A non-linear dynamic electrical model of Sodium-Nickel Chloride Batteries

In this paper a non-linear second order circuit model of high temperature Sodium-Nickel Chloride batteries (SNBs) is presented. The aim is the development of an accurate model easily implementable in microgrids Energy Management System and suitable for their real-time control. The proposed model is based on the analysis of the experimental performance of a commercial 23.5 kWh SNB. In particular, the mathematical description of the used algorithm, the model parameters identification method as well as the measurement tests carried out for their evaluation are reported and discussed in detail. Then, the model is validated using a measured current-voltage profile, developed in order to trigger the whole battery operative range. The comparison between the experimental data and simulations has confirmed the good accuracy of the proposed model in a defined SOC range. However, due to the particular chemical composition of the battery positive electrode, a novel modelling approach specific for the SNB technology has been finally demonstrated to be necessary.