TITLE:
A Simplified Simulation Procedure and Analysis of a Photovoltaic Solar System Using a Single Diode Model
AUTHORS:
Robinson Ndegwa, Elijah Ayieta, Justus Simiyu, Nicodemus Odero
KEYWORDS:
Five-Parameter Model, Ideality Factor, Saturation Current, Series and Shunt Resistances
JOURNAL NAME:
Journal of Power and Energy Engineering,
Vol.8 No.9,
September
29,
2020
ABSTRACT: 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 (Io). For a quick and fast convergence, we
have determined the optimal ideality factor (no) and optimal saturation current (Ioopt) as the
primary parameters by first assuming the optimal values of Rsh, Rs and Iph at
standard test conditions (STC). Further, we evaluated the effects of Iph, Rs and Rsh on I-V and
P-V curves by considering the values of n below no. We have
evaluated different iterative procedures of determining Rsh and Rs 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 ≤ no. These
approaches have been categorized by deriving the saturation current as a
dependent variable at each cardinal point with or without Rs and Rsh 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).