26-05-2012, 02:57 PM
Mitigation of Disadvantages in Direct Torque Control of Induction Motor by Applying Fuzzy Logic
Mitigation of Disadvantages in Direct Torque Control.pdf (Size: 448.14 KB / Downloads: 61)
Introduction
Advantages of Direct Torque Control (DTC) over Vector Control:
Doesn’t requires coordinate transformation
Doesn’t requires PWM pulse generation
Doesn’t requires current regulators
Less dependent on machine parameters
Easy for implementation
Drawbacks of classical DTC
The speed regulators are conventional PI controllers (CPIC), which requires precise math model of the system and appropriate value of PI constants to achieve high performance drive. Therefore, unexpected change in load conditions or environmental factors would produce overshoot, oscillation of the motor speed, oscillation of the torque, long settling time and causes deterioration of drive performance.
The selected voltage vector is applied for the entire switching period, and thus allows electromagnetic torque and stator flux to vary for the whole switching period. This causes high torque and flux ripples.
fuzzy Logic PI Controller
Recently, Tien-Chi Chen. et al (2002) has proposed a speed control method for induction motor drives based on a two-layered neural network PI controller. However, the off-line training of neural network is very difficult and there is difficulty in real time control and its implementation.
When Fuzzy Logic is used for the on-line tuning of the PI controller, it receives scaled values of the speed error and change of speed error. Its output is updating in the PI controller gains based on a set of rules to maintain excellent control performance even in the presence of parameter variation and drive non-linearity.
The first part of this work replaces the conventional PI controller with FPIC which can adjust the gains of CPIC on-linefuzzy