Voltage droop control is a common control strategy for multi-terminal HVDC transmission systems, while the traditional voltage droop control strategy has problems, such as large DC voltage fluctuations and unbalanced power distribution. To maintain the voltage stability of MMC-MTDC system and the power balance between the converter stations, an improved droop control strategy is proposed in this paper. The droop coefficient is designed by comparing the measured value of the multi-terminal direct-current voltage with the reference value of voltage. The four-terminal MMC-MTDC simulation model is built in PSCAD/EMTDC, and the proposed control strategy is simulated and verified under both transient and steady state conditions. The results show that the proposed control strategy can reduce the DC voltage deviation of MMC-MTDC system and improve the reliability and stability of the system. The correctness and effectiveness of the proposed method are verified.
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