Research on DFIG flux damping control strategy based on imaginary damping winding

For double-fed induction generator (DFIG) wind power system, when grid voltage fault happens, transient DC flux component will emerge in the stator. The transient DC flux will affect the performance of output power and electromagnetic torque of DFIG. In serious conditions over voltage and current will be induced in rotor side. To mitigate this problem, a novel flux damping control strategy of DFIG is proposed based on grid voltage oriented vector control and imaginary damping winding in this paper. Firstly the transient process of stator flux under grid faults is analyzed based on the electromagnetic relationship of DFIG. The stability of DFIG grid voltage vector oriented control strategy is also analyzed. Then based on the function of damping winding in synchronous generator the novel flux control is proposed and principles of it are introduced in details. The effects of the rotor-side converter's rate and the generator operation state are considered. The validity of the proposed method is verified using a typical 1.5MW DFIG in the Matlab/Simulink simulation environment. The proposed control strategy is proven to be able to increase damping rate of the transient DC flux component in stator effectively and improve the stability of control system.