PERFORMANCE INVESTIGATION OF INDUCTION MOTOR WITH DIRECT TORQUE CONTROL

Abstract

Induction motors are widely used in many industrial applications due to their mechanical robustness and low cost. However a draw back of induction machines is that precise torque control can not easily be achieved. In order to overcome this difficulty vector control of pulse width modulation (PWM) inverter fed IM drives which guarantees high dynamic and static performance has-been developed. The draw backs of this method are dependency on the rotor resistance value and computational requirements and time delay due to the use of current control loops and axes transformations. Direct torque control (DTC) has a relatively simple control structure yet performs at least as god as vector control technique. In the present work the Direct Torque Controlled induction motor drive operating principle is briefly studied and the various forms of direct torque controlled induction motor drives that are reported in literature have been reviewed. The implementation of simulation of the drive is done using MATLAB/SIMULINK toolbox with a speed sensor and without speed sensor. The implementation aspects of the simulation and the obtained results are discussed. The drive simulation is done for starting from rest, sudden changes in load torque, speed reversal and the speeds above the base speeds operating the induction motor in the field weakening region. A hybrid fuzzy controller for direct torque control induction motor drive is also presented. The features of the presented hybrid fuzzy controller will be highlighted by comparing the performance of various control approaches, including PI control, PI-type fuzzy logic control (FLC), proportional-derivative (PD) type FLC, and combination of PD-type FLC and I control, for DTC-based induction motor drives.