Comparison of a Reduced-Order Observer and a Full-Order Observer for Sensorless Synchronous Motor Drives

Abstract

Abstract-Two back-electromotive-force (EMF)-based position observers are compared for motion-sensorless synchronous motor drives: the reduced-order observer and the adaptive full-order observer. A stabilizing gain is proposed for the adaptive fullorder observer, which guarantees the local stability of the closedloop system, if the motor parameters are known. Equations for the steady-state position error and for the linearized estimationerror dynamics under erroneous parameters are derived, and the robustness of the two observers against parameter errors is analyzed and compared. 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 reduced-order observer is easier, but the adaptive full-order observer can be made more robust against parameter variations and noise.

Signal-injection assisted full-order observer with parameter adaptation for synchronous reluctance motor drives

“…With this gain selection, the characteristic polynomial of the closed-loop system consisting of (1) - (12) can, after linearization, be split into a product of two secondorder polynomials [18],…”

“…The observer is of the fourth order, and there are four gains. In order to further reduce the number of design parameters, d and e can be chosen as [18], [19] …”

“…The characteristic polynomial of this system is given in (18). In a similar manner, the linearized estimation-error dynamics are obtained for the adaptation of the q-axis inductance:…”

Observers for Sensorless Synchronous Motor Drives: Framework for Design and Analysis

“…A voltagemodel-based flux observer, operating in stator coordinates, is combined with a position-tracking loop in [2], [3]. A state observer, operating in estimated rotor coordinates, is augmented with a speed-adaptation loop in [4], [5]. In order to simplify the gain selection, a modified state variable is used to form a D-state observer in [6] and a minimum-order flux observer in [7].…”

State observer for sensorless control of a grid-connected converter equipped with an LCL filter: Direct discrete-time design

“…Adaptive observers have been used for estimation of the rotor speed, position, and flux magnitude in motor drives, e.g., in [14], and, correspondingly, for estimation of the grid-voltage frequency, angle, and magnitude in gridconnected converters [8], [10]- [13]. The estimation error of the converter current includes the information of the gridvoltage angle and amplitude [11], [12].…”