Vector Control Of Permanent Magnet Synchronous Motor By Using Single Current Sensor

In recent years,permanent magnet synchronous motors(PMSM)have been widely used in household appliances,industrial control,aerospace and other fields because of their high torque density,high power factor,high efficiency and high reliability.According to the basic theory of modern motor control technology,the motor driven by a double closed-loop vector control strategy has the characteristics of strong anti-interference,fast response and stable operation.To complete the vector control,it is necessary to obtain the motor rotor position and winding threephase current information in real time.This requires the use of position sensors and Hall-current sensors.The installation and use of physical sensors not only increases the size of the controller,but also increases the system cost.In order to reduce the number of sensors as much as possible,the thesis studies the phase current reconstruction technology based on single current sensor sampling,and combines the technology with the position sensorless control of the motor,and finally completes the vector control system design of PMSM using only one current sensor.Firstly,this thesis analyzes the traditional vector control method of PMSM using SVPWM algorithm,and describes the design method of current loop PI controller and speed loop PI controller.According to the specific parameters of the motor,the system model is established in Matlab/Simulink,and the simulation experiments of no-load start,speed regulation and sudden full load are carried out,which lays the foundation for the later study of phase current reconstruction under single current sensor sampling and vector control without position sensor.Then,the basic principle and implementation method of phase current reconstruction based on the inverter DC link current sampling are introduced.In the actual control system,the action time of some voltage vectors is too short,and the current sampling will fail,which leads to the problem that the current reconstruction has a dead zone that needs to be improved.This thesis focuses on the analysis of pulse shift method to reduce the blind area of current reconstruction.By comparing the current reconstruction error and performing a spectrum analysis on the reconstructed current,it is concluded that the complete three-phase current obtained by the improved scheme is more practical.According to the results of theoretical analysis and simulation,the pulse shift method still has the problem of high harmonic distortion rate of the reconstructed current waveform in the low modulation ratio region.Aiming at this problem,this thesis also studies the phase current reconstruction method based on the Zerovector sampling method,which solves the problem that the current reconstruction effect in the low modulation ratio region is not good enough.However,the use of the Zero-voltage sampling method needs to change the installation position of the single current sensor,which brings the problems of changing the wiring of the inverter branch line and redesigning the overcurrent protection.Therefore,it is necessary to select one of these two improvement schemes according to the specific application scenarios.Finally,in order to further reduce the number of physical sensors,this thesis studies the position sensorless control technology based on sliding mode observer(SMO).By modifying the sliding mode control function,designing an adaptive back-EMF observer and using phaselocked loop technology to extract rotor position information,the chattering phenomenon caused by the use of traditional SMO is reduced,the speed estimation error is reduced,and greatly improved the observation effect of SMO on motor rotor position information.This thesis also proposes a combination of the current reconstruction algorithm based on pulse shift and improved SMO sensorless control technology,and an integrated system model is established in Simulink.Through the simulation experiments of full load starting,changing speed and sudden unloading load,the simulation results of motor speed,stator current and electromagnetic torque are analyzed to verify the feasibility of the PMSM vector control system designed in this thesis.