A new member of the Sunny Family
Sunny Boy 4200TL Multi-String
Innovations for the success of PV
technology are the mission of
SMA. After the success of the
Sunny Boy 5000TL Multi-String
we provided a smaller innovation: The Sunny Boy 4200TL is a
new member of the Sunny Boy
family. It has two separate input
Strings and is designed for PV
plants with 5 kWpeak.
The Multi-String technology of
the Sunny Boy 4200TL is based
on an effective transformerless
circuit. It combines two separate
input strings and one common
Grid
inverter bridge within
one device.
Here the efficiency of
the Sunny Boy 4200TL
kicks in: The advantages
of the String technology
are combined with the
affordable price for this
system size. And the efficiency is remarkable (see
chart).
A separate MPP tracking for
the two connected Strings provides additional flexibility in
designing your plant and guarantees your yields. Naturally,
the 4200TL Multi-String is compatible with all the monitoring
concepts of the Sunny Boy family, is delivered in a stainless
enclosure and is suitable for outdoor installation.
Andreas Jeppe
Poster
Sunny Boy
Inside
Contents:
SB4200TL Multi-String . . . . . . . . . . . . . . . . . . . 1
Up-to-date: Yield Maximization . . . . . . . . . . 2
Optimal Design of a PV Plant (8) . . . . . . . . . . 3
Sunny Island Complete System . . . . . . . . . 4
Winner . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Efficiency is guaranteed . . . . . . . . . . . . . . . 5
Starting problems overcome . . . . . . . . . . . 7
Sunny Boys Deluxe . . . . . . . . . . . . . . . . . . 8
Up-to-date: Yield Maximization!
The energy yield (kWh/kWp) has
always been an important quality
criterion for a PV plant. But with
the introduction of the EEG law
(Renewable Energy Law in Germany) the amortization time
depends on the energy that can
be extracted from the PV cells. In
order to be on the profit side it is
not enough to select the components with the highest efficiency.
The plant efficiency
of different concepts
by comparison
Many details influence the yield in
the percent range and are a sign
for a good plant designer. With
some experience the promises of
several component manufacturers
can be integrated correctly and
unrealistic expectations of plant
operators can be avoided. These
categories comprise also two
important loss causes, that are
briefly explained in the following.
1. Mismatching
Mismatching means that not all the
PV modules of a generator are operated in the maximum power point
(MPP). The causes for this can be
minor differences in the fabrication
of the PV module, voltage drops
resulting from the DC wiring, different module temperatures. Losses
due to mismatching arise when
modules are all connected to one
big PV module array. They substantially increase with the number
of modules (typical values: 1…3%).
The String technology developed
by SMA and introduced onto the
market with the Sunny Boy inverters
reduce these losses to a minimum.
2
2. Partial load efficiency
PV inverters are designed for
powers that contribute the largest portion of energy to the
total yield. Thus, the maximum
efficiency should be in this range
(at 50…80% of the nominal
power). Below 10% of the nominal power, the Sunny Boys feed
a maximum of 90% of the PV
power into the grid. An adequate way to increase the so called partial load efficiency - at
least on the paper - is the masterslave operation. Many small
inverters are connected in parallel to a large PV generator
and activated according to the
current power. In periods of time
with lower irradiation, that
means low PV power, only a few
inverters are active, but in an
operation range with high efficiency.
More yield in theory…
The question is, if a noticeable
increase of the annual yield is
possible with this concept. A
simple consideration shows the
potential of this technology: The
European weighted efficiency
provides information about the
average efficiency of a PV inverter. Ideally, it can have at most
the value of the maximum efficiency. The difference between
these two values is normally only
1…1.5 % in case of good inverters. At the same time, it reflects
the upper limit for the increased
yield.
This increased yield of 1 % or 2 %
is only theoretic, because it can
only be achieved with the design
of a single large PV generator.
The resulting mismatching losses
are of the same degree and can
compensate the theoretical increased yield achieved.
before. Even in some cases, product names contain the introduced term master-slave although they do not use this concept. Other devices functioning
in the master-slave operation
have a more attractive name and
achieve an increased yield of an
astronomic value in advertising
brochures.
… and in practice:
Sunny Team ®
The only possibility to combine
the advantages of the String operation with those of the masterslave operation is the patented
plant concept Sunny Team ®.
Here a real increased yield of
1…2 % is achieved and has been
shown at a test plant in contrast
to the two individual technologies. However, the relative yield
increase can be larger when the
energy portion of weak irradiations is increased due to a module
arrangement that is not ideal.
Choose Sunny Team ® when you
want to achieve the best yield.
Do not be deceived by an utopian yield increase due to clever
calculations.
Werner Reitze,
Joachim Laschinski
You will find a detailed comparison of the
individual plant concepts in the article
"Mehr Ertrag durch Teamarbeit" ("More
yield due to teamwork") in the "Sonne,
Wind & Wärme" magazine 4/2003 which
is also available as offprint. You will find
details about "Sunny Team ®" in our leaflet
"Sunny Boy Extra" (issue 03/02). All information is available upon request from our
sales partner Rosendahl Inudstrievertretungen
in Krefeld, Germany
(phone +49 2151 4567890).
Despite of the doubtful result of
this idea, that is no new at all, the
master-slave operation now
seems to be more up to date than
November 2003
PV Plant Design PV Plant Design PV Plant Design PV Plant Design
Finding the Optimal Design
of a Utility Interactive PV Plant
Topics
1.
Inverter /
PV generator ratio
1.1 Power distribution
of the energy yield
1.2 Underdimensioning
of a PV inverter
1.3 The optimum design
1.4 Sunny Boys among themselves
2.
PV generator voltage
2.1 Lowest operating voltage
2.2 Highest operating voltage
2.3 MPP voltage
and efficiency
3 . Planning instruments
3.1 Excel table "GenAu"
3.2 EIntegration of
local insolation data
4.
Summary
5.
Sources
In addition, the high voltage is a
heavy load for the input circuit of the
inverter. A low (up to 10 % of the
maximum input voltage) overvoltage
at the input port does not result in a
functional deficiency of the inverter
but can cause a heating and thus an
early aging of some components, in
this case of the electrolytic capacitor.
Due to the generally higher ambient
temperature and more unfavourable
cooling of the electrolytic capacitor,
devices positioned in an air-conditioned interior react more sensitively to
overvoltages than inverters in outdoor installations.
RT
PA
8
Thus, too high input voltages will at
least result in yield losses but can
even damage the inverter. Such a
situation must be avoided by all
means. A PV plant in Central Europe
with an idle voltage of -10°C cell
temperature that is within the input
voltage range of the inverter has sufficient internal reserves to get over
extreme weather situations without
any damages.
Joachim Laschinski
To be continued in the next issue of Sunny Boy Info.
2.2 Highest operating voltage
Just like the lowest operating voltage
is linked with the highest temperature
of the solar cells, the highest operating voltage is observed with the
lowest temperature of the solar cells.
However, not only the MPP voltage
is to be considered but also the slightly higher open circuit voltage of the
PV generator (see figure 7, PV Plant
Design, Part 6).
November 2003
Fig. 1: The idle voltage of the PV generator is higher than the highest allowed input voltage
of the inverter
In contrast, overvoltages beyond this
range can result in a fast overheating
and a subsequent bursting of the
electrolytic capacitor or even a flashover and arc. Such an irreparable
damage of the inverter is only possible in case of an extremely bad
plant layout and/or inadvertent
series connection instead of a planned parallel connection of Strings.
SB-info23 :AE4403
Figure 1 illustrates the situation to be
considered when the idle voltage of
the PV generator exceeds the maximum input voltage of the inverter. Although the MPP is within the accepted operating range an inverter
ready for operation would not start
to operate. Because it would have to
start at too high input voltages to
achieve the accepted operating
point. Thus, it would overload its
power semiconductors. Only when
the idle voltage of the PV generator
decreases (by heating the cells) and
reaches the accepted operating
range the inverter starts the grid-feeding mode. Such a situation results in
a decreased yield of the PV plant.
Imprint
Published by:
SMA Regelsysteme GmbH
Hannoversche Straße 1 - 5
34266 Niestetal
www.SMA.de
Edited by:
SMA Regelsysteme GmbH
and
Rosendahl Industrievertretungen
Adolf-Dembach-Straße 1
47829 Krefeld
Phone +49 2151 4567890
Fax +49 2151 4567899
e-Mail:
info@Rosendahl-Energietechnik.de
www.Rosendahl-Energietechnik.de
3
A Complete System The Sunny Island
System Kit!
New at SMA - Kit solutions
for the design of island grids
Whether you need a utility backup plant or want to establish an
off-grid electricity supply - SMA
has the exact solution for you offthe shelf. Reliable decentral
energy supply systems can easily
be designed and maintained by
means of our modular AC supply
units. The necessary components
(PV-plant, wind and water generators, battery bank etc.) can be
integrated in form of modules
and allow numerous variation
possibilities with our standard
components, such as Sunny
Island, Sunny Boy and Sunny
Boy Control. This results in an
energy supply system that exactly
fits your individual requirements.
Since Spring 2003, we offer for
the first time complete packages
in the field of island systems. Finally you can purchase all components you
require for your project in one
kit. System technology from one
hand assuring a simple installation and perfect performance
due to selected components.
We assembled four basic packages with different upgrade possibilities in order to support you
with simple and reliable planning and design of off-grid supply
systems. Each package has a
modular design and contains a
battery bank and a generator,
where applicable. The components are tested and selected for
a reliable and long-lasting use.
An installation guide with all
schematics and wiring instructions and the factory preset configuration results in a fast "plug &
play" installation on your site.
basic packages can be upgraded, remotely monitored, all depending on your needs. This
makes your system a reliable
electricity supply for the future.
Based on our experience resulting from many years right on the
field of decentral energy supply,
we can offer you with our systems an easy entry into the electricity supply for off-grid applications with durable solutions of
convincing technology providing
a multitude of application possibilities.
Michael Wollny
One important advantage of the
modular island grid is that the
Always a profit - "SMA Upgrade"!
Our e-mail newsletter "SMA
Upgrade" is available since
January. The response to our
campaign for the start of the
"SMA Upgrade" was enormous thank you very much!
Would you also like to get our
"SMA Upgrade"? Please contact
the team of the Rosendahl Energietechnik (contact: Mrs. Pereira,
phone +49 (0) 2151 45678 93
or via e-mail: pereira@RosendahlEnergietechnik.de
Rosendahl Industrievertretungen
4
November 2003
Performance is guaranteed!
We can prove this.
In addition to the price, the realized efficiency is very important for the selection of an inverter.
The energy yield of the solar cells that are still comparatively expensive, shall be preferably
fed into the grid completely. The losses within the grid-feeding unit shall be as low and the
efficiency shall be as high as possible.
Thus, some inverter manufacturer tend to promise more in advertising texts than they can
actually prove by measurements. Here we would like to provide our customers with some
information that can help them to conduct their own assessments.
Basically, two different inverter
concepts are available:
●
●
Inverters with transformers allowing an electrical separation of
PV and grid side.
Two options are distinguished:
the low voltage (low voltage =
50 Hz) and the high voltage
transformer
Transformerless inverters
The concept of the
low voltage transformer
In case of devices functioning
with the low voltage concept,
normally a toroidal core transformer is responsible for the voltage
regulation. The efficiency directly depends on the size and the
weight of the transformer, i. e. a
low loss transformer is large and
heavy. But what seems to be
disadvantegeous at first glance,
is absolutely advantageous in
practical operation. However, it
is not the weight that is important
during operation, but the best
possible efficiency. The efficiency of the Sunny Boy 3000, for
example, is very good with 95%.
Block circuit diagram of an inverter with
low frequency transformer
Block circuit diagram of an inverter with
high frequency transformer
weight transformer. However,
additional electronic transformer
stages reducing the efficiency
especially in the important partial
load range are necessary. Thus,
SMA did not follow up this technology for PV applications after
experiences with the PV inverter
PV-WR 1800/5000 (1990 1994) but decided in favor of the
low voltage transformer concept.
efficiencies, because increased
core and switching losses have to
be compensated. Price advantages of the smaller transformer
are more than compensated due
to the increased expense for an
additional transformer stage and
filter. High number of active and
passive components, highest
complexity.
Advantages: Low weight, small
size.
Disadvantages: Low partial load
Advantages: Extremely robust,
electrical separation from grid.
Disadvantages: High weight,
large volume.
The concept of the
high voltage transformer
The goal of the high voltage concept is to have a small and light-
November 2003
The graph shows enormous differences in efficiency of the two concepts in particular in the partial
load range
5
The transformerless concept
provides the best efficiency profile, as here the maximum efficiency is the highest. In the range
of partial load, the values are
also higher than in case of other
concepts, since there are no losses due to the magnetization of
the transformer.
An excellent "European
weighted efficiency" (Euro
eta) arises, considering in
particular the insulation conditions in Central Europe
with high proportions in the
range of partial load.
However, a fixed transformation ratio of input and output
voltage results from a transformerless concept. There is almost
no flexibility with respect to use
and connection of different types
of PV modules.
order to realize a wide input voltage range. This transformer
stage just slightly reduces the
maximum efficiency in case of
low generator voltages.
The dependency of the efficiency
profile of the inverter from the
input voltage should be consider-
Block circuit diagram of
a transformerless inverter
ed when designing the PV generator. The efficiency of the SB
2100TL is highest at an MPP voltage of approx. 400 volt assuring the best yields.
Thus, SMA implements an electronic step-up converter in case
of transformerless Sunny Boys in
Our offer:
We do not only promise but guarantee high
efficiencies! In case that downward deviations of more than 1 % (considering the precision of measurement) from our efficiencies
specified under nominal conditions are detected during retests, we bear the costs for
this measurement*.
*) measurement in qualified institutes
6
Comparing the efficiencies of
transformerless inverters of different manufacturers, it should be
considered if a step-up converter
(DC/DC converter) is integrated.
This is the only way how a maximum of interconnection possibilities can be guaranteed.
Although the competitive
device (yellow efficiency
profile in the chart below)
does not have an integrated
step-up converter, the measured values clearly fall
below the technically possible values. This is only an
example for the fact that the
technology of transformerless inverters from SMA
(e. g. Sunny Boy 2100TL) with
integrated step-up converter
even tops devices that could
have a much higher efficiency
due to the absences of this adjustment stage.
The Multi-String concept
The Sunny Boy reaches a higher efficiency profile, even with an integrated
step-up converter, than the comparative
device without integrated step-up converter
Advantages: Highest efficiencies.
Disadvantages: Electronic stepup converter is necessary for the
connection of low input voltages.
The Multi-String concept is another reasonable possibility to increase the system efficiency of a
PV plant especially in case of higher performances. The Strings
have their own MPP tracker with
an extremely wide input voltage
range. Thus, highest flexibility
with a maximum of effectiveness
is possible. The energy collected
by the single MPP trackers is
supplied to a common internal
transformer stage and fed into
the grid. In this case, concepts
with transformer as well as without transformer are used. The
convincing concept of the SMA
Multi-String inverters is shown in
the chart on the next page.
Conclusion
Basically, the fact that the technically possible efficiencies are
only obtained when the PV generators are optimally designed
and/or interconnected applies
to all types of inverters.
The MPP voltage of the generator should be the same as the vol-
November 2003
tage of the inverter at which the
inverter reaches its peak
efficiency.
The efforts of our research and
development activities to optimize the efficiencies of inverters
of the Sunny Boy family were
profitable and resulted in outputs
that can hardly be surpassed.
The realized efficiencies of the
Sunny Boys within the respective
inverter concepts are better compared to the standard competitive products available!*
Peter Simon,
Reiner H. Rosendahl
The Multi-String concept within the competitive device
does not yet result in higher efficiency profiles, as the
used topology is also important
*) Our measurement equipment used:
Precision measurement device LEM Norma D 6000
Sunny Boy 5000TL Multi-String:
Initial difficulties overcome
First of all, we would like to express our regret for some problems occurred during operation of several Sunny Boy
5000TL Multi-Strings and would
like to formally apologize for
the resulting inconveniences for
you.
However, we would like to use
the opportunity to inform you
about the technical background
of these problems. Despite of our
comprehensive quality management and a continuous error tracing, some failures can occur
only after a longer operating
time in combination with different
PV generators. Thus, these failures cannot be detected by our
comprehensive tests during or at
the end of the development
and/or manufacturing. This was
the case for some Sunny Boy
5000TL Multi-String type inverters.
This inverter, introduced onto the
market at the end of the last year,
is a high innovative product with
November 2003
a new circuit topology and a
high increase of complexity in
respect of control algorithms and
device internal communication
structures.
After a field test during the last
year, we were convinced that we
can provide a device complying
with the high quality standards of
SMA. However, we had to realize that this was not the case in
all plant combinations and configurations. We really regret the
resulting inconveniencies for you.
We tried to keep them as little as
possible.
The firmware change accomplished and extensively tested at
our plant during the suspension
of deliveries has now proved in
the field. Thus, we are optimistic
that our quality requirements can
now be reached and you and
your customers will realize peak
yields with this innovative device.
In conclusion, we would like to
thank you for your understanding
and cooperation. A good partnership proves in particular in
times of difficulties. We thank
you very much for this.
Marko Werner
Divisional Director Solar Technology
The problems detected to some
extend in your plants after the
introduction of the device never
occurred in the conducted field
test. Now we use these problematic field and plant experiences
to optimise the Sunny Boy
5000TL as to its device behavior.
Thus, a reliable operating behavior is also assured in the previously problematic plant combinations.
7
For example
Sunny Boys
Deluxe
The workshop and exhibition
building of Bauer Energietechnik
suited at the Northeastern outskirts of Ingolstadt shows an
architecturally attractive and
manifold use of solar power.
The exhibition hall has a southwardly inclined pent roof that is
bended from East to West and
has a surface of 120 m² equipped with an integrated PV plant.
The semitransparent PV modules
functioning as so called thermal
insulating façade elements are
building shell, sun shield and PV
panel at the same time. 72 PV
panels are horizontally connected in Strings and to four Sunny
Boy 2000 allowing a possibly
consistent power generation
during the day.
The East and West side of the
exhibition room have steel /
glass facades. Three elements
with transparent perforated PV
8
cells are integrated into the glazing of a part of these façades.
These elements are used to generate additional solar power as
well as for clouding and as
blinds of the stairway. A Sunny
Boy 700 is used to feed the produced power into the grid.
The total of 75 modules are monitored by the powerline modems integrated into the inverters. The data logger Sunny Boy
Control Plus records the data
from the PV plant, the energy
consumption of the building and
the insulation and temperature
data. An automatic nominal/
actual value comparison is possible by means of special software. All electrical consumers
are controlled if required or
upon request (EIB).
Due to an underground channel
around the building supplying
the ventilation system with pre-
cooled air in the summer and preheated air in the winter, additional energy is saved.
Christian Luttmann
Description of the plant:
Total power: 10.04 kWp
Number of modules: 75
Manufacturer or the modules:
Flabeg Solar International GmbH
Number of modules: 75
Module power: 125 Wp and/or 346 Wp
Inverter: 1 Sunny Boy SWR 700,
4 Sunny Boys SWR 2000
Visualization:
Sunny Boy Control Plus via Powerline
Total costs of the plant:
Approximately 100,000 Euro
Expected energy output:
8,000 kWh / year
November 2003