Analysis of DFIG Terminal Voltage Oscillation Caused by Reactive Power Compensation under Weak Grid Connection

摘要

According to the wind farm codes, the doubly-fed induction generator (DFIG) is required to possess low voltage ride through (LVRT) capability during grid faults, especially reactive power compensation performance. However, under weak grid connected condition, the interaction between DFIG control system and grid may cause voltage oscillations at the point of common coupling (PCC). To investigate the mechanism of the oscillation phenomenon during LVRT, this paper establishes a reactive power compensation equivalent model, considering system transient characteristics, weak grid structure and rotor-side converter (RSC) controllers. The results of Nyquist criterion confirm that the transient stability of wind power system will be deteriorated with the increase of compensation gain value and grid impedance. A DFIG simulation model is built to verify the validity of the model and theoretical analysis.