Analytical estimation of common mode conducted EMI in PWM inverter

In PWM inverter system, the high dv/dt and di/dt due to the fast switching of IGBT could bring serious EMI issues. How conducted emission measurement should be made are specified. Based on the study of mechanisms on common mode conducted electromagnetic interference (CM EMI) associated with a single phase PWM inverter, the origin and propagation path of CM EMI noise are highlighted. Compared with buck converter, a simple equivalent circuit is proposed to study the CM EMI. Time and frequency domain analysis is conducted to obtain CM current waveforms and noise spectra in 10 kHz-30 MHz frequencies. The simulated CM EMI waveforms are compared with the actual experiments to verify the validity of the proposed model. The modeling method described can be readily extended to a three-phase PWM inverter.