Research On The Position-Sensorless Operation Of Surface Permanent Magnet Synchronous Motor At Full Speed Range

Permanent magnet synchronous motor has the advantages of high efficiency,high power factor and wide speed regulation range.It has been widely used in rail transportation,aerospace and other fields in recent years.Compared with the traditional position sensor vector control,the position-sensorless control can reduce the volume of the motor system,reduce the cost,and improve the reliability of the system.In this article,the surface permanent magnet synchronous motor is studied.The algorithm of controlling the motor operation without position sensor in the whole speed range is studied.The main contents are as follows:In order to avoid the phenomenon of overcurrent or motor reversal when the position-sensorless algorithm is input as much as possible,this dissertation uses the pre-positioning method to drag the motor rotor to the known position before the motor runs.For the positioning blind zone formed by the inherent torque of the motor bearing friction in the actual environment,a method of secondary positioning is studied to make the rotor smoothly avoid the blind zone and reliably reach the predetermined position.Two open-loop control strategies,V/f control and I-f control,are studied.The stability of the two open-loop control strategies is analyzed.The system damping is increased by correcting the voltage frequency or current frequency,thus improving the stability of the open-loop control.After frequency correction,both control strategies can drive the motor to run stably in the full speed range and have certain anti-interference ability.Starting from the steady state model of the motor,it is concluded that the two control methods are based on the respective power angle characteristic curves to find the steady-state operating point and the stable operation range of the two open-loop control strategies are derived.A comparative analysis summarizes the advantages and disadvantages of each.In order to realize high-performance control of surface permanent magnet synchronous motor in medium and high speed area,this dissertation designs an instantaneous switching strategy to make the motor smoothly transition to position-sensorless closed-loop vector control.By using the principle of double d-q space transformation and self-balancing of torque power angle,the switching strategy of V/f control and I-f control is unified,and the switching between open loop and closed loop can be realized.In this article,an improved model reference adaptive method based on stator current is used to estimate the rotor position and speed,which realizes the high efficiency operation of the motor in the medium and high speed region.Based on theoretical analysis and Matlab/Simulink simulation research,the experimental verification of the surface permanent magnet synchronous motor on the tow platform is carried out.The experimental results show that the open loop control described in this article can smoothly start the motor and make it run stably at a given frequency.The switching strategy can smoothly complete the switching between open loop and closed loop.The position control algorithm has higher estimation accuracy and good dynamic performance.