METHOD FOR CONTROLLING THE OPERATION OF A GAS TURBINE WITH AN AVERAGED TURBINE OUTLET TEMPERATURE

Abstract

A method is disclosed for operating a gas turbine having a compressor, a combustor, a turbine downstream of the combustor, and a total number of turbine outlet temperature measurements. The method includes locally measuring the turbine outlet temperature of the turbine with the turbine outlet temperature measurements of the respective turbine, and averaging measured temperatures of the selected turbine outlet temperature measurements to obtain an average turbine outlet temperature. The gas turbine operation is controlled depending on the determined average turbine outlet temperature.

Claims

1. Method for operating a gas turbine having a compressor, a combustor, a turbine downstream of the combustor, and a total number of turbine outlet temperature measurements, the method comprising: measuring the turbine outlet temperature of the turbine with the turbine outlet temperature measurements of the respective turbine; selecting a number of turbine outlet temperature measurements which is smaller than a total number of the turbine outlet temperature measurements; averaging the measured temperatures of the selected turbine outlet temperature measurements to obtain an average turbine outlet temperature (TAT AVG); and controlling the operation of the gas turbine in dependence of the average turbine outlet temperature (TAT AVG).

2. Method as claimed in claim 1, burners of the combustors upstream of the turbine are in operation.

3. Method as claimed in claim 1, wherein turbine outlet temperature measurements with specified data quality are identified, and in that the average turbine outlet temperature (TAT AVG) is averaged based on a number of turbine outlet measurement values with specified data quality which is smaller than the total number of turbine outlet temperature measurements with geed-the specified data quality.

4. Method as claimed in claim 1, wherein a proper subset of the turbine outlet temperature measurements is selected for obtaining the average turbine outlet temperature (TAT AVG) wherein a proper subset of turbine outlet temperature measurements comprises: the turbine outlet temperature measurements with highest measurement values.

5. Method as claimed in claim 1, wherein a proper subset of the turbine outlet temperature measurements is selected for obtaining the average turbine outlet temperature (TAT AVG), and a proper subset consists of: an i highest to the j highest turbine outlet temperature measurements, wherein i, and j are natural numbers, i is 2 or larger than 2, j is equal or larger to i, and i and j are smaller than the total number of outlet temperature measurements.

6. Method as claimed in claim 1, wherein the controller has a clock and that-for each turbine outlet temperature, mesurement, a temperature difference between an actual measured value and the average turbine outlet temperature (TAT AVG) of previous controller cycle is calculated, and wherein only measurement values with a temperature difference which is below a maximum temperature deviation are selected for averaging the turbine outlet temperature (TAT AVG) of a current cycle.

7. Method as claimed in claim 1, wherein the averaging is carried out over a number of controller cycles comprising the following steps: a) setting an average turbine outlet temperature variable to zero, assigning the selected turbine outlet temperatures measurements to obtain the average turbine outlet temperature (TAT1 AVG) to a summing list, and in each cycle; b) determining the maximum of a turbine outlet temperature measurements which are on the summing list; c) adding the measurement value of the determined maximum turbine outlet temperature to the average turbine outlet temperature variable; d) removing the determined maximum turbine outlet temperature measurement from the summing list; e) repeating steps b) to d) for a specified number of times, or until the summing list is empty and f) dividing the average turbine outlet temperature variable by the number of measurements added to the average turbine outlet temperature to obtain the average turbine outlet temperature (TAT AVG).

8. Method as claimed in claim 1, wherein the averaging is carried out over a number of controller cycles comprising the following steps: a) setting an average turbine outlet temperature variable to zero, assigning the selected turbine outlet temperatures measurements to obtain the average turbine outlet temperature (TAT1 AVG) to a summing list, and in each cycle; b) determining the maximum of the turbine outlet temperature measurements which are on the summing list; c1) continuing with step d) if it is one of a first to m-th time that a maximum turbine outlet temperature measurement has been detected in the number of controller cycles for averaging, wherein m is a natural number smaller than the number of turbine outlet temperatures measurements on the summing list; c2) adding the measurement value of the determined maximum turbine outlet temperature to the average turbine outlet temperature variable; d) removing the determined maximum turbine outlet temperature measurement from the summing list; e) repeating steps b) to d) for a specified number of times, or until the summing list is empty; and f) dividing the average turbine outlet temperature variable by the number of measurements added to the average turbine outlet temperature to obtain the average turbine outlet temperature (TAT AVG).

9. Method as claimed in claim 1, wherein the average turbine outlet temperature (TAT AVG) is controlled to a set point temperature or the average turbine outlet temperature (TAT AVG) is used to control the combustor temperature to a set point temperature with a closed loop control using the fuel flow to the combustor as correcting variable.

10. Method as claimed in claim 1, wherein all available turbine outlet temperatures measurements are used for calculating the average turbine outlet temperature (TAT AVG) for operation of the gas turbine below a relative load limit, and the selected turbine outlet temperatures measurements are used for calculating the average turbine outlet temperature (TAT AVG) above the relative load limit of the gas turbine.

11. Method as claimed in claim 1, wherein the measurement values of all available turbine outlet temperature measurements are averaged to obtain a reference average turbine outlet temperature and that a protective action of the gas turbine is triggered if a difference between the reference average turbine outlet temperature and the average turbine outlet temperature (TAT AVG) based on the selected turbine outlet temperatures exceeds an allowable deviation.

12. Method as claimed in claim 1, wherein the protective action is one of a deloading, a load shedding, and a trip of the gas turbine.

13. Method as claimed in claim 1, wherein the method it is applied to the gas turbine which is configured as a sequential combustion gas turbine having a first combustor, a first turbine downstream of the first combustor, a total number of first turbine outlet temperature measurements, a second combustor downstream of said first turbine, and a second turbine downstream of said second combustor; and wherein the selected first turbine outlet temperature measurements of the first turbine are averaged to obtain an average first turbine outlet temperature (TAT1 AVG).

14. Method as claimed in claim 1, wherein it is applied to a gas turbine which is configured as a sequential combustion gas turbine having a first combustor, a first turbine downstream of the first combustor, a second combustor downstream of said first turbine, a second turbine downstream of said second combustor, and a total number of second turbine outlet temperature measurements; and wherein selected second turbine outlet temperature measurements of the second turbine are averaged to obtain an average second turbine outlet temperature (TAT2 AVG).

15. Gas turbine comprising: a compressor; a combustor; a turbine downstream of the combustor, a sensor for providing a total number of turbine outlet temperature measurements; and a controller, wherein the controller is configured to carry out a method which includes: measuring the turbine outlet temperature of the turbine with the turbine outlet temperature measurements of the respective turbine; selecting a number of turbine outlet temperature measurements which is smaller than a total number of the turbine outlet temperature measurements; averaging the measured temperatures of the selected turbine outlet temperature measurements to obtain an average turbine outlet temperature (TAT AVG); and controlling the operation of the gas turbine in dependence of the average turbine outlet temperature (TAT AVG).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The disclosure, its nature as well as its advantages, shall be described in more detail below with the aid of the accompanying schematic drawings.

[0052] Referring to the drawings:

[0053] FIG. 1 shows a gas turbine with sequential combustion and a closed loop control circuit for its operation,

[0054] FIG. 2 shows the cross section II-II of the combustor with first turbine outlet temperature measurements,

[0055] FIG. 3 shows the cross section III-III of the second turbine outlet with second turbine outlet temperature measurements,

[0056] FIG. 4 shows a calculation routine for determining the average turbine outlet temperature over a number of y controller cycles.

EMBODIMENTS OF THE DISCLOSURE

[0057] A control scheme of a gas turbine with sequential combustion (known for example for GT24 or GT26) is shown in FIG. 1. The gas turbine 10 comprises a rotor 11, which is surrounded by a concentric casing. A compressor 12 compresses air that enters a first combustor 13 with a first burner 24 through a plenum. Fuel is supplied via a first burner fuel supply 22. The resulting hot gas leaving the first combustor 13 drives a first turbine 14 also called high-pressure turbine. Downstream of first turbine 14 fuel is injected into the gas, which still contains sufficient oxygen for further combustion via a second burner fuel lance 15. The fuel burns in the second combustor 16. The re-heated gas drives a second turbine 17 which is also called low-pressure turbine, and finally exits the gas turbine 10. The first turbine outlet temperature measurement 18 can also be integrated or attached to the second burner fuel lance 15.

[0058] A controller 20, which controls the operation of gas turbine 10, receives measurement values from first turbine outlet temperature measurements 18 being measured at various (e.g. 24) points at the outlet of the first turbine 14. Furthermore, it receives measurement values of second turbine outlet temperature measurements 19 of the second turbine 17 being measured at various points at the outlet of the second turbine 17. Using the measured data the controller 20 controls the operation of the first combustor 13 by means of a first burner fuel control line 21 and the operation of the second combustor 16 by means of a second burner fuel control line 23.

[0059] The gas turbine system can be coupled to a generator via the rotor 11. Typically, a gas turbine 10 further comprises a cooling system for the first turbine 14 and second turbine 17 and sequential combustor arrangement, which is not shown as they are not the subject of this disclosure.

[0060] Exhaust gases leave the second turbine 17. The remaining heat of the exhaust gases is typically used in a subsequent water steam cycle, which is also not shown here.

[0061] An example of an arrangement of the first turbine outlet temperature measurements 18 is shown in FIG. 2. FIG. 2 shows the cross section II-II of FIG. 1 through the annular second combustor 16 with a plurality of second burners 25 upstream of the second combustor 16. In each second burner 25 a first turbine outlet temperature measurement 18 is arranged which is connected to the controller 20.

[0062] An example of an arrangement of the second turbine outlet temperature measurements 19 is shown in FIG. 3. FIG. 3 shows the cross section III-III of FIG. 1 with the outlet of the second turbine 17. A number of second turbine outlet temperature measurement 19 is arranged downstream of the second turbine which is connected to the controller 20. The number of second turbine 17 outlet temperature measurements can for example correspond to the number of second burners 25.

[0063] A calculation routine for determining the average turbine outlet temperature of a first turbine TAT1 AVG in a controller 20 over a number of y controller cycles is shown in FIG. 4. At a first cycle n=1 the maximum turbine outlet temperature measurement max(TAT1i) is determined and stored in an averaging variable also called average turbine outlet temperature variable. For each subsequent controller cycle n until n reaches a number of turbine outlet temperature measurements used for temperature averaging y, the maximum turbine outlet temperature measurement max(TAT1i) among the remaining first turbine outlet temperature measurements 19 is determined and added to the averaging variable. When the controller cycle n=y is reached the value of the average turbine outlet temperature variable is divided by n=y to obtain the average turbine outlet temperature of the first combustor TAT1 AVG. The average turbine outlet temperature of a second turbine can be determined analogously.

[0064] All the explained advantages are not limited to the specified combinations but can also be used in other combinations or alone without departing from the scope of the disclosure. Other possibilities are optionally conceivable, for example the second combustor can have can combustors.

LIST OF DESIGNATIONS

[0065] 10 gas turbine

[0066] 11 rotor

[0067] 12 compressor

[0068] 13 first combustor

[0069] 14 first turbine

[0070] 15 second burner fuel lance

[0071] 16 second combustor

[0072] 17 second turbine

[0073] 18 first turbine outlet temperature measurement

[0074] 19 second turbine outlet temperature measurement

[0075] 20 controller

[0076] 21 first burner fuel control line

[0077] 22 first burner fuel supply

[0078] 23 second burner fuel control line

[0079] 24 first burner

[0080] 25 second burner

[0081] n controller tact

[0082] y number of turbine outlet temperature measurements used for temperature averaging

[0083] TAT AVG average turbine outlet temperature

[0084] TAT1 AVG average first turbine outlet temperature

[0085] TAT2 AVG average second turbine outlet temperature max(TAT1i)