How renewables caused Scottish grid’s ‘double heart attack’

In December 2017, a National Grid report ‘Performance of Phase-Locked Loop Based Converters’ [PDF] highlighted concerns about the ability of the billions of pounds of investment in HVDC interlinks being installed across the UK to transfer power in all circumstances. Since then, I have been questioning whether power companies – including those in Scotland – have solved the known instability risks.

National Grid identified that these could emerge as a result of progressively increasing the use of renewables while simultaneously closing synchronous generation. Hunterston B nuclear power station’s last reactor, No 4, ran for the final time in January this year, further weakening the Scottish grid.

The National Grid report concludes that “system strength will decrease in our transmission network over the next decade” and that “We have found an increasing risk of converter instability”. It goes on to predict that as system fault levels fall due to increased...