Phase Step Control in PLL of DFIG-Based Wind Turbines for Ultrafast Frequency Support

For doubly-fed induction generator (DFIG)-based wind turbines, this letter proposes a phase step control (PSC) in the phase-locked loop (PLL) to achieve ultrafast frequency support. In the method, a phase angle, associated with the initial frequency differentiation, is appended to the PLL when frequency event occurs. Furthermore, the control parameter of PSC is designed under the constraints of the amplitude of active power. Finally, the proposed method is validated by experiments. The results show that the response time of PSC is less than half of the existing methods, and the frequency metrics are better improved.