An Introduction to Ancillary Services

Transcription

1 An Introduction to Ancillary Services Pre-conference workshop, IEEE CDC, Dec 2013, Florence, Italy Ancillary Service from Flexible Loads to Help The Electric Grid of the Future Anupama Kowli Department of Electrical Engineering Indian Institute of Technology Bombay, India December 9, 2013

2 Outline Background and motivation Types of Ancillary services Ancillary Services for Frequency Control Services for normal operations Services during contingencies New policies impacting ancillary service providers Alternate framework for characterizing ancillary services A. Kowli Introduction to Ancillary Services IEEE CDC / 28

3 What are Ancillary Services? FERC those services necessary to support the transmission of electric power from seller to purchaser given the obligations of control areas and transmitting utilities within those control areas to maintain reliable operations of the interconnected transmission system similar definitions adopted across other jurisdictions A. Kowli Introduction to Ancillary Services IEEE CDC / 28

4 What are Ancillary Services? FERC those services necessary to support the transmission of electric power from seller to purchaser given the obligations of control areas and transmitting utilities within those control areas to maintain reliable operations of the interconnected transmission system similar definitions adopted across other jurisdictions Not new! Vertically integrated utilities provided these services for many decades. Restructuring necessitated the need to define, measure and pay for ancillary services additional source of revenue for resource owners provision of these services impacts energy and capacity obligations A. Kowli Introduction to Ancillary Services IEEE CDC / 28

5 Need for Ancillary Services Power system operations are challenging because of complexity of large, interconnected power grids constraints on resources just-in-time manufacturing many sources of dynamics and uncertainty obligation to supply electric power of a certain quality defined by the frequency, voltage and reliability A. Kowli Introduction to Ancillary Services IEEE CDC / 28

6 Need for Ancillary Services Power system operations are challenging because of complexity of large, interconnected power grids constraints on resources just-in-time manufacturing many sources of dynamics and uncertainty obligation to supply electric power of a certain quality defined by the frequency, voltage and reliability Ancillary services provide the flexibility needed to control system frequency maintain voltages across the system restart the system in the event of a blackout A. Kowli Introduction to Ancillary Services IEEE CDC / 28

7 Different Ancillary Services Ancillary Services in North American Grids Ancillary Services in European Grids Source: FERC Docket RM Source: EURELECTRIC Tech. Rep A. Kowli Introduction to Ancillary Services IEEE CDC / 28

8 Classification of Ancillary Services System-wide ancillary services Example: scheduling and dispatch, grid loss compensation Resource-based ancillary services ancillary services from resources frequency control services voltage control services restart services primary reserves eg. governor response, load response VAR support black start secondary reserves eg. regulation reserves, spinning reserves higher-level reserves eg. balancing reserves, replacement reserves A. Kowli Introduction to Ancillary Services IEEE CDC / 28

9 ACE(MW) Frequency(Hz) Frequency of an Interconnected Power System System frequency indicates the health of the system ACE Interconnection Control Error & ERCOT Taylor Frequency on August 20, 2010 surplus generation Frequency (Hz) loss of :25 deficit generation ACE (MW) :00 16:00 ACE 17:00 Time ERCOT Taylor Frequency 18:00 19:00 Time Plots adapted from ERCOT Operations Report on the EEA Event of August 20, 2010 A. Kowli Introduction to Ancillary Services IEEE CDC / 28

10 Frequency Control 60.0Hz I System conditions continuously change I Frequency must be kept close to nominal to avoid equipment damage I A hierarchical control architecture is employed to regulate the grid frequency Source: A. Kowli Introduction to Ancillary Services IEEE CDC / 28

11 Ancillary Services for Frequency Control Deployed on various timescales to balance aggregate generation and demand manage power flows on transmission lines A. Kowli Introduction to Ancillary Services IEEE CDC / 28

12 Ancillary Services for Frequency Control Deployed on various timescales to balance aggregate generation and demand manage power flows on transmission lines Examples: PJM regulation and synchronized reserves ERCOT responsive, regulation, balancing, non-spinning and replacement reserves Swiss Grid primary, secondary and tertiary reserves National Grid frequency response, dynamic, fast and operating reserves A. Kowli Introduction to Ancillary Services IEEE CDC / 28

13 Frequency Control during Normal Operations Random fluctuations in load and generation cause system frequency to change continuously power grid limit deviation restore normal activate primary control free reserves take over secondary control free reserves take over Primary control: local governor or load response (instantly) Secondary control: ISO-controlled regulation (seconds) Tertiary control: ISO-dispatched balancing reserves (sub-hourly/hourly) tertiary control A. Kowli Introduction to Ancillary Services IEEE CDC / 28

14 Primary/Frequency Responsive Reserves Local, automatic control action: outputs levels adjusted instantaneously to respond to frequency deviations Providers: generators with governors, motors loads Supply-demand balance is established at new frequency offset Frequency Loss of generation lowers the frequency, droop control increases generation output Power Output A. Kowli Introduction to Ancillary Services IEEE CDC / 28

15 Secondary/Regulation Reserves Centralized, automated control: signals sent to resources to inject/extract power from the grid as needed Providers: generators, loads, batteries A. Kowli Introduction to Ancillary Services IEEE CDC / 28

16 Freeing up the Primary Reserves Secondary reserves change the base output (output at nominal frequency), thus releasing primary reserves Frequency offset Power Output Primary and secondary reserves are deployed to manage fast fluctuations in system conditions A. Kowli Introduction to Ancillary Services IEEE CDC / 28

17 Freeing up the Primary Reserves Secondary reserves change the base output (output at nominal frequency), thus releasing primary reserves Frequency power injected by regulating resources resets the frequency back to nominal offset Power Output Primary and secondary reserves are deployed to manage fast fluctuations in system conditions A. Kowli Introduction to Ancillary Services IEEE CDC / 28

18 Tertiary/Balancing Reserves Balancing/load following reserves or fast energy markets balance out the slower fluctuations in system conditions Deployments are based on centralized control (dispatch) Providers: generators, loads, energy storage Demand (MW) baseline regulation balancing Time Source: Hirst and Kirby, Electric Power Ancillary Services, 1996 A. Kowli Introduction to Ancillary Services IEEE CDC / 28

19 Characterization of Frequency Control Reserves Service Examples Response speed Duration Primary primary reserves in UK, instant seconds to control responsive reserves in minutes service ERCOT Secondary control service Tertiary control service regulation reserves in PJM and ERCOT balancing reserves in ERCOT, PJM real time market within 1 minute up to a few minutes up to several minutes minutes 1 hour to Cycle Time seconds minutes hours A. Kowli Introduction to Ancillary Services IEEE CDC / 28

20 Example: UCTE s Reserves Source: Asko Vuorinen, Frequency Control and Regulating Reserves A. Kowli Introduction to Ancillary Services IEEE CDC / 28

21 Frequency Control during Contingency Operations Equipment failure can cause sudden, large frequency deviations Spinning, non-spinning and supplement reserves are deployed to quickly restore frequency to nominal value power grid limit deviation restore normal activate primary control free reserves take over secondary control free reserves take over Primary control: local governor or load response (instantly) Secondary control: ISO-dispatched contingency reserves (secs--mins) Tertiary control: ISO-dispatched supplemental reserves (sub-hourly--hourly) tertiary control A. Kowli Introduction to Ancillary Services IEEE CDC / 28

22 Characterization of Contingency Reserves Providers: generators, loads, energy storage Service Examples Response speed Spinning reserves synchronized reserves in seconds PJM, fast reserves in to < few National Grid minutes Nonspinning reserves Replacement reserves non-spinning reserves in ERCOT and CAISO replacement reserves in ERCOT, operating reserves in National Grid within a few minutes within an hour Duration minutes hours minutes hours hours to to Cycle Time hours to days hours to days hours to days A. Kowli Introduction to Ancillary Services IEEE CDC / 28

23 Typical Contingency Response in North America Contingency occurs Replacement reserves Spinning and non-spinning reserves Primary reserves Time after contingency Source: Brendan Kirby, Ancillary Services: Technical and Commercial Insights, 2007 A. Kowli Introduction to Ancillary Services IEEE CDC / 28

24 Example: ERCOT s Frequency Control Operations Frequency (Hz) Adjusted responsive reserves MW EEA Level1 Declared Alert Responsive reserves deployed EEA Level1 Terminated Non-spin reserves deployed Reserves (MW) :00 16:00 17:00 Time Time 18:00 Adjusted Responsive Reserves Responsive Reserves Deployed Non-Spin Deployed Frequency 19: Plots adapted from ERCOT Operations Report on the EEA Event of August 20, 2010 A. Kowli Introduction to Ancillary Services IEEE CDC / 28

25 Quality of Ancillary Services Regulation from generators Regulation from flywheels Sources: Kirby ORNL report 2009 Regulation from Alcoa (DR) A. Kowli Introduction to Ancillary Services IEEE CDC / 28

26 Regulation from Limited-Energy Resources Source: A. Kowli Introduction to Ancillary Services IEEE CDC / 28

27 Benefits of Fast Response Source: CAISO presentation to CEC, 2005 Also see: PNNL and KEMA reports A. Kowli Introduction to Ancillary Services IEEE CDC / 28

28 Policy Developments: FERC Order 755 Background: Regulation service providers did not receive payments for accuracy P ayment = capacity payment + payment based on net injection/withdrawl Procurements and deployments of regulating resources are not economically efficient X MW fast regulation Y MW slow regulation, where X < Y Solution: Two-part payment proposed in FERC order 755 released in October 2012 P ayment = capacity payment + performance based payment A. Kowli Introduction to Ancillary Services IEEE CDC / 28

29 Market Landscape for Regulation ERCOT: fast regulation pilot program PJM: two types of regulation services ACE Low pass filter Traditional controller RegA Traditional regulation Usual control signal sent to generators Suitable for slow, ramp-limited resources High pass filter Dynamic controller RegD Dynamic regulation Control signal shortterm zero Suitable for limited energy resources Diagram adapted from PJM Business Practices Manual A. Kowli Introduction to Ancillary Services IEEE CDC / 28

30 The PJM Experiment Source: A. Kowli Introduction to Ancillary Services IEEE CDC / 28

31 Alternate Notion of Ancillary Services Usual characterization of ancillary service focuses on response timescales Alternate characterization: AS(B), where B is the power spectral density B encompasses quantity (and hence, capacity) of service provided as well as bandwidth (indicating its ability to track service requests) Possible extensions: Inclusion of hard constraints of the service provider Incorporation of response characteristics, such as delay A. Kowli Introduction to Ancillary Services IEEE CDC / 28

32 Thanks! Questions? Dr. Anupama Kowli Assistant Professor IIT Bombay, India A. Kowli Introduction to Ancillary Services IEEE CDC / 28