Induction Motor Direct Torque Control Of The Optimal Control Strategy

Direct Torque Control technology is developed as a kind of AC Driver in the 1980's. The model is analyzed in the stator coordinate, the stator flux space vector and electromagnetic torque as variables is controlled, the purpose is to control the electromagnetic torque directly, the method is more simple and rapid, and improve the dynamic response of the system further. However it is well known that DTC presents some disadvantages on flux linkage trajectory and torque ripple, especially bad performances at low speed in comparison with FOC,which makes difficulties in employment in industry application.Firstly, basic principles of traditional DTC based induction-motor were introduced. The simulation model of DSC strategy and approximate circle flux DTC strategy was established, and carried out a detailed analysis to the performance of both of systems.Secondly, as for many disadvantages like high current harmonics, torque ripples and variable switching frequency in conventional switching-table direct torque control scheme, the author propose a discrete space vector control strategy, which use double torque hysteresis comparators, synthesize new voltage vectors, detail the voltage vector switching-table and increase the sector. The simulation model of discrete space vector control strategy is built up by using Matlab7.1/simulink in order to verify the feasibility of the control systems theory. At the same time the simulation results are got.Finally, according to the requirement of DTC system based on the induction motor, the selection and hardware platform is designed. The page gave the software design processes. The design has a certain guiding significance to the realization of direct torque control program in practice.