Modular multilevel converter（MMC） is the key of a voltage sourced converter high voltage direct current（VSC-HVDC） transmission project. The parameter design and type test of MMC are based on the results of switching overvoltage analysis. Therefore

an MMC model for switching overvoltage analysis was presented. Based on the system parameters of ±500 k V VSC-HVDC project

influences of design parameters of MMC on switching overvoltage were researched

including surge arrester

arm reactor

and submodule capacitor. The results show that the decisive fault conditions for switching overvoltage analysis of MMC are single phase-to-earth fault on AC side of MMC

pole-to-earth fault on DC side of MMC

and phase-to-phase fault on AC side of MMC. When increasing the charge ratio of the surge arresters

the maximum switching overvoltages of the phase-to-ground on AC side of MMC

of the pole-to-ground on DC side of MMC

and between terminals of MMC arms are decreased. As the arm reactors inductance increases

the maximum switching overvoltage of phase-to-ground on AC side of MMC decreases. In addition

as the submodules capacitor capacitance increases

the maximum switching overvoltage of pole-to-ground on DC side of MMC increases. The research results can provide a reference for the design and test of converters for VSC-HVDC projects.