Delta-Channel Modular Multilevel Converter for a Variable-Speed Motor Drive Application

Delta-channel modular multilevel converter (MMC) proved successful for zerolow-fundamental-frequency operation without injecting common-mode voltage. However, its application in a medium-voltage variable-speed motor drive is not verified. This paper develops a variable-speed motor drive system based on a delta-channel MMC. The converter power losses together with the compensation strategies are analyzed, and accordingly the submodule capacitor voltage controls are elaborated. The converter controls cascaded with the advanced motor control form the entire control scheme for the drive system. The system performances are tested based on a 4160-V 1-MW simulation model and 208-V 5-kW experimental setup. The results show that the delta-channel MMC along with the proposed control algorithm performs satisfactorily in a driving motor from standstill to a rated speed even under rated torque condition.