Carrier signal injection based sensorless control of permanent magnet synchronous machines without the need of magnetic polarity identification

Inherent 2^nd harmonic resistive and inductive saliencies are generally employed for rotor position estimation of permanent magnet synchronous machine at standstill and in low speed range. However, the resultant estimated rotor position has an angle ambiguity of π due to the lack of magnetic polarity information in these saliencies. Therefore, this paper utilises the high frequency (HF) inductance (permeance) harmonics (i.e., HF saliency) generated due to the saturation modulation between HF field and main flux field for rotor position estimation. Since the HF saliency contains the magnetic polarity information, the resultant carrier responses due to the interaction between HF field and HF saliency (i.e., the secondary harmonics) can be utilised for the actual rotor position tracking without any ambiguity of machine polarity. This will not only eliminate the time-consuming process of polarity identification but also enhance the position estimation robustness and stability. Finally, in order to validate the effectiveness of HF saliency based sensorless control strategies, experiments are carried out on a laboratory permanent magnet synchronous machine.