Comparison of Governor Deadband Settings Feb 2010

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A 0.01666 Hz Deadband with a Straight LineProportional 5% Droop Curve Compared to a 0.036

Hz Deadband with a “Step” Straight LineProportional 5% Droop Curve from the Deadband

Comparison of Governor Deadband

& Droop Settings of a Single 600 MW

Unit

Sydney Niemeyer, NRG

February 9, 2010



2

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 atthe deadband.

To meet the 5% droop performance, Governorswere encouraged to “step” into the 5% droop curve

at the deadband.



3

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 eliminatingany “step” function.

● Initially only 4 Unit’s Governors were changed.

Total Capacity of 2486 MW or approximately 82.8MW/0.1 Hz of Primary Frequency Response.

● The coordinated Boiler Control Systemimplemented the same Droop curve and deadbandas the turbine Governor.

● Additional Units changed their Governor settingsthroughout 2009 and 2010, mostly after July 2009.



4

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 stepfunction.

11,607 MW Total Capacity Identified by PDCWGmembers.

• 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



5

2008 Jan thru Oct

0

20000

40000

60000

80000

100000

120000

140000

160000

5 9 . 9

5 9 . 9 1

5 9 . 9 2

5 9 . 9 3

5 9 . 9 4

5 9 . 9 5

5 9 . 9 6

5 9 . 9 7

5 9 . 9 8

5 9 . 9 9 6 0

6 0 . 0 1

6 0 . 0 2

6 0 . 0 3

6 0 . 0 4

6 0 . 0 5

6 0 . 0 6

6 0 . 0 7

6 0 . 0 8

6 0 . 0 9

6 0 . 1

M W

2008 MW Response of 0.036 db 2008 MW Response of 0.0166 db

591324.0

782765.9 MW Res onse of 0.0166 db

MW Response of 0.036 db

32.38% Increase in MW

movement with

lower deadband.

MW-Minute Primary Frequency Response of a 600 MW Unit To

All Frequency Deviations During The First 10 Months of 2008

M i n u t e

This compares the difference a single 600MW unit would have experienced as a result

of Primary Frequency Response if on-linethe first 10 months of 2008 and had marginto move.



6

2008 Jan thru Dec

0

20000

40000

60000

80000

100000

120000

140000

160000

5 9 . 9

5 9 . 9 1

5 9 . 9 2

5 9 . 9 3

5 9 . 9 4

5 9 . 9 5

5 9 . 9 6

5 9 . 9 7

5 9 . 9 8

5 9 . 9 9 6 0

6 0 . 0 1

6 0 . 0 2

6 0 . 0 3

6 0 . 0 4

6 0 . 0 5

6 0 . 0 6

6 0 . 0 7

6 0 . 0 8

6 0 . 0 9

6 0 . 1

M W


662574.0

893164.2 MW Res onse of 0.0166 db


34.80% Increase in MW

movement with

lower deadband.

MW-Minute Primary Frequency Response of a 600 MW Unit To

All Frequency Deviations in 2008

M i n

u t e

This compares the difference a single 600MW unit would have experienced as a result

of Primary Frequency Response if on-line allof 2008 and had margin to move.



2009 Jan thru Dec

0

20000

40000

60000

80000

100000

120000

140000

5 9 . 9

5 9 . 9 1

5 9 . 9 2

5 9 . 9 3

5 9 . 9 4

5 9 . 9 5

5 9 . 9 6

5 9 . 9 7

5 9 . 9 8

5 9 . 9 9 6 0

6 0 . 0 1

6 0 . 0 2

6 0 . 0 3

6 0 . 0 4

6 0 . 0 5

6 0 . 0 6

6 0 . 0 7

6 0 . 0 8

6 0 . 0 9

6 0 . 1

M W


446244.0

692039.8 MW Res onse of 0.0166 db


55.08% Increase in MWmovement withlower deadband.

However, the 692039.8 MW Response of

the 0.0166 db unit is only 29465.8 MWmore than the 2008 MW Response of the0.036 db unit (662574.0 MW). A 4.45%increase with the benefit of the improvedfrequency profile.

The MW responseof the 0.036 db

unit decreased216330.0 MW in2009 from 2008.This is a 32.645%decrease inmovement.

MW-Minute Primary Frequency Response of a 600 MW Unit To All

Frequency Deviations in 2009

M i n u t e

The MW response

of the 0.0166 dbunit decreased201124.4 MW in2009 from 2008.This is a 22.518%decrease in

movement.



ERCOT Frequency Profile Comparison

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

5 9 . 9

5 9 . 9 1

5 9 . 9 2

5 9 . 9 3

5 9 . 9 4

5 9 . 9 5

5 9 . 9 6

5 9 . 9 7

5 9 . 9 8

5 9 . 9 9 6 0

6 0 . 0 1

6 0 . 0 2

6 0 . 0 3

6 0 . 0 4

6 0 . 0 5

6 0 . 0 6

6 0 . 0 7

6 0 . 0 8

6 0 . 0 9

6 0 . 1

O

n e M i n u t e O c c u r a n c e s

2009 2008

525,600 One Minute Periods per Year 2009 FrequencyProfile more “Normal”

than 2008. Note: 2008had two months ofoperation at the lowergovernor deadbandsettings (Nov & Dec).

ERCOT Frequency Profile 2008 and 2009



ERCOT Frequency Profile Comparison

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5 9 . 9

5 9 . 9 1

5 9 . 9 2

5 9 . 9 3

5 9 . 9 4

5 9 . 9 5

5 9 . 9 6

5 9 . 9 7

5 9 . 9 8

5 9 . 9 9 6 0

6 0 . 0 1

6 0 . 0 2

6 0 . 0 3

6 0 . 0 4

6 0 . 0 5

6 0 . 0 6

6 0 . 0 7

6 0 . 0 8

6 0 . 0 9

6 0 . 1

O n e M i n u t e O c c u r a

n c e s

December 2009 January 2010 November 2009

December 2009 and January 2010 improved over typical (November 2009) performance.Several additional units changed their deadbands in

December 2009 and January 2010.

ERCOT Frequency Profile Had Additional Improvement in December

2009 and January 2010



10

MW-Minute Primary Frequency Response of a 600 MW

Unit To All Frequency Deviations During January 2010

January 2010 Primary Frequency Response

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

5 9 . 9

5 9 . 9 1

5 9 . 9 2

5 9 . 9 3

5 9 . 9 4

5 9 . 9 5

5 9 . 9 6

5 9 . 9 7

5 9 . 9 8

5 9 . 9 9 6 0

6 0 . 0 1

6 0 . 0 2

6 0 . 0 3

6 0 . 0 4

6 0 . 0 5

6 0 . 0 6

6 0 . 0 7

6 0 . 0 8

6 0 . 0 9

6 0 . 1

M W M

i n u t e s

MW Response of 0.036 db MW Response of 0.0166 db

53656.4

37384.0



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.



11

Conclusions

● Clearly the MW-Minute Movement of a Unit with a

lower deadband setting is more than that of alarger deadband.

● The MW-Minute movement of the lower deadbandhas a gradual injection of Primary FrequencyResponse compared to the “step” implementation

of the larger deadband. Better Unit stability

Better Frequency stability

● As more Units implement the lower deadband andnon-”step” droop curve, the frequency profile

improves and the total MW-Minute movement ofthe grid decreases.

Comparison of Governor Deadband Settings Feb 2010

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