IEEE Power & Energy Magazine - March/April 2021 - 84

ing to system security. In this respect, while the challenges
of resource adequacy and reliability often relate to critical
periods over a year and are a matter of planning, keeping
a system operationally secure is an everyday (and even an
every-second) challenge that requires careful consideration
within a market environment.
As previously discussed, new forms of technical risk
are being introduced from intermittent and inverter-based
sources of supply and demand. From a market perspective,
scarcities are emerging in system services that were previously delivered as a by-product of energy, such as inertia
and system strength provided by synchronous generators
that would be online to produce energy (and make money in
energy markets) and would also provide these other services
(and in many cases without being specifically remunerated).
Finally, increasing interactions among different power system parameters with the potential for cascading and correEconomy, Market, and Regulatory
lated system events (what we previously called " system fraChallenges and Opportunities
Following the previous technical discussions and consider- gility " ) are being observed.
The economic implications of a failure to manage system
ing all of the potential solutions to the emerging challenges
that have been proposed, the questions now arise of what is security are serious. Scarcities of system services may force
the best way to incentivize the development of the most suit- market operators to increasingly intervene in the market.
able solution within a market environment, what the role of This may also lead to more curtailment of renewable plants,
regulation and energy policy is, and what the best approach delays to connection, and stagnating investment. This has all
been witnessed in Australia.
would be.
On a starker level, inadequate service provision could
lead
to system outages and major economic loss, especially
The Economics of System Security: From the
in
the
context of a more fragile grid that is less resilient to
Bottom Up
high-impact,
low-probability events, as illustrated previFrom the considerations made in the previous sections, it is
clear that the transition of our electricity system to a low-car- ously in the case of the 25 August 2018 separation event. A
bon future with large shares of variable and partly uncertain key challenge for policy makers and market designers is to
renewable energy and with pervasive IBRs is profoundly develop cohesive economic and regulatory frameworks for
changing (or has already changed) the nature of risks relat- operational security that efficiently procure the services necessary to secure the system to an
appropriate level of risk and that
effectively manage the integration
Hornsdale Battery Plant-25 August 2018
80
50.6
within the broader market design
for electric supply.
60
50.4
In this respect, cross-market co40
50.2
optimization, for energy, operating
reserves, inertia, largest contin20
50
gency, and so on, has been shown
0
49.8
to be technically achievable. In
fact, it is already being pursued in
-20
49.6
Western Australia. However, inte-40
49.4
gration among other different ser-60
vices is lacking. For example, sys49.2
Battery (MW)
Frequency (Hz)
tem strength, which is also linked
-80
49
to inertia, is managed as a local
service, in contrast with the more
regional or system level nature of
the others. Furthermore, the right
Time (hh:mm:ss)
economic signals should be incorporated to support adequate investfigure 5. The Hornsdale battery plant's active power response versus frequency in
ment over the long term, but this is
South Australia during the 25 August 2018 separation event (Source: AEMO).
84

ieee power & energy magazine

13:12:30

13:12:20

13:12:10

13:11:60

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Frequency (Hz)

Active Power (MW)

its ability to switch the active power direction following the
frequency's inversion.
However, such responses might create issues in an
interconnected system, for example, because too fast of an
increase in interconnector flows might activate protection
relays and trip the interconnector. In the specific case of the
separation event, it is not clear whether the fast response from
the battery did contribute to the trip of Heywood. However,
authors' simulations that were analyzed to emulate the event
and study potentially similar cascaded outages suggest this
is a material possibility. Therefore, moving forward, it will
be particularly important to carefully plan the location of
fast frequency-response resources, considering interconnector transfer limits and coordinating their potential response
with interconnectors' protection settings.

march/april 2021
IEEE Power & Energy Magazine - March/April 2021

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