Modular multilevel converter (MMC) is increasingly being applied to high voltage direct current (HVDC) systems. However

dc short circuit situations restrain the application of a conventional half bridge MMC system. In this paper

a new sub-module topology with inserted thyristor can help the MMC system clear a dc side fault. Working states and devices voltage stress of the proposed topology are analyzed and the conduction loss comparison between the proposed topology with several existing topologies with dc fault blocking capability is carried out. Results show the proposed topology is superior to other topologies in terms of conduction loss while using the same voltage rating devices. Besides

compared with traditional half bridge topology

only thyristors and diodes are added in the proposed topology. Therefore

cost of the proposed topology can be lower than conventional hybrid MMC sub-modules. At last

the fault blocking capability of the proposed topology is verified in the simulation.