PowerWorld Case Validation John Gross – Avista SRWG Member March 9-10, 2017 Western Electricity Coordinating Council

Western Electricity Coordinating Council 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 Western Electricity Coordinating Council

Western Electricity Coordinating Council 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. Western Electricity Coordinating Council

Opening epc file in PowerWorld Steady State Data Opening epc file in PowerWorld Western Electricity Coordinating Council

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 Western Electricity Coordinating Council

Western Electricity Coordinating Council Balance Parallel LTC Before solution After solution Not balanced Balanced Western Electricity Coordinating Council

Western Electricity Coordinating Council Transformer LTC Tap Before solution After solution Western Electricity Coordinating Council

Western Electricity Coordinating Council 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. Western Electricity Coordinating Council

Bus Voltage and Angle Difference Differences mostly from LTC tap positions changing. Western Electricity Coordinating Council

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! Western Electricity Coordinating Council

Generator MVAr DIfference Difference from MVAr sharing across multiple units regulating same bus Western Electricity Coordinating Council

Western Electricity Coordinating Council 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 < 0.0029), bypassed elements, and transformers Western Electricity Coordinating Council

Area Tieline MW Difference LTC Tap change Before After Western Electricity Coordinating Council

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 Western Electricity Coordinating Council

Using dyd data in PowerWorld Dynamic Data Using dyd data in PowerWorld Western Electricity Coordinating Council

Western Electricity Coordinating Council 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 Western Electricity Coordinating Council

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 Western Electricity Coordinating Council

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 Western Electricity Coordinating Council

Western Electricity Coordinating Council No Disturbance I think its “flat” Western Electricity Coordinating Council

Western Electricity Coordinating Council 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) Western Electricity Coordinating Council

Western Electricity Coordinating Council 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 Western Electricity Coordinating Council

Western Electricity Coordinating Council Solution Tolerance 0.1 MW Tolerance 0.005 MW Tolerance Plots may look “spiky” when scale is small New default is 0.01 MW Western Electricity Coordinating Council

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 Western Electricity Coordinating Council

Western Electricity Coordinating Council 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 Western Electricity Coordinating Council

Western Electricity Coordinating Council 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 www.PowerWorld.com Western Electricity Coordinating Council