Hi team,
We've found a few instances of a plant having ClearedMW in the Cleared Offers file which is incompatible with the offers submitted for the plant for that given time period.
Example:
7/05/2025 12:00:00 pm
THI2201 THI1 cleared 59MW with an offer of one tranche of 25MW at 0.01 and 75MW at 5000.
Help with clarifying our misunderstanding here is much appreciated.
Regards,
Perry
Hi Team,
Just seconding this with my own experience, I saw some cleared offers MW in the files here https://www.emi.ea.govt.nz/Wholesale/Datasets/DispatchAndPricing/ClearedOffers for 5 minutes intervals where the GDX here didn't have corresponding offers https://www.emi.ea.govt.nz/Wholesale/Datasets/DispatchAndPricing/GDX
Not too sure if I'm missing something, if the mismatch is just for plants ramping up/down, or if it's something else but it would be nice to know what these cleared offers really reflect.
Regards,
Gislain
I haven't had a chance to delve into the example you cite so I'm not saying that what follows is the answer in this instance. But there are legitimate reasons why the MW the system operator clears a plant at can differ from what was offered.
The SO might constrain a plant on for security or other reasons, even if that plant is out of the merit order (or at least one or more tranches of the offer is out of the merit order). When constraining a plant on, the MW could be anywhere between zero and the offered amounty. At first glance, I'd guess that is what is happenning in the example you cite.
Another reason is bona fide offer revisions after gate closure, ie something happens that prevents a plant from generating at the level it offered at. In such cases, only the MW can be reduced - bona fide revisions can't change the price of any tranche.
Hi Perry,
The situation you referred to is a "constrained-on" condition caused by a ramp-down constraint. Below are the details for the trading interval at 07-MAY-2025 12:00 (RTD):
Offer Structure:
Under normal conditions (i.e., without ramp-down constraints), the unit would have cleared at 25 MW.
However, due to the ramp-down limitation, the unit can only reduce its output by 20.833 MW within a 5-minute interval. This means the minimum achievable generation in this dispatch interval is:
80 MW – 20.833 MW = 59.167 MW
As a result, the unit is constrained-on to generate at least 59.167 MW, even though the economic dispatch would have been lower.
I hope this clarifies the situation.
Best regards,
Tuong Nguyen
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