Parameter Design of LLCL Filter for NPC Grid-Connected Inverter

This paper introduces a design method for LLCL filter of NPC grid-connected inverter. By analyzing the ripple current of NPC inverter in different switching states, the inverter side inductance, series capacitor and grid connected side inductance are designed by the side ripple ratio of the inverter, the branch series inductance is designed by the resonance at the switching frequency, the passive damping method is adopted to eliminate the resonance peak, and the branch resistance is designed. The parameters of each device of the designed LLCL filter meet the requirements of grid connection. The performance of LLCL filter is tested by MATLAB/Simulink simulation to achieve the purpose of grid connection.