ cables (thick dotted lines in Figure 5.1).
The control unit can be connected to a computer via a LAN port on the front.
This connection is used for programming the drives. Each component connected
via DRIVE-CLiQ transmits an electronic name plate, such that everything can be
programmed on the control unit itself. There is also a communication port (in this
case PROFINET (PN)) and some digital inputs and outputs for attaching extra
components (e.g. a switch). The full hardware manual of the Control Unit is available
in [26].
order code 1FK7105-2AF71-1SH0, gearbox order code LP120S-MF1-3-1K1/1FK7105-5AC71
order code 6SL3120-1TE24-5AA3
6
order code 2KJ1103-1GJ12-1FL1-ZD88+H03+K01+K06+L02+L50+M00+M71+N48+Q47+Q95
7
order code 6SL3120-1TE21-0AA3
8
order code 6SL3040-1MA01-0AA0
4
5
52
5.2. Assembly
Because the motors have no DRIVE-CLiQ interface, they are connected via a
sensor module. Sensor module 1 9 is an SMC10 module which connects the winch
motor’s resolver and temperature sensors to the control unit. Sensor module 2 10
is an SMC30 module which connects the induction motor’s encoder to the control
unit. The motors have no DRIVE-CLiQ interface because the current version of
DRIVE-CLiQ is not able to go through slip rings.
Connected to the DC bus is also a braking module 11 to which a braking resistor 12
is attached. This component is not connected to the control unit via DRIVE-CLiQ
since it requires no control inputs13 . The braking module enables a controlled shut
down of the drives if a power failure occurs and also limits the DC link voltage to
770V.
The final block in the scheme is the AC/DC converter 14 . This component is used
to supply power to all electronic components. The 24 V DC power line is shown as
the narrow full line in Figure 5.1. All components (but the motors) require this power
line since all the electronic components are electrically separated from the main
connection and the DC bus. This is an expensive but useful feature that companies
like ABB and WEG do not offer. Should something go wrong on the main line (e.g.
an overvoltage), then that fault is not transmitted to the electronics. This means
they can continue operating and safely shut down operations. As will be explained
in 5.5 this saved a lot of trouble.
5.2
Assembly
5.2.1
Hardware
All the components need to be wired as shown in Figure 5.1. It is important that
the components which are connected to the DC bus are in a specific order. Following
the power flow, the order is: active line module, winch motor module (motor module
1), carousel motor module (motor module 2), braking module. This is based on
the amount of current drawn by each component. The active line module is the
current source, the winch motor module is able to draw the most current, so then
this doesn’t need to pass through the DC bus of the carousel motor module.
Another important aspect when mounting the drives is earthing and equipotential
bounding. Each component has multiple earthing connections and at least one of
those should be connected. This set-up is connected via an equipotential back plate
which is connected to the ground. Components which are not directly mounted to
this back plate (for example the sensor modules are mounted on a DIN rail) need to
be wired to the earth.
order code: 6SL3055-0AA00-5AA3
order code: 6SL3055-0AA00-5CA2
11
order code: 6SL3100-1AE31-0AB0
12
order code: 6SN1113-1AA00-0DA0
13
It has hard wired connections to the control unit for monitoring, so that if a fault should occur,
the control unit is aware of this event.
14
order code: 6EP1334-3BA00
9
10
53
5.2. Assembly
A final important aspect is cooling. [28] has a list of the estimated power loss of
each component. This adds up to 918,4 W (full details in Table 6.2). The components
with significant losses have an internal fan. In this case the drives are mounted
in a cabinet, so a distance of 100 mm above and below the components should be
maintained and ventilation inside the cabinets is required. Therefore a fan for the
cabinets with temperature monitoring was bought.
5.2.2
Software
The drives were configured using Siemens’s Drive ES - STARTER software package
(v4.3.1.2). A list of all the functions and possibilities is available in [29] and an
explanation of all the parameters and faults that can occur is available in [30].
Explaining the full software configuration would lead us to far, however the choice
between the different control loops will be explained.
Siemens’s software offers three control possibilities for motors: servo, vector
and U/f control (voltage over frequency control). Each control loop will be briefly
explained and it will be made clear why servo control was selected for both our
motors. Most of the information comes from [29].
The naming of these control loops is very confusing, since generally ‘vector control’
means that the internal PI controller for the motor current controls the direct and
quadrature current, which are calculated via a Park-Clark transformation. This is
the case for both Siemens’s ‘Servo control’ and ‘Vector control’ and their naming
thus points at the way the speed and torque control loop work.
Servo control
The servo control loop enables operation with a high dynamic response and precision
for a motor with a motor encoder or resolver. It was specifically designed for motors
using speed control and it has a sampling time of 150µs15 . It also offers a great deal
of pre-control and various number of possibilities to limit the rotational speed and
torque. Therefore it was recommended by Siemens to use this control loop for both
our drives.
Vector control
The vector control loop is mainly aimed for sensorless torque control. When no
sensor is present and the system is thus open loop, the position of the flux and actual
speed must be determined using the electric motor model. At low frequency, the
motor model cannot determine the speed with sufficient accuracy. To circumvent
this and to operate more exactly, a closed loop system with sensor is better. With
a sensor the flux and speed estimation is no longer necessary. The control loop is
however still limited to a sampling time of 1000µs and therefore slower than the
servo control loop.
15
The sampling time specifies how often the controller samples the measured process variable
and computes and transmits a new controller output signal
54
5.3. The switchboard
U/f control
The U/f control characteristic is the simplest way to control an induction motor. The
stator voltage of the induction motor is set proportional to the stator frequency. This
technique is used for many standard applications where the dynamic performance
requirements are low. It requires no feedback but is also not very accurate when
dealing with changes in torque. Therefore servo control was also selected for the
carousel motor (which is an induction motor).
5.3
The switchboard
Because the drive system, shown in Figure 5.1, and all the other components need to
be connected to the grid, a switchboard is required. On this switchboard electrical
safety equipment like MCBs and RCDs can be connected. In the following subsections
the electrical and safety requirements of the different components will be briefly
recapitulated so that a design for the switchboard can be made. The safety design
tries to take into account the regulations described in the AREI [1]16 . It was also
approved by the HSE department of the KU Leuven.
5.3.1
AREI
The AREI [1] has a few clauses that are of interest to this project. First of all it should
be made clear that in all probability the set-up falls under ‘electrical laboratory
and test stands’ described in art. 55. Art. 41 therefore describes that, given a few
conditions 17 , the set-up is not by law obliged to be protected against electrical
shocks. Nevertheless shocks should never occur and the AREI is being followed as a
guide line.
Besides proper isolation of all current carrying conductors, physical protection of
all components and proper signaling, the AREI also describes some rules on how to
protect with MCBs and RCDs. Art. 86.07 states that all current carriers should be
protected with an RCD with a maximum sensitivity of 300 mA. Art. 119 states that
all current carriers should be protected against over current in the approved manner.
It was therefore decided to protect the entire system with a 300 mA RCD and each
subsystem with a suitable MCB, to protect for over current.
AREI stands for “Algemeen reglement op de elektrische installaties”, which is Dutch for ‘general
regulation for electrical installations’
17
a simplification of these conditions is:
• A 1m high demarcation
• Only people who need to be there are allowed
• Clear signs of the hazards
• Touching voltages higher than 500 V AC or 750 V DC could not be done without intentionally
trying
• Should protecting direct touching be impossible, the people themselves have to be properly
protected
16
55
5.3. The switchboard
5.3.2
The drives
As shown in Figure 5.1 the drives require two power connections: a three phase 400 V
main connection with a nominal current draw of 23 A (this is the nominal current of
the active line module) and a single phase 230 V connection with a nominal current
draw of around 0,5 A18 . The drive has some filters which come with a warning ‘The
drive components generate high leakage currents in the protective conductor’. It is
thus important to select the 300 mA RCD so that it will not trip during nominal
operation (as also brought up by Art. 85.05 AREI which states that an RCD should
never interrupt the power supply during nominal and expected operation). Therefore
the main RCD should be a type B, as set by [28].
To protect the 400 V supply a 32 A MCB is selected, because it can cope with
the nominal and peak power of the drives and should still be able to protect it in
case of a fault. It should also prevent the main power cable (32 A nominal) from
overheating and braking down. For the 230 V electronic power supply a 2 A MCB
is selected, because it is be able to cope with the nominal current draw while still
being able to clear a fault.
5.3.3
The plane
As shown in Section 4.2 the electrical design for the plane is as in Figure 4.2 or as in
Figure 5.2. The plane needs about 80 W at 230 V and also needs to be able to charge
the battery while delivering that power. Therefore an MCB of 2 A is sufficient while
the threshold is low enough for a fault to be detected and cleared. The maximal long
term current for the two wires inside the tether is 3 A, so should a fault occur then
this is not able to destroy the electrical wires and thus the tether. [7]
Servos
AC
PLC
Cable
OpenUPS
PLC
DC
Plane
Electronics
Battery
Figure 5.2: Schematic overview of the plane, reworked version of 4.2
18
Our own measurement results in 0,4 A. When calculating using the electronic power consumption,
provided by [28], the 230 V current consumption results in maximum 0,74 A and nominal 0,53 A.
56
5.3. The switchboard
Since the plane might crash or land on wet ground and be touched by humans
when the electrical power connection is still operational, an additional 30 mA RCD is
added to this circuit. 30 mA is the legal threshold for ‘safe’ and should thus prevent
anybody from being harmed by the electrical connection on the plane. Should the
plane be detached from the cable and the cable falls on the ground and creates a
connection with it, then the RCD will also switch off the voltage in this case.
5.3.4
The auxiliaries
The auxiliary power demands include multiple computers and laptops for control and
monitoring, lighting for the cabinets, ventilation for the cabinets, sensors which need
external power . . . They all connect on 230 V and it is estimated that the combined
power draw is 1 kW19 . A 10 A MCB is chosen so that enough gear can be connected
while a fault should still be detected and cleared.
5.3.5
The switchboard
The switchboard, schematically represented in Figure 5.3, connects all previously
discussed components to the three phase 400 V grid connection (with neutral and
earthing (protective earth or PE) wire, the PE is not shown on the scheme). An
additional manual switch is added at the grid side and an additional relay is added
to the drives’ main power supply, to be able to electronically switch this on and off.
Because a three phase connection is available, the power connections at 230 V can
be used to more or less balance the phases by connecting different parts to different
phases. On the scheme the auxiliaries are connected to phase 1, the plane to phase
2 and the drive electronics to phase 3. Figure 5.4 shows all the parts connected
together. This scheme represents the practical implementation.
Drive
Electronics
Drives
32A
MCB
Relay
2A
MCB
Plane
Three
phase grid
+ neutral
Auxiliaries
2A
MCB
10A
MCB
Manual
Switch
30mA
RCD
300mA
RCD
L1
L2
L3
N
Figure 5.3: Schematic overview of the switchboard
19
5 laptops (90 W), 1 PC (200 W), 3 fans (70 W), 10 sensors (10 W) and 3 lights (30 W)
57
Sensor
Module
2
Braking
Module
...
230V Socket
230V Socket
230V Socket
Auxiliaries
Resistor
Drives
M
Winch Motor
Carousel Motor
Brake
Motor
Module 1
M
Motor
Module 2
Control
Unit
Sensor
Module
1
Active
Line
Module
Basic Line
Filter
2A
MCB
30mA
RCD
2A
MCB
PLC
Cable
Figure 5.4: Schematic overview of the final system
Relay
32A
MCB
Switchboard
Active
Interface
Module
AC / DC
converter
Plane
PLC
10A
MCB
DC
AC
Battery
OpenUPS
300mA
RCD
Manual
Switch
Three
phase grid
+ neutral
Plane
Electronics
Servos
5.3. The switchboard
58
5.4. Communication
5.4
Communication
Communication between the drives and the PC running the control software is
crucial. Multiple possibilities exist, which all use the PROFINET (PN) interface
on the control unit. The PC runs on Linux and compatibility with this operating
system is thus required. Three possibilities are then considered:
• using a PLC as a middle man
• using an xml-panel as a middle man
• communicating directly over PN
All three possibilities will be discussed briefly.
PLC
A first solution is to use a PLC (programmable logic controller) as a middle man.
Communication between the drives and the PLC goes over PN. Another communication protocol needs to be implemented between the PLC and the PC. Modbus
TCP/IP, using a standard Ethernet cable, is a suitable communication protocol for
which libraries for Linux exist. The main advantage of a PLC is that part of the
logic can be implemented on this device. The PLC would then e.g. be able to do the
start-up procedure of the drive via a simple ‘start’ command. This means that the
communication part on the PC can be kept very simple.
Another advantage is that sensors and equipment, like relays and switches, can be
connected to this PLC. It would then contain the logic for operating these components
and the PC could read the sensor data via Modbus TCP-IP. The main disadvantage
is the complexity. The cost for a PLC is around €150 but the software needed to
program it costs an additional €850.
Panel with XML
A second solution is to use an interfacing panel as a middle man. Communication
between the drives and the panel goes over PN. For communication with the PC, the
panel serves as an XML-server. The main advantage is that configuring this panel
and the XML-server is easier than configuring the PLC. The panel does not support
extra equipment like relays and sensors, so additional interfacing would be required.
The cost is around €1000 (the same as for the PLC). An interfacing panel can also
be added as a peripheral to the PLC.
Direct communication
A final solution is to connect PN directly to the PC. This would mean writing our
own PN controller, as this is not available, or implementing an OPC server. This
option was considered first, but multiple experts advised against it because it would
take too much time.
59
5.5. Mistakenly tripping of the RCD during testing
Conclusion
Because direct communication is not feasible and using a panel as an XML-server
means finding another way to communicate with sensors and other components, a
PLC will be used. The PLC can also be used to implement safety measures and
provides expansion for the future, as automation can be integrated.
5.5
Mistakenly tripping of the RCD during testing
During testing of the drives, the used RCD was of the wrong type (type A) and sensitive to 30 mA instead of 300 mA. Therefore it mistakenly tripped and disconnected
the drives from the grid, while the winch motor was generating energy. This lead
to an overvoltage on the DC bus, which lead to the failure of some of the DC bus
capacitors inside the 45 A motor module. This motor module needed to be entirely
replaced due to the failed capacitors.
5.5.1
Course of events
Together with Siemens the following course of events was composed; all events
happened in a matter of seconds:
1. The system is working fine and about 1 kW is being generated: the winch motor
is working at a fixed speed and the driving motor is delivering a fixed torque
2. The RCD trips due to the normal operation of the filters
3. This disconnects the drives from the grid
4. Power can no longer be sent back to the grid
5. The winch motor is no longer capable of delivering the required counter torque
6. The driving motor (torque control) starts to speed up due to its torque set-point
and too high speed limit
7. Because the only place to lose energy is in the capacitors of the 600 V DC-bus,
the bus’ voltage starts rising
8. The braking module starts burning excess power due to the DC voltage rising
above 770 V
9. The braking module stops working due to an over-temperature in the braking
resistor and is thus no longer capable of dumping the power
10. The DC-bus voltage further rises over 800 V, which is the nominal voltage of
the capacitors
11. Some DC-bus capacitors of the 45 A motor module explode
12. Due to the explosion the DC-bus shorts, thus releasing all excess energy
13. The emergency button of the driving motor is pressed
14. The motors stop rotating and the system is fully de-energized
60
5.6. Conclusion
5.5.2
Lessons learned
The experienced fault thought some valuable lessons:
• Using the correct RCD is extremely important, while a 30 mA device might
seem safer due to the leakage current being limited to a safe 30 mA, this limit is
too low to allow normal operation of the drives. Furthermore the RCD should
be a type B.
• Loosing the grid connection while generating is a consequence that could result
from multiple causes, therefore this issue should be dealt with properly, even
if the RCD in the final set-up should not trip due to normal operation of the
drives and filters.
• Part of the issue lies also in the driving motor having a torque set-point and a
too high speed limit, thus increasing the speed of the winch motor once it was
disconnected from the grid. In the final set-up this should be impossible, since
the kite will lose traction when the tether is being unrolled faster.
• The drives’ electronic power supply is fully independent of the main power
supply, otherwise the overvoltage on the DC bus would have taken out all the
electronics.
5.5.3
Solution
At the time of writing there is no consensus yet on what is the best solution. Two
solutions are proposed by Siemens:
The fist solution is to use a voltage protection module (VPM). This module
detects an overvoltage (the threshold is 800 V) and shorts the motor’s connectors.
All energy is then transferred to heat in the short-circuit and the motor is no longer
connected to the DC bus and the rest of the system [32].
The second solution is to use brake resistances which are used to short-circuit
the armature when required. These resistances are connected in parallel with the
power cable and the energy is now dissipated in the brake resistances [27]. Correct
dimensioning is thus very important.
5.6
Conclusion
In this chapter all previous components are brought together to form the final system.
The drives, plane and auxiliaries are connected together on a switchboard to be able
to connect to the three phase grid. This final system is protected with MCBs and
RCDs. A first implementation is made to be able to test the drives. The results of
these tests will be discussed in Chapter 6. Furthermore a PLC is introduced to be
able to communicate with the drives from the control PC. Finally the mistakenly
tripping of the RCD during testing is discussed as this is an important fault that
also halted the testing.
61
Chapter 6
Testing the Drives and
Implementation of the Results
The final system has to be tested in a controlled environment in order to check all
the functionalities. This is done by creating a test set-up in the ESAT lab ‘labo
grote machines’. The drives were tested by measuring the efficiencies of a range
of operating points. This way familiarity with the drives was attained and the
efficiency measurements can be used in the optimization of a power orbit. So far
the power orbits were optimized without taking the electrical conversion system
into account. The efficiency measurements enables to asses the accurateness of a
function that transfers the mechanical power to the electrical output power. This
makes the optimization for maximal electrical energy yield of a power orbit possible.
Two different functions will be addressed in this chapter: ‘power loss calculation’
and ‘curve fit’. The most accurate function will be used in the optimization of a
power orbit and the results will be discussed. These results allow an assessment of
the dimensioning of the winch drive.
6.1
Testing of the carousel drive
The electrical power required by the carousel drive will be measured. These measurements will serve as a means to validate the accurateness of the proposed functions
later on. The carousel drive only has to operate in motor mode, therefore only motor
mode was tested.
6.1.1
Measurement set-up
The carousel motor is connected to two brakes: a particle brake that is capable
of providing braking torque at low rotational speed and an eddy current brake
that will not be used in this test since it only functions at rotational speed values
that are higher than the rotational speed of the carousel drive. A torque flange is
installed between the motor and the brakes in order measure (mechanical) torque.
Together with a rotational speed measurement this torque measurement will be used
62
6.2. Testing of the winch drive
to calculate the mechanical power generated by the carousel drive. The electrical
power is measured by connecting a power analyzer to the grid connection of the
drive. See Appendix E.4 for details on the used components. During testing the
temperature was kept between 40±10◦ .
370 operating points were measured: the rotational speed was varied between 10
and 125 rpm and torque was varied between 0 and 340 Nm. These measurements
nearly cover the whole operating field of this drive: the nominal rotational speed is
equal to 100 rpm and the nominal torque is equal to 389 Nm. The braking torque
could not be increased to the nominal torque because the particle brake was not able
to generate more braking torque. This limitation is not of no concern because the
carousel drive is oversized: it will not have to work in the carousel set up at its nominal
torque. Seven different variables (rotational speed, torque, active power, reactive
power, apparent power, power factor and current) were recorded in order to have
some redundancy in the measurements: all the measurement points had to be written
down manually and typing errors can occur. By using redundant measurements,
errors can be corrected afterwards during the analysis of the measurements.
6.1.2
Result
The measurements were used to create an efficiency map of the carousel drive. Figure
6.1 shows the efficiency map that was created by fitting a surface to the measurement
points using the ‘TriScatteredInterp()’ function in MATLAB. This function provides
an easy way to visualize the measurements. The white region in Figure 6.1 below
40 rpm originates from the limited braking torque the particle brake can provide at
low rotational speed. The white region above 100 rpm originates from a limit on the
electrical power: we limited the active power to 4,4 kW.
6.2
Testing of the winch drive
The electrical power required by the winch drive will be measured. These measurements will serve as a means to validate the accurateness of the proposed functions
later on. The winch drive has to work in motor and generator mode, therefore two
test set-ups were used.
6.2.1
Measurement set-up
Motor mode set-up
The same measuring set-up as the one for the carousel drive is used for the testing of
motor mode of the winch drive (see Appendix E.4). Since the rotational speed of this
drive is higher (up to 1500 rpm) the eddy current brake can be used. During testing
the temperature was kept between 70±20◦ . 507 operating points were measured:
the rotational speed was varied between 50 and 1500 rpm and torque was varied
between 0 and 100 Nm. These measurements make up the whole operating field of
this drive: the nominal rotational speed is equal to 1000 rpm and the nominal torque
63
6.2. Testing of the winch drive
350
70
300
60
50
200
40
150
30
100
20
50
0
Efficiency (%)
Torque (Nm)
250
10
0
20
40
60
80
Rotational speed (rpm)
100
120
0
Figure 6.1: Efficiency map of the carousel drive in motor mode
is equal to 78 Nm but the motor can easily be overloaded up to 1500 rpm (limited by
the gearbox input speed) and to 100 Nm1 (limited authoritarian). Seven different
variables (rotational speed, torque, active power, reactive power, apparent power,
power factor and current) were recorded in order to have some redundancy in the
measurements: all the measurement points had to be written down manually and
typing errors can occur. By using redundant measurements, errors can be corrected
afterwards during the analysis of the measurements.
Generator mode set-up
The generator measuring set-up is different from the motor mode measuring set-up
since the brakes cannot be used as a motor to drive the winch drive. Another drive
thus has to be used as a motor, see Appendix E.4 for details. The measurement
set-up has an analogue torque measuring device which allows us to calculate the
incoming mechanical power. The generated power is measured by connecting a power
analyzer to the main power infeed of the drive. During testing the temperature was
kept between 70±20◦ .
The winch motor is able to deliver a peak torque of 132 Nm during a small time duration
(100 ms). Taking the gearbox ratio into account this is equal to a peak torque of 396 Nm on the
outgoing gearbox shaft
1
64
6.2. Testing of the winch drive
552 operating points were measured: the rotational speed was varied between 50
and 1500 rpm and torque was varied in order to test different generating powers from
0 kW to 10 kW (power was limited to 10 kW, in order not to overload the motor too
excessively). These measurements make up the whole operating field of this drive:
the nominal rotational speed is equal to 1000 rpm and the nominal torque is equal to
78 Nm but the motor can easily be overloaded up to 1500 rpm (limited by the gearbox
input speed) and to 100 Nm (limited authoritarian or by the 10 kW limit). Seven
different variables (rotational speed, torque, active power, reactive power, apparent
power, power factor and current) were recorded in order to have some redundancy in
the measurements: all the measurement points had to be written down manually and
typing errors can occur. By using redundant measurements, errors can be corrected
afterwards during the analysis of the measurements.
Holding torque set-up
In carousel 1.0 (a smaller indoors version) a crash occurred due to a too low holding
torque of the installed drive which caused a slip in the tether length. To ensure that
this does not happen in the new carousel, a holding torque test was done to have
confirmation of the data sheet. The generator measuring set-up can also be used for
a holding torque measurement. The driving motor exerts a torque and our winch
drive has a zero speed setpoint. The holding torque measurement was limited to
114 Nm because the driving motor could not create a higher torque at zero speed.
The installed brake was also tested in this set-up and likewise the measured torque
was limited to 114 Nm.
6.2.2
Result
Motor mode results
The measurements were used to create an efficiency map of the winch drive in motor
mode. Figure 6.2a shows the efficiency map that was created by fitting a surface to
the measuring points using the ‘TriScatteredInterp()’ function in MATLAB. This
function provides an easy way to visualize the measurements.
Generator mode results
The measurements were used to create an efficiency map of the winch drive in
generator mode. Figure 6.2b shows the efficiency map that was created by fitting a
surface to the measuring point using the ‘TriScatteredInterp()’ function in MATLAB.
This function provides an easy way to visualize the measurements. An important
detail is that ’negative efficiencies’ are mapped to zero: in generating mode it is
possible that power is required. In that case the generated power is not as large as
the power losses that occur because of the functioning of the components. These
points would distort the figure and are for that reason mapped to zero efficiency.
The white triangle in the upper right corner of the figure is due to the limitation in
generated electrical power: this was limited to 10 kW.
65
6.2. Testing of the winch drive
100
90
80
80
70
60
60
50
50
40
40
Efficiency (%)
Torque (Nm)
70
30
30
20
20
10
10
0
0
500
1000
Rotational speed (rpm)
1500
0
(a) motor mode
90
80
80
70
70
50
50
40
40
30
30
20
20
10
10
0
Efficiency (%)
Torque (Nm)
60
60
0
500
1000
Rotational speed (rpm)
1500
(b) generator mode
Figure 6.2: Efficiency map of the winch drive
66
6.2. Testing of the winch drive
Holding torque result
Table 6.1 shows the measurement results. From the data sheet (Appendix B) a
higher holding torque should be possible but due to limitations of the test set-up
this could not be tested. This result confirms that the winch drive could keep the
tether length fixed when the plane exerts a force of 1146 N on the tether (the winch
drive has a radius of 0,1 m). Higher forces should be possible too when looking at
the data sheet, but have not been confirmed experimentally.
Table 6.1: Holding torque measurement
Torque (Nm)
Active power (W)
Reactive Power (VAr)
114,6
536,1
1804,4
Apparent Power (VA)
Power factor
Current (A)
1882,3
0,284
2,675
67
6.3. Power loss calculation
6.3
Power loss calculation
The first function to translate mechanical power into electrical power is the ‘power
loss calculation’. This function will use the power losses in the drive to estimate the
required or generated electrical power. As mentioned in Appendix B the servo motor
of the winch drive has a maximum efficiency of 91,2 % (including the efficiency of the
gearbox) and the induction motor of the carousel drive has a maximum efficiency of
86,6% (including the efficiency of the gearbox). When a drive system is considered,
the efficiency of this system will be lower than the efficiency of the motor: the
efficiency of the active line module and motor module also needs to be taken into
account. Table 6.2 shows the power losses of the different components. The table
makes a distinction between power loss and electronic power loss: power loss refers
to the loss related to the functioning of the component, electronic power loss refers
to the power that the extra control and communication electronics need in order to
function.
Table 6.2: Power losses of the set-up
Unit
Control unit
Sensor module winch
Sensor module carousel
Braking module
Basic line filter with active line module
Active line module
Motor module winch (45A)
Motor module carousel (9A)
Power loss at
nominal load (W)
Electronic
power losses (W)
24
10
10
20
16
282,8
455,2
100,4
/
/
/
/
/
22,8
25,2
20,4
The power loss for the active line module and the motor modules in Table 6.2 is
defined for nominal power flows. For non-nominal situations Siemens has provided
some figures that enable a recalculation of the power losses (see Appendix E.5). This
allows an estimation of the maximal efficiencies for a certain power demand. The
power loss in the motor module PlossM M is dependent on the current IM M that is
feeding the motor (Appendix E.5 and Equation 6.1). The power loss in the active
line module PlossAL (Equation 6.3) is dependent on the power it needs to deliver
to the motor modules (Equation 6.2). In the case where only one motor module is
active, this power is equal to the mechanical power Pmech divided by the efficiency of
the motor ηmach and the power loss in the motor module PlossM M . The combination
of these losses gives the losses in the system without the electronic power loss PlossE .
The electronic power loss is not included in the efficiency calculations because the
power consumption of these electronics is accounted as auxiliary power (like e.g.
the PC used for running the flight control software). With the same reasoning the
maximal generating efficiency can be calculated.
68
6.3. Power loss calculation
IM = √
PlossM M
Pmech
ηmach
3 × Unominal × cos(φ)
IM M
= f (PlossM M nominal ,
)
IM M nominal
PlossAL = f (
PlossM M +
(6.1)
(6.2)
Pmech
ηmotor
)
(6.3)
PALnominal
Figure 6.3a shows the calculated maximal efficiency for the carousel drive system:
a maximal efficiency of 82.6% can be reached. Figure 6.3b and Figure 6.3c show the
efficiency of the winch drive system in motor mode and generator mode: a maximal
efficiency of 87 % in motor mode and 86.7 % in generator mode can be reached.
These calculated maximal efficiencies can be compared with the measured maximal
efficiencies for a certain mechanical power, as done in Table 6.3 for the carousel drive.
At higher mechanical power the predicted efficiencies become more accurate but at
lower powers the accurateness drops. This could be explained by the usage of a fixed
(nominal) motor efficiency in the calculations: a near nominal powers the efficiency
of the motor is almost correct, at non-nominal conditions the actual motor efficiency
will differ.
The difference at non-nominal operating points can be larger than 15 % points
since Table 6.3 mentions the maximal measured efficiency operating points. When
other points with the same mechanical power are measured, larger variations in the
efficiency are observed. Table 6.4 illustrates this: the difference in the calculated
efficiency and the measured efficiency can go up to 20 % points. For this reason
the calculation of the efficiency (and required powers) on the basis of the individual
power losses cannot be used in the optimization program for the carousel drive: the
differences between the calculations and the measurements are too large.
Table 6.5 and Table 6.6 compares the maximal measured efficiency with the
calculated maximal efficiency of the winch drive in motor and generator mode. The
calculated results appear to be quite accurate, although in generator mode a lower
maximal efficiency is predicted than is measured. The largest difference between the
measured maximal efficiency and the calculated maximal efficiency is 8,4 % points in
motor mode and 13 % points in generator mode. This is already a quite significant
difference. Since this is the difference for the maximal measured efficiency, the
difference with other measuring points will be larger. The difference with the other
measuring points is illustrated in Table 6.7 and Table 6.8: these differences go up
to 34 % and 54 %. For this reason the power loss function cannot be used in the
optimization program, it is not accurate.
The power losses in the data sheet allow us to have an indication of the maximal
efficiency; this maximal efficiency is quite correct for nominal operating points but at
non-nominal operating points the accurateness drops. The non-maximal efficiencies
differ even more from the calculated maximal efficiency. Furthermore they only
take into account the power and do thus not account for different torque-speed
combinations. For these reasons the power losses calculations are not usable in the
optimization program. Another efficiency/power function has to be found.
69
6.3. Power loss calculation
90
80
70
Efficiency (%)
60
50
40
30
20
10
0
0
1000
2000
3000
Mechanical power (W)
4000
5000
(a) carousel drive in motor mode
90
80
70
Efficiency (%)
60
50
40
30
20
10
0
0
2000
4000
6000
8000
Mechanical power (W)
10000
12000
(b) winch drive in motor mode
90
80
70
Efficiency (%)
60
50
40
30
20
10
0
0
2000
4000
6000
8000
Mechanical power (W)
10000
12000
(c) winch drive in generator mode
Figure 6.3: Predicted maximal efficiency for a certain mechanical power of the
drives, derived from the data provided by Siemens
70
6.3. Power loss calculation
Table 6.3: The highest measured efficiency of the carousel drive in motor mode for
a certain mechanical power demand is compared with the highest maximal calculated
efficiency.
Mechanical
power (W)
Rotational
speed (rpm)
Torque
(Nm)
Measured maximal
efficiency (%)
Calculated maximum
efficiency (%)
3400
3000
2500
2000
1500
1000
500
95
95
100
100
80
105
30
340
290
240
190
176
91
151
79,6
78
77,3
76,6
73,7
68,5
56,2
82
81,7
81,2
80,5
79,2
76,9
70,7
Table 6.4: The efficiency of operating points with the same mechanical power is
compared with the maximal calculated efficiency at that mechanical power for the
carousel drive (in this case 500 W).
Mechanical
power (W)
Rotational
speed (rpm)
Torque
(Nm)
Measured
efficiency (%)
Calculated maximum
efficiency (%)
500
500
500
500
500
17,5
30
75
95
100
271
151
62
52
47
50
56
55
55
52
70,7
70,7
70,7
70,7
70,7
Table 6.5: The highest measured efficiency of the winch drive in motor mode for a
certain mechanical power demand is compared with the highest maximal calculated
efficiency
Mechanical
power (W)
Rotational
speed (rpm)
Torque
(Nm)
Measured
efficiency (%)
Calculated maximum
efficiency (%)
9700
8000
6000
4000
2000
1000
500
300
100
1000
900
1000
400
200
150
200
100
50
92,5
85
57,5
95
95
65
25
30
20
84,6
83,8
82,6
80
73,4
68
60
52
32,2
86,8
86,5
86
84,9
81,8
76,3
67,3
58,1
34,7
71
6.3. Power loss calculation
Table 6.6: The highest measured efficiency of the winch drive in generator mode for
a certain mechanical power demand is compared with the highest maximal calculated
efficiency
Mechanical
power (W)
Rotational
speed (rpm)
Torque
(Nm)
Measured
efficiency (%)
Calculated maximum
efficiency (%)
11900
10000
8000
6000
4000
2000
1000
700
500
300
1400
1000
1000
600
500
400
200
150
200
100
95,5
95,5
76,4
95,5
76,4
47,7
47,7
43
22,9
28,6
89,2
88,4
87,8
85,7
83,7
76,2
65,6
50,3
42,4
20,5
86,7
86,4
86
85,3
83,8
79,4
70,7
63,2
52,2
29,9
Table 6.7: The efficiency of operating points with the same mechanical power is
compared with the maximal calculated efficiency at that mechanical power for the
winch drive in motor mode (in this case 500 W).
Mechanical
power (W)
Rotational
speed (rpm)
Torque
(Nm)
Measured
efficiency (%)
Calculated maximum
efficiency (%)
500
500
500
500
500
500
500
50
100
200
250
500
1000
1200
95
50
25
20
10
5
4
46,8
59,2
60,0
58,5
50,4
38,7
33,5
67,3
67,3
67,3
67,3
67,3
67,3
67,3
Table 6.8: The efficiency of operating points with the same mechanical power is
compared with the maximal calculated efficiency at that mechanical power for the
winch drive in generator mode (in this case 1000 W).
Mechanical
power (W)
Rotational
speed (rpm)
Torque
(Nm)
Measured
efficiency (%)
Calculated maximum
efficiency (%)
1000
1000
1000
1000
1000
1000
1000
100
150
200
900
1000
1100
1400
95,5
62,1
47,7
10,5
9,5
8,6
6,7
51,6
62,3
65,6
37,9
33,7
29,1
16,4
70,7
70,7
70,7
70,7
70,7
70,7
70,7
72
6.4. Curve fit
6.4
Curve fit
As stated in the previous section, the calculation of the efficiency (or power) on the
basis of the power losses is not accurate enough. A second possibility for the power
conversion function is the usage of the measurements itself to produce a function.
This can be done by fitting a curve to the measurement results with a least square
method. The function of the curve will have the following shape:
Pelec = a0 + a1 · rpm + a2 · rpm2 + a3 · torque + a4 · torque2 + a5 · rpm · torque (6.4)
The term a0 represents the power losses when no mechanical power is required or
generated; a1 and a2 takes the influence of the rotational speed into account while
a3 and a4 takes the effect of torque into account; a5 links the electrical power to the
mechanical power (comparable with the power losses calculation).
The least square methods problem is described by:
Pelec = M · a

1 rpm(1)

1

M =
 ..
.

rpm(2)
..
.
rpm(1)2
rpm(2)2
..
.
(6.5)

torque(1)
torque(1)2
rpm(1) · torque(1)
torque(2)
..
.
torque(2)2
rpm(2) · torque(2) 

 (6.6)
..


.

..
.
1 rpm(n) rpm(n)2 torque(n) torque(n)2 rpm(n) · torque(n)
h
i
a = a0 a1 a2 a3 a4 a5

Pelec (1)

(6.7)



 Pelec (2) 



Pelec = 
..




.


(6.8)
Pelec (n)
With a being the unknown. Pelec (i) is the i-th measured electrical power, rpm(i)
and torque(i) are the rotational speed and the torque value at that the i-th measurement point. This problem is a linear least squares problem that is solved by:
a = (M T · M )−1 · M · Pelec
(6.9)
73
6.4. Curve fit
The solution for the carousel drive is shown in Table 6.9 and the solution for the
winch drive is shown in Table 6.10.
Table 6.9: Solution of the least squares method for the carousel drive
a0
a1
a2
a3
a4
a5
308,5018
-0,4145
0,0094
-0,2758
0,0025
0,1180
Table 6.10: Solution of the least squares method for the winch drive
a0
a1
a2
a3
a4
a5
293,5816
-0,0000
0,0004
0,0000
0,0666
0,1079
Figure 6.4 and Figure 6.5 show the efficiency curves of the carousel drive and the
winch drive because a power map is difficult to illustrate. All efficiencies lower than
zero are mapped to zero.
The differences between the measured efficiencies/powers and the efficiencies/powers calculated by this function are shown in Table 6.11 and Table 6.12. These tables
can be compared with Table 6.4 and Table 6.8, the accuracy of the fitted curve is a
lot higher and for this reason this function is used in the optimization of the power
orbit. There remain however still some inaccuracies, as can be seen in the first and
last line of Table 6.12. These inaccuracies originate from very steep borders between
the zero efficiency area and the non zero efficiency area in generating mode. A more
complex function than Equation 6.4 might solve these problems.
74
6.4. Curve fit
350
70
300
60
Torque (Nm)
50
200
40
150
30
100
20
50
0
Efficiency (%)
250
10
0
20
40
60
rpm
80
100
0
120
Figure 6.4: Efficiency curve of the carousel drive
Table 6.11: The efficiency of operating points with the same mechanical power
is compared with the curve fit efficiency at that mechanical power for the carousel
drive (in this case 500 W).
Mechanical
power (W)
Rotational
speed (rpm)
Torque
(Nm)
Measured
efficiency (%)
Calculated maximum
efficiency (%)
500
500
500
500
500
17,5
30
75
95
100
271
151
62
52
47
50
56
55
55
52
51,2
55,6
55,9
55,7
54,2
75
6.4. Curve fit
100
90
80
80
60
70
40
50
0
40
−20
30
−40
−60
20
−80
10
−100
−1500
Efficiency (%)
Torque (Nm)
60
20
−1000
−500
0
500
Rotational speed (rpm)
1000
1500
Figure 6.5: Efficiency curve of the winch drive
Table 6.12: The efficiency of operating points with the same mechanical power is
compared with the curve fit efficiency at that mechanical power for the winch drive
in generator mode (in this case 1000 W).
Mechanical
power (W)
Rotational
speed (rpm)
Torque
(Nm)
Measured
efficiency (%)
Calculated maximum
efficiency (%)
1000
1000
1000
1000
1000
1000
1000
100
150
200
900
1000
1100
1400
95,5
62,1
47,7
10,5
9,5
8,6
6,7
51,6
62,3
65,6
37,9
33,7
29,1
16,4
12,5
44,0
56,9
40,4
33,4
24,8
-5,6
76
6.5. Implementation
6.5
Implementation
The efficiency/power function is used in the optimization of the power generating
orbits. They were being optimized for mechanical power. Because in the end the
electrical power is used, it is better to take the electrical efficiency into account. The
increase in electrical power generation, used to compare the two optimizations, is
addressed in this section.
Influence of dimensioning
The increase will depend on the level of dimensioning: if the winch drive is overdimensioned, larger increases are expected. This is because the orbit will not be constrained
by the characteristics of the motor (torque and rotational speed) and the whole
operating zone of the drive can be used. Therefore an orbit optimized for mechanical
power will largely differ from an orbit optimized for electrical power. If however the
winch drive is correctly dimensioned (or underdimensioned) smaller increases are
expected because a mechanical or electrical optimized orbit will encounter (or come
close to) the constraints of the motor. This limits the possible differences between
the two cycles.
Indication of the importance
The importance of incorporating the electrical efficiency in the optimization is obvious
when the mechanical powers of the orbit, used for dimensioning the system (see
Section 2.1), are translated to electrical powers. Figure 6.6 shows the mechanical and
electrical power of an orbit. During the generation phase (reeling out) the magnitude
of the electrical power is lower than the mechanical power due to the electrical
efficiency. And vice versa, during the motor phase (reeling in) the magnitude of the
electrical power is larger than the mechanical power due to the electrical efficiency.
The mechanical energy generated during one orbit is equal to 2 kJ, because of the low
efficiency of the operating points the orbit requires 225 J to be completed. This orbit
illustrates the necessity to include the electrical characteristics in the optimization
program.
New plane model
The pumping cycle that Figure 6.6 shows was based on a preliminary model of
the plane. Using a correct model, multiple orbits were optimized for mechanical
and electrical energy yield. This way the importance of incorporating the electrical
efficiency in the optimization can be verified. The results of an optimization for
mechanical energy yield and electrical energy yield at low wind speed (4 m/s) and
high wind speed (10 m/s) will be compared by their average electrical power. This
average electrical power is equal to the generated energy of one orbit divided by the
duration time of the orbit. Three different orbits will be investigated: a single loop,
double loop and triple loop. The difference in these orbits is the number of loops the
plane will fly before it has to reel in.
77
6.5. Implementation
1000
Mechanical Power
Electrical Power
800
600
Power (W)
400
200
0
−200
−400
−600
−800
−1000
0
1
2
3
4
5
6
7
Time (s)
Figure 6.6: Mechanical and electrical power during a pumping cycle.
Low wind speed
The result of the optimization of the mechanical energy yield is shown in Table 6.13
and the result of the optimization of the electrical energy yield is shown in Table 6.14.
In both optimizations the orbit will not be able to harvest energy, it will require
energy. But is clear that the optimized electrical orbit requires, on average, a lower
power than the optimized mechanical yield orbit: for a single loop 43 %, for a double
loop 44 % and for a triple loop 43 %.
Table 6.13: Results for the mechanical optimized orbit at 4 m/s
Single loop
Double loop
Triple loop
Average generated electrical power
(mechanical optimized) (W)
Duration (s)
-147,6
-147,7
-143,9
4,13
8,42
12,73
Table 6.14: Results for the electrical optimized orbit at 4 m/s
Single loop
Double loop
Triple loop
Average generated electrical power
(electrical optimized) (W)
Duration (s)
-84,4
-83,1
-82,2
5,59
11,29
16,99
78
6.5. Implementation
55
55
50
50
45
45
40
40
35
35
Torque (Nm)
Torque (Nm)
The effect of incorporating the electrical efficiency is not limited to the average
power but it also changes the orbit: the duration of an orbit will increase (see Table
6.13 and Table 6.14) and the shape of the orbit will change (see Figure 6.7a and
Figure 6.7b). The control of the plane will be entirely different for a mechanical or
electrical optimized cycle. Therefore the effect of the efficiency on the control of the
plane in low wind speed conditions is large.
30
25
30
25
20
20
15
15
10
10
5
5
0
−400
−200
0
200
400
600
Rotational speed (rpm)
800
(a) Mechanical optimized
1000
1200
0
−400
−200
0
200
400
600
Rotational speed (rpm)
800
1000
1200
(b) Electrical optimized
Figure 6.7: Mechanical optimized orbit (a) and electrical optimized orbit (b) for
4 m/s wind speed in a rotational speed - torque map
High wind speed
The results of the optimization of the mechanical energy yield is shown in Table 6.15
and the result of the optimization of the electrical energy yield is shown in Table
6.16. At this wind speed the system will be able to harvest energy, but the increase
in average power by taking the electrical efficiency into account is not large: 2,5 %
for the single loop, 1,3 % for the double loop and 0,7 % for the triple loop.
This small increase in average power is due to the constraints of the drive. As
can be seen in Figure 6.8a and Figure 6.8b the orbits look very similar. The reason
for this similarity is the motor, and to be exact the motor constraints: torque is
limited to 78 Nm and rotational speed is limited to 1500 rpm. These constraints are
visible in the rotational speed - torque figures: during generation (reeling out) the
torque constraint is active, the plane is reeling out at the maximal torque. This
causes a large generation of mechanical power but also of electrical power since high
torque regions are efficient (see Figure 6.5). During the motor phase (reeling in)
the rotational speed constraint is active: the plane is being reeled in at its maximal
speed. This is the same for a mechanical and electrical optimized orbit since this
ensures that the interval at which power is required, is minimized. The two phases of
the orbit, reeling in and reeling out, are thus similar for a mechanical and electrical
optimized orbit. The difference between the two orbits can only come from small
differences in the orbits, therefore only a small increase in average power is observed.
79
6.5. Implementation
Table 6.15: Results for the mechanical optimized orbit at 10 m/s
Average generated electrical power
(mechanical optimized) (W)
Duration (s)
1726,6
1831,8
1867,9
4,92
9,84
14,59
Single loop
Double loop
Triple loop
Table 6.16: Results for the electrical optimized orbit at 10 m/s
Average generated electrical power
(electrical optimized) (W)
Duration (s)
1770
1854,7
1881
5,18
10,35
15,12
90
90
80
80
70
70
60
60
50
50
Torque (Nm)
Torque (Nm)
Single loop
Double loop
Triple loop
40
30
40
30
20
20
10
10
0
0
−10
−1500
−10
−1500
−1000
−500
0
500
1000
Rotational speed (rpm)
(a) Mechanical optimized
1500
2000
−1000
−500
0
500
1000
Rotational speed (rpm)
1500
2000
(b) Electrical optimized
Figure 6.8: Mechanical optimized orbit (a) and electrical optimized orbit (b) for
10 m/s wind speed in a rotational speed - torque map
Unconstrained
In order to illustrate that the high wind speed orbits are constrained, a simulation
without winch drive constraints was made. Of course, this result is not realistic
since the conversion of mechanical to electrical power is done for values that have
not been measured and there is no limit on the power of the winch drive. It is
however a resemblance of a bigger drive. The results are shown in Figure 6.9a and
Figure 6.9b, the average electrical power for the mechanical optimized orbit is -378 W
(requiring power) but for the electrical 2638 W (generating). This thus shows that
incorporating the electrical behaviour of the winch drive can have a very large effect
on the optimized orbit.
80
400
400
350
350
300
300
250
250
Torque (Nm)
Torque (Nm)
6.6. Conclusion
200
150
200
150
100
100
50
50
0
−2000
0
−1000
0
1000
Rotational speed (rpm)
2000
(a) Mechanical optimized
3000
−2000
−1000
0
1000
Rotational speed (rpm)
2000
3000
(b) Electrical optimized
Figure 6.9: Optimized orbits for 10 m/s wind speed without winch drive constraints
in a rotational speed - torque map
Assessing the final system
The results from the low wind speed and high wind speed conditions can be used
to asses the dimensioning of the components of the final system. As can be seen
in Figure 6.7b, the system is overdimensioned for low wind speed conditions: the
power orbit does not reach the nominal values of the winch drive, which lowers the
efficiency considerably. This explains that the power orbit requires energy instead
of producing energy. When looking at Figure 6.8b the opposite conclusion can be
made: the system is underdimensioned, the constraints of the winch drive are reached
(78 Nm and 1500 rpm) and do not allow to make optimal use of the high wind speeds.
The average wind speed in the surroundings of Leuven is 5-5,75 m/s [11]. This
number fits in between the low wind speed (4 m/s) and high wind speed (10 m/s) of
the simulations. This indicates that the final system is properly dimensioned, the
power orbits will lie between an under- and overdimensioned system.
By spending a lot of time in the lab testing the drives, hands-on experience was
gained. These experiences confirm that the choice for Siemens was a good one and
that the drives behave as they should.
6.6
Conclusion
Thorough testing resulted in an efficiency/power function that enables a conversion of
mechanical power to electrical power. It also showed that the system was dimensioned
properly. The function could then be incorporated in the optimization of pumping
cycles. The most optimal cycles in low wind speeds are changed considerably by the
new optimization. And even for high wind speeds, were the operations are limited by
motor constraints, the average electrical power can be increased by a few percentages.
If airborne wind energy is to become an economic alternative for wind turbines, these
extra percentages of output power can become game changing.
81
Chapter 7
Conclusions, Leading to the
Future
This master’s thesis shows that designing an electrical system for airborne wind
energy is not trivial. It also shows that simplifying or neglecting the electrical system
for calculating and optimizing the energy production of AWE yields non-optimal
results. This is something that, to the authors’ knowledge, has never been taken into
account when considering AWE. Those two aspects are the main conclusions of this
thesis.
The first section of this chapter recapitulates very quickly how those conclusions
have been reached. The following sections describe what could be further reached in
the future. In the first place this means taking a look at the future of the set-up.
What could be further developed?
To conclude, the scope of this master’s thesis is broadened. What would change
if the electrical energy conversion system was designed for actual electrical energy
production? We try to envision improvements and extensions that make the system
better from an electrical energy production point of view.
7.1
Concluding the design
In Chapter 2 the system requirements were defined and translated into an initial
design. This design was especially important for companies to get a clear view of
what was electrically intended and required for this project. In Chapter 3 the system
requirements were then translated in a more practical form. The proposals of the
contacted companies showed how a real system would look like. Also the safety
analysis of the system was further developed.
In Chapter 4 the same was done for the plane. In this chapter a trip was made to
the power electronics inside the flying part of the system. The flow of work however
was the same: from system requirements to a first design, to a real world design and
to an implementation. Possible improvements for the plane were also discussed.
Chapter 5 then put everything together and finalized the design. This chapter
showed how everything will be implemented and why it was designed that way. All
82
7.2. The future of testing
Figure 7.1: Implementation of the drives for the test set-up
these chapters show that designing an electrical energy conversion system for AWE is
a complex task which should not be rushed, since it has a large effect on the overall
operations of the system and has a great impact on safety.
Chapter 6 used this finalized design to implement the electrical properties in the
optimization of power generating orbits. By testing the efficiencies of the drives, from
the grid to the outgoing shaft, an efficiency and power map was made which could
be used in the optimization program. By including this it is shown that the effect
of the electrical part, although often ignored due to its high and rather constant
efficiency, is significant.
7.2
7.2.1
The future of testing
Practical implementation
Although the design is completely finished, the practical implementation isn’t. The
drives, as schematically shown as in Figure 5.1, have been assembled for testing, as
can be seen in Figure 7.1. Moving them to the final set-up in their cabinets should
be no problem. All the components for the final implementation shown in Figure 5.4
have been ordered and some additional components are ordered as well.
The biggest loose end is probably the communication. While the proposed
system, with a PLC as a middle man, as explained in Section 5.4, theoretically
works, the practical implementation will definitely show some unforeseen difficulties.
Communication is however extremely important. And while a temporarily solution
83
7.2. The future of testing
is available (using a Windows machine running STARTER), this is not a practical
method for use in a closed-loop control system.
7.2.2
Validation of the results
While the results from Chapter 6 show great promise, validating these numbers
has not yet been possible. The assumption has been made that the steady state
efficiencies are suited for modeling the overall efficiency of the drives when going
through a dynamic cycle. The test set-up for testing the generator efficiency was
perfect for validating this assumption. We could have manually put in a cycle (by
changing the speed and torque setpoints of the driving motor) and then see what
the net energy output or input was. By performing these tests it can be verified that
the dynamic efficiency is the same as the steady state efficiency. However since the
major fault occurred (Section 5.5) this could not be done.
7.2.3
Standalone system: the generator
As explained in Section 2.2 powering the system with a generator poses some problems.
Powering the system with a cable connection however poses some problems as well.
The main problem is not being able to test further then (in this case) 300 m away
from a grid connection. Another important problem is that the voltage drop is so
significant that to keep the voltage within a 5 % margin only 8 A can be drawn
(although it is a 32 A cable). As most of the components connected to the grid are
able to deal with significant undervoltages 1 , drawing more current is not expected
to be a problem.
Depending on the results of the tests and the actual power flows, instead of
estimated and calculated ones, a generator might become a good option again. Good
dimensioning however is very important and because of the lack of numbers to work
with, a grid connection is the better solution to start with.
7.2.4
Sliprings
It has been mentioned a couple of times in various chapters that sending sensor
signals (encoder or resolver) through a slip ring might not work. Siemens’s resolvers
should be able to deal with this. However because of the lack of correct components
and a misunderstanding in one of the orders, this has never been tested. Controlling
the winch motor without the resolver signals is possible, but the accuracy of the
speed control loop will not be as good as with a closed loop system. Should the
resolver signals not reliably go through the slip rings, than vector control might be
more suitable than servo control for reasons mentioned in Section 5.2.2.
1
The undervoltage limit for ATX power supplies is 180 V [18] which translates into a current
of 34 A going through the cable. The undervoltage limit for the drives is 85% at which it will
commission a warning and 75 % at which it will turn off, this translates into a current of 39 A going
through the cable
84
7.3. Beyond testing: electricity production
7.2.5
Modeling the drives for use in the optimization
As explained in Chapter 6 integrating the drives’ efficiency or power draw in the
optimization has some clear advantages. This was done by fitting a curve on the
measured efficiency map. However testing the drives to get that efficiency map takes
a lot of time. Future research might solve this by developing or finding an adequate
model that is able to generate this efficiency map, that is suitable for use in the
optimization. The data is present to check if the results are accurate and it will then
be very easy to translate the electrical part of the optimization to a different system.
7.3
7.3.1
Beyond testing: electricity production
The advantages of phase shifting
Because of the nature of pumping AWE, one cycle involves motor and generator
mode. This thus means tremendous power fluctuations (sign changing). Problems
like the ones described in [8], were they are caused by the fluctuating power of waves,
can then be expected. These problems go from flicker, due to the pulsating voltage
caused by the voltage drop over the cable, till a black-out, should the rotor angle
stability of the generators from the grid be lost.
However, due to the extensive level of control over the plane and the cycle, it is
very possible to limit this pulsating power when multiple units are available. Like
limiting the vibrations in an internal combustion engine by using more cylinders, the
power fluctuations can be limited by using more units with a phase difference. Figure
7.2 shows this effect for a different number of units and for different loops for which
the cycle was optimized. For easy visualizing each cycle is made non-dimensional by
dividing by the respectable maximum power (so for one unit the maximum power of
one unit, for two units twice the maximum power of one unit etc.).
The coupling of the different units can be done on the AC level, but it can also be
done on the DC bus, which enables more interesting possibilities, described in Section
7.3.3. Other solutions like energy storage can also solve the problem of fluctuating
power. For short periods like ours, supercapacitors could buffer the DC bus. When
units are connected with a phase shift on the DC bus and there is enough DC bus
capacitance, the power fluctuations can be completely corrected.
85
7.3. Beyond testing: electricity production
one unit
two units
three units
four units
eight units
0.8
0.6
power (per unit)
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
time (s)
(a) Single loop
one unit
two units
three units
four units
eight units
0.8
0.6
power (per unit)
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1
1
2
3
4
5
6
7
8
9
10
11
time (s)
(b) Double loop
one unit
two units
three units
four units
eight units
0.8
0.6
power (per unit)
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1
2
4
6
8
10
12
14
16
time (s)
(c) Triple loop
Figure 7.2: The effect on power fluctuations by phase shifting, the cycles are for
an electrical power optimization at 4m/s wind speed
86
7.3. Beyond testing: electricity production
7.3.2
Controlling the harvested wind energy
Traditional wind turbines have a variety of effects on the electricity grid. Issues like
uncontrollable reactive power consumption and low power factor, power fluctuations
on the grid due to variations of wind speed, voltage fluctuations due to those power
fluctuations in weak grids and voltage distortion due to harmonic distortion can
occur due to multiple factors [24]. While harmonic distortion and reactive power
consumption are caused by the generator and (when present) converter, power and
voltage fluctuations are caused by the nature of the wind itself. Using more elaborate
generators like synchronous generators with a power converter or doubly fed induction
generators can solve or mitigate some of the problems [23]. The problems due to
fluctuating wind speeds (and thus power) can be limited but not solved.
Wind power becomes higher and more consistent when going to higher altitudes
[4] [5]. This means a higher capacity factor and less power fluctuations due to the
wind. Therefore also these power fluctuations will be lower using pumping AWE.
Because the designed system uses a (permanent magnet) synchronous generator with
power converter, some of the other issues with wind energy can also be mitigated.
Since the flight control software is able to generate power in an optimal way, it is
also able to generate power in a non-optimal way. With the use of reversed pumping,
it is even possible to consume power, instead of generating, should prices become
negative. This offers wide possibilities as to load balancing. Lots of issues exist today
with fluctuating power and thus electricity prices due to renewable energy sources.
AWE offers such an extensive amount of control over the power generating cycle that
load balancing and load following with this renewable energy resource is a very good
possibility.
7.3.3
Common DC bus
When connecting multiple traditional wind turbines in a farm, they are usually
connected via their AC connection, even if an internal DC bus is present [37]. For
offshore wind farms it is worthwhile to connect via a high voltage DC (HVDC)
cable to limit losses. There is thus an AC collection point where the AC voltage is
converted to HVDC and this is then connect to the mainland where it is inverted
and connected to the main AC grid [25] [6].
The designed system already has an internal DC bus, which thus offers the
possibility to interconnect multiple units on the DC level. The DC bus can then be
connected to the grid with one single inverter (and via a DC power cable for offshore
farms). This offers multiple advantages, similar to advantages of interconnected
wind turbines. Especially HVDC based on voltage-source converters has multiple
advantages on the grid it is connected to [20]. First of all the advantages of phase
shifting, as described above, are now present on the DC bus and the remaining
fluctuations are thus not seen on the AC side. Furthermore an intelligent inverter
offers lots of possibilities to keep the AC voltage steady. When including some energy
storage (for example capacitors are always present on a DC bus) the possibilities
become even more vast as to power buffering.
87
Appendices
88
Appendix A
The Full Siemens Quote
On the next pages the full Siemens quote can be found. This document is however
partially in Dutch.
89
Appendix B
Datasheets
This appendix holds relevant datasheets of components used in the master’s thesis.
98
B.1. Carousel motor
B.1
Carousel motor
This is a custom made motor and because of all the options, the data can’t be
retrieved in a manual. The datasheet in table B.1 was provided by Siemens and
includes all necessary data on the induction motor, gearbox and encoder.
Table B.1: Datasheet of carousel motor and gearbox provided
by Siemens
Product
Type designation:
Order number
Order codes
Gearbox data
Type of construction
Nominal torque
Output torque
Service factor
Transmission ratio
Output speed
Mounting type
Output shaft
Connection type
Motor data
Nominal power
Asynchronous speed
Number of poles
Voltage
Frequency
Rated current
Rel. starting current
Cos Phi
Efficiency
Rel. starting torque
Rel. av. run-up torque
Rel. breakdown torque
Moment of rotor inertia
Temperature class
Terminal box position
Degree of protection
Venting
Fan material
Circuit (Starting)
Operating mode
Helical geared motor
ZF48-LA112ZMP4E-IN
2KJ1103-1GJ13-1FL1-Z
D88+H03+K01+K06+L02+L50+
M00+M71+N48+Q47+Q95
V1
420
389
1,08
14.68
98
Flange (A200)
Solid shaft (V30 x 60)
Feather key
4
1.440
4
230 / 400
50
14 / 8,2
6,9
0,81
86.60
2,8
2,5
3,2
0,014
F
1AK
IP55
Self ventilation
Synthetic fan
D/Y (Y-D/Y)
S1
D88
[Nm]
[Nm]
[1/x]
[1/min]
H03
[kW]
[1/min]
[V]
[Hz]
[A]
[IA/IN]
[%]
[TA/TN]
[THm/TN]
[TK/TN]
[kg*m2]
M71
K01
99
B.1. Carousel motor
Gearbox options
Output bearing
Output sealing
Oil level control
Oil drain
Venting
Gearbox oil
Oil quantity
Housing material
Motor options
Miscellaneous
High efficiency motor
Efficiency class
Encoder data
Encoder type
Number of impulses
Degree of protection
Design
Output signal
Connection
Mechanical Protection
General data
Painting
Color
Weight approx.
Bearings normal
Radial shaft seal (NBR)
Oil level plug
Oil drain plug
Vent filter
Mineral oil CLP ISO VG220
1,8
Cast iron
K06
[l]
Motor retro-fittable on N-Side
N48
M00
IE2
Incremental encoder (1XP803210)
1024
IP66
HTL 8-30 VDC
6 Kanal (A-, B-, 0-Spur + Invertierung)
Kabel+Kupplungsdose
encoder underneath cover
Q47
Finish C1
Sky blue RAL 5015
52
L02
L50
Q95
[kg]
100
B.2. Winch motor
B.2
Winch motor
The data of this motor can be found in [31] and in table B.2.
Table B.2: Datasheet of the winch motor and gearbox as found in [31]
Product
AFK7 synchronous motor with Wittenstein reductor
Order number motor
1FK7105-2AF71-1SH0
Order number gearbox LP120S-MF1-3-1K1/1FK7105-5AC71
Motor data
Rated power
8.2
[kW]
Rated speed
3000
[rpm]
Maximum speed
5000
[rpm]
Static torque
48
[Nm]
26
[Nm]
Rated torque
Rated current
18
[A]
Number of pole pairs
4
Moment of inertia of rotor (without brake)
154 × 10−4
[kgm2 ]
Weight (without brake)
39
[kg]
Weight of the brake
4
[kg]
Efficiency
94
[%]
Static current
31
[A]
Protection class
IP64
Multi-pole resolver
3
[poles]
Gearbox data
Transmission ratio
3
[1/x]
Maximal acceleration torque
305
[Nm]
Nominal output torque
155
[Nm]
Emergency stop torque
400
[Nm]
Nominal input speed
2600
[rpm]
Maximum input speed
4800
[rpm]
Mean no load running torque
1,1
[Nm]
Maximal torsional backlash
<= 8
[arcmin]
Torsional rigidity
30
[Nm/arcmin]
Maximal axial force
4000
[Nm]
Maximal radial force
4600
[Nm]
Efficiency at full load
97
[%]
Weight
8,6
[kg]
Maximum permitted housing temperature
90
[◦ C]
Protection class
IP64
Moment of inertia
7.8
[kgcm2 ]
101
Appendix C
The Full MAT
On the next pages the ‘General risk assessment for the acquisition and handling
of Machines, Apparatuses en Test-set-ups’ form can be found. This document is
however in Dutch.
102
DIENSTEN ALGEMEEN BEHEER
DIRECTIE STAFDIENSTEN ALGEMEEN BEHEER
DIENST VGM
W. DE CROYLAAN 58 – BUS 5530, BE-3001 LEUVEN
TEL. + 32 16 32 20 24
FAX + 32 16 32 29 95
WWW.KULEUVEN.BE/VGM vgm@kuleuven.be
RISICOANALYSE Carousel2 - HighWind – Februari / 1
Algemene risicoanalyse voor het verwerven van en activiteiten met Machines,
Apparaten en Proefopstellingen (MAP)
KATHOLIEKE
UNIVERSITEIT
LEUVEN
Controleer eerst in het overzicht (onder standaard formulieren) of er voor de MAP een specifiek
risicoanalyseformulier bestaat, zoniet gebruik dit algemene risicoanalyseformulier.
Vul het formulier elektronisch in, in overleg met het VGM-antennelid CV/EV. Indien blijkt dat na het invullen
van deel 2 de MAP een verhoogd risico (=risicoklasse MAP2 of 3) heeft, dan dient de risicoanalyse door de
VGM-antennecoördinator aan de Dienst VGM overgemaakt te worden.
Deel 1: Identificatie van de afdeling (gebruikers) en beschrijving van de MAP
Identificatie van de afdeling:
Aanvrager/contactpersoon: Andrew Wagner
Tel:
E-mail adres: andrew.wagner@esat.kuleuven.be
Afdeling: ESAT - SISTA
Promotor: Diehl Moritz
Afdelingshoofd: Joos Vandewalle
(Hiërarchisch verantwoordelijke volgens het officiële organigram)
Identificatie van de MAP:
Toestelnaam: Carousel2 - HighWind
Totaal nominaal vermogen: 16 kW
Serienummer:
Waterinhoud: 0 liter.
Gebouw:
Eigen constructie: Ja
Nee
Lokaal:
Tweede hands: Ja
Nee
bouwjaar: 2013
Buitenlandse leverancier: Ja
Nee
Dossiernummer (VGM): 2013.0387
De MAP wordt mogelijks verkocht: Ja
Nee
Identificatienummer (afdeling):
De MAP of de individuele onderdelen hebben een CE-markering (indien bouwjaar na 1995 is dit nvt).
Ja
Nvt
Nee, opmerking
Indien samenbouw specifieer de onderdelen:

Beschrijf het gebruiksdoel van deze MAP en de randfactoren (uitvoerige beschrijving)
Het ontwerp bestaat uit twee motoren, twee dc/ac convertoren en één gemeenschappelijke ac/dc convertor met bijhorende
controle eenheid. De lichtste motor (4kW) wordt gebruikt om de carrousel te laten ronddraaien. De tweede motor (8,8kW),
aangesloten via een sleepring, wordt gebruikt om een lier aan te drijven. Deze laatste motor werkt ook als generator. Beide
motoren worden gevoed via een individuele frequentieomvormer (dc/ac). Deze zijn dan weer via een gemeenschappelijke
dc bus verbonden met een 16kW ac/dc convertor, welke ook vermogen terug op het net kan zetten.
Toepassingsgebied (afbakening) van de risicoanalyse:
Gebruik
Onderhoud
Instellen/afstellen
Bijkomende info:
Deze risicoanalyse betreft:
Het betreft een nieuwe MAP
Het betreft een aanwezige/bestaande MAP (nog niet eerder gemeld)
Het betreft afvoeren en definitief uit dienst nemen van een MAP met DossierNr
(indien dossiernummer is ingevuld hoeft er verder niets ingevuld te worden)
Het betreft een wijziging/uitbreiding van een bestaande reeds eerder gemelde MAP
Deze wijziging/uitbreiding betreft (gelieve aan te duiden):
lokalen waar het experiment plaatsvindt
andere wijzigingen/ wijziging risico’s
Dossiernummer of referentienummer vorig advies:
(indien gekend)
(indien dossiernummer is ingevuld enkel de wijzigingen beschrijven verder in het formulier)
Indien VGM-DOSSIER beschikbaar:
experiment in het kader van een bestaande activiteit
Geef nummer van de activiteiten:
1
experiment in het kader van een nieuwe activiteit (in overleg met VGM-antenne en Afdelingshoofd )
Geef naam van de nieuwe activiteit voor het VGM-dossier:
(max. 40 karakters)
Doorloopproeven (onbewaakt experiment binnen of buiten de diensturen) – vul het bijhorende formulier in.
Pagina 1 van 6
versie oktober 2012
Deel 2: Analyse van de gevaren, de aanwezige risico’s en de bijhorende maatregelen
Onderstaand veld kan u vrij bewerken en dient voor het toevoegen van oa. tekst, foto’s, schema’s, opsomming
onderdelen, …
1.
2.
3.
4.
5.
6.
7.
8.
9.
Control unit
Data kabel
AC/DC convertor (16kW)
DC/AC convertor
Vermogen kabel
Motor
SMC module
Encoder kabel
DC bus (intern)
Pagina 2 van 6
versie oktober 2012
Algemene risico’s
JA
NEE
NVT
OK
NOK
NVT
Er is kans op gehoorschade, vb. door lawaaiproductie boven 85dB.
Er is kans op snijden, pletten, klemmen, perforeren, gegrepen worden, oog- of andere letsels bv.





scherpe randen of hoeken
onafgeschermde bewegende delen/aandrijfmechanismen
afschermingen die snel overbrugbaar zijn (zonder gereedschap of veiligheidscontact)
vrijkomen van stof, damp of vloeistof
wegschietende of vallende delen.
doordat onderdelen kunnen breken of uiteenspringen.



onvoldoende bewegingsruimte
onvoldoende verlichting rond (en eventueel in) het toestel.
losliggende kabels
een hoogte waar men zich kan bevinden (relevant vanaf 50cm valhoogte)


rechtstreeks aanraakbare elektrische delen
onvolledige of het gebrek aan aarding (of is niet dubbel geïsoleerd).
beschadigde of niet correct aangesloten elektrische kabels

rechtstreeks aanraakbare hete of zeer koude oppervlakken

Er is kans op vallen of struikelen bv.

Er is kans op elektrocutie (direct of indirect) bv.

Er is kans op verbranden bv.

werken met open vlam
De MAP kan omvallen of kantelen omdat deze niet stabiel staat.
Er is kans op het ontstaan van brand
Er is kans op explosie (oa. door druk, stof, gas vloeistof, …).
Andere:
Omschrijving van de te nemen maatregelen indien JA:

(Elektrische) afscherming

Zekeringen, differentieelschakelaars, automaten
Voorwaarden van bediening
De MAP kan in alle omstandigheden veilig stoppen op een snelle en veilige manier (indien dit niet te
realiseren is met de normale bediening is een noodstop aangewezen).
De noodstop (indien aanwezig) brengt de MAP in een veilige toestand.
De MAP kan enkel starten door een bewuste actie.
De MAP kan niet automatisch herstarten na een spanningsval, of dit vormt geen risico.
De bedieningsmechanismen staan niet in de gevarenzone.
Het stopcommando heeft voorrang op het startcommando.
De MAP is duidelijk en éénvoudig los te koppelen van het elektrische stroomnet.
De gebruiksaanwijzing is aanwezig en omvat:

Gebruik (start, stop, signalisatie, …)

Onderhoud (onderhoudsprogramma, testen, …)

(de)monteren en inbedrijfstelling
Andere:
Omschrijving van de te nemen maatregelen indien NOK:

Pagina 3 van 6
versie oktober 2012
Organisatorische maatregelen
OK
NOK
NVT
Onderhoud, herstellingen en periodieke reiniging worden uitgevoerd volgens de specificaties, hierbij
wordt de MAP eerst uit dienst genomen.
Er is een technisch dossier dat minstens de handleiding, het onderhoudslogboek en de eventuele
wettelijke keuringen omvat.
De belangrijkste instructies (indien aanwezig) zijn aanwezig bij de MAP
De MAP wordt niet gebruikt buiten zijn normale gebruiksdoel (beschreven in deel 1).
Elke bediener heeft voldoende kennis (dmv opleiding, ervaring, gebruiksaanwijzing, …) over/om:

de bediening van het toestel: start-stop-noodstop.

een gevaarlijke of abnormale situatie te herkennen.

Het gebruiksdoel van de MAP
Elke bediener heeft kennis van de noodprocedures en weet wat hij/zij moet doen bij faling of incident.
Afgezonderde tewerkstelling (oa. afgezonderde ruimte, buiten werkuren): indien de persoon alleen
werkt en de kans bestaat dat hij niet zelfstandig alarm kan slaan is minstens één van volgende
maatregelen aanwezig.
Iemand anders in de buurt die weet heeft van de lopende activiteit.
Een automatisch dodemansalarm (aan te vragen via de CD)
Er is voldoende (=overeenstemmend met het risico) signalisatie van

De restrisico’s (warme oppervlakken, elektrisch risico, bewegende delen, …)

De noodzakelijke aandachtspunten (bril, gehoorbescherming, handschoenen, …)
Er is een aangeduide verantwoordelijke voor deze MAP (van toepassing bij risicovollere toestellen).
Andere:
Omschrijving van de te nemen maatregelen indien NOK:

Uitvallen van nutsvoorzieningen (incl. afwijken van specificaties)
Is dit een
Indien een probleem - omschrijving van de
Beschrijf het gevolg hiervan
VGM
maatregel.
probleem
Elektriciteit
Ventilatie
Gasvoorziening
(Koel)water
Perslucht
Inerte atmosfeer
Vacuüm
Andere:
Motoren komen tot stilstand
Controle kast warmt op
Interactie met de omgeving
Zijn er binnen het lokaal nog andere MAP of infrastructuur met gevaren, zoja welke extra/bijkomende risico’s brengen deze
met zich mee?

Omschrijf de reeds geïmplementeerde en de nog te nemen maatregelen:

Duidelijke schriftelijke en visuele instructies voor gebruik en wat de gevaren zijn
Pagina 4 van 6
versie oktober 2012
Voorwaarden voor het melden – duid
dit ook aan
Specifiek gevaren
Gebruik van gassen (welke + gebruiksdruk):
Vanaf E4 met vrijgave
Gebruik van cryogene gassen (welke + hoeveelheid):
Indien kans op zuurstofverdringing
(<19%O2 in lucht)
Vanaf E4 met vrijgave
Pyrofoor
Vanaf E4 met vrijgave
Gebruik van poeders (welke):
Gebruik van chemische producten
Naam product
Cas nr.
Klasse
(E1, …)
Hoeveelheid,
concentratie
Belangrijkste risico (brandbaar, giftig, …)
Gebruik van biologische agentia (welke):
Steeds, zie bioveiligheid
Gebruik van ioniserende straling (welke):
Steeds, zie radioprotectie
Gebruik niet-ioniserende straling (welke):
Magneetvelden: Maximale veldsterkte:
Gauss.
Statisch magneetveld
Wisselend magneetveld: frequentie:
Hz
Gebruik van lasers
Laserklasse
Golflengtebereik:
Verhoogde/verlaagde druk in glaswerk.
Gebruik van (Hoog)spanning (niet afgeschermde):
Max. Spanning 600V,
Max. outputstroom =23000mA.
Andere:
Indien de gebruiker wordt
blootgesteld.
Vanaf een statisch veld van 5 Gauss
buiten de opstelling.
Laserklasse 3 en 4 met open bundel
(ook tijdens uitlijnen).
Zonder overdrukbeveiliging.
Contacten zijn niet afgeschermd en
Imax≥10mA.
Welke concrete risico’s zijn aanwezig:

Electrisatie
Welke concrete maatregelen zijn genomen om de beschreven risico’s op te vangen:

(Elektrische) afscherming en bescherming (automaat, differentieel, zekeringen …)
Collectieve:
Vereiste standaard beschermingsmiddelen
Indien niet aanwezig dienen deze aangevraagd te worden
Individuele:
Gesloten systeem
Zuurkast(trekkast)
Plaatselijke afzuiging
Ruimtelijke afzuiging
Veiligheidsscherm
Veiligheidskooi (volledige omsluiting)
Opvangbakken onder opstelling
Gasdetectie
draagbare
ruimtelijk
Branddetectie (ruimtelijk)
Verliesstroomschakelaar op MAP
Andere: Automaat
Gelaatsbescherming:
Veiligheidsbril art. 18042
Ruimtezichtbril art. 15912
Gelaatsscherm art. 24176
laserbril
Ander type:
Handschoenen
wegwerpnitrile EN 374 artnr. 58951
wegwerpvinyl EN 374 (op aanvraag)
nitrile M/L/XL art.159.29/.30/.31
cryogene handschoenen
Ander type:
Gehoorbescherming:
Wegwerp oordopjes
Gehoorbeugel
Oorkappen
Op maat gemaakte
Ademhalingsbescherming
Stofmasker P1 art 15918
Stofmasker P3 art.16236
wegwerphygiënemasker
halfgelaatsmasker met volgende patronen:

volgelaatsmasker met volgende patronen:

Ander type:
Veiligheidsschoenen
Wegwerp hygiëne haarnetje
Laboschort/werkkledij
Bijkomende analyse van de risico’s die in bovenstaande onderdelen niet aan bod komen (vrij te bewerken).
Beschrijving van het risico
Vallen van de kabel bij het loskomen van de
vlieger
Pagina 5 van 6
Bijhorende maatregel
Het terrein waarbinnen de kabel kan vallen wordt visueel afgebakend.
Indien iemand deze zone betreedt, wordt het experiment stopgezet.
versie oktober 2012
Deel 3: Beoordelen van de risicoanalyse
De MAP dient, conform de procedures, aan de Dienst VGM gemeld te worden als uit de risicoanalyse blijkt dat
minstens aan één van onderstaande voorwaarden voldaan is, duid deze telkens aan:
Een “NOK (of JA) - uit de risicoanalyse - deel 2” is niet opgevolgd door een afdoende maatregel
De MAP bij “specifieke gevaren - uit de risicoanalyse - deel 2” beantwoordt aan de voorwaarden
voor te melden
Bij “specifieke gevaren” uit de risicoanalyse (deel 2) zijn de concrete maatregelen onvoldoende
om het risico weg te werken/ te reduceren
Indien het uitvallen van nutsvoorzieningen relevante gevolgen heeft in kader van VGM.
Ondanks het implementeren van de beschreven maatregelen is er nog steeds een reële kans op
een lichamelijk letsel (korte en/of lange termijn)
Op basis van de melding kunnen er bijkomende gegevens worden opgevraagd.
Personen die het experiment uitvoeren (niet noodzakelijk voor eenheden met activiteiten opgenomen in het VGM-dossier)
Naam - voornaam
Personeelsgroep
Wagner Andrew
Stuyts Jeroen
Vandermeulen Wouter
KU
KU
KU
KU
KU
Student KU
Student KU
Student KU
Student KU
Student KU
UZ
UZ
UZ
UZ
UZ
VIB
VIB
VIB
VIB
VIB
Externen:
Externen:
Externen:
Externen:
Externen:
Bezorg dit formulier (geen pdf-versie) elektronisch aan uw VGM-antennecoördinator, promotor en
leidinggevende. De VGM-antennecoördinator bezorgt deze melding aan de Dienst VGM
Opmerkingen/toevoegingen/advies van de Dienst VGM
Pagina 6 van 6
(vak voorbehouden voor de Dienst VGM)
versie oktober 2012
Appendix D
Reliability Calculations
On the next pages MATLAB code for the calculation of the reliabilities of the plane
power systems is shown.
1
%% C a l u c l a t i o n f o r t h e r e l i a b i l i t y o f t h e p l a n e power system
2
3
% A c o n s t a n t f a i l u r e r a t e i s assumed .
4
5
close a l l
6
7
%% P l o t t i n g :
8
9
10
11
12
13
14
plot_top100 = 0 ;
plot_open = 0 ;
p l o t _ t o t a l _ b a s i c =1 ;
plot_total_secured = 1;
plot_separate = 0;
plot_total_switched = 0;
15
16
%% OpenUps
17
18
%No d a t a i s found on r e l i a b i l i t y . We w i l l asume f o r t h e
c a l c l u a t i o n s a Mean Time Between F a i l u r e (MTBF) o f 8760
h o u r s : MTBF_open = 8760 h o u r s and d i v i d e t h e time a x i s by
t h i s assumptiom . This way a d i m e n s i o n l e s s time a x i s w i l l
be c r e a t e d and t h e e x a c t MTBF o f t h i s component i s not
important .
19
20
MTBF_open = 8 7 6 0 ;
MTTF_open = MTBF_open −1; %Assumption o f a Mean Time To
Repair (MTTR) o f 1 hour , Mean Time To F a i l u r e (MTTF)
22 Lambda_open = 1/MTTF_open ;%MTTF = 1/Lambda . With lambda
equal to the f a i l u r e rate
21
109
23
24
%The r e l i a b i l i t y o f t h i s component i s e q u a l t o exp(−
lambda_open ∗ t )
25
i f plot_open == 1 ;
27
time = [ 0 : 1 : 8 7 6 0 0 ] ;
28
plot ( time /MTTF_open, exp(−Lambda_open . ∗ time ) ) ;
29 end
26
30
31
%% S t a r t i n g o f a f i g u r e
32
figure ( ) ;
hold on ;
35 ylabel ( ’ R e l i a b i l i t y ’ ) ;
36 xlabel ( ’ time ( h o u r s ) /MTTF’ ) ;
33
34
37
38
%% T o t a l B a s i c
39
40
%The r e l i a b i l i t y o f t h e p l a n e i s e q u a l t o t h e r e l i a b i l i t y o f
t h e open−ups board ! The p l a n e works i f : open ups work
41
42
Lambda_tot_basic = Lambda_open ;
43
i f p l o t _ t o t a l _ b a s i c == 1
time = [ 0 : 1 : 8 7 6 0 0 ] ;
46
plot ( time /MTTF_open, exp(−Lambda_tot_basic . ∗ time ) ) ;
47
legend ( ’ R e l i a b i l i t y o f t h e o r i g i n a l system ’ ) ;
48 end
44
45
49
50
%% T o t a l s e c u r e d DC Bus
51
52
%The p l a n e i s f u n c t i o n a l i f : one o f t h e open−ups b o a r d s
s t i l l works . In t h i s example 2 open−ups b o a r d s a r e
p r e s e n t t h e r e l i a b i l i t y i s e q u a l t o 1 − (1 − t h e
r e l i a b i l i t y o f board 1) ∗(1 − t h e r e l i a b i l i t y o f board 2)
53
54
55
56
57
58
59
60
61
i f p l o t _ t o t a l _ s e c u r e d == 1 ;
endtime = 8 7 6 0 0 ;
time = [ 0 : 1 : endtime ] ;
R = zeros ( s i z e ( time ) ) ;
f o r i = [ 1 : 1 : endtime +1]
R( i ) = (1−(1−exp(−Lambda_open∗ time ( i ) ) ) ∗(1−exp(−
Lambda_open∗ time ( i ) ) ) ) ;
end
plot ( time /MTTF_open, R, ’ g ’ ) ;
110
legend ( ’ R e l i a b i l i t y o f t h e o r i g i n a l system ’ , ’ R e l i a b i l i t y
o f t h e s e c u r e d bus system ’ ) ;
62
63
end
64
65
%% T o t a l s e p a r a t e
66
67
%The p l a n e i s f u n c t i o n a l i s a l l b o a r d s f u n c t i o n . I t i s i n a
di m i n s h e d f u n c t i o n a l s t a t e i f one o f t h e open ups b o a r d s
works . This i s t h e same as t h e s e c u r e d DC bus , b u t w i t h
no c o n t r o l l o g i c t h a t s w i t c h e s . The r e l i a b i l i t y o f t h e
p l a n e ( f o r a l e s s c o n t r o l a b l e p l a n e ) i s t h e same .
R e l i a b i l i t y d i m i n i s h e d = 1 − (1 − t h e r e l i a b i l i t y o f
board 1) ∗(1 − t h e r e l i a b i l i t y o f board 2) . R e l i a b i l i t y
f u l l = ( t h e r e l i a b i l i t y o f board 1) ∗( t h e r e l i a b i l i t y o f
board 2)
68
69
70
71
72
73
74
75
76
77
78
79
80
81
i f p l o t _ s e p a r a t e == 1 ;
endtime = 8 7 6 0 0 ;
time = [ 0 : 1 : endtime ] ;
R_diminished = zeros ( s i z e ( time ) ) ;
R _f u ll = zeros ( s i z e ( time ) ) ;
f o r i = [ 1 : 1 : endtime +1]
R_diminished ( i ) = (1−(1−exp(−Lambda_open∗ time ( i ) ) )
∗(1−exp(−Lambda_open∗ time ( i ) ) ) ) ;
R _f u ll ( i ) = exp(−Lambda_open∗ time ( i ) ) ∗exp(−
Lambda_open∗ time ( i ) ) ;
end
plot ( time /MTTF_open, R_full , ’ g ’ ) ;
plot ( time /MTTF_open, R_diminished , ’ r ’ ) ;
legend ( ’ R e l i a b i l i t y o f t h e o r i g i n a l system ’ , ’ R e l i a b i l i t y
o f t h e s e p a r a t e dc bus system − c o m p l e t e o p e r a t i o n ’ ,
’ R e l i a b i l i t y o f t h e s e p a r a t e dc bus system −
diminished operation ’ ) ;
end
82
%% F u l l s w i t c h b o a r d
84 %This s o l u t i o n works i f one o f open ups b o a r d s i s s t i l l
f u n c t i o n a l . This i s t h e same as t h e s e c u r e d dc bus . The
o n l y d i f f e r e n c e i s power r a t i n g : i n t h i s s i t u a t i o n e v e r y
o u t p u t o f t h e s w i t c h b o a r d can be p r o v i d e d w i t h power by
one open ups board . In t h e s e c u r e d case , t h i s i s not t r u e
: a l l power w i l l come from 1 open ups board .
83
85
i f p l o t _ t o t a l _ s w i t c h e d == 1 ;
87
endtime = 8 7 6 0 0 ;
86
111
88
time = [ 0 : 1 : endtime ] ;
R = zeros ( s i z e ( time ) ) ;
f o r i = [ 1 : 1 : endtime +1]
R( i ) = (1−(1−exp(−Lambda_open∗ time ( i ) ) ) ∗(1−exp(−
Lambda_open∗ time ( i ) ) ) ) ;
end
plot ( time /MTTF_open, R, ’ g ’ ) ;
legend ( ’ R e l i a b i l i t y o f t h e o r i g i n a l system ’ , ’ R e l i a b i l i t y
o f t h e s w i t c h b o a r d system ’ ) ;
89
90
91
92
93
94
95
end
112
Appendix E
Other Information
E.1
Contact information
Table E.1: Important contacts for this thesis
ABB - drives
ABB - motors
ABB - ordering
KU Leuven ELECTA lab
KU Leuven electrical workshop
KU Leuven high voltage
KU Leuven VGM
Siemens - drives
Siemens - PLCs
Vandecappelle NV - communication
Vandecappelle NV - sales
WEG - drives
WEG - sales
Koen Michiels
Robert Hambrouck
Freddy Demerre
Roland Reekmans
Geert Wolfs
Hendrik Cludts
Steven Janssens
Harm Leenders
Anneleen Sterckx
Patrick La Haye
Marc Vindevogel
Werner Joosens
CETmotoren
113
E.2. IP rating
E.2
IP rating
Table E.2: Meaning of the IP rating [19]
Level
Digit one: Solid particle protection
Safe Object size
Effective against
0
1
2
3
4
5
> 50 mm
> 12,5 mm
> 2,5 mm
> 1 mm
Dust protected
Level
No solid particle protection
Any large surface of the body
Fingers or similar objects
Tools, thick wires, etc.
Most wires, screws, etc.
Ingress of dust is not prevented but should cause
no harm; complete protection against contact
Dust tight
No ingress of dust complete protection against
contact
Digit two: Liquid ingress protection
Protected against
Effective against
0
1
2
3
4
Dripping water
Dripping water at 15◦
Spraying water
Splashing water
5
6
Water jets
Powerful water jets
7
8
Immersion up to 1 m
Immersion beyond 1 m
6
No liquid ingress protection
Vertically falling drops
3mm rainfall per minute
spray at any angle up to 60◦
50 liters for 5 minutes at 80-100kPa from any
direction
water projected by a nozzle from any direction
water projected in powerful jets from any direction
Immersion up to 1 m
Immersion beyond 1 m
114
E.3. The full Vandecappelle NV quote
E.3
The full Vandecappelle NV quote
Table E.3: The full Vandecappelle NV quote
Post aantal Omschrijving
Prijs
Eenheid
1
a
2 st
Gesloten kasten IP66 (incl. montageplaat)
Type EKS 12064 h = 1200 b = 600 d = 400
249,16 €-/stuk
b
1 st
Type EKS 12084 h = 1200 b = 800 d = 400
Totaal post 1
2
a
b
c
e
f
3
3
4
3
3
g
h
i
1 st
1 st
1 st
j
k
1 st
2 st
l
3 st
m
1 st
st
st
m
st
st
Toebehoren :
Handgreep type LSC 501
+ cilinder LSSI 521
DIN RAIL 2069s
Dichtingsset BG01 EKS
Deurarretering DSTP02
Ventilatie
kastventilator (225 x 225 mm) EF 250R5
+ filter EFA 250 300 R5
kastventilator EF 500R5
+ filter EFA 500-700 R5 291x291 mm
Kastthermostaat ETR 202 (koeling)
Signalisatie
Paneel led lamp d = 22,5 mm Type XB4-BVB3
24 VDC
Flitslicht rood type STR3 024 31 24 VDC
Totaal post 2
3
a
1 st
b
c
d
3 st
1 st
1 st
i
j
2m
2m
Kablering :
Hoofdschakelaar 32 A/4 -polig / rood-gele handgreep Type KG32B T204/01
Monofasig stopcontact met klapdeksel 104 OBL
Barenstel 04885 4-polig/40 A
Relais 32 A/ 4-polig / 1 open en gesloten hulpcontact Type LC1-40-BD
PVC open draadkanalen
Type LK4 600 60 60x60
Type LK4 600 40 60x40
Metalen gesloten kabelgoot
308,22 €-/stuk
806,54 €
23,61
15,72
3,82
13,93
5,94
€-/stuk
€-/stuk
€-/meter
€-/stuk
€-/stuk
84,64 €-/stuk
25,02 €-/stuk
134,43 €-/stuk
28,75
14,86
€-/stuk
€-/stuk
8,61
€-/stuk
108,30 €-/stuk
629,57 €
44,06
€-/stuk
2,36
€-/stuk
17,91 €-/stuk
136,41 €-/stuk
7,36
5,63
€-/meter
€-/meter
115
E.3. The full Vandecappelle NV quote
k
l
9m
10 m
m
n
1 st
1 st
o
p
q
25 st
5 st
10 st
Type KG 60 x 100 l = 3 m
deksel D100 l = 2 m
CE inbouwcontactdoos
Vrouw. CL 532/6
Mann. CG 532/6
Rijgklemmen 2,5-4 mm2
UK5N (grijs)
USLKG5 PE klemmen
CLIPFIX 35 eindsteunen
Totaal post 3
4
a
b
c
d
2
1
1
1
e
1 st
5
a
3
b
c
1
1
st
st
st
st
Beveiliging:
automaat 2-polig / 2 A A9F84202
automaat 2-polig / 10 A A9F89210
automaat 3-polig / 32 A A9F89432
Verliesstroom (aanbouw) 30 Ma/2-polig
A9V11225
Diff. Schakelaar type B 4-polig/40 A/300 mA
MERLIN GERIN ref 16753
Totaal post 4
Kabel:
100m CTMBN 5 G 4 met 1 CT 532/6h en 1 CC
532/6h
CT532/6h
CC532/6h
Totaal post 5
Totaal
6,96
5,16
€-/meter
€-/meter
9,12
12,03
€-/stuk
€-/stuk
0,87
2,85
0,41
406,93
€-/stuk
€-/stuk
€-/stuk
€
40,89
30,93
61,46
96,22
€-/stuk
€-/stuk
€-/stuk
€-/stuk
662,49 €-/stuk
932,88 €
355,00 €-/stuk
6,12
€-/stuk
7,77
€-/stuk
1078,89 €
3854,81 €
116
E.4. Used test equipment
E.4
Used test equipment
Table E.4: Test equipment used in testing the drives at the ‘labo grote machines’
of ESAT
Component
General equipment
Universal power analyzer
Current transformers
Thermometer
Decibel meter
For motor duty
Table 25
Powder brake
Eddy current brake
Torque read out
Torque flange
Rotational speed measurement
For generator duty
Driving motor
Torque measurement
Motor controller
number
Type
01.727
03.048.14
03.048.14
03.048.14
01.457.01
01.594.03
Voltech PM3000A
2PB15
2WB15
01.596.01
Peaktech 5110
Peaktech 5035
Fribourg Vibrometer sa
Fribourg Vibrometer sa
Keithley 20000 multimeter
Manner MF500
01.327
7.003
Siemens 16P9155
Herman Faust Wiegeapparate
ABB DCS400 //
117
E.5. Losses in the components
E.5
Losses in the components
On the next two figures the behavior of the losses in function of the load is shown. [28]
Figure E.1: Losses in the partial load range for Active Line Modules and Smart
Line Modules
Figure E.2: Losses in the partial load range for Motor Modules
118
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