Repetitive Control Circulating Current Suppression Strategy for Photovoltaic Inverter Parallel System

The parallel connection of inverters can increase the capacity of the system, but it will bring circulation problems, which will reduce the efficiency of the system and increase the system loss, and the output grid connected current will be distorted. Aiming at the zero sequence circulating current problem of multi machine photovoltaic grid connected inverter, a repetitive control strategy is proposed. Firstly, based on the analysis of the circulating current model of the inverter parallel system, a controller combining the improved repetitive control of circulating current and PI control is designed. The circulating current is suppressed by controlling the zero vector action time in the space vector modulation in each parallel module. Finally, the strategy is verified by simulation.