Research On Sensorless Vector Control Of PMSM Based On Fractional Sliding Mode Observer

The magnetic suspension energy storage flywheel system has been widely studied in the field of energy storage due to its high power density,wide application range and long service life.As one of the most important parts of the system,the control quality of flywheel motor is related to the performance of the whole system.Permanent magnet synchronous motor(PMSM)is favored by many researchers because of its simple structure,high efficiency and low loss.In general,PMSM drive control requires the use of position sensors to obtain rotor position and speed information,but the installation of position sensors will increase the cost of the control system and may reduce the reliability of the system.Therefore,sensorless control technology of PMSM has important research significance and broad application prospect.This paper mainly studies sensorless vector control system of PMSM based on improved sliding-mode observer.The main contents are divided into the following parts:In the first part,the mathematical models of PMSM in various coordinate systems and the coordinate transformation between the coordinate systems are mainly studied.Then the basic principles of space vector pulse width modulation technology and the implementation of SVPWM algorithm are studied.A vector control system model of PMSM is built on the MATLAB l Simulink platform.The built models include a current loop controller,a speed loop controller,a coordinate conversion module,and a voltage vector control module.The parameter tuning method of PI regulator in current loop and speed loop is also given.Through simulation experiments,the effectiveness of parameter tuning of the PI regulator is proved.It lays the foundation for the following research on sensorless vector control of PMSM.In the second part,the application of improved sliding mode observer in sensorless vector control system of PMSM is introduced.Because the sliding mode observer is not sensitive to parameter changes and external disturbances,it is used to estimate the back EMF of the motor,estimate the rotor speed,and extract the rotor position information by using the arctangent function method.Through simulation experiments,it is verified that the sensorless control of permanent magnet synchronous motor can be realized by using sliding mode observer instead of mechanical sensor,and a better control quality can be obtained.In the third part,the design of fractional order sliding mode observer and its application in sensorless vector control system of PMSM are described.Based on the theory of fractional order calculus and the sliding mode observer,a new kind of improved fractional order sliding mode observer is proposed.Firstly,the fractional differential operator is introduced into the sliding mode switching surface,and the exponential approach law is used to establish the fractional order sliding mode observer.Then the smooth continuous hyperbolic tangent function is used to replace the traditional sign function.Finally,the stability condition of Lyapunov is obtained by analyzing the stability of the observer.The simulation results show that the fractional order sliding mode observer can reduce system jitter,improve the accuracy of rotor position and speed estimation,and is robust to load fluctuation.In the fourth part,the sensorless vector control system of PMSM based on sliding mode observer is tested on the control platform of magnetic levitation flywheel energy storage system.The hardware part takes DSP28335 as the control core to build the hardware platform.The software part introduces the flow of the control system software design and gives the flow chart of the main program of the system and the PWM interrupt program.Aiming at the problem of estimation Angle deviation of sliding-mode observer when flywheel motor is running at high speed,the improved sliding-mode observer proposed in this paper is verified on this experimental platform,and it is proved that the improved sliding-mode observer can effectively improve the accuracy of rotor position and speed estimation.