Author(s)

Robinson Ndegwa, Elijah Ayieta, Justus Simiyu, Nicodemus Odero

Department of Physics, University of Nairobi, Nairobi, Kenya.

A single diode model for a photovoltaic solar module is the most ideal and quick way of analyzing the module characteristics before implementing them in a solar plant. Solar modules manufacturers provide information for three critical points that are essential in I-V, P-V or P-I curves. In this study, we propose four separate simulation procedures to estimate the five-model parameters of an analogous single diode equivalent circuit by utilizing three cardinal points of the photovoltaic module I-V curve, described from experimental data using a solar simulator and manufacturer’s datasheet. The main objective is to extract and use the five unknown parameters of a single diode model to describe the photovoltaic system using I-V ad P-V plots under different environmental conditions. The most influential parameters that greatly alter the cardinal points defined at short circuit point (SCP), the maximum power point (MPP) and the open circuit point(OCP) are the ideality factor (n) and the diode saturation current (I_o). For a quick and fast convergence, we have determined the optimal ideality factor (n_o) and optimal saturation current (I_oopt) as the primary parameters by first assuming the optimal values of R_sh, R_s and I_ph at standard test conditions (STC). Further, we evaluated the effects of I_ph, R_s and R_sh on I-V and P-V curves by considering the values of n below n_o. We have evaluated different iterative procedures of determining R_sh and R_s at open-circuit, short-circuit point and the maximum-power points. These procedures have been classified into four approaches that guarantees positive shunt and series resistance for n ≤ n_o. These approaches have been categorized by deriving the saturation current as a dependent variable at each cardinal point with or without R_s and R_sh pair. The values obtained for the five parameters have been used to simulate the photovoltaic solar module characteristic curves with great precision at different air temperatures and irradiances, considering the effect of Nominal Operating Cell Temperature (NOCT).

Five-Parameter Model, Ideality Factor, Saturation Current, Series and Shunt Resistances

Ndegwa, R. , Ayieta, E. , Simiyu, J. and Odero, N. (2020) A Simplified Simulation Procedure and Analysis of a Photovoltaic Solar System Using a Single Diode Model. Journal of Power and Energy Engineering, 8, 65-93. doi: 10.4236/jpee.2020.89006.