1. Western Electricity Coordinating Council Renewable Energy Modeling Task Force Wind and Solar Modeling Update Contact: Abraham Ellis Salt Lake City, UT March 21, 2012
Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

2. WECC REMTF Charter The Renewable Energy Modeling Task Force shall
Develop and validate generic, non-proprietary, positive-sequence power flow and dynamic simulation models for solar (and wind) generation for use in bulk system studies
Implement models in commercial simulation software
Issue guidelines, model documentation
Coordinate with stakeholders
REMTF reports to the WECC Modeling & Validation Work Group (MVWG)
Responsible for maintaining dynamic modeling in the Western Region, per NERC MOD standards

3. SOLAR MODELS
Copper Mountain 48 MW PV plant in Nevada (Picture: inhabitat.com)

4. Solar (PV) Models Under Development
REMTF working on three models for PV plants
PV Plants (full-featured and simple models)
Distributed PV
Model
Purpose
Status
PV1X
Large-scale PV plats
Specification complete
PVD1
Stand-alone model for plant or aggregated distributed PV
Specification nearly complete
CMPLDWg
CMPLDW with DG for distributed PV
Version 3
Options for PF representation under discussion

5. Large PV Plant Modeling
In power flow, PV modeled explicitly as generator
Should include feeder or collector system equivalent per WECC guide
In dynamics, use stand-alone PVD1 model or PV1X model
PVD1 (stand alone)
PV1X OR

6. PV1X Model Structure
Identical structure as WT4 model

7. PV1X P/Q and Plant Control
Separate model for plant control, including power-frequency droop
Simplify as indicated (items are WGT4-specific)

8. Generator/Converter
Simplify as indicated (item is WGT4-specific)

9. PVD1 Model 3 1 2 Change input to vterm + (iterm)(xcomp)
Insert summation, + qref
Insert summation, + p_var

10. Distributed PV Generation
In power flow, residential/commercial PV would be load-netted or represented explicitly (several options possible)
In dynamics, represent with CMPLDWg model
CMPLDWg = CMPLDW + DG
Simple version of PVD1

11. PV Portion of CMPLDWg
Simplified version of PVD1: No p_var, no volt/var control, no P/Q priority

12. CMPLDWg PSLF DYD File
cmpldw "LOAD-CMP" "CM" : #9 mva=200. /
"Bss" "Rfdr" "Xfdr" "Fb" 0.1 /
"Xxf" "TfixHS" 1.00 "TfixLS" 1.01 "LTC" 0 "Tmin" 0.9 "Tmax" 1.1 "step" /
"Vmin" "Vmax" "Tdel" "Ttap" 5. "Rcomp" 0 "Xcomp" 0 /
"Fma" "Fmb" "Fmc" "Fmd" 0. "Fel" 0.1 /
"Pfe" "Vd1" "Vd2" 0.7 "frel" 0.5 /
"Pfs" "P1e" 2. "P1c" 0.33 "P2e" 1 "P2c" "Pfreq" 1 /
"Q1e" 2. "Q1c" 0.33 "Q2e" 1 "Q2c" "Qfreq" -1 /
"MtpA" 3 "MtpB" 1 "MtpC" 3 "MtpD" 0 /
"LfmA" 0.85 "RsA" "LsA" "LpA" "LppA" /
"TpoA" 0.16 "TppoA" "HA" "etrqA" 0 /
"Vtr1A" 0.7 "Ttr1A" "Ftr1A" 0.5 "Vrc1A" 1.1 "Trc1A" 55. /
"Vtr2A" 0.8 "Ttr2A" "Ftr2A" 0.2 "Vrc2A" 1.2 "Trc2A" 66. /
"LfmB" "CompPF" /
"Vstall" 0.6 "Rstall" "Xstall" "Tstall" "Frst" 0.5 "Vrst" "Trst" /
"fuvr" "vtr1" "ttr1" 0.2 "vtr2" 0. "ttr2" 5. /
"Vc1off" 0.5 "Vc2off" 0.4 "Vc1on" 0.6 "Vc2on" 0.5 /
"Tth" "Th1t" "Th2t" 1.3 "Tv" 0.05 /
"LfmC" 0.85 "RsC" "LsC" "LpC" "LppC" /
"TpoC" 0.16 "TppoC" "HC" "etrqC" 2 /
"Vtr2A" 0.8 "Ttr2A" "Ftr2A" 0.2 "Vrc2A" 1.2 "Trc2A" 66.
“DGtype” 1.0 “Pdgflag” “Fdg_Pdg” “PFdg” “ialim” /
“vt0” “vt1” “vt2” “vt3” “vrflag” /
“ft0” “ft1” “ft2” “ft3” “frflag” /

13. Specification of DG Fraction
A1. In dynamic file only, as a fraction of load
Best alternative short term
A2. In dynamic file only, as an absolute MW value
In power flow, as a negative load associated with existing load through special ID
Could be confusing to users
C. In power flow load record
Would require changes to power flow programs
Best solution long term
CMPLDWg prototype to support A1 and A2
Consult with MVWG and SRWG on C (future)

14. Summary for Solar Models
PV1X/PVD1 and CMPLDWg
Specifications working documents
Prototype for testing/validation under development
Collecting lab/field data for model validation effort

15. WIND MODELS

16. WT1/WT2 Pitch Control Model
REMTF consensus: need to re-design

17. WT1/WT2 Pitch Control Model
Proposed new implementation
PI Control, Rate Limiter, Lag filter
Voltage Dip Flag
Set based on voltage; reset based on voltage and generator speed
Action Items: test/validate against manufacturer models; update draft REMTF specification
Source: R. Zavadil

18. WT1/WT2 Pitch Control Model
Good results compared to two major Type 1 WTG vendor-specific PSCAD models
Source: Zavadil
Source: Zavadil
P-I block: Gain=1, Time Constant=0.1s
Lag Filter: Gain=2, Time Constant=3 s
Rate Limiter: Up(pitch back)=1.5, Dn(restore)=0.5
P-I block: Gain=1, Time Constant=0.001s
Lag Filter: Gain=1, Time Constant=0.01 s
Rate Limiter: Up(pitch back)=0.5, Dn(restore)=0.5

19. WT1/WT2 Pitch Control Model
Good validation against MWT1000A manufacturer model

20. WT1/WT2 Pitch Control Model
Partial success with validation against V82-AGO
50% output
40% voltage dip
50% output
80% voltage dip
Proposed model structure would not capture this behavior
100% output
40% voltage dip
100 % output
80% voltage dip

21. WT1/WT2 Pitch Control Model
Acceleration control comes into play for severe disturbances and Pgen = Prated ev
Speed
Torque
Pitch

22. WT2 Rotor Resistance Model
Do we need to change anything? No
Manufacturer: WT2 model is fine as is

23. New WT4 Model
Approved by REMTF with minor modifications

24. WT4 Generator/Converter

25. WT4 P/Q Control

26. WT4 Drive Train

27. WT4 Plant Control Need to add active power control
High frequency droop

28. WT4 Validation Good results for multiple manufacturers
Differences in controls approach drove model options
Siemens
Vestas
ABB
Source: Pourbeik

29. New WT3 Model
Identical to WT4 model, except for pitch and torque control

30. New WT3 Model Initial validation with two vendors – good news ABB
Vestas
Source: Pourbeik

31. Summary for Wind Summary for Phase 2 WTG models Next Steps
WT1: Redesigned pitch control, investigating ways to emulate acceleration control for V82-AGO
WT2: Use redesigned pitch; otherwise OK as is
WT3: Progress
WT4: Specs approved, with addition of P/f droop
Next Steps
Complete official specifications by June
Present for MVWG approval in November

32. Other REMTF Items to Address
Default Data for Existing WTG Models
Typical machine data
Testing Procedures for Non-Synchronous Generators
Data Preparation manual
Language around DG?

33. Discussion About Plant-Level Model Validation

34. Why So Much Detail in EU Models
Driven by Grid Codes!
For example, Latest Proposed ENTSO-E Grid Code, Article 32: Common Provisions on Compliance Simulations, Parts (3) & (4):
3. The Power Generating Facility Owner shall provide simulation results relevant to each and any individual Generating Unit within the Power Generating Facility in a report form in order to demonstrate the fulfillment of the requirements of this Network Code. The Power Generating Facility Owner shall produce and provide a validated simulation model for a Generating Unit. […]
4. The Relevant Network Operator shall have the right to check the compliance of a Generating Unit with the requirements of this Network Code by carrying out its own compliance simulations based on the provided simulation reports, simulation models and compliance test measurements.
Reference:

35. Models for Interconnection Studies
Requirements are vague in comparison
Applicable requirements: NERC FAC/TPL and FERC LGIP/SGIP
IVGTF Task Force 1.1 recommended changes to MOD standards and also recommended that FAC-001 be reviewed and expanded to clearly cover modeling requirements for generator interconnection study process
NERC Standard FAC requires evidence that assessments included steady-state, short circuit and dynamics studies as necessary to confirm compliance with NERC Standard TPL-001-0

36. NERC IGVTF Task 1.3 Report
Reference: IVGTF Task 1.3 Report, Section 6: Models for Facility Connection, Page 91

37. NERC IGVTF Task 1.3 Recommendations
Specific recommendations to FAC shown in red:
R2 The Transmission Owner’s facility connection requirements shall address, but are not limited to, the following items:
[…]
[Add] R Generation facility modeling data, including appropriate power flow, short circuit and dynamic models, and verification requirements. [add appendix to clarify]

38. NERC IGVTF Task 1.3 Report
Proposed Appendix to FAC about models:
Preliminary or approximate power flow and dynamic models may be adequate for the preliminary assessment of interconnection impacts, or to represent existing and proposed projects that are not in the immediate electrical vicinity of the Facility being studied. However, detailed dynamic (and possibly transient) models for the specific equipment may be needed for the System Impact Study and Facilities Study, to represent the Facility and other equipment in the electrical vicinity. Generic non-proprietary publicly available models are more appropriate for the NERC model building process covered by existing MOD standards, although validated generic models with specifically tuned parameters may be adequate for interconnection studies. The models for interconnection studies must be acceptable to the TO in terms of simulation platform, usability, documentation & performance.

39. IVGTF 1.3 Proposed Modeling Grid Code
Preliminary model data may be used for the initial feasibility study of a variable generator interconnection project
The best model available shall be used for the final SIS or FS. These models can be user written and require non-disclosure agreements
The detailed dynamic model must be accurate over the frequency range of 0.1 to 5 Hz. Time constants in the model should not be less than 5 ms
Detailed dynamic models must be validated against a physical or type test.
Verification of detailed model performance should be confirmed during commissioning to the extent possible. The following tests shall be performed:
Primary/secondary voltage control
Low voltage and high voltage ride through
Power factor/reactive power capability
Power ramping and power curtailment
Verification of the non-propriety model accuracy may be performed by simulation tests compared with the detailed model performance.
At the end of the commissioning tests, the Generator Owner shall provide a verified detailed model and a non-proprietary model, ideally in IEEE, IEC or other approved format, for ongoing regional studies such as TPL-001.