Stability Analysis of Converter-Connected Battery Energy Storage Systems in the Grid

This paper analyzes the stability of a battery energy storage system (BESS) connected to the grid using a power-electronic interface. It is shown that the internal resistance and internal voltage of the battery affect system stability. Variations in these parameters may occur due to aging and changes in the state-of-charge (SoC). Using average-value modeling, this problem is framed into a nonlinear system formulation and the region of stability as a function of the internal resistance and the internal voltage of the battery is determined. This paper also extends its results in determining the configuration of a battery pack in terms of the number of battery cells in series and parallel to prevent instability while meeting demand power requirements. The findings are useful both in the design and operation stages of large-scale battery storage systems in the grid.