Título Suboptimal hierarchical control strategy to improve energy efficiency of vapour-compression refrigeration systems
Autores BEJARANO PELLICER, GUILLERMO, Vivas, Carlos , Ortega, Manuel G. , Vargas, Manuel
Publicación externa Si
Alcance Article
Naturaleza Científica
Cuartil JCR 1
Cuartil SJR 1
Impacto JCR 3.771
Impacto SJR 1.505
Fecha de publicacion 01/10/2017
ISI 000410011200018
DOI 10.1016/j.applthermaleng.2017.06.135
Abstract This paper deals with optimal control of vapour-compression refrigeration systems, where only the compressor speed and the expansion valve opening are considered as manipulable inputs. Any given cycle is completely defined by a three-variable set, thus it is an underactuated control problem. The controllability analysis presented by the authors in a previous work applying linear theory is extended to a pointwise nonlinear analysis based on the phase portrait method. It is concluded that there is no full controllability and only a two-dimensional subspace of the three-dimensional solution space can be explored. A suboptimal hierarchical control strategy is proposed, where an online optimizer explores the two-dimensional controllable subspace to generate the reference on the degree of superheating, which, along with the cooling demand set point and the uncontrolled state, defines the cycle in steady state. The uncontrolled state is, by definition, not manipulable and defines the maximum achievable efficiency. Some simulation results comparing the proposed control architecture with other strategies studied in the literature are included, regarding the energy efficiency achieved in steady state and the dynamic behaviour of the controlled variables, where the controllability issues are highlighted. (C) 2017 Elsevier Ltd. All rights reserved.
Palabras clave Refrigeration system; Vapour-compression cycle; Controllability analysis; Hierarchical control; Nonlinear model predictive control
Miembros de la Universidad Loyola

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