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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
18.01.2011 2
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 3
The general drive train scheme
G
Nacelle and tower
Grid
C TP
BGB
GB – gearboxB – brakeG – generatorC – converterT – transformerP - protection
18.01.2011 4
Basic drive train solutions
Configuration 1: gear + double-fed IG
Configuration 2: gear + IG
Configuration 4: gear + PMSG
Configuration 3: direct SG with wound rotor
Configuration 5: DD PMSG
Efficiency of different drive trains
• Components included: gearbox, generator, converter, transformer– Direct driven PM generator solution gives the best efficiency at speeds below rated
18.01.2011 5
Analysis performed in cooperation with Zhaoqiang Zhang, NTNU (supervisor Prof. Robert Nilssen)
LS – low speedMS – medium speedHS – high speed
PMSG – permanent magnet synchronous generatorDFIG – doubly-fed induction generatorEESG – electrically excited synchronous generatorSCIG – squirel-cage induction generator
60,00 %
65,00 %
70,00 %
75,00 %
80,00 %
85,00 %
90,00 %
95,00 %
100,00 %
3 5 7 9 11 13 15
MS_PMSG HS_PMSG
HS_DFIG MS_EESG
HS_SCIG HS_EESG
LS_PMSG LS_EESG
Wind Speed (rpm)
Eff
icie
ncy
• Direct drive is larger and heavier, but
• it doesn’t suffer gearbox-related problems
18.01.2011 6
Direct drive vs geared solution
Source: NTNU
turbine
gear
generator
• High-torque generator for direct drive is large. This is basically the only drawback of direct drive solution
18.01.2011 7
High-torque generator for direct drive
PM generator from Siemens. 3 MW, 17 rpm
• 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– ...
• Design means finding a trade-off between various criteria
18.01.2011 8
Some conclusions
Efficiency
cos_fi
P/kg
T/kg
1/Length
Tan. tensionDesign 1
Design 2
Design 3
Design 4
Design 5
18.01.2011 9
...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 10
Available solutions with PMG
Low-speed PMG (DD) Medium-speed PMG (1-s.g.)
High-speed PMG (3-s.g.)
• Low-speed, medium-speed and high-speed generators
18.01.2011 11
Products of ABB and TheSwitch
<3.3 MW <300 rpm
<4.25 MW <20 rpm
<1 MW <2000 rpm
• Examples of medium-voltage (ABB) and low-voltage (TheSwitch) converters
18.01.2011 12
Commercial power electronics
ABB TheSwitch
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
• Magnetic gears, pseudo-direct drive (PDD), superconducting machines
• The concepts have not been proven yet for high-power WEC
18.01.2011 14
Examples of new concepts
Magnomatics Converteam/Zenergy
PDDMagnetic gears Direct drive using HTS superconductors
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)
18.01.2011 15
0,00
50,00
100,00
150,00
200,00
250,00
300,00
350,00
400,00
450,00
1,00 10,00 100,00
<1.5 MW
1.5-2 MW
2-3 MW
3-4 MW
>4 MW
Superconducting
Some new designs
Po
wer
Den
sity
(W
/kg)
Torque Density (Nm/kg)
Area of state-of-the-art designs
TheSwitch 4,25 MW DDSiemens 3,6 MW DD
TheSwitch 3,3 MW geared
ABB 2 MW 3-stage gear
Analysis performed in cooperation with Zhaoqiang Zhang, NTNU (supervisor Prof. Robert Nilssen)
• 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
16 16
~60
00
~1000-1500
<30000 kg
Active parts, cooling and carrying structure
TheSwitch
When going for higher powers...
• Weight of carrying structure grows disproportionally!
18.01.2011 17
Source: TU Delft
Enercon
• 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
...next part
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)
18.01.2011 19
TheSwitch ABB Magnomatics
18.01.2011 20
Direct-driven generator in the nacelle
• Just a few of numerous patented designs
• Popular concept: generator between blades and tower
18.01.2011 21
Direct-driven generator in the nacelle
MTorres
Northwind Mervento
Vensys
• Integration variants
18.01.2011 22
Direct-driven generator in the nacelle
Source: NREL
18.01.2011 23
Direct-driven generator outside the nacelle
Bearing
Outer rotor
Inner stator
Emergia
• No shaft• Single bearing common for generator and blades
• Different approaches to weight reduction
18.01.2011 24
Direct-driven generator outside the nacelle
Concept: light carrying structure of the generator
Concept: integration of generator with blades
Key to success for generator supplier
• Work in close contact with the turbine designers
• Provide best active parts– Lightest
– Most compact
– Giving high efficient energy conversion
– Segmented
– Easy to integrate
– Cheap in production
– With low cogging
– Medium- and low-voltage
18.01.2011 25
18.01.2011 26
...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 27
What is SmartMotor
• Established in 1996 in Trondheim, Norway
• One of the largest R&D groups in the world with focus on PM technology
Reference projects offshore
18.01.2011 28
• Low-voltage and medium-voltage machines of MW-class
1.1 MW tidal turbine of Atlantis Resource Corporation (delivered)
0.8 MW propulsion system for Rolls-Royce Marine (in operation)
10 MW offshore wind turbine of SWAY (under construction)
29
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
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
18.01.2011 31
• Shift PMG technology frontier by introducing new concepts
• Find new integration solutions together with wind turbine manufacturers
0
100
200
0 30 60
Pow
er p
er w
eigh
t [W
/kg]
Torque per weight [Nm/kg]
Enercon 4.5 MW
Siemens 3.6 MW
TheSwitch 4.2 MW
Siemens 3.0 MW
Vensys 1.5 MW
0
32
1
0
1
2
3
State-of-the-art
New active parts (NAP)
NAP+mech. integration
MAG-concept
Our R&D directions
18.01.2011 32
• 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 low-
voltage insulation can be used (which means considerably more compact and cheap machine)
ABB concepts
18.01.2011 33
...the end)
Thank you!
Contact information: alexey@smartmotor.no, www.smartmotor.no
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