Rotor and flux position estimation in delta-connected AC machines using the zero sequence carrier signal current

This paper analyzes carrier signal voltage injection, zero sequence current based, sensorless control techniques for delta-connected, three-phase AC machines. The analysis will focus on rotor position estimation (tracking of rotor-position-dependent saliencies) but the method applies equally well to flux position estimation (tracking of flux-dependent saliencies). The paper first develops a theoretical model and then provides analysis of relevant implementation aspects, like selection of the carrier signal frequency and voltage magnitude, measurement of the zero sequence carrier signal current, measurement and compensation of saturation-induces saliencies and the signal processing needed for position/flux angle estimation.