Integrated control strategy of vehicle supercapacitor energy storage system based on MMC

Aiming at the problem that the single urban rail train impacts the traction network voltage during the starting and braking process and causes the instability of the network voltage, this paper proposes an MMC-based vehicle supercapacitor energy storage system (vehicle MMC-SCESS). The system uses MMC topology as the main circuit and the control flexibility and fault tolerance of the system are improved by dispersing the supercapacitor energy storage unit into the MMC sub-module. Then taking the overall structure of the vehicle MMC-SCESS as the research object, the working principle of the a-phase bridge arm circuit is analyzed in detail, and the general working mode of each energy storage sub-module is summarized. Aiming at the main circuit structure of the energy storage system, an integrated control strategy is proposed. By controlling the charge and discharge state of the supercapacitor energy storage unit, the energy is realized to flow between the urban rail train, the DC traction network, and the super capacitor energy storage system. Finally, a three-phase fivelevel vehicle MMC-SCESS simulation model is built in Matlab/Simulink. The simulation waveform verifies the feasibility of the energy storage system control strategy.