Research On Speed Sensorless Control Method Based On AC Drive

With the development of high-power converter technology, the improvement of controltheory and microcomputer control technology, and the mature converter technique, thealternating current (AC) drive system has also made a breakthrough. As induction motorspeed sensorless control method is an important research direction, it has gradually become aresearch hotspot. Due to the complexity of the mathematical model of induction motor itself,although the online speed estimation methods have many, but the accuracy of speedestimation could not get a better solution.Various existing speed sensorless control method has its own advantages anddisadvantages, but the scope of application themselves has some limitations. In order to solvethe problem, this dissertation focuses on the study about the speed estimation of inductionmotor speed sensorless control system. The specific contents are as follows:(1) AC drive technology and speed sensorless control technology are summarized, andthe difference and scope of application of various motor control strategies and speedestimation methods are generalized and compared.(2) The mathematical model of induction motor in the two-phase coordinate system isanalyzed and derived, and the basic principles of vector control are discussed. On these basis,the simulation model of vector control on induction motor speed sensor is set up byMATLAB/Simulink. According to the idle running and load of the motor, the simulationexperiments have done.(3) The thought of speed sensorless control technology has been analyzed and explained.Using model reference adaptive control (MRAC) method, and taking the flux equation asbasis model for speed estimation of the motor, the estimation of motor speed has been studied.The simulation results have verified the correctness of this method.(4) For the problem of speed estimation imprecisely based flux MRAC, and the problemof the jitter within the low speed range caused by the integrating element, the estimationmethod with the model of motor reactive power is employed to improve the accuracy andconvergence of speed estimation. The flux voltage model and current model are replacedrespectively by instantaneous reactive power and steady-state reactive power. Though speedsensorless vector control system simulation model, this experiment has simulated the load,speed changing and zero-crossing phenomenon during the actual operation of the motor. Thespeed estimation has one detailed analysis experiment.