Research On Speed-sensorless Vector Control System For Asynchronous Motor

With the development of modern power electronics and control technology based on computer, the technical revolution of electrical drive is promoted. It is a trend that AC drive replaces DC drive and computer-aided digital control takes the place of traditional analog control. The speed-sensorless vector control of asynchronous motor has become a focus gradually as an important approach direction in modern alternating current machine control.The thesis made a study on the speed-sensorless vector control system. Firstly, it is summarized that the progress of control strategies of alternating current motor and speed-sensorless vector control technology in recent years. What's more, the advantages and disadvantages of different strategies are enumerated and compared. Then, the principles of vector control, coordinate conversion and space vector pulse modulation (SVPWM) are expounded; Mathematical models of asynchronous motor in different coordinates are introduced, which offers theoretical foundation for further research on the speed-sensorless vector control system for asynchronous motor. Secondly, it discusses two kinds of speed identification method which based on model reference adaptive system (MRAS) and full order speed adaptive observer in detail, Then give real-time identification for the stator and rotor parameters in order to improve the dynamic and static performance. The simulations of speed-sensorless vector control system based on model reference adaptive system and full order speed adaptive state observer are realized in MATLAB/Simulink, and the simulation results are analyzed and compared. The results of the simulation show that the two kinds of speed-sensorless vector control systems for asynchronous motor are both effective and rational. The speed estimation of full order speed adaptive rotor state observer is more accurate than MRAS, because the error-corrected loop is used. According to the above, I have modified the hardware and software in the elevator door-motor control system and designed a speed-sensorless vector control systems, experiment proves that the system is feasible. The system mainly includes the main circuit, the detection circuit, the control circuit, the human-machine interface circuit, the protection circuit and the power circuit.Finally, the paper is summarized and gives the analysis and prospect for the future research.