Improved Ride-Through Control of DFIG During Grid Voltage Swell

Grid voltage swell causes a transient dc flux component on doubly fed induction generator (DFIG) stator winding even stronger than grid voltage dip, resulting in a much more serious stator, rotor current, and torque oscillation. This paper analyzes the dynamic behavior of DFIG during grid voltage swell. Based on the analysis results, the virtual resistance control strategy manages best to suppress the rotor current and torque oscillation but prolongs the transient duration, resulting in a higher rotor voltage. Thus, this paper proposed a virtual impedance control strategy to enhance the high-voltage ride-through capability of DFIG. In order to improve the dynamic performance, the optimization algorithm of virtual impedance is proposed in the paper. The effectiveness of the proposed control strategy was verified by simulation and experimental results.