An Improved Virtual Inertia Control Strategy of DFIG-Based Wind Turbines for Grid Frequency Support

This article proposes an improved virtual inertia control strategy, which reduces the lag effect of a low-pass filter in conventional control and increases the speed of virtual inertia control in wind turbines. The grid frequency obtained by phase locked loop (PLL) must pass through a low- pass filter with a small cutoff frequency under distorted grid voltage. The delay caused by the low- pass filter conflicts with the goal of fast support required for virtual inertia control. This article analyzes the influence of filter on system stability and response speed in frequency detection. First, the advantages and disadvantages of differential feed-forward (DFF) control are proposed and analyzed. Then, a lag-lead-based phase compensator (LLPC) scheme is proposed to provide better system stability and rapidity. Finally, the effectiveness of the proposed control strategy is validated on an 11-kW doubly fed induction generator (DFIG) platform.