Modeling And Prediction Of Conduction Electromagnetic Interference In Inverter System

Inverter is one of the most widely used in power electronic devices,and Usually use the switching devices such as MOSFET?IGBT?GTO etc. In order to get better performance,the frequency of the switch device is generally high, the mutation of voltage and current generated in the open and shut off time is the main source of conducted electromagnetic interference. Conducted electromagnetic interference(EMI) becomes an important factor restricting the development of power electronics and the current research focus at home and abroad. The EMI modeling and prediction have significant meaning for the design of EMI filter. The focus of this paper is modeling and prediction of conducted electromagnetic interference.Firstly, according to the research of literature at home and abroad, this paper summarizes the research development of inverter system conducted electromagnetic interference respectively from three directions. After analyzing the difficulties and deficiencies of inverter system EMI modeling and prediction by now, it leads to the contents of this paper.Secondly, this paper analyzes the sources and propagation path of the inverter system conduction interference. In combination with IGBT EMI model proposed in the literature at home and abroad, this paper establishes the common-mode and differential-mode EMI equivalent circuits of three-phase four-leg inverter. In order to avoid the complex process of interference sources modeling and according to the theory of port in the circuit theory, the common-mode and differential-mode equivalent circuit transforms into two-port active network and one-port active network in this paper.Thirdly, experimental method was used to measure the frequency characteristic of all the passive components and port network impedance in this paper. Using the impedance relations between equivalent circuit and port model, this paper compares the changes of the impedance matrix on power off and on. By measuring the common-mode interference sources of the common-mode equivalent circuit and combining with the sources' relation of common-mode equivalent circuit and two-port active network, this paper figures out the equivalent interference source of two-port active network and compares with the interference source calculated with the theory of two-port network. The experimental is to verifies the relation between two-port network and equivalent circuit.Finally, we firstly measure the impedance of invertor in the condition without EMI filter and calculate the equivalent source. Then the paper predicts common-mode and differential-mode current in the condition with EMI filter. In order to verify the validity of port-model, we will compare the predicted result with the experimental result. The port-model of inverter system can predict the suppression effect of electromagnetic interference after adding EMI filter we have known. This paper will make a big difference in EMI filter design.