Position and velocity sensorless control of synchronous reluctance motor at low speed using disturbance observer for high-frequency extended EMF

Abstract

Recently, synchronous reluctance motors (SynRMs) have attracted study because of their favorable properties, including limited thermal expansion of the shaft due to low heat generation by the rotor, the ability to drive at high velocity, a low degree of torque ripple and an absence of demagnetization problems. Sensorless control of SynRMs is now desired, and several methods have been proposed. These methods, however, have difficulties at low speed when the voltage signal necessary to estimate rotor position is very small. The authors have proposed a new position estimation method using high-frequency extended e.m.f. (EEMF) in which high-frequency voltage and current are calculated using a disturbance observer. Simulations have shown the new method to be very useful. In this paper, it is shown, experimentally, that it is possible to control the motor at low speeds without the position and velocity sensor using the new proposed method.