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The Australian energy market operator has given itself more room on the sensitive issue of rooftop solar shutdown after reviewing the only time the initiative must be deployed since it became part of its toolkit more than a year ago.

In March, AEMO did something that it has never done before, and probably hasn’t done it anywhere else in the world-it shut down a large amount of “unplanned” solar energy to ensure that it can maintain the South Australian power grid. Safe state.

The grid in South Australia has the world's leading share of rooftop solar. Last week, it reached an unprecedented level of 92.6% of local demand, helping the local power grid to enter negative operating demand for the first time-another gigawatt power grid that is the world's largest.

Rooftop photovoltaics at this level are still a challenge, but as long as the connection to the Victorian grid is functioning properly, market operators have the tools to ensure grid security. However, when AEMO is concerned that there is a credible risk that the connection may be lost, it hopes to have the option of mandatory shutdown rules.

This is what it did on March 14 of this year, when a major transmission line was out of service due to regular maintenance. This created a real risk that the state might be isolated from other grids, which made it possible to manage high levels of rooftop solar more difficult.

AEMO expects that operating demand will not be less than 400 MW, but the results prove that rooftop solar production is higher than expected-this is the result of the predicted reduction in cloud cover-and the industrial load is reduced, and it exceeded the 400 MW at around 1.43 in the afternoon. level.

In response, AEMO issued a directive requiring the reduction of 71MW of distributed solar photovoltaic power generation to ensure that the minimum operating demand of 400MW is maintained (see the blue line above which shows its impact).

About 14MW of power curtailment comes from the new smart home plan, which requires all newly installed and upgraded inverters to withstand interference, and designated "agents" to be able to shut down the solar system when needed.

The other 57MW comes from the direct control of solar systems above 200kW through AEMO's SCADA system, as well as from voltage control.

The review of the event-as a world first-led AEMO to modify the settings and some agreements on how it will operate in the future.

"This incident is significant because it involves the active management of consumer DPV," the report said. "Under the current market structure, this is considered a'last resort' measure. It is only considered when other options for maintaining the safety of the power system are not available or have been exhausted."

AEMO found that it fell into a short position due to an accidental drop below the minimum operating threshold, resulting in a 40-minute delay in the power cut.

Therefore, it has now implemented an "early warning system" to take into account possible changes in expected demand, and recommends changes to the smart home plan to ensure that the photovoltaic system is cut off at the "instrument" to ensure more visibility and accuracy of intervention.

It also gives itself greater flexibility by replacing the static 400MW minimum demand threshold with a "dynamic" demand threshold calculated based on forecast conditions.

"This dynamic demand threshold manages the risk of insufficient demand for the minimum combination of scheduled synchronized units and DPV contingency that exceeds safety limits," it said.

"According to the forecast, the dynamic demand threshold may be lower or higher than the previous 400MW threshold. In the case that the 400MW threshold is not enough, it is expected to reduce unnecessary DPV curtailment while maintaining the safety of the power system."

Giles Parkinson is the founder and editor of Renew Economy, and the founder/editor of One Step Off The Grid and The Driven, which focuses on electric vehicles. Giles has been a journalist for 40 years, a former business person and associate editor of the Australian Financial Review.

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