Design Of Speed-sensorless Vector Control System For Induction Motor

There are three kinds of control methods of induction motor,which are direct torque control,constant voltage-frequency ratio control and vector control that have their own advantages and disadvantages,but compared with other methods,vector control has more obvious advantages,so it is widely used in the field of AC speed regulation in recent years.High performance vector control system is a closed loop speed control system.The premise of the speed closed-loop system is the accurate speed identification,the traditional speed identification method is to install the speed sensor and other components on the motor bearing,however,this method not only increases the cost,but also destroys the inherent characteristics of the motor,and the accuracy will be greatly affected in some special occasions,so it is very important to study the speed sensorless vector control.In this paper,the mathematical model of asynchronous motor in different coordinate systems,which consist of three-phase stationary coordinate system,two-phase stationary coordinate system and two-phase rotating coordinate system,is established,which is based on the derivation of vector coordinate transformation formula,and the basic principle of vector control is analyzed in detail.In addition,according to the principle of rotor magnetic field orientation,the control equation of vector control is obtained,and the decoupling of excitation current and torque current is achieved.Meanwhile,the basic principle of the space vector modulation(PWM)method is analyzed,and the formulas involved are deduced,and the concrete implementation steps are given.Then,the method of rotor flux observer in speed sensorless vector control system is introduced briefly,and advantages and disadvantages of different observation methods are analyzed,and the improved rotor flux observation model is given.The theoretical basis and basic principles of the model reference adaptive system are studied,and the model reference adaptive speed identification system based on rotor flux is designed,and adaptive law can be obtained by Popov stability theory,and the dynamic stability of system is also analyzed,and the basic principle of voltage reconstruction technology is given,which is the theoretical basis of model reference adaptive system.In summary,the block diagram of speed sensorless vector control system is established.Based on the above theoretical analysis,the sub module of the system is modeled in the simulation environment,the improved rotor flux based model reference adaptive system is simulated and verified,the hardware platform of the variable frequency speed regulation system based on TMS320F28335 is built,finally,the hardware circuit and software algorithm are briefly introduced.Based on the experiments of motor acceleration,deceleration,forward rotation,reverse rotation and loading,the response speed and tracking performance of identification speed in the motor speed adjustment process are observed,and compared with the simulation waveform,and compared with the simulation waveform,it is proved that the method has high accuracy and feasibility.