Method for shutting down a gas turbine and a steam turbine of a combined cycle power plant at the same time

Abstract

A method for operating a combined cycle power plant, wherein the combined cycle power plant has a gas turbine and a steam turbine and also a shutting-down device, and wherein, for shutting down the gas turbine and the steam turbine, the gas turbine and the steam turbine are operated within a time window that extends from the beginning of the shutting-down procedure at a first time to the falling of the steam temperature to a lower limit value at a second time by the shutting device in such a way that the gas turbine and the steam turbine are relieved substantially at the same time and the block power falls to zero, thermal energy that is stored in the combined cycle power plant preventing immediate falling of a steam temperature to operation below a minimum power output of the gas turbine within the time window.

Claims

1. A method for shutting down a combined cycle power plant, wherein the combined cycle power plant comprises a gas turbine and a steam turbine, the method comprising: operating the gas turbine and the steam turbine within a time window that extends from a first time to a second time; beginning a shutdown procedure of the combined cycle power plant at the first time; decreasing a steam temperature during the time window such that the steam temperature reaches a lower limit value at the second time; decreasing an output power of the gas turbine at the first time; decreasing an output power of the steam turbine at the first time; ceasing operation of the gas turbine at the second time such that the output power of the gas turbine is zero at the second time; ceasing operation of the steam turbine at the second time such that the output power of the steam turbine is zero at the second time; wherein ceasing operation of the gas turbine and ceasing operation of the steam turbine reduces an output power of the combined cycle power plant to zero.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An advantageous embodiment of the connecting element according to the invention is explained below on the basis of the accompanying schematic drawings, in which:

(2) FIG. 1 shows a schematic representation of a combined cycle power plant,

(3) FIG. 2 shows a schematic representation of a controller structure for the combined cycle power plant represented in FIG. 1,

(4) FIG. 3 shows a schematic representation of a further controller structure for the combined cycle power plant represented in FIG. 1,

(5) FIG. 4 shows a schematic representation of a control structure for the combined cycle power plant represented in FIG. 1, and

(6) FIG. 5 shows a schematic representation of the rotational-speed and output-power profile of the combined cycle power plant represented in FIG. 1 during shutting down.

DETAILED DESCRIPTION OF INVENTION

(7) Reference is first made to FIG. 1.

(8) In FIG. 1, a combined cycle power plant 1 is represented.

(9) The combined cycle power plant 1 has in the present exemplary embodiment a gas turbine 2, a steam turbine 3, a condenser 4 and a boiler 5.

(10) The combined cycle power plant 1 may be designed as a multi-shaft plant, in which the gas turbine 2 and the steam turbine 3 respectively drive a generator (not represented). Alternatively, the combined cycle power plant 1 may also be designed as a single-shaft plant, in which the gas turbine 2 and the steam turbine 3 and also a generator are on a common shaft, with a self-synchronizing overrunning clutch for decoupling being additionally provided.

(11) In normal operation, air and fuel are fed to the gas turbine 2. The hot exhaust gases of the gas turbine 2 are fed via an exhaust-gas line 14 to the boiler 5 for generating steam and are discharged via an outlet 15. Steam from the boiler 5 is fed via a steam line 16 to the steam turbine 3 and is expanded there. Via a further steam line 17, the expanded steam is fed to the condenser 4, from which condensate is then fed to the boiler 5 via a condensate line 18.

(12) Reference is now additionally made to FIG. 2.

(13) It shows a controller structure for the combined cycle power plant 1 represented in FIG. 1.

(14) The controller structure has a gas-turbine power controller 8 and a steam-turbine power controller 9, where the gas-turbine power controller 8 is assigned to the gas turbine 2, which is symbolized in FIG. 2 by the controlled-system gas turbine 6. The steam-turbine power controller 9 is assigned to the steam turbine 3, which is symbolized in FIG. 2 by the controlled-system steam turbine 7.

(15) As known per se. the output variable of the gas turbine 2 and of the steam turbine 3 is detected as a respective actual value ACT, a control difference is determined from a respective setpoint value SET and actual value ACT and is fed as a system deviation e to the respective gas-turbine power controller 8 and steam-turbine power controller 9. The respective gas-turbine power controller 8 and steam-turbine power controller 9 then transmits a respective manipulated variable u, to which the respective controlled-system gas turbine 6 and controlled-system steam turbine 7 is subjected, in order to ensure a desired power output.

(16) During a shutting-down process, a shutting-down device 13 becomes active. In the exemplary embodiment represented in FIG. 2, the shutting-down device 13 is designed as a setpoint-specifying device 10.

(17) The shutting-down device 13 transmits a shutting-down setpoint-value profile ASV I for the gas turbine 2 and a shutting-down setpoint-value profile ASV II for the steam turbine 3 as respective setpoint values to the gas-turbine power controller 8 and steam-turbine power controller 9. In this case, the shutting-down setpoint-value profile ASV I for the gas turbine 2 and the shutting-down setpoint-value profile ASV II for the steam turbine 3 comprise in the present exemplary embodiment in each case a series of values of decreasing magnitude that are coordinated with one another and transmitted to the gas-turbine power controller 8 and steam-turbine power controller 9 one after the other (e.g. after a respective predetermined time period has elapsed), in order that the gas turbine 2 and the steam turbine 3 are shut down substantially at the same time and/or at the same time t1 (see FIG. 5).

(18) Reference is now additionally made to FIG. 3.

(19) It shows a further controller structure for the combined cycle power plant 1 represented in FIG. 1.

(20) The controller structure represented in FIG. 3 has a shutting-down device 13, which in the present exemplary embodiment may also be designed as a pre-control device 11.

(21) As a result of its respective shutting-down setpoint-value profile ASV I, ASV II, the shutting-down device 13 also transmits a shutting-down pre-control profile AVV I for the gas turbine 2 and a shutting-down pre-control profile AVV II for the steam turbine 3 as respective actuating values s directly to the gas turbine 2 or the controlled-system gas turbine 6 and the steam turbine 3 or the controlled-system steam turbine 7. In this case, the shutting-down pre-control profile AVV I for the gas turbine 2 and the shutting-down pre-control profile AVV II for the steam turbine 3 comprise in the present exemplary embodiment in each case a series of values of decreasing magnitude that are coordinated with one another and transmitted one after the other, in order that the gas turbine 2 and the steam turbine 3 are shut down substantially at the same time t1 (see FIG. 5).

(22) Reference is now additionally made to FIG. 4.

(23) It shows a further control structure for the combined cycle power plant 1 represented in FIG. 1.

(24) The control structure represented in FIG. 4 has a shutting-down device 13, which in the present exemplary embodiment is designed as a control device 12 for controlling the gas turbine 2 and for controlling the steam turbine 3.

(25) The shutting-down device 13 transmits the shutting-down manipulated-variable profile ASG I to the gas turbine 2 or the controlled-system gas turbine 6 and a shutting-down manipulated-variable profile ASG II to the steam turbine 3 or the controlled-system steam turbine 7, in order that the gas turbine 2 and the steam turbine 3 are shut down substantially at the same time t1 (see FIG. 5).

(26) Reference is now additionally made to FIG. 5.

(27) It shows the rotational-speed profile n and the output-power profile P of the combined cycle power plant 1 in a schematic form.

(28) A shutting-down process begins at the time t0. Consequently, at the time t0 the shutting-down device 13 becomes active.

(29) If the shutting-down device 13 is designed as a setpoint-specifying device 10, the shutting-down device 13 transmits the shutting-down setpoint-value profile ASV I for the gas turbine 2 and the shutting-down setpoint-value profile ASV II for the steam turbine 3 as respective setpoint values to the gas-turbine power controller 8 and steam-turbine power controller 9, in order that the gas turbine 2 and the steam turbine 3 are shut down substantially at the same time t1.

(30) If the shutting-down device 13 is designed as a pre-control device 11, the shutting-down device 13 transmits a shutting-down pre-control profile AVV I for the gas turbine 2 and a shutting-down pre-control profile AVV II for the steam turbine 3 as respective actuating values directly to the gas turbine 2 or the controlled-system gas turbine 6 and the steam turbine 3 or the controlled-system steam turbine 7, in order that the gas turbine 2 and the steam turbine 3 are shut down substantially at the same time t1.

(31) If the shutting-down device 13 is designed as a control device 12, the shutting-down device 13 transmits a shutting-down manipulated-variable profile ASG I to the gas turbine 2 or the controlled-system gas turbine 6 and a shutting-down manipulated-variable profile ASG II to the steam turbine 3 or the controlled-system steam turbine 7, in order that the gas turbine 2 and the steam turbine 3 are shut down substantially at the same time t1.

(32) This allows the gas turbine 2 to be shut down at the same time as the steam turbine 3 within a time window that extends from the time t0 to the time t1, i.e. from the beginning of the shutting-down procedure to the falling of the steam temperature to a lower limit value.

(33) Furthermore, the output-power profile P falls to zero within the time window between the times t0 and t1.

(34) This allows the shutting down to be sped up. It is of advantage here, but not a prerequisite, that the gas turbine 2 has high dynamics.

(35) Although the invention has been illustrated more specifically and described in detail by the preferred exemplary embodiment, the invention is not restricted by the examples disclosed and other variations may be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.