초록 ▼

Methods and apparatus for operating a combined-cycle power system are provided. The method includes operating the steam turbine, the combustion turbine, and the steam source at steady state operating conditions. Upon sensing a grid frequency deviation away from the standardized grid frequency value,

Methods and apparatus for operating a combined-cycle power system are provided. The method includes operating the steam turbine, the combustion turbine, and the steam source at steady state operating conditions. Upon sensing a grid frequency deviation away from the standardized grid frequency value, determining a current thermal energy capacity of the steam source, determining a rate of frequency recovery available using the current thermal energy capacity of the steam source and a predetermined rate of change of the at least one steam turbine control valve, if the determined rate of frequency recovery available is greater than the grid frequency deviation, mitigating the frequency deviation using the current thermal energy capacity, if the determined rate of frequency recovery available is less than the grid frequency deviation then mitigating the frequency deviation using the current thermal energy capacity substantially simultaneously with a power level increase of the combustion turbine.

대표청구항 ▼

What is claimed is: 1. A method of operating a combined-cycle power system coupled to an electric power grid, the combined-cycle system including at least one electric power generator, a steam turbine coupled to the at least one electric power generator, a combustion turbine coupled to the at least

What is claimed is: 1. A method of operating a combined-cycle power system coupled to an electric power grid, the combined-cycle system including at least one electric power generator, a steam turbine coupled to the at least one electric power generator, a combustion turbine coupled to the at least one electric power generator, and a steam source having a thermal energy reservoir, the thermal energy reservoir being in flow communication with the steam turbine via at least one control valve, said method comprising: operating the steam turbine at a first electric power output, operating the combustion turbine at a first electric power output, and operating the steam source at a first thermal energy level, the steam turbine having at least one control valve in a first position, the combustion turbine having at least one air inlet guide vane in a first position, the steam turbine and the combustion turbine being synchronized to an operating frequency of the grid, so that the steam turbine, the combustion turbine, and the grid are operating at a frequency substantially similar to a standardized grid frequency value; and upon sensing a grid frequency deviation away from the standardized grid frequency value, then: determining a current thermal energy capacity of the thermal energy reservoir; determining a rate of frequency recovery available using the current thermal energy capacity of the thermal energy reservoir and a predetermined rate of change of the at least one steam turbine control valve; if the determined rate of frequency recovery available is greater than the grid frequency deviation and a predetermined recovery period then, moving the at least one steam turbine control valve to a second position thereby inducing a thermal energy transfer between the thermal energy reservoir and the steam turbine, moving the thermal energy reservoir energy level to a second energy level, thereby facilitating a predetermined rate of a grid frequency recovery for a predetermined period of time, the predetermined rate of frequency recovery being substantially uniform; and if the determined rate of frequency recovery available is less than the grid frequency deviation and a predetermined recovery period then, substantially simultaneously moving the at least one combustion turbine air inlet guide vane to a second position and the at least one steam turbine control valve to a second position thereby changing a power level output of the combustion turbine, inducing a thermal energy transfer between the thermal energy reservoir and the steam turbine, moving the thermal energy reservoir energy level to the second energy level, and changing the power output level of the combustion turbine, thereby facilitating a predetermined rate of a grid frequency recovery for a predetermined period of time, the predetermined rate of frequency recovery being substantially uniform. 2. A method in accordance with claim 1 wherein moving the at least one steam turbine control valve to a second position comprises increasing a steam mass flow rate to the steam turbine. 3. A method in accordance with claim 1 wherein moving the at least one steam turbine control valve to a second position comprises decreasing a steam mass flow rate to the steam turbine. 4. A method in accordance with claim 1 wherein moving the at least one combustion turbine inlet guide vane to a second position comprises increasing a combustion gas mass flow rate to the combustion turbine. 5. A method in accordance with claim 1 wherein moving the at least one combustion turbine inlet guide vane to a second position comprises decreasing a combustion gas mass flow rate to the combustion turbine. 6. A method in accordance with claim 1 wherein moving the thermal energy reservoir energy level to a second energy level comprises decreasing and subsequently increasing a steam pressure within the steam source. 7. A method in accordance with claim 1 further comprising adjusting a steam turbine inlet temperature set point to a temporary temperature excursion limit selected to facilitate the predetermined rate of the grid frequency recovery for a predetermined period of time, the predetermined rate of frequency recovery being substantially uniform. 8. A method in accordance with claim 1 further comprising adjusting a heat recovery steam generator temperature set point to a temporary temperature excursion limit selected to facilitate the predetermined rate of the grid frequency recovery for a predetermined period of time, the predetermined rate of frequency recovery being substantially uniform. 9. An electric power grid frequency control sub-system for a combined-cycle power system, said control sub-system comprises: a steam turbine comprising a steam flow control valve; a steam source coupled in flow communication with said steam turbine through said control valve, said steam source comprising a thermal energy reservoir; a combustion turbine comprising an inlet guide vane; an electric power generator coupled to at least one of said steam turbine and said combustion turbine, said electric power generator electrically coupled to an electric power grid, a frequency of said generator and the grid being synchronized at an operating frequency of the grid; a controller configured to modulate said steam flow control valve and said inlet guide vane substantially simultaneously to facilitate inducing a predetermined rate of a grid frequency recovery for a predetermined period of time wherein the predetermined rate of frequency recovery is substantially uniform. 10. An electric power grid frequency control sub-system in accordance with claim 9 configured to open said steam control valve in response to a grid under-frequency condition and close said steam control valve in response to a grid over-frequency condition. 11. An electric power grid frequency control sub-system in accordance with claim 9 wherein said controller is configured to determine a current thermal energy capacity of the thermal energy reservoir. 12. An electric power grid frequency control sub-system in accordance with claim 9 wherein said controller is configured to determine a rate of frequency recovery available using the current thermal energy capacity of the thermal energy reservoir and a predetermined rate of change of the at least one steam turbine control valve. 13. An electric power grid frequency control sub-system in accordance with claim 9 wherein said controller is configured to open said guide vane in response to a grid under-frequency condition and close said guide vane in response to a grid over-frequency condition. 14. A combined-cycle power system comprising: a steam turbine comprising a steam flow control valve, said steam turbine coupled to at least one electric generator; a steam source comprising a thermal energy reservoir, said steam source in flow communication with said steam turbine through said steam flow control valve; a combustion turbine coupled to the at least one electric generator said combustion turbine comprising an inlet guide vane; and a controller communicatively coupled to said steam flow control valve, said steam source, and said inlet guide vane, said controller configured to: determine a current thermal energy capacity of the thermal energy reservoir; determine a rate of frequency recovery available using the current thermal energy capacity of the thermal energy reservoir and a predetermined rate of change of the steam turbine control valve; open the inlet guide vane substantially simultaneously with said steam flow control valve in response to a grid under-frequency condition that exceeds the frequency recovery available of the thermal energy reservoir; and close the inlet guide vane substantially simultaneously with said steam flow control valve in response to a grid over-frequency condition that exceeds the frequency recovery available of the thermal energy reservoir. 15. A combined-cycle power system in accordance with claim 14 wherein said steam source comprises a heat recovery steam generator. 16. A combined-cycle power system in accordance with claim 14 wherein said steam turbine, said combustion turbine, and said generator are rotatably coupled together on a common rotatable shaft such that said control valve, said air inlet guide vane, and said controller cooperate to move said control valve and said guide vane toward a substantially open position to accelerate said common rotatable shaft in response to a grid under-frequency condition and toward a substantially closed position to decelerate said common rotatable shaft in response to a grid over-frequency condition. 17. A combined-cycle power system in accordance with claim 14 wherein at least one generator comprises a first generator, said first generator being rotatably coupled to said steam turbine such that said steam turbine control valve facilitates an acceleration and a deceleration of said first generator. 18. A combined-cycle power system in accordance with claim 14 wherein at least one generator further comprises a second generator, said second generator being rotatably coupled to said combustion turbine such that said combustion turbine air inlet guide vane facilitates an acceleration and a deceleration of said second generator. 19. A combined-cycle power system in accordance with claim 14 wherein if the determined rate of frequency recovery available is greater than the grid frequency deviation and a predetermined recovery period then, moving the at least one steam turbine control valve to a second position thereby inducing a thermal energy transfer between the thermal energy reservoir and the steam turbine, moving the thermal energy reservoir energy level to a second energy level, thereby facilitating a predetermined rate of a grid frequency recovery for a predetermined period of time, the predetermined rate of frequency recovery being substantially uniform. 20. A combined-cycle power system in accordance with claim 14 wherein if the determined rate of frequency recovery available is less than the grid frequency deviation and a predetermined recovery period then, substantially simultaneously moving the combustion turbine air inlet guide vane to a second position and the steam turbine control valve to a second position such that a power level of each of the CTG and the STG are ramped substantially simultaneously to a power level determined to facilitate a predetermined rate of a grid frequency recovery for a predetermined period of time, the predetermined rate of frequency recovery being substantially uniform.