Research On Simulation For Improving Low-speed Performance Of Asynchronous Motor DTC System

After direct torque control technology was invented, it has been given wide concern and has got rapid development because of its original control notion, concise system structure and excellent capability on activity and immobility. On the other hand, DTC technology directly applies optimum control on the switch conditions of inverter and generates.In this paper, summary to the question that in the DTC the ripples of torque,current and flux are large,switching frequency is low and not fixed, we develop the following improving method: the application of the integrated torque regulation be composed of P/N regulation; the application of flux regulation at three levels, use of improved swithching tables; use of the new stator flux observer based on the low-pass filter is designed. Use of this method can not only improve performance of motor through decreasing the ripple of torque, flux and current but also improve capability on activity.At first this thesis introduces the basic principle of direct torque control on asynchronous motor. Through mathematics model of asynchronous motor stator flux and torque can be got. The model of simulink is designed. The keystone of this thesis is the solving project for improving low-speed section of Asynchronous Motor based DTC. The thesis point out the following project: To demonstrate the validity of the asynchronous motor's direct torque control system, simulation system of DTC is designed through the simulation software MATLAB/SIMULINK. The result of the test is analyzed. On the other hand, after changing the parameters in direct connection with flux- regulation and torque-regulation, this paper gives the effect of changing parameters to motor ability. The result of simulation expresses, this paper's standpoint is a good project for improving low-speed section of the asynchronous motor.The speed sensorless estimation is an important trend of modern AC drive. This paper has discussed several primary algorithm of speed estimation and emphasized on the algorithm of speed estimate based on model reference adaptive system. It will become the theoretics support during designing the speed-recive part of the really DTC.