Saliency-Based Position Sensorless Control of a Heavily Cross-Saturated PMSM

In position sensorless control schemes for permanent magnet synchronous motors usually saliency-based estimation methods are used to detect the rotor position in the low speed range including standstill. The capability of these methods is determined by the characteristics of the differential inductances and therefore strongly depends on the design of the motor. Especially cross-saturation and spatial harmonics cause significant estimation errors, which may restrict the current and torque to an upper limit to ensure stable position sensorless control. In this paper saliency-based position estimation of a heavily cross-saturated PMSM using the INFORM method is investigated. The impact of saturation on the estimation accuracy is analyzed by simulations and confirmed by measurements. A simple compensation of the estimation error is proposed and the stability of the closed-loop compensated estimation scheme is analyzed. Finally, measurements of position sensorless control up to rated torque are presented.