Presentation on theme: "Reading a GE PSLF *.epc into PWS"— Presentation transcript:
1Reading a GE PSLF *.epc into PWS Tracy RolstadAvista System PlanningWECC PWSUG, 14 March 2012We are going to discuss how a GE *.epc power flow case should be read into PWS, what to watch out for, how the results are the same, and why the results might be somewhat different. Both programs yield “correct” answers…any notable differences should certainly be examined with an eye towards modeling “error budget.”
2Open Case, Select <GE EPC format (with options)> Make use of the proper epc read form to understand what you are doing.
3What Options (these are defaults)? Matching up options…understand what ignoring the generators with less than 2 MVAr bandwidth does across the case. Is this really the right thing to do? Note that GE doesn’t enjoy very tight bandwidths whereas PWS will solve fine.
4Start with GE Nothing is sacred about the GE defaults. Change them! Solve the case, multiple times…GE uses an estimated mismatchSo, solve in GE three times or soSave the solved case as an *.epc fileIf you have GE you should play around with the settings and see how GE does with different settings. Read how the recommended PARM settings are NOT the same as the WECC default solution settings. Note that at least the GE *.epc file tells you how a case was solved. The PTI *.raw format has no provision for that.
5Read into PWS and Solve Read in case, note mismatches, understand them Lock all controls down, solve in PWS (set gen voltage control)Check Interface flows against GE…GE allows double counting the same linePWS does NOT allow double countingNote Mismatch resolution in logPWS Zero Impedance Line is very, very smallGE uses X= ( kV)PWS uses X= ( kV)
6Mismatch TableWhy are these mismatches there? What does this all mean? Guesses?
7Mismatches in State Variable View Note the lack of arrows in the state variable view…thoughts?
8Mismatches in Input Data View Try the input data view?
9Bug or feature. When should software NOT do what you tell it Bug or feature? When should software NOT do what you tell it? It is fair to assume that someone wanted to add the same line twice…but PWS doesn’t because we understand how WECC intends to represent the Path Rating Catalog. There is NO right way to implement the software, but there is certainly a right way to submit the data.
10After Fixing GE Bface Error Errors after removing extra BFACE entryTotal MW Error (i.e. sum) = -19.5Max MW Error = 3.7 (North to South California, Path 24)Min MW Error = -4After fixing the error we get really about the same answer
11Read the Log, Understand and Take Action See the IID to SCE entry
12Read into PWS and Solve Unlock all controls, solve in PWS Check log for AGC movementMay need to “Zero out transactions”If GE transaction table isn’t manually updated by WECC staffCheck Interface flows against GE…Should get pretty much the same answer on path flowsCheck for multiple islands
14Voltage Control for Generators Allocate across buses using the user-specified remote regulation percentages. This option is what is used by default and most closely matches the sharing seen in RAW files.Allocate so all generators are at same relative point in their [min .. max] var range. This option most closely matches the sharing seen in a few EMS solutions PowerWorld has seen.Allocate across buses using the SUM OF user-specified remote regulation percentages. This option most closely matches the sharing seen in EPC files.Note: Generators at the same bus always allocate vars so they are at the same relative point in their [min…max] range
15Var SharingNote what is going on here with the same setpoint. At the highside bus the Var injection is almost exactly the same
16Comparing PWS to GE VAr “Answer” Which method do YOU think is right.
17Check Case Summary and Slack Bus Generator QuantityGEPWSLoad MWGen MWLosses MW6269.86263.5Buses count1820518585Load MVAr(t_area)Load MVAr*Slack MW538.0543.01The TABR report t_area seems to have a bug. Never trust summation tools in software without doing a basic check once in awhile.* Summed directly from load record
18Look for Places to Establish “Test Flows” Cut and paste depiction of PWS flows on a GE scan diagram
19Check Performance in Contingent Environment GE pasted on a PWS diagram
20Participation Factor Note (Added Post Meeting) During the second WECC PWS Users Group we noticed that PWS was parsing the Gen MVA field of the *.epc file and setting Participation Factors on that field. In many cases this value is merely set to 100 MVA (for example the large units located in the third power house at Grand Coulee).Users should be alert to this behavior and manually set Participation Factors to be based on PmaxTypically setting Participation Factors to Pmax is the desired setting for dispatching make-up power during contingency analysis, etc.
22Questions?PWS will provide similar, but not exact results when compared to GE (or PTI)Heuristics abound…What is “right?” Good reason to use multiple toolsVAr dispatch of generation has an impact, especially on the initialization point for transient stabilityZero impedance line representations have some impactRecommendationPresume that both software provide reasonably accurate possible solution pointsTake five minutes to understand the case read!!!In general, going through this sort of procedure should let users verify that PWS and GE produce substantially the same results in Power Flow. Such an activity is being proposed as part of the certification process of software. Note that if you stress the case you are likely to seem MORE differences in the solved cases…
23Dump truck providing smart grid to a home in Othello, WA…losses should be low if your alarm clock operates at 13.2 kV