PSS™MUST results are subject
to the following assumptions:
The assumptions inherent in the use of DC power flow for incremental
flow changes.
The initial starting point for analysis can be obtained from
the AC or DC load flow solution or from user-defined data (normally
obtained from SCADA/EMS measurements).
Contingencies are modeled using linear compensation methods
Subsystems (control areas) may be defined using area/zone definitions,
which are defined in the load flow base case. Bus-by-bus adjustments
to the subsystem definitions may be made.
Transmission losses are allocated to individual buses across
the system from an initial base case AC load flow solution.
Phase shifters can be assumed to operate either with fixed
angles (locked) or with fixed power flows, if for controlling
phase shifter.
The MW flow of DC lines remain constant at the base case values.
PSS™MUST can evaluate the impact of transactions within
AC-connected areas. Transactions over DC lines have to be modeled
by using intermediate buses.
PSS™MUST can be viewed as
a customized software product specially tailored for fast analysis
of available transfer capability between power system busbar groupings,
enhancing and complementing the PSS™E linear network analysis
functions. The transfer limit analysis function is the only common
function available both in PSS™MUST and PSS™E.
PSS™MUST uses a PSS™E
load flow case as the main input file. PSS™MUST reads solved
power flow cases in PSS™E saved case or raw data file formats.
Only very limited power flow case changing functions are available
in PSS™MUST. PSS™E is the recommended program for
changing the load flow case, though other load flow programs that
can create PSS™E raw data files can be used. It is recommended
that you start with a solved load flow case (or at least check
that it is solvable).
PSS™MUST is compatible with
PSS™E linear network analysis files. Therefore, existing
PSS™E contingency data files, previously designed to run
Activities TLTG, ACCC, or DCCC, can be used unchanged. PSS™MUST
should be able to process all PSS™E files without any changes.
However, PSS™E activity TLTG will not be able to process
most of the PSS™MUST input file extensions.
In particular, the user must specify
the following input data files:
Solved load flow case file in PSS™E saved case
or raw data file format.
Subsystem description data file defining potential
sources and sinks for transactions and subsystems that may be
used for defining monitored elements and contingencies.
Monitored element definition file specifying monitored
branches and interfaces.
Optional EXCLUDE file allowing customization of specified
monitored elements and contingencies.
Solution parameters and reporting options that will be applied
during the session.
Major differences between PSS™MUST
transfer limits analysis and PSS™E Activities TLTG, SPIL,
and POLY are:
PSS™MUST does not require any additional activities
such as PSS™E Activity DFAX. PSS™MUST computes required
factors "on the fly" and is transparent to the user
during the initialization stage and then generates an internal
"sensitivity data base" (CFAX), which is retained
in memory while PSS™MUST is active.
Subsystem definition files for PSS™MUST should contain
all possible subsystems that may be involved in the study and
parallel transactions. If the same control area has different
participation buses or factors for different transactions, several
subsystems should be specified for that control area with different
names. It is recommended to create a Master subsystem definition
file that may contain definitions of 50 to 100 (and even more)
subsystems at once. The present limit is 5000 subsystems.
PSS™MUST provides various additional analysis functions
expanding and enhancing transfer limit analysis.
PSS™MUST has numerous extensions to specify subsystems,
monitored elements, and contingencies significantly simplifying
and enhancing data maintenance, and sharing data between
companies.
