Comparison of carrier signal voltage and current injection for the estimation of flux angle or rotor position

The focus of this paper is on a comparative analysis of position, velocity, and flux estimation in AC machines based on the injection of a carrier signal superimposed on the fundamental excitation. Specifically the paper compares methods based on voltage and current injection and develops guidelines on their respective use. To provide a basis for fair comparison, the paper addresses two problems of carrier signal current injection: (1) the regulation of high frequency currents with current regulators of limited bandwidth (regulation of the carrier signals with zero steady-state error is necessary to avoid loss of spatial information); and (2) the extraction of the spatial information contained in the induced voltages.