A single-phase asymmetrical NPC inverter topology

This paper presents a topology and a modulation scheme for a single-phase multi-level inverter referred as asymmetrical NPC. The proposed topology is formed by two legs, namely, a NPC and a standard two-level leg, where The NPC leg allows access to the middle point of the DC source. The proposed asymmetrical NPC is able to produce an output with five voltage levels. The proposed modulation algorithm forces the two-level leg to commute at line frequency. This has the benefits of reducing switching losses, common mode voltage, and hence, leackage currents. It also eliminates the need for very fast switching devices. Numerical simulations are presented to assess the performance of the proposed topology and modulation strategy.