Simulator 16 User Guide - PowerWorld

done if the Generator Cost Modeling field is Change to Specified Points per Curve. Default =
5.
MWs per Cost Curve Segment
Specifies the number of MWs for each segment of the piecewise linear cost models that are
automatically inserted for those generators that are modeled using cubic cost functions. This is only
done if the Generator Cost Modeling field is Change to Specified MWs per Segment. Default
= 10 MW.
Save Existing Piecewise Linear Cost Curves
Generators that are modeled with cubic cost curves may have existing piecewise linear cost curves
which may have been manually entered by the user. These curves may or may not resemble the
cubic cost function. During the OPF solution the existing piecewise linear cost curves are replaced
with the auto-created cost curves. If this option is checked then the existing piecewise linear cost
curves are restored at the end of the OPF. The default and recommended option is false since this
allows one to view the actual cost curves used by the OPF.
If you would like to use a particular piecewise linear cost function simply make sure that the
generator is modeled using the piecewise linear model, which can be set on the OPF Generator
Records display.
During the Initial OPF Power Flow Solution
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Modeling of OPF Areas/Superareas
Choose what manner of generation control you wish to be employed in the FIRST power flow
solution the OPF will perform, which will establish the base case load flow condition for performing
the subsequent OPF generation dispatch.
During Stand-Alone Power Flow Solutions
Choose what manner of generation control you wish to be employed in all load flow solutions
FOLLOWING the initial load flow solution. In other words, after the LP OPF routine has determined
the new generation dispatch, what type generation dispatch should be used during the normal load
flow solution.
NOTE: it is NOT recommended that you use Economic Dispatch in this case, although it is an
available option. The reason it is not recommended is that you will remove the optimal dispatch
(including constraints) just determined by the OPF in favor of lowest cost economic dispatch, which
will likely result in the re-introduction of overloaded elements that were corrected by the OPF
dispatch in the first place.
Treat Area/Superarea MW Constraints as unenforceable even when the ACE is less than
the AGC Tolerance (default is checked)
This option by default is checked, which means that if Simulator solves an OPF and the generators in
an area or super area are all either at their minimum or maximum outputs, and the area control
error is still not 0, then the area MW constraint is considered unenforceable and Simulator will assign
a large penalty cost (usually $5,000/MWhr) to the LMP's of the area. However, if you deselect this
option, you give Simulator the additional control of checking the ACE mismatch against the AGC
tolerance for the area, and if the ACE mismatch is less than the AGC tolerance, Simulator will
"acquire" the mismatch amount from the system slack bus for the area, and the area will not be
considered unenforceable in the OPF solution. The AGC tolerance is usually small, and therefore the
amount of power taken from the system slack bus will also be small. The purpose of this option is to
allow for valid LMP solutions in an area that is meant to reach its full minimum or maximum
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