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Measurements and analysis of battery harmonic currents in a commercial hybrid vehicle
KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.ORCID-id: 0000-0002-9481-7366
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.ORCID-id: 0000-0002-0108-1872
KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.ORCID-id: 0000-0002-6283-7661
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.ORCID-id: 0000-0001-9203-9313
Vise andre og tillknytning
2017 (engelsk)Inngår i: 2017 IEEE Transportation and Electrification Conference and Expo, ITEC 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, s. 45-50Konferansepaper, Publicerat paper (Fagfellevurdert)
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.

sted, utgiver, år, opplag, sider
Institute of Electrical and Electronics Engineers Inc. , 2017. s. 45-50
Emneord [en]
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
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-216277DOI: 10.1109/ITEC.2017.7993245ISI: 000427121300009Scopus ID: 2-s2.0-85028594346ISBN: 9781509039043 OAI: oai:DiVA.org:kth-216277DiVA, id: diva2:1165685
Konferanse
2017 IEEE Transportation and Electrification Conference and Expo, ITEC 2017, 22 June 2017 through 24 June 2017
Merknad

QC 20171213

Tilgjengelig fra: 2017-12-13 Laget: 2017-12-13 Sist oppdatert: 2019-05-17bibliografisk kontrollert
Inngår i avhandling
1. Interactions between battery and power electronics in an electric vehicle drivetrain
Åpne denne publikasjonen i ny fane eller vindu >>Interactions between battery and power electronics in an electric vehicle drivetrain
2018 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The electric machine and power electronics in electric and hybrid electric vehicles inevitably cause AC harmonics on the vehicle's DC-link. These harmonics can be partially filtered out by large capacitors, which today are overdimensioned in order to protect the vehicle's battery pack. This is done as a precaution, since it is not known whether ripple-current has any harmful effect on Li-ion  cells.

We have measured and analyzed the ripple-current present in a hybrid electric bus, and found that a majority of the power was carried by frequencies in the range 100~Hz to 1~kHz. The single most energetic harmonic in this particular vehicle is believed to have been caused  by a misaligned resolver in the motor.

We have also designed and built an advanced experimental set-up in order to study the effect of ripple-current on Li-ion cells in the lab. The set-up can cycle up to 16 cells simultaneously, with currents of up to 50~A including a superimposed AC signal with a frequency of up to 2~kHz. The cells' temperatures are controlled by means of a climate chamber. The set-up also includes a sophisticated safety system which automatically acts to prevent dangerous situations before they arise.

Using this set-up we tested whether superimposing AC with a specific frequency improves the charging performance of Li-ion cells. Statistical analysis found no improvement over regular DC cycling, and a physics-based model explains the experimental findings.

We have also investigated whether ripple-current accelerates the aging of Li-ion cells. Twelve cells were either calendar or cycle  aged for one year, with some cells being exposed to superimposed AC with a frequency of 1~Hz, 100~Hz, or 1~kHz. No effect was observed on any of capacity fade, power fade, or aging mechanism.

Finally we also tested whether it is possible to heat Li-ion cells from low temperatures using only AC. We propose a method for AC heating of Li-ion cells, and open the discussion for generalizing the technique to larger battery packs.

In conclusion, ripple-current has negligible effect on Li-ion cells, except for heating them slightly.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2018. s. 74
Serie
TRITA-CBH-FOU ; 2018:27
HSV kategori
Forskningsprogram
Kemiteknik; Elektro- och systemteknik
Identifikatorer
urn:nbn:se:kth:diva-228030 (URN)978-91-7729-837-3 (ISBN)
Disputas
2018-06-15, E2, E-huset, huvudbyggnaden, våningsplan 3, Lindstedtsvägen 3, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Forskningsfinansiär
Swedish Energy Agency
Merknad

QC 20180518

Tilgjengelig fra: 2018-05-18 Laget: 2018-05-17 Sist oppdatert: 2018-05-18bibliografisk kontrollert
2. Modeling and Analysis of the Interaction of Batteries and Power Electronic Converters
Åpne denne publikasjonen i ny fane eller vindu >>Modeling and Analysis of the Interaction of Batteries and Power Electronic Converters
2019 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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. 

sted, utgiver, år, opplag, sider
Stockholm, Sweden: KTH Royal Institute of Technology, 2019. s. 184
Serie
TRITA-EECS-AVL ; 2019:45
Emneord
Alternating current, aging, electric vehicles, harmonics, lithium-ion batteries, power converter, resonant filters, ripple, temperature control.
HSV kategori
Forskningsprogram
Elektro- och systemteknik
Identifikatorer
urn:nbn:se:kth:diva-251665 (URN)978-91-7873-187-9 (ISBN)
Disputas
2019-06-05, Kollegiesalen, Brinellvägen 8, Kungliga Tekniska högskolan, Stockholm, 14:00 (engelsk)
Opponent
Veileder
Merknad

QC 20190517

Tilgjengelig fra: 2019-05-17 Laget: 2019-05-17 Sist oppdatert: 2019-05-20bibliografisk kontrollert

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