Research On EMI Modeling And Rectification Technology Of Phase Shifted Full Bridge DC-DC Converter For Electric Vehicle

With the deterioration of the environment and the depletion of non renewable resources,the country has paid more and more attention to the energy problem,which makes the electrification become the mainstream development direction of the automobile industry.Compared with traditional vehicles,electric vehicles contain power batteries,drive motors,voltage converters and other strong electromagnetic interference components.At the same time,the number of weak current,high frequency and wireless devices in the vehicle is increasing due to the intelligent vehicle,which is vulnerable to the interference of strong current system,resulting in electromagnetic compatibility(EMC)problems.DC-DC converter is an essential component and one of the main interference sources of electric vehicles.In order to realize the prediction,analysis and rectification of its electromagnetic interference(EMI)in the design stage,the EMC performance is improved by optimizing the circuit design.This paper mainly studies the EMI modeling,EMC problem analysis and rectification scheme evaluation of DC-DC converterIn order to predict the EMI of DC-DC converter,the EMI modeling method of DC-DC converter based on multi port network theory is studied,aiming at the electromagnetic characteristics of different interference sources,complex coupling path and coexistence of linear and nonlinear interference.The topology model of conducted interference and radiated interference is established.The interference path is regarded as a multi port network,and the interference source and sensitive equipment are regarded as the external Thevenin equivalent circuit of the network.The coupling characteristics of the network are reflected by the functional relationship between the ports,so that the EMI prediction is converted into generation calculation.Based on the multi port network EMI model,aiming at the problems that the contribution sources of each EMI in DC-DC converter are difficult to quantify due to heterogeneity,this paper evaluates the potential of the interference factors from sensitivity and contribution degree,and introduces entropy weight method to normalize and rank.The influence of EMI contribution sources on EMC is evaluated,and the analysis and positioning of EMC problems are realized.As the selection of the rectification scheme is not only affected by the objective EMC problems,but also restricted by the subjective conditions such as time,cost and technical difficulty,this paper builds a tree structure that can evaluate and compare a variety of indicators and factors hierarchically,and realizes the evaluation of the rectification scheme through the same level distribution and hierarchical merging of weights,which improves the rationality and accuracy of the scheme selection.Finally,the multi port network EMI modeling method is applied to the simulation device of phase shifted full bridge DC-DC converter,and the conducted and radiated interference models are established.By comparing the interference calculation results with the measured data,the accuracy of EMI model interference prediction is verified.Then,the main source of EMI and the evaluation and selection of the rectification scheme are carried out for the DC-DC converter analog,which realizes the analysis and rectification of EMI and optimizes the EMC design.