Research On Speed Sensorless Vector Control Of Induction Motors

Proposal and successful application of the vector control theory open the era in which DC (Direct Current) motor speed control system is replaced by ACIM (Alternative Current Induction Motor) speed control system.It stimulated the interest and enthusiasm of people to design AC speed control system with high performance. As the speed sensorless technology eliminates the need for speed sensor, it can reduce the complexity of AC speed control system and enhance the environmental adaptability of the system and reduce system cost. Therefore in recent years, the combination of speed sensorless technology and vector control technology became a research focus. Based on this, the thesis carries out an in-depth research on speed sensorless vector control system.The start-of-art and developments trends of the AC motor control theory are introduced and the concept of speed sensorless is compared and analyzed. The issue of the purpose and main contents of the research are also presented.In this thesis, the basic principles of vector control, vector coordinate transformation are presented. The mathematical model of induction motor and the flux oriented vector control system are discussed. Then the accuracy of flux observation is analysisd comprehensively, a combined model for flux observer is presented. Then the model reference adaptive control systems (MRAS) and the speed estimation methods based on MRAS are discussed. For the conventional model reference adaptive speed estimation method suffers from slow convergence and large estimation errors of low-speed, modified model reference adaptive speed estimation with variable parameters is proposed.Design a induction motor speed sensorless vector control system with TMS320LF2407 DSP chip as control core, introducing the system's main circuit, detection circuit, drive circuit, protection circuits and other hardware circuitry.Then the software design idea of the speed sensorless vector control system is introduced and the software of various modules are given.Finally, the system emulate modulations are constituted on the Matlab/Simulink simulation platform. Combined with model reference adaptive speed estimation theory and the vector control theory, the system simulation model is built. Simulation results show that, the speed estimation method based on variable parameter model reference adaptive control theory has fast convergence rate and high estimation accuracy, and the speed sensorless vector control system has a good dynamic performance and static character.