Abstract

The state-of-charge (SOC) is a fundamental indicator representing the remaining capacity of lithium-ion batteries, which plays an important role in the battery’s optimized operation. In this paper, the model-based SOC estimation strategy is studied for batteries. However, the battery’s model parameters need to be extracted through cumbersome prior experiments. To remedy such deficiency, a recursive least squares (RLS) algorithm is utilized for model parameter online identification, and an adaptive square-root unscented Kalman filter (SRUKF) is designed to estimate the battery’s SOC. As demonstrated in extensive experimental results, the designed adaptive SRUKF combined with RLS-based model identification is a promising SOC estimation approach. Compared with other commonly used Kalman filter-based methods, the proposed algorithm has higher precision in the SOC estimation.

Highlights

  • Rechargeable lithium-ion batteries have been widely used in numerous applications due to their superior power performance, long life cycle, and so forth [1,2]

  • An adaptive square-root unscented Kalman filter (SRUKF) based on this online identified battery model is developed to estimate the battery’s SOC, where a noise statistic estimator is utilized for the noise information online update

  • To validate the performance of the designed adaptive SRUKF with recursive least squares (RLS)-based model parameters online identification on battery SOC estimation, an IFP36130155-36Ah lithium-ion battery with a nominal capacity of 36 Ah [26] was chosen for the experiment

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Summary

Introduction

Rechargeable lithium-ion batteries have been widely used in numerous applications due to their superior power performance, long life cycle, and so forth [1,2]. A UKF algorithm is developed to estimate the SOC with another adaptive UKF utilized for the online identification of the model parameters of the battery in [24]. (2) Extensive experiments demonstrate the effectiveness of the proposed charging strategy showing that the proposed adaptive SRUKF can provide higher SOC estimation accuracy compared with other commonly used Kalman filter-based methods. The rest of this manuscript is arranged as follows.

Battery Equivalent Circuit Model
Model Discretization
Observability Analysis
Model Parameter Identification with Rls Algorithm
Adaptive Square-Root Ukf Based Soc Estimation
Experimental Results
Conclusions

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