High-speed Permanent Magnet Synchronous Motor Without Position Sensor And Low Carrier Ratio Control

Permanent magnet synchronous motor(PMSM)has the advantages of wide speed range,high power density and small size.It is widely used in aerospace industry,intelligent manufacturing industry and transportation industry.Vector control method is widely used in the field of motor control because of its high precision and high efficiency.In order to achieve accurate closed-loop control,the rotor position and speed information must be collected in real time.The common method is to install photoelectric encoder or resolver on the rotor shaft for position sampling.However,the installation of mechanical position sensor will inevitably occupy the volume of motor system,which limits the application of permanent magnet synchronous motor in some special places.The sensorless control method only needs to sample the current and voltage signals,and the rotor position and speed information can be calculated by the corresponding algorithm.However,due to the low carrier ratio at high speed,the estimated position information has phase error due to various factors,and the motor parameters are easy to change at high speed,which has a great impact on the accuracy of rotor position estimation.In this paper,the working condition of high speed and low carrier wave ratio is taken as the research background,and the accuracy of position estimation by sensorless control method is studied,The main research contents are as follows.1.The sliding mode variable structure is analyzed in detail.In order to reduce the chattering problem of the traditional sliding mode observer,the sigmoid function is used as the switch function to observe the back EMF,and the phase-locked loop is used to extract the rotor position and speed information.2.In order to solve the problem of rotor position phase delay estimation under high speed and low carrier wave ratio,an angle compensation method based on d-axis discrete current is proposed.In this method,the error state between d-axis discrete current and d-axis given current is used to judge whether rotor position compensation is needed.When the error is not 0,it is considered that there is an angle error.When the error is near 0,the angle compensation is considered done.3.In order to solve the problem of motor parameters changing at high speed,an on-line parameter identification method based on discrete current error is proposed in this paper.The parameter identification method needs to wait for the angle compensation algorithm to complete.After the angle compensation algorithm is completed,if the d-axis current error is not zero again,then the motor parameters are considered to have changed.After analysis,only the inductance parameters can be considered When the current error is 0,the inductance value is recorded.It is considered that the inductance value at this time is the real inductance value of the motor and updated to the no position algorithm.