Suppressing Secondary Ripple On DC Side Of Single-phase Rectifier Based On CRH3

With the increasing proportion of high-speed emu in railway transportation,the requirements for safety,rapidity and economy of emu in the process of operation are more and more strict,and the structural design of the whole vehicle must meet certain technical indicators.In the existing vehicle structure design,how to reduce the quality of the vehicle body as much as possible under the premise of ensuring the performance of the train,that is,lightweight design has become an indispensable part.At present,single-phase rectifier is used in front of the traction converters,which leads to secondary ripple on the dc side inevitably.However,the secondary ripple suppression circuit used in engineering is bulky and heavy,which is not conducive to the lightweight design of train.Therefore,it is of high practical significance to study a filtering scheme for CRH3,the fastest CRH(China Railway High-speed)series emus,which can not only meet the requirements of absorbing secondary ripple on the dc side,but also reduce the volume and weight.This paper first briefly introduces the development and research status of train traction drive system.In this background,the research status of secondary ripple in traction converters is introduced,and the advance of active filter scheme in this paper is pointed out.Then the structure and working principle of the traction converter based on CRH3 vehicle are analyzed.According to the power requirements of the train,the key parameters of the converter,such as capacity,input voltage and current,input filter inductance,are designed.The mathematical model of single-phase rectifier is established,and the transient current direct control strategy and bipolar SPWM modulation are studied.The mathematical model of three-phase inverter is established and the indirect vector control strategy and mixed multi-mode pulse width modulation of traction motor are studied.The correctness of the basic control strategy and modulation strategy is verified by building a simulation model based on Matlab/Simulink.Secondly,according to the energy flow relationship of traction converter,the generation mechanism of secondary ripple in dc side of traction converter is deeply analyzed.From the control principle and hardware circuit of rectifier and inverter,the influence mechanism of secondary ripple causing large amount of low order harmonics in rectifier network side current and inverter output voltage is revealed.The existing passive secondary ripple suppression scheme is designed,the main circuit of passive secondary ripple suppression is studied and the filter parameters are calculated.The mechanism and influence of secondary ripple are verified by the simulation model.Then,based on the mechanism of secondary ripple accordance with the requirements of the lightweight design of the train,design the active secondary ripple suppression scheme,design the active secondary ripple suppression of main circuit parameters of the filter and the filter inductor,filter capacitor and a given dc bias voltage are calculated,puts forward the applied to active secondary ripple suppression circuit of voltage and current double closed-loop control strategy;The engineering design of passive scheme and active scheme was carried out respectively,and the engineering 3D model was established.The advantages of the two schemes were compared.The correctness and effectiveness of the active secondary ripple suppression scheme for single-phase rectifier proposed in this paper are verified by building a simulation model based on Matlab/Simulink.Finally,this paper built a small power experiment platform with FPGA as the core controller and a high power verification platform with semi-physical object as the core.Based on Verilog language,the traction converter and secondary ripple suppression circuit experiment program was written.Through the comparison and analysis of experimental results and theories,the correctness and effectiveness of active secondary ripple suppression scheme for single-phase rectifier proposed in this paper are verified,which lays a good foundation for its engineering application.