Read Microsoft PowerPoint - 06-Power Plant Frequency Response.ppt text version

Power Plant Frequency Response

John Undrill September 2006

FRR is a Balancing Authority Obligatio

But - the response must be produced by the turbines in the Balancing Authority Area Because frequency changes rapidly, a major part of the complete response must be produced in a 10-20 second time frame Therefore - a major part of FRR must be primary response The Primary Controller is the Governor Primary Response is Governor Response

Production of Frequency Response

Frequency Response is produced inherently by governor action If unit is not at maximum governor should respond But governor action may be blocked, overridden or countermanded

Plant physics may require that limits be placed on primary response eg. temperature - hydraulics - drum level control Commercial considerations may inducd limits on primary response eg. valve wear - compensation for foregone revenue

Primary and Secondary Control

Primary - Secondary Control

Primary Control = Governing

Primary - Response

Power increases to equal increased load

Governor Responds to speed change Speed dips when load increases

No change in speed/load reference

Primary Response |

Secondary Response - AGC adjusts speed-load references

Fuel Command

Grid Frequency

Governor Responds to Frequency change

Generator Power Plant Controller Returns Power to Schedule

Primary Control Governor Responds to Frequency change Secondary Control Plant Controller Returns Power to Schedule

Primary and Secondary Response

Primary Response Test No secondary Control Action

Hydro Plant Characteristics

o - Control action involves large pieces of equipment - Temperature is not a factor - Principal limitations are in hydraulics of civil works - Rough running/draft tube stability my limit allowable dispatch ranges - but have little effect on primary response capability

- Surge tank/manifold design may affect primary respo - River hydrology often affects allowable secondary

Steam Plant Characteristics

- Boiler Follow - Older plants

- Primary response is steam turbine response - Steam turbine response can be very fast - 5% in 5 seconds - Useable Primary response is limited by boiler response capability - Plant capability - 5% fast - remainder - 2%/min or less

er - Boiler control must respect dozens of rate limits

mperature stresses, drum level, coal mills, feedwater heating

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- Turbine Follow - Supercritical and older very large plants

- Primary response is boiler response - Turbine valves are used to control steam pressure - not power - Primary response to frequency is very limited and slow - Secondary response is limited by boiler response capability - Plant capability - 0% fast - remainder - 2%/min or less

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- Coordinated Control - Modern / Updated plants

- Primary response is steam turbine response

Main Plant Characteristics

- Primary response of gas turbine is fast - Generally better going up than coming down - Frequently desirable to implement rate limits to manage temperature transients - Plant capability - 10 to 15 percent fast - remainder - 8%/mi

GT - Primary control (governor) acts on GT - ST valves are wide open in economical output range - ST output follows GTs - behind boiler response time consta - GT component of response is fast - ST component of response is slower - Plant capability - 5 to 8 percent fast - remainder - 3 to 5%/m

Gas Turbine Plants

100 sec

Hydro Plants

Large Steam Plants

Summary of FRR Capability

1-3 % per minute 1-3 % per minute 1-3 % per minute

ge Modern Coal 5 % in few seconds ce Thru & Turbine follow Coal 0 % in few seconds er Boiler Follow Coal 5 % in few seconds

ro 5-10 % in 15 seconds

fast over full range

10-15 % in 15 seconds

8 % minute

GT 5 - 8 % in 15 seconds

5-8 % minute

Summary of Operational Realities

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ideal capability overidden by turbine temperature/stress limits drum level control feedwater heater level controls coal feeder/mill limitations ro low head - few limitations high head/underground/pipeline - civil works limitations

concern regarding reduced output economics wear of valves hot gas path exposure due to maneuvering GT GT as in cimple cycle plants

Information

Microsoft PowerPoint - 06-Power Plant Frequency Response.ppt

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