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 impedance of power grid and the interaction between DFIG control system and grid may cause voltage oscillation of the point of common coupling (PCC). Aiming at this phenomenon, this paper establishes a reactive power compensation model considering weak grid structure and rotor side converter (RSC) controllers. The result of Nyquist criterion confirms 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.

Doubly-Fed Induction Generator (DFIG); Low voltage ride through (LVRT); Reactive power compensation; Voltage oscillation; Weak grid