Research On Conducted EMI Of High Power Frequency Control System

Currently, almost all power converters using PWM modulation technique, and switching devices as IGBT has many advantages like reducing switching losses, reducing the volume of the radiator and so on, but there are also some risks. While rapid implementation of IGBT switching operation, it will produce high du / dt and di / dt. Due to the parasitic capacitance and inductance, a lot of electromagnetic interference will be produced by the transient currents and it will affect the stability of the equipment itself, and other equipments around. Currently, electromagnetic compatibility problem is getting attention. This article will study for electromagnetic interference suppression power inverter. Conducted EMI produced by high power dual three level frequency control system are compared under different modulation strategies, and an EMI filter is designed to suppress the conducted EMI effectively in this paper.Firstly, the generation mechanism of the conducted electromagnetic interference is analyzed. Through IGBT double pulse experiment testing, its turn-on and turn-off processes have been analyzed deeply. Transmission paths of common mode and differential mode interference of the system are analyzed. Since LISN network is no longer applicable for high power frequency control system, high voltage probe is used to measure the interference and the interference transmission paths based on high voltage probe are given.Then, according to the actual situation of the scene, the high frequency model of the high power frequency control system is established. And then the modulated waves are manifested, and the double Fourier series expressions of the interference sources are obtained. The simulation waveforms and the experimenta waveforms are compared to verify the correctness of theoretical analysis and high frequency model. The simulation waveforms of the three modulation strategies(SPWM, SVPWM, DPWM) of are compared horizontally and longitudinally, and the consistent conclusions are obtained by the longitudinal comparison, and the conclusion that the conducted EMI under SVPWM modulation strategy is the most serious and the conducted EMI under DPWM modulation strategy is the smallest is obtained by the horizontal comparison.Finally, a multi-stage filter is designed according to the original EMI signal extracted, and then the interference is further suppressed by reducing the length of the capacitor wiring, and the effectiveness of the EMI filter designed is verified by the experimental results.