Research On EMI Analysis And Suppression Technology Of Traction Converter System

In recent years,urban rail transit has developed rapidly,and at the same time,traction converters,which are its main components,are also developing in the direction of high frequency and high power.This makes the converter system operate efficiently and at the same time generate serious Electromagnetic Interference(EMI).As the source of electromagnetic interference,traction converter not only affects the normal operation of the on-board control unit,but also produces electromagnetic pollution to the environment near the train.It is of great significance to suppress its electromagnetic interference.At present,the electromagnetic radiation of the whole train has a standard limit.Once it exceeds the standard,the general method is rectification,and the labor and time costs are high.Therefore,it is worth discussing and studying EMI suppression in the design stage of the converter and verifying its suppression effect from computer simulation.The main research contents are as follows:(1)The power busbar filter circuit is designed to suppress conducted interference.The filter cutoff frequency and characteristic impedance are introduced in the parameter design.The advantage is that the range of the passband and cutoff band is clarified,and without making the impedance mismatch.In the structure design,the common and differential mode circuits share inductance,and the design method of the magnetic permeability magnetic ring,which solves the problem that the current EMI filter cannot have both high withstand voltage and small size.The connection between harmonics and EMI is analyzed,and the relationship between them is proved by simulation,designed a sinusoidal filter circuit to suppress harmonics,thereby suppressing electromagnetic interference.During the design of the filter circuit,the high-frequency parameters are fully considered,which can more accurately predict its suppression effect on high-frequency EMI,which is convenient for finding problems in the design and debugging.And the conduction and radiation interference of the converter are fully considered during EMI filter design,which effectively solves the problem of excessive radiation.(2)The conducted EMI prediction model of the DC-AC traction converter system is established.To improve the accuracy of the circuit model in predicting high frequency EMI,the method to establish a high frequency model of the converter is used to study high frequency EMI.The operation of the circuit model is closer to the actual one,which provides great help for the design and correction of the filter circuit.The electromagnetic field radiation simulation model of the converter is constructed,and the radiation model is subdivided into common mode and differential mode models.(3)Build a conducted interference test platform,and verify the accuracy of the simulation modeling by comparing the simulated EMI signals with the measured ones.The filter element selection scheme is proposed,and the rationality of the element selection is verified.A subway train traction converter is chosen to be the research object for above all research contents.A filter was designed to solve the problem of excess radiation of converter.Through simulation and verification of the test platform,the filter can suppress 20 d B conducted interference in the interference frequency range exceeding the standard,and the radiated EMI meets standard limits.