Stability enhancement via speed adaptation and efficiency improvement for induction machine

Abstract The primary characteristics of an electric drive include the ability to utilize the maximum torque throughout the speed range, minimal reliance on parameters, and, if feasible, the highest efficiency. This paper proposes a new speed observer and energy-saving control approach for induction motors (IMs) that exploits the advantages of Maximum Active Power per Flux Controlling Variable (MAPPFCV) for flux optimization. It employs an extended-speed observer to enhance the low-speed stability of sensorless IM and address the challenges, reducing the unstable area during low-speed operation. The proposed energy-saving approach, in real time, enables the algorithm to evaluate the optimal flux of the MAPPFCV, thereby enhancing efficiency. In a recent study on applying the loss model for flux optimization, the core loss resistance has been considered, as it increases the robustness and accuracy of the model. However, considering core resistance, complexity, and the flux optimization parameter dependence increases, resulting in significantly increased sensitivity. Thus, this paper proposes a model-based approach that considers core loss resistance for flux optimization, providing better performance while being less complex and robust to parameter variations. The advantages obtained, including simple and straightforward implementation; high dynamic performance; reduced stator current drawn by the drive; reduced power loss leading to improved efficiency, and reduced steady-state torque ripple, are presented in the article. The findings demonstrate that the proposed approach performs well across various operating conditions. Hardware results on a 5.5 kW IM are presented to validate the effectiveness and performance of the proposed approach.