Universal state of charge estimator for battery packs of battery energy storage systems

Battery energy storage system (BESS) is an ideal solution for managing intermittent renewable sources such as photo voltaic (PV) panels and wind turbines connected to grids or micro grids. Their optimized performance is very dependent on accurate estimation of BESS´s state of charge (SOC). This accurate estimation is vital for the operating scheme decisions of any BESS. This paper presents a universal method to accurately estimate the SOC for battery packs used in BESSs. Online estimated model parameters are used to update electrical melectrical modelodel of each single cell in the battery pack of the BESS. The algorithm´s low estimation error and reduced computational requirements, makes it practical for on board estimations. SOC estimation error along with voltage estimation error for a pack of Li-ion batteries are presented to show the accuracy of the algorithm.