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Frontiers in Energy

Front Energ    2012, Vol. 6 Issue (2) : 184-192
Dynamic contribution of variable-speed wind energy conversion system in system frequency regulation
Yajvender Pal VERMA1(), Ashwani KUMAR2
1. Department of Electrical & Electronics Engineering, UIET, Panjab University, Chandigarh 160014, India; 2. Department of Electrical Engineering, National Institute of Technology Kurukshetra, Haryana 132119, India
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Frequency regulation in a generation mix having large wind power penetration is a critical issue, as wind units isolate from the grid during disturbances with advanced power electronics controllers and reduce equivalent system inertia. Thus, it is important that wind turbines also contribute to system frequency control. This paper examines the dynamic contribution of doubly fed induction generator (DFIG)-based wind turbine in system frequency regulation. The modified inertial support scheme is proposed which helps the DFIG to provide the short term transient active power support to the grid during transients and arrests the fall in frequency. The frequency deviation is considered by the controller to provide the inertial control. An additional reference power output is used which helps the DFIG to release kinetic energy stored in rotating masses of the turbine. The optimal speed control parameters have been used for the DFIG to increases its participation in frequency control. The simulations carried out in a two-area interconnected power system demonstrate the contribution of the DFIG in load frequency control.

Keywords doubly fed induction generator (DFIG)      load frequency control      inertial control      wind energy conversion system (WECS)     
Corresponding Authors: VERMA Yajvender Pal,   
Issue Date: 05 June 2012
 Cite this article:   
Yajvender Pal VERMA,Ashwani KUMAR. Dynamic contribution of variable-speed wind energy conversion system in system frequency regulation[J]. Front Energ, 2012, 6(2): 184-192.
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Yajvender Pal VERMA
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Fig.1  Inertial control schematic
Fig.2  vs. curve for maximum power available
Fig.3  Linearized model of two-area interconnected power system
Fig.4  DFIG-based wind turbine control based on frequency change
Equivalent wind turbine inertiaHe11.5 pu?MW?sHe21.5 pu?MW?s
AGC integral control gainKagc10.05Kagc20.05
Power system gainKp150 Hz/puKp260 Hz/pu
DFIG integral controller gainKwi10.1Kwi20.1
DFIG proportional speed controller gainKwp11.23Kwp21.58
Regulation droopR13R23
Tie line synchronizing coefficientT°0.07 pu?MW/HzT°0.07 pu?MW/Hz
DFIG turbine time constantTa10.2 sTa20.2 s
Conventional generation governor time constantTh10.1 sTh20.1 s
Power system time constantTp110 sTp210 s
Transducer time constantTr115 sTr215 s
Conventional generation turbine time constantTt11 sTt21 s
Washout filter time constant for DFIGTw16 sTw16 s
Tab.1  Model constants used for simulation
Tab.2  Optimal parameters of the controllers for 10% wind penetration
Fig.5  Area frequency responses with and without DFIG
Fig.6  Tie-line power per unit
Fig.7  Generation response from the DFIGs of two areas
Fig.8  ACEs of two areas.
(a) Without DFIG; (b) with DFIG
Fig.9  Generation response of the conventional units.
(a) Without DFIG; (b) with DFIG
Fig.10  Speed variations of DFIG-based wind turbines following a load change of 2% in area-1 under different regulation support
Fig.11  Frequency response for load perturbation of 1 percent and 2% at time zero and 20 s respectively
Tab.3  US and OS of frequency responses for varying wind penetration level.
Fig.12  Frequency response of area-1 for different penetration level
Fig.13  Frequency response of area-2 for different penetration level
Fig.14  Generation response of conventional generators at different wind penetration level
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