College of Energy and Electrical Engineering, Hohai University, Nanjing 211100, China

Aiming at the problem of reactive power compensation in high-voltage high-power occasions in the wind farm, a reactive power compensation control and three-phase DC voltage balance control method based on the cascaded H-bridge STATCOM is proposed. Firstly, based on the equivalent of the large-scale wind farm, the voltage unbalanced condition in the wind farm is considered,and the reactive power compensation control strategy is carried out for the wind farm in the positive sequence coordinate system and the negative sequence coordinate system. In order to realize the three-phase capacitor voltage balance control of the cascaded H-bridge STATCOM, the power flow between the wind farm and the cascaded H-bridge STATCOM is analyzed. According to the active power flow, the feedforward compensation of phase-to-phase voltage control and the zero-sequence voltage to be injected are calculated. The feedforward control is added on the basis of feedback control to improve the accuracy of phase-to-phase voltage balance. Finally, the wind farm equivalent model and the reactive power compensation model of cascaded H-bridge STATCOM are established in MATLAB/Simulink. The simulation results verify the effectiveness of the proposed control strategy for dynamic reactive power compensation of wind farm and phase-to-phase voltage balance of cascaded H-bridge STATCOM under steady-state and power grid fault conditions.