1. NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. Western Wind and Solar Integration Study - Phase 3 Kara Clark, NREL Nick Miller, Miaolei Shao, Slobodan Pajic, Rob D’Aquila, GE July 15, 2014

2. 2 Western Wind and Solar Integration Study Phase 1 - Can we integrate high penetrations of wind and solar into the Western Interconnection? What do we need to do to accommodate this? Phase 2 – What is the impact of high penetration wind and solar on the rest of the generation fleet? Specifically, what are the costs of cycling, and the emissions impacts of cycling? Do wind and solar differ in their impact?

3. 3 WWSIS Phase 3 Project Objectives Examine Western Interconnection large scale stability and frequency response with high wind and solar penetration Identify means to mitigate any adverse impact (advanced controls, transmission, storage, etc) Investigate whether power system reliability can be maintained with high wind and solar penetration

4. 4 Building the Study Scenarios WECC power flow and dynamic databases o 2022 Light Spring, 2023 Heavy Summer WWSIS Phase 2 renewable scenario o High Mix 33% wind and solar annual energy (½ and ½) Mine WWSIS Phase 2 PLEXOS results o Time periods that match power flow cases, o High levels of wind and solar generation, o Balance of fleet commitment and dispatch Composite load model including rooftop PV Defined 4 regions for reporting o Northwest = Northwest o California = IID, LADWP, PGE, SDG&E, SCE o Northeast = PACE, ID, MT, Sierra, WAPA UM o Desert Southwest = AZ, El Paso, NV, NM, WAPA RM, PSCo

5. 5 Wind and Solar Siting

6. 6 WWSIS 3 Light Spring scenarios Reference Case High Renewable Case ~21GW Wind, ~5GW Solar 28% penetration* ~27GW Wind, ~25GW Solar 57% penetration* * = % of instantaneous load

7. 7 WWSIS 3 Extreme Light Spring scenario Reference Case Extremely High Renewable Case ~33GW Wind, ~32GW Solar 69% penetration* High Renewable Case ~21GW Wind, ~5GW Solar 28% penetration* * = % of instantaneous load ~27GW Wind, ~25GW Solar 57% penetration*

8. 8 Composite Load Model (CMPLWG) Electronic M M M Loadflow Bus Static M UVLS UFLS PLagg PV gen. PLnet Pdg Pma Pmb Pmc Pmd Pel Pst QLnet Qdg

9. 9 Scope of Analysis Not comprehensive or exhaustive Frequency response focused on loss of 2 Palo Verde units Transient stability focused on loss of Pacific DC Intertie and fault on new bus in wind rich part of Wyoming Lots of monitoring Standard performance criteria Sensitivity analysis of mitigation measures

10. 10 Frequency Response Analysis Evaluate frequency response to loss of generation o Large central station o Distributed generation Apply frequency controls to wind plants Apply frequency controls to solar plants Add energy storage Illustrate impact of re-dispatch and/or de-commitment Headroom depletion

11. 11 Frequency Response Obligation BAL 003-1 Approximate FRO for 4 regions and 20 areas. Actual FRO is BA based

12. 12 Preliminary Frequency Response Results Frequency nadir 59.67 59.65 59.61 Settling frequency59.84 59.81 Preliminary. Not for Citation or Further Distribution. Reference High Renewables Extremely High Renewables ReferenceHigh RenewablesExtremely High Renewables FROFRKtFRKtFRKt WECC84013520.4613110.4210650.38 California2963050.343120.332950.32 DSW2202150.441190.27970.22 Northeast82610.26470.3510.27 Northwest1314340.624830.622800.53 2 Palo Verde unit outage

13. 13 Apply Frequency Controls to Wind Plants 5% primary frequency response (aka APC = active power control) o Apply to new wind plants loaded <= 95% of rating o No change to power flow, assume wind speed is sufficient to deliver 5% more o ~900 MW headroom Controlled inertial response Combination of APC and controlled inertial response

14. 14 High Renewables Frequency Response High Renewables HR + Wind Controlled Inertial Response HR + Wind Active Power Control HR + Wind Controlled Inertial Response & APC Preliminary. Not for Citation or Further Distribution.

15. 15 Apply Frequency Controls on Solar Plants 5% primary frequency response o Apply to new utility scale PV only o ~820 MW curtailment o Aggressive control No controlled inertial response

16. 16 High Renewables Frequency Response Preliminary. Not for Citation or Further Distribution. High Renewables HR + Solar Governor Response

17. 17 Transient Stability Analysis Evaluate stability under heavy summer conditions in response to o PDCI outage o Broadview 500kV fault and line trip o Laramie River 345kV fault and line trip Impact of load modeling Analyze coal plant displacement/retirements o Aeolus 500kV fault and line trip o Extremely high renewables o Light spring System strength o % Non-synchronous generation Investigate possible relay impacts/issues

18. 18 WWSIS 3 Extreme Light Spring scenario Reference Case Extremely High Renewable Case ~33GW Wind, ~32GW Solar 69% penetration* High Renewable Case ~21GW Wind, ~5GW Solar 28% penetration* * = % of instantaneous load ~27GW Wind, ~25GW Solar 57% penetration*

19. 19 New Transmission into NE part of WI Aeolus 500kV

20. 20 Coal Displaced/Retired Coal !! Preliminary. Not for Citation or Further Distribution. Reference High Renewables Extremely High Renewables Reference High Renewables Extremely High Renewables DSW Northeast

21. 21 NE Areas Idaho (60) Montana (62) Sierra (64) PACE (65) Preliminary. Not for Citation or Further Distribution. Reference High Extremely Renewables High Renewables Reference High Extremely Renewables High Renewables Reference High Extremely Renewables High Renewables Reference High Extremely Renewables High Renewables

22. 22 WYODAK 230 kV Bus Voltage Preliminary. Not for Citation or Further Distribution. Reference High Renewables Extremely High Renewables Extremely High Renewables with Reinforcements

23. 23 Dave Johnson Synchronous Condenser Conversion Preliminary. Not for Citation or Further Distribution. Reference Extremely High Renewables with Reinforcements Power (MW) Reactive Power (MVAr)

24. 24 System Strength Systemic concern about future low levels of synchronous generation o EirGrid monitors “system non-synchronous penetration”, currently limited to <50%, potential to raise limit to <75% o Also an issue in west Texas, Brazil, Australia Fault currents

25. 25 Synchronous vs. Non-synchronous Commitment Condensers Preliminary. Not for Citation or Further Distribution. California DSW Northeast Northwest HS Reference HS High Renewables LSP Reference LSP High Renewables LSP Extremely High HS Reference HS High Renewables LSP Reference LSP High Renewables LSP Extremely High HS Reference HS High Renewables LSP Reference LSP High Renewables LSP Extremely High HS Reference HS High Renewables LSP Reference LSP High Renewables LSP Extremely High HS = heavy summer LSP = light spring

26. 26 System Non-Synchronous Penetration ~66% SNSP without condensers ~ 61% with condensers Preliminary. Not for Citation or Further Distribution. HS Reference HS High Renewables LSP Reference LSP High Renewables LSP Extremely High HS Reference HS High Renewables LSP Reference LSP High Renewables LSP Extremely High HS Reference HS High Renewables LSP Reference LSP High Renewables LSP Extremely High HS Reference HS High Renewables LSP Reference LSP High Renewables LSP Extremely High HS = heavy summer LSP = light spring

27. 27 Light Spring Fault Currents LocationReferenceExtremely High Renewables Dave Johnson 230 kV19.7 kA/7,730 MVA10.7 kA/4,260 MVA Populus 345 kV25.1 kA/15,000 MVA20.1 kA/12,000 MVA

28. 28 Observations on high coal displacement / weak grid Dynamic models really need to be right when wind and solar are the dominant source of generation o WECC has longstanding best practice to keep dynamic models up-to-date o Wind and solar plant modeling needs to be held to the same level of accountability in high penetration future o More on investigation of sensitivity to WTG control specifics and of modeling implications. Local problems will occur o Good transmission planning practice is needed, especially for voltage management o There is no obvious reason why voltage and thermal problems can’t be solved by conventional methods – but they will need to be solved! Further investigation of weak grid aspects needed o Maximum fraction of non-synchronous generation the limit on wind and solar now in Ireland, Brazil, etc o Potential barrier to high penetration wind and solar in the US

29. 29 WWSIS 3 Next Steps Analysis done Draft final report this summer In-person TRC meeting in October Final report by end of December

30. 30 Thank You! Kara Clark National Renewable Energy Laboratory kara.clark@nrel.gov 303-384-7098