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Modeling and Analysis of the Interaction of Batteries and Power Electronic Converters
KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. (EmadLab)ORCID iD: 0000-0002-9481-7366
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the interaction of batteries and power electronic converters in automotive applications. Even if the additional heating caused by (unwanted) alternating currents is disregarded, there has been a concern that alternating currents can be harmful for batteries. For that reason, alternating currents can be filtered using capacitors and/or by sophisticated hardware. In this work, the concern whether alternating currents are harmful to batteries is studied particular focus on large, lithium-ion cells for use in automotive applications.First, the harmonic content in the battery current of two, commercial hybrid-electric busses were measured and analysed. The most prominent harmonic had a peak magnitude higher than 10% of the maximum direct current level (160 A) arising at frequencies below 150 Hz. The maximum amplitude detected of a harmonic caused by the voltage source converter’s switching action was around 10 A and occurred at a frequency of 2 kHz. An experimental setup with alternating current capability for evaluating large lithium-ion cells has been designed and built. Twelve lithium-ion cells were cycled at a rate if 1 C during approximately 2000 cycles (corresponding to approximately one year). The cells were cycled with an superimposed alternating current of 1 Hz, 100 Hz, or 1 kHz while the rest of the cells were cycled with direct current (only), injected with alternating current (only), or no current at all (calendar aging). No negative effects caused by the alternating current was identified in terms of capacity fade and power fade for the tested lithium-ion cells. A comparison between sinusoidal current-ripple charging and conventional constant-current constant-voltage charging was also carried out. Three lithium-ion cells were cycled (ten times) with different ac currents superimposed during charge. The results were analyzed statistically and no significant improvements in terms of charging time or charging efficiency were observed in any of the charging tests using an superimposed ac current. The injection of alternating currents into batteries for heating purposes has also been studied and a control method for battery heating using an ac current was proposed. The proposed controller is applicable regardless of the LIB’s subsequent impedance nature (capacitive, inductive or resistive). Further, a design process for the generation of magnified alternating currents in dc-dc converters was presented. By matching the switching frequency with the frequency where the LCL filter and the battery resonate, the current flowing in the semiconductors and the switching frequency could be reduced. In a small experimental setup using a single lithium-ion cell, using an LCL-resonant circuit and a full bridges witch arrangement, magnifications of up to 15.7 were reached. This allowed for a loss reduction in the semiconductors of up to 75%, when compared to an equivalent dc-dc converter enabled to produce anon-magnified ac current. 

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2019. , p. 184
Series
TRITA-EECS-AVL ; 2019:45
Keywords [en]
Alternating current, aging, electric vehicles, harmonics, lithium-ion batteries, power converter, resonant filters, ripple, temperature control.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-251665ISBN: 978-91-7873-187-9 (print)OAI: oai:DiVA.org:kth-251665DiVA, id: diva2:1316369
Public defence
2019-06-05, Kollegiesalen, Brinellvägen 8, Kungliga Tekniska högskolan, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20190517

Available from: 2019-05-17 Created: 2019-05-17 Last updated: 2019-06-17Bibliographically approved
List of papers
1. Measurements and analysis of battery harmonic currents in a commercial hybrid vehicle
Open this publication in new window or tab >>Measurements and analysis of battery harmonic currents in a commercial hybrid vehicle
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2017 (English)In: 2017 IEEE Transportation and Electrification Conference and Expo, ITEC 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 45-50Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, the harmonic content of the battery current in a commercial hybrid vehicle (bus) is measured and analyzed for a number of different driving situations. It is found that the most prominent harmonic reaches peak magnitudes that can be higher than 10% of the maximum dc-current level with a maximum frequency less than 150 Hz. Further, it is found that this harmonic can be approximated using a fitted, simple analytical expression with reasonable agreement for all driving situations considered.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2017
Keywords
DC-link, Harmonic currents, Hybrid vehicles, Lithium-ion batteries, Permanent-magnet synchronous machine, Ripple, Voltage source inverter, Commercial vehicles, Electric batteries, Electric inverters, Electric utilities, Harmonic analysis, Lithium compounds, Permanent magnets, Secondary batteries, Vehicles, DC links, Permanent magnet synchronous machines
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-216277 (URN)10.1109/ITEC.2017.7993245 (DOI)000427121300009 ()2-s2.0-85028594346 (Scopus ID)9781509039043 (ISBN)
Conference
2017 IEEE Transportation and Electrification Conference and Expo, ITEC 2017, 22 June 2017 through 24 June 2017
Note

QC 20171213

Available from: 2017-12-13 Created: 2017-12-13 Last updated: 2019-05-17Bibliographically approved
2. Analysis and Prediction of the Harmonic Content in the Battery Currentof a Commercial Hybrid-Electric Bus
Open this publication in new window or tab >>Analysis and Prediction of the Harmonic Content in the Battery Currentof a Commercial Hybrid-Electric Bus
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(English)In: IEEE Transactions on Transportation ElectrificationArticle in journal (Refereed) Submitted
Abstract [en]

This paper presents a comparison of the harmoniccontent in the battery current in two, commercialhybrid electric vehicles (HEVs) (intercity passenger buses)when operated in realistic drive scenarios. These harmonicscan contribute to issues related to electromagnetic compatibilityand indirectly accelerate the aging of the battery dueto elevated cell temperatures caused by associated ohmiclosses. A key finding is that low-frequency harmonics (upto approximately 130 Hz) attributed to resolver eccentricityand non-ideal effects in the voltage-source inverter (VSI) (upto approximately 260 Hz) were significant in terms of magnitudes.Also, the variation between the two HEVs (in termsof current magnitude) were substantial for these harmonics.This is an important observation since it demonstratesthat significant, low-frequency harmonics can be presentin the battery current and that modeling and collectingexperimental data from a single corresponding vehicle maynot sufficiently represent the harmonic content in the batterycurrent for a fleet of vehicles.

Keywords
Dc-link, harmonic currents, hybrid electric vehicles, lithium-ion batteries, permanent-magnet synchronous machines, ripple, voltage source inverter
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-251662 (URN)
Funder
Swedish Energy Agency, 37434-1
Note

QC 20190520

Available from: 2019-05-17 Created: 2019-05-17 Last updated: 2019-05-20Bibliographically approved
3. Design Aspects of an Experimental Setup for Investigating Current Ripple Effects in Lithium-ion Battery Cells
Open this publication in new window or tab >>Design Aspects of an Experimental Setup for Investigating Current Ripple Effects in Lithium-ion Battery Cells
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2015 (English)In: Power Electronics and Applications (EPE'15 ECCE-Europe), 2015 17th European Conference on, IEEE conference proceedings, 2015, p. 1-8Conference paper, Published paper (Refereed)
Abstract [en]

This paper describes an experimental setup for investigating the effects of current ripple on lithium-ion battery cells. The experimental setup is designed so that twelve li-ion cells can be simultaneously tested in a controlled environment. The experimental setup allows for a wide range of current ripple in terms of frequency and amplitude. Additionally, the quantification of the current ripple effects such as the aging of li-ion cells implies that a precise measurement system has to be designed which also are discussed in the paper.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2015
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-178001 (URN)10.1109/EPE.2015.7309112 (DOI)000377101800063 ()2-s2.0-84965074464 (Scopus ID)
Conference
Power Electronics and Applications (EPE'15 ECCE-Europe), 8-10 Sept. 2015, Geneva,
Funder
Swedish Energy AgencyStandUp
Note

QC 20160216

Available from: 2015-12-01 Created: 2015-12-01 Last updated: 2019-05-17Bibliographically approved
4. An Experimental Setup with Alternating Current Capability for Evaluating Large Lithium-ion Batteries Cells
Open this publication in new window or tab >>An Experimental Setup with Alternating Current Capability for Evaluating Large Lithium-ion Batteries Cells
Show others...
(English)Manuscript (preprint) (Other academic)
Keywords
Alternating current, aging, battery testing, electric vehicles, GITT, HPPC, life cycle, lithium-ion batteries, ripple, SOC
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-228024 (URN)
Note

QC 20180518

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2019-05-17Bibliographically approved
5. Challenging Sinusoidal Ripple-Current Charging of Lithium-Ion Batteries
Open this publication in new window or tab >>Challenging Sinusoidal Ripple-Current Charging of Lithium-Ion Batteries
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2018 (English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 65, no 6, p. 4750-4757Article in journal (Refereed) Published
Abstract [en]

Sinusoidal ripple-current charging has previously been reported to increase both charging efficiency and energy efficiency and decrease charging time when used to charge lithium-ion battery cells. In this paper, we show that no such effect exists in lithium-ion battery cells, based on an experimental study of large-size prismatic cells. Additionally, we use a physics-based model to show that no such effect should exist, based on the underlying electrochemical principles.

Place, publisher, year, edition, pages
IEEE Press, 2018
Keywords
Fast charging, lithium-ion (Li-ion) battery, sinusoidal ripple charging
National Category
Other Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-223315 (URN)10.1109/TIE.2017.2772160 (DOI)000425618900031 ()2-s2.0-85034238750 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20180222

Available from: 2018-02-16 Created: 2018-02-16 Last updated: 2019-05-17Bibliographically approved
6. Aging effects of AC harmonics on lithium-ion cells
Open this publication in new window or tab >>Aging effects of AC harmonics on lithium-ion cells
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2019 (English)In: Journal of Energy Storage, E-ISSN 2352-152X, Vol. 21, p. 741-749Article in journal (Refereed) Published
Abstract [en]

With the vehicle industry poised to take the step into the era of electric vehicles, concerns have been raised that AC harmonics arising from switching of power electronics and harmonics in electric machinery may damage the battery. In light of this, we have studied the effect of several different frequencies on the aging of 28 Ah commercial NMC/graphite prismatic lithium-ion battery cells. The tested frequencies are 1 Hz, 100 Hz, and 1 kHz, all with a peak amplitude of 21 A. Both the effect on cycled cells and calendar aged cells is tested. The cycled cells are cycled at a rate of 1C:1C, i.e., 28 A during both charging and discharging, with the exception of a period of constant voltage at the end of every charge. After running for one year, the cycled cells have completed approximately 2000 cycles. The cells are characterized periodically to follow how their capacities and power capabilities evolve. After completion of the test about 80% of the initial capacity remained and no increase in resistance was observed. No negative effect on either capacity fade or power fade is observed in this study, and no difference in aging mechanism is detected when using non-invasive electrochemical methods of post mortem investigation.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Lithium-ion, ripple-current, harmonics, aging
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Chemical Engineering
Research subject
Electrical Engineering; Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-241643 (URN)10.1016/j.est.2018.12.016 (DOI)000459203100066 ()2-s2.0-85060290744 (Scopus ID)
Note

QC 20190125

Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-05-17Bibliographically approved
7. A Control Method for Battery Heating Using Alternating Current
Open this publication in new window or tab >>A Control Method for Battery Heating Using Alternating Current
Show others...
(English)Manuscript (preprint) (Other academic)
Keywords
Current control, electric model, injection of alternate current, internal heat, lithium-ion batteries, packaging, ripple, temperature control, thermal model
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-228027 (URN)
Note

QC 20180518

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2019-05-17Bibliographically approved
8. Integration of Magnified Alternating Current in Battery Fast Chargers based on DC-DC Converters using Transformerless Resonant Filter Design
Open this publication in new window or tab >>Integration of Magnified Alternating Current in Battery Fast Chargers based on DC-DC Converters using Transformerless Resonant Filter Design
(English)In: IEEE Transactions on Transportation ElectrificationArticle in journal (Refereed) Submitted
Abstract [en]

For safety and longevity reasons, in subzero temperatures, lithium-ion batteries can only be charged after precommissioningtheir temperature. Therefore, in such conditions fast charging depends on fast heating. Recently,the injection of AC currents into lithium-ion batteries has been reported as a technique with potential to decreaseheating time. This paper proposes a method based on a multi-objective algorithm for DC-DC converter designusing transformerless resonant filters. The method enables the DC-DC converters to produce magnified AC currentin addition to the DC current. Using the proposed design method, a topological survey of DC-DC converters withmagnified AC current capability composed of either half- or full-bridge switch arrangements is carried out. Inthe presented experimental setup, it is demonstrated that by using an LCL circuit with specific component valuesand a full-bridge switch arrangement, magnifications of up to 15.7 may be reached. Further, by matching theswitching frequency with the frequency where the LCL and the battery resonate, for the same injected AC current,the current flowing in the semiconductors and the switching frequency could be reduced. This allowed a lossreduction in the semiconductors of up to 75%, when compared with an equivalent DC-DC converter enabled toproduce a non-magnified AC current.

Keywords
Batteries, DC-(DC/X·AC) converters, fast charging, fast heating, injection of alternating current.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-251663 (URN)
Funder
Swedish Energy Agency, 37434-1
Note

QC 20190520

Available from: 2019-05-17 Created: 2019-05-17 Last updated: 2019-06-14Bibliographically approved

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