IEEE Power Electronics Magazine - December 2022 - 69

FIG 1 The goal of UNIFI is to develop a universal set of guidelines that enable seamless
integration of IBRs. Source: U.S. DOE.
suggesting that commercial availability
of this emerging technology is on
the horizon. On Tuesday 11 October,
special session 5, organized by Victor
Veliadis of PowerAmerica, North Carolina
State University (NCSU), USA
and Thomas M. Jahns of University of
Wisconsin-Madison, USA, demonstrated
new developments in WBG
bidirectional switches and applications.
In this session, five panelists
from academia and industry disclosed
new monolithic bidirectional (M-BD)
switches using silicon carbide (SiC)
and gallium nitride (GaN) technologies.
The speakers were Subhashsish
Bhattacharya of NCSU, Johann Kolar
of ETH Zurich, Switzerland, Bulent
Sarlioglu of University of Wisconsin-
Madison, Michael Harris of Atom
Power, and Xiaoqing Song of ABB U.S.
Corporate Research Center. Both lateral
and vertical M-BD device topologies
were proposed using GaN and
SiC devices with ratings as high as
1400 V and 100 A. While evaluating
both strengths and technical challenges,
this session also explored
some application areas for these
devices, extending from ac solid-state
circuit breakers to static power converters
and motor drives.
Bhattacharya presented a SiC
FIG 2 The Ultium battery module is made up of long pouch cells that can be
stacked to meet the unique needs of every driver, all while improving efficiency,
power, and range.
because they come in large-format, pouch-style cells that
can be stacked vertically or horizontally inside the battery
pack (Figure 2). Consequently, added Grewe, engineers
can optimize battery energy storage and layout for
each vehicle design. Ultium energy options range from 50
to 200 kWh, which could enable a GM-estimated range of
up to 400 miles (643 km) or more on a full charge with
0-60 mph acceleration as low as 3 seconds. Ultium cells
are now being manufactured by a joint venture with LG
Chem, and hope to drive battery cell costs below $100/
kWh. The cells use a proprietary low cobalt chemistry. GM
will back the technology with a comprehensive charging
infrastructure and customer service, stated the keynoter.
Bidirectional WBG Switches
Wide bandgap (WBG) based bidirectional switches were
the focus of several special and technical sessions,
based four quadrant monolithic bidirectional
FET (BiDFET) (Figure
3) with static and dynamic characterization
for a 1.2 kV/20 A BiDFET
that offered lower conduction voltage
drop and higher switching frequency
for current source inverter
(CSI) and direct ac-ac matrix or cyclo converter based
power conversion systems. In addition, applying SiC
based monolithic BiDFET switches, the researcher also
demonstrated a 3-phase grid-connected power conversion
system for EV charging application (Figure 4) and
a grid-connected power conversion system for PV application.
The keynote speaker indicated that the proposed
single-stage architecture for isolated, bidirectional dc-
ac conversion enabled by the four-quadrant monolithic
BiDFET switches offered several advantages over the
conventional architecture. They include simpler,
switch count topology, elimination of nonreliable, low-life
electrolytic capacitors, potentially superior EMI performance,
soft-switched operation enabling high-efficiency,
and higher power-density.
Furthermore, using 1200 V, 50 A BiDFET based halfbridge
modules, Bhattacharya realized a 50 kW ac-dc
December 2022 z IEEE POWER ELECTRONICS MAGAZINE 69
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