Photovoltaic (PV) power has been successfully used for over five decades. The output characteristics of a PV array vary nonlinearly when temperature or irradiance conditions change. At the beginning of this paper, the performance of PV panel is analyzed, for parallel and series connections of solar cell elements exposed to the same light conditions and temperature by using the Brune's conditions of interconnection. Therefore the parameters of the equivalent circuits for each typical PV cell connections are characterized by a new set of matrix equations. A Lab View application is implemented to prove the theoretical models. Moreover, the grid connected PV systems have become more popular because they do not need battery back-ups to ensure maximum power point tracking (MPPT). However, partial shading is one of the main causes that reduces energy yield of PV array. In this respect, the second part of the paper refers to the influences of different irradiance conditions on the PV array performance in order to achieve MPPT under shaded array conditions. Consequently, PV array emulator is crucial for the operational evaluation of system components. The purpose of this study extension is to design and develop a new real-time emulator of PV array output characteristics based on closed-loop reference model. (C) 2011 Elsevier Ltd. All rights reserved.