Double-diode and triple-diode solar cell models: invertible approximate analytical expressions based on the g-function approach

Solar cells can be represented by different n-diode models. The most commonly used models are single-diode (SDM), double-diode (DDM), and triple-diode (TDM). The SDM is the simplest and most widely used model with reversible current (I)-voltage (V) expressions. The DDM and TDM are more precise models, but only a few approximate analytical Lambert W approaches are available for current‒voltage (I–V) expressions in the literature. This paper presents approximate analytical invertible voltage‒current expressions (V–I) for DDM and TDM via a g-function. Moreover, this paper presents a new formula for calculating the root mean square error (RMSE) in voltage estimation based on the derived expressions. It also demonstrates the limitations of the Lambert W function and the numerical unsolvability of its solution through examples for these purposes. In addition, the paper discusses and tests analytical and iterative solutions for solving the g-function and provides the MATHEMATICA code for DDM and TDM V–I expressions via the g-function. Therefore, this paper confirms the effectiveness and accuracy of using the g-function in solar cell modeling.