The Speed Sensorless Control Of Asynchronous Motor Based On High Frequency Signal Injection Method

Speed sensorless vector control system of asynchronous motor abandons thephysical speed sensor, which not only reduces the cost of the system but also makesthe whole system more convenient, stable and reliable. It becomes one of the researchfocuses in the worldwide.The mathematical model and vector control methods of asynchronous motor areelaborated in this thesis. And basic principles and control method of the rotor fluxoriented vector control is thoroughly analyzed. Meanwhile, the controllability andobservability of asynchronous motor is studied and speed estimation adaptive rate ofthe model reference adaptive system based on Popov super stability theory is derived.Accurate and reliable information of speed is the prerequisite for safe, reliableand efficient work of the motor. On the basis of high-frequency signal injectionmethod as well as basic principles of asynchronous tachometer generator, a speedestimation method using high-frequency circulating current is proposed in this thesis.Compared with other high-frequency signal injection methods, it does not depend onnon-ideal characteristics of the motor and does not need to make any changes to thestructure of the motor. And this method has good versatility and practicality.Meanwhile, the proposed high-frequency circulating current method retains thecharacteristic of high-frequency signal injection method which is insensitive to motorparameters. And it improves shortcomings of high-frequency signal injection methodin the low speed, which broadens the range of speed estimation. Simulation resultsshow that the high-frequency circulating current method can achieve an accurateestimation of motor speed in a wide speed range, and has a quick dynamic response.On the basis of vector control system of asynchronous motor, speed sensorlesssystem simulation model based on high-frequency circulating current method isconstructed. Compared with the system simulation model based on model referenceadaptive method, results show that the proposed method has great robustness to thechanges of motor parameters and interferences from outside. The entire system has agood dynamic and static performance. Meanwhile, the effectiveness and feasibility ofhigh-frequency circulating current method are verified by the experimental platform.