08-16-2017, 09:01 PM
Presented by:
G.SIRISHA
V.PRATHIBHA
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Abstract
Direct Torque Control (DTC) is quite different from vector control and has several advantages compared to vector control. This paper presents intelligent control scheme together with conventional control scheme by fuzzy logic approach, to overcome the problems with uncertainties in the structure encountered with classical model based design. To adjust the speed of the direct torque control of induction motor drive, a fuzzy state feedback controller is proposed based on the pole placement technique. Simulation studies have been carried out for different operating conditions of the drive system, the results have been presented and compared with those of the conventional method. Key words: Induction motor, direct torque control, fuzzy logic.
Introduction
, which has , which les Induction motors are characterized by complex, nonlinear, time-varying dynamics and inaccessibility of some states and outputs for measurements. In field oriented control of induction motor, stator current is divided into torque and flux producing components. These components are controlled in a fashion similar to that of a separately excited dc motor. Because of the transformations, this method is complex. To simplify the control strategy, in 1986 DTC was reported . In conventional DTC optimum voltage vector is selected from the switching table based on the flux and torque errors. As this method does not involve with any transformations, this method was widely accepted by industry. Industrial applications exhibit significant nonlinearities, mainly the rotor resistance, vary with the operating conditions and performance may deteriorate if conventional controller such as PID controller is used. For these reasons it is worth developing controllers which have capability to handle not only linear but also nonlinear as well as ill defined systems Hence, intelligent control systems combining conventional control techniques such as state feedback controls with fuzzy logic leads to more effective control design with improved system performance and robustness . In this paper, to improve the drive performance, fuzzy state feedback controller is developed. These controllers are evaluated under simulations for a variety of operating conditions of the drive system and a comparative study of the PID and FSFC strategies are made and it is found that the fuzzy state feedback controller gives better results. s than one leaf