Optimal SoC Balancing Control for Lithium-Ion Battery Cells Connected in Series

Chi Nguyen Van, Thuy Nguyen Vinh, Minh-Duc Ngo and Seon-Ju Ahn
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Chi Nguyen Van: Institute of High-Technology Research and Development for Industry (RIAT), Thai Nguyen University of Technology (TNUT), 666, 3/2 Street, Tich Luong Ward, Thai Nguyen City 251750, Vietnam
Thuy Nguyen Vinh: Department of Automation, Thai Nguyen University of Technology (TNUT), 666, 3/2 Street, Tich Luong Ward, Thai Nguyen City 251750, Vietnam
Minh-Duc Ngo: Department of Automation, Thai Nguyen University of Technology (TNUT), 666, 3/2 Street, Tich Luong Ward, Thai Nguyen City 251750, Vietnam
Seon-Ju Ahn: Department of Electrical Engineering, Chonnam National University, Gwangju 61186, Korea

Energies, 2021, vol. 14, issue 10, 1-18

Abstract: The optimal state of charge (SoC) balancing control for series-connected lithium-ion battery cells is presented in this paper. A modified SoC balancing circuit for two adjacent cells, based on the principle of a bidirectional Cuk converter, is proposed. The optimal SoC balancing problem is established to minimize the SoC differences of cells and the energy loss subject to constraints of the normal SoC operating range, the balancing current, and current of cells. This optimization problem is solved using the sequential quadratic programming algorithm to determine the optimal duties of PWM signals applied to the SoC balancing circuits. An algorithm for the selection of the initial points for the optimal problem-solving process is proposed. It is applied in cases where the cost function has no decreasing part. Experimental tests are conducted for seven series-connected Samsung cells. The optimal SoC balancing control and SoC estimation algorithms are coded in MATLAB and embedded in LabVIEW to control the SoC balancing in real time. The test results show that the differences between the SoCs of cells converges to the desired range using the proposed optimal SoC balancing control strategy.

Keywords: lithium-ion battery; state of charge; optimal control; bidirectional Cuk converter; SoC balancing control (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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