Dyna, year 80, Nro. 182, pp. 191-199. Medellin, December, 2013. ISSN 0012-7353 EXPERIMENTAL VALIDATION OF A MODEL FOR PHOTOVOLTAIC ARRAYS IN TOTAL CROSS-TIED CONFIGURATION VALIDACIÓN EXPERIMENTAL DE UN MODELO PARA ARREGLOS FOTOVOLTAICOS EN MATRIZ INTERCONECTADA CARLOS ANDRÉS RAMOS-PAJA Ph.D., Profesor Facultad de Minas, Universidad Nacional de Colombia, Sede Medellín, caramosp@unal.edu.co JUAN DAVID BASTIDAS Ing., Escuela de Ingeniería Eléctrica y Electrónica, Universidad del Valle, Cali, Colombia, juan.d.bastidas@correounivalle.edu.co ANDRÉS JULIÁN SAAVEDRA-MONTES Ph.D., Profesor Facultad de Minas, Universidad Nacional de Colombia, Sede Medellín, ajsaaved@unal.edu.co Received for review January 18 th , 2013, accepted July 13th, 2013, final version July, 24 th , 2013 ABSTRACT: An extended analysis and the experimental validation of a mathematical model for Total Cross-Tied photovoltaic arrays, based on the inflection points concept, is presented. The model is able to reproduce the electrical characteristics of real photovoltaic plants in both uniform and mismatched conditions (e.g. partial shading). The model calculates the array voltages in which the bypass diodes are turned on, which allows one to detect when a photovoltaic module is active or bypassed in order to consider or neglect its contribution to the array current and power. Such a procedure generates a significant reduction in the computational burden required in comparison with classical approaches. The experiments presented in this paper confirm the advantages of the model: low computational burden, high accuracy reproducing the experimental data, and its usefulness to perform energetic evaluations for viability analysis. KEYWORDS: photovoltaic array, mathematical model, inflection points, low computational burden, experimental validation, total cross- tied configuration. RESUMEN: Este artículo presenta un análisis extendido y la validación experimental de un modelo matemático, basado en el concepto de puntos de inflexión, para arreglos fotovoltaicos en matriz interconectada. El modelo reproduce las características eléctricas de plantas fotovoltaicas reales en condiciones uniformes y no-uniformes (e.g. sombreado parcial). El modelo calcula los voltajes del arreglo en los cuales se activan los diodos de bypass, lo que permite detectar si un módulo fotovoltaico está activo o inactivo para decidir si se considera o desprecia su contribución a la corriente y potencia del arreglo. Este procedimiento genera una reducción significativa en la carga computacional requerida en comparación con soluciones clásicas. Los experimentos reportados en este artículo confirman las ventajas de modelo: baja carga computacional, alta exactitud en la reproducción de datos experimentales, y su utilidad en las evaluaciones energéticas de arreglos fotovoltaicos orientadas al análisis de viabilidad. PALABRAS CLAVE: sistemas fotovoltaicos, modelo matemático, puntos de inflexión, baja carga computacional, validación experimental, matriz interconectada. 1. INTRODUCTION The high popularity of solar power systems caused by their low pollution and sustainable operation [1], along with the implementation of policies and subsidies to provide incentives for Photovoltaic (PV) installations [2, 3], have promoted the PV market in the last years, where the installed PV power capacity has grown from 0.1 GW in 1992 to 14 GW in 2008 [2]. Most of the installed capacity corresponds to grid-connected applications, which, in many cases, operate under mismatched conditions due to the partial shadows produced by surrounding objects (trees, buildings, antennas, etc.) and clouds, as well as the differences in the parameters of the PV panels. When a PV array is operating under mismatched conditions the Power vs. Voltage curves exhibit