Induction Motor Dtc System Simulation Modeling And Performance Improvement

Direct Torque Control (DTC) is a new method for AC motor speed regulating since Vector Control. It is based on stator static axis, has a simple mathematic model and realizes some high level performances, such as robustness to undulation of input voltage, low sensitivity to parameters' change etc. In recent 20 years, DTC developed rapidly, and was applied successfully in high power train driving system.The structure of DTC system is complex, so it's necessary to do simulation experiments in DTC theory research and before practical system developing. In this thesis, a good DTC simulation system is constructed based on MATLAB6.5/Simulink and S-Function programming. It provides a very good simulation platform for kinds of DTC strategies' researching.In traditional DTC, because of the stator resistance voltage and other factors, its control performance is not very good. And hexagon flux trace brings higher harmonic and does harm to the system. This thesis puts forward the control strategy, that in lower speed range using round flux trace, using -120° voltage and PI speed controller, to lower overshoot and improve dynamic performance; In high speed range, invaginated 18-angular flux trace DTC takes the place of hexagon flux, this method greatly reduces harmonic components in stator currents and doesn't make burden to controller and inverter. And, a flux model switch method without disturbance is carried out. Through deep simulation experiments, this control strategy shows satisfactory performances.