Analysis and Experiment of A Common-ground Five-Level Inverter Based on Switched Capacitors

Multilevel inverter has received widespread attention in photovoltaic (PV) energy system due to its low total harmonic distortion. In this article, a single-phase five-level inverter is proposed. The common ground structure eliminates the leakage current by connecting the negative terminal of the PV panel to the neutral point of the ac side. In addition, by means of a switched-capacitor unit and the virtual dc-link technique, a two-time boost inverter within a single-stage operation was achieved. Furthermore, a dual-objective finite control set model predictive control is proposed for the topology. Using this control, the complicated modulation design is eliminated. And it formulates a cost function, encompassing both the flying-capacitor voltage and grid-connected current to achieve dual-objective control. The control of the flying-capacitor voltage mitigates the risk of charging current surges caused by significant drops in capacitor voltage. Finally, the simulation and experimental results verify the feasibility of the proposed topology and control algorithm, which show the accurate tracking of reference current and voltage.