Full-Curve Five-Parameter Extraction of a Commercial Photovoltaic Module Using the Single-Diode Model at Standard Test Conditions

Extracting the parameters of photovoltaic (PV) modules accurately from the experimental current-voltage (I-V) curves is important for operating simulation, assessment of energy yield and degradation diagnostics. This study applies a transparent full-curve parameter-extraction method for the single-diode model (SDM) of a commercial crystalline-silicon PV module under standard test conditions (STC). The unknown parameters are the light-generated current Iph, diode reverse saturation current I0, series resistance Rs, shunt resistance Rsh, and modified diode ideality factor a. Unlike methods based only on short-circuit, open-circuit, and maximum-power points, the adopted procedure minimises the residuals of the implicit SDM equation over 100 measured voltage-current pairs from short circuit to open circuit. The extracted model reproduces the measured I-V and P-V characteristics with very high accuracy, with a maximum-power error of only 0.009% and an R2 value of 0.99999996. These results demonstrate the high numerical accuracy of the full-curve fitting procedure without relying on module-specific voltage, current, or power values. The results obtained confirm that it is possible to obtain full-curve residual fit capable of describing the experimental I-V and P-V characteristics with a very high precision. Simultaneously, the article highlights the importance of understanding the remarkable numerical consistency of the parameter identifiability and measurement resolution concerning cases when the experimental curve is either rounded or approximates the ideal one before reaching the knee point.