Application of PLL in the Generator-side Converters for Doubly-Fed Wind Power Generation Systems

In order to investigate the enhanced control and operation of wind power generation systems based on doubly-fed induction generators (DFIG) when grid voltage is unbalanced, a novel phase-locked loop system used to realize real time phase synchronization is presented. With the help of the novel PLL, the phase of positive sequence component can be obtained quickly and accurately, even if the grid voltage appears to be unbalanced and distorted. As a result, the rapidity and stability of PLL are greatly improved. The simulation and experiment results have verified the validity and effectiveness of it under the unbalanced and distorted grid voltage.