WECC Modeling and Validation Work Group

1. WECC Modeling and Validation Work Group Report to TSS August 2007 Dmitry Kosterev Bonneville Power Administration Transmission Planning

2. MVWG Workload • Load Modeling • Generating Unit Model Validation • Wind Farm Modeling • Modeling of Power Electronics Devices • Static VAR Systems • HVDC Systems • Disturbance Analysis and System Performance Validation WECC Modeling and Validation Work Group

3. Load Modeling Task Force

4. Load Modeling • Load Model Structure • Composite load model in production program • Explicit load representation • Load Model Data • System Studies: • Sensitivity, Validation, System Performance • New Research Items • Load models for post-transient voltage stability • Simulation of single-phase loads under un-balanced disturbances

5. Load Model Structure Today M 20% 115-kV 230-kV Static Load Model Components M Proposed Transformer Feeder Equivalent M 115-kV 230-kV M M Static

6. Load Model Structure • LMTF developed EPCL routines for explicit load representation in PSLF program • WECC developed load model specifications • WECC Composite Load Model is implemented in GE PSLF 16.1 (no single-phase motor model or partial load tripping by UVLS / UFLS ). • LMTF tested model performance: • Simple test system • WECC-wide representation • Single-Phase Motor Model is under development • Single-phase motor model will be in PSLF 17.? : • part of composite load model • as a stand-alone model

7. Single-Phase Motor Models • SCE, BPA, APS/EPRI tested a large number of residential single-phase air-conditioner motors • There is a difference between equipment-level and grid-level models • CEC funded development of a mathematical model for single-phase motors – Bernie Lesieutre (LBNL) is the lead • John Undrill developed a “motorc” model in PSLF based on machine physical principles • John Undrill and Bernie Lesieutre are reconciling the amount of detail that should go into grid-level PSLF model

8. Single-Phase Motor Models • Single-phase motor model will include: • Compressor motor model • “motorc” is the preferred choice • Performance model (static) • Thermal protection model • Under-Voltage relay model (SCE solution) • Control and contactor model

9. Load Model Data • Load model data records include: • Distribution equivalent model data • Fractions of total load assigned to each load model component • Model data for load model components (e.g. motor inertia, driven load, electrical data, etc)

10. Load Component Model Data • Models and model data for various electrical end-uses • equipment testing • Single-phase air-conditioners • Lights, Electronics • Large Fans • Large Pumps • Variable-Frequency Drives • Residential Appliances • manufacturer’s data analysis • Model and data aggregation: • separate end-uses that exhibit different behavior • aggregate model data for end-uses within the same group • Map electric end-users to model components

11. Load Component Model Fractions • The most challenging part of model data • High level of uncertainty and variability • Shown to have significant impact on study results • Short-term objective: • Get reasonable region-wide estimates for heavy summer loads • Understand sensitivities • Contact WECC Load and Resource Group • PNNL work under CEC Contract

12. Load Component Model Fractions Substation Time, Date, Temp COM RES C1 C2 C5 R1 … … kW kW kW kW Large Office Grocery Retail Residential

13. Load Model Data ID, Base Feeder Tx data Fractions cmpldw 11 "LOAD-1 " 115.00 "A " : #9 mva=110 "Bss" 0 / "Rfdr" 0.024 "Xfdr" 0.03 "Fb" 0.749/ "Xxf" 0.08 "TfixHS" 1 "TfixLS" 1 "LTC" 1 "Tmin" 0.9 "Tmax" 1.1 "step" 0.00625 / "Vmin" 1.02 "Vmax" 1.035 "Tdel" 30 "Ttap" 5 "Rcomp" 0 "Xcomp" 0 / "Fma" 0.2 "Fmb" 0.15 "Fmc" 0.2 "Fmd" 0.25 "Fdl" 0 / "Pfs" 0.98 "P1e" 2 "P1c" 0 "P2e" 1 "P2c" 1 "Pfreq" 1 / "Q1e" 2 "Q1c" 1 "Q2e" 1 "Q2c" 0 "Qfreq" -1 / "MtpA" 3 "LfmA" 0.85 "RsA" 0.02 "LsA" 2.5 "LpA" 0.2 "LppA" 0.15 "TpoA" 0.44 "TppoA" 0.0026 / "HA" 0.3 "atrqA" 0 "btrqA" 0 "dtrqA" 1 "etrqA" 2 / "Vtr1A" 0.7 "Ttr1A" 9999 "Ftr1A" 0.5 "Vrc1A" 1 "Trc1A" 9999 / "Vtr2A" 0.65 "Ttr2A" 9999 "Ftr2A" 0.5 "Vrc2A" 1 "Trc2A" 9999 / "MtpB" 3 "LfmB" 0.85 "RsB" 0.02 "LsB" 2.5 "LpB" 0.2 "LppB" 0.15 "TpoB" 0.44 "TppoB" 0.0026 / "HB" 1 "atrqB" 0 "btrqB" 0 "dtrqB" 1 "etrqB" 2 / "Vtr1B" 0.7 "Ttr1B" 9999 "Ftr1B" 1 "Vrc1B" 1 "Trc1B" 9999 / "Vtr2B" 0.8 "Ttr2B" 9999 "Ftr2B" 1 "Vrc2B" 1 "Trc2B" 9999 / "MtpC" 3 "LfmC" 0.85 "RsC" 0.02 "LsC" 2.5 "LpC" 0.2 "LppC" 0.15 "TpoC" 0.44 "TppoC" 0.0026 / "HC" 0.3 "atrqC" 0 "btrqC" 0 "dtrqC" 1 "etrqC" 2 / "Vtr1C" 0.7 "Ttr1C" 9999 "Ftr1C" 1 "Vrc1C" 1 "Trc1C" 9999 / "Vtr2C" 0.8 "Ttr2C" 9999 "Ftr2C" 1 "Vrc2C" 1 "Trc2C" 9999 / "MtpD" 3 "LfmD" 0.85 "RsD" 0.03 "LsD" 1.8 "LpD" 0.2 "LppD" 0.15 "TpoD" 0.2 "TppoD" 0.0026 / "HD" 0.07 "atrqD" 0 "btrqD" 0 "dtrqD" 1 "etrqD" 2 / "Vtr1D" 0.7 "Ttr1D" 9999 "Ftr1D" 1 "Vrc1D" 1 "Trc1D" 9999 / "Vtr2D" 0.8 "Ttr2D" 9999 "Ftr2D" 1 "Vrc2D" 1 "Trc2D" 9999 Static ZIP Motor A data Motor B data Motor C data Motor D data

14. Load Model Data Tool

15. Load Model Validation Studies • Challenges of load model validation: • Load composition is constantly changing • Large disturbances may not occur during loading conditions of interest • Most disturbances are not large enough to extrapolate the load behavior for most planned for disturbances • Lack of dynamic measurements • Validate the load behavior in principle rather than curve-fitting a particular disturbance event

16. Load Model Studies Actual Event

17. Load Model Studies Explicit load representation “Performance” model for 1phase A/C units Simulations done by Robert Tucker, SCE

18. Load Model Studies 3-hase fault Hassayampa – Palo Verde Normal clearing Explicit load representation BPA “Performance” A/C model Baseline simulation 20% of a/c tripped by UV relay 30% of a/c tripped by UV relay 60% of a/c tripped by UV relay

19. Load Model for Post-Transient Studies • How good is our present assumption of constant load P and Q ? • How is reactive margin affected with assumptions of voltage sensitivity of loads? • Work in Progress

20. Non-Symmetric Simulations • Present transient stability programs: • designed to study angular stability of synchronous generators • assume symmetric loads and generators • One-line system representation • assume balanced post-fault system • There is a growing need to study dynamic voltage stability events: • Such events are greatly influenced by load behavior • Can be initiated by non-symmetric faults, with non-symmetry in post-fault conditions (e.g. single-phase air-conditioners are stalling in the faulted phase initially) • Existing simulation methods may not capture the severity of non-symmetric disturbances • Work in Progress, request CEC to fund research

21. Something to Think About Criteria 100% Reality 75% 30 seconds

22. Generating Unit Modeling and Validation

23. Generating Unit Modeling • Generating Unit Model Validation Standard • Model Validation Using Disturbance Recordings • Generator Saturation Models • USBR Governor Model

24. Generating Unit Model Validation • WECC will continue operating under the existing Policy, approved in July 2006 • WECC will not pursue development of a regional Standard • WECC will make sure that its expertise and 10+ years of experience are represented in the development of the national standard: • Donald Davies, Shawn Patterson, Les Pereira, John Undrill, Abe Ellis, Baj Agrawal and Dmitry Kosterev

25. Generating Unit Model Validation • BPA developed an EPCL program for model validation using disturbance measurements at generating facility POI • The tool is being tested and manuals are developed

26. Generator Saturation Modeling • Long-known deficient area of synchronous machine dynamic modeling • Present assumptions are believed to be more conservative from angular stability standpoint • Present assumptions produce much more optimistic reactive power for a given field current when machine is over-excited at full load • John Undrill, BPA, USBR collected test data from a number: • Open circuit magnetization curve • V-curve at no-load, partial load, full load • Current interruption tests

27. Generator Saturation Modeling Gentpf model

28. Generator Saturation Modeling • Both parabolic and exponential saturation models are OK, with exponential having a slightly better fit • Most model validation tests (current interruption) are not affected by saturation modeling

29. Generator Saturation Modeling Explanation from John Undrill: • The 'standard' models (gensal, gentpf, genrou) all assume that saturation is a function of an internal flux linkage. These models assume that the effect of saturation on the voltages induced throughout the generator are the same when stator current is at normal operational values as at zero real power output. • The “gentpj” model recognizes that the leakage flux components induced in the stator teeth by high stator currents can increase the reluctance of the magnetic circuit significantly above the level seen on open circuit. • That the reluctance of the magnetic circuit is affected by leakage flux effects of stator current has long been recognized in generator design practice but has been ignored in the generator models used in grid-level simulations.

30. Generator Saturation Modeling Recommendation from John Undrill: • The use of the GENSAL model in the PSLF and PSS/E programs should be discontinued. References to the GENSAL model should be replaced by references to the GENTPF with the new saturation model. • The model saturation is implemented within the present GENTPF model. • Saturation parameter “Kis” is added at the end of GENTPF data record. Typical Kis = 0.08 to 0.15 and can be estimated from reactive limit tests. • The GENTPF with new saturation model is available in PSLF 17.0

31. Generator Saturation Modeling Palo Verde reactive power on June 14, 2004 Actual Gentpf Genrou Gentpj (modified Gentpf)

32. Wind Farm Modeling Abe Ellis, PNM Juan Sanchez-Gasca, GE Bill Price, GEYuri Kazachkov, Siemens PTIEduard Muljadi, NREL

33. Wind Farm Powerflow Model Equivalent WTG Main transformer Equivalent pad-mounted transformer POI Equivalent feeder Plant-level reactive compensation. Could be static and/or dynamic Turbine-level power factor correction shunt capacitor, if any Collector station Wind power plant capacity = 100 MW Substation transformer: RTX = 0.0, XTX = 0.10 to 0.12 pu Collector system (34.5 kV): Ze = (0.015 + j 0.025) p.u. with Be = 0.01 p.u. Pad mount transformer: Zte = (0.0 + j 0.05) p.u. NREL has a tool for equivalencing collector system

34. Dynamic Model Specifications • WTG modeling detail • Effects of grid disturbances, not wind disturbances. • P, Q, V response, not internal details. • Simplified aerodynamic model (no Cp curves) • One-mass or two-mass mechanical model • Separate models for shunt compensation and protection • LVRT trip levels, not internal details. • Initialization • P and Q from power flow • If P = rated, initialize at specified wind speed > rated

35. Proposed Standard Models • Four basic topologies based on grid interface • Type 1 – conventional induction generator • Type 2 – wound rotor induction generator with variable rotor resistance • Type 3 – doubly-fed induction generator (APPROVED) • Type 4 – full converter interface Type 1 Type 2 Type 3 Type 4 Plant Feeders ac dc generator to to dc ac full power

36. PSLF WTG Dynamic Models Under development New models Undergoing verification tests (PSLF vs. EMTP) Under development

37. Power Electronic DevisesBharat Bhargava, SCE

38. Power Electronic Devices • What happened to NERC MOD-028 “Models and Data for Transmission Power Electronic Control Devices” ? – chopped out • WECC SVC Modeling Task Force is developing powerflow and dynamic models of Static VAR Systems. • WECC MVWG developed HVDC Modeling Requirements in 1988. The requirements are currently being reviewed and updated.

39. Static VAR Systems: Powerflow Models • Represent the device as a shunt for SVCs and as a current injection in STATCOMs • Model droop in power flows (post-transient ?) • Modeling coordinated shunt switching and ULTCs in power flows • Model slow-susceptance regulator • Dead band representation • Model reactive power control • High-side or low-side of coupling transformer representation • Seamless transition of sav case from power flow to dynamics

40. Static VAR Systems: Dynamic Models • Voltage cutout (under / over voltage performance) • Integrated fast-switched capacitor banks • Coordinated control with local and remote capacitor banks, shunt reactors, and LTCs • High-side or low-side of coupling transformer representation • Default set of parameters for different types of SVC and STATCOM • TCR based SVS, STATCOM based SVS or TSC/TSR based SVS • Control modes ( Main voltage regulator, Slow-susceptance, Deadband control, Non-linear droop, MSC coordinated switching, Hysteresis )

41. Static VAR Systems Survey • Was sent out in May • Received information on 12 SVCs by June 30, 2007 • Donald Davis has compiled the list and a summary has been provided to the SVC TF members • SVC TF will be contacting some Companies individually as the responses have not been received from them • SVC TF will be updating the information and a summary report will be prepared • Some Information in the survey is being treated as confidential information and the survey as such is not being released for general use.

42. Static VAR Systems - Comments • Prioritize efforts to focus on what is critical for grid simulations • Avoid excessive and unnecessary control detail • Capture essential controls affecting system performance • Develop SVC monitoring requirements • Develop SVC model validation requirements and guidelines

43. PDCI Model – Siemens PTI • Siemens PTI implemented PDCI model in PSS™E • Load Flow: • In PSS™E load flow, each pole of the PDCI is represented as a 3-terminal HVDC. • Because of the difference between multi-terminal HVDC data records in PSS™E and PSLF, PDCI power flow data had to be manually inserted from PSLF to PSS™E. • Different data for north to south versus south to north flows on the PDCI must be used.  • Dynamics: • When developing the latest PSS™E dynamic simulation model for the present PDCI arrangement the PSLF epcl (pseudo code) programs have been used, along with the original ABB block diagrams. • Two PSS™E dynamic simulation models have been developed: PDCINS for the PDCI power flow from North to South and PDCISN for the opposite direction of the power flow. • The data sets for both PSS™E dynamic simulation models for PDCI are exactly the same as for the PSLF model.

44. PDCI Model Validation • PSS™E models were tested and successfully validated against results of testing the respective PSLF models. • Model Validation against reality: • SCE, LADWP are installing monitors to monitor voltages, frequency, real and reactive power at the Sylmar terminal • BPA already has monitors at Celilo • Model validation tests are planned • Feasibility of model validation against disturbances is studied by PNNL

45. Disturbance ValidationLes Pereira, NCPA

46. West-Wide System Model • MVWG supports development of West-Wide System Model • Accurate powerflow snapshot of system conditions prior to a disturbance is necessary for model validation studies • BPA is mapping state estimator solution from July 24 2006 heat-wave onto WECC base case • Need to make sure that State Estimator solution is sufficiently good for voltage and transient stability studies

47. Questions ?Comments ?Suggestions ?