Performance improvement of SVM-DTC of Induction Machine Drive via Backstepping Controller and Stator Resistance Compensator

Abstract

The direct torque control (DTC) of the induction machine (IM) has a very fast dynamic response but it has the disadvantage of large oscillations of torque and flux with an inconstant switching frequency. In particular, this article presents an improved DTC method based on the backstepping technique of an induction machine supplied with voltage by an inverter controlled by a Space Vector Modulation (SVM). For this strategy, the rotor speed, the electromagnetic torque and stator flux are selected as virtual state variables, and then a beckstepping controller are designed to produce the components of the stator reference voltage. Then, depending on its voltage components, the pulse width modulation is used to produce switching states of the inverter. On the other hand over a wide operating range of the machine the variation of the stator resistance due to heating degrades the performance of the DTC. To solve this problem an estimator has been developed to compensate for each variation in the stator resistance of the machine during operation. The results obtained by numerical simulation show the effectiveness of the proposed control method. This combination could effectively reduce flux and torque ripples with good dynamic performance and robustness.