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QSE Managers Working Group October 12, 2010 Base Point Deviation Issues – Short Term and Long Term Solutions Nodal Settlement & Billing Group. Overview Proposal for Interim Solution Proposed options for Post Go-Live. Base Point Deviation – Overview of Issue. - PowerPoint PPT Presentation
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QSE Managers Working GroupOctober 12, 2010
Base Point Deviation Issues – Short Term and Long Term SolutionsNodal Settlement & Billing Group
Base Point Deviation – Overview of Issue
OverviewProposal for Interim SolutionProposed options for Post Go-Live
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Base Point Deviation – Overview of Issue
During the Market Trials phase of the ERCOT Nodal Market, Market Participants and ERCOT personnel became aware that when SCED runs at shorter intervals than every five (5) minutes, it is possible for Resources to receive Base Point Deviation charges, although the Resource may have followed their instructed Base Points based on the Normal Ramp Rate.
Settlement issue only (not an operational issue / no change required to operations)
Within settlements, the protocol-defined AABP calculation assumes that every SCED Base Point is achievable and makes no accommodations for a shortened SCED interval.
The result is an AABP value that is skewed high, which can result in Base Pont Deviation penalties for under-generation.
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Base Point Deviation – Example of Short SCED intervals
SCED IntBase Point Y
(Current SCED)Base Point Y-1
(Previous SCED) Telemetered GenSCED Int (seconds) AABP
TWTG (SCED weighted)
120 120
y1 120 120 120 60 8 8
y2 270 120 150 60 13 9
y3 300 270 180 60 19 11
y4 330 300 210 60 21 13
y5 360 330 270 120 46 32
y6 420 360 360 180 78 63
y7 470 420 404 120 59.33333333 50.93333333
y8 470 470 430.4 120 62.66666667 55.62666667
y9 470 470 446.24 120 62.66666667 58.44266667
2570.64
900 369.6666667 301.0026667
92.41666667 75.25066667
Under Over
ramp per minute = 30 MW 95% 87.79583333 97.0375 1.05%
5 MW 91.16666667 93.66666667 5 MW
Min - TWTG 12.54516667 -21.7868333
12.54516667 0
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Base Point Deviation –Proposed Interim Solution
Interim solution for Base Point Deviation (non IRR) – include an exemption for shortened SCED intervals. Settlements would implement by setting the FQDEVFLAG to 3 in intervals with shortened SCED intervals which would exempt all resources.
The question becomes: How short is too short?
Two options:
A defined percentage – if we find a SCED interval that has a duration of less than x% of 5 minutes in the 15-minute settlement interval, then the exemption would apply.
A defined number – if the 15-minute settlement interval contains greater than x number of complete SCED intervals, then the exemption would apply. (Not including partial SCED intervals)
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Base Point Deviation – Long Term Solutions
Proposal A:
The first alternative modifies the AABP calculation by incorporating a methodology to derive what the Base Point should have been for a shortened SCED interval. The derived Base Point is utilized in the AABP calculation rather than the 5-minute based SCED Base Point. Proposal B:
The second alternative modifies the AABP calculation by using the data inputs calculated for the GREDP calculations. The GREDP data inputs are on a 5-minute clock basis and would not require the time-weighting and averaging that is currently part of the AABP calculation. Therefore, use of the GREDP data avoids the issue of shortened SCED intervals.
Both options require system change for settlements.
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Base Point Deviation – Proposal A: Derived Base Point Inputs
AABP = [(BPSETy - TELGEN (y-1)) / 300* TLMPy ] + TWAR BPSETy = TELGENy-1 + ( (BPy - TELGENy-1)/300 * TLMPy ) Where: TWAR = ((ARI y * TLMP y) / ( TLMP y) {no proposed change}
TELGENy-1 = Telemetered Generation during the prior SCED interval TELGENy = Telemetered Generation during the current SCED interval TLMP = Duration of SCED interval in seconds (BPy - TELGENy-1) / 300 = Using SCED data (which is based on the Normal Ramp Rate for the Resource) this derives a MW/second ramp rate. This value is applied against the number of seconds in the shortened SCED interval to determine the “achievable” change in generation for that shortened SCED interval.
y
y
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Base Point Deviation – Proposal A: Derived Base Point
Once you alter the input AABP, the remainder of the formula is the same. TWTG becomes the incremental difference between the starting and ending Generation in the settlement interval.
Over Generation:BPDAMT q, r, p= Max (0, RTSPP p) * Max [0, (TWTG q, r, p – ¼ * Max (((1 + K1) * AABP q, r, p), (AABP q, r, p + Q1)))]
Where:TWTG = ( (TELGENy - TELGEN(y-1) )) / 4 K1 = 5 % Q1 = 5 MW
Under Generation:BPDAMT q, r, p= Max (0, RTSPP p) * Min (1, KP) * Max {0, {Min [((1 – K2) * ¼( AABP q, r, p)) , ¼( AABP q, r, p – Q2 )] – TWTG q, r, p}}
Where:TWTG q, r, p = ( (TELGENy, q, r, p - TELGEN(y-1) q, r, p)) /4
K2 = 5 % Q2 = 5 MW
y
y
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Base Point Deviation – Proposal A: Derived Base Point
SCED Point
BPy
(30 MW/Min Ramp Rate)
TELGENy-
1TLMPy
MW Change(1) BPSETyTELGENy
TWTG(TELGENy - TELGENy-1)
Y1 120 120 60 120
Y2 270 120 60 30 150 150 30
Y3 300 150 60 30 180 180 30
Y4 330 180 60 30 210 210 30
Y5 360 210 120 60 270 270 60
Y6 420 270 180 90 360 360 90
Y7 470(2) 360 120 44 404 404 44
Y8 470 404 120 26.4 430.4 430.4 26.4
Y9 470 430.4 120 15.84 446.24 446.24 15.84
Total 326.24 2450.64 2450.64 326.24
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Base Point Deviation – Proposal B: GREDP Inputs
• This option utilizes the following data which are inputs into GREDP :oAVGBP_5MoAVG_REG_INST_5MoAVG_REGUP_5MoAVG_REGDN_5MoAVGMW_5M
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Base Point Deviation – Proposal B: GREDP Inputs
AABP q, r, p, i = AVGBP q, r, p, i + TWAR q, r, p, i
Where:
AVGBP q, r, p, i = (AVGBP y + AVGBP y-1 + AVGBP y-2)/3
TWAR q, r, p, i = (AVGREG y + AVGREG y-1 + AVGREG y-2)/3
y = 5-minute clock intervali = 15-minute settlement interval
Formula Variables to GREDP translation:AVGBP = AVGBP_5MAVGREG = AVG_REG_INST_5M = AVG_REGUP_5M - AVG_REGDN_5M
y
y
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Base Point Deviation – Proposal B: GREDP Inputs
Once you alter the input AABP, the remainder of the formula is the same. TWTG becomes the average telemetered generation for each 5-minute clock interval in the settlement interval.
Over Generation:BPDAMT q, r, p= Max (0, RTSPP p) * Max [0, (TWTG q, r, p – ¼ * Max (((1 + K1) * AABP q, r, p), (AABP q, r, p + Q1)))]
Where:TWTG = ( ( AVGTG q, r, p, i)/3)) * ¼
K1 = 5 % Q1 = 5 MW
Under Generation:BPDAMT q, r, p= Max (0, RTSPP p) * Min (1, KP) * Max {0, {Min [((1 – K2) * ¼( AABP q, r, p)) , ¼( AABP q, r, p – Q2 )] – TWTG q, r, p}}
Where:TWTG q, r, p = (( AVGTG q, r, p, i)/3)) * ¼ K2 = 5 % Q2 = 5 MW
Formula Variables to GREDP translation:AVGTG = AVGMW_5M
i
i
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Base Point Deviation – Proposal B: GREDP Inputs
5-Min Clock
IntervalAvg MW
Avg Base Point
(AVGBP)
Avg Reg Instruction(AVGREG)
2:35:00 336.81 352.89 15.13
2:40:00 334.69 352.89 11.02
2:45:00 336.40 352.89 9.17
Total 1007.90 1058.70 35.32
Under
95% 346.44
5MW 359.67
Min(Under)-TWTG 2.61Deviation MWh 2.61
Over
1.05 382.91
5MW 369.67
TWTG-Max(Over) -11.73Deviation MWh 0
364.67 = Average BP + Average Regulation Instruction / 3335.97 = Average MW output / 3
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