Resonance Characteristics and Resonance Suppression Method for Multi-Parallel LCL-Type Inverters

When the LCL filter is used as the inverter filter network to suppress the harmonics of the grid-connected current, the grid resonance will be caused by the inherent third-order characteristics, which seriously affects the power quality and system stability. For the resonance problem of multi-paralleled inverters in distributed grid-connected power generation system, the equivalent model of multi-inverters is established, and the distribution of resonant peak is analyzed. The influence of the number of inverters and the power grid impedance on the resonance characteristics of the system is analyzed in detail. And then, an active damping control scheme based on proportional current feedback of capacitor current is proposed to realize the resonance suppression. Finally, grid connected multi-inverters model was built in MATLAB Simulink+plecs platform to verify correctness of the theoretical analysis and the effectiveness of the proposed control strategy.