1. WECC Composite Load Model
WECC MVWG Meeting
Bellevue, WA
August 25, 2011

2. Motion
Approve the implementation plant for replacing the “interim” load model with a Phase 1 “composite” load model
Use default data sets
Residential air-conditioner stalling disabled*
* No revision of the WECC reliability criteria is needed

3. Composite Load Model Development

4. Load Modeling
In the first 40 years of digital simulations, the focus was on modeling the supply side
We have reasonably good power plant models
Models data is to get more consistent as more plants have digital controls
We have tools for power plant model validation using disturbance data
Now, the focus is shifting on modeling the supply side

5. Load Modeling Upcoming big changes on demand-side:
Loads will play much more influential role in power system stability
Resistive-type loads are phasing out (incandescent lights and resistive heating)
Energy inefficient but exhibit “grid-friendly” behavior
Power Electronic loads, VFDs, AC compressors, heat pumps, CFLs, LEDs are gaining their presence
Energy efficient but have undesirable characteristics from standpoint of dynamic stability
Increasing penetration of residential air-conditioners
Upcoming big changes on demand-side:
Electric vehicl chargers
Distributed generation
Reasonable models are needed to understand the system impacts of these changes, to plan and operate the system and to develop appropriate standards

6. Load Modeling – Setting Expectations
We can now achieve the great accuracy with generator models:
We model physical equipment that is well defined and under our control
We will never be able to achieve a comparable level of accuracy with load models
Load models will not be able to predict details
Load models should be capable of representing the load response in principle

7. WECC Load Modeling Philosophy
WECC uses a physical-based modeling approach:
Bottom-up model development
Develop models that represent physics and characteristics of the actual end-use components
Top-down model validation
Validate and calibrate model data using disturbance recordings

8. History Of Load Modeling in WECC
1980’s – Constant current real, constant impedance reactive models connected to a transmission bus
Reflected the limitation of computing technologies of that time
1990’s – EPRI Loadsyn effort
Several utilities use static polynomial characteristics for load representation
1990’s – IEEE Task Force recommends dynamic load modeling
The recommendation does not get much traction in the industry
1996 – BPA model validation study for August outage:
Need for motor load modeling to represent oscillations and voltage instability

9. History Of Load Modeling in WECC
2000 – 2001 – WECC “Interim” Load Model:
Presently used in planning and operational studies in WECC
20% of load is represented with induction motors, the remaining load is static, mainly constant current active, constant impedance reactive components
Tuned to match inter-area oscillations for August and August 4, 2000 events
“Interim” load model was intended as a temporary solution to address oscillation issues observed at California – Oregon Intertie
The model limitations and the need for a composite load model were recognized

10. History Of Load Modeling in WECC
Late 1980’s – Southern California Edison observed events of delayed voltage recovery attributed to stalling of residential air-conditioners
Tested residential air-conditioners, developed empirical AC models
1997 – SCE model validation study of Lugo event:
Need to represent a distribution equivalent
Need to have special models for air-conditioning load

11. Southern California Edison
Lugo Event – Load Modeling Lessons:
A. Need to represent a distribution equivalent
B. Need to have special models for residential air-conditioners

12. Load Modeling Efforts in the East
1994 – Florida Power published an IEEE paper, used a similar load model
1998 – Events of delayed voltage recovery were observed in Atlanta area by Southern Company, the events are analyzed and modeled
Southern Company and Florida Power used in principle similar approaches to SCE’s and eventually WECC model

13. WECC Load Modeling Task Force
2005 – WECC developed “explicit” load model:
Adding distribution equivalent to powerflow case (PG&E)
Modeling load with induction motors and static loads
Numerically stable in WECC-wide studies !
2007 – PSLF has the first version of the composite load model (three-phase motor models only)
– SCE-BPA-EPRI testing residential air-conditioners and developing models
2009 – residential air-conditioner model is added to the composite load mode

14. WECC Load Modeling Task Force
Composite Load Model Structure
Default data sets
Load composition
Load component data
Distribution equivalent
Tools for data management
Validation studies
System impact studies

15. WECC Composite Load Model (CMPLDW)
12.5-kV
13.8-kV M
69-kV
115-kV
138-kV M AC
UVLS
Electronic
UFLS
Static

16. Composite Load Model Structure
Composite load model structure is implemented in General Electric’s PSLF, Siemens PTI PSS®E, Power World Simulator
Similar model exists in PowerTech’s TSAT
TSS approved Composite Load Model Structure

17. Load Model Data

18. WECC Composite Load Model
Load Component
Model
Data
Distribution Equivalent Data M M
115-kV
230-kV M
Load Model
Composition
Data M
UVLS and UFLS Data
Electronic
Static

19. Distribution Equivalent DataM M
R + j X
69-kV
115-kV
138-kV M M B1 B2
Bss
Electronic
DV = 4 to 6%
X/R = 1.5
PL < 7%
B1:B2 = 3:1
X = 8%
LF = 110%
Tap = +/- 10%
Static

20. WECC Climate Areas ID Climate Zone Representative City NWC
Northwest Coast
Seattle, Vancouver BC
NWV
Northwest Valley
Portland OR
NWI
Northwest Inland
Boise, Tri-Cities, Spokane
RMN
Rocky Mountain North
Calgary, Montana, Wyoming
NCC
Northern California Coast
Bay Area
NCV
Northern California Valley
Sacramento
NCI
Northern California Inland
Fresno
SCC
Southern California Coast
LA, San Diego
SCV
Southern California Valley
SCI
Southern California Inland
DSW
Desert Southwest
Phoenix, Riverside, Las Vegas
HID
High Desert
Salt Lake City, Albuquerque, Denver, Reno

21. Load Composition Information
California Energy Commission: 2006 California Commercial End-Use Survey (CEUS)
LBNL Reports on Electricity Use in California
PNNL DOE2 building simulations
BPA-PNNL End-Use Load Characterization Assessment Program (ELCAP)
BPA Building Data
Load shapes provided by WECC members

22. California Commercial End-Use Survey
15 climate zones in California
Four seasons
Typical, Hot, Cold, Weekend
24-hour data
Data is available on CEC web-site
bottom
top

23. LBNL Electricity Use In California Study
Residential AC
Lighting
Commercial AC

24. PNNL Load Composition Model
CEC / BPA hired PNNL to develop load composition data
Detailed models of various building types
Residential loads are modeled using ELCAP data and DOE-2 models
Commercial loads are taken from CEUS
WECC developed mapping from end-uses to models

27. Load Class
Model Components

28. Portland Metro Area – BPA SCADA

29. Portland Metro Area – BPA SCADA

30. WECC Load Composition Model
There is a balance between precision and the amount of effort required to maintain the data sets
Based on the understanding developed using PNNL tool, WECC developed a simplified LCM version to create default data sets
Produces load composition data for summer (normal, peak, cool), shoulder (normal) and winter (normal) days

31. WECC Load Composition Model (Light)

32. Future work
Better understanding of “electrification” by regions, and ultimately by substations
Validation of building models
Right now commercial data is extrapolated from California CEUS, and residential data is used from ELCAP
Validation of load shapes at substation level:
Use customer mix data and models to produce load shapes
Validate the load shapes using SCADA data (5-min and 1–hour are available from BPAT)

33. Expert Help is Available
If you want detailed load composition information for your specific area, please contact David Chassin at PNNL
Detailed analysis is currently done for substations in Seattle, Portland and Phoenix

34. Motor Data

35. Commercial Compressor Motor

36. Commercial Fan and Pump Motors

37. Commercial Fan and Pump Motors

38. Protection Industrial compressors: Industrial fans and pumps
Trip and lock-out - half at 75%, half at 65%, 3 to 5 cycles
Industrial fans and pumps
Trip and lock-out - half at 75%, half at 65%, 3 to 5 cycles
Commercial compressors
Trip and lock-out: 20% of motors, trip < 60% 2 cycles
Trip and reclose: remaining, trip < 50% 2 cycles , reclose > 60% for 0.2 sec
Fans and pumps

39. Tools for Load Model Data Management

40. WECC Composite Load Model
cmpldw "CANYON " "1 " : #1 mva= "Bss" 0 "Rfdr" "Xfdr" 0.04 "Fb" 0.749/
"Xxf" 0.08 "TfixHS" 1 "TfixLS" 1 "LTC" 1 "Tmin" "Tmax" 1.1 "step" /
"Vmin" "Vmax" 1.04 "Tdel" 30 "Ttap" 5 "Rcomp" 0 "Xcomp" 0 /
"Fma" "Fmb" "Fmc" "Fmd" "Fel" /
"PFel" 1 "Vd1" 0.75 "Vd2" 0.65 "Frcel" 0.35 /
"Pfs" "P1e" 2 "P1c" "P2e" 1 "P2c" "Pfreq" 0 /
"Q1e" 2 "Q1c" -0.5 "Q2e" 1 "Q2c" "Qfreq" -1 /
"MtpA" 3 "MtpB" 3 "MtpC" 3 "MtpD" 1 /
"LfmA" 0.75 "RsA" 0.04 "LsA" 1.8 "LpA" 0.12 "LppA" /
"TpoA" "TppoA" "HA" "etrqA" 0 /
"Vtr1A" 0.7 "Ttr1A" "Ftr1A" 0.2 "Vrc1A" 1 "Trc1A" 9999 /
"Vtr2A" 0.55 "Ttr2A" "Ftr2A" 0.75 "Vrc2A" 0.65 "Trc2A" 0.1 /
"LfmB" 0.75 "RsB" 0.03 "LsB" 1.8 "LpB" 0.19 "LppB" /
"TpoB" 0.2 "TppoB" "HB" "etrqB" 2 /
"Vtr1B" 0.65 "Ttr1B" "Ftr1B" 0.1 "Vrc1B" 1 "Trc1B" 9999 /
"Vtr2B" 0.6 "Ttr2B" "Ftr2B" 0.1 "Vrc2B" 1 "Trc2B" /
"LfmC" 0.75 "RsC" 0.03 "LsC" 1.8 "LpC" 0.19 "LppC" /
"TpoC" 0.2 "TppoC" "HC" "etrqc" 2 /
"Vtr1C" 0.65 "Ttr1C" 0.05 "Ftr1C" 0.1 "Vrc1C" 1 "Trc1C" 9999 /
"Vtr2C" 0.6 "Ttr2C" 0.03 "Ftr2C" 0.1 "Vrc2C" 1 "Trc2C" /
"LfmD" 1 "CompPF" 0.98 /
"Vstall" 0.54 "Rstall" 0.1 "Xstall" 0.1 "Tstall" "Frst" 0.14 "Vrst" 0.95 "Trst" 0.3 /
"fuvr" 0.1 "vtr1" 0.6 "ttr1" 0.02 "vtr2" 0.9 "ttr2" 5 /
"Vc1off" 0.5 "Vc2off" 0.6 "Vc1on" 0.4 "Vc2on" 0.5 /
"Tth" 15 "Th1t" 0.7 "Th2t" 1.9 "tv" 0.025

41. LMDT 3A Powerflow case (done by SRWG)
Climate zone and load type are identified in “Long_ID” column of “load” table in PSLF
E.g. DSW_RES = Desert Southwest, predominantly residential loads
EPCL Programs (done by WECC Staff)
Default data sets for each climate zone and feeder type
Ability to over-ride defaults with specific information
Creates composite load model records for PSLF
PTI PSS®E Users
Convert from PSLF models
IPLAN tolls may be available ?
Load models will be distributed by WECC staff with study cases
LMDT 3A is posted on WECC web-site, including user’s manual

42. Load Model Validation Studies

43. August 4, 2000 Oscillation - CMPLDW

44. August 4, 2000 Oscillation - MotorW

45. August 4, 2000 Oscillation - CmpldW
Default Data Set

46. August 4, 2000 Oscillation - CmpldW
Tuning

47. June 14, 2004 Westwing Fault - CmpldW

48. July 28, 2003 Hasayampa Fault

49. July 28, 2009 Mid-Valley Fault
Voltage
Frequency

50. System Impact Studies

51. 2011HS – Chief Joseph Brake Blue = MotorW Red = CmpldW phase 1
Green = CmpldW phase 2

52. 2011HS – BC-Alberta Loss (546 MW)
Blue = MotorW
Red = CmpldW phase 1
Green = CmpldW phase 2

53. 2011HS – 2 Palo Verde Outage Blue = MotorW Red = CmpldW phase 1
Green = CmpldW phase 2

54. 2011HS – 2 Palo Verde Outage Blue = MotorW Red = CmpldW phase 1
Green = CmpldW phase 2

55. 2014LS – Montana Blue = MotorW, 77% dip Green = CmpldW, 22:00, 82% dip
Brown = CmpldW, 6:00, 82% dip

56. 2014LS – Montana Blue = MotorW Red = CmpldW,
Grey/Green = CmpldW, improved exciters at a hydro plant

57. Next Steps

58. Conclusions
WECC Composite load model is implemented in GE PSLF, Siemens PTI PSS®E, Power World, Power Tech TSAT
Tools are developed for load model data management
Default sets are developed:
12 climate zones in WECC,
four types of feeders
Summer, winter and shoulder conditions

59. Conclusions
Validation studies are done for FIDVR events and oscillations
System impact studies
Significant impact on faults in large load centers FIDVR
Impact on inter-area oscillations

60. FIDVR
Composite load model is capable of reproducing the FIDVR phenomenon
Composite load model can be tuned with reasonable data sets to match the historic events
MVWG at this point is not comfortable recommending using CMPLDW for FIDVR studies for compliance purposes
There is a concern that the FIDVR modeling can result in over- investment or unnecessary operational restrictions

61. FIDVR – Planned Work
Continue work on understanding the phenomenon of air-conditioner stalling in distribution systems (supported by DOE)
Work with AHRI
Feeder simulations
Speed up efforts on collecting disturbance recordings
SCE, SRP, Center Point Energy, PSE, BPA/PGE
A letter was sent to grid operators in the East
Tools for detecting FIDVR events in PMU data

62. CMPLDW – Phased Approach

63. CMPLDW CMPLDW has many benefits beyond FIDVR
TSS delayed PSS Policy review until appropriate load models are developed
Frequency response review studies are required

64. CMPLDW Plan
Today – Approve the implementation plan for adopting Phase 1 CMPLDW for system studies
Continue improvement of FIDVR modeling
Disturbance recordings, system impact studies
Start using the CMPLDW for studies to support the review of the WECC voltage dip criteria
Seek the approval of the “CMLDW with FIDVR enabled” and the new reliability criteria by Fall 2012

65. Motion
Approve the implementation plant for replacing the “interim” load model with a Phase 1 “composite” load model
Use default data sets
Residential air-conditioner stalling disabled*
* No revision of the WECC reliability criteria is needed