A novel topology and control strategy of modular multilevel converter (MMC)

Modular multilevel converter (MMC) is a newly introduced topology of multilevel converter, which is based on cascade connection of chopper-cells per leg. This paper presents a novel topology of MMC, in which, based on traditional topology of MMC, H-bridge (HB) cells are used for more levels of output voltage. Corresponding control strategy is presented and explained in details, including phase-disposition (PD) sinusoidal pulse width modulation (SPWM) strategy, control methods on H-bridge cells and chopper-cells, and several controls on capacitor voltage balancing. Output voltage levels of novel topology are twice as many as those of traditional one by proposed strategy. The validity of the novel topology as well as the control strategy proposed in this paper is confirmed by computer simulation.