Two-and-One Set of Arms MMC-Based Multilevel Converter With Reduced Submodule Counts

Multilevel inverters are receiving increasing attention recently. Among different multilevel topologies, modular multilevel converter (MMC) seem to be a promising topology in the medium-voltage and high power applications. But similar to other multilevel topologies, one drawback is high count of power semi-conductor devices and associated gate driver and protection circuitry. This paper proposes a new MMC based inverter that can produce the same output voltage as a conventional MMC but with significantly reduced number of power semi-conductor devices. This is achieved by introduction of an extra middle arm to the conventional MMC. The new topology offers significant reduction in size and cost of the overall system through reducing the number of SM capacitors, high-frequency switches, related gate-driver and protection circuits, heat sinks, and the capacitor voltage measurements. This paper first describes the new topology and explains its switching states and mathematical model then it provides simulation results to verify the theoretical outcomes.