Study of current control strategy of STATCOM based on LCL filter under distorted grid conditions

In order to improve the filtering performance of the system with small inductor, LCL filter is selected as the output filter of distribution static synchronous compensator(D-STATCOM). LCL filter is a three-order system, the resonant peak may result in the instability of system. State-feedback control based on virtual impedance is proposed to suppress the resonant peak, which reduces system losses compared with passive damping. The grid voltage harmonics result in the distortion of compensation current, which makes the compensation current not track its reference. A multi-resonance proportional resonant. (PR) regulator is proposed to increase the grid input impedance at a specific frequency, which rejects the disturbance of grid harmonics and improves the current tracking performance. Simulation and experimental results prove the validity of this method.