An In-depth Analytical Study of the Switching States of Direct Torque Control Algorithm of an Induction Motor Over the Entire Speed Range

In this paper, a full analysis of the voltage vectors (VVs) in the Direct Torque Control (DTC) algorithm is presented to determine the accurate effect on both the torque and the flux throughout the entire sector with the change of the speed and the load. The analytical analysis showed that the application of specific VVs results in false switching states in a specific range of the sector with the change of speed, load, or both. More specifically, some switching states are not fully defined. These wrong states are called Uncontrollable Angles (UCAs). The authors proposed a robust and effective scheme that ensures the elimination of the (UCAs) over the entire speed range. Through the analysis, it was found that the basic scheme suffered from UCAs of large values ​​at medium and high speeds. Accordingly, a special strategy for medium and high speeds with 18 Sub-Sectors (SSs) was proposed while maintaining the basic 6 sectors strategy for low speed. The transition speed between the two strategies was determined to ensure the absence of UCAs. Furthermore, to verify the effectiveness of this method, MATLAB/ Simulink results of the drive system were accomplished and validated.