5.1.1 DIRECT TORQUE CONTROL
Direct torque control with duty is purposed as one of the best controllers for driving any induction motor. Its main principles have been introduced and explained in detailed. It is also proved in this work that the method of DTC also allows the independent and decoupled control of motor torque and motor stator flux. It is apparent that DTC strategy is easier to implement than the flux vector control method because voltage modulators and coordinate transformation are not needed, although it introduced some drawback being the high magnitude of torque ripple.
5.1.2 Direct torque control with duty ratio fuzzy controller
After all the simulation, this work focused on introducing a modulation in the DTC. A fuzzy logic controller is in charge of controlling this modulation between the selected active state and a null one.
Therefore it has been suggested and deeply described the fuzzy logic controller, which together with the DTC will create the fuzzy logic DTC.
Finally, the theoretical claim that duty ratio control can reduce torque ripple in DTC control gave acceptable results and reduces the computation burden by skipping unnecessary complex mathematical modeling of the nonlinear systems. By using duty ratio control, a particular motor performance can be achieved at a lower switching frequency compared to the conventional DTC, which in turn increases the performance of the drive by reducing the flux harmonics.
All recommendation is summarized schematically in the following ideas:
• To develop a new fuzzy controller that will enhance better performance. This new fuzzy controllers should take into account the following ideas:
1. To develop completely an automatic adaptive controller.
2. The controller must be adaptive to any electrical motor.
3. To minimize the electrical noises, which appear in any power drive.
• Develop the torque ripple reduction with fuzzy logic with duty ratio controllers and also with multilevel converters.
• Develop fuzzy logic with duty ratio DTC without sensor implementation that will be sensing two currents, the DC voltage and by means of either Kalman filter techniques or observers.
• Develop and apply different fuzzy logic DTC, not only to induction motors as it has been done in the present work, but also to any