Research on Modelling Method of Conducted EMI in the Electric Drive System on Motor-Load Conditions

As the main Electromagnetic Interference (EMI) source in electric vehicles, the high-voltage electric drive system is required to test according to CISPR 25. And the test shall be carried out on the specified motor-load condition. To analyse and suppress the EMI noise, a high-precision model is proposed in this work. First, common- and differential-mode EMI paths are investigated. Second, a SPICE based simulation model is established. Typical high-voltage EMI filter, shielding cables and connections, drive motor, IGBT module are modelled and verified separately. Motor-load simulation with pulse width modulation is also realized in Simulink. Third, the whole system simulation in combination with the component SPICE models and the motor-load model is verified from 9KHz to 108MHz. Moreover, based on the established system-model simulation, the high-voltage EMI filter is designed to suppress the typical noise peaks. It can be shown that the proposed modelling method, especially considering the real motor-load condition, can effectively predict the EMI noise level. And high-efficiency noise suppression solutions could be achieved from the proposed system simulations.