Research On Induction Motor Speed Sensorless Vector Control Strategy And Its Experiment

Speed sensorless vector control not only maintains the excellent performance ofvector control, but also overcomes the adverse effects of speed sensor, so it is apromising way to realize low-cost, high reliability and high performance AC speedregulation system, due to which it becomes a research focus of electric drives at homeand abroad. In this thesis, theories and related issues of induction motor speed sensorlessvector control are researched in depth. Speed estimation theories, motor parametersoff-line identification methods, and inverter nonlinearity error compensation strategiesare analyzed, and also verified by simulations and experiments.Vector control theory and the speed estimation principle are two theoretical bases ofspeed sensorless vector control. In this thesis, vector control theory is described, on thebasis of which an induction motor slip vector control system structure is designed out.Adaptive state observer is the selected scheme for speed estimation, and a full-orderadaptive flux observer model of induction motor is built. On the basis of Lyapunovstability theorem, speed adaptive law is derived as the adaptive institution. Then aninduction motor speed sensorless slip vector control system structure is designed out, thecorrectness and effectiveness of which is verified by simulations. Simulation ofparameter sensitivity is also done with stator resistance as the deviation parameter, on thebasis of which system robustness to parameter changes is analyzed.An off-line motor parameters identification method is given, which can effectivelyeliminate the effect of dead time on the accuracy of identification for stator resistance.During the process of identification, the current of motor is controlled to ensure securityof the system. And by simulations and experiments, the identification method proveshigh accuracy. Nonlinear error of inverter output voltage can affect estimation for speedand flux, so a compensation strategy on the basis of the average deviation voltage isgiven. In the strategy the calculated angle of current vector is used to determine the current polarity, and the output voltage deviation is compensated by correcting commandvoltage. Simulations and experiments are done for the compensation strategy, the resultsof which show that the strategy is correct and effective.A physical experiment platform of speed sensorless control system is built withTMS320F2810DSP as its controller. Control system experiments and parametersensitivity experiments are done, the results of which confirm the correctness andeffectiveness of the control strategies and also show some robustness for the system toparameter deviation, which has a certain guiding significance for the practical use andproductization for speed sensorless vector control.