Photovoltaic module series resistance identification at its maximum power production

Abstract

Analysis of measured current–voltage curves offers a cost-effective option for online condition monitoring of photovoltaic (PV) modules. The current–voltage curves of PV modules can be modeled accurately using the well-known electrical single-diode model. In practical applications, condition monitoring should be based on measurements performed near the maximum power point (MPP) by affecting PV power production negligibly. The series resistance is the most important single-diode model parameter in assessing the condition of PV modules; this paper proposes a novel method for its determination by using measurements acquired near the MPP only. The proposed method can be used with any series resistance identification procedure based on current–voltage curve measurements. The proposed method is experimentally validated using current–voltage curves of two PV modules measured in Malaga, Spain. This study allows to assess that the series resistance can be accurately determined from measurements performed near the MPP. Especially the results obtained with an ISOFOTON ISF-145 PV module are very promising: the scaled series resistances obtained from measurements done without lowering the PV power more than 2% of the maximum power differ on the average by no more than 2% of the series resistances obtained from the whole current–voltage curves.