Research On Online Parameter Identification Based On Vector Control System Of AC Motor

Vector control simulates asynchronous motor to DC motor by coordinate transformation, and realizes the decoupling control of flux and torque, so that AC motor can achieve the control effect of DC motor. Vector control system directed by the rotor field-oriented is based on rotor flux accurate observation, so the control system performance is affected largely by time-varying motor parameters. When motor parameters changes, especially when the rotor time constant changes, gross error of rotor flux observation will appear, stator current can't be decoupled completely, and the motor speed performance based on vector control will be affected seriously.The structure and working principle of vector control system are briefly introduced, the mathematical models of rotor time constant, rotor flux and torque are derived, the effects of the changed motor parameters on rotor flux observation is analyzed basing on the models, and the necessity of parameters identification is so proved; in the same time, the effects of AC rotor time constant on vector control is qualitatively analyzed, and the importance of rotor time constant identification is clarified.The model reference adaptive system is adopted here to identify the asynchronous motor rotor time constant online, and the ideal mathematical model of asynchronous motor in two-phase static coordinate is established. The adjustable model changed with rotor time constant is constructed, using above model as reference model, and the error equation of the adaptive system is derived. The rotor time constant adaptive law is designed basing on Liapunov stability theory, and the rotor time constant identification algorithm is derived.The online parameters identification method is applied to asynchronous motor vector control system, and the step response simulation and tracking performance simulation using Matlab/Simulink are completed. The results show that: the parameters identification algorithm possesses of ideal convergence speed, and good tracking performance. It can be proved that the parameter identification method can effectively track the rotor magnetic linkage, by analyzing the simulation results of the vector control system included rotor time constant online identification module. In a word, the study of this paper lays a foundation of theory and technology for AC motor speed high accurate control based on vector control system.