Voltage balancing of modular multilevel converter for an induction motor drive

Modular Multilevel Converter (MMC) have been widely designed and used in medium as well as high voltage applications. Salient features of MMC include modular structure, high voltage levels, good quality output waveforms and fault tolerant operations. The converter consists of sub modules connected in series fashion to obtain high voltage levels. Each sub module of MMC has a floating DC link capacitor. In an MMC, an uncontrolled circulating current flows in each converter arm due to various reasons. This current causes capacitor voltage ripples. During normal operation of MMC, the floating capacitors voltage need to be limited at its fairl value, for this purpose a dynamic voltage balancing algorithm is proposed here. Applications include electrical drives, HVDC power transmissions. A five level MMC with a three phase induction motor is simulated with MATLAB/SIMULINK and results obtained are included.