Position sensorless control of permanent magnet assisted synchronous reluctance motors

The sensorless control of permanent magnet assisted synchronous reluctance motors is faced, in order to conjugate the advantages of the sensorless control with full exploitation of the allowed operating area, for a given inverter. A d-axis pulsating flux is injected at low and zero speed, while it is drop-out, at large speed, to save voltage and additional loss. A flux-observer-based control scheme is used, which includes an accurate knowledge of the motor magnetic behavior. This leads, in general, to good robustness against load variations, by counteracting the magnetic cross saturation effect. Moreover, it allows an easy and effective correspondence between the wanted torque and flux and the set values of the chosen control variables, that is d-axis flux and q-axis current. Experimental verification of the proposed method is given, by pointing-out steady-state and dynamic performance as well. A prototype PMASR motor is used to this aim, as part of a purposely assembled prototype drive, for light traction application (electric scooter).