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What's in the Simulator 9.0 Patch?

PowerWorld Simulator 9.0 Patch addresses problems that were detected in the program after its release and introduces some new functionality. These modifications are listed here.

The patch was last modified February 26, 2004. (June 4, 2004 for SimAuto)

Minor Updates made to this patch are noted below along with a date and explanation. This patch was first introduced on February 21, 2003.

If you are ready to download this patch, click here to go to the patch download page.

SimAuto

(June 4, 2004) Installations of Simulator 9.0 SimAuto and Simulator 10.0 SimAuto would cause conflicts with Windows. These conflicts have been correct in Simulator 9.0 and 10.0 so that multiple versions of SimAuto can be present simultaneously.

Case Information Displays

(February 21, 2003) Fixed bug which was causing the admittance matrix (Y-bus) to not be correctly updated after changing the nominal MVAR of a switched shunt object.

(February 21, 2003) Limit Monitoring and Violations displays were not being automatically refreshed after a new power flow solution occurred. This now is done automatically after every power flow solution. This includes after the contingency analysis completes a solution.

(February 23, 2003) Modified interfaces which contain contingent elements to ALWAYs show you the post-contingency flow on the interface. This is now always calculated during the power flow solution.

(February 28, 2003) Previously Case Information displays consumed a large amount of computer memory (typically about 2 MB each). The software has been optimized to remove this memory burden to a much smaller amount.

(February 28, 2003) Custom Expressions and Custom Model Expressions utilize an external DLL (ucalc.dll) which must be initialized by Simulator for use. When reading in a list of expressions from an auxiliary file the last expression read from the file would not be correctly initialized, therefore the expression would always return zero. This error has been fixed.

(March 18, 2003) When appending cases in Simulators while also having case information displays open, sometimes access violations would appear. They could be dismissed with no problems and were related to the case information display customizations. These errors will no longer occur.

(March 28, 2003) When performing a topological case comparison, the transformers comparison was not correctly working. This has been fixed.

(April 4, 2003) Added a status column for a bus object to notify you whether the bus is disconnected or connected.

(April 10, 2003) Added the highlighting of required fields inside the Display/Column options dialog. Also added an (*) to denote required fields when showing the variable names for column headers.

(April 11, 2003) When a generator fuel cost was presently 0.0, an divide by zero error would occur when trying to change the fuel cost value to a non-zero value. This error been fixed.

(April 11, 2003) Added support for more complex Advanced Filters which model the mixed AND/OR logic such as A and (B or C).

(April 23, 2003) When changing the Area or Zone Equivalence (Which System?) and Scaling (Scale?) fields, the buses in the Area or Zone would not automatically change to reflect the change in the Area or Zone unless you were interacting on the Equivalencing or Scaling dialog itself. This has been modified so that it works regardless of which case information display you are interacting with.

(April 23, 2003) Modified some refresh issues with case information displays. When hitting the enter key, the Row of the case information would automatically refresh to reflect changes, but when just clicking away from the cell you are editing, the row would not automatically refresh.

(April 28, 2003) Modified transmission branches so that the the column "Xfrmr" could be edited by the user directly for branches that are not obviously transformers. A branch is considered obviously a transformer if any of the following are true: Type <> FIXED, tap <> 1.0, phase <> 0.0, Non-equivalent branch with From Nom KV <> To Nom KV. Obvious transformers are label "Yes" and can not be edited.

(May 2, 2003) Added a column to show the Transformer Configuration of a transformer (Delta-Wye, Wye-Wye, etc...)

(May 7, 2003) Added a column for interfaces which will show the "Scheduled MW" for interfaces which contain area-to-area tie-line elements.

(May 7, 2003) Added an option in the Simulator's Solution/Environment settings that allows you to disable the automatic setting of a generator's AGC status to NO when you change the generator's MW output.

(May 30, 2003) When right-clicking on the Multi-Section Lines Case Information display, the local menu would not always appear. This has been fixed.

(June 10, 2003) When copying a case info display to the clipboard, or when sending to Excel, an extra tab character at the end of each row was added. This has been removed.

(September 10, 2003) Excel uses a single quote at the beginning of a string as an indication that what follows should be treated as a string. If what follows already is a string, the beginning single quote is dropped. This causes problems when trying to paste label information from Excel into a Simulator bus information string grid, because labels require that single quotes enclose them. The code has been changed to insert a single quote at the beginning of the label string that is to be imported if it is not already present.

(September 10, 2003) Fixed an error when setting the generator fuel type field to an invalid setting. In this situation it would always set the fuel type to coal. If a blank entry was specified, an access violation would occur.

(September 10, 2003) Fixed an error when using the toggle All on the contingency element status.

(September 10, 2003) Fixed an error when reading in an aux file from specialized case information displays. Sometimes the text file read in would not be properly closed after the AUX file was read.

(October 31, 2003) When choosing to print directly from a Case Information display, the column headings printed out were sometimes incorrect. This has been fixed.

Bus View Onelines

(February 21, 2003) The Bus View oneline diagrams were improved so that the spacing of the Serial Buses is dynamic, thus allowing a larger number of serial buses for buses which appear to the right of the screen. Also, bus numbers were added next to the serial buses. Also, IDs were added for generators, loads and shunts at the bus.

(March 5, 2003) The Bus View oneline was incorrectly showing mismatches based on the full AC power flow equations when running in DC approximation mode. This has been fixed.

(March 13, 2003) After pressing enter on the bus name/number field on the Bus View oneline, the name/number is now highlighted making it possible just to type in another name/number.

(April 23, 2003) Modified the Serial Buses feature of the Bus View so that serial buses are made wide when appropriate.

(May 7, 2003) Added a denotation in the Bus View that line shunts exist.

(May 7, 2003) Added support for opening multiple Bus View onelines simultaneously.

(May 7, 2003) The options regarding the Bus View onelines are now saved in the windows system registry.

(May 13, 2003) Fixed error introduced on May 7 which disabled the ability to enter values directly into the Bus Name/Number box to bring up new buses.

(June 20, 2003) When opening the line dialog by right-clicking on a line in the bus view, and then choosing the move the terminals of the line, an access violation would occur which could crash Simulator. This bug has been fixed.

(November 20, 2003) Modified the Bus View and Sub View so that they both use the default background color instead of always setting the color to white.

Oneline Diagrams

(February 21, 2003) When have oneline diagrams open and choosing to delete a bus from the Bus case information display, sometimes fatal access violations would occur. This has been fixed. In order to avoid this error without the patch, close oneline diagrams prior to deleting a bus from the case information display.

(February 28, 2003) When using the "Show Oneline Hints" option in Simulator, oneline diagrams which contained unlinked transmission lines would result in nuisance access violations. No harm came from the error. The error will no longer occur after this patch.

(February 28, 2003) When using filtering on the Contouring Dialog errors could be introduced in the reading and saving of the oneline diagrams. This would occur if you (1) used filtering for more than one type of contour (2) saved the oneline diagram, (3) read the diagram back in. After doing this, errors would occur when trying to save the diagram. This has been fixed.

(February 28, 2003) When reading in oneline diagrams which contain memo objects, the oneline display would not be properly initialized. This resulted in many memos appearing even though they should have been hidden because you were not zoomed in on that part of the display. This has been fixed.

(March 7, 2003) Added an option on the Environment tab of the Option/Tools, Solution/Environment dialog which allows the user to specify that they be prompted to save open oneline diagrams when choosing to save their case in Simulator.

(April 23, 2003) Modified the dialog for inserting Line Flow Objects so that it always properly choose the from and to bus direction after clicking on the oneline to insert an object. Previously this would default to the wrong direction sometimes.

(May 7, 2003) Added the ability to insert pie charts and/or circuit breakers on a selection of lines and transformers. This is accessed by right-clicking on a selection and choosing "Add new fields around selection..."

(May 30, 2003) The automatic coloring for load MW fields that are outside their limits has been disabled.

(June 10, 2003) When dragging field around a oneline, users are often prompted about changing the "link" of the field to a new bus or line. The dialog which appears now has a button for "No To All" which will cause this dialog to quite appearing for that session of Simulator.

(October 31, 2003) When inserting fields around a generator, sometimes they were being inserting offset incorrectly. This has been fixed.

(November 4, 2003) Fixed access violation which would occur when right-clicking on a oneline and choose Area Information if the oneline had no bus or substations on it.

(January 10, 2004) Corrected problem where text fields inserted were always inserted black, regardless of the color setting of the default font.

File Formats

(February 28, 2003) When loading in a PowerWorld binary (*.pwb) file saved in Simulator 9.0, the message log would include a line stating that you were loading a "10.0 BETA" version of Simulator. This message was incorrect. You were really loading in a 9.0 file. This patch corrects the message.

(March 18, 2003) Modified to support the reading of PTI RAW Version 29 files.

(March 18, 2003) When reading in Simulator 5.0 PWB files written in late 1999, errors were sometimes encountered. This has been fixed.

(March 25, 2003) Fixed error resulting in the incorrect reading of PTI RAW files prior to version 29 which occurred due to the bug fix on March 18.

(April 11, 2003) Fixed an error when writing out the *.ECF files when reading in GE EPC files. This was resulting in the loss of the extra five rating sets for power system branches.

(April 15, 2003) When writing out the Jacobian matrix to a Matlab *.m file formated file, Simulator previously would write out some unneeded zero entries. This has been changed so that only non-zero entries are written out.

(April 17, 2003) Added support for reading in 6 new flags for generators in the GE EPC file. Five of these flags are not used by Simulator and are saved in the *.ECF file. The flag "AGC_flag" is read and populates the generator AGC status field in Simulator.

(April 24, 2003) An occasional error would result in writing the transformer sections of PTI Version 27 with a missing comma. This has been fixed.

(April 28, 2003) When writing out PowerWorld Binary Case files (*.PWB) to Version 7.0 and earlier, if your case had multi-terminal DC lines defined in it, then you would not be able to read the case back in. This was caused because Version 7.0 and earlier did not support multi-terminal DC lines. A fix has been added which will just skip writing out this information to Version 7.0.

(April 28, 2003) Fixed a bug related to reading in PTI RAW files which had a zone number of zero.

(May 16, 2003) Fixed error when reading the owner number and metered end of transformers to PTI RAW version 27 and later.

(May 16, 2003) Fixed errors when writing out the transfer tap name information and the magnetizing reactance for transformers to PTI RAW version 27 and later.

(May 16, 2003) When reading in zone names from GE EPC files, the zone names were being truncated to 8 characters. This has been fixed.

(May 30, 2003) When using the "Save External System" abilities on the Equivalencing dialog, if the case had Multi-Section lines and a multi-section line spanned the study and external system, then when you read the PWB file with the external system back into Simulator, there would sometimes be problems with the multi-section line definitions. This has been fixed.

(May 31, 2003) Simulator was not properly processing the end of section marker in a PTI raw file if a comment was attached to the end of the section marker. This has been fixed so that it now properly locates the end of the section.

(May 31, 2003) Fixed a bug with reading Transformer Correction tables from a RAW file when reading the values on a computer set to use commas as the decimal point separator.

(June 10, 2003) When reading an AUX file containing a bus renumbering swap list, sometimes Simulator would not correctly find the "end of file" and result in Simulator crashing. This bug has been fixed.

(June 20, 2003) Fixed an error in writing out the magnetizing G and B values to GE EPC files.

(June 20, 2003) Modified the reading of PTI raw files so that comments found at the end of the transformer adjustment data section would not cause errors in reading the file.

(September 10, 2003) Fixed a bug when writing disconnected buses to GE EPC files. Disconnected buses are now written out as type “0” instead of type “4”.

(September 10, 2003) Fixed a bug when writing out shunt data to a GE EPC file. When processing the *.ECF file, sometimes an error would occur.

(September 10, 2003) Enhanced the reading of GE EPC files so that when we read transformers specified as FIXED, we still read their control parameters and retain them. They will then appear later if the transformer is changed to a type of control.

(November 4, 2003) Fixed error when writing out the AUX files that contained line rating pairs while processing the GE EPC files.

(November 10, 2003) Fixed errors when reading the PTI *.con files which contained comment lines and/or blank lines. The file reading routine is now able to ignore such lines appropriately.

(November 20, 2003) Modified the saving of GE EPC files so that the voltage setpoint for buses on switched shunt control is handled correctly.

(December 8, 2003) Fixed a bug with deleting Buses, Lines, Generators, etc... which contain Fault Sequence Data. After deleting these objects, errors would occur when saving the case.

(December 18, 2003) Fixed bug with writing out section numbers for line shunts in multi-section lines segments.

(December 19, 2003) Fixed bug reading with writing out regulated value limits for phase shifting transformers in GE EPC format.

(January 10, 2004) dified to take the highest limit of the sections when merging multi-section lines (such as when reading the GE EPC files or when choosing to merge sections on the MSLine records case information display).

(January 10, 2004) ixed bug where line shunts on transformers were being written both as the magnetizing imedance and as individual shunt records when saving as an EPC file. Line shunts on transformers are now exclusively written as magnetizing impedance on transformers.

(January 10, 2004) Added ability to write out version 29 PTI RAW files.

(January 10, 2004) Fixed bug reading CON files. Problem was that if a line started with a comment errors occurred.

(January 29, 2004) Modified so that when choosing File, Open Project it properly opens onelines and other files.

(February 10, 2004) Fixed error which would result in the loss of zone names when reading in GE and PTI text file formats.

(February 10, 2004) Fixed error in writing out 8 branch limits to AUX files when reading in a GE EPC file. Previously sections of multi-section lines were not properly processed.

(February 10, 2004) Fixed error in automatic determination of the PTI file format version. This sometimes occurred when detecting the Version 29 files.

(February 26, 2004) Fixed error when writing out MS Lines as part of interface records in the GE EPC file format.

.DATA Section of Auxiliary Files

(February 21, 2003) Fixed bug which was causing the admittance matrix (Y-bus) to not be correctly updated after changing the nominal MVAR of a switched shunt object.

(February 28, 2003) When reading in auxiliary files which contained Reactive Capability Curve data in the Generator SUBDATA sections, the program would not immediately enforce those curves until the generation moved a small amount. This has been fixed to immediately enforce the limitations.

(April 4, 2003) Fixed a bug which could result in the creation of power system elements when automatically reading in an auxiliary file while opening Simulator in Edit Mode.

(April 23, 2003) When changing the Area or Zone Equivalence (Which System?) and Scaling (Scale?) fields, the buses in the Area or Zone would not automatically change to reflect the change in the Area or Zone unless you were interacting on the Equivalencing or Scaling dialog itself. This has been modified so that it works from the AUX file format as well.

(April 28, 2003) See note above in Case Information section regarding the Branch column "Xfrmr"

(May 7, 2003) Added another option under the Help, Export Object Fields menu setting for "Send to Excel". This will export the object field descriptions directly out to a spreadsheet.

(October 7, 2003) Modified the reading of the CTGElement SUBDATA section of Auxiliary files so that when it encounters unrecognized contingency actions it does not abort the entire auxiliary file read.

SCRIPT Section of Auxiliary Files

(April 10, 2003) Fixed bugs in the ATC script commands related to handling multiple scenarios.

(April 11, 2003) Fixed bugs which resulted when changing the slack bus by using SCRIPT commands.

(April 15, 2003) Fixed a bug in the ATCDetermine SCRIPT command which would sometimes result in an access violation when using the iterated solution methods.

(April 23, 2003) Added another solution method to the SolvePowerFlow() script command. Users can now choose SolvePowerFlow(Robust) to perform the robust solution method.

(June 11, 2003) Add script support for Move BRANCH and Move LOAD calls

(September 10, 2003) Fixed bug in the ProcessAuxFile and RunScriptCommand SimAuto calls so that they create an empty power system if non presently exists. Previously if you had not opened a case, these commands would not work.

(September 10, 2003) Added more suppression of Simulator pop up messages when using the Change Parameters function of SimAuto

Power Flow Solution

(February 21, 2003) Modified the abilities of Simulator when creating separate islands so that when an island is "dead" because no generation exists, it will be brought back to service after a generator inside that island is closed. This generator will then be chosen as the slack bus for that island.

(February 21, 2003) Fixed a bug which was resulting in generators on "Line Drop / Reactive Current Compensation" Voltage control to not back-off their MVAR limits once they are able to.

(February 28, 2003) An error in the generator MVAR control would occur under the following conditions: (1) Multiple generators at the same bus were on "Line Drop / Reactive Current Compensation" voltage control (2) Some of these generators had a VAR range (Min VAR <> Max VAR), (3) some these generators had no VAR range (Min = Max). The generators with no VAR range would cause trouble. This has been fixed.

(March 5, 2003) An error was occurring in the DC Power Flow with cases which contained Multi-Terminal DC transmission lines. This has been fixed.

(March 7, 2003) Improved transformer/shunt/generator MVAR control switching when the power flow convergence tolerance is set to a larger value.

(March 18, 2003) Removed incorrect warning message to the log regarding "low voltage convergence". The message still appears, but now only when appropriate.

(March 28, 2003) When combining two islands together by closing an AC line between them, previously the slack bus which had the lowest bus number would be maintained as the slack bus for the newly merged island. This has been changed so that the bus which has the largest amount of maximum generator output is now maintained.

(September 10, 2003) When a generator's avr status is switched in run mode on a solved power flow case, the Jacobian was not being recalculated to account for the change in regulation. Thus, any sensitivity calculations, such as those used to compute tap or shunt switching, would be incorrect. The code has been changed to force a recalculation of the Jacobian when a generator's AVR status is switched.

(September 10, 2003) The solution engine uses a technique called “angle smoothing” to help improve convergence when branch is closed across a large angle difference. In cases where such a branch is a phase shifter, the calculation would fail to subtract the phase angle of the phase shifter when computing the required change in real power injection at the terminals of the line. This could harm convergence. This problem has been fixed by subtracting the phase difference of the phase shifter from the cross-branch phase difference when computing the required real power injection.

(September 10, 2003) When closing in a transmission branch whose terminal bus angles were on either side of +/- 180 degrees (for example, -179 and +179), the power flow would have convergence difficulties. A fix was made to the angle smoothing routine so that the angle difference used would be 2 degrees instead of 358 degrees.

(September 10, 2003) Modified the automatic generation control algorithms to fix a problem when trying to manually set the MW output for a slack bus generator when the generator was presently set the AGC=NO. Previously in this situation, the slack generator would continue to fall back to its original setting.

(September 10, 2003) Modified the Multi-terminal DC line control to better handle the loss of all rectifier or all inverter terminals.

(October 31, 2003) When calculating the total line shunts for an area, the inclusion of the line shunts on an area-to-area tieline was not being assigned according to the metered end of the transmission line. This has been fixed.

(November 4, 2003) Modified the Power flow solution so that the angle-smoothing routine is properly called when bypassed a branch which is part of a multi-section line. Previously this would often result in an unsolvable power flow solution.

(November 20, 2003) Modified the Robust Solution Process action so that it refreshes all open onelines and case information displays after completion.

(December 18, 2003) Modified a warning message regarding generators have different setpoints for the same control bus so that it ignores off-line generators. This was not causing problems, but was introducing insignificant error messages.

(February 1, 2004) When running a simulation in Play mode, after the simulation end time is reached, and you had chosen the "simulation never ends" option a bug was occurring resulting in transformer tap positions to not automatically change. This has been fixed.

Security - Constrained OPF (SCOPF)

(February 21, 2003) Improvements have been made in the handling of phase-shifter controls in the SCOPF.

(February 21, 2003) Users may now click the Abort button on the toolbars to abort the SCOPF solution.

(April 29, 2003) Improvements to phase shifter handling in the solution algorithm. Phase shifters used as controls are now controlling MW flow only instead of MVA flow, as was occurring previously.

(June 10, 2003) Fixed a bug when running multiple outer loops in the SCOPF which was causing limiting elements to show as blank.

(June 10, 2003) When using load benefit curves while also choosing to "Use Marg. Losses" for the OPF Areas, an access violation would occur causing the OPF solution to abort. This has been fixed.

(September 10, 2003) There was a bug when setting a super area to non-OPF control when one of its individual areas was set the OPF control. Generators in the sub-areas set to OPF control would participate in OPF control dispatch even though their super area should have been overriding this activity. This has been fixed

(September 10, 2003) Modified the OPF calculation so that all buses that are not in an Area or Super Area which is participating in OPF dispatch will have their marginal costs (LMPs) set to zero.

(September 30, 2003) Fixed bug which occurred when solving DC approximation and the Primal LP after making a change to the system. This would result in a change occurring at the slack bus temporarily which would then get set back at the next solution.

Contingency Analysis

(February 21, 2003) Added ability to automatically generate a contingency list from a list of interfaces which contain contingent elements. This is accessed from the right-click popup menu on the interface records display.

(February 21, 2003) Added some more options to the contingency text reporting options. Users may choose to only show limit violations summaries for types of violation that actually occurred a particular contingency. Users may choose which types of violations to show (Line, high voltage, low voltage, interface).

(February 23, 2003) Fixed a bug that sometimes caused an access violation after doing the following in this order (1) run through a list of contingencies (2) delete all the contingencies, (3) open new contingency list from an aux file, (4) run new list of contingencies.

(February 28, 2003) Contingency Reporting has been updated so that the list of line violations indicates the direction of the violation. The order of the from and to bus indicate the direction now.

(May 16, 2003) Fixed bug in the linear contingency solutions when using the MOVE Load action.

(May 16, 2003) Fixed bug in the Full AC contingency solution when using the MOVE Gen by a specific MW amount action.

(May 16, 2003) When using the linear solution methods, transmission branches that were presently out-of-service were never being monitored for overloads, even if part of the contingency definition involved closing in the branch. The contingency analysis (and thus ATC) was modified to monitor the post-contingency flow on such branches.

(May 30, 2003) Restoring the original state of generators that use reactive capability curves would fail to restore minimum and maximum var limits of such generators. This problem affected only units that use reactive capability curves. The problem has been fixed.

(June 10, 2003) When restoring a reference state after a contingency which results in the creation of new islands in which there is a generator that is separated from its remote-regulation bus, the remote regulation percent of the generator would not be properly reset. This has been fixed.

(July 11, 2003) Further fix related to June 10 bug with restoring remote regulation percent.

(June 20, 2003) When writing out PTI *.con files, there was an error with writing the MOVE Load contingency actions. A space was missing in the file. This has been fixed.

(Juen 20, 2003) A bug was fixed in the contingency actions for GEN SET or CHANGE. If the present generation at a bus was equal to zero, a divide-by-zero error would occur. This has been fixed.

(September 10, 2003) Fixed some formatting issues in the contingency reports

(October 7, 2003) Modified the system state so that it stores the generators Min/Max Mvar, Reactive capability curve, and the Use Capability Curve flag.

(October 7, 2003) Modified the reading of the CTGElement SUBDATA section of Auxiliary files so that when it encounters unrecognized contingency actions it does not abort the entire auxiliary file read.

(October 21, 2003) Modification on October 7 for including the reactive capability curves in the system state resulted in a large memory leak. This has been fixed.

(November 20, 2003) Modified the power flow solution when called to perform a post-contingency solution so that it will skip the optimal multiplier for 3 iterations after each redispatch of generation. This helps speed up power flow convergence substantially as you approach voltage collapse.

(December 8, 2003) Changed the modification from Nov 20 so that the optimal multiplier is not skipped on the very first inner loop power flow solution of the post-contingency solution. It only skips the optimal multiplier as it's trying to "narrow in" on the generator dispatch.

(February 26, 2004) Add the owner field as a potential field when displaying the list of violations associated with a contingency (the lower left list display on the Contingency Analysis dialog).

Sensitivity Calculations (PTDF, GSF, TLR, LODFs, etc...)

(April 28, 2003) In the TLR/GSF calculation, buses with a status of "Disconnected" would always show a P sensitivity value which was equal to the sensitivity at the island slack bus. In reality, the sensitivity at such a bus is not defined, the patch has been changed to show this value as 0.0.

(April 28, 2003) When choosing the transactor to the slack bus, the slack bus for the island with the largest number of buses is now chosen. Previously, the sensitivity at each bus would be with respect to going to its own island's slack bus.

(April 28, 2003) Modified the TLR/GSF calculation so that transactors such as Areas, Zones, Super Areas, or Injection Groups which span more than one power system island are not allowed.

(April 28, 2003) Modified the TLR/GSF calculation so that the P Sensitivity for Areas whose generators span more than one power system island always show a P Sensitivity of zero.

(May 16, 2003) When calculating LODF values, transmission lines with a present status of OPEN would show LODF values (this was actually a value related to how much the flow on that line would change if the line was actually in service). This has been modified so that out-of-services lines show an LODF value of 0.0 instead.

(May 30, 2003) When calculating the TLR/ GSF values for a transmission line which was out-of-service, the calculation would compute non-zero values (the was a value related to how much the flow on that line would change if the line was actually in service). This has been modified so that if the line is out-of-service, then all values are calculated as zero.

(June 5, 2003) When calculating the TLR Sensitivity for a transmission branch that is directly connected to the slack bus, the sensitivity value determined for the slack bus was incorrect. This bug has been fixed.

Available Transfer Capability Add-on (ATC)

(March 7, 2003) Modified the Multi-Scenario Results summary grid so that the background color corresponds to the most limiting element solution method when using the Iterated Solution Techniques.

(March 13, 2003) Fixed bug which resulted during iterated ATC solution methods (especially when including the full contingency soltion). Simulator was not properly handling a divergent power flow solution as you iterated on individual transfer limitations.

(April 17, 2003) Fixed a bug introduced in the April 11, 2003 patch which was causing problems when running multi-scenario ATC analysis runs.

(April 24, 2003) There was a large memory leak which would occur only when running the ATC using the "(IL) then Full CTG Solution" method. This has been removed.

(May 7, 2003) Fixed an intermittent bug caused when using the "(IL) then Full CTG Solution" method while studying multiple scenarios. If a contingency which was implemented resulted in additional islands being formed, then the next scenario could abort saying that the buyer or seller is split into two islands. This bug has been fixed.

(May 13, 2003) Users could not use the iterated methods to find limitations for Interface flows. This has now been enabled.

(May 13, 2003) Contingencies which involved the outage of a one of a set of parallel lines which connect a radial system we behaving as though all the parallel lines were being outaged. This has been fixed.

(May 16, 2003) ATC calculations which monitored post-contingency interface flows were not working properly. This has been fixed.

(May 16, 2003) ATC calculations would not work properly for contingencies which involved the action CLOSE Branch.

(June 5, 2003) When using the (IL) then Full CTG Solution method in conjunction with contingencies involving actions with a status of POSTCHECK, it is possible that a violation may disappear after the full contingency solution is implemented. This would signify that the transfer limitation will not limit the ATC. Previously Simulator would erroneously report a transfer limitation which was equal to that found using the Iterated Linear method by itself. It has now been changed to report a very high transfer limitation to let the user know that it is no longer limiting the transfer.

(September 23, 2003) Fixed a bug in handling the calculation of ATC when monitoring interfaces that contain contingency elements.

(February 10, 2004) When using the Iterated the Full CTG solution method, the post-contingency solution options were not properly maintained after the full contingency solution was implemented. This has been fixed.

PV and QV Curve Tools (PVQV)

(March 13, 2003) Modified the QV curve calculation so that QV curves can be calculated even if the contingency can not be solved under the base case condition. This is achieved by inserting the fictitious synchronous condenser into the power system before performing the contingency allow additional reactive power support, potentially resulting in a solvable power flow. If this provides a solvable starting point the QV curve can be traced resulting in a bus with "negative reactive margin).

(March 13, 2003) Modified the PV curve tool to allow phase shifter to be locked during the curve process. Previously, phase shifters were not properly being locked.

(April 24, 2003) When writing QV curve text files, a line break was missing after the string Q(MVR), V(pu). This has been added.

(April 24, 2003) There was a bug which occurred when automatically launching the QV curve tool after performing a PV analysis when studying cases which had multi-terminal DC transmission lines. The bug would cause the program to freeze. This has been fixed.

(May 9, 2003) When the initial case was unsolvable, the PV curve which not properly report the inability to continue. This resulted in a crash. This has been fixed

(May 30, 2003) Restoring the original state of generators that use reactive capability curves would fail to restore minimum and maximum var limits of such generators. This problem affected only units that use reactive capability curves. The problem has been fixed.

(May 30, 2003) A bug was fixed which was resulting in the QV tool not using the proper minimum, maximum and voltage stepsizes for individual buses.

(June 10, 2003) The qv curve tool seemed to enter an infinite loop when the case was unsolvable and you attempted to get it to solve by increasing reactive injection at the study bus. The starting state was not being restored properly, making it very difficult to get the case to solve by changing the Q injection at the study bus. This has been fixed by restoring the solvable state in its entirety before adjusting the synchronous condenser at the study bus.

(September 10, 2003) In the QV tool, if a QV run is performed at a bus with a switched shunt, the shunt would be held fixed instead of switched. This has been fixed by having the shunt switch to restore the voltage after the fictitious synchronous condenser has established the new voltage setpoint.

(September 10, 2003) QV tool now records both the output of the QV synchronous condenser and of any shunts at the QV test bus.

(September 10, 2003) The QV tool seemed to enter an infinite loop when the case was unsolvable and it attempted to find a level of Q injection at the study bus to make the case solvable again. The problem was that no attempt was being made to start the solution from a solved case because a solved case was never being restored. This problem has been fixed.

(September 10, 2003) The ability to make an unsolvable case solvable through the action of the QV synchronous condenser has been extended in two ways: (1) whereas the tool used to be applied only to unsolvable contingency cases, the capability can now be applied to an unsolvable base case as well; (2) instead of scanning set point voltages just in descending order, the tool will now search for a solvable voltage setpoint for the synchronous condenser in the positive direction, too.

(September 10, 2003) In the PV tool, when the user elected to run the base case to completion, an access violation would sometimes occur. This was due to the fact that Simulator would continue to try to finalize the results of all scenarios, not just the base case. Simulator has been modified to consider the results only of the base case once the PV study has progressed to the point where only the base case should be considered.

(September 10, 2003) In the PV tool, the critical state of contingencies were being saved to the old PVS format in addition to the full PWB format. Support for the PVS format was discontinued after version 8, so this activity should have been removed. The code has been changed to skip saving the system state to PVS format.

(September 10, 2003) Modifications were made to the QV curve tool to allow a step size of 0.0001 per unit.

(September 25, 2003) Fixed occasional bug which would make the specification of the number of limiting cases to determine in the PV curve disabled.

(October 6, 2003) Fixed a bug which would occur when choosing to "Use Initial Voltage as VMax" in the QV curve tool. This would cause the first bus's QV curve to be calculated correctly, but all subsequent QV curves to be using an artificially low Vmax value. This usually ended up in an unsolvable QV curve.

(December 18, 2003) Modified to handle situations correctly when a contingency takes a bus out of service in the QV curves tool. This was causing a bug which result in subsequent QV curve traces to fail.

Fault Analysis

(September 10, 2003) Fixed an error in the line-to-line fault calculation which would only occur if you specified a generator or load zero-sequence impedance of zero.

(November 20, 2003) Grounded wye to Ungrounded Wye transformers were being included in the zero sequence admittance matrix. This was incorrect and has been fixed.

(November 20, 2003) Simulator was not scaling the fault to ground impedance by 3 for the zero sequence network. This has been fixed.

(January 29, 2004) Fixed bug which occurred for generators whose MVA base was zero.

Modifications to Data Objects in Simulator

(February 28, 2003) Interfaces in Simulator can contain contingency element (Line Open and Line Close actions). Previously these elements were only utilized in the PTDF calculation (turning them into OTDF calculations) and the ATC tool in Simulator. When one looked at the "Flow" on an interface it will still only show the sum of the flow on the monitored elements in the interface. Simulator has been optimized now so that it calculates the "contingent" flows on these interfaces during each power flow solution thereby allowing us to display the correct flows.

(April 11, 2003) Fixed an error which was causing Zones and Areas which had no buses in them to lose their name and settings such as the Shown setting for Area/Zone filters. This has been fixed.

(April 21, 2003) Modified the setting the Area Number or Zone Number of a load, generator, or shunt during Edit Mode so that it will auto-create a area or zone as appropriate.

(April 21, 2003) Fixed a bug in the calculation of an interface's MW loss. It was causing an access violation.

(September 10, 2003) The code was set to ignore blank entries when the user left the "all labels" field blank. Now, the code no longer ignores it but instead frees the object's list of labels. This allows the user to remove all labels from an object simply by blanking out its “all labels” field.

(September 10, 2003) Modified bus renumbering routine to automatically update AC bus number references for multi-terminal DC lines.

(September 10, 2003) Fixed bug where manually changing the AC bus number of an existing MTDC converter always resulted in a new converter being created instead of renumbering the existing converter

(September 10, 2003) Fixed error in assigning losses when multi-section lines spanned two areas. Now the areas of the intermediate buses are reassigned according to the metered end of a multi-section line.

(September 10, 2003) Fixed bug with saving the default fields from Default Drawing Values to the windows registry. Previously if you had chosen one of the specific fields, the field would not be properly saved.

(November 20, 2003) Fixed intermittent error in determining the type (rectifier or inverter) of the voltage controlling converter in a multi-terminal DC transmission line.

(December 18, 2003) Added a new field available on bus records called "Throughflow MW and Mvar" which show a measure of the total amount of power being processed through the bus.

(January 29, 2004) Modified to not allow owner numbers of value zero.

User Interface Dialogs

(February 21, 2003) When using the Edit Mode Zone Dialog to move buses between zones, the zone of generation and shunts would sometimes not move along with the bus specification. This has been fixed.

(February 21, 2003) When inserting a direction on the PTDF dialog (after choosing multiple directions for the PTDF type), if a user forgot to give the direction a name, the dialog would notify them of that and then close without creating the direction. The dialog will still give an error asking for a name, but no longer closes.

(February 28, 2003) When typing in numbers to the buyer or seller drop down boxes on the PTDF dialog, Simulator would not always register the change in the buyer or seller. This has been fixed.

(February 28, 2003) When using the Select by Criteria Dialog, the section of generator objects and generator fields did not always work properly.

(March 13, 2003) When using the System Scaling options with the "Enforce ACE" option checked, even areas which were not scaled would have their generation moved. This bug has been fixed.

(March 25, 2003) Modified to allow the optional saving of one-line diagrams when saving a case.

(April 23, 2003) When trying to find the shortest path between two buses for which no path existed, then the program would fail. This has been fixed so that it simply returns the result "no path found"

(April 23, 2003) The Facility Analysis dialog was improved to return a more detailed response when no path exists between the facility and external node.

(May 7, 2003) When looking for branches, the Find dialog shows a list of buses on the left and then a list of the buses connected to that bus on the right. A right-click option has been added so that the "far buses" connected to the selected bus can also show multi-section line terminals in addition to the directly connected bus.

(May 13, 2003) The Edit Mode Generator dialog was not registering changes made to the "Fuel Type". This has been fixed.

(May 31, 2003) Fixed a nuisance bug which resulted in random access violations when closing the Switched Shunt Dialog after opening it by right-clicking on a switched shunt object in the Bus View Oneline.

(September 10, 2003) There was a problem when right-clicking on an interface list and choosing to load the “NERC book of flowgates”. This only worked when called from the Case Information, Interfaces dialog. All other dialogs which contained a list of interfaces would cause an access violation when calling this. This has been fixed.

(September 10, 2003) Forced the Limit Monitoring Settings dialog to show up in front of the OPF constraint options. Previously it was hidden behind this dialog.

(September 10, 2003) Modified switched shunt dialogs to show the regulated bus voltage with 4 decimal points.

(September 10, 2003) Fixed a bug in the quick power flow list. Generators with two character IDs had their ID clipped to one character.

(September 10, 2003) In the System Scaling dialog when choosing to “Scale Generator to keep ACE constant”, and “Enforce Generator MW limits”, Simulator would always attempt to change the generation in every area by the same amount that the load changed, while at the same time ensuring that the generator MW limits are honored. Previously when an area’s load was not changed, the scaling would still try to enforce generator MW limits. If an area had generators outside their limits, then they would be moved. The scaling has been modified so that areas which have no change in load will never be modified.

(September 23, 2003) Fixed a bug when right-clicking on the bus records display to bring up the bus dialog. Sometimes this would result in an access violation.

(September 25, 2003) Modified the System Scaling dialog and routines so that the totals listed for loads only includes in-service load. Previously the totals would also include load that was open.

(October 21, 2003) The ability to choose to "toggle all" on the Split Bus dialog for moving equipment was not working. This has been fixed.

(February 26, 2004) Modified the transformer correction table dialog so that when toggling to a correction table which was not utilized by any transformers, it would properly refresh the list of transformers and show that none used the table.