Research On Position Sensorless Control Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motors have the advantages of simple structure,large power density,high efficiency,reliable operation,and are widely used in the field of AC drives.Position sensorless control technology eliminates the use of mechanical position sensors,which can reduce the system costs,improve the system reliability,expand the product applications,and is of great significance in promoting the use of permanent magnet synchronous motors and promoting the development of China's permanent magnet industry chain.This paper focuses on the application of surface-mounted permanent magnet synchronous motors in compressors,fans,and pumps.The main contents are as follows:An improved sliding mode observer has been studied.The sinusoidal function with the variable boundary layer thickness was used as the switching function to effectively suppress the chattering phenomenon in the system;the back-EMF-normalized orthogonal phase-locked loop was used to extract the rotor position and speed information,which improves the system's resistance to high-frequency interference,and simplifies the parameter design;At the same time,the on-line identification of stator resistance was introduced into the sliding mode observer to reduce the influence of stator resistance changes on the observation accuracy.Using the improved sliding mode observer,the rotor position and speed of the motor can be accurately estimated in the mid-high speed.Aiming at the problem of low identification of the sliding mode observer at low speed,a position sensorless startup method for permanent magnet synchronous motor was studied.The secondary positioning method was used to preposition the rotor;Using the I/F control mode with speed open loop and current closed loop starts,can effectively avoid the over-current and out-of-step fault phenomena during the startup process;A transition strategy from I/F control to vector control with speed and current double closed loop based on sliding mode observer is designed,which can realize the smooth switching between the two control modes.With TI's TMS320F28335 as the main control chip,a permanent-magnet synchronous motor vector control hardware and software platform was built,and the experimental control scheme was verified by experiments.The experimental results show that the designed control scheme can ensure the smooth and reliable startup of the system,smoothly switch to double-closed-loop vector control without impact,and the system has good dynamic and static performance under the double closed-loop vector control mode at medium and high speed.The rationality of the design scheme was verified,and has great application value.