AEMO conducts the market through a centrally-coordinated dispatch process (please refer to SO_OP_3705) that pools generation from producers and delivers required quantities of electricity from the pool to wholesale consumers.
Specific activities in achieving this include managing the bidding, scheduling and dispatch of generators, determining the spot price, measuring electricity use, and financially settling the market.
AEMO performs various functions and processes that require different types of regional demand. The following document outlines the composition, use and publication of the different types of demands and associated terms used in AEMO’s Electricity Market Management Systems (EMMS) Data Model for National Electricity Market (NEM) participants or other interested parties.
Spot market operations timetable
The spot market operations timetable sets out the due dates and times, frequency, and period covered by information to be provided to or from participants in relation to the operation of the spot market.
- Spot Market Operations Timetable (398 KB, pdf)
NEM dispatch engine
The NEM dispatch engine (NEMDE) is the software developed and used by AEMO to ensure the central dispatch process 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 would, if not catered for, cause NEMDE to fail to solve. Such a failure is unacceptable, so AEMO has procedures to ensure dispatch and pricing continue. These procedures are referred to as constraint relaxation procedures.
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 (CVP price), and are selected to control which constraints 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 constraint relaxation procedure, in the document below, was developed in consultation with registered participants.
For more information on constraints documents please see the Congestion Information page.