Optimizing Wind Generation in ERCOT Nodal Market Resmi Surendran ERCOT Chien-Ning Yu ABB/Ventyx Hailong Hui ERCOT FERC Conference on Increasing Real-Time and Day-Ahead Market Efficiency through Improved Software - June 23-25, 2014
Agenda Overview of ERCOT Wind in ERCOT Operational Challenges Wind Scheduling in ERCOT Nodal Market Day-Ahead Market (DAM) Reliability Unit Commitment (RUC) Real Time Market (RTM) Improvements due to better handling of wind Summary June 23-25, 2014 2
ERCOT 85% of Texas load 24 million consumers 40,530 circuit miles of high-voltage transmission 74,000 megawatts (MW) capacity for peak demand From 550 generation resources With 8.7 % Wind capacity included 11,059 MW Wind Capacity 68,305 MW peak demand (Aug.3, 2011) Peak Wind 10,296 MW (March 26, 2014) $33 billion Market ~1,100 active Market entities 73% of load are competitive-choice customers 179 competitive retailers Nodal market completed three year of operation on Dec. 1, 2013 Extensively working on ensuring Resource Adequacy June 23-25, 2014 3
ERCOT Wind Generation 25,000 MW ERCOT Wind Installations by Year (as of April 2014) 20,000 MW Cumulative MW Installed Target MW Target Yr Cumulative Planned (Signed IA) Achieved Yr 18,364 19,190 19,690 15,000 MW 2000 2010 2005 5000 2015 2007 14,169 7,305 8,131 8,631 10,000 MW 10000 2025 2010 8,005 8,916 10,407 9,400 9,604 11,065 3,110 11,059 5,000 MW 4,785 0,000 MW 2,875 1,854 816 977 1,173 1,385 116 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 The data presented here is based upon the latest registration data provided to ERCOT by the resource owners and can change without notice. Any capacity changes will be reflected in current and subsequent years' totals. Scheduling delays will also be reflected in the planned projects as that informationisreceived. This chart reflects planned units in the calendar year of submission rather than installations by peak of year shown. June 23-25, 2014 4
ERCOT Wind Generation 11,059+ MW of installed wind capacity Significant amount of additional MW being reviewed Wind generation record of Peak Wind 10,296 MW (March 26, 2014) 29% of system load Improved transmission, market rules and operator tools allowed more energy from wind to be generated June 23-25, 2014 5
Wind Pattern in ERCOT June 23-25, 2014 6
Wind Pattern in ERCOT ERCOT Wind Generation vs. System Load on a typical peak day June 23-25, 2014 7
Operational Challenges due to High Wind Inadequate transmission for projected wind growth Constraint management under high and low wind Higher frequency deviations due to large system excursions Difficulty in managing transient stability due to reduced inertial response Increased variability of net load Higher Ancillary Service Requirement Increased Non-Spin for forecast error of net load Increased Regulation due to increased net load variability Increased volatility in prices Lower average system wide energy prices Lower average Real Time prices in West Zone Higher Day-Ahead premium in West Zone June 23-25, 2014 8
Wind Input to ERCOT Markets Wind Forecasts Hourly forecasts for a rolling 48-hour in both system level and individual Wind-Powered Generation Resource (WGR) level Total ERCOT Wind Power Forecast (TEWPF): probability distribution of the hourly production potential from all wind-power in ERCOT for each of the next 48 hours Short-Term Wind Power Forecast (STWPF): 50% probability of exceedance forecast Wind-powered Generation Resource Production Potential (WGRPP): 80% probability of exceedance of the TEWPF Current Operating Plan (COP) Anticipated operating conditions for next seven Operating Days WGRs are required to keep High Sustained Limit(HSL) in COP updated to less than or equal to the most recent STWPF for the first 48hrs June 23-25, 2014 9
Wind in Day-Ahead Market The QSE representing WGRs may participate in DAM for wind scheduling by submitting one of the following offers or bids in DAM: Three-Part Supply Offer to sell energy for the physical WGR Virtual Energy Only Offers to sell or Bids to buy at the WGR Settlement Point CRR Point to Point (PTP) Obligation Bids with source or sink at the WGR Settlement Point Physical offers are cleared based on HSL from COP June 23-25, 2014 10
Wind in Reliability Unit Commitment WGRs are required to participate in RUC by submitting a valid COP The full capacity up to HSL of WGR is considered available to be dispatched in RUC WGRPP value used in the RUC for each WGRs is considered the available capacity of the WGR when determining capacity-short RUC charges, regardless of the real-time output of the WGR June 23-25, 2014 11
MW Wind Scheduling in DRUC 7,000 6,500 6,000 5,500 5,000 4,500 4,000 3,500 3,000 2,500 2,000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Hour DRUC WGR COP HSL STWPF WGRPP RT Wind June 23-25, 2014 12
Improvements in DAM/RUC for Wind Optimize the Phase Shifter tap in DAM/RUC Initially used fixed tap position for each hour for each Phase Shifter based on the WGR forecast and system load condition 2 days ahead of operating day Hourly absolute phase shifter tap positions are modeled as control variables in the optimization engine of Security Security Constrained Unit Commitment (SCUC) Shift factor of phase shifters with respect to the transmission constraint is defined as MW/tap i.e. the MW flow change on the constraint with respect to each tap position change Cost function of phase shifter tap position is modeled as a cost of tap position changes to the initial position June 23-25, 2014 13
Phase Shifters in ERCOT Majority of the Phase Shifter in ERCOT relieves transmission overloads caused by variations in wind generation The maximum degree change for each of the phase shifters is ±1.875*16 = ±30 degree Optimization of these phase shifter tap positions helped remove unrealistic congestion in DAM and RUC June 23-25, 2014 14
Wind in Real-Time Market RTM re-dispatch generation every 5 minutes based on current WGR output to take care of net load variability RTM issues WGR specific curtailment instruction for managing congestion WGRs are required to follow Base Points if the curtailment flag is set and automatically release from curtailment under low frequency WGRs are charged a fine if they generate more than 10% of their Base Point when they are curtailed unless it is aiding frequency June 23-25, 2014 15
Wind in Real-Time Market In Real-Time, WGRs are required to offer in their full capacity telemeter HSL equal to current net output of the facility limit its ramp rate to 20%per minute of its nameplate rating as registered with ERCOT when responding to or released from an ERCOT deployment limit its ramp rate to 25%per minute of its nameplate rating as registered with ERCOT anytime June 23-25, 2014 16
Real Time Proxy Offer Curve for Wind Resources If a Wind Generation Resource did not submit Energy Offer Curves in Real-Time Market, SCED market clearing engine will create a Proxy Offer Curve for it June 23-25, 2014 17
Energy Offer Curve Price ($/MWh) Typical Wind Aggregated Energy Offer Curve Energy Offer at 2AM Energy Offer at 5PM 50 0 0 500 1000 1500 2000 2500 3000 3500 4000-50 -100-150 -200-250 -300 Energy Offer Curve MW June 23-25, 2014 18
Improvements in RTM for Wind Implemented a flag to indicate when a WGR was curtailed Initially WGRs were required to Set HSL to current net output capability after each RTM run and hold it constant until the next RTM run consider the WGR as curtailed if the base point from RTM was less than HSL minus 2 and not curtailed if base point from RTM was greater than HSL minus 2 Changed to Telemeter HSL as current net output capability all the time Consider as curtailed and follow Base Point if the curtailment flag is set June 23-25, 2014 19
Wind Generation (MW) Wind Curtailment (MW) System Wide Wind Generation Curtailment 7000 800 6500 700 600 6000 500 5500 400 5000 300 200 4500 100 4000 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Hour 0 Base Point Telemetry MW HDL Curtailment MW June 23-25, 2014 20
Wind Generation (MW) Curtail Flag Real Time Curtailment of Single Wind Resource 180 10 160 9 140 8 120 7 100 6 5 80 4 60 3 40 2 20 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Hour 0 Base Point Telemetry MW HDL Curtailment Flag June 23-25, 2014 21
Enhanced Ability to Manage Volatility The Nodal Real-Time Market design has resulted in more stable frequency control Wind Ramp in Zonal The Graphs illustrate an observed 2000 MW drop in wind under both designs: Under the Zonal design the frequency fluctuated ± 0.08 Hz Under the Nodal design the frequency fluctuated ± 0.04 Hz Wind Ramp in Nodal June 23-25, 2014 22
Better Frequency Control Performance ERCOT s recent NERC CPS1 scores shows control improvements CPS1 12 Month Rolling Average = 163.30% June 23-25, 2014 23
Summary Texas continues to explore more wind power capacity more than 11,000 MW of commercial wind power capacity installed nearly 8,000 MW of new projects in development more than 26,700 MW under study. Special rules and system improvements made for wind generation resources resulted in better utilization of the available wind capacity while maintaining reliability Running RTM every 5 min based on current Wind Resource production Proxy offers at -$250, WGR specific curtailment signals, Requiring WGRs to follow Base Point and implementing deviation charges Putting ramp restrictions Requiring WGRs to provide primary frequency response Phase shifter tap optimization, June 23-25, 2014 24
June 23-25, 2014 25
Appendix June 23-25, 2014 26
Wind Generation in U.S. Source: www.awea.org June 23-25, 2014 27