energies Article Adjusting the Single-Diode Model Parameters of a Photovoltaic Module with Irradiance and Temperature Nader Anani 1,* and Haider Ibrahim 2 1 School of Engineering, University of Wolverhampton, Telford TF2 9NT, UK 2 Department of Electrical Technique, Southern Technical University, Technical Institute-Qurna, Basra, Iraq; [email protected] * Correspondence: [email protected] Received: 30 May 2020; Accepted: 17 June 2020; Published: 22 June 2020 Abstract: This paper presents a concise discussion and an investigation of the most literature-reported methods for modifying the lumped-circuit parameters of the single-diode model (SDM) of a photovoltaic (PV) module, to suit the prevailing climatic conditions of irradiance and temperature. These parameters provide the designer of a PV system with an essential design and simulation tool to maximize the efficiency of the system. The parameter modification methods were tested using three commercially available PV modules of different PV technologies, namely monocrystalline, multicrystalline, and thin film types. The SDM parameters of the three test modules were extracted under standard test conditions (STC) using a well-established numerical technique. Using these STC parameters as reference values, the parameter adjustment methods were subsequently deployed to calculate the modified parameters of the SDM under various operating conditions of temperature and irradiance using MATLAB-based software. The accuracy and effectiveness of these methods were evaluated by a comparison between the calculated and measured values of the modified parameters. Keywords: ideality factor; irradiance; photocurrent; saturation current; series resistance; shunt resistance; single-diode model; temperature effects 1. Introduction Photovoltaic systems offer the most direct conversion of the electromagnetic energy in the sunlight into electricity. At the heart of any PV power plant is the PV generator, which typically consists of an array of PV modules connected in series-parallel combinations to deliver the rated power at the required levels of terminal current and voltage. Each PV module consists of several PV cells, which are almost always connected in series to provide a specific terminal voltage. The terminal I-V (current-voltage) and P-V (power-voltage) characteristics of a typical PV generator, whether it is a cell, a module, or an array, are shown in Figure1. Three salient points can be identified on the I-V curve: The short circuit (SC), the open circuit (OC), and the maximum power point (MPP). The design of a PV power system requires a lumped-circuit parameters’ model of the PV generator. This is used for purposes, such as to properly size the power switching devices used in the power processing converters, designing the maximum power point tracking system, and for efficient sizing of the PV array. In addition, such an equivalent circuit model can be readily embedded in circuit simulation programs. The widely accepted circuit model of a PV generator is the single-diode model (SDM), which is also included in Figure1[ 1–3]. This model can be easily adapted to model a cell, a module, or an array and offers a compromise between accuracy and complexity [4–6]. An extensive study on the measurement uncertainty using different lumped-circuit parameters models of a PV module can be found in [7]. However, this paper was based on the single-diode model. Energies 2020, 13, 3226; doi:10.3390/en13123226 www.mdpi.com/journal/energies Energies 2020, 13, 3226 2 of 17 Energiesextensive2020, study13, 3226 on the measurement uncertainty using different lumped-circuit parameters models2 of 17 of a PV module can be found in [7]. However, this paper was based on the single-diode model. Figure 1. The normalized I-V and P-V curves of a typical PV module (left) and the single-diode Figure 1. The normalized I-V and P-V curves of a typical PV module (left) and the single-diode model model (right). (right). The SDM involves five parameters: The photocurrent Iph, the saturation current Isat, and the The SDM involves five parameters: The photocurrent , the saturation current , and the ideality factor n of the diode, the parallel resistance Rsh, and the series resistance Rs. 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