dr. longya xu the ohio state university april, 2010
TRANSCRIPT
2MW PM Machine Design for Direct–Driven Wind Turbine
Generator Application
Dr. Longya XuThe Ohio State University
April, 2010
Contents1. Introduction Major Wind Power System Configurations Challenges to Remain in Power Grid Why PM Direct-Driven WTG Getting Popular
2. Initial Design and Performance Analysis
Specifications and Sizing Stator and Rotor Design Performance Evaluation
3. Conclusions
1.2 Major Wind Power Generation System Configurations
Example: Windformer (ABB)
Capacity Trajectory of Single Unit
Off-Shore Wind Farm Based on HVDC
Multi Units connected in series and power transmitted through HVDC
Specifications and Sizing
V Rated(V, rms) 690 Frequency 5~11Hz
I Rated(A, rms) 1700 Speed 10~22 rpm
KW Rated 2,000 Torque (peak) 850kNm
The reason for low speed at:10~22 rpm
Tip Speed of Wind Blades: vtip = 115 meters/sec.
The reason for low Frequency at:5~11 hz
Sizing Equations
LDT rre2
Consider the electrical and magnetic loadings are relatively constant, we have a traditional sizing equation:
where subscript “r” indicates rotor related variables.
(1)
In (1) the electrical loading refers the current along the air-gap in the unit of Ampere per Meter (A/M).The magnetic loading refers the magnetic flux density passing through air-gap in the unit of Tesla.
Sizing Equation Alternative
LDTe300
where subscript “o” indicates the stator related variables and a coefficient proportion to the current density and magnetic flux density. Here current density is in the unit of Ampere per Square Meter and magnetic flux density in Tesla.
0
0
(2)
0 LD30
is also closely Do/Dr related and at certain value of Do/Dr, is maximized, or minimized.
Combining (1) and (2), we have two new sizing equations, one in terms of stator OD
LDTe5.2
0'0
LDT rre5.2'
(3)
(4)
another in terms of rotor OD
In sizing an electric machine, the new equations take many variables into
consideration: electrical loading, magnetic loading, Do/Dr ratio, and slot current density.
Stator OD 3820mm Pole # 60
Stator ID 3500mm Slot # 288
Stack L 1300mm Air-gap 6mm
Sizing Results
21x120
R1750
R1910
Stack l ength: 1300Ai rgap: 6
Stator Slot Shape and Dimensions
Stator current density at 2 MW
17.2
12
782
4
0.77(A/mm2)
Considerations on Slot Numbers
360 Slots: Integer Number/Pole/Phase
288 Slots: Fractional Number/Pole/Phase
Pros: reduced slot harmonics and cogging torque
Cons: reduced fundamentals and less effective in EM conversion
Pros: increased fundamentals and more effective EM energy conversion
Cons: more slot harmonics and increased cogging torque possibility
Considerations on Inner or Outer Rotor
Inner Rotor
Outer Rotor
Pros: traditional mechanical structure to design and manufacture
Cons: extra effort to install permanent magnets
Pros: easy installation of permanent magnets and better utilization of space
Cons: non-traditional mechanical structure and extra effort for bearing installation
Estimation of Losses and Efficiency
Estimated Copper Losses
Pcu= 3I2R = 2.7~3 kw
Assume equal amount of iron and other losses
Effi. = 97%
Expected energy efficiency
PFe+other = ~3 kw
FEM Comparison Results
(1) Outer Rotor with 360 Stator Slots
In order to keep copper losses the same in comparison, some changes are made as follows:• Cross-section of stator slot for conductor:
1400mm2 (288 slots) vs. 1120mm2 1400*288/360 (360 slots)
• Current (peak) flow in each conductor: 1300A(288 slots) vs.
1040A (360 slots)1300*8/10
FEM Comparison Results
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00Time [ms]
-20.00
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
Y1
[Wb
]
Ansoft Corporation Outer rotor3XY Plot 1
Curve Info
FluxLinkage(WindingA)Setup2 : Transient
FluxLinkage(WindingB)Setup2 : Transient
FluxLinkage(WindingC)Setup2 : Transient
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00Time [ms]
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
800.00
Mo
vin
g1
.To
rqu
e [k
Ne
wto
nM
ete
r]
Ansoft Corporation Outer rotor3XY Plot 5
Curve Info
Moving1.TorqueSetup2 : Transient
Torque Production
Winding Flux
Linkage
(1) Outer Rotor with 360 Stator Slots
(2) Outer Rotor with 288 Stator Slots
FEM Comparison Results
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00Time [ms]
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
Y1
[Wb
]
Ansoft Corporation Outer rotorXY Plot 1
Curve Info
FluxLinkage(WindingA)Setup2 : Transient
FluxLinkage(WindingB)Setup2 : Transient
FluxLinkage(WindingC)Setup2 : Transient
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00Time [ms]
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
800.00
Mo
vin
g1
.To
rqu
e [k
Ne
wto
nM
ete
r]
Ansoft Corporation Outer rotorXY Plot 5
Curve Info
Moving1.TorqueSetup2 : Transient
Winding Flux
Linkage
Torque Production
(2) Outer Rotor with 288 Stator Slots
(3) Inner Rotor with 360 Stator Slots
FEM Comparison Results
Winding Flux
Linkage
Torque Production
0.00 20.00 40.00 60.00 80.00 100.00 120.00Time [ms]
-20.00
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
Y1
[Wb
]
Ansoft Corporation Innerrotor1XY Plot 2
Curve Info
FluxLinkage(Winding1)Setup1 : Transient
FluxLinkage(Winding2)Setup1 : Transient
FluxLinkage(Winding3)Setup1 : Transient
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00Time [ms]
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
800.00
Mo
vin
g1
.To
rqu
e [k
Ne
wto
nM
ete
r]
Ansoft LLC Innerrotor1XY Plot 1
Curve Info
Moving1.TorqueSetup1 : Transient
(3) Inner Rotor with 360 Stator Slots
(4) Inner Rotor with 288 Stator Slots
FEM Comparison Results
Winding Flux
Linkage
Torque Production
(4) Inner Rotor with 288 Stator Slots
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00Time [ms]
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
Y1
[Wb
]
Ansoft LLC InnerrotorXY Plot 3
Curve Info
FluxLinkage(WindingA)Setup1 : Transient
FluxLinkage(WindingB)Setup1 : Transient
FluxLinkage(WindingC)Setup1 : Transient
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00Time [ms]
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
800.00
Mo
vin
g1
.To
rqu
e [k
Ne
wto
nM
ete
r]
Ansoft LLC InnerrotorXY Plot 1
Curve Info
Moving1.TorqueSetup1 : Transient
3. Conclusions• PM machine plays a critical role in WTG systems
• Direct-driven WTG requires a large size machine and heavy use of permanent magnet
• Optimal sizing of PM machine is significant
• Two rotor structures are possible• Slot/phase/pole fractional or integer
makes differences• FEM comparison results are
presented• Design of PM machine satisfying
specifications is achieved.
Thanks!
Q & A