1

WECC Modeling and Validation Work Group

Report to TSSAugust 2007

Dmitry KosterevBonneville Power Administration

Transmission Planning

WECC Modeling and Validation Work Group 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

3

Load Modeling Task ForceLoad Modeling Task Force

4

Load ModelingLoad 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 StructureLoad Model Structure

Static

MTransformer FeederEquivalent

Load ModelComponents

M

M

Proposed

Today

Static

M115-kV230-kV

115-kV230-kV

20%

M

6

Load Model StructureLoad 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 ModelsSingle-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 ModelsSingle-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 DataLoad 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 DataLoad 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 FractionsLoad 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 FractionsLoad Component Model Fractions

Large Office RetailGrocery Residential

C1 C2 C5

COM RES

R1

SubstationTime, Date, Temp

… …kW kW kW kW

13

Load Model DataLoad Model Datacmpldw 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

Motor Ddata

Motor Cdata

Motor Bdata

Motor Adata

Static ZIP

Fractions

Tx data

FeederID, Base

14

Load Model Data ToolLoad Model Data Tool

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Load Model Validation StudiesLoad 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

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Load Model StudiesLoad Model Studies

Actual Event

17

Load Model StudiesLoad Model Studies

Simulations done by Robert Tucker, SCE

Explicit load representation

“Performance” model for 1phase A/C units

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Load Model StudiesLoad Model Studies

3-hase faultHassayampa – Palo VerdeNormal clearing

Explicit load representationBPA “Performance” A/C model

Baseline simulation20% of a/c tripped by UV relay30% of a/c tripped by UV relay60% of a/c tripped by UV relay

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Load Model for Post-Transient Load Model for Post-Transient StudiesStudies

• 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

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Non-Symmetric SimulationsNon-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

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Something to Think AboutSomething to Think About

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.05

1.10

0 5 10 15 20 25 30Seconds

Vo

ltag

e (p

u)

30 seconds

75%

100%

Criteria

Reality

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Generating Unit Modeling Generating Unit Modeling and Validationand Validation

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Generating Unit ModelingGenerating Unit Modeling

• Generating Unit Model Validation Standard

• Model Validation Using Disturbance

Recordings

• Generator Saturation Models

• USBR Governor Model

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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

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Generating Unit Model ValidationGenerating 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

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Generator Saturation ModelingGenerator 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

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Generator Saturation ModelingGenerator Saturation Modeling

Open Circuit Saturation Curve

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.25 0.5 0.75 1 1.25 1.5

Field Current [Per Unit]

Sta

tor

Vo

lta

ge

[P

er

Un

it]

V(pu)

V-sim(pu)

V-airg(pu)

V-curve at 0 MW

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 0.5 1 1.5 2 2.5

Field Current [PU]

Ab

so

lute

Re

ac

tiv

e P

ow

er

[PU

]

Ifd-rec

Ifd-sim

Gentpf model

V-curve at 145 MW

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

1 1.5 2 2.5

Field Current [pu]

Ab

so

lute

Re

ac

tiv

e P

ow

er

[pu

]

Ifd-rec

Ifd-sim

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Generator Saturation ModelingGenerator 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

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Generator Saturation ModelingGenerator 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.

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Generator Saturation ModelingGenerator 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

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Generator Saturation ModelingGenerator Saturation Modeling

Palo Verde reactive power on June 14, 2004

Actual

Gentpf

Genrou

Gentpj (modified Gentpf)

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Wind Farm ModelingWind Farm Modeling

Abe Ellis, PNM Abe Ellis, PNM Juan Sanchez-Gasca, GE Juan Sanchez-Gasca, GE Bill Price, GEBill Price, GEYuri Kazachkov, Siemens PTIYuri Kazachkov, Siemens PTIEduard Muljadi, NRELEduard Muljadi, NREL

33

Wind Farm Powerflow ModelWind Farm Powerflow Model

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

Equivalent WTGMain transformer

Equivalent feeder

Equivalent pad-mounted transformer

Turbine-level power factor correction shunt capacitor, if any

POI

Plant-level reactive compensation.

Could be static and/or dynamicCollector station

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Dynamic Model SpecificationsDynamic 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 ModelsProposed 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

generator

full power

PlantFeeders

actodc

dctoac

generator

partia l power

PlantFeeders

actodc

dctoac

generator

Slip poweras heat loss

PlantFeeders

PF controlcapacitor s

actodc

generator

PlantFeeders

PF controlcapacitor s

Type 1 Type 2 Type 3 Type 4

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PSLF WTG Dynamic ModelsPSLF WTG Dynamic Models Type 1 Type 2 Type 3 Type 4

Model Type Existing Generic Existing Generic Detailed Generic Detailed GenericGE 1.5 GE 2.x

Generator genind wt1g genwri wt2g gewtg wt3g gewtg wt4g

Excitation Controller exwtg1 wt2e exwtge wt3e ewtgfc wt4e

Turbine wndtrb wt1t wndtrb wt2t wndtge[1] wt3t wndtge [1] wt4t

Pitch Controller wt1p wt2p wt3p wt4p

[1] Includes pitch controller

New models

Undergoing verification tests (PSLF vs. EMTP)

Under development

Under development

37

Power Electronic DevisesPower Electronic Devises

Bharat Bhargava, SCEBharat Bhargava, SCE

38

Power Electronic DevicesPower 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 ModelsStatic VAR Systems: Powerflow Models

1. Represent the device as a shunt for SVCs and as a current injection in STATCOMs

2. Model droop in power flows (post-transient ?)

3.3. Modeling coordinated shunt switching and ULTCs in power Modeling coordinated shunt switching and ULTCs in power flowsflows

4.4. Model slow-susceptance regulatorModel slow-susceptance regulator

5.5. Dead band representationDead band representation

6.6. Model reactive power control Model reactive power control

7.7. High-side or low-side of coupling transformer representationHigh-side or low-side of coupling transformer representation

8.8. Seamless transition of sav case from power flow to dynamicsSeamless transition of sav case from power flow to dynamics

40

Static VAR Systems: Dynamic ModelsStatic VAR Systems: Dynamic Models1. Voltage cutout (under / over voltage performance)

2. Integrated fast-switched capacitor banks

3. Coordinated control with local and remote capacitor banks, shunt reactors, and LTCs

4. High-side or low-side of coupling transformer representation

5. Default set of parameters for different types of SVC and STATCOM

6. TCR based SVS, STATCOM based SVS or TSC/TSR based SVS

7. Control modes ( Main voltage regulator, Slow-susceptance, Deadband control, Non-linear droop, MSC coordinated switching, Hysteresis )

41

Static VAR Systems SurveyStatic VAR Systems Survey1. Was sent out in May

2. Received information on 12 SVCs by June 30, 2007

3. Donald Davis has compiled the list and a summary has been provided to the SVC TF members

4. SVC TF will be contacting some Companies individually as the responses have not been received from them

5. SVC TF will be updating the information and a summary report will be prepared

6. 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 - CommentsStatic 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 PTIPDCI 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 ValidationPDCI 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 ValidationDisturbance Validation

Les Pereira, NCPALes Pereira, NCPA

46

West-Wide System ModelWest-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 ?Questions ?Comments ?Comments ?

Suggestions ?Suggestions ?