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

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

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 at the deadband.

To meet the 5% droop performance, Governors were 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 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.

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 step function. 11,607 MW Total Capacity Identified by PDCWG

members.• 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

59.9

59.9

159

.9259

.9359

.9459

.9559

.9659

.9759

.9859

.99 60

60.0

160

.0260

.0360

.0460

.0560

.0660

.0760

.0860

.09

60.1

MW

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

591324.0

782765.9 MW Response 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

Min

ute

This compares the difference a single 600 MW unit would have experienced as a result of Primary Frequency Response if on-line the first 10 months of 2008 and had margin to move.

6

2008 Jan thru Dec

0

20000

40000

60000

80000

100000

120000

140000

160000

59.9

59.9

159

.9259

.9359

.9459

.9559

.9659

.9759

.9859

.99 60

60.0

160

.0260

.0360

.0460

.0560

.0660

.0760

.0860

.09

60.1

MW


662574.0




MW-Minute Primary Frequency Response of a 600 MW Unit To All Frequency Deviations in 2008

Min

ute

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.

7

2009 Jan thru Dec

0

20000

40000

60000

80000

100000

120000

140000

MW


446244.0




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.

The MW response of the 0.036 db unit decreased 216330.0 MW in 2009 from 2008. This is a 32.645% decrease in movement.

MW-Minute Primary Frequency Response of a 600 MW Unit To All Frequency Deviations in 2009

Min

ute

The MW response of the 0.0166 db unit decreased 201124.4 MW in 2009 from 2008. This is a 22.518% decrease in movement.

8

ERCOT Frequency Profile Comparison

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

On

e M

inu

te O

ccu

ran

ces

2009 2008

525,600 One Minute Periods per Year 2009 Frequency Profile more “Normal” than 2008. Note: 2008 had two months of operation at the lower governor deadband settings (Nov & Dec).

ERCOT Frequency Profile 2008 and 2009

9

ERCOT Frequency Profile Comparison

0

500

1000

1500

2000

2500

3000

3500

4000

4500

59.9

59.9

159

.92

59.9

359

.94

59.9

559

.96

59.9

759

.98

59.9

9 6060

.01

60.0

260

.03

60.0

460

.05

60.0

660

.07

60.0

860

.09

60.1

On

e M

inu

te O

ccu

ran

ces

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

59.9

59.9

159

.92

59.9

359

.94

59.9

559

.96

59.9

759

.98

59.9

9 60

60.0

160

.02

60.0

360

.04

60.0

560

.06

60.0

760

.08

60.0

960

.1

MW

Min

ute

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 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.

Documents

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