Urgent Changes to the Dispatch Algorithm
In accordance with clause 7.2.3 of the Electricity System and Market (ESM) Rules, where AEMO reasonably determines that an urgent change to the Dispatch Algorithm is required to maintain Power System Security and Power System Reliability, AEMO may implement the change.
Where AEMO makes such a change, AEMO must:
- Publish the change on the WEM website, and the reasons the change was required; and
- If the issue that is being addressed is not temporary, AEMO must as soon as practicable, submit a Procedure Change Proposal to formalise amendments into the WEM Procedure: Dispatch Algorithm Formulation.
List of Urgent Changes Made Under Clause 7.2.3
| Change Title | Effective From | Change | Reason |
|---|---|---|---|
| Constraint Violation Penalty Adjustment | 04/12/2025 08:00 |
Update the parameter CVP values defined in the Dispatch Algorithm Formulation Appendix B.:
|
The change is intended to prevent WEMDE from decommitting Facilities that should have been trapped on at their Enablement Minimum in certain edge cases relating to combined contingencies (i.e. contingencies consisting of multiple Facilities). The correct behaviour is for WEMDE to respect relevant FCESS trapezium limits. |
| Constraint Violation Penalty Adjustment | 05/11/2025 08:00 |
Update the parameter CVP values defined in the Dispatch Algorithm Formulation Appendix B:
|
The change is intended to prevent WEMDE from decommitting Facilities that should have been trapped on at their Enablement Minimum. The correct behaviour is for WEMDE to respect relevant FCESS trapeziums and solve for a shortfall. |
| Constraint Violation Penalty Adjustment | 30/10/2025 08:00 |
Update the parameters CVP values defined in the Dispatch Algorithm Formulation Appendix B:
|
This change is intended to prevent WEMDE from violating safe limit and defined contingency constraints by lifting the priority of the relevant constraints, as defined in Dispatch Algorithm Formulation sections 2.4.55 and 2.4.56. Correct behaviour is for WEMDE to automatically reduce contingency sizes and RoCoF shortfalls. |
| ESS Enablement Pre Processing Flag calculation changes | 12-Oct-2023 08:00 | Include calculations for new “EnablementMinPreProcessing” and “EnablementMaxPreProcessing” values to be used in the Essential System Service pre-processing step (Dispatch Algorithm Formulation 2.5.4). |
Previously, minor telemetry errors and Facility droop could result in Facilities operating near the edges of their ESS trapeziums being unintentionally decommitted from FCESS services and potentially energy. This change adds a tolerance to the ESS pre-processing calculations so the Dispatch Algorithm can allow for minor Facility output deviations driven by droop, telemetry errors, or small variations in output. |