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Interactions betwee...
Interactions between battery and power electronics in an electric vehicle drivetrain
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- Bessman, Alexander (författare)
- KTH,Tillämpad elektrokemi
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- Lindbergh, Göran, 1959- (preses)
- KTH,Kemiteknik
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- Svens, Pontus, 1970- (preses)
- KTH
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- Wallmark, Oskar, 1976- (preses)
- KTH,Farkost och flyg
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- Thiringer, Torbjörn, Professor (opponent)
- Chalmers, Elektroteknik
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(creator_code:org_t)
- ISBN 9789177298373
- Stockholm : KTH Royal Institute of Technology, 2018
- Engelska 74 s.
- Relaterad länk:
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https://kth.diva-por... (primary) (Raw object)
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https://urn.kb.se/re...
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Abstract
Ämnesord
Stäng
- 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.
Ämnesord
- TEKNIK OCH TEKNOLOGIER -- Kemiteknik -- Annan kemiteknik (hsv//swe)
- ENGINEERING AND TECHNOLOGY -- Chemical Engineering -- Other Chemical Engineering (hsv//eng)
Nyckelord
- Chemical Engineering
- Kemiteknik
- Electrical Engineering
- Elektro- och systemteknik
Publikations- och innehållstyp
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