Abstract:The medium voltage DC distribution network has a good development prospect. In this paper, the multi-terminal MMC-HVDC control strategy for power supply to passive networks is studied for the flexible DC power distribution demonstration project of Guizhou Power Grid. Firstly, the power supply characteristics of the passive network and the feasibility of power supply from the MMC-HVDC to the passive network are analyzed. The MMC mathematical model based on hybrid submodules is studied. Then a simulation model of the four-terminal flexible DC transmission system for powering the passive network is built and the corresponding double loop control strategy is designed. Conventional passive-end controllers use constant AC voltage and frequency control. The control principle of virtual synchronous generator is introduced. Combined with project requirements, the paper also designs a passive-end controller that uses virtual synchronous generator control. Finally, PSCAD is used to simulate the multi-terminal flexible DC transmission system model and its passive-end controller design. The simulation results show that the two control strategies can realize flexible power supply to the passive network, however, passive end controllers based on virtual synchronous generator control can reduce frequency fluctuations during load fluctuations.