Binary Capacitor Voltage Control-based Multi-Level Converter for Low Nominal DC Voltage Applications

Multi-level converters synthesize the stair-shaped multi-level 3-phase voltage, the synthesized voltage with higher voltage levels are closer to the pure sinusoidal waveform. Thus this significantly improves DC/AC power conversion quality. The most promising multi-level converter is the modular multi-level converter (MMC) with high voltage levels nowadays because MMC is expandable to a wide range of voltage levels due to its modularity and simple capacitor voltage balancing. However, the design cost and DC voltage and sub-module ratings limit the number of voltage levels. Consequently, MMC with a low DC voltage rating has lower DC/AC power conversion quality than that of MMC with a high DC voltage rating. To provide high DC/AC power conversion quality for low nominal DC voltage applications, this paper proposes a new multi-level converter named as the binary capacitor voltage control-based multilevel converter. Compared to MMC, this proposed converter synthesizes significantly higher voltage levels for low DC voltage ratings with a significantly reduced number of circuit elements and control complexity. Still, it maintains the modular design advantage and compact 3-phase converter design of MMC. This paper presents theoretical and simulation studies of the proposed converter for eight-level applications using Matlab/Simulink.