Because the modular multilevel converter（MMC）has good control characteristics and mature applica-tion

it is not only used in the field of HVDC transmission

but also widely used in the field of intelligent distribution.It has become a research focus in the field of flexible primary equipment of intelligent distribution network to ensurethe unlocked operation of converter under DC bipolar short circuit fault and to realize rapid self-recovery of fault.Firstly

the DC bipolar short circuit fault mechanism of MMC with full bridge sub-module（FBSM）was analyzed

and then a DC bipolar short circuit non-locking fault ride-through control strategy including zero voltage fault ride-through control and DC current control was proposed. Starting the zero voltage fault ride-through control after thefault occurs can restrain the capacitance discharge of the sub-module

and make the DC side current cross zero to fa-cilitate the DC circuit breaker to cut off the fault current. After the DC side voltage was re-established

the DC cur-rent control can be used to linearly lift the power to the fault recovery

so as to realize the non-locking fault ride-through and fast self-recovery of the converter equipment. Finally

a double-ended FBSM-MMC model was builtbased on PSCAD/EMTDC simulation software to verify the effectiveness of the proposed fault ride-through strategy.