1. PowerWorld Case Validation
John Gross – Avista
SRWG Member
March 9-10, 2017
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Introduction
WECC has started posting cases in PowerWorld format in addition to PSLF and PSSE
Process for data conversion and “approval” is still being developed
Following slides outline recent discoveries found through approval process
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Disclaimer
This presentation is not intended to identify or confirm potential software issues. The intent is to show differences observed when converting between software. Differences are not necessarily issues.
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4. Opening epc file in PowerWorld
Steady State Data
Opening epc file in PowerWorld
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5. Transformer LTC and shunt conflict
Solution should not be different because of this
Contingency analysis may give different results depending on solution options
Cause: data input is bad or not good
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Balance Parallel LTC
Before solution
After solution
Not balanced
Balanced
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Transformer LTC Tap
Before solution
After solution
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Phase Shifter control
Info: EPC files assume phase shifters are adjusted discretely using the step size between min/max phase. Option to model as a discrete control has been turned on.
Typical practice had been to allow discrete control in PowerWorld therefore causing solution to differ.
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9. Bus Voltage and Angle Difference
Differences mostly from LTC tap positions changing.
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10. Generator MW DIfference
Tielines with Loss Factor not equal to 1 or 0 are rounded to 1 or 0
Only Area slack generators moved slightly
Nothing else should move!
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11. Generator MVAr DIfference
Difference from MVAr sharing across multiple units regulating same bus
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Branch MW Difference
Ring with jumper
Other jumpers cause same issue
Stop using jumpers?
See DPM change request for Branch Type
Table excludes jumpers (X < ), bypassed elements, and transformers
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13. Area Tieline MW Difference
LTC Tap change
Before
After
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14. Steady State Conclusion
Using an epc file in PowerWorld yields acceptable results (many WECC members have been doing this for decades)
Improvements going forward
Evaluate Loss Factor must be 1 or 0
Stop using jumpers
Review voltage control setpoints for LTC and shunts
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15. Using dyd data in PowerWorld
Dynamic Data
Using dyd data in PowerWorld
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Reading dyd file
Several dynamic records with no matching steady state record
Records with not enough or too many parameters
Incorrect values
MVA base not equal to MVA base in steady state
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17. Validation (Fix Bad Data)
Mostly time constants not large enough relative to the time step
Error with REPC_A models not having monitored branches
Disable model – data submitter should fix
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18. Simulation Performance
Run Standard Disturbances listed in Annual Study Program Results Log (Link)
“No Disturbance” should be flat – how flat?
Speed delta < 0.001
EFD delta < 0.063
PG delta < 1
Other disturbances – just check for undamped oscillations
Composite load model is used in all simulations
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No Disturbance
I think its “flat”
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Time Step
Typical practice had been to use 0.5 cycles time step (why not? Its twice as fast as 0.25 cycles)
Auto correcting time constants to 4 times time step created unstable models – positive Eigenvalue
Going forward, stick with 0.25 cycles time step unless models are tuned to larger time step (new default is 0.25)
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Specific Models
There was an inconsistency in a specific load control model
One of the values was not being used as expected
“Issue” resolved – see LCFB1 documentation
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Solution Tolerance
0.1 MW Tolerance
0.005 MW Tolerance
Plots may look “spiky” when scale is small
New default is 0.01 MW
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23. Disturbances Meeting Criteria
For 2PV after 27 seconds check flat line criteria
Not meets criteria
Delta MW
Delta EFD
Meets criteria
Meets speed delta requirement
Does it need to? No…
Other disturbances meet criteria
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Dynamic Conclusion
Using the dyd data in PowerWorld yields acceptable results (many WECC members have been doing this for several years)
Stick with 0.25 cycles time step
Be aware of expectations with solution tolerance
Documentation on process may be beneficial
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Overall Conclusion
WECC should continue posting cases in PowerWorld format
Questionable data discovered in the process should be addressed by data submitters
Continue with BATF Modeling and Data Management Strategy suggested projects!
PowerWorld documentation is all on the website
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