Scale electro-thermal model of a lithium-ion battery for time-accelerated experiments in a hardware in the loop process

Abstract

A scale electro-thermal model has been developed for LiFePO4/graphite lithium-ion battery. Such model is appropriate in order to develop a physical emulation of a battery in the context of a hardware in the loop process, especially for testing energy management strategies of microgrids under the same conditions (solar irradiation for PV arrays, wind speed for wind turbine, state of health for storage device) and potentially by compressing testing time. Classically, physical emulation allows achieving laboratory size-scaled analysis but one major originality of the proposed approach deals with the “time-compressed experimental analysis”. The electro-thermal model is based on the extended modified shepherd model coupled with a 1D thermal model. The model parameters are estimated through a sequential characterization approach from several input profiles such as the hybrid pulse power characterization protocol and the open circuit voltage measurement. Both the dimensional analysis and the Vaschy-Buckingham theorem are used to obtain the scaling factors (voltage, current, “but also” time) which are applied on the original model parameters. The accuracy of the scale electro-thermal model is validated on a robustness analysis (the battery current profile is based on a specific energy management strategy for a typical microgrid application) with voltage, current and time scaling. The simulation results presented in the paper show that the reduction of the time horizon of experimental tests for HIL process is possible by means of an appropriate dimensional analysis (scaling) on the model parameters.