A protection scheme for DC-side fault based on a new MMC sub-module topology

•A new MMC sub-module topology is designed and a protection scheme is proposed.•Prevent the thyristor from being mis-triggered, thus avoiding the risk of system fault.•Attenuation of fault current is effectively accelerated, thus protect sub-module devices.•Fault isolation time is shortened and sub-module devices are protected from damage.•Quickly restore the system to normal operation in the case of instantaneous fault.