Differences In File Formats
PowerWorld Simulator supports loading from and saving to a number of different external formats, including EPC and PSS/E files. There are a number of points where Simulator's handling of a power system is not precisely represented in other formats, so some care must be taken when working with these other files.
GE EPC Files
Buses
Bus names are limited to 12 characters. When writing out to PSLF files, Simulator will truncate names in a way that ensures unique names remain unique.
PSLF specifies the specific voltage setpoint with a Bus record, and then specifies a range with the device (Vband for a shunt, Vmin/Vmax for a transformer)
Generators
GE Baseload Flag is an extra flag used by PSLF in transient simulation only (user-written EPCL code might also use this). Simulator allows you to interpret this field as a Post-Contingency AGC status (Simulator has a separate field for Transient Simulation use).
Simulator has an AVR flag which is set to YES or NO. PSLF uses (Qmax-Qmin) to determine AVR. By default ranges at 2.0 Mvar or less are considered AVR=NO.
Shunts
| GE PSLF | PTI PSS/E | PowerWorld Simulator |
Controllable Shunt | SVD (Multiple allowed per bus) | Switched Shunt (Multiple allowed per bus) | Switched Shunt Control Mode = Fixed, Discrete, Continuous, or SVC Multiple allowed per bus (coordinated control as of version 16) |
Fixed Bus Shunt | SHUNT (Multiple allowed per bus) | Fixed Bus Shunt (Multiple allowed per bus) | Switched Shunt Control Mode = Bus Shunt (Multiple allowed per bus) |
Fixed Line Shunt | SHUNT Assigned to a line. IDs must start with an f or t | No special record. Fields with AC Line GI, BI, GJ, BJ specify the total at each end | Line Shunt Each end of line can have multiple shunts. IDs assigned for multiple shunts. |
G and B for equiv | None | None | Bus fields Nom G Shunt and Nom B Shunt |
Transformers
PSLF allows a tertiary bus number of zero (0). Simulator supports this exclusion of the tertiary bus, but will write it as two 2-winding transformers when exporting to a RAW file.
Multi-Section Lines
In PSLF, intermediate buses are not defined and thus loads, generators, and shunts at these points are not allowed. When writing out to an EPC file, the multi-section line record is ignored if intermediate buses have objects.
Area/Zones for Shunt Objects
PSLF allows area and zone designations for specific branches and transformers. Simulator reads this into EPC specific fields, but does not use them for anything.
Area MW Transactions
PSLF includes tables showing Transactions. The actual scheduled values are informational only. PSLF does not use these MW Transactions in the power flow solution; instead, it includes a field with an area specifying the net MW export. When loading an EPC file, Simulator's area field "Unspecified MW Interchange" is assigned as the "leftover" which isn't included in the transactions table.
DC Lines
In Simulator, there are distinct container objects for both a two-terminal DC line and a multi-terminal DC line (MTDC). In PSLF, there are only definitions of the DC Buses, AC/DC converter, and DC line objects. The groupings are then determined by the topology of the DC line links. PSLF requires that all DC buses throughout the entire model have a unique DC bus number, which Simulator supports.
Super Areas
In Simulator, Super Area objects can be created and each area can be assigned to one super area. This is useful in studying groups of areas which are dispatched together (Electricity Markets). PSLF does not support Super Areas.
Nomograms
In Simulator, Nomogram objects can be created which specify two interfaces and then a two-dimensional limit region. Nomogram limit violation can then be monitored or enforced in Contingency Analysis, ATC, OPF and SCOPF studies. PSLF does not support Nomograms.
PSS/E Files
Buses
PSS/E bus names are limited to 12 characters. When writing out to PSS/E files, Simulator will truncate names in a way that ensures unique names remain unique.
Generators
While Simulator specifies the capability curve explicitly, PSS/E has a separate input file called "GCAP" which specifies the capability (Simulator can read this file).
PSS/E specifies a "bus type" to signify the generator is not on AVR control, while Simulator uses an AVR flag set to YES or NO.
Shunts
See shunt format comparison table above.
Transformers
PSS/E does not support a fixed tap definition on the same side as the variable tap (FROM), thus Fixed tap is always assumed as 1.00.
PSS/E does not specify the intermediate Star Bus of a 3-winding transformer explicitly. The voltage and angle at this point are part of the transformer record.
PSS/E does not allow the tertiary of a 3-winding transformer to be excluded. Simulator allows this, though we do not consider it good practice.
Area/Zones for Shunt Objects
Simulator allows Generators, Loads and Switched Shunts to have a different area or zone than the terminal bus. PSS/E only allows this for Loads. These objects are then treated as tie-lines in area and zone interchange calculations. PSS/E has a specoal solition option to specify whether to include the interchnge as "LINES ONLY" or "LINES AND LOADS". Simulator always uses Lines and Loads.
Area MW Transactions
PSS/E includes tables showing Transactions. The actual scheduled values are informational only. PSS/E does not use these MW Transactions in the power flow solution; instead, it includes a field with an area specifying the net MW export. When loading an EPC file, Simulator's area field "Unspecified MW Interchange" is assigned as the "leftover" which isn't included in the transactions table.
DC Lines
PSS/E requires that all DC buses of a particular MTDC grouping be numbered from 1 to the number of DC buses. Simulator supports this when exporting to PSS/E.
Interfaces
PSS/E has a monitor functionality (MON file) which allows definition of an interface which includes AC branches and Line Open of Close contingent elements.
Injection Groups
Simulator supports the definition of an injection group which represents a group of generators, loads, or switched shunts (and can contain other injection groups). This can bus used for summary calculations, sensitivity-based calculations, or as a source and sink for a transfer. PSS/E has a similar concept called a "subsystem", which you may find in a SUB file.
Super Areas
In Simulator, Super Area objects can be created and each area can be assigned to one super area. This is useful in studying groups of areas which are dispatched together (Electricity Markets). PSS/E does not support Super Areas.
Nomograms
In Simulator, Nomogram objects can be created which specify two interfaces and then a two-dimensional limit region. Nomogram limit violation can then be monitored or enforced in Contingency Analysis, ATC, OPF and SCOPF studies. PSS/E does not support Nomograms.