Modular multilevel converter based unidirectional medium/high voltage drive system

This work introduces a novel unidirectional Power Electronics system of converters to be applied in medium/high voltage (MV/HV) drives. The system employs two modular multilevel converters (MMCs) connected through a MV/HV dc bus. The active rectifier is a new unidirectional MMC topology and the inverter is the already known MMC. This is feasible since most of the MV drives present today do not require energy regeneration. The resulting unidirectional system leads to increased reliability and reduced components count. A proper control strategy is presented to provide unit power factor at the mains side and field oriented control at the machine side. Simulation results from a system driving a three-phase 11 kV/1.9 MW induction motor from a 11 kV/60 Hz ac grid are presented.