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Article

Series-Parallel Reconfiguration Technique with Voltage Equalization Capability for Electric Double-Layer Capacitor Modules

1
College of Engineering, Ibaraki University, Hitachi 316-8511, Japan
2
Fanuc Corporation, Yamanashi 401-0597, Japan
3
Seiko Epson Corporation, Nagano 392-8502, Japan
*
Author to whom correspondence should be addressed.
Energies 2019, 12(14), 2741; https://doi.org/10.3390/en12142741
Received: 18 June 2019 / Revised: 15 July 2019 / Accepted: 16 July 2019 / Published: 17 July 2019
(This article belongs to the Section D: Energy Storage and Application)
Voltage variations of electric double-layer capacitors (EDLCs) are rather wider than those of traditional rechargeable batteries, and an energy utilization ratio of EDLCs is dependent on cells’ voltage variation ranges. To satisfactorily utilize EDLCs’ energies, voltages of EDLC modules should be within a certain range, while cells need to be charged and discharged over the wide voltage range. To this end, various kinds of series-parallel reconfiguration techniques based on balance- and unbalance-shift circuits have been proposed, but conventional techniques can only be applied to modules consisting of even number cells, impairing the design flexibility and scalability. With the unbalance-shift circuits, cell voltages are unavoidably mismatched due to unequal currents, resulting in reduced energy utilization ratios. This article proposes a novel series-parallel reconfiguration technique with voltage equalization capability for EDLC modules. The proposed technique can be applied to any number of cells, improving design flexibility and scalability. Furthermore, since the proposed circuit behaves as a switched capacitor converter, in which all cells are virtually connected in parallel, cells are equally charged and discharged without causing voltage imbalance, realizing the improved energy utilization ratio. A prototype for an EDLC module comprising four cells, each with a rated charging voltage of 2.5 V, was built and experimentally tested. The module voltage varied in the range of 3.2–5.0 V, while all cells were uniformly discharged down to as low as 0.8 V, achieving the energy utilization ratio of 90%. View Full-Text
Keywords: electric double-layer capacitor (EDLC); series-parallel reconfiguration; switched capacitor converter; voltage equalization electric double-layer capacitor (EDLC); series-parallel reconfiguration; switched capacitor converter; voltage equalization
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MDPI and ACS Style

Uno, M.; Iwasaki, K.; Hasegawa, K. Series-Parallel Reconfiguration Technique with Voltage Equalization Capability for Electric Double-Layer Capacitor Modules. Energies 2019, 12, 2741. https://doi.org/10.3390/en12142741

AMA Style

Uno M, Iwasaki K, Hasegawa K. Series-Parallel Reconfiguration Technique with Voltage Equalization Capability for Electric Double-Layer Capacitor Modules. Energies. 2019; 12(14):2741. https://doi.org/10.3390/en12142741

Chicago/Turabian Style

Uno, Masatoshi, Koyo Iwasaki, and Koki Hasegawa. 2019. "Series-Parallel Reconfiguration Technique with Voltage Equalization Capability for Electric Double-Layer Capacitor Modules" Energies 12, no. 14: 2741. https://doi.org/10.3390/en12142741

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