Research On Conducted EMI In DC Power Supply With A Three Phase Inverter

Power electronics equipments that can realize the power converter efficiently are applied to electric transform, electric drive, and power system abroad. With the development of switching devices, the era of high frequency and large capacity has come. As a result, the interference has been reinforced. The fast switching devices including IGBTs and MOSFETs can bring high frequency pulses. They have very large dv/dt and di/dt , which produce large electromagnetic interference(EMI)from several kilo to several million hertz frequency. The EMI not only influences the usual work of load and inverter itself and withdraws their work lives but also has detrimental effects on the electromagnetic environment.This paper researches differential mode conducted electromagnetic interference (DM EMI) and common mode conducted electromagnetic interference (CM EMI) in DC power supply with a three-phase inverter. The DM EMI and CM EMI excitation sources and the coupling paths are analysed. Based on experimental and theoretical analysis, the conducted EMI of DC power supply with a typical inverter (DC/AC) is studied systematically. The study shows that: the biggish conducted EMI are presented at the integral times of its PWM controlling frequency, the conducted EMI decreases with reference to the increase of frequency. New DM EMI and CM EMI frequency-domain equivalent circuits are established. By the experiment, the parameters of components in the circuits are obtained and the DM EMI and CM EMI between 10kHz to 30MHz are studied. Compared the calculated DM EMI and CM EMI spectras with those of the experimented, the established models are verified to be validity.Furthermore, the rules of DM EMI and CM EMI with the change of the resistance and inductance loads are researched. As to CM EMI,the EMI does not change while the resistance and inductance loads change. But, the DM EMI changes with resistance and inductance loads. Under the condition of resistance load, the DM EMI boosts up with the load drop, especially in low frequency bandwitch. When the inductance load changes, the DM EMI does not change. The conclusion is agreement with the analysis of EMI mechanism and coupling paths.