A Review of EMI Research in Modular Multilevel Converter for HVDC Applications

The modular multilevel converter (MMC) is one of the most critical implementation forms of high voltage direct current transmission. However, the electromagnetic interference (EMI) problems in MMC are unavoidable and complex due to the nonlinear switching behavior of a considerable number of submodules. In this article, the state of the art of EMI research in MMC is reviewed. The characteristics of MMC EMI sources are studied by analyzing the topology and modulation method of MMC and the dynamic turn-on and turn-off processes of the power electronic devices. The standard evaluation and the modeling methods of MMC EMI emission are reviewed by analyzing the EMI propagation paths. In addition, the EMI reduction methods of MMC at sources and along the propagation paths are summarized. Finally, the MMC EMI research is concluded and the future prospects are presented.