Study On Position Sensorless Vector Control Of Low Speed Direct Drive Permanent Magnet Synchronous Motor

Permanent Magnet Synchronous Motor(PMSM)has the advantages of light weight,small size,compact structure,high torque/inertia ratio and wide speed range.It has been widely used in household appliances and industrial control in recent years.PMSM uses position sensor to obtain the position information of the rotor.However,considering the cost,volume,mechanical structure and operating environment,the use of position sensorless control technology has important significance and application value for the research of motor speed control system.The startup of PMSM and low speed operation are major problems with position sensorless control.The first step is to establish a mathematical model,including the voltage equation,the mechanical motion equation,and the electromagnetic torque equation.The second step introduces the basic principles of the PMSM vector control method and compares and determines the vector control strategy.Finally,the basic concepts and applications of the rotating high-frequency voltage injection method and the pulsating high-frequency voltage injection method involved in PMSM at low operating speed are introduced in detail,and the advantages and disadvantages of the two methods are compared.The pulsating high-frequency voltage injection method is used to construct the mathematical model,and the simulation analysis is performed to finally determine the injection voltage and the frequency.The initial position detection of the PMSM rotor is critical to the smooth start of the motor.Rotating high-frequency voltage injection and pulsating high-frequency voltage injection are commonly used to detect the initial position of the rotor at rest without a position sensor.The basic principle of saturated salient pole characteristics and the PLL rotor position estimation method are studied.Proportional-Integral(PI)observers and Extended State Observer(ESO)are introduced and their parameter tuning is studied.Methods,the simulation module was built under MATLAB/Simulink to compare the two methods and the two observers.Finally,according to the relevant theory of pulsating high-frequency voltage injection method,the pulsating square wave voltage injection method is used to estimate the position and speed of the motor rotor to realize the position sensorless control of the low-speeddirect-drive permanent magnet synchronous motor.After deeply understanding the basic working principle of the method,the PI observer is used to realize the position sensorless control from start-up to low-speed operation.Through a series of comparative analysis of simulation results,it provides a basis for research and confirms the feasibility of the scheme.