Control and simulation of doubly‐fed induction generator for variable‐speed wind turbine systems based on an integrated Finite Element approach Qiong‐zhong Chen*, Michel Defourny # , Olivier Brüls* *Department of Aerospace and Mechanical Engineering (LTAS), University of Liège, Belgium # SAMTECH Headquarters, Liège, Belgium EWEA 2011, Brussels, Belgium
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Control and simulation fed induction generator for … and simulation of doubly‐fed induction generator for variable‐speed wind turbine systems based on an integrated Finite Element
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Control and simulation of doubly‐fed induction generator for variable‐speed wind turbine systems based on an
integrated Finite Element approach
Qiong‐zhong Chen*, Michel Defourny#, Olivier Brüls*
*Department of Aerospace and Mechanical Engineering (LTAS),University of Liège, Belgium
# SAMTECH Headquarters, Liège, Belgium
EWEA 2011, Brussels, Belgium
1
Outline
Background
Control of DFIG
Integrated simulation approach
Examples & validation
Conclusions
2
Background
Wind turbine concepts
Evolution of WT size:
Increased flexibility Increased coupling effects
(Data source: A. Perdala, dynamic models of wind turbines, PhD thesis, 2008)
WT types Gen. typesDFIG WTs DFIG
FSWTs SCIG
FCWTs PMSG, SCIG etc.
Other OSIG
Equipped gen. types
(Figure from EWEA factsheets)
3
Background
Computer-aided analysis for WT systems Software specialized in a certain field Aerodynamics: AeroDyn etc. Structure: ADAMS/WT etc. Electrics: DIgSILENT etc.? Different systems on different simulation platforms?? No detailed coupling analysis
Integrated simulation packages: GH Bladed, Simpack Wind, HAWC2, FAST etc.? Weak coupling (DLLs or co-simulation)?? Numerical stability?
Need for integrated optimization tools (Bottasso, 2010)
4
Background
Samcef for Wind Turbine (S4WT) Nonlinear FE flexible multibody solver: SAMCEF/MECANO One single platform: Aeroelastics, multibody, control, electrodynamics etc.
Flexibility in blades, shafts, tower etc. Simulation approaches: Weak & strong coupling
An integrated model on S4WT(Courtesy: Samtech)
…
5
Highlights of the paper
Improved control strategies of DFIG WTs Grid-synchronization Power optimization
Strongly-coupled approach for mechatronic systems [B. & Golinval 2006]
Integrated structure-control-generator analysis on S4WT
Brüls, O. and Golinval, J. C. The generalized-α method in mechatronic applications. Zeitschrift für angewandte mathematik und mechanik (ZAMM) 86, 10 (2006), 748-758.
6
Control of DFIG
Working process of WT systems
Control of DFIG: soft grid connection power optimization
Method: Grid-voltage-oriented reference frame Vector control PI Controller designed based on internal model control
(IMC) method
+
_ Gr(s)+ +qrVqr_refi qri
l r drs L i
+DFIG
Cqr(s)
l r drs L i
_
FF term
+
_ Gr(s)+ +drVdr_refi dri
l r qrs L i
_DFIG
Cdr(s)
l r qrs L i
+
FF term
D,q-axis rotor current control loops
8
Power control
Objective: Follow a pre-defined power-speed characteristics
profile speed regulation
Method Stator-flux-oriented reference frame
Vector control q-axis rotor current active power d-axis rotor current reactive power
IMC or pole placement method for design of controllers
9
Power control
Power control scheme
Controllers: PI or IP regulators Design of controllers
PI : IMC method (current loop) IP : pole placement method (speed loop)
controller:CTω(s)
+ _
qr_refi
qri
qrvref
e_refT
dr_refi
dri
refQ drv
DFIG
controller:CiT(s)
controller:CiQ(s)
controller:Cvi_qr(s)
controller:Cvi dr(s)
+_
+_
Decoupled speed and reactive power control of DFIG
10
Design of controllers
PI controller for q-axis rotor current i-v transfer function
PI controller on IMC
IMC parameter:
For electrical dynamics, the rise time is set to 10ms
1
( ) 1( )( )
qrvi_qr
qrr
s
I sG s
XV s R sω
1 1( ) ( ) rvi_qr qr
s
X RC s G ss ω s
riseln 9 /= t
+
_ Cvi_qr(s) Gvi_qr(s)+̄qrVqr_refi qri
qrE
current control block
11
Design of controllers
IP controller for speed control Close-loop transfer function
Pole placement method
For over-damped systems:
For mechanical dynamics, the settling time is set to 1s, DFIG alone 2.5s, with WT system
+
_Ki/s 1/(Js)
+ +e_refTref
Kp
+
_
mT
r
2
( )( ) ( )
ir
ref p i
K /Js =s s + K /J s+ K /J
2
2p d nd
i nd
K = J
K = J
5.8nd sd= /t
Speed control block
12
Integrated simulation approach
Strongly-coupled representation for mechatronic systems
Extended generalized-α solver Coupled 1st / 2nd order systems Second order accuracy Unconditional stability More details can be referred to [B. & Golinval 2006]
qMq Φ ( λ Φ) g(q,q, ) L y 0
Φ(q) 0x f (q,q,q,λ, x, y, ) 0y h(q,q,q,λ, x, y, ) 0
T ak p t
ktt
Mechanism
Control system
y ( , , , )q q q
Coupling in a mechatronic system
13
Mechatronic Modelling on SAMCEF
Considerations for the Mechatronic modelling: Functional system decomposition Modularized, parameterized components E.g. DFIG, PI, PID modules etc.
Nodes are introduced for Mechanical DOFs State variables Outputs