A Novel MMC H-type Sub-module with Capability of DC Fault current Clearing and Voltage Self-balancing

The clearance of DC fault current and the fast restart of converter need to be achieved for DC transmission system based on the modular multilevel converter (MMC). This paper proposes a novel MMC sub-module topology named diode clamp H-type sub-module (DCHTSM), which can clear DC fault current symmetrically and has the capability of capacitor voltage self-balancing. Meanwhile, DCHTSM ensures the control simplicity and has good economic performance. Finally, a single terminal MMC-HVDC system is built by MATLAB/Simulink, and effectiveness of DCHTSM-MMC in DC fault current clearance and fast restart is verified by simulation results.