Research On Flux Observation Methods Of Induction Motor

The induction motor has been widely applied in industry and agriculture due to its simple construction, high reliability and relatively low manufacturing cost etc. Thanks to mature application of a variety of electronic products and advanced control methods, induction motor speed control system also has rapidly developed.The vector control and direct torque control are two main methods of high performance alternating current drive system. The key of decoupling in the vector control is to obtain the accurate rotor flux information, similarly, the accurate stator flux estimation also plays an important role in the direct torque control. The flux observation plays a key role in high performance alternating current speed control system. The information can be obtained usually adopt the method of direct detection or indirect calculation, but the former is difficult for practical applications because of process and technical issues. Therefore, a lot of kinds of indirect calculation methods have been proposed, namely the flux observer method. In this dissertation the flux observation methods will be mainly studied.On the basis of the analysis and establish of the mathematical model of induction motor,firstly the integral problems in pure integrator of the voltage model flux observer have been analyzed on theory and verified in simulation, and three kinds of improved integral algorithms have been studied: modified integrator with a saturated feedback, with an amplitude limiter,with an adaptive compensation feedback. These improved integral algorithms have effectively solved the initial phase and input direct current bias problems of pure integrator. Then on the basis of further study of the strengths and weaknesses of the current and voltage model flux observers, a hybrid model flux observer based on a speed dependent function in combination with the advantages of both has been proposed, it has implemented the accurate flux estimation for all speed range, and high and low speed smoothly transits in the process of converting to each other. Finally, the sliding-mode control is used to design the flux observer,a high-order non-singular terminal sliding-mode flux observer has been proposed, a high-order sliding-mode control low has effectively eliminated the chattering phenomenon of conventional sliding-mode, a non-singular terminal sliding-mode surface has guaranteed the system convergence within finite time.The correctness and validity of the designed flux observation method has been verified by Matlab/Simulink in the induction motor simulation model and the vector control system of speed and flux closed-loop, and the simulation results are analyzed in comparison.