Research On High Reliability Permanent Magnet Motor Traction System For Urban Rail Transit

With the improvement of permanent magnetic materials,the permanent-magnet motor has been developing rapidly.Due to high efficiency,high torque density and high power density,the permanent magnet motor traction system is gradually used in urban rail transit.In the permanent-magnet motor traction system,three-phase permanent-magnet motors are generally driven by three-phase voltage source inverters.Compared with the asynchronous motor traction system,the permanent-magnet motor traction system requires more power electronic devices.More power electronic devices mean higher fault rate.In order to enhance the reliability of the traction system,the permanent-magnet motor traction system usually requires fault-tolerant operation capability.High reliability permanent-magnet motor traction system for urban rail transit is studied in this thesis.The main research contents of this thesis are listed as follows.1 The background and the significance of this thesis are explained.The development status of urban rail transit are introduced.The latest technologies of urban rail transit traction system are reviewed.2 The topological structure of permanent-magnet traction module for urban rail transit is introduced.3 A fault-tolerant control method is proposed for dual-motor drive system under open phase fault.The formulas of the maximum average phase copper loss in loss mode and torque mode are respectively developed by the data-fitting method.According to the fitted formula,the over current phenomenon can be avoided.If the load is light,loss mode is preferable since the total copper loss can be reduced.If loss mode cannot provide enough torque,torque mode should be activated since the total torque can be increased.4 A dual-level hysteresis current control is proposed for the five-leg drive system.The six phase-switching-states of two three-phase motors are obtained by standard current hysteresis control.If the two coupling phases have the same phase-switching-states,the-phase-switching-state of any coupling phase can be directly assigned to the common leg;otherwise,the leg-switching-state of the common leg is determined by the master slave selection principle.The coupling phase with the larger absolute value of the phase current error is determined as the master coupling phase and the leg-switching-state of the common leg is set as the phase-switching-state of the master coupling phase.5 A direct torque control method is proposed for the five-leg drive system.The weight functions are designed based on the electromagnetic torque error and flux error.The leg-switching-state of the common leg is determined by comparing the values of the two weight functions.Additionally,the performance distortion of the proposed direct torque control method for the five-leg drive system is theoretically analyzed.6 An experimental platform for permanent-magnet motor traction system is established based on dSPACE.