IMPACT TO FREQUENCY CONTROL DURING STARTUP AND SHUT DOWN OF UNITS Sandip Sharma ERCOT Operations Analysis 1

IMPACT TO FREQUENCY CONTROL DURING STARTUP AND SHUT DOWN OF UNITS

Sandip Sharma ERCOT Operations Analysis

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IntroductionThis 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, there have been performance issues and Base Point Deviation Charges.

At the system level, ERCOT has experienced frequency deviations and exhaustion of regulating reserves.

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ObjectivesAt 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.

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AgendaDefinitionsResource StatusQSEs responsibility during Start-upStart-up SequenceStart-up issuesQSEs responsibility during Shut-DownShutdown issuesOther observed issuesQuestions

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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

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Resource Status

Offline Status OUT – 11 (offline and unavailable) OFFNS – 12 (reserved for offline non-spinning) OFF – 13 (offline but available)

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)

Startup and Shutdown Status STARTUP – 16 SHUTDOWN - 15

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QSE’s Responsibility During Start-upOnce 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

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Start-up SequenceThe 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)

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Start-up SequenceWhen 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.

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Observed Issues #1. Too high NURR during start-up

10

0

3

6

9

12

15

18

21

24

27

30

-150

-120

-90

-60

-30

0

30

60

90

120

150

09:55 10:00 10:05 10:10 10:15 10:20 10:25 10:30 10:35 10:40 10:45 10:50

NURR & Status

MW

GENERATION BASEPOINT DEVIATION RESOURCE STATUS NURR

Observed Issues #2. Too Low NURR during start-up

0

3

6

9

12

15

18

21

24

27

30

-210

-180

-150

-120

-90

-60

-30

0

30

60

90

120

150

180

210

240

270

300

330

360

390

420

450

480

510

09:40 09:45 09:50 09:55 10:00 10:05 10:10 10:15 10:20 10:25 10:30 10:35

NURR & StatusMW


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CORRECT STARTUP SEQUENCE

12

0

3

6

9

12

15

18

21

24

27

30

33

36

39

42

45

48

51

54

57

60

-100

-65

-30

5

40

75

110

145

180

215

250

285

320

355

390

425

460

495

530

565

600

05:25 05:30 05:35 05:40 05:45 05:50 05:55 06:00 06:05 06:10 06:15 06:20

NURR & StatusMW


QSEs Responsibility During Shut-DownThe QSE will initiate the shut-down sequence by changing

the Resource status to SHUTDOWNThe 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.

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Shut-Down SequenceRLC 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

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Shut-Down SequenceDuring 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

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Observed Issues #1. NDRR not updated accurately during shut-down

16

3

6

9

12

15

18

21

24

27

30

33

-200

-80

40

160

280

400

520

640

760

880

1000

16:40 16:45 16:50 16:55 17:00 17:05 17:10 17:15 17:20 17:25 17:30 17:35

NDRR &Status

MW

UDBP SCED BP GENERATIONBASEPOINT DEVIATION RESOURCE STATUS NDRR

Observed Issues#2 Improper sequence of shut-down

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0

2

4

6

8

10

12

14

16

18

20

-200

-130

-60

10

80

150

220

290

360

430

500

22:10 22:15 22:20 22:25 22:30 22:35 22:40 22:45 22:50 22:55 23:00 23:05

NDRR &StatusMW


CORRECT SHUTDOWN SEQUENCE

18

0

2.5

5

7.5

10

12.5

15

17.5

20

22.5

25

-100

-50

0

50

100

150

200

250

300

350

400

23:00 23:05 23:10 23:15 23:20 23:25 23:30 23:35 23:40 23:45 23:50 23:55

NDRR & Status

MW

GENERATION BASEPOINT DEVIATION RESOURCE STATUS NDRR

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

-100

-75

-50

-25

0

25

50

75

100

125

150

175

200

225

250

275

300

325

350

375

400

23:00 23:05 23:10 23:15 23:20 23:25 23:30 23:35 23:40 23:45 23:50 23:55

NDRR &Status

MW


Other Observed IssuesNURR/NDRR telemetry is correct but it is outside the

RARF reasonability limitFor 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 economicallyWhile 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 )

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http://www.ercot.com/content/mktrules/bpm/BP%20ERCOT%20And%20QSE%20Operations%20Practices_v5%205.doc

Temporary Limitations without AS

-150

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

-100

-60

-20

20

60

100

140

180

220

260

300

340

380

420

460

500

540

580

620

660

700

12:15 12:20 12:25 12:30 12:35 12:40 12:45 12:50 12:55 13:00 13:05 13:10

NURR/BPDeviation

(MW)

MW

UDBP SCED BP GENERATION HSL HASL BASEPOINT DEVIATION NURR

Into duct firing mode

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Temporary Limitations with AS

-150

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

-100

-60

-20

20

60

100

140

180

220

260

300

340

380

420

460

500

540

580

620

660

700

12:15 12:20 12:25 12:30 12:35 12:40 12:45 12:50 12:55 13:00 13:05 13:10

NURR/BPDeviation

(MW)

MW

UDBP SCED BP GENERATION HSL HASL BASEPOINT DEVIATION NURR

Into duct firing mode

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SummaryImproper 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

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QuestionsQuestions

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1. The QSE’s 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

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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.

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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

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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

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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

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Documents

IMPACT TO FREQUENCY CONTROL DURING STARTUP AND SHUT DOWN OF UNITS Sandip Sharma ERCOT Operations Analysis 1