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Open AccessArticle

Flexible Grouping for Enhanced Energy Utilization Efficiency in Battery Energy Storage Systems

National Active Distribution Network Technology Research Center (NANTEC), Beijing Jiaotong University, Beijing 100044, China
Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing Jiaotong University, Beijing 100044, China
Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI 48202, USA
The Key Laboratory of Systems and Control of CAS, Institute of Systems Science, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100190, China
Author to whom correspondence should be addressed.
Academic Editor: Sheng S. Zhang
Energies 2016, 9(7), 498;
Received: 3 May 2016 / Revised: 22 June 2016 / Accepted: 24 June 2016 / Published: 29 June 2016
PDF [4653 KB, uploaded 29 June 2016]


As a critical subsystem in electric vehicles and smart grids, a battery energy storage system plays an essential role in enhancement of reliable operation and system performance. In such applications, a battery energy storage system is required to provide high energy utilization efficiency, as well as reliability. However, capacity inconsistency of batteries affects energy utilization efficiency dramatically; and the situation becomes more severe after hundreds of cycles because battery capacities change randomly due to non-uniform aging. Capacity mismatch can be solved by decomposing a cluster of batteries in series into several low voltage battery packs. This paper introduces a new analysis method to optimize energy utilization efficiency by finding the best number of batteries in a pack, based on capacity distribution, order statistics, central limit theorem, and converter efficiency. Considering both battery energy utilization and power electronics efficiency, it establishes that there is a maximum energy utilization efficiency under a given capacity distribution among a certain number of batteries, which provides a basic analysis for system-level optimization of a battery system throughout its life cycle. Quantitative analysis results based on aging data are illustrated, and a prototype of flexible energy storage systems is built to verify this analysis. View Full-Text
Keywords: battery; flexible group; converter efficiency; energy utilization efficiency battery; flexible group; converter efficiency; energy utilization efficiency

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Diao, W.; Jiang, J.; Liang, H.; Zhang, C.; Jiang, Y.; Wang, L.; Mu, B. Flexible Grouping for Enhanced Energy Utilization Efficiency in Battery Energy Storage Systems. Energies 2016, 9, 498.

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