Investigation Of Sensorless Control System For Permanent Magnet Synchronous Motor

With the improvements of power-electronics, motor body design, microprocessorcontrol and large-scale integration(VLSI), the electric driving technology has made a rapid development. In the current field of electric transmission, the permanent magnet synchronous motor has become more widely available due to its advantages of small size, high power density, reliable operation, wide speed range and so on. Because the position sensor in the control system of permanent magnet motor has mainly some shortcomings such as difficult installation, high price and low reliability, the research of no-sensor control technology of permanent magnet synchronous motor appears particularly necessary. The sensorless control for permanent magnet synchronous motor in high-speed phase achieves good control effect presently, but a lot of problems exist in low and start-up phase. Therefore, the control technology for permanent magnet motor during low speed and start-up phase were studied by applying high frequency signal injection method. The main contents are listed as follows:(1) The mechanism of high-frequency signal injection method was analyzed in detail on the basis of mathematical model of permanent magnet synchronous motor, focusing on the filter, position observer and the compensation of estimated position angle. The simulation results show that the rotor position with low speed can be well tracked by the rotating high-frequency signal injection method, which has good behaviors on anti-turbulence and dynamics.(2) The magnetic saturation characteristics of the permanent magnet synchronous motor were analyzed in detail, and the mathematical model of flux linkage saturation was derived. A novel method to detect the initial position abroad was compared to the traditional method, and the respective simulation system was built for discussion. The simulation results show that the two methods both have good performance in detecting the initial position, but great differences in the scope of application as well as the difficulty of implementation.(3) A sensorless control experimental device based on the rotating high-frequency signal injection method was designed for permanent magnet synchronous motor. Some key technologies during the testing process were studied in depth. Experimental results show that the sensorless control for permanent magnet synchronous motor has good static and dynamic characteristics at low speeds and start-up phase by using the high-frequency signal injection method.