Submodule Capacitor voltage balancing of Modular Multilevel Converter

A modular multilevel converter (MMC) is one of the latest next generation power electronic converter intended to be most suitable for industrial applications. It is made up of N number of sub-modules (SM) connected in cascaded form for obtaining desired high quality multilevel output voltage waveform. This paper deals with a three-phase MMC designed with half-bridge (HB) SMs. Phase disposition based pulse width modulation (PWM) technique is used for generating gating signals for individual sub-modules. Voltage balancing is achieved by rotating gating signals between the submodules. Modulation indices are varied for obtaining good quality output voltage waveform and required submodule capacitor voltage balance.