ERCOT Operations Analysis: Impact of Frequency Control During Unit Startup and Shutdown
This presentation by Sandip Sharma discusses ERCOT's expectations regarding resource entities and QSEs during the startup and shutdown of units, emphasizing the importance of proper procedures to avoid performance issues, base point deviation charges, and system-level frequency deviations. The objectives include identifying responsibilities, sequences, and impacts on grid and market operations due to improper unit startup/shutdown.
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IMPACT TO FREQUENCY CONTROL DURING STARTUP AND SHUT DOWN OF UNITS Sandip Sharma ERCOT Operations Analysis 1
Introduction This presentation is intended to explain ERCOT s expectation of the Resource Entities and QSEs during start-up and shut-down of the units based on the ERCOT Protocol, Operating Guides and Business Practice manual. Due to improper start-up and shut-down at the individual Resource level, performance issues and Base Point Deviation Charges. At the system level, ERCOT has experienced frequency deviations and exhaustion of regulating reserves. there have been 2
Objectives At the completion of this course of instruction you will: 1. Identify the QSE s responsibilities during Startup and Shutdown. 2. Identify the correct sequence of generation resource Startup. 3. Identify the correct sequence of generation resource Shutdown. 4. Identify the impact on ERCOT Grid Operations of improper start-up or shut-down of units. 5. Identify the impact on ERCOT Market Operations of improper start- up or shut-down of units. 3
Agenda Definitions Resource Status QSEs responsibility during Start-up Start-up Sequence Start-up issues QSEs responsibility during Shut-Down Shutdown issues Other observed issues Questions 4
Definitions STARTUP The Resource is On-Line and in a start-up sequence and has no Ancillary Service Obligations. This Resource Status is only to be used for Real-Time telemetry purposes; SHUTDOWN The Resource is On-Line and in a shut-down sequence, and has no Ancillary Service Obligations. This Resource Status is only to be used for Real-Time telemetry purposes; GREDP Generation Resource Energy Deployment Performance SCED Security Constrained Economic Dispatch RLC Resource Limit Calculator LSL Low Sustained Limit HSL High Sustained Limit NURR Normal Up-Ramp Rate NDRR Normal Down-Ramp Rate BP Base Point 5
Resource Status Startup and Shutdown Status STARTUP 16 SHUTDOWN - 15 Online Status ONRUC 1 (hour is RUC-committed interval) ONREG 2 (with energy offer curve and providing regulation) ON 3 (online with energy offer curve) ONDSR 4 (dynamically scheduled resources) ONOS 5 (with output schedule) ONOSREG 6 (with output schedule providing regulation) ONDSRREG 7 (dynamically scheduled resource providing regulation) ONOPTOUT 18 (online and the hour is a RUC buy back hour) Offline Status OUT 11 (offline and unavailable) OFFNS 12 (reserved for offline non-spinning) OFF 13 (offline but available) 6
QSEs Responsibility During Start-up Once the generator breaker is closed, QSE must change telemetered Resource Status to STARTUP from OFF. This should be done about a minute prior to SCED run. The QSE should telemeter a Normal Up Ramp Rate value to ERCOT that reflects the MW per minute rate at which the QSE anticipates bringing the Resource On-Line. Low Sustained Limit (LSL) and High Sustained Limit (HSL) should reflect the true capabilities of the Resource (In other words, don t mess with them) ERCOT does not expect the telemetered Ramp Rate value will be exactly correct, but the QSE should update the ramp rate as often as needed during the start-up process to provide a reasonable estimation 7
Start-up Sequence The QSE should align bringing the Resource On- Line after a SCED execution, which takes into consideration the STARTUP status. RLC will calculate Low Dispatch Limit (LDL) as the telemetered real power output plus the five- minute ramping capability of the Resources. RLC will set the High Dispatch Limit (HDL) equal to the Low Dispatch Limit (LDL) 8
Start-up Sequence When SCED observes Resource Status of STARTUP, SCED will issue a Base Point equal to LDL which is equal the current telemetered net real power plus five times normal ramp rate of the Resource During periods in which the Resource has a telemetered Resource Status of STARTUP, the QSE is exempt from GREDP scoring and Base Point deviation charges. Once the Resource has reached a stable operating condition and is ready to be dispatched normally by SCED, the QSE should change the Resource Status to an appropriate online status and begin responding directly to ERCOT dispatch instructions. 9
Observed Issues #1. Too high NURR during start-up GENERATION BASEPOINT DEVIATION RESOURCE STATUS NURR 150 30 120 27 90 24 60 21 30 18 NURR & Status MW 0 15 09:55 10:00 10:05 10:10 10:15 10:20 10:25 10:30 10:35 10:40 10:45 10:50 -30 12 -60 9 -90 6 -120 3 -150 0 10
Observed Issues #2. Too Low NURR during start-up GENERATION BASEPOINT DEVIATION RESOURCE STATUS NURR 510 30 480 450 27 420 390 24 360 330 300 21 270 240 18 NURR & Status 210 180 MW 150 15 120 90 12 60 30 9 0 09:40 09:45 09:50 09:55 10:00 10:05 10:10 10:15 10:20 10:25 10:30 10:35 -30 -60 6 -90 -120 3 -150 -180 -210 0 11
CORRECT STARTUP SEQUENCE GENERATION BASEPOINT DEVIATION RESOURCE STATUS NURR 600 60 565 57 530 54 495 51 460 48 425 45 390 42 355 39 320 36 285 33 NURR & Status MW 250 30 215 27 180 24 145 21 110 18 75 15 40 12 5 9 05:25 05:30 05:35 05:40 05:45 05:50 05:55 06:00 06:05 06:10 06:15 06:20 -30 6 -65 3 -100 0 12
QSEs Responsibility During Shut-Down The QSE will initiate the shut-down sequence by changing the Resource status to SHUTDOWN The QSE should telemeter a Normal Down Ramp Rate value to ERCOT that reflects the MW per minute rate at which the QSE anticipates bringing the Resource Off-Line The QSE should not begin taking the Resource Off-Line until a SCED execution has completed taking into consideration the SHUTDOWN status. 13
Shut-Down Sequence RLC will calculate HDL as the telemetered real power output minus the five-minute ramping capability RLC will set the Low Dispatch Limit (LDL) equal to the High Dispatch Limit (HDL) SCED will issue Base Points equal to the HDL and ramp the resource smoothly down to a Base Point of zero 14
Shut-Down Sequence During the shut-down process when the Base Points issued by SCED is above the Resource s telemetered LSL, the QSE must follow the Base Point instructions issued by SCED For periods in which the SCED Base Point is below the telemetered LSL, the QSE is exempt from Generation GREDP scoring and Base Point deviation charges Once the Resource has reached a real power output level of zero and the generator breaker has been opened, the QSE will change the telemetered Resource Status to an appropriate offline status 15
Observed Issues #1. NDRR not updated accurately during shut-down UDBP BASEPOINT DEVIATION SCED BP RESOURCE STATUS GENERATION NDRR 1000 33 880 30 760 27 640 24 520 21 MW 400 18 NDRR & Status 280 15 160 12 40 9 16:40 16:45 16:50 16:55 17:00 17:05 17:10 17:15 17:20 17:25 17:30 17:35 -80 6 -200 3 16
Observed Issues #2 Improper sequence of shut-down UDBP BASEPOINT DEVIATION SCED BP RESOURCE STATUS GENERATION NDRR 500 20 430 18 360 16 290 14 220 12 NDRR & Status MW 150 10 80 8 10 6 22:10 22:15 22:20 22:25 22:30 22:35 22:40 22:45 22:50 22:55 23:00 23:05 -60 4 -130 2 -200 0 17
CORRECT SHUTDOWN SEQUENCE UDBP SCED BP GENERATION NDRR GENERATION BASEPOINT DEVIATION BASEPOINT DEVIATION RESOURCE STATUS RESOURCE STATUS NDRR 400 25 400 22 375 21 350 22.5 350 20 325 19 300 20 300 18 275 17 250 17.5 250 16 225 15 200 15 200 14 175 13 MW MW NDRR & Status 150 12.5 NDRR & Status 150 12 125 11 100 10 100 10 75 9 50 7.5 50 8 25 7 0 5 0 6 23:00 -25 23:05 23:05 23:10 23:10 23:15 23:15 23:20 23:20 23:25 23:25 23:30 23:30 23:35 23:35 23:40 23:40 23:45 23:45 23:50 23:55 5 23:00 23:50 23:55 -50 2.5 -50 4 -75 3 -100 -100 0 2 18
Other Observed Issues NURR/NDRR telemetry is correct but it is outside the RARF reasonability limit For temporary limitations like configuration change, activation of power augmentation, start second boiler feed-pump, etc. Resource HSLs are not updated to reflect temporary limitations SCED continuously dispatches these Resources economically While SCED dispatches these Resources with temporary limits higher, SCED is also dispatching other more expensive generator lower. This has market impact as well as affects grid frequency and leads to exhaustion of regulation-up service. The impact of these large deviations are similar to what were discussed with Startup and Shutdown 1For additional details on expected actions from a QSE, please see ERCOT and QSE Operations Practices During the Operating Hour Section 3.2 Generation Resource Power Operation. (http://www.ercot.com/content/mktrules/bpm/BP%20ERCOT%20And%20QSE%20Operations%20Practices_v5%205.doc ) 19
Temporary Limitations without AS UDBP SCED BP GENERATION HSL HASL BASEPOINT DEVIATION NURR 700 50 660 40 620 30 580 20 540 10 500 0 460 -10 420 -20 380 -30 NURR/BP Deviation (MW) MW 340 -40 300 -50 Into duct firing mode 260 -60 220 -70 180 -80 140 -90 100 -100 60 -110 20 -120 -20 -130 12:15 12:20 12:25 12:30 12:35 12:40 12:45 12:50 12:55 13:00 13:05 13:10 -60 -140 -100 -150 20
Temporary Limitations with AS UDBP SCED BP GENERATION HSL HASL BASEPOINT DEVIATION NURR 700 50 660 40 620 30 580 20 540 10 500 0 460 -10 420 -20 380 -30 NURR/BP Deviation (MW) MW 340 -40 300 -50 260 Into duct firing mode -60 220 -70 180 -80 140 -90 100 -100 60 -110 20 -120 -20 -130 12:15 12:20 12:25 12:30 12:35 12:40 12:45 12:50 12:55 13:00 13:05 13:10 -60 -140 -100 -150 21
Summary Improper start-up and shut-down impacts Grid Frequency, leads to exhaustion of regulation service and has market impacts What RLC and SCED expects during Start-Up and Shut-Down of units were explained Proper sequence of start-up and shut- down were explained 22
Questions 23
1. The QSEs responsibilities during Startup include: a) about a minute before a SCED run, change Resource Status from OFF to STARTUP b) calculate Low Dispatch Limit (LDL) c) set the High Dispatch Limit (HDL) equal to the Low Dispatch Limit (LDL) d) issue a Base Point equal to LDL which is equal the current telemetered net real power 24
2. When SCED observes a Resource Status of STARTUP on a unit: a) It will issue a Base Point equal to LDL which is equal to current output plus 5 times NURR. b) It will issue a Base Point equal to Normal Down Ramp Rate value. c) It will change the Resource Status to ONLINE. d) It will begin economically dispatching the unit. 25
3. The QSE correct sequence of generation resource Shut-Down is: a) The QSE will initiate the shut-down sequence by changing the Resource status to SHUTDOWN b) The QSE will telemeter a Normal Down Ramp Rate value to ERCOT c) The QSE should not begin taking the resource off-line until a SCED execution d) All of the above 26
4. One impact on ERCOT Grid Operations of improper shut-down of units is: a) Improper shut-down impacts grid frequency b) Off line non-spin is impacted c) Start of HRUC delayed during those hours d) Load resources are incorrectly calculated 27
5. One impact on ERCOT Market Operations of improper start-up of units is: a) Prolonged regulation deployment and impacts system lambda calculation b) DRUC is delayed for those hours c) HRUC is delayed for those hours d) Mid-term load forecast is incorrectly calculated 28
