Renewable Integration at ERCOT

Transcription

1 Renewable Integration at ERCOT Dan Woodfin Director of System Operations ERCOT CIGRE Chile September 12, 2016

2 The ERCOT Region The interconnected electrical system serving most of Texas, with limited external connections 90% of Texas electric load; 75% of Texas land 71,197 MW peak demand, August 11, 2016 More than 43,000 miles of transmission lines 550+ generation units 220 MW with SPP ERCOT connections to other grids are limited to ~1250MW of direct current (DC) ties, which allow control over flow of electricity 30 MW with CFE at Eagle Pass 600 MW with SPP 100 MW with CFE at Laredo 300 MW with CFE at Mc Allen 2

3 ERCOT Inc. Independent System Operator (ISO) assigned with four primary responsibilities by the Texas state legislature: Maintaining System Reliability Ensuring Open Access to Transmission Facilitating of Competitive Retail Market Facilitating Competitive Wholesale Market Non-profit, non-governmental company regulated by the Texas Public Utility Commission ERCOT is not a market participant and does not own generation or transmission/distribution wires 3

4 Wholesale Energy Market Market participants bring generation on-line; ERCOT may start additional generation needed to maintain reliability Market participants submit offers for generation output ERCOT clears market every five minutes, using the generation with the lowest bids to serve the load, subject to transmission constraints Prices received by generators signal whether more or less output is needed from generators in that area at that time In general, the set of generator output levels produced by this process is the lowest cost way that doesn t overload the transmission system to meet the system load for each five minute interval 4

5 Average Wholesale Prices 5

6 Topics to be Covered Growth of Wind in ERCOT Market Importance of Wind Forecasting Use of Ancillary Services to cover risks Impact of low System Inertia Approaching Weak System issues Other Activities on renewable integration 6

7 Wind Generation July 2016 If the ERCOT Region were a separate country, we d be #6 in the world in wind generation capacity (as of end of 2015). 7

8 CREZ Transmission Completed in January 2014 As of January 30, 2014, the CREZ transmission projects were complete. The transmission plan is designed to serve approximately 18.5 GW of wind generation: ~3600 right-of-way miles of 345 kv $6.9 billion project cost Lines are open-access; use not limited to wind 8

9 Changing Resource Mix Installed Capacity (MW) Other 0.9% Renewables 0.008% Nuclear 8% Cogen 11% Coal 25% Gas-Steam 14.8% Coal 22.4% Gas-CT/CC 5% Late 1990s 2015 Renewables 13.8% Gas-Steam 50% Gas-CT/CC 36.5% Nuclear 5.7% Cogen 5.3% Other 1.4% 9

10 Wind Records Time Load (MW) Wind Generation (MW) Penetration at Record Time 02/18/ :20 35,528 14, % 03/23/ :10 27,245 13, % 10

11 MW Wind Duration Hours 11

12 Wind Forecasting 12

13 Wind Power Forecasting ERCOT contracts with AWS Truepower to produce a forecast for each Wind Generation Resource (WGR) Delivery: Hourly at 15 minutes after the hour Forecast period: hour forecast Forecast for each WGR is provided to the WGR; aggregate forecast is provided publicly 13

14 Day-Ahead Wind Forecast Performance

15 Load Over forecast Load Under forecast 3-hour-ahead Wind and Load Forecast Error Wind Over forecast Load Under forecast Outliers primarily due to Icing Wind Under forecast Load Over forecast Wind Over forecast Wind Under forecast 15

16 Ancillary Services 16

17 Ancillary Services (AS) AS are procured to ensure sufficient resource capacity is on-line, or able to be brought on-line in a timely manner, to balance the variability that cannot be covered by the 5-minute energy market Procurement occurs in Day-Ahead market from offers received to provide each AS Regulation Provided from selected generators that receive signal from ERCOT every 4 seconds to move up or down to maintain frequency between 5-minute dispatch intervals

18 Ancillary Services - Responsive Used to ensure sufficient capacity is available to respond to frequency excursions due to unit trips Capacity reserved from generators to provide governor response Note: all generators, including wind, must have governor-like response Up to 50% of Responsive requirement can be provided by load on underfrequency relays Quantity required varies by inertia on system 18

19 Ancillary Services Non-Spin Used to ensure sufficient capacity is available to cover load/wind forecast errors or replace deployed responsive reserves 30 min deployment required but most provided by 10 min quick start or unloaded on-line generation Quantity required varies by historic risk of forecast error 19

20 Dispatch 20

21 Dispatch on High Wind/Low Load Day Power Dispatch Summary per Fuel Type for 4/10/2016 Max Gen: MW at 08:40:17 PM Load Factor: Power (MW) Diesel Renewables Hydro Wind Combined Cycle Simple Cycle Gas Traditional Coal Nuclear Total Dispatch Wind Output 0 0 Time 21

22 Wind on the Margin 22

23 Inertia 23

24 Inertial Effect Initial rate of change of frequency (prior to any resource response) is solely a function of inertia 24

25 Critical Inertia Concept 0.4 Hz The level of inertia which causes the frequency to drop below the UFLS trigger before the fastest resources can provide sufficient frequency response (for the two STP trip) is the Critical Inertia 0.5 s 25

26 Primary Frequency Response(MW) More Responsive AS Required at Low Inertia 8000 Primary Frequency Response(MW) Other studies have shown that the amount of Responsive (if all provided by gen) required goes up asymptotically as inertia approaches the critical level Inertia (GW s) 26

27 Inertia(MW*s) Load(MW) Inertia in April 2016 by Unit Type 2016 April Inertia provided by Nuclear Inertia provided by Coal Inertia provided by Simple Cycle Inertia provided by Combined Cycle Load

28 Other Renewable Integration Activities 28

29 Other Renewable Integration Items Wind generators started to assist in frequency control for ERCOT after 2011, having an automatic response to frequency deviations, and provide enhanced voltage support Added 7-day wind forecast (previously 48 hour) Have implemented utility-scale solar forecast Inclement weather preparation Added new capability to manually adjust wind forecast during icing events Hosted Wind Generation Winter Preparation Webinar Have developed tools for use in control room to forecast and monitor: Inertia and Responsive Reserve requirements Net load ramp versus fleet capability Adding a new operator/shift in control room, in part to provide increased situational awareness of renewables and related issues to other desks 29

30 Weak System 30

31 Operational Experience Bus 1 Bus 2 Bus 3 Bus 4 Bus 5 Bus 6 ERCOT WGR Bus kV 34.5kV Collector System 34.5kV 69kV 69kV Point Of Interconnection PMU

32 Weak System Panhandle Area No conventional generation, very little load Far from the rest of system (synchronous units) Dynamics dominated by power electronics (wind plants, SVC.) A large amount of wind units. Disturbances occurring when the weighted short circuit ratio is below 1.5 can cause oscillations, unit trips and and cascading over-voltages in Panhandle. 6

33 Weighted Short Circuit Ratio Limit 33

34 Questions? 34