| With healthy and sustainable development of railway lines in China,more and more CRH2 EMUs are applied to railway transportation.Some failure phenomena,which affect the normal operation of the train,have occurred now and then,such as deflector ablation,voltage transformer damaged by discharging,lighting arrester discharge breakdown caused by high order harmonic resonance,APU founction failure,speed sensors and other electrical equipment damage,and so on.In fact,the occurrence of these failures is closely related to the main circuit system of CRH2 EMU.The main circuit system is mainly composed of high-voltage system on the roof,traction drive system,auxiliary power supply system,and grounding system.It is the power supply center of the whole train,which undertakes external inputing power transformation,drive train operation,and supply power for control system.If these equipments are in the event of a failure,the normal operation of the train will be affected because the working voltage of them is very high.Using simulation and real vehicle test,this paper researches on the failure mechanism of main circuit system of CRH2 EMU,and put forward design solutions optimized to suppress the failure occurrence.To research the distributing characteristics of electric field and flow field,electric field and flow field simulation model of high-voltage system on the roof is established with ANSYS.Test platform of high-voltage system is founded,which uses real high-voltage equipment of CRH2 EMU.The paper analyses the effects of insulating property of high-voltage system influnced by different environment and different height of the insulator by doing field test.Combining test and simulation results,an design solution optimized for high-voltage system is provided,which can improve the electric field distribution of high voltage equipment area on the roof and the risk of flashover is reduced.To research transient process during lifting pantograph and ferromagnetic resonance during crossing electrical separation phase,different simulation models of transient process are established in PSCAD/EMTDC.Then suppression methods,installing magnetic ring and parallel RC filter,are put forward.The effects of these two methods are analyzed by simulation and the results shows that the methods can improve the transient performance.From the coupling relationship between the train and the traction power network,this thesis establishes the harmonic simulation model combining AT traction network and electric traction drive system of CRH2 EMU.The mechanism and transmission characteristic of high order harmonic produced by coupling between the train and traction network are studied.Based on the test data produced in the process of failure and simulation results,the solutions of control parameters of interior current loop of the four quadrant converter and interlaced control strategy optimization are advanced,which can be used to suppress two different high order harmonic resonances effectively.By doing simulation and ontrack train test,the suppression methods are verified to be effective.In addition,to meet real-time performance and accuracy requirements,an algorithm on eliminating interaction effects of fundamental and harmonic phasor estimator(FHPEI)is put forward.Aims to APU function failure of CRH2 EMU due to the EMU and traditional train operate on one railway line.This thesis analyses the tracing test results and reveals the causes of the failure by theoretical calculation and simulation.Based on the above results,two solutions have been proposed:optimizing the APU control strategies and APU input parameters.Considering train operation requirements,the APU control strategies optimization solution has been implemented,by decreasing time of uncontrollable rectifying,advancing into PWM control stage and controlling the middle loop voltage simultaneously,which can effectively eliminate the APU starting-up failure by the APU middle loop voltage produced by power network harmonics.By doing so,the later tracing test results show the APU failure never happens again.Grounding method of CRH2 EMU is analyzed in detail.This thesis do technical analysis on problems of grounding system,such as surge voltage of car body,return current in car body and track insulator influencing on the return current.The simulation model of grounding system is established in PSPICE.The parameters of main grounding part in the model are obtained by field test.Aiming to CRH2 EMU grounding structure,the grounding system returning current distribution laws and the equivalent parameters of all returning branch are obtained by test.Based on the above results,CRH2 EMU grounding and returning system simulation model is established,and distribution and propagation law of car body current,grounding current and surge voltage have been studied when CRH2 EMU is running on continuous guide way and insulation joint.Considering tradeoff between carbody surge voltage and current,this thesis conduct technical analysis on influence of resistance value and inductance value of grounding resistor.Then appropriate resistance and inductance value of grounding resistor can be determined.In the end,the paper puts forward the reasonable improvement measures for grounding system optimization. |
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