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Transformer based equalisation circuit applied to n-number of high capacitance cells

Lookup NU author(s): Dr Simon LambertORCiD, Professor Volker Pickert, Dr Dave Atkinson, summer Zhan



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Over the last decade various high capacitance devices have become available on the market such as supercapacitors, ultracapacitors and recently, Li-ion capacitors. The cell voltage limit of each of these technologies is a small percentage of the system level voltage so they must therefore be connected in series to attain a high voltage. During charging and discharging, manufacturing tolerances between the cells result in voltage mismatch across the stack. Mismatched voltages are an inefficient use of the energy storage medium and can lead to dangerous failures in the cells if voltages exceed safety limits. Transformer based voltage equalisation techniques are the preferred circuit topologies in applications with low system voltage due to simplicity of control and low number of switches. The drawback of these circuits is the number of isolated windings which are required on a single core. This paper describes for the first time a solution to that problem by using a classical two windings transformer that in principal can be applied to any number of capacitors. The paper describes the operation of the circuit, shows simulation results and practical results based on a prototype with 5 cells.

Publication metadata

Author(s): Lambert SM, Pickert V, Atkinson DJ, Zhan H

Publication type: Article

Publication status: Published

Journal: IEEE Transactions on Power Electronics

Year: 2016

Volume: 31

Issue: 2

Pages: 1334-1343

Print publication date: 01/02/2016

Online publication date: 15/05/2015

Acceptance date: 06/04/2015

Date deposited: 13/04/2015

ISSN (print): 0885-8993

ISSN (electronic): 1941-0107

Publisher: IEEE


DOI: 10.1109/TPEL.2015.2424075


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