Study on control method for the grid-connected inverter with LCL filter

LCL filer has been widely applied in modern grid-connected inverter systems. In this paper, the impacts of LCL filter parameters on the filtering effects of harmonics and the current tracking accuracy of grid-connected inverter are analyzed, and the relationships between the inverter-side and network-side currents of the grid-connected inverter under active and reactive current output situations are derived. In addition, in the LCL-filter-based grid-connected inverter system, the current tracking ability is affected by the filter capacitor current when using the traditional control method by inverter-side current feedback. To solve this problem, a method to calculate the network-side current using the inverter-side current is proposed, and the calculated network-side current is compared with the command current in the control system. With the proposed control method, the current tracking ability of the grid-connected inverter system is improved. Simulation results show the improved control method is correct and superior.