frequency control turbine governor droop nerc requirement droop setting and turbine response...
TRANSCRIPT
Frequency Control
• Turbine Governor Droop• NERC Requirement• Droop Setting and Turbine Response• Governor underperformance• ERCOT Droop• Size does make a difference
Sydney Niemeyer
• Turbine Governor Droop, Speed Regulation or Speed Error are common terms used in describing a turbine’s response to Changes in Interconnection Frequency (speed).
• Not the same as the “Regulation” Ancillary Service Deployment of ERCOT’s Frequency Control System.
• NERC requires all generators greater than 10 MW’s to have an operating governor.
• Droop distributes Frequency regulation to all generators in the interconnect.
• Recommended droop settings of 4 to 5% with a maximum dead band of +/- 0.036 Hz.
Droop Setting Determines Response• 5% Droop: 100% change in generator output for a 5%
change in Frequency or Speed.– A 5% change in frequency, 60 Hz x 0.05 = 3 Hz or for a
2 pole generator, 3600 rpm x 0.05 = 180 rpm.• 4% Droop: 100% change in generator output for a 4%
change in Frequency or Speed.– A 4% change in frequency, 60 Hz x 0.04 = 2.4 Hz or for
a 2 pole generator, 3600 rpm x 0.04 = 144 rpm.• 4% Droop setting is more sensitive (responsive) than the
5% Droop setting.
Example of Expected Response• 150 MW unit at 5% Droop
– 150 / 3 Hz = 50.00 MW/Hz or in tenths of Hz, 5.00 MW/0.1 Hz
– Frequency change from 60.05 to 59.95 should result in the generator increasing output 5.0 MW’s
• 150 MW unit at 4% Droop– 150 / 2.4 Hz = 62.50 MW/Hz or in tenths of Hz,
6.25 MW/0.1 Hz– Frequency change from 60.05 to 59.95 should
result in the generator increasing output 6.25 MW’s
Expected Governor Response
• 5 % Droop:– Unit Net Capability/30 = MW/0.10 Hz
• 4 % Droop:– Unit Net Capability/24 = MW/0.10 Hz
Turbine Governor Response to Frequency - Max Capability 60 MW
-14.0
-12.0
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
59.50 59.60 59.70 59.80 59.90 60.00 60.10 60.20 60.30 60.40 60.50
Meg
aw
att
s
-14.0
-12.0
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
Meg
aw
att
s
5% 4%
4%
4%
5%
5%
Testing Governor Performance
• ERCOT requires off line testing of Steam Turbine governors every 2 years.– Mechanical and Electro hydraulic test forms are in
the Operating Guides.• Combustion Turbines do not have an approved test
procedure.– On Line observation verifies proper performance
for limited frequency range.
59.70
59.72
59.74
59.76
59.78
59.80
59.82
59.84
59.86
59.88
59.90
59.92
59.94
59.96
59.98
60.00
60.02
60.04
60.06
60.08
60.10
7:40 7:45 7:50 7:55 8:00 8:05 8:10 8:15 8:20 8:25 8:30 8:35 8:40
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
Hz 400 MW Unit at 55% Throttle Pressure - Boiler Following
7/18/01
400 MW Unit at 55% Throttle Pressure - Boiler Following
• Base Load with output limited by Exhaust Temperature – Small governor response then reverses and reduces output.
• Pre-Selected Load set-point, limited by Exhaust Temperature – some governor response within Load set-point dead-band.
• Partial Load, not controlling to a load set-point – Full governor response.
Droop Underperformance due to Unit Control Mode – Combustion Turbine
Control Mode of Combustion Turbine May Limit Governor Response
3600 RPM ReferenceActual Shaft Speed
Exhaust Temperature Limit
Pre-Select Load Set-point Generator Output MW
Fuel Control Valve
FSR - Full Speed Regulation
Speed Error
Pre-Select Control Mode
Droop Setting
Combustion Turbine in Pre-Select Mode – Limited Governor Response
Combustion Turbine in Partial Load Mode – Full Governor Response
59.80
59.82
59.84
59.86
59.88
59.90
59.92
59.94
59.96
59.98
60.00
60.02
60.04
60.06
60.08
60.10
17:40 17:45 17:50 17:55 18:00 18:05 18:10 18:15 18:20 18:25 18:30 18:35 18:40
0
4
8
12
16
20
24
28
32
36
40
44
48
52
56
60
Hz GBY 82
7/18/02 Unknown External Unit Trip
GBY 82
QSE - REI
0.00Performance at Point BGreater than 0.64 = Passing
59.80
59.82
59.84
59.86
59.88
59.90
59.92
59.94
59.96
59.98
60.00
60.02
60.04
60.06
60.08
60.10
17:40 17:45 17:50 17:55 18:00 18:05 18:10 18:15 18:20 18:25 18:30 18:35 18:40
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
Hz SJS 1
7/18/02 Unknown External Unit Trip
SJS 1QSE - REI
-0.03
59.80
59.82
59.84
59.86
59.88
59.90
59.92
59.94
59.96
59.98
60.00
60.02
60.04
60.06
60.08
60.10
19:50 19:55 20:00 20:05 20:10 20:15 20:20 20:25 20:30 20:35 20:40 20:45 20:50
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Hz SJS 2
7/16/02 Unknown External Unit Trip
SJS 2QSE - REI
0.02
ERCOT System Droop
• Unit mix determines Frequency Response– Possible Combination
% ResponseMW Droop MW/0.1 Hz
Nuclear 4700 100 0Wind 200 100 0
Combined Cycle CT 6000 55 19Solid Fuel Fully Loaded 11300 51 38
Steam Turbine 12000 6.2 390
Total 34200 13.89 446Spinning 3000
Total On-Line Capacity 37200
ERCOT Load Contributes to System Droop
• As Frequency decreases, load decreases. As Frequency increases, load increases.– Droop contribution of load 0.266 %/MW of ERCOT Load,
in MW/0.1 Hz.• 34,700 MW Load x 0.00266 = 92.3 MW/0.1Hz.
– Total ERCOT Droop includes Turbine droop and Load droop.
• 446 + 92.3 = 538.3 MW/0.1Hz.– For a disturbance of 1250 MW’s and a system response
of 538.3 MW/0.1 Hz, System Frequency would decline by 0.2322 Hz. If starting at 60.00, would result in a minimum frequency of 59.7678 Hz.
ERCOT Load Change vs. Frequency Change
0
100
200
300
400
500
600
700
800
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
Frequency Change
Lo
ad
Ch
an
ge
20000
25000
30000
35000
40000
45000
50000
55000
20,000 MW Load
55,000 MW Load
ERCOT’s Future Droop?
• What will the future unit mix be?– 2000 MW’s of Wind Generation?– Combined Cycle Combustion Turbines want to be
100% loaded on Temperature Control.• What governor response the turbines don’t provide,
the load will (at the expense of larger frequency deviations).
Increasing Wind & Combined Cycle Generation
% ResponseMW Droop MW/0.1 Hz
Nuclear 4700 100 0Wind 1200 100 0
Combined Cycle CT 12000 55 37Solid Fuel Fully Loaded 11300 51 38
Steam Turbine 5000 6.2 202
Total 34200 22.43 276Spinning 3000
Total On-Line Capacity 37200
• Changing the unit mix changes minimum frequency for the same event.– Droop contribution of load 0.266 %/MW of ERCOT Load,
in MW/0.1 Hz.• 34,700 MW Load x 0.00266 = 92.3 MW/0.1Hz.
– Total ERCOT Droop includes Turbine droop and Load droop.
• 276 + 92.3 = 368.3 MW/0.1Hz.– For a disturbance of 1250 MW’s and a system response
of 368.3 MW/0.1 Hz, System Frequency would decline by 0.3394 Hz. If starting at 60.00, would result in a minimum frequency of 59.6606 Hz.
ERCOT System Droop
Firm Load Shedding
• 59.30 Hz – Trips 5% Firm Load• 58.90 Hz – Trips 10% Firm Load• 58.50 Hz – Trips 10% Firm Load
Size Does Make a Difference
• Eastern Interconnect and Western Interconnect Frequency is much more stable than ERCOT’s.
• Based on 2001 Peak Planning Data and Load’s contribution to System Droop:– East 527,000 MW 1370 MW’s/0.1 Hz– West 132,492 MW 344 MW’s/0.1 Hz– ERCOT 53,391 MW 139 MW’s/0.1 Hz
Plot-0
1/31/02 05:17:05 AM 1/31/02 06:17:05 AM60.00 Min(s)
ICCP .HLPFREQ .AV
MAN .MANSYSFREQ .AV
Keystone.KY0 NRRW FREQ .AV
59.95
60
60.05
59.9
60.160.003
59.993
59.963
ICCP .HLPFREQ .AV
MAN .MANSYSFREQ .AV
Keystone.KY0 NRRW FREQ .AV
ERCOT
WEST
EAST
Interconnection
Frequency
ERCOT
EAST
WEST