IEEE Power & Energy Magazine - November/December 2020 - 34

to draw from, the knowledge that has been gleaned to date
indicates that VPPs can respond effectively to power system events and price signals. This includes responding to
frequency excursions beyond the normal operating range
(49.85-50.15 Hz) and precharging (or discharging) to cater
to future high-price (or low-price) events, respectively. Two
VPP responses to contingency FCASs and energy events in
South Australia are analyzed in the following.

contingency events. A recent example of such a contingency
event occurred when the interconnector between Victoria
and South Australia separated on 31 January 2020.
VPP Demonstrations

Given the potential scale of DER installations during the
next decade, AEMO has established a dedicated program to
integrate the resources into the power system safely, securely,
and in a way that maximizes their benefits for all consumers, not just those who own them. For example, appropriate
frameworks can incentivize DERs to deliver value for all
electricity consumers by providing grid services that make
the power system more efficient.
In 2019, AEMO launched VPP demonstrations to explore
the capability of aggregated DERs to deliver FCASs and
develop the organization's understanding of how VPPs
respond to energy market price signals. A VPP broadly refers
to an aggregation of resources (such as decentralized generation, storage, and controllable loads) that are coordinated to
deliver services for power system operation and electricity
markets. As of January 2020, there are two participants in
the program, and two further VPPs are going through the
enrollment process. Although there is a small pool of data

Zone 3

Zone 2

D-PV Response
to Disturbance

400
200

Zone 3
(942 km)

.
5:

m
p.

00
4:

.
1:

m
11

a.
0

.
m
a.
10

Upscaled
Generation (MW)

9-15 January 2020 Response to
Energy Spot Prices
Observing VPPs' actions during the course of a week provides evidence that VPPs do respond to energy market signals.
This is clear in Figure 19, where precharging in anticipation

Zone 1

600

Change (%)
t0-tnadir

10 December 2019 Response to
Underfrequency Event
On 10 December 2019, NEM experienced both high (>50.15 Hz)
and low (<49.85 Hz) frequency events within 45 min of each
other. The South Australia VPP responded immediately, in
both cases, to first charge its batteries to lower the system
frequency and then discharge the batteries to raise the system frequency, shown in Figure 18.

Generation Reduction
Proportion Disconnected

Zone 2
(182 km)

20
0

Zone 1

Zone 2

Zone 3
Zone 1
(34 km)
Torrens Island Gas
Generator
0

700
(km)

figure 17. A South Australian voltage disturbance event map and D-PV response profile for 3 March 2017 (upscaled
generation indicates the estimated performance across the South Australian D-PV fleet, based on operational data). For
further details, please refer to Stringer et al. in the "For Further Reading" section.
34

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