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High Performance Speed Sensorless Induction Motor Direct Torque Control System

Posted on:2008-07-21Degree:MasterType:Thesis
Country:ChinaCandidate:X H LiuFull Text:PDF
GTID:2192360215485040Subject:Pattern Recognition and Intelligent Systems
Abstract/Summary:PDF Full Text Request
Direct torque control (DTC) is an advanced AC variable-frequency speed adjustment technique, for its simple structure, fast behavior and unsensitive to rotor parameters. As speed sensor increases the cost and spoils the simplicity and reliability of the system, the speed sensorless technique is a new focus of AC speed adjustment research. The thesis develops research on the improvement for the speed sensorless induction motor direct torque control system performance, its main works are as follows:In this thesis, the basic principle of traditional DTC system is analyzed firstly, and the basic simulation platform of DTC system is built. And then, the performance of traditional DTC system is analyzed in detail. For the drawbacks of traditional DTC, such as bad performance in low speed course and the variation of the inverter switching frequency, a novel DTC scheme based on space vector modulation (SVM) is proposed, which calculates the reference voltage vector in predictive algorithm according to the flux and the torque error and composes the reference voltage vector in a simplified synnetrical voltage vectors combination modulation technique, it improves the low speed performance and keeps the switching frequency constant. Because of its constant parameters, the general PI regulator can not satisfy high performance speed adjustment request, a novel fuzzy adaptive PI regulator is proposed, which using fuzzy controller to modify the PI parameter according to the speed error and its rate of change, it improves the speed control performance effectively. The speed identification scheme based on rotor flux model is modified in this thesis, the output filter is introduced to improve the performance of the pure integrator, and a parallel speed and stator resistance identification scheme is designed by using Popov's hyperstability theory, the influence caused by the stator resistance variation is eliminated by feedback the estimated stator resistance value to the system. Consequently, the precision of speed estimate is improved effectively.Based on the synthesis of the proposed improvement strategies in the dissertation, a high performance speed sensorless induction direct torque control scheme is proposed. The simulation model of the proposed system is built in the Matlab7.1/Simulink environment. Validity of the proposed scheme is verified by simulation results.
Keywords/Search Tags:induction motor, direct torque control, speed sensorless, space vector modulation
PDF Full Text Request
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