Lookup NU author(s): Dr Simon Lambert,
Professor Volker Pickert,
Dr Dave Atkinson,
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.
Author(s): Lambert SM, Pickert V, Atkinson DJ, Zhan H
Publication type: Article
Publication status: Published
Journal: IEEE Transactions on Power Electronics
Online publication date: 15/05/2015
Acceptance date: 06/04/2015
ISSN (print): 0885-8993
ISSN (electronic): 1941-0107
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