AEMO reviews NEM power system requirements

2 min

The Australian Energy Market Operator (AEMO) published its annual reports on Network Support and Control Ancillary Services (NSCAS) and System Strength and Inertia. The reports identify emerging trends, challenges, and potential solutions to maintain critical power system requirements as the National Electricity Market (NEM) experiences rapid change.

Both reports highlight that maintaining power system security will become more challenging due in part to a greater share of renewable grid-scale generation and less synchronous generation availability. Further, world-leading levels of rooftop solar have seen minimum operational demand levels occurring in the daytime, rather than overnight, with falling minimum demand records impacting the NEM.

These trends, as highlighted in AEMO’s 2020 Integrated System Plan and 2020 Electricity Statement of Opportunities, pose significant implications for maintaining secure and reliable energy for consumers.

AEMO Acting Chief System Design and Engineering Officer, Nicola Falcon, said: “As increasing new amounts of rooftop and commercial solar is installed, minimum demand is expected to further decline, and together with increasing amounts of grid-scale wind and solar, these factors could lead to operational changes in synchronous generation in the market.

“This could include withdrawals of units in low demand periods, and lower overall synchronous unit commitments outside of peak demand periods,” she said.

The System Strength and Inertia Report observes strong indications that projected system strength may be insufficient in Queensland, New South Wales and Victoria in the near term if certain conditions eventuate. Similarly, projected inertia may be insufficient in Queensland.

AEMO has not declared these shortfalls, due to the remaining uncertainty about when and to what degree existing synchronous generating units may change their operations.

This report also updates the minimum system strength and inertia requirements across the NEM, declares the re-emergence of a system strength and inertia shortfall in Tasmania in 2024 once existing service agreements expire (as well as a risk of larger, earlier shortfalls), extends an existing inertia shortfall in South Australia to 2023, and notes that further analysis is required to confirm the scale of the Red Cliffs system strength shortfall in Victoria beyond 2022. 

Similar to the system strength and inertia report, while AEMO’s NSCAS review has not identified any gaps at this stage, there are signs that this could soon change as minimum demand continues to decline or if synchronous generation changes operation under a changing energy mix. Operational measures are being relied upon more frequently to help manage voltages during low demand conditions, including switching lines out of service to reduce voltages. 

“We expect that the power system will operate close to its limits in some areas and under some conditions. AEMO will monitor the situation closely, in particular in Queensland and Victoria, and if conditions change then AEMO will declare gaps as required before the next scheduled annual review,” Ms Falcon said.

“Delivery of voltage management and reactive power support from non-synchronous generators, such as wind and solar farms, will become critical, especially at times of minimum demand on the system,” she said.

The Energy Security Board and the Australian Energy Market Commission are progressing major regulatory reforms which will affect future provision of system strength and inertia (and in conjunction may also deliver new infrastructure which can support voltage needs). The reform programme includes the post-2025 NEM market design project, and consideration of seven National Electricity Rule change requests relating to the provision of system services.  

AEMO is currently preparing an Engineering Framework intended to help stakeholders stay informed of the changing technical needs of the power system. When planning for the provision of new system strength and inertia, AEMO and TNSPs must also account for other system needs, including thermal network capacity, stability of DER, and voltage requirements. There will be increasing opportunities for sourcing these services from non-energy providers, which may provide further efficiencies in the future power system design.

Click here to access an infographic that summarises the emerging trends and outcomes from the 2020 planning for system operability assessments.

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