The Research Of The Double Electric Locomotive’s Transient Characteristics During The Switching Different Supply Systems Process

With the rapid development of China’s high-speed rail technology and urban railtransit construction, electric traction is being widely used in high-speed rail,intercityrail and urban rail transport due to its efficient,convenient and cleanfeatures.However now the power supply system of high-speed rail and intercity rail isAC27.5kV/50Hz and urban rail transport is running under1.5kV DC traction powersupply system.In order to achieve the goal of three interconnected railtransportation,the foreign used system is almost multi-system locomotives and thedouble-system is commonly used.Therefore, it is significant to develo p multi-systemlocomotives.The point of the double-system locomotives research is regarding to theelectromagnetic transient process with power mode switching.This paper describes the structural characteristics of the circuit of thedouble-system locomotive traction drive system as well as the condition of thetransition region with power mode swithching in the foreign countries and thencompare with the traditional structure of CRE EMU.Then this paper studies theworking principle,control methods and mathematical models of the four-quadrantpulse rectifier and two-level inverter and establish the simulation model usingMatlab.Simulate the DC voltage,current and voltage of the network side of therectifier at steady conditions of the double-system locomotives.The simulationverifies the validity of the design methods and studies the principles of regenerativebraking of the locomotives.Trough the simulation of electric locomotives in the caseof regenerative braking analysis the current harmonics of rect ifier network side.For the transient process of AC to DC switching power supply mode,this paperanalyses the cause overvoltage for removing load transformer and have a simulationfor verification.Then this paper creates equivalent circuit model of the transitionprocess of the double-system locomotives and specially studies the disconnecting theAC power,coasting through the middle of the non-electrified areas,and intermedicateDC voltage trends of closing the transient process of the DC switch and the n makes asimulation for verification.Afterwards,in order to reduce electromagnetic interferenceduring handover,this paper proposes to establish DC filter unit in the transition zoneon the DC side and restrains all AC component in the system when entering the DCmode. For the transient process of DC to AC switching power supply mode,this paperestablishes an equivalent circuit model of the locomotives switching from DC modeto AC mode and analyses the harmonic current waveform distortion when closing theAC swith.Meanwhile,this paper studies the multi-winding transformer load inrushcurrent characteristics at closing time after a DC current causes magnetic saturationand have a simulation for verification.Finally,this paper proposes a new scheme ofinduction filter type isolation transformer to improve the harmonic current distortionof the network side and compares its simulations with traditional filtering methods toverify the feasibility of the program.