An Eight-Parameter Adaptive Model for the Single Diode Equivalent Circuit Based on the Photovoltaic Module's Physics

Abstract

This paper proposes an eight-parameter adaptive electrical model based on the physical behavior of the photovoltaic (PV) module with respect to variations of the environmental conditions. In addition, an accurate parameter estimation technique is proposed for this new model based on the pattern search optimization algorithm. The usual characterization of the I–V curves has five unknown parameters. The majority of the estimation techniques identify those five parameters for a specific irradiance and temperature. This means that different sets of five parameters are found for each environmental condition, i.e., the estimated parameters are based only on a mathematical fitting with lack of physical meaning. In the proposed eight-parameter adaptive model, it is necessary to execute the parameter estimation technique only once, because the model is valid for all ranges of values of the environmental conditions available on datasheets or experimental curves. Moreover, the restrictions imposed on each parameter make the model capable of emulating the physical behavior of the PV module, particularly useful in fault diagnosis and predictive and corrective maintenance of PV systems. Comparison results based on datasheet and experimental curves are presented to verify the effectiveness of the proposed model and parameter estimation technique.