| As a new type of induction motor,linear induction motor not only keeps the simple structure like the ordinary induction motor,but also has the advantage for it can be used in various occasions.At the same time,it also has strong climbing ability and the radius in the turning process is relatively small.So it is widely used in urban rail transit for traction.In the process of controlling for the linear induction motor?no matter which control method is adopted,the initial parameter value of the motor needs to be set in the control system.If the initial parameters set in the system have a large error comparaed with the actual value,the control performance will be seriously affected,even making the control can’t be implemented.Because the linear induction motor is special in structure,the parameter identification method of the common induction motor is no longer applicable.Therefore,in order to provide accurate initial parameter values for the linear induction motor control system to control the linear induction motor better,this thesis proposes a method for obtaining the parameters of the linear induction motor while it is stationary.The method is mainly based on the PWM inverter,and considers the circumstances for the secondary leakage inductance of the linear induction motor is much smaller than the primary leakage inductance.Firstly,this thesis analyzes the influence of the parameters of linear induction motor on its common control methods,and expounds the role of the initial parameters of the motor in the motor control performance and online parameter identification,which indicates that the research on parameter identification method of linear induction motor at standstill is of great significance.Based on the summary of the research status of linear induction motor parameter identification method,the identification idea of single phase test method is proposed.Then,according to the characteristic of linear induction motor that the traveling wave magnetic field and the electromagnetic thrust can’t be generated in the single-phase test,and the motor always keep still,the parameter identification method of the linear induction motor based on the PWM inverter in the static state is theoretically derived.Single-phase DC test and single-phase AC test with high frequency and low frequency are conducted to obtained the primary resistance,primary leakage inductance,secondary leakage inductance,mutual inductance and secondary resistance of the linear induction motor.Then,four linear induction motors with different power and different voltage levels are taken as research objects and the parameter identification model is established by SIMULINK software.The parameters of the motors are obtained through simulation and compared with the actual values.The frequency range applicable in single-phase high-frequency and low-frequency tests is determined by discussing the variation of the parameter identification error following frequency.The parameter identification error of this method and the traditional method are compared under the same experimental conditions,which proves that the accuracy of the method in this thesis is higher when the method is applied to linear induction motor.In addition,considering the influence of the voltage drop of the switch,the dead time and the delay time of the switch on the parameter identification when the inverter is in use,the corresponding compensation method is proposed to compensate these factors,and the correctness of the compensation method is verified.Finally,the ANSYS Simplorer and Maxwell softwares are used to perform field-circuit coupling finite element simulation analysis,and the simulation results are compared with the results calculated by analytical method and simulation results with SIMULINK.It can be proved that the end effect of the linear induction motor can be considered when the parameter identification of linear induction motor is carried out by using this method.So the feasibility and correctness of the method can be further demostrate. |
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