PV module Series Resistance

The series resistance Rs used in PVsyst is the resistance involved in the one-diode model.

It should not be confused with the slope dI/dV measured around Voc, which we call "apparent series resistance" Rsapp.

The Rs of the one-diode model is not directly measurable on the PV-module. It is one of the 4 unknown related (coupled) parameters when adjusting the one-diode model.

It's effect on the I/V curve is combined with the diode model (exponential) slope: the lower Rs resistance, the sharpener I/V characteristics toward high voltages.