Generator Commit

Units:	-
Mode:	Input Only
Multi-band:	False
Default Value:	-1
Validation Rule:	≥-1
Key Property:	No
Description:	Number of units that should be committed

Generator Commit predetermines or 'hardwires' the unit commitment either in all periods or selected periods. Commit specifies the number of units that (if available) should be committed. A value of -1 for any period means the unit commitment is to be optimized in the usual way. It is acceptable to mix -1 with non-negative values if you wish to set the commitment pattern only in certain time periods.

As with any property its value can change by date and pattern and scenario, and even be read from a flat text file. Note that any non-negative value of Commit is hard constraint e.g. a value of zero means no units are allowed to be committed. If you want to set a minimum unit commitment instead of a fixed commitment, use the Must Run Units property, as in Table 1.

Generators with the Commit property defined require less unit commitment overhead in the optimization. This provides the simulation with a significant computational boost, and hence it is desirable to set this for all 'baseload' generators, or other generators with fixed or semi-fixed commitment schedules. Commit is ignored when a unit is out of service so there is no need to account for outages when defining the property. Note however that Commit overrides other constraints such as Min Down Time and Min Up Time i.e. if you define Commit = 1 a unit will be committed if available regardless of whether or not Min Down Time gets violated and vice versa for Min Up Time.

The most common use for Commit is for baseload generators, where one would set Commit equal to the number of units i.e. commit the unit is it is available. Another application is with intermediate type units who might commit during certain hours e.g. peak periods, but be either off during off-peak, or freely optimize their commitment in those other periods.

Table 1: Commit and Must Run Units Example
Generator	Property	Value	Units	Timeslice
B1	Units	1	-
B1	Commit	1	-
B2	Units	1	-
B2	Commit	1	-	PEAK
B2	Commit	0	-	OFF-PEAK
B3	Units	1	-
B3	Commit	1	-	PEAK
B3	Commit	-1	-	OFF-PEAK
B4	Units	4	-
B4	Commit	4	-	PEAK
B4	Must Run Units	2	-	WEEKDAY
B4	Commit	-1	-	WEEKEND

In these examples:

The single unit at "B1" will be committed in any hour it is available.
The single unit at "B2" will be committed in all peak hours and off in all off-peak hours.
The single unit at "B3" will be committed in all peak hours, and available for economic commitment outside of those hours.
All four units at "B4" will be committed on in peak periods, and in weekdays there will be at least two units committed, with commitment outside those periods freely optimized.