The operators of four large scale solar farms in north Queensland have found that “tuning” their inverter settings has enabled them to solve “system strength” issues at a fraction of the cost of the current default mechanism – spinning machines.
Ian Christmas, head of engineering at Edify Enegy, told a Clean Energy Council large scale solar forum last week that the inverter tuning at four key solar farms – Whitsunday, Daydream, Hayman, and Hamilton – would address recently declared system strength issues in that part of the grid at one twenty-fifth of the cost of installing a synchronous condenser.
He also said it could be done in a fraction of the time – around four months compared to fourteen months or longer for the alternative. “It’s significant enough (in terms of price and time) that it is a no brainer,” Christmas said.
That a cheaper solution has been found for system strength is significant, because it highlights how new technologies are proving that they can provide many of the services previously thought only possible through spinning machines, such as those used in coal, gas and hydro plants.
Until now, those wind and solar farms that have found themselves in parts of the grid with system strength issues have been obliged to spend tens of millions of dollars installing synchronous condensers, a technology that dates back more than half a century and which provide large spinning machines that do not burn fuel.
But this has created problems. It’s added huge costs to those wind and solar farms, but the installations have also occurred in such an “ad-hoc” manner, thanks to a regulatory ruling ironically dubbed “do no harm”, that network owners such as Transgrid complain has actually made the situation worse rather than better.
But as the renewable transition marches on, so too does the understanding of what these new technologies can do, and how they can be applied to issues that arise in the grid.
Perhaps the biggest example of this is with battery storage, which can do significantly more than simply store excess power for use at a later time: It can provide frequency control, synthetic inertia and can be “grid forming” – pretty much covering the range of “grid services” now delivered by traditional generators.
One of the biggest break-throughs occurred last year when five large scale solar farm in the “west Murray” region of the grid (northwest Victoria and western NSW) had their output cut in half due to newly discovered “oscillation” issues.
That was finally resolved through the “tuning” of the SMA inverters that happened to be common to all those solar farms, dubbed the “Murray 5” and the constraint was relaxed last April. It just so happens that SMA inverters are also common to the four solar farms in north Queensland that have found this work around.
As of last week, the firmware at the Hayman and Daydream solar farms had been updated, tested and validated, while Hamilton and Whitsunday are still being completed.
It’s a relief to Christmas and the team at Edify, which has previously had to install syncons at other projects, such as Darlington in NSW, at great cost.
Christmas notes: “I think we as engineers need to stop and pause and ask ourselves a question: can we overcome the current challenges we have with the existing assets that we have.”
That’s a point reinforced by SMA’s head of service Scott Partlin, who has been leading the solutions package for both the Murray 5 and the Queensland solar farms.
“We can do so much more with the kit we’ve got, if there is more latitude in the rules to tune and work with the existing kit to optimise its performance for the kit,” Partlin says, noting that some of the assumptions in the grid rules and connection agreements did not recognise the potential solutions that could be found with the technologies.
Any modifications usually meant that the connection agreements had to be re-cast, which can be highly problematic. “The Murray and Queensland situations show that collaboration is the only way it will work,” he says.
These are issues and questions that are being asked of this and other challenges around the grid. To be sure, some new synchronous condensers will be installed in the main grid, but it is argued that this should only occur in a planned way at the network level, as is happening in South Australia, where the addition of four syncons should dramatically reduce the need for gas plants to operate.
In time, however, even the services offered by syncons will likely to superseded by the expanding capability of inverters. It’s just part of the voyage of discovery for engineers, operators, regulators and investors on what is possible as grid heads towards zero emissions.