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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.

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Presentation on theme: "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."— Presentation transcript:

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. Operating Reserves and Variable Generation Erik Ela, Michael Milligan January 28, 2012 WECC Webinar

2 Outline Overview: Operating Reserve categories Operating Reserves in Practice WECC Other areas (North America and Europe) Operating Reserve Methods with High VG FESTIV and Plexos models Proposal for NREL/WECC study National Renewable Energy Laboratory Innovation for Our Energy Future

3 Operating Reserves and VG Operating Reserves and Variable Generation Erik Ela, Michael Milligan, and Brendan Kirby August 2011: What are the operating reserves standards and policies in practice? What types of operating reserve methods are being proposed in research? How does variable generation change the need?

4 Definitions (for this presentation) Operating Reserves: Capacity above or below that which is scheduled and used to maintain the active power balance of the system during operations Upward and downward response at all time scales For multitude of reasons: Maintain frequency at nominal level (60 Hz in U.S.) Reduce Area Control Error (ACE) to zero Assist neighboring balancing authority Reduce over flow of transmission lines and transformers Manage Voltage (mostly done with reactive power) Etc. Reactive Power Reserves: Reactive Power capacity to facilitate voltage control (not discussed here) Planning Reserves: Long term capacity to ensure system adequacy (not discussed here) National Renewable Energy Laboratory Innovation for Our Energy Future

5 Normal Conditions National Renewable Energy Laboratory Innovation for Our Energy Future Normal conditions Regulation Reserve (AGC, load frequency control) Following Reserve (Flex reserve, load following, balancing reserve)

6 Contingency Conditions National Renewable Energy Laboratory Innovation for Our Energy Future Disturbance Frequency (Hz) 60 Primary Reserve (frequency responsive reserve) Secondary Reserve (spinning and non- spinning reserve) Secondary Freq. Control Tertiary Reserve (supplemental reserve) Bring back to a secure state

7 New Condition National Renewable Energy Laboratory Innovation for Our Energy Future ERCOT event: February 26, 2008 Potential for a Ramping Reserve 1600 MW in 3.5 hours More significant and rare than Following Reserve Much slower than Contingency Reserve

8 Operating Reserve Regulating Reserve Contingency Reserve Following Reserve primary Ramping Reserve Non-event Event Correct the current ACE Manual Part of optimal dispatch InstantaneousNon-Instantaneous secondarytertiarysecondarytertiary Stabilize FrequencyReturn Frequency to nominal and/or ACE to zero Replace primary and secondary Return Frequency to nominal and/or ACE to zero Replace secondary Automatic Within optimal dispatch Correct the anticipated ACE Operating Reserve Categorization

9 Typical Methods in WECC Secondary(Spinning) reserve: Max { 3% load + 3% generation, Largest Contingency } 50% synchronized, all deployable within 10 minutes Primary (FRR) reserve: no requirement yet, Part of new BAL003 Regulation Reserve: To meet CPS1 and CPS2 No explicit requirement Typically percent of load Reliability based control will likely affect requirements Following reserve: no explicit requirement CAISO flexible ramping product proposal Ramping Reserve: no explicit requirement National Renewable Energy Laboratory Innovation for Our Energy Future

10 Regulation Reserve in North America National Renewable Energy Laboratory Innovation for Our Energy Future RegionRequirement Definition PJM Based on 1% of the peak load during peak hours and 1% of the valley peak during off-peak hours. NYISO Set requirement based on weekday/weekend, hour of day, and season. ERCOT Based on 98.8 th percentile of regulation reserve utilized in previous 30 days and same month of previous year and adjusted by installed wind penetrations (described further below) CAISO Use a requirement floor of 350-MW up and down regulating reserves which can be adjusted based on load forecast, must-run instructions, previous CPS performance, and interchange and generation schedule changes. MISO Requirement made once a day based on conditions and before the day-ahead market closes. ISO-NEBased on month, hour of day, weekday/sat/sun.

11 European comparison National Renewable Energy Laboratory Innovation for Our Energy Future N America (NERC)Europe (ENTSOE) Regulating Reserve NERC does not provide for explicit quantitative requirements. Reserve is only used for normal conditions. NERC enforces compliance with Control Performance Standards CPS1 and CPS2. It. The CPS drive the requirements for each BA which are mostly based on time of day and season. Secondary reserve requirement is explicitly based on statistical equation and mostly comes from load variability. However, secondary reserve is used for both contingencies and normal variations. There are no compliance measures. Following Reserve No requirements Contingency Reserve (Primary) No requirement. In discussions. Only a frequency bias requirement as part of ACE equation of 1% peak load. Primary Control (3000 MW) split between TSOs based on load share. Full Response at 200 mHz. 20 mHz maximum insensitivity. Contingency Reserve (Secondary) Disturbance Control Standard DCS must recover from contingency in 15 minutes. Enough to recover largest contingency. Many regions require at least 50% to be online/spinning. Similar requirement to DCS. Return ACE to zero within 15 minutes. Split between primary secondary and tertiary. Sum of secondary and tertiary should be at least as large as largest contingency Contingency Reserve (Tertiary) No quantifiable requirement but contingency reserve must be replaced within 105 minutes following contingency. No requirement Ramping ReserveNo requirements

12 Future methods with consideration of high penetration of Variable Generation National Renewable Energy Laboratory Innovation for Our Energy Future

13 Wind Integration Study Summaries NYISO/NYSERDA 2005 (10% capacity): No additional contingency reserves. Regulating reserves require slight increase based on keeping 3 sigma of variability. Minnesota 2006 (25% energy): No additional contingency reserves. Regulating reserves based on geometric addition of load and wind variability, with wind variability based on 100 MW wind farms. Used 5 sigma. Load following reserve based on 2 sigma of five minute changes in net load. Operating reserve margin (comb. of load following and ramping reserve) based on hourly forecast errors and was a dynamic requirement based on the hourly forecast.

14 Wind Integration Study Summaries California ISO 2007 (20% capacity): Detailed observation of CAISO scheduling time lines including ED initiation, completion, and basepoint interval. Used swinging door algorithm to calculate regulating reserves and load following reserves which quantifies needs of capacity, ramp rate, and ramp duration. Study showed that persistence forecast errors can impact regulating reserves. All Island Grid Study 2008 (multiple scenarios): Spinning Reserve based on largest contingency and additional contribution from wind. Replacement reserve (can be provided by offline units with startup times less than 60 minutes) was calculated by tool that looked at probabilistic distributions of wind and load forecasts. This was based on how the thousands of scenarios for wind and load were reduced to the 5 or 6 used in the simulation that the 90 th percentile should be met.

15 EWITS Methods Reserve demand as a function of Predicted operating levels (wind, load)

16 Simulation Tools

17 FESTIV Flexible Energy Scheduling Tool for Integration of VG SCUC, SCED, and AGC sub-models Models at high resolution Typically AGC, the highest resolution is at 2-6 seconds Models multiple time frames with communication between sub-models Multiple chances of forecast error and forecast correction Interval length, interval update frequency, process time and optimization horizon configurable

18 FESTIV Flexible operating structures All modeling timing parameters, how reserves are used, AGC mode of operation, etc. Deployment of operating reserves modeled Definitions defined by user Reserves are held in one sub-model and used in another Can measure effectiveness of operating reserves in terms of both costs and reliability

19 FESTIV The model focuses on short-term reliability impacts (i.e. 1 day-1week) It can be used to compare inputs (e.g. VG penetrations) as well as scheduling strategies (e.g. dispatch frequency) Metrics: Extreme imbalances - CPS violations (with configurable L10 and CPS interval) Total imbalances - Absolute ACE Energy (AACEE) Variability of imbalances - ACE Similar metrics can be made for line flow, voltage, etc. e.g. Absolute Line Flow Exceedance in Energy (ALFEE)

20 FESTIV Flow Diagram Data Flow Process Flow Run DASCUC Unit status and unit start-up for all units with start time > t RTCSTART t RTC interval? Run RTSCUC Unit status and unit start-up for all units t RTD interval? Run RTSCED Dispatch schedules and reserve schedules for all units Run AGC AGC schedule, realized generation for all units, production cost, and ACE t = t+t AGC yes no yes no

21 Metric and Outputs National Renewable Energy Laboratory Innovation for Our Energy Future ACE without Regulating Reserve ACE with Regulating Reserve CaseCPS2 scoreAACEE(MWh) ACE (MW) Costs ($) Case 6: Imperfect real-time forecasts at 5-minute intervals,regulation reserves = 1.5% of load 27 violations 96.3% $13.237M Case 7: Imperfect real-time forecasts at 5-minute intervals, with WWSIS2 regulation reserves 19 violations 97.4% $13.313M

22 PLEXOS SCUC and dispatch model with sub-hourly resolution (down to 5 min) Evaluate effectiveness of following (flex) reserves DA unit commitment DA wind, solar forecasts 4-HA unit commitment RT dispatch Contingency and regulation reserve requirements Flex deployed 4-HA wind, solar forecasts Contingency, flex, and regulation reserve requirements Actual wind, solar generation Coal, nuclear commitment + Gas CC commitment

23 Project Proposal in collaboration with WECC National Renewable Energy Laboratory Innovation for Our Energy Future

24 Project Proposal Step 1: Review of current and proposed methods for reserve requirements (continuation of VGS initiative) Step 2: Use requirements in simulation models and compare ACE and cost metrics among all methods Step 3: Look through data results to see what influences needs Step 4: Determine if new reserve requirement method is appropriate for recommendation National Renewable Energy Laboratory Innovation for Our Energy Future

25 Reserve Requirement Methods The following methods have already been in discussion with the WECC VGS: Current WECC requirements ERCOT BPA NREL Western Wind and Solar Integration Study NREL Eastern Wind Integration and Transmission Study PNNLs method National Renewable Energy Laboratory Innovation for Our Energy Future

26 Example: WWSIS-2 Total requirementComponents

27 Approach FESTIV can show the benefits and tradeoffs of different regulation reserve methods using cost and ACE metrics Plexos model can show the benefits and tradeoffs of different following (Flex) reserve methods using cost metrics Wind and solar will have different impacts Project to be proposed to the OC Suggest Bi-monthly meeting with interested members of OC/VGS for review and guidance Stakeholder participation is key! National Renewable Energy Laboratory Innovation for Our Energy Future

28 Next Steps… Questions? National Renewable Energy Laboratory Innovation for Our Energy Future


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