Common-mode interference study of a auxiliary power supply based on the serialization of SiC MOSFETs for MMC-HVDC system

As modular multilevel converter high-voltage direct current system (MMC-HVDC) is widely used, its auxiliary power supply (APS) needs the DC input ultra-high voltage (kV class) and the DC output low voltage, which is used for supplying power to the drive and control modules. Firstly, this paper designed an ultra-high voltage flyback power supply based on the serialization of SiC MOSFETs. Secondly, a novel multi-switch conducted electromagnetic interference model for the APS is proposed. The novelty of the proposed model lies in that it found the coupling difference between one switch condition and multi-switch condition for the first time. Then through the mathematical modeling and quantitative analysis of the serialization of switches, we find that under the condition of the same input voltage, as the number of the switches in series increasing, the common-mode interference will be larger. Finally, the above conclusion is verified by simulation and experiment, which proved the validity of the model.