An important growth in the power of the photovoltaic systems connected to a grid has recently been observed. In spite of the advances in module technology, the problems in the system design increased, especially regarding the surface of the earth they occupy. In this work we propose a complete model for plant simulation with different wiring diagrams and under dynamic shading. Results obtained from simulations showed that the configuration with the lowest performance was that of only one serial-parallel group, whereas the highest efficiency corresponded to a design of groups of modules in parallel connected then in series. In general, a higher efficiency was obtained diminishing the quantity of modules in series and increasing their number in parallel. The simulation model proposed allows exploring different alternatives of wiring modules and finding the most efficient configurations for photovoltaic plants of medium and high power. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.