Study On Direct Torque Control Of Induction Motor Based On MRAS

With the high speed development of power electronics and computer technology, AC electricity transmission systems are replacing DC ones step by step. The typical technology for AC motor control has VVVF, VSVF, VC and DTC etc. Direct Torque Control (DTC) of asynchronous motors, which has been developed in the recent decades, is a power control method for motor drives. Following the vector control technique, the quick development of DTC makes itself a new high-powered Alternating Current(AC) driving technique paralleling to the vector control. The DTC system has many advantages such as simple realization and excellent dynamic response and perfect robustness etc. However, as a kind of the new theory and technology, it has some imperfect aspects. So the dissertation bring forward a DTC of induction motor base on model reference adaptive system(MRAS), and studies the theory of estimate rotor speed and stator resistance, also studies the theory of DTC.First, the dissertation analyses the theory of traditional DTC and MRAS, then using MRAS to slove traditional DTC's limitation. Bring forward a suitable mathematical model for DTC of induction motor base on MRAS.Secondary, the dissertation using MRAS to estimate rotor speed and stator resistacne. Then using MRAS to observer stator flux, calculate electromagnetism torque. Then divid the motor work state based on stator flux and electromagnetism torque, confirm the control method to stable and dynamic. 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. Then do experiments for the DTC of induction motor base on MRAS, By analyzing the experiments'result, the following conclusion can be derived: the improved DTC scheme based on MRAS can both preserves the feature of rapid dynamic response and reduces the ripple of flux and torque.