Stabilization of Regenerating-Mode Operation in Sensorless Induction Motor Drives by Full-Order Flux Observer Design

Abstract

Abstract-This paper deals with the full-order flux observer design for speed-sensorless induction motor drives. An unstable region encountered in the regenerating mode at low speeds is well known. To remedy the problem, a modified speed-adaptation law is proposed. Instead of using only the current estimation error perpendicular to the estimated flux, the parallel component is also exploited in the regenerating mode. Using current estimation error loci in steady state, a linearized model, simulations, and experiments, it is shown that the observer using the proposed speed-adaptation law does not have the unstable region. It is also shown that the effect of erroneous parameter estimates on the accuracy of the observer is comparatively small.

Feedback Gain Design Method for the Full-Order Flux Observer in Sensorless Control of Induction Motor

“…In order to validate the proposed design, we studied a conventional test used by industrial drive designers: very low and progressive load torque increase under constant speed; Fig. 5 depicts results in regenerating mode obtained using the observer gain g 1 = −0.25R s , [13], [5]. The speed reference was set to (−25rad/s) (dashed line) and a rated-load torque ramp was applied at t=0.…”

“…Using the assumption of constant angular rotor speedω = 0 (i.e. the speed variations are slow with respect to electrical mode) [8], [5], the speed adaptive law is [8]:…”

“…In these two systems, the stator frequencies are regarded as identical : ω s = ω s [5]. Preserving only dynamic parts, the two systems (9), (10) become after linearization,:…”

“…Thus, the drive stability can't be guaranteed when this type of observer is associated with a field oriented control. There was many work in order to reduce this region of instability which is due to inadequate observer design [1,2,5,14]. In this paper, we describe the design of an adaptation law that minimizes the instability region of an adaptive speed estimator.…”

Braking scheme for vector-controlled induction motor drives equipped with diode rectifier without braking resistor

“…The stator current i s and the dc-link voltage u d are measured. The rotor flux estimate (whose amplitude is denoted byψ R and angle bŷ ϑ s ) and the rotor speed estimateω m can be obtained using a speed-adaptive flux observer [7], [8].…”