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Caveat … Reader’s Note – completed in a rush this afternoon (posted at 16:08, only 2 hours after the spike) so may well be errors!
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Turns out what happened on Wednesday 15th January 2025 is more complex than we’d initially thought, with a number of factors at play.
Allan O’Neil has helpfully pointed out (thanks for allowing yourself to be distracted, Allan!) that the ‘N_NEWENSF1+2_100-INV’ constraint equation was another significant contributor. In this article, we’ll briefly peruse.
Firstly we show a collage of constraint-related widgets focused on the ‘N_NEWENSF1+2_100-INV’ constraint equation, which:
1) was invoked from the 14:00 dispatch interval
2) this was as part of the ‘N-MUTW_88’ constraint set
… we see the scheduled invocation, as at 14:00 time-travelled, from 14:00 to 14:35, so a very brief outage of the Muswellbrook to Tamworth (88) line
3) We see that the constraint equation had the effect of setting the combined Target of New England Solar Farm 1 and New England Solar Farm 2 to be 0MW.
… that’s got to have contributed a sizeable share of aggregate reduction in supply from Large Solar in NSW noted in Part 1 here!
Under the ‘Plain English Translation’ tab (not shown in an image) we see that the formulation of the RHS in the dispatch timeframe is listed by the AEMO as follows:
‘Dispatch RHS =
-0.001 {Limit_zero}
+ if
(-1 x [Number of inverter available for New England Solar Farm 1]
– Number of inverter available for New England Solar Farm 2
+ 101 {Check_INV_WT}) <= 0
then
0
else
10000’
… and the ‘Reason’ given by the AEMO is that…
‘Constraint to violate if New England Solar Farm 1 and 2 inverters availability greater than 100’
… so we wonder what’s happened onsite (or in the AEMO systems) with respect to the availability across the inverters across the New England Solar Farm site?
Looking also at this collage of two different ‘Unit Dashboard’ widgets focused on both units at New England Solar, we see that the units were collectively producing 370MW at 13:55 (i.e. 181MW + 189MW as FinalMW at 13:55) and that this was reduced to be 94MW at 14:00 (i.e. 51MW + 43MW as FinalMW at 14:00)
… so a fair way above the 0MW combined Target we deduced above
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