Research On Position Sensorless Control Strategy Of Permanent Magnet Wind Generator

The permanent magnet synchronous generator(PMSG)vector control system always needs to detect motor rotor position information.In the machine side converter control,the mechanical sensor acquires the rotor position and speed information of the wind generator.In order to avoid the use of such sensors and achieve high-performance control of permanent magnet wind generator,domestic and foreign scholars have proposed some sensorless control strategies for PMSG.This thesis will study the control theory and control strategy of permanent magnet wind generator position sensorless.Firstly,this thesis introduces the research status of sensorless technology for permanent magnet wind generator and reviews the research status of sensorless control at home and abroad,especially in the classification of rotor position detection technology.Focus on analyzing the key points and difficult problems of rotor position detection technology at this stage,Among the many difficult problems,it introduces high-precision estimation of the rotor position when the wind speed is abrupt and the initial position detection.The rotor position estimating method of permanent magnet wind generator is studied by sliding mode observer(SMO)combined with synchronous reference system phase-locked loop(SRF-PLL)method.This thesis introduces the variable structure control principle of SMO;the selection of switching surface and the design of control function;and it analyzes the cause of the error in SMO application in rotor position estimation.The thesis introduces the working principle of SRF-PLL and analyzes the reason for its error in position estimation.it is set up that the sensorless control simulation model of SMO combined with SRF-PLL.The simulation proves the advantages and disadvantages of this method in the rotor position estimation method.Secondly,the rotor position estimation method for SMO combined with SRF-PLL has problems such as low rotor position estimation accuracy when the wind speed is abrupt.This thesis proposes a permanent magnet wind generator rotor position estimation method based on finite position set phase-locked loop(FPS-PLL).The iterative function is designed to eliminate the PI tuning process of SRF-PLL.The cost function is designed to aid observer cancellation the back electromotive harmonics.This method effectively reduces the rotor position estimation error when the wind speed is abrupt,and effectively improves the estimation accuracy of the entire sensorless control system.The simulation and experimental results show that the method can quickly track the rotor position and speed information when the wind speed is abrupt,the speed tracking setting time is reduced by 63%,the position error estimation is below 0.03 rad,and it has good dynamic and static performance and higher estimation accuracy.and effectively improves the estimation accuracy of the entire sensorless control system.Finally,aiming at the SMO-based rotor position estimation method has a problem of large rotor speed tracking error when PMSG works in zero speed and low speed.This thesis studies the rotor position estimation method of permanent magnet wind generator based on pulsed high frequency injection method.It sets up the system structure of rotating high-frequency voltage injection method and pulse high-frequency injection method,and detailedly infers the mathematical model.The thesis combines the rotating high-frequency injection method with the FPS-PLL method to design a full-speed range composite observer.A weighted mean method is proposed for smooth cutover the two methods.The simulation model verifies the effectiveness of the method.Finally,this thesis achieves a high-precision estimation of the rotor position when the permanent magnet wind generator is running in full speed range.