State-of-Charge Estimation of Lithium-Ion Batteries in Parallel for Electric Vehicles Using Improved Square Root Unscented Kalman Filter

An accurate state of charge (SOC) estimation is crucial for battery applications. Traditional model-based methods have difficulty addressing parameter mismatches and measurement errors, whereas the Kalman filter method faces challenges in handling non-Gaussian noise. In this paper, an improved squar...

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Main Authors: Huakai Zhang, Jing Shi, Peixi Jiang
Format: Article
Language:English
Published: IEEE 2025-01-01
Series:IEEE Access
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Online Access:https://ieeexplore.ieee.org/document/11045903/
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author Huakai Zhang
Jing Shi
Peixi Jiang
author_facet Huakai Zhang
Jing Shi
Peixi Jiang
author_sort Huakai Zhang
collection DOAJ
description An accurate state of charge (SOC) estimation is crucial for battery applications. Traditional model-based methods have difficulty addressing parameter mismatches and measurement errors, whereas the Kalman filter method faces challenges in handling non-Gaussian noise. In this paper, an improved square root unscented Kalman filter (SRUKF) is proposed for the SOC estimation of lithium-ion batteries (LIBs). The improved SRUKF can effectively handle colored noise, and it is challenging to accurately model it owing to the mismatch between the measurement model and theoretical reference model in the process of SOC estimation. Using this method, colored noise and white noise are separated by the characteristic that the mean value of colored noise differ from that of white noise. The Kalman gain was modified according to the amplitude of the colored noise in the current and historical states, and the estimated value was closer to the real SOC than the conventional SRUKF. To better simulate the characteristics of large-capacity batteries in electric vehicles, parallel battery cells with different initial SOC values were configured for comparative simulations and experiments. Compared with the traditional SRUKF, the estimation error is reduced by 10% (pulsed-current condition) and 49% (World Transient Vehicle Cycle, WTVC) by the proposed method. The experimental results demonstrate that the improved SRUKF can overcome the influence of colored noise on the SOC estimation.
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spelling doaj-art-a962a813cdeb40e4b3eeb53d7f5c86432025-08-20T03:32:42ZengIEEEIEEE Access2169-35362025-01-011310825510826510.1109/ACCESS.2025.358190311045903State-of-Charge Estimation of Lithium-Ion Batteries in Parallel for Electric Vehicles Using Improved Square Root Unscented Kalman FilterHuakai Zhang0https://orcid.org/0000-0002-4290-6359Jing Shi1https://orcid.org/0009-0008-0513-7061Peixi Jiang2School of Automotive and Mechanical Engineering, Liaoning Institute of Science and Engineering, Jinzhou, ChinaSchool of Automotive and Mechanical Engineering, Liaoning Institute of Science and Engineering, Jinzhou, ChinaSchool of Physical Sciences, University of California at San Diego, San Diego, CA, USAAn accurate state of charge (SOC) estimation is crucial for battery applications. Traditional model-based methods have difficulty addressing parameter mismatches and measurement errors, whereas the Kalman filter method faces challenges in handling non-Gaussian noise. In this paper, an improved square root unscented Kalman filter (SRUKF) is proposed for the SOC estimation of lithium-ion batteries (LIBs). The improved SRUKF can effectively handle colored noise, and it is challenging to accurately model it owing to the mismatch between the measurement model and theoretical reference model in the process of SOC estimation. Using this method, colored noise and white noise are separated by the characteristic that the mean value of colored noise differ from that of white noise. The Kalman gain was modified according to the amplitude of the colored noise in the current and historical states, and the estimated value was closer to the real SOC than the conventional SRUKF. To better simulate the characteristics of large-capacity batteries in electric vehicles, parallel battery cells with different initial SOC values were configured for comparative simulations and experiments. Compared with the traditional SRUKF, the estimation error is reduced by 10% (pulsed-current condition) and 49% (World Transient Vehicle Cycle, WTVC) by the proposed method. The experimental results demonstrate that the improved SRUKF can overcome the influence of colored noise on the SOC estimation.https://ieeexplore.ieee.org/document/11045903/Improved square root unscented Kalman filterslow-changing colored noisebattery cells in parallelstate of charge model mismatch
spellingShingle Huakai Zhang
Jing Shi
Peixi Jiang
State-of-Charge Estimation of Lithium-Ion Batteries in Parallel for Electric Vehicles Using Improved Square Root Unscented Kalman Filter
IEEE Access
Improved square root unscented Kalman filter
slow-changing colored noise
battery cells in parallel
state of charge model mismatch
title State-of-Charge Estimation of Lithium-Ion Batteries in Parallel for Electric Vehicles Using Improved Square Root Unscented Kalman Filter
title_full State-of-Charge Estimation of Lithium-Ion Batteries in Parallel for Electric Vehicles Using Improved Square Root Unscented Kalman Filter
title_fullStr State-of-Charge Estimation of Lithium-Ion Batteries in Parallel for Electric Vehicles Using Improved Square Root Unscented Kalman Filter
title_full_unstemmed State-of-Charge Estimation of Lithium-Ion Batteries in Parallel for Electric Vehicles Using Improved Square Root Unscented Kalman Filter
title_short State-of-Charge Estimation of Lithium-Ion Batteries in Parallel for Electric Vehicles Using Improved Square Root Unscented Kalman Filter
title_sort state of charge estimation of lithium ion batteries in parallel for electric vehicles using improved square root unscented kalman filter
topic Improved square root unscented Kalman filter
slow-changing colored noise
battery cells in parallel
state of charge model mismatch
url https://ieeexplore.ieee.org/document/11045903/
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AT jingshi stateofchargeestimationoflithiumionbatteriesinparallelforelectricvehiclesusingimprovedsquarerootunscentedkalmanfilter
AT peixijiang stateofchargeestimationoflithiumionbatteriesinparallelforelectricvehiclesusingimprovedsquarerootunscentedkalmanfilter