| With the rapid development of China's railway industry,high-power power electronic devices are widely used in various series of EMUs,and a large number of signal equipment and cables are concentrated in the bottom of the vehicle,which leads to the increasingly complex electromagnetic environment inside and outside the vehicle.Considering that the traction converter system is one of the main low-frequency electromagnetic disturbance sources of EMUs,in order to study the low-frequency electromagnetic characteristics of the high-speed train bottom,this thesis takes the traction converter system of CRH2 EMUs as the main research object,the internal models of traction converter and traction motor are established,and the output current harmonics are simulated and analyzed.Based on this,the distribution characteristics of low frequency magnetic field in the bottom of EMUs caused by the output current of the traction system are studied.First of all,the structure of the traction converter system is introduced.Considering that CRH2 EMU adopts a three-level topology,the circuit structure of three-level rectifier and inverter is described respectively by comparing it with the traditional two-level circuit,and the state changes under different operation modes are obtained by analyzing the schematic diagram of equivalent switch.Secondly,based on the principle of pulse width modulation,the modulation mechanism and method of SPWM are introduced in detail.The traction converter system is divided into rectifier circuit and inverter circuit,and the main circuit and control modules of rectifier and inverter are respectively built under the platform of ANSYS Simplorer,and the simulation results are as expected.Then,the rectifier part and the inverter part are connected to form the traction converter,and the obtained output current is used as one of the disturbance sources.The final output current is analyzed in time and frequency domain,and the proportion of each current harmonic component to the total current is calculated.Motor leakage current is another important disturbance source of traction system.According to the cause of leakage current of induction motor,the common mode voltage caused by PWM modulation is studied in detail,and the common mode path model composed of stray capacitance inside the motor is established,and the values of each stray capacitance in the circuit is calculated respectively.Then,a common mode path is built on the Ansys Simplorer platform,which is connected to the circuit of traction converter,and the leakage current of the motor is calculated by simulation,and the harmonic components of the current are analyzed.Finally,in order to study the electromagnetic environment of EMUs bottom,the EMUs bottom model is built on the ANSYS Maxwell platform,and the main electromagnetic interference sources are added respectively: the output cable current of traction converter system,the leakage current of motor,the rail return current and the body return current.The low-frequency magnetic field distribution caused by these four disturbance sources in the vehicle bottom is analyzed qualitatively and quantitatively.Then,these four kinds of disturbance sources are considered at the same time,under the condition of 50 Hz eddy current field,the low-frequency magnetic field distribution characteristics of EMUs underbody are simulated and analyzed,and the conclusion that rail recirculation and cable current have a great influence on the undercarriage is obtained,which provides help for the research of high-speed train electromagnetic compatibility. |
PDF Full Text Request