Conducted EMI Model and Coupling Resonant Mechanism Analysis of Multi-Cell Converter System

Multi-cell converter is used to improve the current capability and power rating of a power supply system. Due to the faster switching speeds and higher power ratings, wide-bandgap (WBG) power semiconductor devices are used for enhancing the efficiency and power density of converters, which also result in severe electromagnetic interference (EMI) because of the large dv/dt and di/dt slew rates during switching transients. Furthermore, the coupling effect in multi-cell converter aggravates EMI emissions. In this paper, the common-mode (CM) model of a multi-cell converter system is derived. Then, the transfer admittance is analyzed, revealing that the conduction paths among cells form a resonance peak, the frequency of which is related to the number of cells and filter parameters. Finally, the correctness of the theoretical analysis is verified by simulation results.