Coordinated Control of DFIG's RSC and GSC Under Generalized Unbalanced and Distorted Grid Voltage Conditions

This paper proposes a coordinated control of the rotor-side converter (RSC) and grid-side converter (GSC) of a doubly fed induction generator (DFIG)-based wind-turbine generation system under generalized unbalanced and/or distorted grid voltage conditions. The system behaviors of the RSC and GSC during supply imbalance and distortion are investigated. To enhance the fault ride-through operation capability, the RSC is properly controlled to eliminate the torque oscillations, whereas the GSC is carefully designed to ensure constant active power output from the overall DFIG generation system. To achieve simultaneous regulation of the positive-/negative-sequence currents and fifth-/seventh-order harmonic currents for both the RSC and GSC, a novel current controller, consisting of a conventional proportional-integral regulator and a dual-frequency resonant compensator, is proposed and implemented in the positive (dq)+ reference frame. The simulation and experiment studies demonstrate the correctness of the developed model and the effectiveness of the suggested control strategy for DFIG-based wind-turbine systems under such adverse grid conditions.