Analysis and Improvement of Unbalanced Fault Ride-Through Response in DFIG-based Wind Turbines

DFIG based wind turbines (WTs) are very sensitive to grid voltage dips. This is because the grid voltage dips imposed at the connection point of the DFIG to the grid induce large voltages in the rotor windings, resulting in high rotor current. According to high penetration of DFIG based WTs, it is important that the WTs remain connected to the grid during the voltage dips and improve the grid stability. This paper proposes a combinational method for improving ride-through capability of DFIG-based wind turbines under unbalanced voltage dips. The method is realized through the rotor-side converter control and by using additional passive hardware, called stator damping resistor (SDR). The proposed method limits the peak values of transient response at the times of occurring and clearing the fault. It also improves damping of DFIG transient response, and eliminates or reduces undamped negative sequence oscillations with two times of grid frequency. Finally, performance of the proposed method is evaluated by time domain simulations.