Study on Electro Magnetic Interference in Power Electronics

点击翻译按钮获取中文摘要

In this research, prediction of the circuit components which affect EMI such as high frequency leakage current and radiation noise, analysis of the mechanism of EMI troubles, and suppression technique of EMI are studied.The results are as follows,1.Prediction of the circuit components.(1) Parasitic capacitance existing in the power transistor modules : It is proofed that the parasitic capacitance existing in the power transistor modules cause the high frequency leakage currents. Through the investigation of the relation between the parasitic capacitance and the leakage currents, effective technique for suppressing the leakage current is proposed. From experiment by using a experimental set-up and simulation, the effectiveness is proofed.(2) Parasitic capacitance existing in the batteries : In case that the batteries are connected to the DC-bus in the converter is investigated, and found out that a lot of high frequency leakage current was flowing trough the parasitic capacitance existi … More ng in the battery. The equivalent circuit focused on the leakage current is carried out, and the suppression scheme by using the common mode voltage suppression circuit, described in 2 chapter on this abstract, is proposed.(3) The other components : With regard to the circuit components such as filter reactor and parasitic inductance existing in the DC-bus line, very important operating characteristics affecting EMI trouble are pointed out.2.Suppression technique for high frequency leakage current :(1) Common mode voltage suppression method : In the conventional scheme for reducing high frequency leakage currents, common mode reactors are connected to three phase AC lines in series. However, in this method, it is difficult to apply it to large current systems. In this study, a novel common mode current reduction technique by connecting a common mode voltage suppression circuit to the inverter/converter circuit in series is proposed. The optimum circuit condition of the suppression circuit is carried out and the effectiveness is proofed from the experimental and simulation results.(2) Soft switching and DC common mode reactor method : In this method, making the switching transient waves on the main switch soft in addition to inserting a DC common mode reactor for suppressing the high frequency leakage current is studied. The consideration of the optimum circuit parameter and the suppression effect is done.3.Suppression technique for high frequency radiation noise :(1) As a result of high speed switching of the switching devices, high frequency radiation noise is caused. Owing to this study, it is clarified that the origin of the radiation noise is the high frequency resonant current flowing through the DC-bus capacitor and the switching devices. The equivalent circuit for the radiation noise is estimated and proofed it. Furthermore, the effective technique for suppressing the radiation noise is proposed and proofed its effectiveness from the experimental and simulation results. Less