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Load Modeling in WECCLoad Modeling in WECC
August 2009August 2009
Dmitry Kosterev
BPA
360-619-6836
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History Of Load Modeling in WECCHistory Of Load Modeling in WECC
1990s Constant current real, constant impedancereactive models connected to a transmission bus
1990s IEEE Task Force recommends dynamic load
modeling, however the recommendation does not gettraction in the industry
1996 BPA model validation study for August 10 1996
outage: Need for motor load modeling to represent oscillations and
voltage decline
2000 2001 WECC Interim Load Model: 20% of load is represented with induction motors
Tuned to match inter-area oscillations for August 10 1996 and
August 4, 2000 oscillation events Address critical operational issues for COI
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o
o
o o o o
o
o
o o o o
Simulations
instantaneous voltage recovery
This is what we thought would happen using interim load model
Motivation for Better Load ModelingMotivation for Better Load Modeling
30 seconds
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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 30
Seconds
Voltage
(pu
)
and this is what actually happened
Reality
30-second voltage recovery, 12 seconds below 80%
Motivation for Better Load ModelingMotivation for Better Load Modeling
30 seconds
100%
75%
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History Of Load Modeling in WECCHistory Of Load Modeling in WECC
Late 1980s Southern California Edison observed eventsof delayed voltage recovery attributed to stalling of
residential air-conditioners
1994 Florida Power published an IEEE paper on thesimilar experiences of delayed voltage recovery following
transmission faults
1997 SCE model validation study of Lugo event:
Need to represent a distribution equivalent
Need to have special models for air-conditioning load
2004-2005 Increased number of observed events of
delayed voltage recovery in Southern California, greaterneed to develop models to assess dynamic voltage stability
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WECC LMTF ApproachWECC LMTF Approach
WECC LMTF was formed in 2002
Component-based approach Understand load behavior over the wide range
of disturbances
Bottom-up model development
Top-down model validation
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WECC Composite Load ModelWECC Composite Load Model
2004-2005 Load Model prototype is developed and
extensively tested
Sequence of EPCL programs
2006 composite load model specifications are developed
2007 GE implemented version 0 of composite load modelin PSLF
2006-2008 residential AC testing and modeling research
is complete, models are developed, tested and validated 2008 LD1PAC model is approved
2009 composite load model development is completed in
PSLF program
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WECC LMTF Approval ProcessWECC LMTF Approval Process
Load Model Structure Approval
TOscan use composite load model data
Provide Guidance to Users on Composite LoadModel Data Sets
Generic data sets for load composition and load component data
Model Approval for WECC-wide planning andoperational studies
Composite load model to replace interim model in WECC planning andoperational studies
Review the need for WECC disturbance performance standard
Develop database management tools
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Load Model StructureLoad Model Structure
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CompositeComposite Load Model StructureLoad Model Structure
Electronic
M
M
M
115-kV
230-kV
Static
M
UVLS
UFLS
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Event Validation Studies with LD1PAC ModelEvent Validation Studies with LD1PAC Model
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Load Model DataLoad Model Data
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WECCWECCCompositeComposite Load ModelLoad Model
Electronic
M
Load Model
Composition
Data
M
M
115-kV
230-kV
Static
Load Component
Model
Data
Distribution Equivalent Data
UVLS and UFLS Data
M
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Load Model DataLoad Model Data
Load model data records include:
Distribution equivalent model data
PG&E developed methodology, proven to work, feel very confident Model data for load model components (e.g. motor inertia,
driven load, electrical data, etc)
Getting test data, develop better understanding of end-usecharacteristics
Motor protection and control remains least known
Fractions of total load assigned to each load model
component Finally we are getting reasonable estimates
UFLS and UVLS data
External to the model
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Modeling EndModeling End--Use ComponentsUse Components
Models and model data for various electrical end-uses
For Smaller End-Uses:
One test is worth a thousand of expert opinions
Single-phase air-conditioners
Lights, Electronics
Large Fans
Large Pumps
Variable-Frequency Drives
Residential Appliances
For Large End-Uses: manufacturers data analysis
IEEE Literature review
Model Aggregation Studies
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LBNL Electricity Use In California StudyLBNL Electricity Use In California Study
0
1
2
3
4
5
6
7
8
Res. - AirConditioning
Com'l. - AirConditioning
Com'l. -InteriorLighting
Com'l. - Other Res. -Miscellaneous
Res. -Refrigerator
Com'l. -Ventilation
Res. -Cooking
Res. - Dryer Com'l. -Refrigeration
0
5
10
15
20
25
30
35
Peak Demand
Annual Consumption
Source: CEC Demand Analysis Office
Peak Demand (GW) Consumption (TWh
Residential ACResidential AC
Commercial ACCommercial AC
LightingLighting
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< 1%4%< 1%5%
6%
26%
< 1%
9% 4%< 1%
11%
33%
< 1%
CoolingCooling
VentilationVentilation
RefrigerationRefrigeration
LightingLighting
CEC California Commercial EndCEC California Commercial End--Use SurveyUse Survey
Summer Peak LoadSummer Peak Load
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Component Model FractionsComponent Model Fractions
The most challenging part of model data
Sources of data:
California Energy Commission: 2006 Commercial End-Use Survey
LBNL Reports on Electricity Use in California
PNNL DOE2 building simulations and BPA ELCAP
PG&E methodology and tools for deriving bus-specific load
composition from billing data
BPA recorded / purchased building data
Rules of Association to map end users onto models
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LBNL: California Summer Peak Day LoadLBNL: California Summer Peak Day Load
0
10
20
30
40
50
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Residual ("Other" Area)
Res. - Air Conditioning
Com'l. - Air Conditioning
Com'l. - Interior Lighting
Res. - Miscellaneous
Com'l. - Other
Res. - Refrigerator
Com'l. - Ventilation
Res. - Cooking
Res. - Clothes Dryer
Com'l. - Refrigeration
Remainder of Buildings
sectorIndustrial Sector
Agriculture & OtherSector
Time of Day (hour starting)
System Peak
Demand (GW)
Source: LBNL: Electricity Use in California: Past Trends and Present Usage Patterns
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Component Model FractionsComponent Model Fractions
WECC LMTF will provide regional defaults
winter, summer, and shoulder seasons
6:00, 9:00, 15:00, 18:00 hours
Multiple climate zones in WECC
Composition for residential, commercial and mixed load types Please review and provide your comments when LMTF data
becomes available (WECC posting is expected in middle of June2009)
Utilities can over-ride the defaults with bus-specificinformation (recommended)
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WECC TPL StandardsWECC TPL Standards
Existing WECC transient voltage dip criteria was developed underpresumption that load does not experience a structural change duringa disturbance (mostly constant current active and constantimpedance reactive components were used for load representation)
WECC voltage dip criteria was developed as a proxy for low voltagesat which load loss may occur
Transient voltage dip criteria is used only by WECC (not in NERCTPL Standards)
WECC transient
voltage dip criteria
(developed underassumption of constant
current load model)
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WECC TPL StandardsWECC TPL Standards
Transmission faults are likely to results in a wide-spread stalling of air-conditioners, when a stalled motor becomes a locked-rotor shortcircuit for several seconds until it is disconnected by a thermal relay
Actual system performance (and that captured by the new loadsmodel) may not be able to meet the WECC voltage dip criteria
See next slide
Actual system
performance (and that
simulated with a newcomposite load model)
may not meet WECC
transient voltage dip
criteria Time
Bus Voltage
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Palo VerdePalo VerdeDevers Fault Simulations and ActualDevers Fault Simulations and Actual
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