IEEE Power & Energy Magazine - September/October 2021 - 84

manifesting in voltage rises on the distribution network.
These rises present serious issues for network management
when the physical thermal limits of network infrastructure
are reached. The severity and rate of voltage rises have
increased concurrently with the rapidly growing installation
of rooftop solar PVs.
Under existing network connection arrangements, Western
Power sets a default limit for residential customers that
confines the export capacity of solar PV systems to 5 kW
(Western Australia has a mix of single-phase and three-phase
connections for residential properties). The limited communications
capabilities of existing inverters (to send information
and receive signals remotely) restrict the management of customer
DERs in response to network conditions. Consequently,
as installed DER generation capacity increases, Western
Power would be required to undertake significant network
augmentation or limit rooftop solar installation applications.
Customers, too, are impacted by power quality fluctuations
resulting from two-way power flows on the distribution
network. These fluctuations can trip the self-protection settings
of inverters, decreasing output and limiting the financial
benefits expected by customers.
Further, system security is put at risk by the inconsistent
performance of inverters during system disturbances that
can exacerbate fluctuations. These issues are all worsened
by a large legacy fleet, size, and location of which the network
and system operators have extremely limited visibility.
The degree of compliance of these inverters with the existing
mandatory settings is largely unknown, and their performance
during events is unpredictable.
Last, the pressing concerns of low daytime demand and
high evening peak may be addressed in part through increased
battery storage. However, uptake in SWIS at the behind-themeter,
distribution, and transmission levels is currently low.
To address these issues, the roadmap recommends a
range of technology-related actions to improve DER performance,
the visibility and capability of the network and
system operators, and the use of storage.
Inverter Standards
Inverter performance is central to managing the impacts of
DERs, and in the near term, improvements to inverter standards
are essential to managing power quality on the distribution
network. The electrical standard applicable in SWIS
is Australian Standard 4777.2:2015-Grid Connection of
Energy Systems via Inverter Requirements (AS/NZS4777).
In 2019, Western Power made volt-var
response settings
a mandatory requirement of connection in its Network
Integration Guidelines, which set out guidance for the
installation of DER generation. These settings now require
devices to act as a reactive power sink for grid voltages
above 235 V (and a var source at voltages below 220 V).
However, the DER Roadmap identified the need for further
improvements to inverter performance in SWIS and
recommended these be progressed through an uplift to AS/
NZS4777, which came into effect in 2020. This change
results in inverters automatically reducing output as voltage
rises rather than tripping off at high voltages, reducing the
risk of large numbers tripping off on mild days with lowload
and high-solar generation.
Included in these improvements are enhanced autonomous
inverter functions, including a frequency response triggered
outside of a narrower band (with a threshold of 50.025 Hz now
compared to the existing 50.25 Hz). This will more closely
Technology
Integration
Inverter
Standards
Distribution
Battery Storage
Grid Response
Power System
Operations
Distribution
Network Visibility
Planning for
EV Integration
figure 4. DER Roadmap themes.
84
ieee power & energy magazine
september/october 2021
Tariffs and
DER
Investment Signals
Tariff Pilots
DERs for Tenants
Participation
Network
Investment Process
DER Orchestration
Pilot
DSO/DMO
Function Set
New Business
Models
Customer
Engagement
Customer Protection
and Engagement
Data
IEEE Power & Energy Magazine - September/October 2021

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