Automatic Algorithm Based on Simpson Seventh-Order Integration of Current Minus Short-Circuit Current: Extracting Photovoltaic Device Parameters Within One-Diode Model

Simpson’s seventh-order integration has been implemented in an automatically executable program to integrate the current minus the short-circuit current. Then, a regression of this integral to a second-degree polynomial in two variables, namely the voltage and the short-circuit current, is performed, obtaining six regression constants. The series (Rs) and shunt resistance (Rsh), the ideality factor (n), and the saturation (Isat) and light current (Ilig) are extracted from these regression constants. The standard errors of these five photovoltaic device parameters are also calculated. Rs, Rsh, n, Ilig, and Isat can be extracted with less than 1% error when the percentage noise is pn< 0.05%, with just N≥26 (N≥101 for Isat), in contrast with a value of N≥751, in the case of the trapezoidal integration method being used. The program calculates the photovoltaic device parameters in less than a second for 1001 data points, four seconds for 10,001 data points, and nineteen seconds for 20,001 data points, which is in striking contrast with the tenths of minutes when using the trapezoidal integration provided by the software Origin, as it has to be performed manually. It is worth mentioning that for the case of pn≥ 0.1%, both trapezoidal and Simpson seventh-order integration practically yield the same accuracy; nevertheless, the program outstands the trapezoidal integration, as it achieves the extraction in nineteen seconds or less. The results reported in this article are valid for the one-diode solar cell model, and might not be valid for other models.