Research on Single-Stage Five-Level Grid-Connected Inverter for Wide Input Voltage Range

Photovoltaic cells are affected by factors, such as external radiation and temperature, their output voltages have wide range. For adopting to the wide input voltage range from photovoltaic, a novel single-stage five-level grid-connected inverter is proposed in the paper, and the functions of inverter and boost are realized in the transformation. Compared with the traditional multi-level grid-connected inverter, the inverter has the advantages of buck-boost, simple topology, easy control, fewer power devices, and lower switching losses. First, the topology of the inverter is designed and the feasibility and working mode is analyzed. Then, on the basis of the analysis of current sharing characteristics, the inverter's operating mode is analyzed. Based on the traditional PR control method, the model predictive control algorithm is used to control the inverter on the grid. Moreover, the control principles and control process of the modulation method are introduced. At last, the proposed grid-connected inverter is closed-loop designed and simulated, and the feasibility of the topology is verified.