Study On Direct Torque Control Of Induction Motor Based On DSP

Direct torque control(DTC) was brought up by Professor Depenbrock in 1985. It is now as important as the vector control of induction motor. DTC have the advantages of simple control idea and good stable and dynamic performance. However, as a kind of the new theory and technology, it has some imperfect aspects. Owing to the reasons above, DTC has become one of researching hot points. In order to sustain the rapid response of DTC and overcome the flux and torque ripples, the dissertation studies the theory of DTC.First, the dissertation analyses the physical model of induction motor. And according to Park transformation and the characteristic of direct torque control, a suitable mathematical model of induction motor is given out. And the traditional DTC theory is analyzed and discussed.Secondary, after the analysis of traditional DTC, the dissertation designs a modified DTC scheme. The working state of induction motor is divided into several states, and different control schemes are applied to different states. In transient state, traditional DTC scheme is applied, which is in order to sustain the rapid response. In stable state, the stator voltage is modulated by SVPWM, which enables the precise control of the state of induction motor. And meanwhile the trace of stator flux is kept in a circular, in order to diminish the ripple of flux and torque. Therefore, a divided state DTC is derived.In the basis of theoretical analysis, Matlab is used to do simulation research of the designed DTC scheme. The simulation results show that the scheme is correct in principle.Finally, based on TMS320F2812 DSP, the digital implementation is accomplished. A lot of experiments are taken on experiment platform, which verified its validity. By analyzing the experiments'result, the following conclusion can be derived: the improved DTC scheme can both preserves the feature of rapid dynamic response and reduces the ripple of flux and torque.