The GOOGLE Little Box Challenge – Ultra-Compact GaN-Based Single-Phase DC/AC Power Conversion
dc.contributor.author
Neumayr, Dominik
dc.contributor.supervisor
Kolar, Johann W.
dc.contributor.supervisor
Nee, Hans-Peter
dc.date.accessioned
2020-07-24T16:13:05Z
dc.date.available
2020-07-24T14:07:12Z
dc.date.available
2020-07-24T16:13:05Z
dc.date.issued
2019
dc.identifier.uri
http://hdl.handle.net/20.500.11850/428425
dc.identifier.doi
10.3929/ethz-b-000428425
dc.description.abstract
With the ambition of achieving a cost reduction in solar power and microgrid
technology, an increased efficiency of Uninterruptible Power
Supplies (UPS) or the ability to use an electric vehicle’s battery as backup
power during a power outage, Google and IEEE initiated the Google Little
Box Challenge (GLBC) back in July 2014 to build the worldwide smallest
2 kW / 450 V DC / 240 V AC single-phase PV inverter with η > 95 % CEC
weighted efficiency and an air-cooled case temperature of less than 60 °C
by using latest power semiconductor technology and innovative converter
concepts, advertising $1 million prize money. The challenging specifications
and the attractive prize money created a remarkable interest in the power
electronics community, which led to the participation of 2000+ teams – companies,
research institutes and universities – in the GLBC. Finally, 100+ teams
submitted technical descriptions of realized systems. Out of these applications,
18 finalists including ETH Zurich were invited to submit their hardware
prototypes for final testing.
This dissertation reports all major findings and key lessons learned from
the participation of the Power Electronic Systems Laboratory (PES) of ETH
Zurich in the GLBC and during the research conducted afterwards to investigate
encountered problems which could not be analyzed in detail because of
the tight schedule of the competition. The power-density benchmark established
by the realized inverter prototypes and considering the achievements of
other GLBC finalists, indicates that a 20 times higher power-density compared
to the current state-of-the-art in industry is principally possible. All necessary
aspects to realize an extreme power-density converter in accordance with the
GLBC specifications are discussed. First, a review of suitable converter topologies
and advanced control concepts and component technologies to achieve a
high power-density, adopted by the GLBC finalists and/or described in the
scientific literature, is provided. Different bridge-leg control techniques (e.g.
constant frequency PWM vs. Triangular Current Mode (TCM)), the selection
of WBG power transistors, the implementation of compact High Frequency
(HF) inductors and the selection of suitable capacitors, are discussed among
other relevant topics.
Guided by the insights from a preceding multi-objective design optimization
(virtual prototyping), two hardware implementations of the Little Box
inverter concepts developed at ETH Zurich are presented and accompanied
with experimental results to support the claimed performances with respect
to efficiency, η, and power-density, ρ. The initial prototype implementation,
a GaN based full-bridge inverter with TCM control and variable switching
frequency up to the MHz range, was ranked among the top ten contributions
of the GLBC finalists. The continued research following the conclusion of
the GLBC in October 2015, resulted in an improved understanding of key
technologies and allowed to further improve component models for more
accurate Pareto optimization results. Novel experimental methods to accurately
determine the soft-switching losses in GaN and SiC semiconductors,
to characterize the behavior of ceramic capacitors subject to a large-signal
excitation at low-frequencies and to analyze unexpectedly high core losses in
multi-airgap MnZn ferrite inductors, developed for the first version of the
Little Box inverter, are reported. By means of the gained insights and the
consideration of an alternative inverter concept, i.e. a DC/|AC|-buck converter
operated with constant 140 kHz PWM and a subsequent low-frequency
unfolding inverter, an improved version of the Little Box inverter, almost
twice as compact as the initial version, is realized.
Because of the fluctuating power with twice the mains-frequency intrinsic
to single-phase AC systems, active power buffer concepts with additional
auxiliary converters are employed in the developed Little Box inverter systems
in order to substitute bulky electrolytic capacitors and shrink the volume of
the necessary energy storage element to compensate the fluctuating power.
In particular, two promising concepts, a full-power processing buck-type and
a partial-power processing Series Voltage Compensator (SVC)-type power
buffer, are comparatively evaluated. The investigated partial-power auxiliary
converter approach is subsequently also applied to a 380 V DC / 48 V DC
series-resonant LLC converter, where a novel control concept achieves tight
output voltage regulation for changing input voltage without varying the
switching frequency or duty-cycle of the main DC/DC converter. Since the
auxiliary converter only processes a small share of the rated power, only a
marginal ηρ-impairment of the overall converter must be accepted compared
to a system with constant voltage transfer ratio.
In conclusion, the main research findings and lessons learned over the
course of the dissertation are summarized and an outlook on expected future
power-density improvements is provided including a discussion of necessary
advances of the involved component technologies. Finally, further insights on
the origin of the observed excess cores losses in multi-airgap inductors and a
comprehensive comparison of two promising ceramic capacitor technologies
to implement ultra-compact power pulsation buffers are provided in the
Appendices.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.rights.uri
http://rightsstatements.org/page/InC-NC/1.0/
dc.subject
Google Little Box Challenge
en_US
dc.subject
GaN
en_US
dc.subject
DC/AC Power Conversion
en_US
dc.subject
Miniaturization
en_US
dc.subject
Ultra-Compact Power Electronics
en_US
dc.title
The GOOGLE Little Box Challenge – Ultra-Compact GaN-Based Single-Phase DC/AC Power Conversion
en_US
dc.type
Doctoral Thesis
dc.rights.license
In Copyright - Non-Commercial Use Permitted
dc.date.published
2020-07-24
ethz.size
301 p.
en_US
ethz.code.ddc
DDC - DDC::6 - Technology, medicine and applied sciences::621.3 - Electric engineering
en_US
ethz.identifier.diss
26373
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02140 - Dep. Inf.technologie und Elektrotechnik / Dep. of Inform.Technol. Electrical Eng.
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02140 - Dep. Inf.technologie und Elektrotechnik / Dep. of Inform.Technol. Electrical Eng.::03573 - Kolar, Johann W. (emeritus) / Kolar, Johann W. (emeritus)
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02140 - Dep. Inf.technologie und Elektrotechnik / Dep. of Inform.Technol. Electrical Eng.::03573 - Kolar, Johann W. (emeritus) / Kolar, Johann W. (emeritus)
en_US
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20.500.11850/225523
ethz.relation.hasPart
20.500.11850/187166
ethz.relation.hasPart
20.500.11850/187211
ethz.date.deposited
2020-07-24T14:07:21Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2020-07-24T16:13:36Z
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2023-02-06T20:14:30Z
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