Title Voltage balancing in three-level neutral-point-clamped converters via Luenberger observer
Authors Umbria, Francisco, Gordillo, Francisco, GÓMEZ-ESTERN AGUILAR, FABIO, Salas, Francisco, Portillo, Ramon, Vazquez, Sergio, GÓMEZ-ESTERN AGUILAR, FABIO
External publication No
Means Control Eng. Practice
Scope Article
Nature Científica
JCR Quartile 2
SJR Quartile 1
JCR Impact 1.81400
SJR Impact 1.20500
Area International
Publication date 01/04/2014
ISI 000332906400004
DOI 10.1016/j.conengprac.2013.12.003
Abstract This paper addresses the problems associated with the dc-link capacitor voltages of the three-level neutral-point-clamped power converter: the imbalance of the capacitor voltages as well as the presence of an ac-voltage low-frequency oscillation in the dc link of the converter. In order to cope with them, a mathematical analysis of the capacitor voltage difference dynamics, based on a direct average continuous model, is carried out, considering a singular perturbation approach. The analysis leads to a final expression where a sinusoidal disturbance appears explicitly. Consequently, the two problems can be handled together using the ordinary formulation of a problem of regulating the output of a system subject to sinusoidal disturbances, applying classical control theory to design the controller. In this way, the controller is designed including the disturbance estimate provided by a Luenberger observer to asymptotically cancel the disturbance, while also keeping the capacitor voltages balanced. Experiments for a synchronous three-level neutral-point-clamped converter prototype are carried out to evaluate the performance and usefulness of the converter working as a grid-connected inverter under the proposed control law. (C) 2013 Elsevier Ltd. All rights reserved.
Keywords Multilevel power converter; Neutral-point-clamped (NPC) converter; Voltage balancing; Disturbance rejection; Luenberger observer
Universidad Loyola members