The Research On Direct Torque Control System Of Induction Motors With Speed Sensorless

Recently with the development of power electronic techniques,computer control techniques and automatic control techniques,many kinds of inducdion motor control techniques are improved greatly .Among them the Direct Torque Control (DTC) technique attracts more and more attention after vector control theory because of its robust characteristics, simple realization and excellent dynamic response. Direct Torque Control takes the parameter of torque as its control control object, and it based on stator coordinate. As a result,DTC system is a fected by fewer parameter of the motor and has less complex structure and fewer calculations. Since it was brought forward, Direct Torque Control has been taken serious attention by domestic and foreign scholars.At first this paper expounds the basic theory of DTC, then introduces the components of DTC system when the flux locus is round.The emphasis is to introduce the methods of how to calute and control the flux and the torque.Sensorless speed recognization can increase system redundancy effectively and can reduce the hardware design complexity. Nowdays many scholars devote themselves to research the Speed Sensorless of DTC. Some methods of speed identification are explored in this paper.Among these mothods,the MARS is a better one .Lots of simulations are done under Matlab/Simulink.Simulation results prove the methods of MARS accurate.In order to obtain a high quality in the low-speed area of DTC system, a precision model of motor in the low-speed area is necessary of which a important parameter is rotate speed.In this paper, many factor of influencing the quality are analyzed deeply,and some methods to improve the quality in the low-speed area are prensented.At last, this paper designs all the hardwares and softwares of the sensorless speed system of DTC based on DSP.