Full Sensorless Operation of Induction Machines based on Online Identification of Saliencies using Harmonic Compensation LUTs in Traction Applications

Speed sensorless control of induction machines (IM) around zero frequency is distinctively carried out by external injection, whose objective is to extract rotor-related information by evaluating the actual state of the machine saliencies. Commonly, IM saliencies are identified during an offline encoder-based test where each saliency signal component is estimated regarding its amplitude and phase shift for each required torque point. It is then, during the sensorless online operation, where the identified saliencies are eliminated from the total saliency vector, leading to a single saliency component, which is used for sensorless control scheme. The offline process needed for saliency identification requires time, a shaft encoder (during offline test) and cannot deal with online parameter variations. To deal with such drawbacks, this paper proposes a fully sensorless saliency identification method that runs without position sensor even in the identification phase and can be updated during online operation.