AEMO Constraint Relaxation Procedure
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The NEM dispatch engine (NEMDE) is the software developed and used by AEMO to ensure the central dispatch process is optimal (that is, it maximises value of trade subject to the various constraints). Under some circumstances, it may not be possible to satisfy all constraints that need to be considered in a given dispatch interval. Under these circumstances, the solution is infeasible and would, if not catered for, cause NEMDE to fail to solve. Such a failure is not acceptable, so AEMO has procedures in place to ensure dispatch and pricing continue. These procedures are referred to as constraint relaxation procedure.
The following two processes, together with reports produced by AEMO comprise this constraint relaxation procedure.
- For dispatch, constraint violation penalty (CVP) factors are applied to all constraint equations. CVP factors allow dispatch to select the next-best feasible solution. CVP factors are multiplied to the Market Price Cap (MPC) to obtain the per unit violation price (aka CVP price), and are selected to control which constrains are violated without interfering with central dispatch when the solution is feasible.
- For pricing, an over-constrained dispatch (OCD) rerun process relaxes any violated constraints by the amount by which they are violated. NEMDE will then produce a price that is consistent with the next-best dispatch solution.
The document “Constraint Relaxation Procedure”, provided below, was developed in consultation with Registered Participants.
Constraint Relaxation Procedure
14 Aug 2013 | 364 kb (.pdf)
For further information regarding this documentation, please contact the AEMO Information Centre.