Rapid State-of-Power Estimation of Lithium-Ion Battery Packs in DC Microgrids

Lithium-ion (Li-ion) batteries are widely used as energy storage systems in DC microgrids. Effective and lifetime-prolonging operation of Li-ion batteries requires continuous monitoring and control of their operating conditions. One important state parameter in this context is the state of power (SOP), which describes the battery's ability to supply a load under specified constraints. In this work, an SOP estimation method based on rapid online battery impedance measurements is proposed. The method utilizes impedance measurement data to evaluate the effects of both internal resistance and charge accumulation on the battery cell terminal voltage. The proposed SOP estimation approach is independent of prior battery measurement data and does not rely on the estimation of other state parameters, such as the state of charge (SOC). Experimental measurements on commercial Li-ion battery cells using bi-directional load currents and peak current pulses were conducted to evaluate the performance of the proposed SOP estimation method. The method predicts the battery voltage with a maximum root mean square error of 13.07 mV across all bi-directional current tests and predicts the peak current pulse voltage with a root mean square error of 5.27 mV. This work is a revised and extended version of a presentation at ICDCM [L. Lignell] et al., 2025.