Modeling And Suppression Of Conducted Electromagnetic Interference Of DAB Converter Based On S-parameter

The dual active bridge(DAB)converter has become a widely used isolated DC-DC converter in electric vehicles.Although it has the advantages of bidirectional energy flow and electrical isolation of input and output,a large number of switching devices and complex circuit structures also bring strong electromagnetic interference(EMI)problems.Therefore,it is of great significance to study the mechanism of conducted electromagnetic interference in DAB converters.In this paper,the parasitic parameters of the switching device are extracted based on the S parameters,and a time-domain simulation model of the DAB converter is built.Then a two-port equivalent behavior model for predicting common-mode conducted EMI was established,which was verified on the time-domain simulation model and hardware platform.Finally,an EMI filter design method was proposed based on the model.The main research content is divided into three parts.(1)Aiming at the problem that the parasitic elements in switching devices affect the EMI of the converter,a method of extracting the parameter values based on S parameters and establishing parameter model to study the conducted EMI is proposed.Firstly,the port network parameters are introduced,and the parameter values of the second-order RLC series circuit are obtained through the single-port S parameter.Secondly,the parasitic parameters of MOSFET are extracted by using the two-port S parameters,which are verified by ADS simulation and experiment.Thirdly,this method is extended to the application of parameter extraction of half-bridge circuit and the process steps are designed.The effectiveness of this method is verified on half-bridge circuit and high-power IGBT module based on MOSFET.Finally,based on the above extraction results,a parameter model of the MOSFET was established,and a DAB converter time-domain simulation model was built to study common-mode conducted EMI.(2)Aiming to solve the problem that the complex structure of DAB converter leads to the difficulty of conducting EMI analysis,a two-port equivalent behavior model is established based on the S parameter to predict common mode conducted EMI.Firstly,the working mode of the converter is deduced and its working principle is introduced in detail.Secondly,the definition of the two-port equivalent behavior model is given and illustrated,and the modeling process is designed for simulation and experiment respectively.Finally,the circuit time domain simulation was carried out by SABER?and the simulation modeling process was verified.The DAB converter hardware platform was built to verify the experimental modeling process.(3)Aiming at the problem of excessive common-mode conducted EMI of DAB converters,a filter is designed to suppress interference based on the two-port equivalent behavior model.Firstly,the attenuation requirements of the converter are calculated from the predicted EMI noise.Secondly,determine the cut-off frequency and filter component parameter values based on the ideal attenuation amplitude of the filter.Finally,the time-domain simulation model and hardware platform are used to analyze the attenuation effect of the filter,and the effectiveness of the proposed suppression method is verified.