The extraction of photovoltaic module parameters using Fibonacci and Steepest Descent methods

Abstract

Determination of the parameters for a photovoltaic (PV) module is an important part in the PV module modeling process. The PV module parameters include the series and shunt resistances, the leakage currents, the ideality constants, and the PV module solar dependent current. The significance of the PV module parameters is underscored when the high fidelity replication of the behavior of a given PV module is desired. Most PV modules come with a datasheet, which contains key information about the PV module. Some of the data on the PV module datasheet include the maximum power point voltage and current of the PV module, the short circuit current, and the open circuit voltage. Also found on the datasheet are the current and voltage temperature coefficients. However, without accurate knowledge of the PV parameters, obtaining the operating points provided on the PV module datasheet, such as open circuit voltage and maximum power point voltage and current is difficult. The number of parameters to be determined for the PV module is dependent on the model of PV module that is used. The simplest model of the PV module is the one-diode model, followed by the two-diode model, and then the three-diode model. The two-diode PV array model is widely used in the PV array model development, and this two-diode model is the focus of this paper. Current publications that propose methods of extracting the PV module parameters make several simplifications. The goal of these simplifications is to make the two-diode PV model observable. The proposed PV module parameter extraction method in this paper is the method of an optimized Fibonacci search, and the Steepest Descent method. Using these methods, no simplifications are made, and accurate results as compared with data measurements from an actual PV module, are obtained.