Self-Balancing Three-Phase Five-Level Inverter with Reduced DC Bus Voltage

Switched-capacitor/flying capacitor (FC) based multilevel converters have been gaining higher attention for their voltage-boosting ability. This feature makes them an attractive solution for renewable energy systems, such as low-voltage input photovoltaic power systems and electric vehicle systems. However, they usually require more high voltage rating switches and flying capacitors along with boosting capability. Furthermore, they suffer from high pulse currents at the switching transients. Aiming to solve these issues, this article proposes a new self-balancing three-phase five-level inverter based on the switched-capacitor (5L-SCTPNPC), which reduces the dc voltage requirement. The number of active switches is relatively smaller and seven active switches are required per phase. Especially, a soft-charging circuit for FC is designed to limit the impulse charging current. Compared to conventional multilevel inverters, the proposed five-level inverter reduces dc bus voltage by 50%. Significantly, the voltage stress of FC and the switches in parallel with FC are all reduced by 50% in comparison with some existing similar boosting five-level active-neutral-point-clamped (5L-BANPC) inverters. The operating principles, modulation strategy, and the design of the FC and charging inductor are provided in detailly. A comprehensive comparison study has been made to highlight the merits of the proposed inverter. Finally, the simulations and experiments validate the feasibility of the proposed topology.