pwr_january-2025 - 24

TRANSFORMERS
The Solid-State Shift:
Reinventing the Transformer
for Modern Grids
Transformers have been the backbone of power grids for over a century, but today's
demands for renewable energy, electric vehicles, and smarter grids are exposing their
limits. Enter solid-state transformers-compact, efficient, and intelligent power
solutions poised to revolutionize how electricity is distributed and managed.
Sonal Patel
T
he push to modernize the grid is
exposing critical shortcomings of a
century-old workhorse-the transformer.
Stemming from Michael Faraday's
groundbreaking discovery of electromagnetic
induction in 1831, the first
transformer systems built circa 1885 revolutionized
electricity transfer, essentially
by enabling the step-up of voltage for
efficient long-distance transmission and
subsequent step-down for safe local use.
However, despite innovations over the
years, conventional transformers remain
ill-suited to meet the dynamic demands
of modern grids. Although their fundamental
design provides a cost-effective
and reliable method to convert voltage
and current levels, they are optimized
for centralized, unidirectional power systems
with simple structures. At the core
of their limitations, as David Pascualy,
a technical expert in solid-state transformers
(SSTs) and power electronics,
explained to POWER, " a normal transformer
doesn't communicate with the
grid. " Without advanced power electronics
or sensors, conventional transformers
cannot actively regulate voltage, mitigate
harmonic distortion, or respond dynamically
to grid disturbances. Furthermore,
their lack of integration with digital control
systems and grid communication protocols
prevents them from supporting intelligent
grid operations, such as predictive
maintenance or real-time optimization.
Traditional transformers operate at
low frequencies (50/60 Hz), necessitating
bulky cores and windings that limit
scalability, reduce efficiency, and make
them impractical for space-constrained
applications such as urban substations or
offshore wind platforms, Pascualy noted.
Additionally, their reliance on oil-based
insulation and cooling introduces environmental
risks, demands significant
24
maintenance, and leaves them vulnerable
to failures under extreme weather
conditions or fluctuating loads.
To address these limitations, research
into SSTs has been ongoing since the
1960s. William McMurray, an engineer
at General Electric, first proposed the
concept of an " electronic transformer " in
1968 in a design that introduced high-frequency
alternating-current-to-alternatingcurrent
(AC/AC) converters. The design
allowed for voltage transformation using
power electronic components, marking a
foray away from traditional low-frequency
transformers and demonstrating how
high-frequency operation could enable
more compact and efficient designs. The
concept was later refined by contributions
such as J.L. Brooks' SST in 1980
and the Electric Power Research Institute's
(EPRI's) introduction of the Intelligent
Universal Transformer (IUT) in 1995.
The IUT incorporated features such as
bidirectional power flow, voltage regulation,
and seamless AC/DC conversion.
Pilot Projects and Promising
Applications
As Pascualy pointed out, interest in SSTs
has been growing as the urgency to outfit
grids with more capable, intelligent,
and dynamic solutions mounts. But while
SSTs are promising, they largely remain
in the research and development (R&D)
phase. SST technology development is
" really early on, " he noted. " Some of the
big powerhouses are developing SSTs
for certain aspects of their design. "
So far, pilot projects and commercial
offerings highlight SST potential in electric
vehicle (EV) charging and renewable
energy. Amperesand will trial its silicon
carbide (SiC)-based SSTs at Singapore's
port in 2025 for bidirectional EV charging.
Delta in 2022 demonstrated a 96.5% efficiency
for its SST fast chargers using
www.powermag.com
SiC MOSFET-based SST
technology.
Meanwhile, Alder Buck and EPRI are advancing
SST prototypes for multistage
applications and exploring replacements
for 25-kVA distribution transformers with
enhanced voltage regulation.
Most R&D for SSTs appears largely
centered on medium-voltage to lowvoltage
transformations, typically from a
range of 13.2 kV to 15 kV down to lower
voltages for various end-use applications
(Figure 2), Pascualy noted. The near-term
focus is " going to really be at the distribution
level, " even though SST harbors a
potential expansion into higher-voltage
transmission, he suggested. Data centers
represent another key sector looking
intently at SSTs, given their potential
to serve as a more efficient and integrated
interface between an AC grid and a
DC-powered data center, he said.
Several Barriers to Overcome
While progress is encouraging, several
barriers must be overcome before the
technology can achieve mainstream
adoption in the power industry, said Pascualy.
A key challenge is cost. SSTs are
significantly more expensive than conventional
transformers owing to their
advanced materials, complex designs,
and reliance on semiconductor-based
power electronics. As with all novel
power technology, achieving economies
of scale and driving down manufacturing
costs will be essential for making SSTs a
viable option for utilities and grid operators.
Reliability and field performance are
also critical factors, and SSTs, with their
multistage designs and advanced control
capabilities, will need to undergo extensive
testing and validation to ensure they
can withstand the rigors of real-world
grid operations. " You can't possibly figure
out everything that's going to happen
in the field. And you have different use
POWER | January 2025
http://www.powermag.com
pwr_january-2025

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