Direct-Axis Calculation of Direct Torque Control of Induction Motor Using SVM

In this research article author wants to investigate a direct torque control for induction motor. There are drawbacks of DTC method for induction motor. These problems include the inadequacy of electromagnetic torque and the large estimated error of magnetic flux while motor operated in low speed, and generating torque ripples. This critique provided filter feedback, magnetic flux compensation and fixed flux variation DTC method to reduce the estimated error of magnetic flux; furthermore, it provided a strategy of effectively producing the output electromagnetic torque while the motor operated in low speed. Motor could be operated more smoothly by reducing current harmonic waves and power consumption. It could effectively decrease speed error and improve the efficiency of driver. A method is provided to modify the magnetic flux estimator of the direct torque control and improve the inadequacy of electromagnetic torque while motor operated in low speed. It is because that the rotors flux changes slowly while motor operated in low speed. If the stator flux is still operated in the fixed flux, the stator flux will not be able to control effectively which may decrease the output electromagnetic torque and increase in the speed error. This article provides a method to raise the stator flux which makes it effectively produce electromagnetic torque in the low speed and reduces the speed error. Then, applying the DTC for the motor operation is to select a vector from the list of voltage (Vk) vector table. This traditional method is not able to generate a smooth

sine wave voltage. Thus it produces torque ripples during the process of switching over between voltage vectors. Torque ripples cause high noise and oscillation. Then it is difficult to apply in the high-accuracy control. This paper provides fixed flux variation DTC method which uses the space vector modulation (SVM) to compose of the voltage vectors. It effectively reduces the torque ripples during the motor operation. Finally MATLAB simulation software is used to show the possibility of control system. Then simulation results verifies the feasibility and optimality of the new-type direct torque control for induction motor drive system.