The present disclosure relates to a sub-module of a power converter, the sub-module capable of allowing failure-causing electric current to bypass the sub-module when a failure occurs in the sub-module. According to an embodiment of the present disclosure, there is proposed a sub-module of a power converter, the sub-module including an energy storage unit, at least one power semiconductor circuit connected, in parallel, to the energy storage unit and configured with a plurality of power semiconductor switches and a plurality of freewheeling diodes, an auxiliary switching element connected to the energy storage unit, turned on when a failure occurs, and thus allowing electric current from the energy storage unit to pass through, and a main switching element connected in series to an output terminal of the auxiliary switching element, arranged between two output terminals connected to one of one or more of the power semiconductor circuits, forced to undergo an induced failure due to application of a voltage stored in the energy storage unit through the auxiliary switching element, internally short-circuited, and thus connecting the output terminals to each other.