Novel PM generators for large
wind turbines
by Alexey Matveev
Wind Power R&D seminar - Deep sea offshore wind power, 20-21 January 2011, Trondheim, Norway
Contents
• Drive train configurations
• State-of-the-art PMG-based solutions
• Integration: the path to win for direct drive
• SmartMotor in wind
18.01.2011
2
The general drive train scheme
GB
B
T
C
G
P
Grid
Nacelle and tower
GB – gearbox
B – brake
G – generator
C – converter
T – transformer
P - protection
18.01.2011
3
Basic drive train solutions
Configuration 3: direct SG with wound rotor
Configuration 1: gear + double-fed IG
Configuration 4: gear + PMSG
Configuration 2: gear + IG
Configuration 5: DD PMSG
18.01.2011
4
Efficiency of different drive trains
• Components included: gearbox, generator, converter, transformer
–
Direct driven PM generator solution gives the best efficiency at speeds below rated
100,00 %
LS – low speed
MS – medium speed
HS – high speed
95,00 %
90,00 %
PMSG – permanent magnet
synchronous generator
DFIG – doubly-fed induction
generator
EESG – electrically excited
synchronous generator
SCIG – squirel-cage
induction generator
Efficiency
85,00 %
80,00 %
75,00 %
MS_PMSG
HS_PMSG
HS_DFIG
MS_EESG
HS_SCIG
HS_EESG
LS_PMSG
LS_EESG
70,00 %
Analysis performed in
cooperation with Zhaoqiang
Zhang, NTNU (supervisor
Prof. Robert Nilssen)
65,00 %
60,00 %
3
5
7
9
11
13
Wind Speed (rpm)
18.01.2011
5
15
Direct drive vs geared solution
• Direct drive is larger and heavier, but
• it doesn’t suffer gearbox-related problems
generator
turbine
gear
Source: NTNU
18.01.2011
6
High-torque generator for direct drive
• High-torque generator for direct drive is large. This is basically
the only drawback of direct drive solution
PM generator from Siemens. 3 MW, 17 rpm
18.01.2011
7
Some conclusions
• Drive trains with PM generators have the best efficiency
– Especially without gear (direct drive) and 1-stage gear
• However, there are other characteristics to take into account:
–
–
–
–
–
–
–
Weight
Cost
Power factor
Lifetime
Reliability
Manufacturability
...
Efficiency
Tan. tension
cos_fi
Design 2
Design 3
Design 4
1/Length
P/kg
T/kg
• Design means finding a trade-off between various criteria
18.01.2011
Design 1
8
Design 5
...next part
• Drive train configurations
• State-of-the-art PMG-based solutions
• Integration: the path to win for direct drive
• SmartMotor in wind
18.01.2011
9
Available solutions with PMG
Low-speed PMG (DD)
Medium-speed PMG (1-s.g.)
High-speed PMG (3-s.g.)
18.01.2011
10
Products of ABB and TheSwitch
• Low-speed, medium-speed and high-speed generators
<1 MW
<2000 rpm
18.01.2011
<3.3 MW
<300 rpm
11
<4.25 MW
<20 rpm
Commercial power electronics
• Examples of medium-voltage (ABB) and low-voltage (TheSwitch)
converters
ABB
18.01.2011
TheSwitch
12
Is it end of the story?
• Big companies have products and even complete packages up
to approximately 5-7 MW. Is it end of the development?
NO!!!
• New concepts under investigation, for example:
– Magnetic gears and Pseudo-direct drive
– Superconducting machines
• There are problems when going to powers higher then 5-7
MW. These are to be solved!
18.01.2011
13
Examples of new concepts
• Magnetic gears, pseudo-direct drive (PDD), superconducting
machines
• The concepts have not been proven yet for high-power WEC
Magnetic gears
PDD
Direct drive using HTS superconductors
Magnomatics
18.01.2011
Converteam/Zenergy
14
Technology frontier for PM generators
• State-of-the-art in generator weight (expressed via power and
torque densities, each point corresponds to one generator design)
450,00
<1.5 MW
1.5-2 MW
ABB 2 MW
3-stage gear
400,00
2-3 MW
3-4 MW
Power Density (W/kg)
350,00
>4 MW
Superconducting
300,00
Some new designs
250,00
200,00
150,00
Area of state-ofthe-art designs
100,00
TheSwitch 3,3
MW geared
TheSwitch
4,25 MW DD
Siemens 3,6
MW DD
Analysis performed in
cooperation with Zhaoqiang
Zhang, NTNU (supervisor
Prof. Robert Nilssen)
50,00
0,00
1,00
10,00
100,00
Torque Density (Nm/kg)
18.01.2011
15
Active parts, cooling and carrying structure
•
Active parts make 30-40% of total weight
Cooling system defines size of active parts, it
may take considerable space
Carrying structure is usually massive
<30000 kg
~6000
•
•
TheSwitch
~1000-1500
16 16
When going for higher powers...
• Weight of carrying structure grows disproportionally!
Source: TU Delft
Enercon
18.01.2011
17
...next part
• Drive train configurations
• State of the art PMG-based solutions
• Integration: the path to win for direct drive
• SmartMotor in wind
18.01.2011
18
Integration strategies
• For drive trains with gearboxes: integrate generator with
gearbox (see examples below)
• For direct drive: integrate generator with the turbine!
(examples will follow)
TheSwitch
18.01.2011
ABB
Magnomatics
19
Direct-driven generator in the nacelle
• Just a few of numerous patented designs
18.01.2011
20
Direct-driven generator in the nacelle
• Popular concept: generator between blades and tower
Vensys
MTorres
Mervento
Northwind
18.01.2011
21
Direct-driven generator in the nacelle
• Integration variants
Source: NREL
18.01.2011
22
Direct-driven generator outside the nacelle
• No shaft
• Single bearing common for generator and blades
Outer rotor
Bearing
Inner stator
Emergia
18.01.2011
23
Direct-driven generator outside the nacelle
• Different approaches to weight reduction
Concept: light carrying structure
of the generator
18.01.2011
Concept: integration of generator
with blades
24
Key to success for generator supplier
• Work in close contact with the turbine designers
• Provide best active parts
–
–
–
–
–
–
–
–
18.01.2011
Lightest
Most compact
Giving high efficient energy conversion
Segmented
Easy to integrate
Cheap in production
With low cogging
Medium- and low-voltage
25
...next part
• Drive train configurations
• State of the art PMG-based solutions
• Integration: the path to win for direct drive
• SmartMotor in wind
18.01.2011
26
What is SmartMotor
• Established in 1996 in Trondheim, Norway
• One of the largest R&D groups in the world with focus on PM technology
18.01.2011
27
Reference projects offshore
• Low-voltage and medium-voltage machines of MW-class
0.8 MW propulsion system
for Rolls-Royce Marine (in
operation)
1.1 MW tidal turbine of Atlantis
Resource Corporation (delivered)
18.01.2011
28
10 MW offshore wind turbine of
SWAY (under construction)
The technologies we believe in
• PM machines with concentrated winding and ironless machines
• Ideal for high-torque applications like wind turbines with direct drive
NTNU
29
Our technologies
• Concentrated winding technology is advantageous compared to
distributed winding in high-torque applications due to
– higher slot fill factor and consequently better cooling of the copper
 Pre-shaping of the coil
 No insulation is needed between different phases
– segmentation with distributed winding leads to half-empty slots (10% loss
in total slot filling), while with concentrated winding all slots are filled
– low cogging
 Competitors achieve this by shaping magnets
 SmartMotor apply patented slot/pole combinations
• Ironless technology is advantageous for machines with large
diameter
– There is no attracting force between rotors and stator
– The structure is not sensitive to relative displacement of rotors and stator
18.01.2011
30
Our R&D directions
• Shift PMG technology frontier by introducing new concepts
• Find new integration solutions together with wind turbine manufacturers
200
Power per weight [W/kg]
0
1
2
3
State-of-the-art
New active parts (NAP)
NAP+mech. integration
MAG-concept
100
Siemens 3.0 MW
0
1
Siemens
2
3.6 MW
TheSwitch
Enercon 4.5 MW
4.2 MW
Vensys 1.5 MW
0
0
3
30
60
Torque per weight [Nm/kg]
18.01.2011
31
Our R&D directions
• Novel transformer-less concepts
• ABB have developed concepts with direct high-voltage DC outputs based
on use of machines with high-voltage insulation
• SmartMotor have developed similar concept where machine with lowvoltage insulation can be used (which means considerably more compact
and cheap machine)
ABB concepts
18.01.2011
32
...the end)
Thank you!
Contact information: alexey@smartmotor.no, www.smartmotor.no
18.01.2011
33