Control of Grid-connected Inverter based on Filter Capacitor Current Compensation

The LC filter is widely applied in the grid-connected inverter as it is easy to control and has preferable high frequency attenuation characteristic.The effect of output filter capacitor on magnitude,phase and low-order harmonics of grid current in grid-connected inverter with LC filter is analyzed.A digital PI control strategy with filter capacitor current compensation and grid voltage feed-forward is proposed and the design method of controller in the discrete time domain is given.Then the grid voltage disturbance rejection capability of the controller is analyzed in the perspective of harmonics impedance.Theoretical analysis and experimental results verify that the proposed control strategy can improve the THD of grid-connected current,as well as output power quality of the inverter system effectively.