A comparison of an adaptive full-order observer and a reduced-order observer for synchronous reluctance motor drives

Two back-EMF-based position observers are compared for motion-sensorless synchronous reluctance motor drives. The reduced-order observer is of the second order, and the adaptive full-order observer is of the fourth order. The proposed design rules guarantee the stability of the adaptive full-order observer, if the parameter estimates are accurate. The observers are experimentally evaluated using a 6.7-kW synchronous reluctance motor drive in low-speed operation and under parameter errors. The gain selection of the second-order observer is easier, but the adaptive full-order observer is more robust against parameter variations and spatial harmonics.