Phase Angle Compensation Control Strategy for Low Voltage Ride Through of Doubly-Fed Induction Generator

Crowbar-based control is one of the main low voltage ride through (LVRT) control methods for doubly-fed induction generator (DFIG), but converter is still at risk of being damaged by over-current at rotor side after crowbar exits during fault recovering period. For the issue, a model for fault process analysis based on equivalent dynamic model of DFIG is established. The mechanism of phase angle jumping when fault occurring and grid voltage recovering and its impact on vector orientating precision are analyzed. Based on this, jumping phase angle compensation principle is proposed to improve existing LVRT control strategy. Then the process of control is divided into four periods, i.e., normal operation period, crowbar switching period, crowbar exiting period and grid voltage recovering period. In normal operation and crowbar exiting period, stator flux orientation control of DFIG is applied. In crowbar switching period, IGBT pulses of rotor side converter are locked, but grid side converter maintains normal operation. In grid voltage recovering period, phase angle compensation control is applied. Simulation results show that over-current in grid voltage recovering period can be effectively limited by the proposed control strategy.