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Tests for Reasonable LMPs & Price Validation

Tool Overview

October 27, 2009

NATF

6 Month LMP Posting

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6 Month LMP Posting

5.1 (4) As early as practical, ERCOT shall begin posting of LMPs to Market Participants based on test Resource offer curves submitted to ERCOT by the QSEs to measure the accuracy and stability of the SCED. The minimum time for this posting should be at least six months but may be longer as approved by the TPTF.

Note: Early 2008 both tests for reasonableness and metrics were presented to TPTF

ERCOT Nodal Transition Plan v2.0

References:

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Tests for Reasonable LMPs

1. If LMP > offer price (mitigated, proxy) at maximum limit (HDL) for a Resource, then unit should be dispatched at maximum limit (HDL)

2. If LMP < offer price (mitigated, proxy) at minimum limit (LDL) for a Resource, then unit should be dispatched at minimum limit (LDL) 

3. If LMP = offered price (mitigated, proxy) at dispatched MW point for a Resource, then Resource is marginal

4. Base Points are between HDL and LDL

5. Shadow Price is zero for a transmission constraint which is not binding

6. Shadow Price is non-zero for a transmission constraint which is binding

7. SPP Recalculation 

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Overview of Price Validation ToolOverview of Price Validation Tool

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Market prices are validated for DAM, SCED and SASM;

Price Validation is done for: DAM for each hour of the next operating day. SCED for each dispatch interval and each settlement

interval. Each hour of the SASM if a SASM is run.

Overview of the Price validation tool (PVT)

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Core price validation tests

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Core tests of the price validation (continued)

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Tests of the Price Validation

Settlement Point TypeSettlement Point Type DescriptionDescription

Resource NodeResource Node

RN Resource Node for normal resource

PCCRN Physical Resource Node for combined cycle units

LCCRN Logical Resource Node for combined cycle plant

PUN Private Area Network Resource Node

Load ZoneLoad ZoneLZ Congestion Load Zone

LZ_DC DCTIE Load Zone

HubHubHU HubSH ERCOT_345KV_HUBBUSES_AVG

AH ERCOT_HUB_AVG

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1. 15-minute SPP Recalculation

What?What?

This test will verify that at each time interval, the shadow price for a transmission constraint is correctly calculated based on the binding status of the transmission constraint.

How?How?

i) If the transmission constraint is binding Shadow price is nonzero. ii) If the transmission constraint is not binding Shadow price is zero.

ERROR_FLAGERROR_FLAGBATCH_IBATCH_I

DD CONSTRAINT_NAMECONSTRAINT_NAME LIMITLIMIT POWER _FLOWPOWER _FLOW SHADOW_PRICESHADOW_PRICE0 304769 *BCSPS_DIB138 SRB138 478 478 1329.1711 304769 BGLK4A-L_NORTMC 166 166 0

0 304769DCPSRKC5_TURTCR138 VERDCR138 128 128 504.76

0 304769DCPSRKC5_DPW138 GYR138 178 166 0

22 304769 FTSW2A-BARL2A 338 300 345.12

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2. Shadow price check

Tests of the Price Validation

What?What?

This test will verify that the correct number of marginal resources or Transmission Constraint Management (TCM) penalty prices are setting price in each interval given the number of binding or overloaded transmission constraints.

How?How?

i) If there are n transmission constraints binding at least (n + 1) marginal resources setting price. ii) If there are n overloaded transmission constraints at least n transmission constraint shadow prices that are set to that constraint’s TCM penalty price.

Output?Output?

All instances in which the correct number of marginal resources and TCM penalty prices cannot be identified will be flagged for further review.

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3. Marginal Units Check

Tests of the Price Validation

What?What?

This test will verify that committed resources are scheduled correctly based on the resource’s offer price, the LMP at its location.

(1) Base Points are between HDL and LDL(2) If LMP > offer price at maximum limit (HDL) for a Resource, then unit should be dispatched at maximum limit (HDL)(3) If LMP < offer price at minimum limit (LDL) for a Resource, then unit should be dispatched at minimum limit (LDL)  (4) If LMP = offered price at dispatched MW point for a Resource, then Resource is marginal

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4. Dispatch Consistency Check

Tests of the Price Validation

MWhLDL HDL

LMP

MWhLDL HDL

LMP

MWhLDL HDL

LMP

X

Marginal Unit

Base Point

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4. Dispatch Consistency Check

Tests of the Price Validation

Example: Identify extreme high prices, low prices, and large changes

in prices from interval to interval. (Note: this is just a warning flag)

ThresholdThreshold(1 interval)(1 interval)

Interval to intervalInterval to interval(2 intervals)(2 intervals)

OscillatingOscillating(3 intervals)(3 intervals)

LMPsLMPs

Shadow pricesShadow prices

Shift factorsShift factors

Base pointsBase points

threshold limit

Threshold = 30

$/MWhr interval to interval

Threshold = 20

$/MWhr oscillating

Threshold = 15

$/MWhr

Tests of the Price Validation

5. High Level Tests

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Thanks!

Questions?