Extraction of photovoltaic generator parameters through combination of an analytical and iterative approach

In the present work, we propose an improved method based on a combination of an analytical and iterative approach to extract the photovoltaic (PV) module parameters using the measured current-voltage characteristics and the simple diode model. First, we calculate the series resistance using a set of analytical formulas for the base values of the three current-voltage curves. Then, the three other parameters are analytically expressed as functions of serial resistance and ideality factor based on the linear least-squares method. Finally, the ideality factor is calculated applying an iterative algorithm to minimize the normalized root mean square error (NRMSE) value. The proposed method was validated with a real experimental set of two PV generators, which showed the best fit to the I-V curve. Moreover, the proposed method needs only the initial value of the ideality factor

An efficient numerical method and new analytical model for the prediction of the five parameters of photovoltaic generators under non-STC conditions

In this work, the single-diode model is used to model the PV generator. Then, a numerical method is introduced to extract its five parameters using just the values of the key-points. To this end, we apply the I-V characteristic on the three remarkable points to get three equations with five unknowns. To complete the necessary system of five equations, the two other remaining equations are extracted as follow; the first, from the derivative of the equation linking the generator's current to its voltage. Second, an expression linking the fill-factor to the four parameters: Is, Rp, Rs and n is used as the fifth equation. This method is serves to extract the five parameters using five equations, without using any approximation. The accuracy of this approach is evaluated using experimental data for a solar cell, and extracted data from datasheet for a PV panel. Then, using some statistical indicators, this method has shown a good accuracy. Moreover, to get the values of the five parameters for non-standard conditions, and predict the I-V curves and the maximum power, a new analytical model of open-circuit voltage as a function of the module temperature and irradiance is presented as well in this paper