Research On Inversion Technology And Broadband Model Of EMU Voltage Transformer

With the rapid development of technological level and economic strength,high-speed EMUs have developed rapidly in China.In the field of high-speed EMUs,some related technologies have reached leading level in the world.More and more people choose highspeed EMUs as the main means of travel.Therefore,the safe and stable operation of the EMU is particularly important.However,various overvoltages that appear during the operation of the EMU will seriously harm the high-voltage equipment on the EMU,resulting in an EMU operation accident.Therefore,in order to trace the source of accidents and prevent accidents caused by overvoltage on EMUs,accurate overvoltage data is urgently needed.Aiming at the non-linear characteristics of the transmission characteristics of the voltage transformer of the EMU at high frequencies,which leads to the inaccuracy of the current acquisition of the overvoltage and voltage data of the EMU,this paper proposes a new method for obtaining the overvoltage of the EMU.Firstly,the transfer characteristics of the voltage transformer of the EMU were measured by the sweep frequency method and the scattering parameter method.Then,based on the fast Fourier transform and the inverse fast Fourier transform,a waveform inversion technology of the voltage transformer of the EMU was proposed.More accurate overvoltage data can be obtained through waveform inversion technology.An experimental verification platform was built,the overvoltage signal was simulated by the fast pulse.The inversion results were in good agreement with the actual measurement results,which verified the feasibility and accuracy of the inversion technology.The smoothing algorithm of moving average reduces the calculation error caused by data oscillation,and the inversion results are smoothed and the agreement with the actual measurement results is improved.Based on the simulation platform,a broadband model of the voltage transformer of the EMU is built.The measured scattering parameters of the voltage transformer of the EMU are converted into admittance parameters.According to the equivalent circuit of the two-port network,the admittance parameters of each branch of the Pi-type equivalent circuit are calculated to obtain the admittance value of each branch of the Pi-type equivalent circuit.The admittance value of each branch of the equivalent circuit is vector fitted,and the rational function expression of each branch admittance is obtained.Based on black box modeling and basic circuit theory,the rational function expression is converted into an RLCG equivalent circuit.Using the simulation software,Pi-type equivalent circuit was built,and broadband model of the voltage transformer of the EMU was established.The simulation results were compared with the actual measurement results to verify the correctness of the simulation model.Finally,the paper studies the applicability of the transfer characteristics of the same type of voltage transformers.The amplitude-frequency characteristics and phase-frequency characteristics of voltage transformers with different operating mileages were tested and analyzed,including three new products and three 1.2 million operating mileages.On this basis,fast pulse experimental was carried out to verify the transmission characteristics of the same type of voltage transformers applicability.