Transcript Comparison of Governor Deadband Settings

Comparison of Governor Deadband
& Droop Settings of a Single 600 MW
Unit
A 0.01666 Hz Deadband with a Straight Line
Proportional 5% Droop Curve Compared to a 0.036
Hz Deadband with a “Step” Straight Line
Proportional 5% Droop Curve from the Deadband
Sydney Niemeyer, NRG
February 9, 2010
Governor Settings Prior to November 2008
● 2008 Had Ten Months of Operation with no
Governor setting changes.
 ERCOT Operating Guides called for a maximum
+/-0.036 Hz deadband on Governors.
 5% Droop Setting with no clarification as to
implementation. With or without a step function at
the deadband.
 To meet the 5% droop performance, Governors
were encouraged to “step” into the 5% droop curve
at the deadband.
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Governor Settings After November 3, 2008
● Deadbands were decreased to +/-0.0166 Hz (1 rpm
on a 3600 rpm turbine).
● The Droop curve implemented was a straight line
proportional curve from the deadband eliminating
any “step” function.
● Initially only 4 Unit’s Governors were changed.
Total Capacity of 2486 MW or approximately 82.8
MW/0.1 Hz of Primary Frequency Response.
● The coordinated Boiler Control System
implemented the same Droop curve and deadband
as the turbine Governor.
● Additional Units changed their Governor settings
throughout 2009 and 2010, mostly after July 2009.
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Status as of February 1, 2010
● Units with Governors presently set with an
intentional deadband less than or equal to +/0.01666 Hz and droop curve with no step
function.
 11,607 MW Total Capacity Identified by PDCWG
members.
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1690 MW Lignite
4139 MW Coal
3620 MW Combustion Turbine Combined Cycle
1519 MW Combustion Turbine Simple Cycle
399 MW Steam Turbine – natural gas fired
240 MW Hydro
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MW-Minute Primary Frequency Response of a 600 MW Unit To
All Frequency Deviations During The First 10 Months of 2008
2008 Jan thru Oct
160000
782765.9 MW Response of 0.0166 db
591324.0 MW Response of 0.036 db
120000 This compares the difference a single 600
MW unit would have experienced as a result
100000 of Primary Frequency Response if on-line
the first 10 months of 2008 and had margin
to move.
80000
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20000
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MW Minute
140000
32.38% Increase in MW
movement with
lower deadband.
5 db
2008 MW Response of 0.036
2008 MW Response of 0.0166 db
MW-Minute Primary Frequency Response of a 600 MW Unit To
All Frequency Deviations in 2008
2008 Jan thru Dec
160000
893164.2 MW Response of 0.0166 db
140000
100000
This compares the difference a single 600
MW unit would have experienced as a result
of Primary Frequency Response if on-line all
of 2008 and had margin to move.
80000
60000
40000
20000
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MW Minute
120000
662574.0 MW Response of 0.036 db
34.80% Increase in MW
movement with
lower deadband.
6 db
2008 MW Response of 0.036
2008 MW Response of 0.0166 db
MW-Minute Primary Frequency Response of a 600 MW Unit To All
Frequency Deviations in 2009
2009 Jan thru Dec
140000
692039.8 MW Response of 0.0166 db
100000
80000
60000
446244.0 MW Response of 0.036 db
However, the 692039.8 MW Response of
the 0.0166 db unit is only 29465.8 MW
more than the 2008 MW Response of the
0.036 db unit (662574.0 MW). A 4.45%
increase with the benefit of the improved
frequency profile.
40000
The MW response
The MW response
of the 0.036 db
of the 0.0166 db
unit decreased
unit decreased
216330.0 MW in
201124.4 MW in
2009 from 2008.
2009 from 2008.
This is a 32.645%
This is a 22.518%
decrease in
decrease in
movement.
movement.
20000
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MW Minute
120000
55.08% Increase in MW
movement with
lower deadband.
7 db
2009 MW Response of 0.036
2009 MW Response of 0.0166 db
ERCOT Frequency Profile 2008 and 2009
ERCOT Frequency Profile Comparison
525,600 One Minute Periods per Year
45000
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30000
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20000
15000
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One Minute Occurances
40000
2009 Frequency
Profile more “Normal”
than 2008. Note: 2008
had two months of
operation at the lower
governor deadband
settings (Nov & Dec).
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2009
2008
ERCOT Frequency Profile Had Additional Improvement in December
2009 and January 2010
ERCOT Frequency Profile Comparison
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December 2009
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One Minute Occurances
December 2009 and January 2010 improved over typical (November 2009) performance.
Several additional units changed their deadbands in
4500
December 2009 and January 2010.
4000
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January
2010
November 2009
MW-Minute Primary Frequency Response of a 600 MW
Unit To All Frequency Deviations During January 2010
January 2010 Primary Frequency Response
10000
53656.4
MW Response of 0.0166 db
37384.0
MW Response of 0.036 db
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MW Minutes
7000
As the frequency profile continues to improve, the lower
deadband unit provides 43.538% more MW movement
than the larger deadband unit, but overall MW movement is
less as the frequency deviations decrease in magnitude.
10 db
MW Response of 0.036
MW Response of 0.0166 db
Conclusions
● Clearly the MW-Minute Movement of a Unit with a
lower deadband setting is more than that of a
larger deadband.
● The MW-Minute movement of the lower deadband
has a gradual injection of Primary Frequency
Response compared to the “step” implementation
of the larger deadband.
 Better Unit stability
 Better Frequency stability
● As more Units implement the lower deadband and
non-”step” droop curve, the frequency profile
improves and the total MW-Minute movement of
the grid decreases.
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