Research On Characteristics Of Crosstalk In Cables And Radiation Of Converter System Based On Transmission Line Model

The transfer characteristics,prediction and suppression methods of electromagnetic noise are hot issues in EMC research.As an important connecting element of electrical and electronic equipment,Multi-conductor transmission lines(MTL)play the role of transmitting electrical signals.However,the electromagnetic coupling which is crosstalk between cable harnesses will cause function failure or even malfunction of electrical equipment.Electromagnetic radiation will spread to outside space in the form of electromagnetic waves,which affects other equipment.In this paper,MTL and power converter are taken as the research objects,and a series of researches on crosstalk noise and radiation noise are carried out,which include the following parts:1.The crosstalk noise characteristics of MTL system are analyzed.Based on transverse electromagnetic(TEM)wave,this paper analyzes the distributed parameter model of MTL,obtains the general solution of voltage and current frequency domain form by combining with Thevenin’s theorem,and uses the multi port chain parameter to represent the relationship between voltage and current according to terminal constraints.Finally,according to method of moment(Mo M),transfer characteristics of far end crosstalk(FEXT)in multi-layer cable bundles are obtained by software simulation analysis.2.Prediction and suppression of crosstalk noise in MTL system is studied.Firstly,the crosstalk noise is divided into capacitive and inductive crosstalk and the extraction method of electromagnetic parameters is introduced;the crosstalk prediction model is built based on the theory of MTL,and experiment platform of crosstalk is built.The correctness and effectiveness of the prediction model are verified by simulation and experiment;the influence of MTL structure on crosstalk is analyzed.According to the advantages of inductive and capacitive crosstalk,the FEXT transfer function under the condition of weak coupling is derived.Lastly,the crosstalk elimination network is designed with the electromagnetic parameters of MTL,and the suppression effect of crosstalk is demonstrated by simulation.3.The prediction method of electromagnetic radiation noise in power converter system(PCS)is studied.Based on the analysis of characteristics and mechanism of basic radiation antenna,the common mode(CM)current path model is established and the equivalent model of radiation prediction(EMR)is simplified.The parasitic capacitance of PCS and EMR is extracted,and EMR is iteratively optimized according to the corresponding relationship of the capacitance parameters,thus the structure of EMR is determined.In the anechoic chamber,electric field intensity of two models is tested respectively,and radiation intensity is in good agreement with experimental details,which proves the effectiveness and validity of this method.4.The suppression measure of electromagnetic radiation noise in PCS is studied.This part analyzes that the ferrite magnetic ring can weaken the transfer ability of electromagnetic energy by changing the scattering matrix of cables to reduce the electromagnetic interference,so as to establish the model of MTL network and magnetic ring;scattering parameters is used to evaluate the effect of noise suppression by vector network analyzer(VNA),and the influence factor of suppression effect is analyzed.Finally,the exceeding standard frequency point of power converter radiation is suppressed in the anechoic chamber,and the recommended installation mode of the magnetic ring is given,which makes PCS pass the radiation test standard.