IEEE Electrification - September 2022 - 34

and phase angle of their output voltage
sinusoids to change on longer
timescales (a few ac line cycles) in a
way that synchronizes their output
with the rest of the power system.
This should allow them to self-synchronize
without fast supervisory
control, similar to how rotating synchronous
machines do, but through
power electronic controls rather than
through electromechanical physics.
Thus, in theory, a power system can be operated with only
IBRs if enough of them are GFM.
This theory has been proven true on some small, isoIn
theory, a power
system can be
operated with only
IBRs if enough of
them are GFM.
bandwidths in the hundreds of hertz,
such computer simulations need to use
EMT software that simulates the voltage
waveforms and relevant inverter controls
in full detail. Particularly relevant to
this article is a recent EMT study in
power systems computer aided design
(PSCAD) software of near-future Maui
island power system operating scenarios
with various levels of IBRs, synchronous
generators, and synchronous
condensers (see, for example, https://www.nrel.gov/docs/
fy21osti/79852.pdf).
A simplified model of the Maui transmission system
lated power systems (<10 MW) that have been operated
with 100% inverter-based generation; typically, that generation
is all located electrically close together, which reduces
the synchronization and stability challenge. However, to
date, no known power system large enough to include a
transmission system has operated stably with 100%
instantaneous IBRs.
Various authors have shown, via computer simulation,
that a stable operation at and near 100% inverter-based
generation should be possible. Because the inverter controls
responsible for the short-term voltage stability have
is shown in Figure 1; it consists of a mesh-networked
69-kV transmission system and multiple generators
throughout the island serving a typical load of 140-180 MW.
The EMT study indicated that, with all IBRs using conventional
GFL control, the Maui system is stable when
sufficient synchronous condensers are online but be -
comes unstable as condensers are removed. That itself is
an interesting research finding that the authors have
highlighted in other publications: a transmission system
powered by 100% IBRs could be operated stably using two
mature and proven technologies: conventional GFL
Reduced 2023 Maui Transmission Map
Central
111
~
West
405
~
404
~
403
~
~
~
601
~
~ ~~
~ ~ ~ ~
503
Maalaea
~
~
~
~
~
~
305
304
501
301
302
303
South
401
402
~
203
~ ~
Maalaea West
602
~ ~
~
~
~
502
201
~
112
~ ~
~
108
~
103
~
107
106
~
~
105
104
~
~
~
204
202
211
101
115
~
~
205
206
~
109
110
~
102
114
~
~
~
~
210
113
208
East
207
209
~
~
~
Synchronous Generator
Synchronous Condenser
Synchronous Hydro
Load
~
~
Inverter, Large PV, Battery, or Hybrid Plant
Wind, Type 3 or 4
Transformer
Inverter, Distributed Generation
Figure 1. The Maui transmission network as partitioned into regions.
34
IEEE Electrification Magazine / SEPTEMBER 2022
* Information was aggregated from
the full 230-bus system for illustrative
purposes and security reasons.
* The colored regions/hundredth bus
numbers are indicative of the PSCAD
parallelization basis.
https://www.nrel.gov/docs/fy21osti/79852.pdf https://www.nrel.gov/docs/fy21osti/79852.pdf
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