Effect of Phase-Locked Loop on Transient Characteristics of Wind Turbine Generator under Abnormal Frequency Offset

With increasing penetration of wind power generation, influence of transient Characteristics of wind turbine generator (WTG) on safety and stability of power grid is becoming more and more important. The doubly-fed induction generator (DFIG) is connected to the power grid through the back-to-back inverter. The vector control method based on phase-locked synchronization is adopted. The phase-locked loop (PLL) drives the internal potential phase change to realize the synchronous operation with the power grid. PLL is core of back-to-back inverter, which connects DFIG with grid. Therefore, it has great influence on transient characteristics of DFIG. Dynamic model of PLL is built in this paper. Frequency and phase tracking performance of PLL under abnormal frequency deviation is studied by changing its parameters. And its effect on transient characteristics of DFIG is analyzed. Simulation models are built, the influence of frequency and phase tracking performance of PLL on transient characteristics of DFIG under abnormal frequency deviation is simulated.