About the identification of the single-diode model parameters of high-fill-factor photovoltaic modules

The suitable identification of the five parameters for the single-diode model of a photovoltaic module is mandatory for having a correct simulation of the module behavior, at least in STC conditions. This process is afforded in literature by means of a number of fitting procedures, but many studies report difficulties in identifying the series and the parallel resistances for modules showing a high fill factor. In these cases, the identified value of such resistances may become negative, with an evident contrast with the physical meaning of such parameters. In this paper two approaches presented in literature, and based on some simplifications of the nonlinear problem under study, are firstly compared and also jointly used. Their application to some practical cases is discussed and compared with the exact solutions of two different formulations of the system of five non-linear equations.