Enablement of bid Max Avail for semi-scheduled generators


From late 2020, AEMO sought feedback from participants in the Intermittent Generator Forum on the level of support in pursuing changes to the bid energy Max Avail function for semi-scheduled generators. The changes proposed were to enable the bid energy Max Avail function to improve participants’ communication of real-time energy availability for their semi-scheduled generating unit(s). Following the forum, AEMO received support of this initiative and began scoping the necessary changes. AEMO sought further feedback in subsequent forum sessions and via the Operational Forecasting (OPF) mailing list regarding the use and application of bid energy Max Avail. AEMO identified the enablement of bid energy Max Avail would require changes to a number of processes and systems including both NEMDE and PASA.

Use, Design and Operation

The bid energy Max Avail can be used to manage commercial availability in the Dispatch (DS) timeframe however noting this value will also limit the availability of the generating unit in 5-minute Pre-dispatch (5MPD), Pre-dispatch (PD) and PASA processes (DS, PD and Short-Term (ST)) if less than the Unconstrained Intermittent Generation Forecast (UIGF). Participants are expected to rebid if their bid energy Max Avail no longer represents their intended commercial availability. In cases where SCADA Local Limit is unavailable to reflect plant technical capability in dispatch, the bid Max Avail can be used as a backup to reflect the technical capability. The Availability, or Available Capacity, used in the dispatch, 5MPD, PD and PASA processes is the lower of the UIGF and bid Max Avail.

The following outcomes will occur in dispatch as a result of bid energy Max Avail (unless ramp rate limitations apply):

  • If bid energy Max Avail < UIGF, a semi-dispatch cap will be set (to no higher than the bid Max Avail value).
  • If bid energy Max Avail = UIGF, a semi-dispatch cap might not be set – this can occur when SCADA Local Limit is limiting the UIGF and Max Avail SCADA Local Limit.
  • If bid energy Max Avail > UIGF, a semi-dispatch cap will not be set and instead, the dispatch level will be the UIGF (assuming no other constraints are binding).  

Technical limitations and physical plant availability should continue to be managed via the following methods as per Rules requirements, which limits the UIGF:

  • The SCADA Local Limit signal and SCADA Turbines/Inverters Available signal for dispatch.
  • Submission of plant availability in the EMMS Market Portal (or API) for PD/STPASA.

Additional information can be found in the updated documentation and resources.

Participants are advised to refer to the EMMS Technical Specification Data Model v5.2 release which details the changes to the EMMS data model as a result of several different AEMO projects including the enablement of bid Max Avail for semi-scheduled generators.




Sought participant feedback on bid Max Avail in Intermittent Generator Forum (link here)

November 2020, July/December 2021, July 2022


Further information communicated via OPF mailing list

October 2022, May-August 2023


Implementation of bid Max Avail in Pre-Production environment (participant testing)

11 May 2023


Updated (change marked) draft documents sent to OPF mailing list

2 June 2023


Creation of “Enablement of bid energy Max Avail for semi-scheduled generators” AEMO webpage

28 June 2023


Implementation of bid Max Avail in Production environment 

7 August 2023


Further information

For more information, please contact op.forecasting@aemo.com.au

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