A Novel Sub-module Topology for MMC Against DC Side Short-Circuit Faults

Since the traditional half-bridge modular multilevel converter (HB-MMC) is endangered under DC side short-circuit faults. This paper proposes a novel sub-module (SM) topology for MMC with DC fault limitation capability. The fault current is fully transferred to the bypass thyristor by turning off all IGBTs when DC short-circuit fault occurs, then the diode freewheeling effect is eliminated and all bypass thyristors in MMC are arranged as a fully controlled thyristor rectifier, so the fault currents can be cleared simply by inhibiting gate signals of all bypass thyristors. The feasibility and validity of proposed topology are verified by simulation results.