IEEE Electrification - September 2022 - 5

operator. Meanwhile, the PPA structure
also incentivizes the grid operator
to make the best possible use
of resources.
The first feature article, " Operational
Security in 100% InverterBased
Power Systems: Experiences
from Hawai'i, " was contributed by
Ulrich Muenz, Nan Xue, Xiaofan Wu,
Amer Mesanovic, Leland Cockcroft,
Lisa Dangelmaier, Chris Heyde, Zerui
Dong, Sudipta Chakraborty, and Aditya
Ashok. It begins with a description of
challenges from the perspective of
Hawaiian Electric related to variable
generation that requires both shortand
long-term energy storage, new
energy market concepts, and fast grid
operation functions to address rapidly
changing power flows. Another
challenge is related to stability, N-1
security, and protection in a grid with
high levels of inverter-based resources
(IBRs). The authors introduce a
new generation and control architecture
allowing the optimization of
dynamic power system stability and
security against N-1 contingencies
and provide a description of this new
design, which was developed under a
U.S. Department of Energy-funded
Renew100 project for the island of
Hawaii. The components of the architecture
and results of its evaluation
are described.
" A New Hybridization Approach for
Increasing the Share of Renewables
in El Hierro " is by Felix Boda, Cristina
Morales, David Cañadillas, Alberto
Barrado, and Ricardo GuerreroLemus.
The Canary Island of El Hierro
(part of Spain) has been a frontrunner
in regional sustainable energy
policy. Due to a lack of exploitable
endogenous energy resources, El
Hierro was completely dependent on
external fuel supplies until the
deployment of the Wind-Pumped
Hydro Power Station, in 2014. Until
then, electricity was generated
exclusively by the use of fossil fuels
(diesel), with the associated economic
and environmental costs. The
authors describe the hydro-wind
power plant of Gorona del Viento,
which achieved a substantial milestone
in the decarbonization of the
El Hierro power system. But this is
only the first step in the plan to
reach full decarbonization. Photovoltaic
generation and batteries are
considered to increase the penetration
of renewables in the system and
augment stability.
The third feature, " Stabilizing
Inverter-Based Transmission Systems, "
is by Andy Hoke, Przemyslaw
Koralewicz, Rick Wallace Kenyon,
Bin Wang, Li Yu, Kelcie Kawamura,
and Jin Tan. In it, the authors present
the first experimental verification
of the ability of grid-forming
inverters to stabilize a transmission
electric power system that is otherwise
unstable. Megawatt-scale
power hardware-in-the-loop experiments
demonstrate the ability of a
real hardware grid-forming inverter
to stabilize several otherwise unstable
scenarios of a 145-MW power
system, robust to both the loss of
the largest generator and a severe
five-cycle fault at a low-short-circuit-ratio
bus. The trend found in
these experiments indicates an
increased need for grid-forming
inverter capacity to maintain system
oscillatory stability as the online
capacity of synchronous machines
drops. It was demonstrated that
with zero synchronous machines,
the system was stable in steady
state with 30 MVA of GFM inverters
but needed 60 MVA of GFM to withstand
a fault. The results of this
work would vary somewhat for
other systems and varieties of gridforming
control, but it expected that
these general trends will hold across
other transmission systems.
In " Puerto Rico Distributed Solar
Integration Study, " Derek Stenclik
and Matthew Richwine describe a
detailed technoeconomic analysis
that was conducted to illustrate a
future Puerto Rico grid integrated
with high levels of distributed energy
resources, prioritizing rooftop solar
IEEE Electrification Magazine / SEPTEMBER 2022
5
and storage. A unique aspect of the
potential future system is its reliance
on many distribution-connected
GFM inverters for power system stability
(as opposed applying gridforming
controls
on larger
transmission-connected plants, as is
more typical in emerging applications).
The aftermath of Hurricane
Maria led Puerto Rico's energy sector
to consider several new plans to
rebuild the island's infrastructure
and make investments to strengthen
the power grid. To evaluate the
changes to Puerto Rico power system
operations and grid stability with
increasing distributed energy
resources, the analysis was based on
detailed power system simulation
and modeling, including both production
cost modeling and dynamic
stability simulations.
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