$\mu$-Synthesis Robust Control of Variable Speed Wind Turbine Generators for Participating in Microgrid Frequency Regulation

Wind power is expected to reach substantially higher levels of penetration in the near future. The participation of variable speed wind turbine generators (VSWTGs) in frequency regulation will also become an urgent need. Considering wind speed changes, solar/load power fluctuations as well as parametric perturbations in microgrid, a $\mu$-synthesis robust control method is proposed for VSWTGs to participate in microgrid frequency regulation based on deloading control. The dynamic frequency response (DFR) model of VSWTGs participating in microgrid frequency is deduced. A $\mu$-synthesis robust controller is designed using D-K iteration method, considering parametric uncertainty. And the robust stability (RS) and robust performance (RP) of the closed-loop control system is analyzed. The time-domain simulation results of microgrid frequency show that the proposed $\mu$-synthesis robust control method has better dynamic performance and anti-disturbance ability, compared with traditional $H_{\infty}$ robust control and the droop control.