Initial Rotor Position Detection of Induction Machines using Feedforward Sensorless Saliency Separation
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Technical University of Vienna
ALSTOM Transport Austria GmbH
Corresponding author
Eduardo Rodriguez Montero   

Technical University of Vienna
Power Electronics and Drives 2021;6 (41)
Voltage step excitation computes a saliency phasor out of phase current derivatives resulting from specific voltage steps, generated by the inverter switching. Within the saliency phasor, all machine saliencies appear superposed. For some machine constructions, multiple saliencies are present. Given its high accuracy, rotor slotting saliency is often chosen as the sensorless control signal. In order to exclusively access rotor slotting harmonic, saliency separation needs to be carried out, with the goal of eliminating all non-control saliencies from the saliency phasor. Here, feedforward harmonic compensation based on look-up tables is chosen. The idea is to once estimate each saliency regarding amplitude and phase shift, store such information it in a torque-dependent look-up table, and use it for feedforward compensation. Yet, several saliencies are linked to the rotor position and, thus, the stored phase shift in the look-up table is fixed to a defined rotor position at which the saliency estimation was performed. For the feedforward compensation to work during each sensorless start-up, an initial rotor slot detection is needed. This paper presents a technique to estimate initial rotor angle only based on the inherent characteristics of the induction machine multi-saliencies and an iterative feedforward compensation process.
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