The Study Of Application Of DTC Technology In AC Drive System

Direct Torque Control (DTC) technology is another new control thought after vector-control technology. It has direct control methods, rapid response system, excellent static and dynamic characteristics and the system's robustness is good, so DTC has been widely studied and has achieved rapid development.This paper presents the development of AC speed regulation technology and then analyzes the basic principle of induction motor direct torque control. It deduces u-i and i-n two kinds of flux linkage models, and the proper area and features of these two models are analyzed, then a u-n model which is suitable in the range of all speed .The u-n model features: using i-n model in the low speed and u-i model in the high speed range. The transition between low speed and high speed can be smooth, as the current regulator can compensate the observed current, the precision of the observation is raised greatly.Then take exchange electric locomotive as the example, this paper introduced the application of direct torque control technology in the exchange velocity modulation system. Based on traction characteristics of electric locomotive, it has designed the different torque control strategies:(1) Direct torque control with circular stator flux in the low-speed range.(2) Direct torque control with hexagon stator flux in the high-speed range.(3) The torque is adjusted by setting different references of the stator flux in weaken flux area. The system power is invariable.Simultaneously with the application MATLAB/SIMULINK software, it has established the direct torque control system simulation model, has obtained the simulation result and has confirmed the accuracy of this method.Finally, non-velocity generator direct torque control method is presented. The thesis deduces the identification method of rotor speed based on model reference adaptive system (MRAS). The simulation model is set up and the results are also given.