Switched-Capacitor Multi-Input Seven-Level Inverter for HFAC Applications

In this paper, a switched-capacitor-derived multi-level inverter (SCMLI) is developed for high-frequency-ac (HFAC) applications. The proposed inverter uses unequal dc voltage sources as its input. It is useful where multiple dc sources with a common ground are available, e.g., renewable energy systems, ac microgrids, fuel cells, and electric vehicles. This topology gives higher voltage levels and adequate reactive power support with fewer power-electronic switches than the existing switched-capacitor multi-level configurations. Capacitor voltage balancing is not required as it’s charged twice in each cycle of the inverter output. Parallel operation of inverters is required while connecting several dc sources. The proposed inverter solves this problem by connecting multiple sources at once. Selective-harmonic-elimination pulse width modulation (SHE-PWM) technique is used to minimize the higher-order harmonics in the output current. Different operating modes of the inverter are explained in adequate detail. A hardware prototype is assembled for the proposed multi-level inverter. The experimental and simulation results corroborate the expected performance of the proposed inverter.