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http://dx.doi.org/10.6113/JPE.2015.15.3.775

Development of an Optimized Algorithm for Bidirectional Equalization in Lithium-Ion Batteries  

Sun, Jinlei (Department of Electrical Engineering and Automation, Harbin Institute of Technology)
Zhu, Chunbo (Department of Electrical Engineering and Automation, Harbin Institute of Technology)
Lu, Rengui (Department of Electrical Engineering and Automation, Harbin Institute of Technology)
Song, Kai (Department of Electrical Engineering and Automation, Harbin Institute of Technology)
Wei, Guo (Department of Electrical Engineering and Automation, Harbin Institute of Technology)
Publication Information
Journal of Power Electronics / v.15, no.3, 2015 , pp. 775-785 More about this Journal
Abstract
Many equalization circuits have been proposed to improve pack performance and reduce imbalance. Although bidirectional equalization topologies are promising in these methods, pre-equalization global equalization strategy is lacking. This study proposes a novel state-of-charge (SoC) equalization algorithm for bidirectional equalizer based on particle swarm optimization (PSO), which is employed to find optimal equalization time and steps. The working principle of bidirectional equalization topologies is analyzed, and the reason behind the application of SoC as a balancing criterion is explained. To verify the performance of the proposed algorithm, a pack with 12 LiFePO4 batteries is applied in the experiment. Results show that the maximum SoC gap is within 2% after equalization, and the available pack capacity is enhanced by 13.2%. Furthermore, a comparison between previously used methods and the proposed PSO equalization algorithm is presented. Experimental tests are performed, and results show that the proposed PSO equalization algorithm requires fewer steps and is superior to traditional methods in terms of equalization time, energy loss, and balancing performance.
Keywords
Cell inconsistency; Bidirectional equalization; Equalization strategy; State of charge; Particle swarm optimization;
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