Research On Sensorless Direct Torque Control Method Of Synchronous Reluctance Motor

As an energy conversion machine,electric motors are widely used in the fields of ships,warships,aerospace,electric vehicles,industrial production,and so on.Currently,China’s energy shortage is becoming increasingly serious.As a key equipment in the industrial production field,electric motors consume over 50% of the total energy consumption in industry.Therefore,exploring how to reduce the manufacturing cost of electric motors and improve their efficiency is of great significance for reducing industrial energy consumption,alleviating the energy crisis,and supporting the "dual carbon goal".In this context,synchronous reluctance motor(SRM)is considered an ideal motor for replacing asynchronous and permanent magnet synchronous motors in the industrial field due to its high efficiency,simple rotor structure,and low cost.There are two main driving schemes for synchronous reluctance motors: vector control(FOC)and direct torque control(DTC).The DTC method focuses on the feedback of torque and flux loops,with a simple control structure and good robustness,which is consistent with the characteristics of high torque response of synchronous reluctance motors.However,the current direct torque control schemes for synchronous reluctance motors mostly rely on position sensors such as photoelectric encoders to obtain rotor position information.However,in practical applications,the addition of position sensors can,on the one hand,make the size of the motor larger,make the wiring more complex,and even cause concentricity deviation issues.On the other hand,in environments such as high temperature and humidity,the observation accuracy of the sensor significantly decreases,which affects the reliability of the system.Aiming at reducing system cost and improving system reliability,this paper studies the direct torque control method for synchronous reluctance motors.Firstly,the operation principle of synchronous reluctance motor is described,and its mathematical models in different coordinate systems are constructed.After analyzing the problems of the position sensorless direct torque control scheme(SFM-DTC)based on the stator flux model,an improved sliding mode observer design is proposed to achieve position sensorless control,including a reaching law design of a segmented saturation function and an adaptive sliding mode gain design;A flux compensation strategy based on instantaneous power theory is proposed,which includes a flux angle compensation strategy based on instantaneous active power and a flux amplitude compensation strategy based on instantaneous reactive power;A stability analysis method for direct torque control of synchronous reluctance motors based on small signal model is proposed.After integrating the above theoretical analysis,a position sensorless direct torque control(SMO-FC-DTC)system for synchronous reluctance motors based on improved SMO and flux compensation strategy was obtained.Secondly,in order to verify the correctness and effectiveness of the proposed sensorless direct torque control scheme,this paper constructs corresponding models in the Simulink environment.In terms of starting performance,load disturbance resistance,and other aspects,the traditional sensorless direct torque control,sensorless direct torque control based on stator flux model(SFM-DTC)A detailed simulation test and analysis of position sensorless direct torque control(SMO-FC-DTC)based on improved SMO and flux compensation strategy were conducted.According to the simulation results,the proposed SMO-FC-DTC operates well under various operating conditions;Under medium and high speed conditions,SMO-FC-DTC is similar to traditional sensor-based direct torque control systems in terms of rise time and steady-state speed fluctuations,and effectively reduces steady-state speed fluctuations and steady-state errors compared to SFM-DTC;Under low speed and full load conditions,SFM-DTC cannot reach the given rotational speed and torque ripple is significant,while SMO-FC-DTC operates well under this condition,effectively improving the system’s load carrying capacity;In the anti load disturbance experiment,the speed fluctuation of SMO-FC-DTC after sudden loading and unloading is smaller,which is close to the traditional sensor-based direct torque control.Therefore,the proposed position sensorless direct torque control system based on improved SMO and flux compensation strategy has good dynamic and static performance.Finally,the software and hardware scheme of the sensorless direct torque control system for synchronous reluctance motors is designed,and the corresponding experimental platform is built.The code is compiled based on the Code Composer Studio software.Based on this experimental platform,the traditional sensorless synchronous reluctance motor DTC system,the sensorless synchronous reluctance motor DTC system based on stator flux model,and the sensorless synchronous reluctance motor DTC system based on improved SMO and flux compensation strategy were tested for starting performance and load disturbance resistance.Based on the analysis of experimental results,it can be seen that the sensorless DTC algorithm for synchronous reluctance motors proposed in this paper operates well under various operating conditions,and is similar to the sensorless DTC method for synchronous reluctance motors in terms of startup time,steady-state fluctuations,speed fluctuations after load impact,and recovery time.It is significantly superior to the sensorless DTC method for synchronous reluctance motors based on stator flux chain model,which can ensure that the position sensor can be removed Reduce system costs while ensuring good overall system performance.