Doubly Fed Induction Generator System Resonance Active Damping Through Stator Virtual Impedance

The penetration of wind power has been increasing in the past few decades all over the world. Under certain nonideal situations where the wind power generation system is connected to the weak grid, the doubly fed induction generator (DFIG)-based wind power generation system may suffer high-frequency resonance (HFR) due to the impedance interaction between the DFIG system and the weak grid network whose impedance is comparatively large. Thus, it is important to implement an active damping for the HFR in order to ensure a safe and reliable operation of both the DFIG system and the grid-connected converters/loads. This paper analyzes and explains first the HFR phenomenon between the DFIG system and a parallel compensated weak network (series RL + shunt C). Then, on the basis of the DFIG system impedance modeling, an active damping control strategy is introduced by inserting a virtual impedance (positive capacitor or negative inductor) into the stator branch through stator current feedforward control. The effectiveness of the DFIG system active damping control is verified by a 7.5 kW experimental downscaled DFIG system, and simulation results of a commercial 2 MW DFIG system is provided as well.