Abstract: After a short-circuit fault occurs on the DC side,the half-bridge modular multilevel converter （MMC） is prone to block,and improper unblocking during fault recovery leads to overcurrent of the bridge arm,and MMC has the risk of continuous blocking,leading to systemic safety problem.To solve this problem,the unblocking overcurrent mechanism of insulated gate bipolar transistor （IGBT） during fault recovery is analyzed theoretically,and a new fault recovery control is proposed.Firstly,it is pointed out that the fault loop in the underdamped state will inevitably lead to IGBT blocking.Secondly,it is revealed that the source of IGBT unblocking overcurrent during fault recovery is the voltage difference between DC side and AC side.Further,a fault recovery control is proposed to remove the power outer loop during the blocking period,raise the AC-side modulation wave to reduce the pressure difference and suppress the current of the bridge arm.Taking into account the capacitor voltage and reclosing time of submodules during the blocking period,an adaptive outer loop reference value curve is constructed to solve the overvoltage problem caused by power surplus.The results show that compared with the existing series AC-side starting resistance method,the proposed fault recovery control can reduce the peak current of the bridge arm from 1.57 p.u.to 0.79 p.u.in different operation conditions,and adjust the power-side MMC DC voltage to the rated value after unblocking,which is helpful to speed up the fault recovery.