Modular multilevel converter based on arm transfer to clear dc fault

Modular multilevel converter (MMC) has great prospects in voltage source converter‐based high‐voltage direct current (HVDC) transmission. Although the typical half‐bridge MMC can bring huge economic benefits, it is unable to clear dc fault. An MMC based on arm transfer (AT‐MMC) and corresponding timing control are presented to effectively solve this drawback. Compared with the half‐bridge MMC, the AT‐MMC adds the arm‐transferring branch to the each phase unit of the converter and adds the current‐breaking branch and the energy‐absorbing branch to the dc line. Through these branches cooperating with each other, the fault current is cleared. Referring to the half‐bridge MMC with the same voltage grade, the AT‐MMC has a good economy and its additional device cost is low and additional conduction loss is very small. A model of 51‐level MMC–HVDC system is built in RT‐LAB OP5600 to verify the effectiveness of the proposed solution.