An observer-based three-phase current reconstruction using DC link measurement in PMAC motors

Abstract

This paper proposes a novel three-phase current reconstruction technique that utilises the measured DC link current and the switching signals of a three-phase inverter used in permanent magnet (PM) AC motors. The method is based on an adaptive current observer, which includes the model of a motor drive to estimate the three-phase currents. The relationship between the three-phase currents and the DC link current is used to estimate the DC link current first as an output of the observer. Then, this output is compared with the measured DC link current and the current error. The error is used to compensate the DC link voltage that can force the estimated phase currents to follow the actual winding currents. The paper provides a detailed analysis of the current conduction modes in a three-phase inverter and summarises the implementation details the method in realtime. A wide range of experimental results provided in this study demonstrates that the method can accurately reconstruct the phase currents both in the sinusoidal and in the rectangular current excitation modes of a PMAC motor.