Virtual inertia coordination control strategy of DFIG-based wind turbine for improved grid frequency response ability

Abstract

The capability of the inertia response of the Double fed induction generator (DFIG) is mainly achieved at the cost of its economic benefits. As such, this study proposes a coordinated control strategy with frequency modulated inertia layered optimization while considering the inertia response of DFIG direct current (DC) side capacitor. According to the disturbance size of the system, the inertia control task is dynamically assigned to the DFIG DC capacitor and speed inertia control module to reduce the startup times of speed control and improve the operation economy. On this basis, we propose a dynamic recovery of DC capacitor voltage based on State of charge (SOC) self-recovery to solve the problem of voltage clamping after the inertia response of DFIG DC capacitor at its stable operating boundary and thus cannot participate in subsequent inertia control. Aiming at the frequency secondary disturbance caused by DFIG speed recovery, a variable coefficient droop control method based on logistic regression function is proposed to realize the dynamic ordered recovery of DFIG speed. Simulation results show that, compared with the traditional synchronous control with the simulation time sequence of 280 s, the proposed timing optimization coordinated control strategy reduces the rotor start times by 12 times, and the wind energy capture increases by 3.6%.