Magnetic Field Analysis Of High-speed Maglev Train

Maglev train is a modern and high-tech rail transit tool,which achieves non-contact suspension and guidance between the train and the track by electromagnetic force.There is much electrical and electronic equipment inside and outside the train.The electromagnetic energy generated by this equipment can be transmitted to the equipment and cables in the vehicle,as well as the instruments or equipment near the railway through conduction emission and radiation emission.Therefore,it is of great significance to study the magnetic field distribution of the high-speed maglev train.The electromagnetic emission sources of the high-speed maglev train include long stator linear synchronous motor and equipment and strong current cable in the vehicle.Taking the normal conducting high-speed maglev train as an example,this thesis studied the electromagnetic emission characteristics of long stator linear synchronous motor(LSM)powered by traction power supply system,and then analyzed the magnetic field distribution of high-speed maglev train.Firstly,this thesis established the analytical calculation model of a linear motor and calculated the distribution law of air gap magnetic field based on the method of analyzing variables;then,this thesis built the three-dimensional model of the linear motor in Maxwell,after the simulation,we obtained the distribution of the magnetic field in the air gap,which reflected the electromagnetic emission characteristics of the linear motor.By comparison,the simulation results were consistent with the calculation results.The results show that the intensity of the air gap magnetic field generated by linear motor varies periodically in the range of 0-1T,and the periodic distance is about0.2m.Secondly,this thesis studied the harmonic components of the converter unit in the traction power supply system.According to the principle of pulse width modulation,we elaborated the modulation mechanism and method of SPWM and SVPWM in detail.This thesis built the circuit model and control module of the traction power supply system in Simplorer,we achieved the co-simulation of magnetic field and circuit,which combined the circuit with the linear motor model built in Maxwell.Then,this thesis obtained the output current of the converter unit of the traction power supply system under different train running speeds,and we analyzed the frequency spectrum of the current.The results show that the high-order harmonics of the converter unit output current of traction power supply system are mainly distributed in 6k Hz,12 k Hz,18 k Hz,and 24 k Hz when the train is running at low speed;when the train is running at high speed,the higher harmonic of the converter unit output current of traction power supply system is 5.72 k Hz and 6.24 k Hz,these higher harmonic components will output with the power supply of traction power supply system,thus affecting the electromagnetic emission characteristics of the linear motor.Finally,this thesis analyzed the magnetic field distribution of the high-speed maglev train.Then,this thesis established the whole vehicle model of the train in Maxwell.After the co-simulation of Simplorer and Maxwell,we studied the magnetic field near the bottom of the car and potential difference on the surface of vehicle bottom at different running speeds,when the linear motor is powered by the traction power supply system.Besides,taking the high-speed running state of the train as an example,this thesis analyzed the harmonic field near the vehicle bottom produced by the high order harmonic current,which is generated by the converter unit of the traction power supply system.These results provide a reference for perfecting the EMC design of maglev train.