Four-Port Modular Multilevel AC/AC Converter in Continuous Co-phase Traction Power Supply Application

Continuous co-phase traction power supply system is an effective method to eliminate neutral sections and provide high power quality for both the public grid and the catenary. Modular multilevel converter (MMC) can be applied in co-phase power supply system to perform three-phase/single-phase conversion. However, the existing schemes of MMC have some problems including high cost, bulky size and coupling between public grid and catenary. This paper proposed a new main circuit scheme based on four-port MMC (4P-MMC) and three-phase Y/D transformer, which significantly reduces the cost and realizes the decoupling of three-phase and single-phase sides. Simulation results are presented to verify the validation of the proposed scheme.