Position Sensorless Control Of Synchronous Reluctance Motor Based On Improved Sliding Mode Observer

As a motor driven only by reluctance torque,synchronous reluctance motor has great advantages in cost,speed regulation range,operation efficiency and loss.Nowadays,with the rapid development of power electronics technology,synchronous reluctance motor has attracted a lot of attention at home and abroad.In order to achieve high-precision position and speed control,mechanical position sensors are often used to measure the motor rotor position and speed.However,this method has many problems,such as reduced power density,inaccurate measurement,large occupation volume,difficult maintenance and repair in the later stage,which are criticized by people.The corresponding position sensorless control can be applied to many occasions with higher requirements.In this paper,a sensorless control strategy of synchronous reluctance motor based on improved sliding mode observer is proposed,which can effectively suppress the sliding mode chattering and observe the rotor position and speed in a wide speed domain.Firstly,the paper expounds the background and research significance of the subject,and summarizes the research status of synchronous reluctance motor and its sensorless control technology at home and abroad.The model of synchronous reluctance motor and the principle of vector control are explained.Considering the obvious magnetic circuit saturation phenomenon in the operation of synchronous reluctance motor,which makes the motor inductance change nonlinearly with the stator current,in order to realize the accurate control of the motor,this paper constructs the finite element simulation model of synchronous reluctance motor,measures the nonlinear off-line inductance of the motor,and establishes the current inductance query table.At the same time,the calculation of three-phase modulation wave of SVPWM is also described.Secondly,based on the idea of "quasi sliding mode" and "boundary layer",this paper designs a piecewise exponential saturation function to exchange the sliding mode control rate function SGN in the traditional sliding mode observer,and adjusts the sliding mode gain coefficient through fuzzy control to optimize the traditional sliding mode observer,so that the sliding mode chattering can be effectively reduced when the sliding mode surface approaches the origin,Improve the accuracy of observation results.At the same time,in view of the poor observation effect of the sliding mode observer in the low-speed section,the rotating high-frequency voltage injection method is used as the supplement of the position observation,and the smooth switching of the two observation methods is realized in the speed switching domain based on the specific gravity rule.The simulation modeling is carried out in the simulation software MATLAB/Simulink.Through the simulation,it can be concluded that the control strategy has good position and speed tracking effect.Finally,in order to further verify the effectiveness of the control strategy proposed in this paper,a sensorless control experimental platform based on DSP control chip TMS320F2812 is built,and the hardware and software are designed and written.The experimental verification and analysis show that the improved sliding mode observer method effectively reduces the sliding mode chattering and realizes the accurate observation of the position and speed of the high-speed rotor in the motor.At the same time,it also has a good observation effect for the low-speed stage and the combined control stage.