Most inverters for rooftop solar and storage wrongly installed, audit finds

The Australian Energy Market Operator is calling for urgent action on installer standards after a check-up on industry compliance with changed inverter standards found less than one-third of inverters in new solar, battery and EV charging system had been correctly installed.

AEMO commissioned a random audit of inverters installed over the past 12 months and found that only 28% of systems with visible settings could be confirmed to have the correct settings, according to new rules that came into play in December 2021.

More than half – 55% – of the inverters tested displayed settings that were incorrect in some way, while the remaining 17% of inverters checked were partially correct or had some settings not visible.

For around half the inverters randomly tested, the auditor was unable to confirm what settings were applied.

AEMO’s findings on inverter compliance follow changes to rules governing technical settings for new inverters that were published by the Australian Energy Market Commission in December 2020 and became mandatory for all new installations 12 months later.

The rule change was requested by AEMO in a bid to gain greater control and visibility over distributed energy resources; first and foremost rooftop solar, which by 2020 was rapidly contributing up to 50% of instantaneous demand across the grid, and much more in South Australia.

As RenewEconomy has reported, the AS/NZS 4777.2 Grid connection of energy systems via inverters, Part 2: Inverter requirements update differs from the rules rushed through in South Australia in 2020 in that it does not require solar households to nominate an “agent” to switch off their solar if asked to by the market operator.

That is certainly on AEMO’S wish-list for NEM-wide inverter standards as it braces for distributed energy resources like rooftop PV to at least double in capacity by 2040. But in 2020 the AEMC decided to bed down some more basic inverter standards first.

To that end, AS/NZS 4777.2 makes it mandatory for all new inverters connecting to the grid to have an undervoltage disturbance ride-through capability, to ensure household energy systems don’t ‘trip’ or disconnect when there are voltage disturbances on the network.

Essentially, as Alison Potter explains here, the mandated operational settings give behind the meter resources ranging from rooftop solar to electric vehicles the ability to respond to conditions on the grid that might otherwise cause blackouts, power instability or PV systems to trip and shut down.

And while the AEMO audit confirms that all new inverters tested in the audit process are technically capable of meeting the standards required, a worryingly small percentage of new inverters installed since December 2021 have been configured according to the mandated settings – a job that falls to installers.

“When configured properly to the 2020 standard, most inverters appear to be designed appropriately to deliver the disturbance ride-through behaviours necessary to support power system security,” the AEMO report says.

“In the field, compliance with technical settings is poor; a wide range of data sources consistently indicate that less than half of systems installed are set correctly to the required standard.”

AEMO says the poor compliance with the nearly 18 months-old rules points to deficiencies in governance frameworks for monitoring and enforcing the implementation of the mandated technical settings in the field.

And it sets out how important it is for installers to start toeing the line on inverter standards – and fast.

“If compliance with the 2020 standard remains poor, there will be continuing growth in the amount of [distributed solar PV] installed with poor disturbance ride-through capabilities,” the report says.

This, in turn, increases the threat from distributed energy resources to the stability of the grid, and therefore increases the likelihood that other protective measures – such as rooftop solar curtailment – will be put in place instead.

And to remedy this, AEMO is calling on industry and regulatory groups to work together to achieve upwards of 90% compliance on inverter standards by the end of this year.

“At this time, it is clear that whilst the impacts of non-compliance are complex and multifaceted, this issue is already causing serious power system security challenges,” the report says.

“Poor disturbance ride-through of DER is identified as the most serious and urgent barrier to achieving successful, secure and reliable operation of the [grid]… with high levels of DER.”

“On this basis, AEMO recommends that industry efforts focus on improving compliance urgently, targeting at least 90% compliance of new installations with AS/NZS4777.2:2020 by the end of 2023, complemented by ongoing governance frameworks to maintain and further improve that level of compliance.”