1. Voltage balancing in three-level neutral-point-clamped converters via Luenberger observer.
- Author
-
Umbría, Francisco, Gordillo, Francisco, Gómez-Estern, Fabio, Salas, Francisco, Portillo, Ramón C., and Vázquez, Sergio
- Subjects
- *
ELECTRIC potential , *CASCADE converters , *OBSERVABILITY (Control theory) , *CAPACITORS , *PROTOTYPES , *SINGULAR perturbations - Abstract
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. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF