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Title: Modular Approach for Continuous Cell-Level Balancing to Improve Performance of Large Battery Packs: Preprint

Energy storage systems require battery cell balancing circuits to avoid divergence of cell state of charge (SOC). A modular approach based on distributed continuous cell-level control is presented that extends the balancing function to higher level pack performance objectives such as improving power capability and increasing pack lifetime. This is achieved by adding DC-DC converters in parallel with cells and using state estimation and control to autonomously bias individual cell SOC and SOC range, forcing healthier cells to be cycled deeper than weaker cells. The result is a pack with improved degradation characteristics and extended lifetime. The modular architecture and control concepts are developed and hardware results are demonstrated for a 91.2-Wh battery pack consisting of four series Li-ion battery cells and four dual active bridge (DAB) bypass DC-DC converters.
Authors:
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Publication Date:
OSTI Identifier:
1159774
Report Number(s):
NREL/CP-5400-61263
DOE Contract Number:
AC36-08GO28308
Resource Type:
Conference
Resource Relation:
Conference: Presented at IEEE Energy Conversion Congress and Exposition, 14-18 September 2014, Pittsburgh, Pennsylvania
Research Org:
National Renewable Energy Laboratory (NREL), Golden, CO.
Sponsoring Org:
U.S. Department of Energy, Advanced Research Projects Agency-Energy (ARPA-E)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE ENERGY STORAGE; BATTERY; BATTERY PACK; MODULAR