The impact of high-voltage and fast-switching devices on modular multilevel converters

US government is funding the development of high-voltage and fast-switching power semiconductor devices based on silicon carbide (SiC) for applications in medium- and high-voltage power systems. The availability of these devices should reduce the complexities of grid-connected advanced power electronic systems like medium-voltage voltage-source converters (VSC) for HVDC terminals, power electronic interfaces for distributed generation, or high-power motor drives. However, fast-switching devices may augment the adverse effects of parasitic inductances that are inherent in any power converter layout. Hence, this paper presents a theoretical analysis of the impacts that the developing 15-kV SiC insulated gate bipolar transistors (IGBTs) have on modular multilevel converters (MMCs) in terms of the sub-module (SM) numbers, the SM capacitance, the effects of parasitic inductances on overvoltages, capacitor and IGBT module volumes, and THD. An 800 MW ±320 kV VSC-HVDC terminal is selected as a case study to illustrate the potential advantages of such a high-voltage and fast-switching semiconductor device.