Modelling of a Rotating Signal Injection-Based Position Observer for Sensorless Synchronous Electric Drives

A new formulation of the observer transfer function (TF) for rotating injection-based techniques is proposed. The modulation/demodulation theory is exploited to derive the estimator TF in the Laplace-domain. The accuracy of the proposed observer TF is verified with several regulators designed with two approaches, namely, direct synthesis (DS) and internal model principle (IMP). Theoretical considerations and accuracy of the proposed model are verified through an extensive simulation stage. Time response and position tracking of different regulators designed for a wide range of bandwidth are investigated. Finally, the performance of the regulators designed with the conventional observer TF and the proposed one are compared highlighting the flaws of the former approach.