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, there have been
performance issues and Base Point Deviation
Charges.
At the system level, ERCOT has experienced
frequency deviations and exhaustion of regulating
reserves.
2
Objectives
At the completion of this course of instruction you will:
1.
2.
3.
4.
5.
Identify the QSE’s responsibilities during Startup and Shutdown.
Identify the correct sequence of generation resource Startup.
Identify the correct sequence of generation resource Shutdown.
Identify the impact on ERCOT Grid Operations of improper start-up
or shut-down of units.
Identify the impact on ERCOT Market Operations of improper startup 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
QSE’s 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 OnLine 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 fiveminute 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
MW
NURR &
0
09:55
10:00
10:05
10:10
10:15
10:20
10:25
10:30
10:35
10:40
10:45
15 Status
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
210
MW
NURR &
Status
180
150
15
120
90
12
60
30
0
-3009:40
-60
9
09:45
09:50
09:55
10:00
10:05
10:10
10:15
10:20
10:25
10:30
10:35
6
-90
-120
-150
3
-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
33NURR &
250
30 Status
215
27
180
24
145
21
110
18
75
15
40
12
MW
5
-3005:25
9
05:30
05:35
05:40
05:45
05:50
05:55
06:00
06:05
06:10
06:15
06:206
-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
280
18
NDRR &
Status
15
160
12
40
16:40
-80
-200
9
16:45
16:50
16:55
17:00
17:05
17:10
17:15
17:20
17:25
17:30
17:35
6
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
DEVIATION
BASEPOINT
DEVIATION BASEPOINTRESOURCE
STATUS
GENERATION
RESOURCE STATUS
NDRR
NDRR
400
400
MW
MW
22
375
350
350
21
325
300
300
19
275
250
250
17
225
200
200
15
175
150
150
13
125
100
100
11
20
18
16
14
12
10
75
50
50
25
0
0
23:00
23:00
-25
-50
-50
-75
-100
-100
25
22.5
20
17.5
15
12.5
NDRR &
NDRR &
Status
Status
10
9
8
7.5
7
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
23:50
5
6
23:55
23:55
5
2.5
4
3
2
0
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
1
For 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
MW
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
340
-40
300
-50
260
220
Into duct
firing mode
-60
-70
180
-80
140
-90
100
-100
60
-110
20
-120
-2012:15
12:20
12:25
NURR/BP
Deviation
(MW)
12:30
12:35
12:40
12:45
12:50
12:55
13:00
13:05
13:10-130
-60
-140
-100
-150
20
Temporary Limitations with AS
MW
HSL
GENERATION
SCED BP
UDBP
HASL
BASEPOINT DEVIATION
NURR
700
50
660
40
620
30
580
20
540
10
500
0
460
-10
420
-20
380
-30
340
-40
300
-50
260
220
-60
Into duct
firing mode
-70
180
-80
140
-90
100
-100
60
-110
20
-120
-2012:15
12:20
12:25
NURR/BP
Deviation
(MW)
12:30
12:35
12:40
12:45
12:50
12:55
13:00
13:05
13:10-130
-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 shutdown were explained
22
Questions
23
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
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)
b)
c)
d)
Improper shut-down impacts grid frequency
Off line non-spin is impacted
Start of HRUC delayed during those hours
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