In view of the voltage source converter based multi-terminal direct current(VSC-MTDC)transmission system connected with large-scale offshore wind farms

the power distribution mechanism of the conventional DC voltage droop control is derived

and the impacts of the control strategy on the frequency of receiving grid are analyzed. The DC capacitor of the VSC-MTDC system is used for energy storage

and the frequency of receiving grid is coupled with the DC voltage of VSC-MTDC system. Then an adaptive droop control strategy participating in the primary frequency regulation is proposed. The strategy can adjust the DC voltage droop coefficient in real time according to the AC system frequency deviation

which makes each converter station rapidly adjust its own power output without communication. Thus the AC system frequency can be stabilized in a reasonable range. Finally

a five-terminal VSC-MTDC system is formed in the DigSILENT/PowerFactory simulation software

and the effectiveness of the proposed method is verified by results of three simulation examples.