Turbo-MMC: Minimizing the Submodule Capacitor Size in Modular Multilevel Converters with a Matrix Charge Balancer

This paper presents a Turbo-MMC architecture with a Matrix Charge Balancer (MCB) to minimize the size of the submodule capacitors in modular multilevel converter (MMC) based medium voltage motor drives. The MCB manages the energy in all the submodule capacitors of a standard MMC. It balances the low frequency pulsating power among many MMC submodules and can significantly reduce the submodule capacitor size as well as the voltage ripple. We introduced the operation principles of the Turbo-MMC, and systematically investigated the tradeoffs between the capacitor size reduction and the power conversion stress of the MCB. A distributed phase-shift control strategy was adopted to compress the voltage ripple of the submodule capacitors while maintaining high performance for the MMC. Theoretical analysis and detailed design guidelines for the Turbo-MMC architecture are presented. A scaled-down MMC prototype and a 12-Port MCB have been built and tested to verify the effectiveness of the Turbo-MMC concept.