Robust series resistance estimation for diagnostics of photovoltaic modules

It is well-known that the slope of the I - V curve of a photovoltaic panel at open-circuit conditions is proportional to the panel's internal series resistance. However, the slope of the I - V characteristic is greatly affected by environmental conditions, showing an approximately linear relationship with the reciprocal of the irradiation. In this work, a simple series resistance estimation method based on the slope of of the I - V curve at open-circuit translated to Standard Test Conditions (STC1), is presented. Experimental test results for crystalline silicone panels show good estimation performance in a wide range of irradiation (> 200W/m2) intensities, with a worst case accuracy of ≈ 0.15Ω