Abstract: In order to solve the power imbalance problem of island VSC-HVDC links operating in parallel with AC line when the AC line is out of operation due to a fault， according to the analysis on grid-connected and the island operation control strategy of the island power supply system， a virtual synchronous control based AC fault ride-through coordination control strategy for MMC-HVDC island power supply system is proposed to realize power coordination in self-consumption and non-self-consumption scenarios. Aiming at the self-consumption scenario， a method for MMC power transfer control is proposed， which reduces the power shortage of the system only by increasing its output power， and can effectively reduce the influence range of unbalanced power. Aiming at the non-self-consumption scenario， a coordinated control strategy for MMC and wind farms to participate in unbalanced power regulation is designed to control the MMC to work at the maximum power output， and the power adjustment capability of the wind turbine is used to compensate for the remaining power deficit through over-speed load-shedding to maintain the power balance of the island system. Finally， the effectiveness of the proposed coordinated control strategy is simulated and verified. The results show that the strategy can realize the smooth transition of island power supply system from grid-connected to island operation， and can effectively improve its safe and stable operation capability.

Key words: modular multilevel converter （MMC）, virtual synchronous generator（VSG）, load-shedding reserve, coordinated control strategy