Photovoltaic module diagnostics by series resistance monitoring and temperature and rated power estimation

One of the most important parameters, which characterizes a photovoltaic panel health state, is its series resistance. An increase of this, normally indicates bad contacts between cells or panels. An other important property, which characterizes the aging of the panel is the reduction of its MPP power in standard test conditions (STC¹). Simulation and experimental measurements regarding the determination of a PV panel series resistance, its MPP power in STC, as well as its temperature, are presented in this paper. It is shown that the panel series resistance can be determined experimentally without needing to perform an entire I-V curve scan. The panel MPP power in STC and its temperature - given the irradiance is measured - can be well approximated using the measured I-V curve, and a simple model of the PV panel.