Why AEMO wants the power to cut off your rooftop solar

The Australian Energy Market Operator has sought to reassure solar households across the country’s main grid that proposed new powers to switch off rooftop PV, en masse, would be used “only as a last resort measure” and in “exceedingly rare circumstances.”

AEMO has released and responded to the major themes of stakeholder submissions relating to its Renewable Integration Study (RIS) Stage 1 report, where it first unveiled in details its proposal to have the power to switch off rooftop solar PV if needed to maintain grid security.

The RIS report, published in April, confirmed AEMO’s plans to seek improved inverter standards for all new rooftop solar PV systems, to help it gain more visibility over the increasing rooftop solar pie, and give it the ability to “curtail” rooftop solar output when needed.

The proposed far-reaching controls – which have already become a reality in South Australia, thanks to that state’s world leading rooftop solar penetration, and may soon follow in Victoria and Western Australia – were the subject of most of the stakeholder submissions AEMO received on the RIS.

These included 575 submissions from consumer supporters of advocacy group Solar Citizens, most of which sought clarification on when and how often such an intervention might happen. Others called on the AEMO to find “more progressive and forward thinking” plans for emergency power maintenance, the report says.

As Solar Citizens put it in the report, such a large number of submissions by individual householders is “highly unusual for an AEMO technical study,” and illustrates a need for AEMO to lift its game on engagement with end-users of rooftop solar.

In this spirit, AEMO says in the report that it “understands concerns raised” by stakeholders, and seeks to reiterate that emergency distributed PV (DPV) curtailment would be used “only as a last resort measure” in “exceedingly rare” circumstances, and when all else has failed.

“An example of such circumstances could be the combination of both high DPV generation online and low underlying demand… (and) an extreme abnormal system event… such as a major incident in the transmission network resulting in an entire region islanding from the NEM or at elevated risk of separation, significantly reducing inter-regional transfer capacity,” the report says.

AEMO also seeks to compares the potential use of emergency DPV curtailment as similar to other emergency backstops available, like load shedding, which are used only as a last resort to prevent a broader grid failure and widespread blackouts.

“Load shedding is used in rare, extreme abnormal system conditions as a last resort to maintain power system security when demand exceeds available supply and market-based responses have not been able to address the deficit,” the report says.

“Similarly, DPV curtailment will be required for managing power system security, if unusual operating conditions arise.

“All large-scale generation output is controllable when necessary. This is now an essential capability for distributed resources, as they comprise such a large proportion of total system generation at times.”