Harmonic Analysis of Voltage Zero-Sequence-Based Encoderless Techniques

This paper exploits the interaction between the low-frequency and the high-frequency fields created by signal-injection techniques during sensorless estimation of the air-gap flux position in induction machines. Such an interaction causes new phenomena that can be summarized in a modulation of the machine saturation level and creation of harmonics that contain information about the position of the flux. This paper analyzes the issues related to the presence of additional fields and predicts the resulting harmonic content using three different approaches such as analytical calculations, computer simulation, and finite element analysis. Experimental measurements confirm the conclusions of this paper.