SCED Power Balance Penalty Curve

Resmi Surendran

Objective

• Explain the Power Balance Penalty Curve

• Discuss the values for the Power Balance Penalty Curve– MW break points

– Penalty for violation up to the MW break point

• Not to discuss the optimal mechanism for setting scarcity pricing.

Power Balance Penalty

• System Lambda is the change in the objective value obtained by relaxing the Power Balance constraint by 1MW

• Power Balance Penalty is the maximum cost paid for one addition/less MW of generation to meet the Power Balance constraint.

SCED Constraints

• Power Balance Constraintsum (Base Point) + under gen slack – over gen slack

= Generation to be dispatched

• Transmission constraintsum( Shift Factor * Base Point) – violation slack ≤ limit

• Ramp Limit constraintLDL ≤ Base Point ≤ HDL

SCED Objective

• Minimize+ Cost of dispatching generation

integral (offer cost * MW dispatched)

+ Penalty for violating Power Balance constraintsum (Penalty cost * violation amount)

+ Penalty for violating transmission constraintsum (Penalty cost * violation amount)

PB Violation with no Transmission Constraints

• Only constraints active will be System demand & ramp

• Given enough SURAMP, PB will not be violated as long as the aggregated offer curve required to meet demand is less than PB penalty

• If PB Penalty is lower than SWCAP then PB will be violated in SCED1 before dispatching Resources on Output Schedule

PB Violation with Transmission Constraints

• Gen with +ive SF (a) SF * TC_Penalty + Offer cost

(b) PB_penatly– If (a) > (b) - moved down for resolving constraints

– If (a) < (b) - moved up for meeting Power Balance

• Example– Violated TC penalty $3500; 0.2 SF; $100 0ffer cost ; $500 PB

penalty

– 1 MW reduction in generation will• reduce TC violation by 0.2 MW

– will reduce objective by 0.2 * 3500 due to reduction in TC violation and $100 by not providing 1MW energy

• violate PB by 1 MW – Will increase objective by 1* $500

Power Balance Penalty Curve - Implementation

• 10 segment step curve

• MW break points– Sets amount violated for a given price

• Penalty for violation up to the MW break point– Sets system lambda for a given amount of violation

Factors affecting Power Balance Violation

• Ramp limited scenarios– Operational Philosophies

– Extend of ramp being reserved for regulation

– Amount of capacity on Output Schedule

– Telemetry errors

• Capacity Scarcity – Operational Philosophies

Current Power Balance Penalty Curve Values

Over Generation Penalty ($/MWh) -3,001 -5,000

MW Cap Segment (MW) 10,000 100,000

Under Generation Penalty ($/MWh) 3,001 5,000

MW Floor Segment (MW) 10,000 100,000

equivalent to having extra capacity for meeting power balance violation at • (+/-) 3001 $/MWh for violated MW from 0MW to 9999.999MW, and • (+/-) 5000$/MWh for violated MW from 10000MW to 99999.999MW

Proposed Power Balance Penalty Curve

MW Price

1 200

5 250

10 300

20 400

30 500

40 1000

50 2250

 100000  3001

Factors Considered

• Extend of regulation that can be sacrificed

• Operational philosophies

• System Wide Offer Cap - $3000

• Interaction with transmission constraints

• Interaction with proxy offer curves

• Market Trials and close loop test results

Future Areas of Improvement for Better Scarcity Pricing

• Prices not reflective of scarcity during UFR Load Resource deployment

• Reduction in prices due to Output Schedule adjustments during Non-Spin deployment from Resources on Output Schedule

• Dependence on MP submitted EOC to set scarcity pricing during Non-Spin and RRS deployment

Appendix

SCED Objective

])(Re**5.0

Re*Pr[

2,,,,,,

,,,,,,,,

tsegofferrtsegofferr

segofferrtsegofferrtsegofferr

sSegDispMWeSlopeEnergyCurv

sSegDispMWiceeEnergyCurv

p

pt

pt

pENG kDnMWEnergySlackUpMWEnergySlactPenaltyCos )(*

tcc

tc WTranSlackMyCostTranPenalt ,, *

Min { Cost of generation dispatch + Sum ( Max Shadow Price * Slack variable)}

+

+

Power Balance Power Balance Penalty Curve valuePenalty Curve value

Max Shadow Max Shadow PricePrice

Generation Generation dispatch costdispatch cost

Slack Slack VariableVariable

Slack Slack VariableVariable

Slack Slack VariableVariable

SCED constraintsPower Balance Constraints:

Transmission Network Constraints:

Resource Constraints:

Ramp Rate Constraints (HDL, LDL):

r

tp

pt

pttr LoadkDnMWEnergySlackUpMWEnergySlacsDispMW )(Re ,

tctcr

trtcr itWTranSlackMsDispMWSF ,,,,, limRe*

tsegofferrtsegofferr izesOfferSegSsSegDispMW ,,,,,, ReRe0

seg

tsegofferrtr sSegDispMWsDispMW ,,,, ReRe

trtrtr HDLsDispMWLDL ,,, Re

Offer Mitigation for SCED2

(1)Cap the Energy Offer Curves at the greater of the Reference LMP at the Resource Node or the Mitigated Offer Cap curve (2) Bound it at the lesser of the Reference LMP at the Resource Node or the Mitigated Offer Floor.

Proxy Offer Curve for Output Schedule

LMP during Congestion

Resource moved down for congestion

LMP

optunitP

]/[$Pr MWhiceOffer unit

][MWPunit

maxPr uniticeOffer

minPr uniticeOffer

minunitP max

unitP

congLMP

congunitP

Lambda

line

lineline SPSFLMP

LMP during Congestion

Resource moved up for congestion

LMP

optunitP

]/[$Pr MWhiceOffer unit

][MWPunit

maxPr uniticeOffer

minPr uniticeOffer

minunitP max

unitP

congLMP

congunitP

Lambda

line

lineline SPSFLMP

Transmission Constraints Penalty Current Values

• Maximum Shadow Price for Transmission Constraints– Base Case:  $5,000/MW

– Generic constraints :  $5,000/MW

– Post Contingency • 345 kV:  $4,500/MW

• 138 kV:  $3,500/MW

• 69 kV:  $2,800/MW