In order to meet the requirements of fast current limiting of DC fault for modular multilevel converter(MMC)based DC transformer

the research of active current limiting control is necessary. By a detailed analysis of DC pole-to-pole fault mechanism and modeling of the fault current

the expressions of arm currents considering the feed at rising stage

the peak current and the peak time of short-circuit current are derived

then the conclusion that the fault current can be limited by reducing the number of submodules to switch on at each phase after DC fault is obtained. According to this conclusion

a novel active current limiting control method is proposed. By producing additional DC offset and AC gain

the DC component and AC component of the bridge-arm voltage are adjusted to achieve the purpose of current limiting through the modulation process. Finally

the simulation results verify the effectiveness and superiority of the proposed method.