Modelling Li-ion batteries using equivalent circuits for renewable energy applications

Abstract

During the last decades, environmental policies have advanced the promotion of renewable energy sources, opening a market for smart-grids both connected and disconnected from the main electrical grid. In the field of renewable energies, such as solar or wind ones, batteries are an essential component since they allow to easily store the energy excess that can be dispensed during periods of scarcity of these sources. This paper presents a dynamic Li-ion battery model for renewable purposes based on an electrical equivalent circuit model. This model takes into account both charge and discharge processes using the same equation, while most models found in the literature only contemplate the discharge process. Several tests were carried out in an experimental micro-grid bench at different state of charge to adjust the model parameters including the non-linear relation between the state of charge and the open circuit voltage. Finally, different experiments were performed to experimentally validate the model. The model predicts, with a low error, the battery voltage as well as the state of charge.