Maximum power point tracking under realistic operating conditions

The process of tracking the Maximum Power Point (MPP), known as MPPT, becomes problematic under realistic operating conditions due to the potential for there to be more than one local maxima. A very detailed physics based model has been developed for a PV module (in this application a PV roof tile) using the Orcad platform for PSpice. This model is unusual in that it properly
represents partial module shading and cell temperature variation. The PV roof tile, based on polycrystalline silicon cells, comprises 18 series-connected cells. In the model, each cell is represented by a standard two-diode sub-model, for which different levels of radiation and cell temperature can be simulated to obtain a realistic overall I-V characteristic for the module. The model can be extended to model any reasonable number of PV roof tiles wired in series and parallel to form a roof array. The IV characteristics calculated in this way using PSpice will be validated using an outdoor PV roof test system located at the University of Strathclyde, Glasgow.