With the increasing use of photovoltaic (PV) systems, the research studies to improve the efficiency of PV systems have gained greater interest in recent years, especially under non-uniform operating conditions and failed operation. The aim of this paper is the study, the optimization and the analysis of behavior of a photovoltaic system in normal and failed operation for one or more of any defects and any configuration of the PV system (module, string or field) trying to get close to the actual operation of photovoltaic systems. (C) 2014 Elsevier Ltd. All rights reserved.