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 Load Model Data System Studies:
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 Proposed M Static M M M M Static 20% 115-kV
Components
Proposed M
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 Static ZIP Motor A
cmpldw "LOAD-1 " "A " : #9 mva=110 "Bss" 0 /
"Rfdr" "Xfdr" 0.03 "Fb" 0.749/
"Xxf" 0.08 "TfixHS" 1 "TfixLS" 1 "LTC" 1 "Tmin" "Tmax" 1.1 "step" /
"Vmin" "Vmax" "Tdel" 30 "Ttap" 5 "Rcomp" 0 "Xcomp" 0 /
"Fma" "Fmb" 0.15 "Fmc" 0.2 "Fmd" "Fdl" 0 /
"Pfs" "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" "TpoA" 0.44 "TppoA" /
"HA" "atrqA" 0 "btrqA" 0 "dtrqA" 1 "etrqA" 2 /
"Vtr1A" 0.7 "Ttr1A" "Ftr1A" 0.5 "Vrc1A" 1 "Trc1A" 9999 /
"Vtr2A" 0.65 "Ttr2A" "Ftr2A" 0.5 "Vrc2A" 1 "Trc2A" 9999 /
"MtpB" 3 "LfmB" 0.85 "RsB" 0.02 "LsB" 2.5 "LpB" 0.2 "LppB" "TpoB" 0.44 "TppoB" /
"HB" 1 "atrqB" 0 "btrqB" 0 "dtrqB" 1 "etrqB" 2 /
"Vtr1B" 0.7 "Ttr1B" "Ftr1B" 1 "Vrc1B" 1 "Trc1B" 9999 /
"Vtr2B" 0.8 "Ttr2B" "Ftr2B" 1 "Vrc2B" 1 "Trc2B" 9999 /
"MtpC" 3 "LfmC" 0.85 "RsC" 0.02 "LsC" 2.5 "LpC" 0.2 "LppC" "TpoC" 0.44 "TppoC" /
"HC" "atrqC" 0 "btrqC" 0 "dtrqC" 1 "etrqC" 2 /
"Vtr1C" 0.7 "Ttr1C" "Ftr1C" 1 "Vrc1C" 1 "Trc1C" 9999 /
"Vtr2C" 0.8 "Ttr2C" "Ftr2C" 1 "Vrc2C" 1 "Trc2C" 9999 /
"MtpD" 3 "LfmD" 0.85 "RsD" 0.03 "LsD" 1.8 "LpD" 0.2 "LppD" "TpoD" 0.2 "TppoD" /
"HD" "atrqD" 0 "btrqD" 0 "dtrqD" 1 "etrqD" 2 /
"Vtr1D" 0.7 "Ttr1D" "Ftr1D" 1 "Vrc1D" 1 "Trc1D" 9999 /
"Vtr2D" 0.8 "Ttr2D" "Ftr2D" 1 "Vrc2D" 1 "Trc2D" 9999
Feeder
Tx data
Fractions
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 Simulations done by Robert Tucker, SCE
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%
75%
Reality
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, GE Yuri Kazachkov, Siemens PTI Eduard 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 = ( 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 Devises Bharat 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 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 Validation Les 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 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 ?