A Novel Economical Type of Four Capacitor Combined Half-Bridge Sub-Module Topology

With the rapid development of energy interconnection and power electronic devices, modular multilevel converters (MMC) are widely used in the field of high voltage direct current transmission (HVDC). The traditional half-bridge sub-module topology lacks the ability to clear the DC fault current, and the full-bridge sub-module topology has a high investment cost, some other improved topologies are difficult to both clear the DC fault current and achieve the ability to balance the capacitor voltage after the fault. Based on the half-bridge sub-module topology, this paper proposes a four-capacitor combined half-bridge sub-module (FCC-HBSM). This FCC-HBSM can not only effectively clear the DC fault current, but also self-balance the capacitor voltage after the fault. And, compared with other improved topologies, it has higher economic benefits. The single-ended MMC-HVDC is simulated by MATLAB/Simulink. The simulation results show that FCC-HBSM has a good ability to clear the DC fault current and keep the capacitor voltage balanced after the fault.