Multiobjective Optimization of Data-Driven Model for Lithium-Ion Battery SOH Estimation with Short-term Feature

As a favorable energy storage component, Lithium-ion (Li-ion) battery has been widely used in the Battery Energy Storage Systems (BESS) and Electric Vehicles (EV). Data driven methods estimate the battery State of Health (SOH) with the features extracted from the measurement. However, excessive features may reduce the estimation accuracy and also increases the human labor in the lab. By proposing an optimization process with Non-dominated Sorting Genetic Algorithm II (NSGA-II), this paper is able to establish a more efficient SOH estimator with Support Vector Regression (SVR) and the short-term features from the current pulse test. NSGA-II optimizes the entire process of establishing a SOH estimator considering both the measurement cost of the feature and the estimation accuracy. A series of non-dominated solutions are obtained by solving the multi-objective optimization problem, which also provides more flexibility to establish the SOH estimator at various conditions. The degradation features in this paper are the knee points at the transfer instants of the voltage in the short-term current pulse test, which is fairly convenient and easy to be obtained in real applications. The proposed method is validated on the measurement from two LiFePO4/C batteries aged with the mission profile providing the Primary Frequency Regulation (PFR) service to the grid.