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30 July 2020

Solar curtailment on the rise in North Queensland’s grid

Nine solar farms in the north of the Australian state of Queensland have had conditions placed on their ability to send power into the grid, due to system strength concerns. These projects total 783.5 MW, and with a wind farm and two solar plants already placed in the limited state in March, the total under curtailment is now 1.2 GW.

These plants may now export 80% or 100% of their power only when any of three sets of conditions are met on the part of several nearby coal and hydro power stations; otherwise, they will be fully curtailed.

System strength pertains to the grid’s stability, managing fluctuations in voltage and frequency in the face of a varying balance of supply and demand.

Powerlink Queensland, the state-owned electricity transmission system operator, began a study in May into system strength issues, which should reach a conclusion by the end of the year. Funding of $500,000 AUD was received from the Australian Renewable Energy Agency, out of a total of $1.3 million – the rest provided by AEMO, grid inverter provider ABB, and AusNet Services.

The study is looking into several different technical solutions – ranging from synchronous condensers to altering inverter settings, or simply expanding the transmission infrastructure. Adding energy storage to renewable developments is another option, but it still needs to be discharged at some point. Synchronous condensers are an old and costly technology, but still an option for developers who are too impatient for grid upgrades. Total Eren installed a 100MVAr condenser at its Kiamal Solar Farm in Victoria state last year.

This was in reaction to the curtailment of the three renewable plants back in March, based on the Ross substation, a 275 kV node near the important coastal settlement of Townsville. AEMO declared there to be unacceptably high fault levels in areas of the North Queensland grid – thus obliging Powerlink to address the issue with ‘system strength services’ by August 2021.

Traditionally northern Queensland is a net importer of power from the south, but this is changing, thanks to wind and solar projects taking advantage of the very strong natural conditions in the area. More transmission infrastructure is needed west or south. Indeed, the 1,000 kilometer, high-voltage Copperstring 2 transmission project will begin construction in 2021, leading west into a power-hungry mining region. In the longer term, Townsville will also have its energy demand boosted by green hydrogen projects, as one of the prospective bright spots for that industry in Australia.

Other parts of Australia have had similar issues, most notably in West Murray, where 350 MW from five solar farms was curtailed for seven months. That ended in April, thanks to an inverter adjustment carried out by SMA engineers from Germany – SMA had supplied inverters for all five projects.

West Murray straddles the border of New South Wales and Victoria states. At a great distance from demand centers, it still had 1.2 GW of committed generation projects, and another 3 GW in application phase, as of February thanks to ideal climactic conditions for both solar and wind, and now AEMO is looking into advanced technical solutions to manage this.

In general, Australia’s transmission infrastructure still lies along the old patterns of coal generation; and so do many regulations such as the authorization process for new transmission lines. Renewable Energy Zones, established in areas with strong wind and solar resource along with new transmission lines, are a new approach being pushed recently, to address the distance that often exists between an ideal wind or solar site and demand centers.