Estimation of Single-Diode Model Parameters of Photovoltaic Panels Using Four Points on the $I-V$ Curve

The single-diode model equation of a photovoltaic (PV) panel is a nonlinear equation that relates the current and voltage of the panel. During operation, the PV panel can be at any point along the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I-V$</tex> characteristic defined by this equation. Catalogue data generally provide current and voltage values at three points: short-circuit, opencircuit, and maximum power under standard test conditions (STC) and nominal operating conditions (NOCT). For the purpose of PV plant modelling, the parameters <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I_{\text{ph}}, I_{0}, V_{\mathrm{t}}$</tex>, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$R_{\mathrm{s}}$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$R_{\text{sh}}$</tex> are typically estimated from catalogue data using various methods. The estimated parameters enable the determination of an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I-V$</tex> curve that typically aligns well with measurements under real-world conditions, provided the panels meet their specified characteristics. However, due to usage or improper storage, panels may degrade, leading to changes in these parameters and deviations from those estimated from catalogue data. Existing methods for capturing <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I-V$</tex> curves often involve measuring currentvoltage pairs at numerous points, making them slow and hardware-intensive. This paper investigates the estimation of real panel parameters using current and voltage at just four points on the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I-V$</tex> curve. The results show good agreement between the estimated parameters and the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I-V$</tex> curves derived from them.