Experimental Implementation of an Algorithm for Real Time Compensation of Phase Current Sensors DC Offset in Field Oriented Controlled PMSM Drives

DCoffset faults of phase current sensors in AC Permanent Magnet Synchronous Machines (PMSMs) are widely studied in the literature since they can lead to heavy torque oscillations and thermal instability of the drive. This paper presents the experimental implementation of an algorithm for the real time estimation and compensation of these faults in PMSM drives controlled by Field Oriented Control (FOC). The method uses equations derived from the analytically closed form solution of the steady-state d-q axes model of PMSM, taking into account the full FOC dynamics and DC offset faults of the phase current sensors. The algorithm allows for detecting, isolating, and estimating the fault conditions by identifying the phase current offsets, both when using three sensors and two current sensors. The real time compensation is based on the developed model, does not require additional hardware, and uses only a digital filter of the measured phase currents for compensating online the offset fault. Experimental results and sensitivity analysis to the motor parameters variations are presented to validate the proposed algorithm.