Abstract: For the MMC-HVDC system connected to a passive network, the active power balance will be broken and the DC voltage will fall rapidly when the AC fault occurs at the sending end, which also will threaten the safe operation of the converter station. Firstly, the passive network load characteristics and the variation mechanism of the electrical quantity of the converter station under AC fault are analyzed in this paper. Then, based on the conventional control of inverter station connected to a passive network, an additional fault ride-through control strategy is proposed to produce d-axis voltage correction instruction according to DC voltage variation. The core idea of the control strategy is as follows: when the active power of sending end loses rapidly, the active power output of the inverter station is reduced through modifying the command value, so as to maintain the active power balance of the converter station at both ends and restrain the DC voltage sag. Finally, an MMC-HVDC system connected to a passive network is simulated on the PSCAD/EMTDC. The results show that the proposed additional control can decrease the DC voltage sag, reduce the active power fluctuation at the sending end during recovery after fault cleaning, and improve the AC fault ride-through capability of the system.