Possible solutions to overcome drawbacks of d irect-drive generators for large wind turbines
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Transcript of Possible solutions to overcome drawbacks of d irect-drive generators for large wind turbines
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EECElectrical Energy Conversion
18 March 2009
Possible solutions to overcome drawbacks of direct-drive
generators for large wind turbinesDeok-je Bang , Henk Polinder ,
Ghanshyam Shrestha , Jan Abraham Ferreira
Electrical Energy Conversion, DUWINDDelft University of Technology
The Netherlands
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Increasing Wind Turbine power,
Direct-drive generator is large &
heavy.
Hence, it is expensive.
Background
mTP
For large direct-drive generators,
New configuration with high force density
and less material is required.
Hence, the cost reduction is achieved.
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Objective
• Find solutions of large direct-drive generators
Electromagnetic material
Structural material
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Contents
1. Promising solutions for large direct-drive
2. Challenges of large direct-drive
3. Rough design of new direct-drive PM
generators
4. Prototype (downscaled)
5. Summary
6. Further researches
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1. Promising solutions for large direct-drive (Source: Bang et al. 2008)
A.Active part• Permanent magnet synchronous generator
(PMSG)
B. Inactive part• Ring shaped construction of which air gap is
maintained by the bearingless drive
C. Practical issues• Modular construction for easy production,
handling and maintenance
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2. Challenges of large direct-driveA. Minimize inactive material
(1) New ring shaped construction
U-phase
V-phase
W-phase
U-phase
V-phase
W-phase
RotorU-phase
V-phase
W-phase
W-phase
V-phase
U-phase
Stator
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(2) New bearingless drive
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(1) Buoyant rotating partin order to
• Support heavy structure easily• Reduce structural material for supporting• Give flexibility in supporting and guiding heavy structure
B. New supporting and guiding concept
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(2) Hydrostatic bearingin order to
• Prevent the touchdown of rotor on stator• Maintain the air gap when the bearingless drive is in failure• Reduce a peak power consumption of the bearingless drive
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A
A’
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3. Rough design of new direct-drive PM generators: 5 & 10 MW
Turbine specification
Power 5 MW 10 MW
Speed 12.1 rpm
8.6 rpm
Rotor diameter 126 m 178 m
Rated wind speed 12 m/s 12 m/sGenerator
Air gap diameter 6.3 m 8.88 m
Air gap length 6.3 mm 8.88 mm
Force density 40 kN/m2
40 kN/m2
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A. Active mass
5 MW 10 MW
Copper 8.0 ton15.1 ton
Stator iron
21.8 ton
42.7 ton
Rotor iron
10.1 ton
20.9 ton
PM 3.2 ton 8.9 ton
Total 43.1 ton
87.6 ton
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B. Inactive mass
Assumption:• Max. normal pressure acting on rotor & stator is about 325 [kN/m2]
• Deflection < 10% of g• Deflection of stationary part is neglected
• th and tb of stationary part are the same with rotating part’s
for the deflection modelling of rotating part
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5 MW 10 MW
Rotor part 9 ton 62.4 ton
Stator part 10.6 ton 69.9 ton
Fluid (water)
13.4 ton 40.8 ton
Total 33 ton 173.1 ton
Modeling of rotor deflection:
Mass estimation:
IE
lwg h
384
505.0
4
max
b
b
AE
wlg
4
05.0max
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C. Total mass estimation
• Concept-1: EESG DD
(Enercon concept, m/T=66.5 kg/kNm at 4.5
MW)
• Concept-2: PMSG DD
(Zephyros concept, m/T=46.4 kg/kNm at 1.5
MW)
• Concept-3: PMSG DD
(Theoretical design, m/T=25 kg/kNm at 2, 3 &
5 MW)
• Concept-4: PMSG DD
(NewGen concept, m/T=18.4 kg/kNm at 4 MW)
• Concept-5: DFIG 3G
(DFIG concept, m/T=17.4 kg/kNm at 3.5(4)
MW)
Assumption: m/T of each concept is constant in
scaling up.
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5 MW 10 MW
Concept-1 262 ton 738.4 ton
Concept-2 183 ton 515.2 ton
Concept-3 98.7 ton 277.6 ton
New concept
76.1 ton
260.7 ton
Concept-4 72.6 ton 204.3 ton
Concept-5 68.7 ton 193.2 ton
In the rough design, general steel structure was used for inactive part construction. Therefore it is expected that the inactive mass can be reduced further by structural optimization.
• Generator mass comparison of different
concepts
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4. Prototype (downscaled): Sponsored by Wintech in Korea
Rotor
StatorRollers
• Modular construction (machine type: TFPM machine)
• Ring shaped construction
3ph_
1set
StatorRotor
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Power analyzer
Torque sensor
Rotor
Stator
Rollers
Gearbox
Driving Motor
Motor driving unit
Power analyzer
Torque sensor
Rotor
Stator
Rollers
Gearbox
Driving Motor
Motor driving unit
Driving motor
3ph AC machine
- Pn: 14.3 kW
- Nn: 2600 rpm
- Tn: 52.7 Nm
Pulley & Belt
- DPulley_1=6 in - DPulley_2=12 in
Gearbox 43:1 gear ratio
Pulley & Belt
• Experimental setup
Experimental analysis is going on.
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5. Summary• New direct-drive concepts have been proposed
with
- New bearingless drive concept
- New guiding/supporting concepts
• Rough design of new 5 & 10 MW direct-drive PM generators have been done
• Downscaled prototype has been built
- Structure: Ring shaped, doubled-sided AF machine
- Machine type: (TF)PM machine
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?
6. Further researches• Electromagnetic optimization• Detailed design on the new direct-drive concept• Structural mass minimization• Find sealing solution
Steel Al. profile
?
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Thanks for your attention !
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Back up slides
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Promising solutions for large direct-drive (Source: Bang et al. 2008)
A. Active part• Permanent magnet
synchronous generator (PMSG)
B. Inactive part• Ring shaped construction of
which air gap is maintained by the bearingless drive
C. Practical issues• Modular construction for easy
production, handling and maintenance
PM
Core
Winding
Secondary part
Primary part
Core
Source: Dubois (2004), Ph.D. Dissertation
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Strength of PM machine
• high energy yield and light weight
• no additional power supply for the
field excitation
• improvement in the efficiency
• higher reliability without slip rings
• higher power/weight ratio
compared to EE machines
Direct-drive permanent magnet synchronous generator (PMSG DD)
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Inactive part (proposed in 2008)
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Conventional bearingless drive
Concept with complicated winding and control
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New bearingless drive