Vehicle-level EMC Prediction Methodology And Application Technique Based On Multi-port Network Theory

As the improvement of electronic technology brings about the improvement of automobile performance,the variety and quantity of electrical/electronic devices in vehicles increase greatly,resulting in the deterioration of the electromagnetic environment inside and outside the vehicle and the seriousness of EMC problems.The vehicle-level EMC prediction technique can help to evaluate EMC at the early stage of vehicle development,so that the hidden EMC problems can be detected in advance,so as to reduce the risk of EMC problems at the later stage.In order to solve the difficulties of vehicle-level EMC prediction,this paper proposes a vehicle-level EMC prediction methodology based on multi-port network theory,the effectiveness of the proposed methodology is verified through a bench test,and the practicability is verified through the use in prediction and improvement of vehicle-level low frequency radiated emission.In addition,the potential crucial application techniques when the methodology is applied are studied.At first,this paper analyzes the characteristics of vehicle-level EMC problems,and proposes a vehicle-level EMC prediction methodology based on multi-port network theory.The methodology uses multi-port network to characterize vehicle-level EMI transmission path which serves as electrically large size structure,and regards each component which serves as electrically small size structure as a port of the network.The characteristics of the network and its ports are combined to predict vehicle-level EMC.This methodology separates coupling paths from the characteristics of interference sources/sensitive equipments,and models the coexistence of multiple interference sources/sensitive equipments.As for EMC problems of a complex system,this paper decomposes complex system into several weakly related subsystems,and realizes EMC prediction of the complex system according to EMC of each subsystem.Then,the validity of the proposed methodology is verified by a bench experiment simulating of vehicle-level radiated emission.Then,the EMC prediction methodology proposed in this paper is applied in prediction and improvement of vehicle-level low frequency radiated emission in a domestic electric vehicle.The prediction model is established according to the characteristics of low-frequency radiated emission of the electric vehicle,and the characteristics of vehicle network,port characteristics,and antenna factors are combined to predict the level of low frequency emission.The characteristics of vehicle network are obtained by simulation in software and conversion of parameters;the port characteristics are obtained through measurement in the actual vehicle;the antenna factors are obtained by antenna calibration.The predicted results agree with the measured results within the range of error.In addition,the prediction methodology is applied in troubleshooting the component with greatest EMC problem and formulating the efficient improvement scheme,which validates the accuracy and practicability of the proposed EMC prediction methodology for vehicle-level EMC problems.In the end,this paper discusses the crucial application techniques about practical engineering problems.This paper introduces the guiding value of the methodology in each process of automobile development;and then discusses how to obtain the characteristics of components which are related to the EMC problems through the bench experiment at the period when the prototype has not been developed.Then,the characteristics of common mode/differential mode interference loop are studied,and the modeling methodology of the coexistence of common mode and differential mode is given.These crucial application techniques can improve the range of adaptation of the prediction methodology.