Comparison of Two Filter Design Methods for Conducted EMI Suppression of PMSM Drive System for Electric Vehicle

In order to solve the problem that the conducted voltage of a motor drive system for electric vehicle (EV) exceeds the standard limits of CISPR25-2016, two different design methods of electromagnetic interference (EMI) filter for HV power supply were proposed. The first method is to design a wide-band EMI filter based on engineering method. It can achieve the insertion loss of 60 dB within 150 kHz - 108 MHz. Another proposed method is to design the EMI filter based on the resonance peaks suppression. During the second filter design process, by analyzing the common mode (CM) and differential mode (DM) interference paths at two key frequency points 1 MHz and 30 MHz, the dominated parameters responsible for the over-standard points were determined, and the CM and DM filter circuit was designed accordingly. Compared with the filter designed by the first method, the filter designed based on resonance peaks suppression can better meet the design goals, without further rectification according to the tests, and it is smaller in size, only 1/4 of the filter size designed by the first method, lower in cost, and easy to be engineering.