The Australian energy market operator has given itself more room to act on the sensitive issue of solar rooftop shutdowns, after reviewing the only time it had to publicize the move since it became part of its toolkit just over a year ago.
The South Australian grid has a world-leading share of rooftop solar energy. Last week, it reached an unprecedented level of 92.6 percent of domestic demand, which helped send the local network to a negative operational order For the first time – another world for the first time for a gigawatt-scale network.
This level of surface PV remains a challenge, but as long as the connection to the Victorian grid is working, the market operator has the tools to keep the grid secure. But when AEMO fears that there is a trustworthy risk of losing contact, they want to have the option of enforcing the shutdown rule.
That’s what it did on March 14 of this year, when one of the major transmission lines was out of service for scheduled maintenance, creating a real risk of isolating the state from the rest of the grid, making high levels of rooftop solar more difficult to manage.
AEMO was not expecting operational demand to fall below 400 MW, but it turned out that there was more rooftop solar production than expected – as a result of lower cloud cover that he had predicted – and less industrial load, and the 400 MW level was breached around 1.43 pm.
In response, AEMO has sent instructions for 71 MW of distributed solar PV to be scaled back, to ensure that a minimum operational demand of 400 MW is maintained (see the blue line above for its impact).
About 14 megawatts of that downsizing came from the new Smarter Homes initiative, which requires that all new installations and upgrades have inverters that can bypass disturbances, and that “agents” are appointed with the ability to shut down the solar system when needed.
The other 57 MW came from direct control of solar systems above 200 kW through AEMO’s SCADA system, and from voltage control.
A review of this event – a world first – has led AEMO to review the settings and some protocols for how it will run in the future.
“This event is significant because it involved the active management of consumer DPV,” the report says. “Under current market structures, this is recognized as a ‘last resort’ measure, and should only be considered when other options for maintaining the security of the energy system are unavailable or have been exhausted.”
AEMO found it vanished due to an unexpected drop below its operational minimum, resulting in a 40-minute delay in downsizing.
As a result, it is now implemented early warning system To account for potential changes to projected demand, it recommended changes to the Smarter Homes software to ensure PV systems are cut “at the counter” to ensure greater clarity and accuracy of interventions.
It also gave itself more flexibility by replacing the fixed minimum demand of 400 MW with a “dynamic” demand threshold calculated on forecast conditions.
“This dynamic demand threshold manages both the risk of insufficient demand for scheduled minimum batches of concurrent units and contingency DPVs exceeding safe limits,” she says.
“Depending on forecast conditions, the dynamic demand threshold may be lower or higher than the previous threshold of 400 MW. Downsizing is expected to reduce unnecessary DPV while keeping the power system safe in scenarios where the 400 MW threshold will not be sufficient.”
Giles Parkinson is founder and editor economy renewal, who is also the founder of One step off the grid and founder/editor of the EV-focused vehicle motivation. Giles has been a journalist for 40 years and is a former business and deputy editor-in-chief of the Australian Financial Review.