Simulator 16 User Guide - PowerWorld

Because the goal is to stress the system while performing the ATC analysis, there are two power
flow solution options that are set internally as part of the ATC process. These are the options
that specify the minimum per unit voltage for constant power and constant current loads. These
options are both set to 0 pu and override any user-specified settings.
These options are both set to 0 pu during both the base case solution and any contingency case
solution.
Injection Group Options
This button brings up a dialog from which options associated with injection groups can be set.
These are the same options that get set for injection groups when using Island-based AGC and
dispatching using an injection group; the ATC process switches to using an island-based AGC
when iterating and using injection groups for the seller and buyer. The options that can be set
are Island AGC Tolerance, Allow only AGC units to vary, Enforce unit MW limits, Do not allow
negative loads, and how reactive power load should change as real power load is changed.
The sink injection group is set as the injection group to use in the dispatch. When implementing
the transfer ramping, the source injection group is ramped to the required amount and then the
power flow is solved with the sink injection group picking up any required changes. These
changes include adjusting injection in response to change in the source injection group as well as
any changes in losses due to the transfer.
Define Contingency Solution Options
Click this button to open the Contingency Solution Options Dialog. These are the same options
that are set with the contingency analysis options.
Use Specific Solution Options
When checked, the ATC tool will use the solution options defined by pressing the Define
Contingency Solution Options button for contingency analysis. When not checked, all
solutions will use the options defined by pressing the Power Flow Solution Options button.
Regardless of the specific contingency solution option settings, there are two options that will be
set internally by the ATC process and will override any user-specified settings. These are the
options for minimum per unit voltage for constant power and constant current loads. These
options are described in more detail in the Power Flow Solution Options section above.
Force all transfer ramping to occur in pre-contingency states and repeat full CTG
solutions
When using the iterated solution methods, the typical iterated operation is to solve for the
transfer step amount in the post-contingency state, and then apply the transfer step amount to
the post-contingency state and resolve for the next transfer step amount. When this option is
checked, the transfer step amount for each iteration is calculated in the post-contingency state,
but the power flow state is restored to the pre-contingency state before the transfer step amount
is applied. The contingency is then applied after the transfer step amount has been ramped and
the transfer step amount for the next iteration is calculated after the contingency has been
applied. The purpose of this is to take into account the possibility of conditional actions in the
contingency definitions that may not be active in the early steps of the iterated calculations, but
may become active at some point during the application of the iterated steps.
Iterate on failed contingency
This option is only enabled when the option to Force all transfer ramping to occur in precontingency
states and repeat full CTG solutions is selected. When this option is checked
and the power flow fails to solve after the contingency has been applied, a new iteration loop is
©2011 PowerWorld Corporation
1354