An active damping control strategy and design method for LCL filter

LCL filter resonance peak characteristics bring about system instability. In media and high power converter, loss of passive damping method causes serious problem of fever. An active damping control strategy of capacitor current feedback and design method was proposed based on the transfer function of LCL filter and the impact of capacitor current on the damping of the system. The impact of the proposed active damping strategy on system resonance peak gain and switching frequency gain was researched. Design method of feedback parameter in active damping strategy was obtained by comparing the active damping strategy with the reactive damping method. Simulation results of grid-inverter show that this active damping strategy restrains the resonance peak, reduces harmonics at resonance frequency and increases the stability of the system.