Analysis and design of L plus LCL-filtered dual-frequency single-phase grid-connected inverter

To increase the efficiency of the grid-connected inverter, this study proposes an L + LCL-filtered dual-frequency single-phase grid-connected inverter. The proposed inverter consists of the low-frequency unit and high-frequency unit. The low-frequency unit transmits power to the grid at the low switching frequency. The high-frequency unit uses the feed-forward method to eliminate grid switching current ripples without current harmonics detection. The passive damping LCL filter is used to attenuate high-frequency unit switching harmonics. The operation principle of the proposed inverter is analysed, and the parameter design method of the inverter is introduced. An experimental prototype is built to test the performances of the inverter. Simulation and experimental results show that the grid current harmonics are effectively suppressed, and the efficiency of the proposed inverter can be higher than that of the L-type inverter and LCL-type inverter.