Vector Control And Parameter Identification Study Of Asynchronous Motor

With the current environmental and energy problems have become more severe,the electric car has become a hot research in each countries. The motor drive controlsystem is one of the core components of the electric vehicle. Induction motor because ofits simple structure, easy to manufacture, small maintenance workload, etc., has beenwidely applied in the electric car. The motor used by Tesla, as the U.S. leader in theemerging electric car industry, is induction motor. Currently, the method used to controlthe induction motor is mainly vector control and direct torque control, both of which arebased on the dynamic model of induction motor. According to field oriented, vectorcontrol decomposes the stator current into excitation component and torque component,making flux and torque control decoupling from each other. So the vector control hasgood static and dynamic performance. However, the vector control is very dependent onmotor parameters, especially the rotor time constant. In the motor is running, rotor timeconstant will large change, because of magnetic saturation and temperature change orother reasons, which will have serious impact on the field orientation.This paper focuses on vector control and parameter identification. First, the basicprinciples of vector control are introduced. And then the main part of the rotor fieldoriented vector control system is analyzed and derived, on the basis of which, parameteridentification is studied. Parameter identification of the asynchronous motor can bedivided into offline and online identification. Paper first discusses traditional method,which get the motor parameters through stall experiment and no-load test. However,they are not easy to perform, because of the site conditions. This paper uses an offlineidentification method based the inverter-motor system. Before the motor running, thecontroller executes a recognition program, imposing specific incentives for motor. Byanalyzing the response of the motor can get the motor parameters.During the operation the motor parameters change can affect the performance ofthe vector control. The static and dynamic performance impact caused by the change ofrotor time constant is analyzed through theoretical and simulation, which clarifies theimportance of parameter identification. In order to suppress adverse affect on theperformance of vector control system caused by parameter changes, paper identify therotor time constant online using the method of model reference adaptive. The key of thismethod is that the selection of model the determination of the adaptive law. Combined with the motor rotor flux model, using Popov stability theory a rotor time constant rotorflux model based identification method is derived, which is easy to implement, but itsthe accuracy is affected by the stator resistance and pure integral part of the subject. Tosolve this problem, the paper studied the reference model containing only one statorvoltage and current. This method overcomes the shortcomings that model referenceadaptive method greatly depends on the motor parameters and does not recognize theparameters of light loads at low speeds. Then the two methods are simulated in theMATLAB/Simulink environment, the results prove the correctness and feasibility of themethod.Experimental system uses TI DSP chips produced TMS320F28035as the core todesign hardware control system and applies C language and modular programming wayto design software control system. Then complete the software design and debug inCCS3.3environment. The effectiveness of the system designed in this article is verifiedby experimental results. Finally, the experimental results are analyzed, and made furthersuggestions for improvement.