Combined steam turbine and gas turbine power plant control system

• US 3,879,616 A
• Filed: 09/17/1973
• Issued: 04/22/1975
• Est. Priority Date: 09/17/1973
• Status: Expired due to Term

• Current Assignee: Jack M. Baker, Lawrence R. Mizen, Russell A. Gray, Vladimir T. Dimitroff
• Original Assignee: Jack M. Baker, Lawrence R. Mizen, Russell A. Gray, Vladimir T. Dimitroff
• Inventors: Baker, Jack M., Dimitroff, Vladimir T., Mizen, Lawrence R., Gray, Russell A.
• Primary Examiner(s): Simmons, G. R.
• Application Number:
  US05/398,218
• Time in Patent Office: 582 Days
• Field of Search: 290/2,40,52 60/39.18,105
• US Class Current: 290/40.00R
• CPC Class Codes: F01K 13/02 Controlling, e.g. stopping or starting
• CPC Class Codes: F01K 23/105 Regulating means specially adapted therefor
• CPC Class Codes: Y02E 20/16 Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]

Abstract

A combined cycle power plant has a number of gas turbines each feeding exhaust gas to an associated heat recovery steam generator to generate steam which is supplied to a common header. Provision can also be made for supplementary firing of the heat recovery steam generator to produce additional steam flow. The combined cycle plant also has a steam turbine with a special control system to control steam pressure in the header and to supply the balance of the plant load. An overall combined plant control system assigns load to the individual gas turbine control systems, while the steam turbine control system controls steam pressure in the common header. The steam pressure level setpoint is ramped between selected operating pressure levels when adding or removing load, in accordance with the steam turbine valve positions, in order to achieve optimum operation of the steam turbine. A steam bypass valve control system is used to control pressure in the header during startup, and a supplementary firing control for the heat recovery steam generators may be included to achieve peak loads.

Claims

1. A control system for a combined cycle power plant including at least one gas turbine driving a first load and a steam turbine driving a second load;

a heat recovery steam generator for generating steam from the gas turbine exhaust heat and a steam header interconnecting the heat recovery steam generator and the steam turbine;

the control system further comprising;

a. a gas turbine control system for regulating a fuel supply to the gas turbine in accordance with a load demand setpoint supplied thereto;

b. a steam turbine control system for positioning a steam turbine control valve in response to the steam pressure in said steam header;

c. first and second load transducers for measuring, respectively, the loads on said gas turbine and said steam turbine; and

, d. a combined power plant control system for comparing a load demand setpoint for the combined plant with the sum of the signals from the first and second load transducers to provide a combined plant load error, and to adjust the load setpoint of said gas turbine control system in accordance with the combined plant load error.

2. The control system recited in claim 1 wherein the steam turbine control system regulates the steam pressure in said header by means of said control valve at a plurality of discrete steam pressure levels, said steam turbine control system further including means to change from one discrete pressure level to another in response to the position of the control valve.

3. The control system recited in claim 1 further comprising at least one additional gas turbine driving a load and having a load transducer, said additional gas turbine having a separate gas turbine control system associated therewith to supply fuel to the additional gas turbine in response to a separate load demand setpoint supplied thereto;

and, said combined power plant control system being arranged to compare the load demand setpoint for the combined plant with the sum of the signals from the respective load tranducers to provide the combined plant load error, and to adjust the load setpoints of said respective gas turbine control systems in response to the combined plant load error.

4. The combination according to claim 1 and further including supplementary firing means arranged to burn fuel in the gas turbine exhaust to augment steam generation in the heat recovery steam generator when the gas turbine control system limits further fuel flow to the gas turbine.

5. A control system for a combined cycle plant of the type having at least one gas turbine, a steam turbine, a heat recovery steam gnereator disposed to generate steam from the gas turbine exhaust and a steam header receiving steam from the heat recovery steam generator, said control system comprising:

a control valve for varying the flow of steam through the steam turbine from said steam header, means for sensing the pressure of steam in said steam header and providing an output pressure signal, control means receiving said output pressure signal and positioning said control valve to regulate the pressure in said header about a pressure level setpoint within a selected operating range of the control valve, and means responsive to control valve movement outside of said operating range and operative tO change the pressure setpoint of said control means to a new pressure level.

6. The combination according to claim 5, wherein said control means ramps the pressure setpoint at a selectable rate to a higher pressure setpoint when said control valve opens beyond a selected position.

7. The combination according to claim 5, wherein said control means causes the pressure setpoint to ramp to a selected lower level at a selectable rate when the control valve closes beyond a selected position.

8. The combination according to claim 5, wherein said control means is arranged to change the pressure setpoint to a new pressure level at a rate dependent upon a measured operating condition of the steam turbine other than valve position.

9. The combination according to claim 5, wherein said control system includes a first amplifier arranged to position said control valve in accordance with a selected operating speed of the steam turbine, and a second amplifier responsive to a selected pressure in the steam turbine arranged to limit the output of the first amplifier and thereby override the position of the control valves dictated by said amplifier.

10. A combined cycle power plant and control system comprising:

at least one gas turbine driving an electrical generator, a steam turbine driving an electrical generator and having a control valve for varying the amount of steam flowing through the steam turbine, a heat recovery steam generator disposed to generate steam from the heat of the gas turbine exhaust, a steam header receiving steam from the heat recovery steam generator, a steam turbine control system arranged to regulate the steam pressure in said header by means of said control valve, a gas turbine control system arranged to supply fuel to the gas turbine in accordance with a gas turbine load setpoint supplied thereto, first and second means providing signals responsive respectively to the loads produced by said gas turbine-driven generator and by said steam turbine-driven generator, and a combined plant control system arranged to compare a load demand setpoint for the combined plant with the sum of the signal from said first and second load responsive means and to adjust the load setpoint of said gas turbine control system in response to the combined plant load error.

11. The combination according to claim 10, and further including an additional gas turbine connected to drive an additional electrical generator having third load responsive means and including an additional heat recovery steam generator connected to said steam header, said gas turbine having an additional gas turbine control system associated therewith arranged to supply fuel to the additional gas turbine in response to a second gas turbine load setpoint, and said combined plant control system being arranged to adjust first and second gas turbine load setpoints to said respective gas turbine control systems in response to the combined plant load error.

12. The combination according to claim 10 and further including supplementary firing means associated with said heat recovery steam generator and arranged to burn fuel in the gas turbine exhaust to augment steam generation in the heat recovery steam generator when the gas turbine control system limits further fuel flow to the gas turbine.