Research Of Key Technology Of Permanent Magnet Synchronous Motor Sensorless Control System

Permanent magnet synchronous motor has many advantages either in structure or in performance. That makes it the inevitable trend of the development of electric drive motor drive. In the high performance of the permanent magnet synchronous motor control system, the information of rotor position and speed is indispensable to realize high precision control. Usually, the information of rotor position and speed can be measured by installing mechanical senor. But the sensor will bring a series of problems such as difficult to install, maintenance, high cost and low reliability. And in some special conditions, it is impossible to use sensors. To solve the problems above, sensorless control technology has become the current research hotspots in the field of electric drive.The research status of permanent magnet synchronous motor sensorless control system is reviewed. The equivalent circuit and mathematical model of permanent magnet synchronous motor are established by analyzing the structure and characteristics. The principle of sensorless vector control of permanent magnet synchronous motor is expounded. Several kinds of permanent magnet synchronous motor vector control strategy and rotor position estimation method are introduced as examples. Through the study above, most of the rotor position estimation method based on the motor back electromotive force cannot work properly at low speed due to the back electromotive force is too small. So this paper will focus on the rotor position estimation method suitable for low speed (zero speed), high frequency signal injection method.First, the mathematical model of permanent magnet synchronous motor under high frequency excitation is established. The principle and the design method of observer of rotating frequency voltage injection and pulsing high frequency voltage injection are analyzed. The simulation models of two kinds of high frequency signal injection method are established by using Matlab software. The two methods are analyzed and compared through the simulation results.Second, a sensorless hybrid control system of surface-mounted permanent magnet synchronous motor is designed. Pulsing high frequency voltage injection method is used at low speed and the initial position detection, back EMF method based on PLL is used at high speed. The principle, signal processing and the design of the observer are introduced. And a hybrid observer is designed to realize the switching of the two methods. The feasibility of this method is confirmed by analyzing the simulation results.Finally, the experiments are carried on the permanent magnet synchronous motor experimental platform. The presented method of theoretical analysis and simulation results are verified by analyzing the experiment results.