Modeling and analysis of conducted EMI for a modular multilevel converter

Currently, the modular multilevel converters (MMCs) based high voltage direct current (HVDC) transmission system have been widely applied due to its better characteristics, such as the stringent modular structure and good line-side behavior. This paper studies the conducted common mode electromagnetic interference (EMI) in MMC based HVDC system. As a matter of fact, interference sources are very complicated for large amounts of switches in large scale MMCs. This paper proposed a novel EMI model of MMC for the first time. Based upon that model, the influence of parasitic parameters of switches, the voltages stage of direct current side and the switching frequency on the leakage current are studied in detail. Useful information about the distribution of conducted interference both in time domain and in frequency domain can be acquired from the proposed model. Theoretical analysis and simulations demonstrated the proposed EMI model provides an intensively investigation and discussion for the conducted EMI in MMC based HVDC system.