Research On Position Sensorless Control Algorithm Based On PMSM

Permanent Magnet Synchronous Motor has the advantages of compact structure,small torque ripple,high power density and good dynamic characteristics,so it is widely used in many fields such as household appliances,aerospace,new energy vehicles,etc..In order to achieve high-performance control of permanent magnet synchronous motors,it is necessary to obtain speed or position information to form a closed-loop feedback loop.The use of mechanical position sensors will increase system volume,increase costs,make maintenance difficult,and reduce system reliability.The sensorless control technology estimates the speed or position information by detecting the electrical signals such as voltage and current during the operation of the motor.This is also one of the hot research directions in the field of motor control.This thesis comprehensively uses vector control scheme,high-frequency signal injection method,sliding mode observer scheme,etc.,and is committed to solving the problems of low estimation accuracy,complicated algorithm structure and difficult system design in the existing position sensorless control scheme.The main work is summarized as follows:(1)The difference between the two physical models of permanent magnet synchronous motors is analyzed,the main research object of this paper is determined as surface-mounted permanent magnet synchronous motors,the mathematical model of the motor in three common coordinate systems is deduced,the vector control(FOC)scheme with small torque ripple and mature engineering implementation is selected as the overall control strategy of the system,the specific implementation steps of the space vector pulse width modulation technology(SVPWM)in the core of the vector control scheme are derived.(2)When the motor is running under low-speed operating conditions,the formation principle of saturation salient poles of surface-mount permanent magnet synchronous motors is analyzed,so the traditional high-frequency pulse voltage injection method with external electrical signals is selected as the low-speed operating conditions The sensorless control scheme of the thesis deduces the basic principle of the traditional high-frequency pulse voltage injection method to estimate the motor speed or position,and analyzes the error of the traditional high-frequency pulse voltage method.The error mainly comes from extracting the current containing the motor position in the process of responding to the amplitude signal,the traditional extraction method does not consider the effect of the delay of the digital signal processing on the amplitude modulation link and the phase lag problem caused by the use of the low-pass filter.This thesis proposes the use of adaptive notch filter(ANF)is used to extract the current response amplitude signal containing the motor position information.This improved solution not only eliminates the amplitude modulation of the current response but also eliminates the use of low-pass filters,which improves the estimated accuracy of motor speed and position.Finally,under the Matlab/Simulink simulation environment,the traditional high-frequency pulse voltage injection method and the improvement scheme proposed in this thesis are compared and analyzed,which proves the effectiveness of the improvement scheme proposed in this article.(3)When the motor is running under medium and high speed conditions,the basic principle of estimating the motor speed or position using the traditional sliding mode observer scheme is derived according to the motor's back electromotive force model.Aiming at the “chattering” problem caused by the switching characteristics of the traditional sliding mode observer scheme itself and the phase lag problem caused by the use of low-pass filters,this thesis proposes the use of second-order sliding mode observation based on the super-twisting algorithm design(STASMO)scheme,this improved scheme not only effectively suppresses the "chattering" problem and also eliminates the use of low-pass filters.In view of the problem that the stator resistance change affects the observation accuracy of the STASMO scheme during the operation of the motor,a reasonable stator resistance observer is designed to observe the change of the motor stator resistance in real time,this scheme improves the estimation accuracy of the STASMO sensorless control scheme.Finally,under the Matlab/Simulink simulation environment,the traditional sliding mode observer scheme and the STASMO scheme with stator resistance observer proposed in this thesis are compared and analyzed,which proves the effectiveness of the proposed improved scheme.(4)In order to further verify the actual estimation effect of the position sensorless control scheme proposed in this thesis on the motor speed or position,the TMS320F28335 is used as the main control chip to build a position sensorless control experimental platform for permanent magnet synchronous motors.The experimental results prove the effectiveness of the improved scheme proposed in this thesis,the position sensorless control of the permanent magnet synchronous motor is realized on the hardware platform.