A Novel Adaptive DC Voltage Droop Control for MMC-MTDC Considering Local Electric Variables

To solve the problem that the multi-terminal HVDC system which adopts fixed coefficient droop control has unacceptable DC voltage deviation and terrible power distribution ability, an adaptive DC voltage droop controller is designed which can give consideration to both DC voltage control ability and power distribution ability. Firstly, the basic structure of MTDC and MMC is introduced. Then a novel adaptive DC voltage droop controller is designed based on the local electric variables of the converters running in droop control mode. Finally, $\mathrm{a}\pm 200$ kv four-terminal HVDC system simulation model has been built in PSCAD/EMTDC, the adaptive voltage droop control strategy introduced in this dissertation is validated. The simulation results show that compared with the traditional droop controller, the proposed adaptive DC voltage droop controller has stronger DC voltage control ability when the power flowing through a converter is greater than the reference, or contrariwise, the controller has better power distribution ability.