Real-Time State of Power Estimation of a Lithium-Ion Battery Using Robust OCV and Internal Resistance Estimates

This article considers the problem of estimating the state of power (SOP) of a battery in real time. The SOP refers to maximum power that a battery can absorb or release during charging and discharging, respectively. The SOP is determined using the open circuit voltage (OCV) and internal resistance of the battery, both of which change with the state of charge (SOC). Existing approaches employ nonlinear system identification techniques that require the knowledge of the battery parameters, especially the parameters of the OCV–SOC characteristics. Further, the estimates of SOP from existing approaches are sensitive to factors such as temperature, SOC, aging, and OCV–SOC characterization parameters. This article presents a novel approach to SOP estimation based on a novel observation model that is independent of temperature, SOC, aging, and OCV–SOC characterization parameters. The proposed approach does not require nonlinear approaches for both system identification and filtering; instead, a linear least squares estimation technique is utilized to estimate the two parameters needed for SOP computation. The SOP estimates computed through the proposed approach are tested using realistic battery data collected from three battery cells at the following eight different temperatures: <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-\text{25}\,^\circ {\text{C}}$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-\text{15}\,^\circ {\text{C}}$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-\text{5}\,^\circ {\text{C}}$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{5}\,^\circ {\text{C}}$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{15}\,^\circ {\text{C}}$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{25}\,^\circ {\text{C}}$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{35}\,^\circ {\text{C}}$</tex-math></inline-formula>, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{45}\,^\circ {\text{C}}$</tex-math></inline-formula>. From this analysis, it was observed that the proposed SOP estimation technique exhibited an SOP estimation error of 0.5 W across all the chosen temperatures except for very low SOC regions.