Performance Analysis of a Single-Diode Photovoltaic Model Based on a Thevenin’s Equivalent Circuit

This article proposes a linear Thevenin's equivalent circuit for a single-diode model. The Thevenin's equivalent circuit is derived based on the piecewise linearization for the nonlinear characteristic of the diode. To validate the accuracy and efficiency of the proposed Thevenin approximation, a photovoltaic module’s current-voltage and power-voltage characteristics are evaluated and compared with the characteristics of the original model. Meanwhile, an error of the proposed approximation is also calculated under different values of irradiance and temperature. The operating conditions are classified into three scenarios: standard technical condition (irradiance=1000 W/m2, temperature=25 oC), (irradiance=400 W/m2, temperature=25 oC), and (irradiance=1000 W/m2, temperature=50 oC). Primary results show encouraging outputs and reliability of the proposed model. It is obvious from the simulation results that the linearization technique can successfully emulate the characteristics of the original nonlinear single-diode model. The peak values of the error are 7.37%, 9.51%, and 6.79% at the different suggested scenarios, respectively. Subsequently, the proposed Thevenin equivalent circuit can be successfully used to study the performance of a photovoltaic system under different operating conditions, avoiding the complicated numerical solutions for nonlinear equations of the original photovoltaic model.