New South Wales (NSW) and the Australian Capital Territory (ACT) are experiencing a major change in electricity demand patterns with growing rooftop solar uptake. This has resulted in record-low operational demand levels, posing potential risks to grid stability. In response, the Australian Energy Market Operator (AEMO) is working with governments, Network Service Providers (NSPs), and TransGrid to introduce an emergency backstop capability to respond to low-demand conditions. This article addresses the problems, possible backstop options, and short-term remedies to facilitate an electricity grid which is reliable as well as stable.

Comprehending Minimum Operation Demand

Minimum operating requirement is the lowest demand level at which the power system can continue to provide basic services. Synchronous generators like coal and gas units play a vital role in system stability as they contribute inertia to assist in frequency fluctuations management, voltage control to support grid stability, and system strength to allow network components to operate correctly.

In NSW/ACT, the grid needs at least 1.5-2 GW of active demand to maintain sufficient synchronous generators in operation. During outage situations, the requirement rises to around 2.6 GW, necessitating emergency arrangements to be in place.

Challenges in Managing Low Demand

Because of the explosive expansion of distributed photovoltaic (PV) systems, minimum demand has been falling by about 500 MW every year. According to projections, NSW/ACT may experience severe grid stability problems as soon as 2025, especially in periods of very low demand, like sunny weekends with intense solar radiation.

AEMO and NSPs do not yet have proper tools to manage distributed PV generation since NSW/ACT does not yet require active PV management capabilities. Grid operators would otherwise have to resort to reverse feeder shedding, disconnecting high-solar-penetration areas to ensure stability.

Current Backstop Capabilities

Currently, NSW/ACT does not have much to draw on to raise operational demand or lower surplus solar output. DNSPs currently estimate they can curtail embedded and non-scheduled generators to the tune of about 120 MW of response. They are also able to shift hot water loads, providing a further 72 MW of operational demand.

New South Wales/Australian Capital Territory: Minimum demand thresholds and projections

In addition to these interventions, however, the overall available backstop capacity is only approximately 192 MW, well short of the 400 MW needed by October 2025. The gap indicates that the need for more extensive backstop arrangements is pressing.

Proposed Solutions and Recommendations

To avoid emergency grid instability, AEMO and stakeholders have put forward key short-term actions.

One of the key measures is the enforcement of mandatory distributed PV management. This involves the introduction of a regulatory framework mandating active management features for all new PV installations, remote curtailment capabilities for new solar installations, and compliance frameworks for regular remote testing and enforcement.

Another vital strategy is the expansion of demand response programs. Industrial users can be incentivized to move energy consumption to low-demand hours, and dynamic electricity pricing can be utilized to encourage energy usage during times of high solar output.

Network and transmission infrastructure also need to be strengthened. DNSP operating procedures must be improved to effectively monitor and manage backstop capacity. TransGrid also has to improve its capacity to control voltage stability during low-demand conditions.

Investing in storage solutions for energy will be a key element in countering low demand problems. The installation of grid-scale batteries and pumped hydro needs to be ramped up to take up marginal solar production. The addition of Virtual Power Plants (VPPs) can give rapid-response grid balancing to stabilize the system further.