Research On Sensorless Control Technology Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motors(PMSM)have the advantages of small size,high power,large torque,etc.,so they have received extensive attention in the field of AC drives and industrial servos.Generally,in order to achieve high dynamic performance of PMSM control,it is necessary to install a mechanical sensor on the motor rotor shaft.However,the use of mechanical sensors often increases the volume,weight,and cost of the PMSM system,and the accuracy of the mechanical sensors is easily affected by harsh environments such as high temperature,which reduces the control performance of the system.In order to solve the above problems,improve system performance,and increase system reliability,PMSM sensorless control technology has become a research hotspot in the field of motor control.The specific research work of this paper is as follows:First,the basic structure and types of permanent magnet synchronous motors are introduced,and the mathematical models of permanent magnet synchronous motors in three different coordinate systems are given.Then the basic principle of vector control technology is explained,and the design process of space vector pulse width modulation strategy is given.Then,the principle of sliding mode variable structure control is introduced in detail,and a traditional sliding mode observer for medium and high speed sensorless control of permanent magnet synchronous motors is designed.Aiming at the chattering problem in traditional sliding mode observer,using the Super-Twisting algorithm,a Super-Twisting sliding mode observer is designed for the sensorless control operation of permanent magnet synchronous motors.Since the equivalent disturbance term in the Super-Twisting sliding mode observer is related to the stator terminal voltage,when the motor is running in a wide speed range,the equivalent disturbance term changes greatly,but the sliding mode gain in the Super-Twisting sliding mode observer is constant,as known from the stability conditions of the SuperTwisting algorithm,this may result in greater system chattering at low speeds,or the observer does not meet the stability conditions at high speeds,which resulting in system instability.In response to this phenomenon,an improved Super-Twisting sliding mode observer is studied.In the improved Super-Twisting sliding mode observer,the estimated motor back EMF is fed back to the input of the observer,thereby limiting the equivalent disturbance term to in a smaller range,reduce the influence of the constant sliding mode gain value on the sensorless control system in a wide speed range.In addition,considering that the temperature change will cause the stator resistance to change,which will affect the rotor position and speed estimation accuracy in the sensorless control system based on the motor model,a stator resistance online identification strategy based on the q-axis voltage equation of the permanent magnet synchronous motor is studied,which taking into account that the stator resistance can also be accurately identified when the motor is running in the power generation mode.Simulation and hardware-in-the-loop test results show that the improved Super-Twisting sliding mode observer has good estimation performance under a wide range of motor speeds,the system chattering is small,and there is no destabilization phenomenon.In addition,the studied stator resistance online identification strategy has good identification performance,and the identified stator resistance can quickly and accurately track the actual stator resistance.Then the nonlinearity of the inverter is analyzed,and considering that in the sensorless control of the PMSM based on the sliding mode observer,the given voltage of the inverter is usually used as the voltage input of the sliding mode observer instead of the actual output voltage.The voltage disturbance caused by the inverter nonlinearity will reduce the accuracy of rotor position and speed estimation.A disturbance voltage observer considering the uncertainty of motor parameters is studied to estimate the voltage disturbance caused by the inverter nonlinearity online and feed it back to the inverter input for compensating the nonlinearity of the inverter online.Simulation and hardware-in-the-loop test results show that the inverter nonlinear compensation strategy based on the studied disturbance voltage observer performs well.Finally,an experimental platform for sensorless control of PMSM is built,and the improved Super-Twisting sliding mode observer algorithm is experimentally verified.Experimental test results verify the correctness and effectiveness of studied the control algorithm.