Analysis of DC Line Bipolar Short Circuit Fault in Full Bridge MMC Flexible DC System

Abstract

After the bipolar fault occurs in the flexible DC transmission line, the converter will affect the fault current, so it is necessary to analyze the fault of the system with converter. Aiming at the common full bridge MMC converter topology, this paper establishes its corresponding circuit model after fault, and derives the fault current expressions in capacitor discharge stage and bridge arm inductance freewheeling stage after blocking. Finally, the simulation is carried out in PSCAD.