The characteristics analysis of the modular multilevel converter(MMC)under the DC pole-to-pole short-circuit fault is studied

which is an important issue in the research of fault management

electrical system design and MMC based power system planning. Firstly

the transient process before and after the PWM blocking of DC pole-to-pole short-circuit fault is analyzed

while the conduction over-lapping angle is defined. Secondly

four possible steady-state short-circuit current paths and seven cases according to different conduction over-lapping angles are identified. And the characteristics of steady-state current at both the AC and DC sides are qualitatively analyzed. Then the influences of the impedance distribution factor and equivalent short-circuit resistance on the steady-state short-circuit current are elaborated

while a practical engineering calculation method for the steady-state short-circuit currents at both AC and DC sides is deduced. Finally

the effectiveness of the analysing method is verified through the case study.