New prospects of modular multilevel converter applied to voltage source converter high voltage direct current transmission

The modular multilevel converter (MMC) is a member of multilevel converter family, and is suitable for being applied in multilevel converter topology for voltage source converter high voltage direct current (VSC-HVDC) transmission due to its many advantages. To review the recent advances in the area of MMC technology, which has half bridge terminology, we firstly introduced the topology circuit, operating principle, technical characteristics and application fields of MMC, then analyzed the advantages of MMC by comparing with two level and three level VSC converter, and described the latest research and engineering application status of MMC, especially the research of mathematical model, modulation strategy, capacitor voltage balancing, precharge, circulating current, control, valves test, and the application in VSC-HVDC. Finally, we put forward the disadvantages and key issues to be urgently solved of MMC for the future. It is shown that MMC has extensive application prospect and is one of an important development direction for power HVDC transmission in future.