Phase angle compensation control strategy for low-voltage ride through of doubly-fed induction generator

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