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Security Constrained Economic Dispatch Basics

GRID. Security Constrained Economic Dispatch Basics . Eric Jensen. 1 August 2011. Agenda. Day Before Operating Day Activities. Operating Day Activities and SCED. Demonstration. Day After Operating Day Activities - Settlements. Energy Imbalance Market (EIM) Time Line. Operating Day - 1.

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Security Constrained Economic Dispatch Basics

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  1. GRID Security ConstrainedEconomicDispatch Basics Eric Jensen 1 August 2011

  2. Agenda Day Before Operating Day Activities Operating Day Activities and SCED Demonstration Day After Operating Day Activities - Settlements Security Constrained Economic Dispatch Basics - 1 August 2011

  3. Energy Imbalance Market (EIM) Time Line Security Constrained Economic Dispatch Basics - 1 August 2011

  4. Operating Day - 1 Capacity Assessment • Ancillary Service Obligations and Load Forecast Provided to Market Participants • Market Participants Submit Resource Plans, Offer Curves, Ancillary Service Plans, and Load Forecast • Assessment Performed to Determine Sufficient Capacity – Mismatches Addressed by Market Participants Submitting Revised Plans • Market Participants Create Native Load Schedules External to EIM Security Constrained Economic Dispatch Basics - 1 August 2011

  5. Operating Day - 1Market Participant Input How do the inputs discussed here fit in with what WECC is planning? • Resource Plan • Planned MW • Limits (Economic, Emergency) • Ramp Rate Curves • Status • Manual • Available • Self-Dispatched • Unavailable • Supplemental Security Constrained Economic Dispatch Basics - 1 August 2011

  6. Operating Day - 1Market Participant Input • Ancillary Service Plan • Ancillary services are scheduled by resource • Maximum operating limits are adjusted down from maximum economic limits for regulation up, spin, and supplemental • Minimum operating limits are adjusted up from minimum economic limits by regulation down amount. • Participants can create bilateral schedules for ancillary service obligations • Offer Curves • Offer curves are defined by MW and $/MWh pairs • Native Load Schedules (NLS) (NLS processing is not part of SCED) Security Constrained Economic Dispatch Basics - 1 August 2011

  7. Operating Day • Adjustment of Resource Plans and Offer Curves Prior to Operating Hour (If Allowed) • Intra-Day Assessment of Capacity Requirements • Congestion Management through the Activation of Constraints and Dispatch to Relieve Active Constraints • Dispatch of Contingency Reserves • Operating Hour Dispatch (SCED) Security Constrained Economic Dispatch Basics - 1 August 2011

  8. Operating Hour – Security Constrained Economic Dispatch (SCED) Security Constrained Economic Dispatch (SCED) Time Line Security Constrained Economic Dispatch Basics - 1 August 2011

  9. SCED –Inputs and Outputs Security Constrained Economic Dispatch Basics - 1 August 2011

  10. SCED - Input • Current Operating Plan (Participant Supplied) • Planned MW • Limits (Economic, Emergency) • Ramp Rate Curves • Status (Manual, Available, Self-Dispatched, Unavailable, Supplemental) • Ancillary Service Plan (Participant Supplied) • Offer Curves (Participant Supplied) • Schedules (Including Native Load Schedules) • Load Forecast (Losses added) • Activate Constraints (TLRs, RTCA) • Topology and Sensitivity Factors Security Constrained Economic Dispatch Basics - 1 August 2011

  11. SCED – InputTopology and Sensitivity Factors • Topology Processor • Performed either by State Estimation in the EMS or by a separate topology processing engine in the market. • Utilizes current device - breaker status as input Security Constrained Economic Dispatch Basics - 1 August 2011

  12. SCED – InputTopology and Sensitivity Factors • Topology Processor • The device–breaker model contains a set of electrical nodes (enodes) and buses (enodes) • Topology Processor transforms the device – breaker model into a bus – branch model • The result is a set of branches and enodes • A subset of the enodes are pnodes. Pnodes are pricing nodes where LIP’s are computed (typically injection buses) • A collection of pnodes is called an apnode or aggregate pnode Security Constrained Economic Dispatch Basics - 1 August 2011

  13. SCED – InputTopology and Shift Factors • Shift Factor • A shift factor is the fraction of change in generation MW output that will appear on a line or facility • Generation shift factors are used to analyze the effect of generation shifts on MW flows For Example: New Flow on Line = Previous Flow on Line + (Generation Shift Factor * Amount of Generation MW Shift) Security Constrained Economic Dispatch Basics - 1 August 2011

  14. SCED –Objective • Economic Dispatch - Dispatch energy and ancillary services at the lowest cost to consumers • Security Constrained – Reliably serve consumers recognizing any operational limits of generation and transmission facility • Objective: • Minimize Costs (Imports, Constraint Penalty Costs, Ancillary Services) • Maximize Value (Exports, Ancillary Services) • Subject to Constraints (System Power Balance, Resource Limits, Transmission) Security Constrained Economic Dispatch Basics - 1 August 2011

  15. SCED - Output • Dispatch • Lower cost generators are dispatched in preference to higher cost generators • Net Scheduled Interchange (NSI) • Locational Imbalance Price (LIP) • Cost to serve next incremental MW of load at a specific location using the lowest cost of production of all available generation subject to transmission limits • Equal to: • System Energy Price • Transmission Congestion Cost = ∑(Locational Shift Factor * Constraint Shadow Price) Security Constrained Economic Dispatch Basics - 1 August 2011

  16. SCED – OutputLocational Imbalance Price (LIP) • Locational Imbalance Price (LIP) at pnodei is calculated as: • System Energy Price ( ) • Optimal dispatch ignoring congestion and losses • Same price at every pnode (bus) in the market • Sometimes used to price market interchange Security Constrained Economic Dispatch Basics - 1 August 2011

  17. SCED –OutputLocational Imbalance Price (LIP) • Marginal Congestion Price ( ) • Represents price of congestion on binding constraints • Calculated by summing the multiple of the shift factor for the bus to the constraint by the constraint shadow price over all binding constraints • The shift factors are the values calculated early on in the Topology Processor • A positive shift factor for a generator to a branch indicates that increasing generation increases flow on the branch – if the branch is binding, the generator price decreases • A negative shift factor for a generator to a branch indicates that increasing generation decreases flow on the branch – if the branch is binding, the generator price increases Security Constrained Economic Dispatch Basics - 1 August 2011

  18. SCED –OutputLocationalImbalance Price (LIP) • Marginal Congestion Price ( ) (cont.) • Shadow Price - the shadow price for a binding branch is the change in the cost of congestion by increasing the limit on the on the branch by a incremental MW • When there is no congestion, the value is zero Security Constrained Economic Dispatch Basics - 1 August 2011

  19. SCED Energy Imbalance Market (EIM) Market Key Features • Energy Imbalance = Actual Production or Usage – Scheduled Production or Usage • Native Load Scheduling (NLS) – Participants may carry their own load and avoid price exposure • Locational Imbalance Price (LIP) - Cost to serve next incremental MW of load at a specific location using the lowest cost of production of all available generation subject to transmission limits • Ancillary Services scheduled not market cleared – System handles deployment • Real-time market - Cost of commitment not considered Security Constrained Economic Dispatch Basics - 1 August 2011

  20. SCED – Demonstration and Examples 6 Bus Model 6 Bus Model A B C F D E Security Constrained Economic Dispatch Basics - 1 August 2011

  21. SCED – Demonstration and Examples Unconstrained – Example 1 Alta Marginal Unit – LIPs Equal to System Marginal Price Marginal Unit Security Constrained Economic Dispatch Basics - 1 August 2011

  22. SCED Unconstrained • No Binding or Violated Constraints • LIP Same at All Pnodes • Single Marginal Unit Setting Price Security Constrained Economic Dispatch Basics - 1 August 2011

  23. SCED – Demonstration and Examples Unconstrained – Example 2 Park City Marginal Unit – LIPs Equal to System Marginal Price Alta Constrained to Lower Operating Limit Marginal Unit Security Constrained Economic Dispatch Basics - 1 August 2011

  24. SCED – Demonstration and Examples Transmission Constraint Binding Marginal Units Security Constrained Economic Dispatch Basics - 1 August 2011

  25. SCED Constrained • Situation Occurs When Operating Constraint is Binding • Price Separation Low and High Side of Constraint • Multiple Marginal Units Setting Price Example: Contingency Analysis detects a violated flowgate. The flowgate is activated for SCED. SCED dispatch with the new constraint and initially solves with the constraint binding. Further dispatch is able to move the flow on the flowgate below the activated limits and the system is unconstrainted. Security Constrained Economic Dispatch Basics - 1 August 2011

  26. SCED – Demonstration and Examples Transmission Constraints (2) Binding Marginal Units Security Constrained Economic Dispatch Basics - 1 August 2011

  27. SCED – Settlements • SCED provides Settlements with: • Dispatch • LIP Pricing • Settlements get additional data passed through SCED: • Actual dispatch • Actual demand • Schedules • Settlements uses LIP to settle against difference between actual dispatch and demand and scheduled dispatch and demand • SCED provides Settlements with curtailed schedule information Security Constrained Economic Dispatch Basics - 1 August 2011

  28. Operating Day + 1 Settlements • Ancillary Service Obligations and Load Forecast Provided to Market Participants • Market Participants Submit Resource Plans, Offer Curves, Ancillary Service Plans, and Load Forecast • Assessment Performed to Determine Sufficient Capacity – Mismatches Addressed by Market Participants Submitting Revised Plans • Market Participants Create Native Load Schedules External to EIM Security Constrained Economic Dispatch Basics - 1 August 2011

  29. SCED – Demonstration and Examples Unconstrained – Example 1 Alta Marginal Unit – LIPs Equal to System Marginal Price Marginal Unit Security Constrained Economic Dispatch Basics - 1 August 2011

  30. SCED - SettlementsUnconstrained – Example 1 Alta has a Native Load Schedule with Sundance to provide 100 MW of Energy at $40/MWh. It also offers energy into the market at $38/MWh. In the Unconstrained – Example 1, Alta cleared 99 MW at $38/MWh Alta EIS = (Actual – Scheduled) * LIP Alta EIS = (99MWh – (-100MWh)) * $38/MWh Alta EIS = $38 (Alta Pays SPP) Sundance EIS = (Actual – Scheduled) * LIP Sundance EIS = (223MWh – (100MWh) * $38/MWh Sundance EIS = $4674 (Sundance Pays SPP) Sundance pays Alta = 100MWh * $40MWh = $4000 Alta makes $3962 – $38*99 = $200 Sundance pays $8674 Security Constrained Economic Dispatch Basics - 1 August 2011

  31. SCED – Demonstration and Examples Unconstrained – Example 2 Park City Marginal Unit – LIPs Equal to System Marginal Price Alta Constrained to Lower Operating Limit Marginal Unit Security Constrained Economic Dispatch Basics - 1 August 2011

  32. SCED - SettlementsUnconstrained – Example 2 Alta has a Native Load Schedule with Sundance to provide 100 MW of Energy at $40/MWh. It also offers energy into the market at $38/MWh. In the Unconstrained – Example 1, Alta cleared 99 MW at $38/MWh Alta EIS = (Actual – Scheduled) * LIP Alta EIS = (20MWh – (-100MWh)) * $25/MWh Alta EIS = $2000 (Alta Pays SPP) Sundance EIS = (Actual – Scheduled) * LIP Sundance EIS = (223MWh – (100MWh) * $25/MWh Sundance EIS = $3075 (Sundance Pays SPP) Sundance pays Alta = 100MWh * $40MWh = $4000 Alta makes $2000 – $38*20 = $1240 Sundance pays $7075 Security Constrained Economic Dispatch Basics - 1 August 2011

  33. SCED – Demonstration and Examples Transmission Constraint Binding Marginal Units Security Constrained Economic Dispatch Basics - 1 August 2011

  34. SCED - Settlements Transmission Constraint Binding Alta has a Native Load Schedule with Sundance to provide 100 MW of Energy at $40/MWh. It also offers energy into the market at $38/MWh. In the Unconstrained – Example 1, Alta cleared 99 MW at $38/MWh Alta EIS = (Actual – Scheduled) * LIP Alta EIS = (88.4MWh – (-100MWh)) * $38/MWh Alta EIS = $440.8 (Alta Pays SPP) Sundance EIS = (Actual – Scheduled) * LIP Sundance EIS = (223MWh – (100MWh) * $38.7/MWh Sundance EIS = $4760.1 (Sundance Pays SPP) Sundance pays Alta = 100MWh * $40MWh = $4000 Alta makes $3559.2 – $38*88.4 = $200 Sundance pays $8760.1 Security Constrained Economic Dispatch Basics - 1 August 2011

  35. SCED – Demonstration and Examples Transmission Constraints (2) Binding Marginal Units Security Constrained Economic Dispatch Basics - 1 August 2011

  36. SCED - Settlements Transmission Constraints (2) Binding Alta has a Native Load Schedule with Sundance to provide 100 MW of Energy at $40/MWh. It also offers energy into the market at $38/MWh. In the Unconstrained – Example 1, Alta cleared 99 MW at $38/MWh Alta EIS = (Actual – Scheduled) * LIP Alta EIS = (92.7MWh – (-100MWh)) * $38/MWh Alta EIS = $277.4 (Alta Pays SPP) Sundance EIS = (Actual – Scheduled) * LIP Sundance EIS = (223MWh – (100MWh) * $27.9/MWh Sundance EIS = $3431.7 (Sundance Pays SPP) Sundance pays Alta = 100MWh * $40MWh = $4000 Alta makes $3722.6 – $38*92.7 = $200 Sundance pays $7431.7 Security Constrained Economic Dispatch Basics - 1 August 2011

  37. SCED – Settlements • SCED provides Settlements with: • Dispatch • LIP Pricing • Settlements get additional data passed through SCED: • Actual dispatch • Actual demand • Schedules • Settlements uses LIP to settle against difference between actual dispatch and demand and scheduled dispatch and demand • SCED provides Settlements with curtailed schedule information Security Constrained Economic Dispatch Basics - 1 August 2011

  38. SCED – Questions • Questions Security Constrained Economic Dispatch Basics - 1 August 2011

  39. www.alstom.com

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