AEMO slashes output of five big solar farms by half due to voltage issues

The Australian Energy Market Operator has taken the dramatic move of slashing the allowable output from five solar farms in Victoria and NSW by half, because of issues over “system strength” that appear to have suddenly emerged.

The solar farms involved are Broken Hill in NSW, and the Karadoc, Wemen, Bannerton and Gannawarra solar farms in north west Victoria. The constraint limiting them to just half of their nominated capacity came into effect at 12pm on Friday, as this graph below illustrates.

Broken Hill slashed its output from 52MW to 26MW from that time (orange line in graph above from 12pm), Gannawarra (wiggly brown line) went from 50MW to 25MW, Karadoc (green) from 85MW to 42MW, Wemen (blue) from 82MW to 40MW, and Bannerton (pink) from 78MW to 39MW.

It is the latest in a series of blows to the solar industry, which has been afflicted by connection and commissioning delays, resulting in a blow out of costs and claims of damages to construction firms, as well as big changes to marginal loss factors, and the requirement for some to spend lots of money on synchronous condensers or other machinery.

To add to their woes, many solar farms in Queensland and South Australia have been forced to switch off during periods of negative pricing, either because they are required to do so under their off-take agreements, or because they are not willing to pay others to take their output over sustained periods.

Most of the solar farms affected by this latest ruling have been operating for some time – and in the case of the 53MW Broken Hill solar farm for four years. But it seems that the issue only emerged in a review just recently.

Some complained about the “blanket” approach to the constraints, but apparently it is difficult for AEMO to apply individual constraints in this instance. They wanted the issue resolved as soon as possible because of the potential revenue impacts. There is also concern about “contagion” into other regions.

The general market advice came in an oblique and typically coded market notice issued by AEMO just after 12pm. However, in a statement issued to stakeholders late Thursday, AEMO said it was working closely with a “number of solar farms” and network service providers to manage identified voltage fluctuations in north-west Victoria and NSW.

“Close analysis and management of this issue is required to ensure power system security across the associated parts of the Victorian and NSW 220kV electricity network,” it says.

“Until the fluctuations are resolved, AEMO will need to partially constrain the affected generators to manage power system security. AEMO has been working closely with all impacted generators, and anticipates an expedited remediation, reducing the impact and timeframe of required constraints.”

People involved say that the issue was raised in the last couple of weeks, and a solution is being worked on. But some expressed surprise the constraint was being imposed on solar installations that had been in operation for more than a year.

The blame has been levelled in roughly equal proportions (depending on who you speak to) at AEMO, at the solar farm developers, and at the antiquated market rules and regulations.

The latter is cited because, while new generators – be they wind, or solar – have to produce detailed modelling of the impact of their new asset on the wider grid, many are doing so in the dark because they do not have access to the full data required.

“The only way to solve this it is to have the whole network data available to the applications,” said one industry participant. “But the plant owners only get access to a theoretical model of the network, not a dynamic one”.

Others pointed to the general lack of planning and evolution from the energy industry’s policy makers and institutions, who have been caught with their guard down over the pace of technology, and have failed to make adequate planning for infrastructure (networks) and rules for the changes that have occurred.


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