JPS6018815B2 - Gas turbine fuel control method and device for combined cycle plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a steam-gas combined cycle plant consisting of a plurality of gas turbines and one steam turbine. The present invention relates to a gas turbine fuel control method for correcting an unbalance when the gas turbine exhaust gas temperature is unbalanced when the gas turbine exhaust gas temperature is unbalanced.

[Background of the invention]

A steam-gas combined cycle plant generally consists of a plurality of gas turbines and boilers and one steam turbine.

Figure 1 shows an example of a combined cycle plant. In the figure, a gas turbine power generation plant consisting of a compressor 1, a combustor 2, a fuel control valve 3, a gas turbine 4, and a generator 5 is arranged in parallel in a plurality of sets (only one set is shown in the drawing). A boiler 8 (only one is shown) is connected to the exhaust side of each gas turbine 4 via an inlet gas damper 6.
power: connected to generate steam using the exhaust gas of the gas turbine 4. Note that 7 is a bypass damper. The steam outlet side of each boiler 8 is connected to one steam header 11 via a boiler outlet valve 10, and a steam turbine 13 is connected to the header 11 via a control valve 12 to drive a generator 14. It looks like this. A condenser 15 is provided on the steam outlet side of the steam turbine 13, and piping is provided so that water is introduced from the condenser 15 to each boiler 8 via a pump P. Further, the steam outlet side of the boiler 8 and the condensate 15 are connected via a pipe having a bypass valve 9. In such a combined cycle plant, the exhaust gas left after driving each gas turbine 4 is used as a heat source in a boiler 8, and then released into the atmosphere.

The steam generated in each boiler 8 is collected in one steam header 11, drives a steam turbine 14 to generate electricity, and then enters a condenser 15, becomes condensed water, and is circulated to each boiler 8 again. be done. In such a combined cycle plant, an equal amount of power is applied to each gas turbine so that the plant load request signal determined by the load state of the power system matches the plant total output, which is the sum of the output of each gas turbine and the output of the steam turbine. A plant master (not shown) is provided to issue a gas turbine load command signal.

That is, the fuel flow rate of each gas turbine is controlled based on this gas turbine load command signal. Therefore, in an ideal case where the control system (gas turbine fuel control device, fuel supply system) and gas turbine characteristics of each gas turbine unit are completely the same, that is, there is no imbalance at all, the exhaust gas temperature of each gas turbine pin would be the same. Become.

However, each gas star pin is rarely exactly the same, and there are differences due to the accumulation of manufacturing tolerances, and the differences become even larger due to aging.

Therefore, even though the same load command is issued to each gas turbine, an imbalance occurs in the output of each gas turbine, and an imbalance also occurs in the exhaust gas temperature. An imbalance in the exhaust gas temperature of each gas star pin appears as an imbalance in the steam temperature generated by each boiler.

By the way, since the steam generated from a large number of boilers 8 is collected in one steam header 11, if a large imbalance occurs in the temperature of these steams, it becomes difficult to simply collect them in the steam header. Conventionally, a desuperheater or the like was installed on the steam outlet side of each boiler to reduce the temperature of the steam to the lowest temperature before supplying it to the steam header. However, considering the efficiency of the steam turbine, it is preferable that the steam temperature is as high as possible, and it is necessary to suppress the difference in the generated steam temperature between the boilers to a predetermined allowable value or less without using a desuperheater.
On the other hand, the temperature of the steam generated in the boiler depends on the temperature of the exhaust gas from the gas turbine sent to the boiler, and the exhaust gas temperature depends on the negative value of the gas turbine, that is, the flow rate of fuel supplied to the combustor.

Therefore, by detecting the exhaust gas temperature of each gas turbine and correcting the flow rate of the gas turbine pin fuel supplied to the combustor, it becomes possible to suppress the unbalance value of the generated steam temperature between the boilers to within a predetermined allowable value. [Object of the Invention] An object of the present invention is to provide a fuel control method and apparatus for correcting the imbalance in exhaust gas temperature of each gas turbine without changing the output of the gas turbine plant as a whole.

[Summary of the invention]

The present invention detects the exhaust gas temperature of each gas turbine, corrects the gas star pin causing the imbalance, and corrects the load command signal given to the identified gas star pin so as to eliminate the imbalance. , the amount of fuel supplied to the gas turbine is controlled based on the modified load command signal.

The output of the unbalanced gas turbine changes due to the modified load signal, but the plant master feeds back the load command signal so that the total actual output of the plant always matches the plant load request signal. Since it is controlled, even if the fuel flow rate of a particular gas turbine changes, the load signal from the plant master changes accordingly, and the total output as a whole matches the plant load request. In other words, as a total negative lateral control system, without changing the actual output of the plant, the load sharing of the gas turbine is changed from equal sharing to changing the load sharing according to the degree of imbalance in the exhaust gas temperature. This eliminates temperature imbalance. [Embodiment of the Invention] An embodiment of the present invention shown in the drawings will be described below.

In FIG. 2, gas turbine power generation plants 20, 30
, 40 are installed in parallel, each plant 20, 30
, each of the four rivers is connected to boiler 8 that utilizes scarlet heat. The steam from each boiler 8 is sent to one steam boiler 11, and a steam turbine 13 is connected to the header 11 via a control valve 12. steam turbine 1
3 drives the generator 14. Exhaust steam from the steam turbine 13 is guided to a condenser 15 and becomes condensed water. These configurations are the same as the previous model. In the present invention, temperature detectors 23, 33, 43 are provided in the exhaust passages from each gas turbine 4, and the temperature signals 24, 34, 44 are sent to the temperature difference correction device 1.
6 is entered.

The temperature difference correction device 16 detects the one causing an imbalance among the temperature signals 24, 34, and 44, and outputs a correction signal 17 for the detected temperature signal. This correction signal 17 is sent to a signal converter 54, where it is equivalently converted into a load command correction signal 19, which is selected by a correction signal switching device 18, and is sent to a gas turbine load command correction device for each power generation plant 20, 30, 40. 22, 32, or 42. Cutting at the correction signal switching blind pupil 18 is performed using a relay switching signal 50 from the temperature difference correction device 16. In addition, each gas turbine temperature command correction control device 22, 3
Gas turbine control devices 21, 31, 41 are connected to 2, 42, and gas turbine control devices 25, 35, 45 are connected to gas turbine control devices 25, 35, 42.
You can also enter The gas turbine control devices 21, 31, and 41 are given load commands from a plant master (not shown) such that the total actual output of the plant always matches the required plant load, and the control devices 21.3
1 and 41 output load command signals 25, 35, and 45 that equalize the load sharing among the respective gas turbines.

The gas turbine load command modification control devices 22, 32, 42 control the fuel control valve 3 based on the signals 25, 35, 45 and the load command modification signal 19.

The principles of these control systems will be explained with reference to FIG.

Now assume that the temperature signal levels corresponding to the temperature signals 24, 34, and 44 in FIG. 2 are @, ■, and @ as shown in FIG. 3, respectively. In this case, the combination of three signals is case 1
Case 3 is represented by three cases. Therefore, the difference between the three signals is taken and it is determined whether the absolute value is within the tolerance range A. If there is any signal that is not within the tolerance range A, a corrected signal is calculated as shown in the figure. For example, case 1
Since all of the values are within the allowable range, there is no need to modify the case.
In case 2, since ■ is the cause of the temperature difference imbalance, the deviation between the average value of the other two signals (@ and ■) and ■ is used as a correction signal. In case 3, ■ or @ causes an imbalance, so a correction signal for correcting ■ or @ is calculated. These correction signals are transmitted to the gas turbine load command control devices 22, 32, 42 in FIG.
and controls the fuel control valve 3. Based on the above principle, the temperature difference correction device 16, correction signal switching device 18, gas turbine load command correction control device 22, 32, 42, etc. that control the fuel control valve 3 will be explained in more detail using FIG. This will be explained in more detail.

The temperature difference correction device 16 has a temperature difference determination circuit 51 that receives the temperature signals 24, 34, and 44 as input, an unbalanced temperature determination circuit 52, and an average temperature calculation circuit 53. The temperature lid determination circuit 51 calculates the difference between each temperature signal, determines whether the absolute value of each difference is within the permissible range, and if any is not within the permissible range, an unbalanced temperature determination circuit is used. 52, it is determined which gas turbine is causing the imbalance, and which gas turbine fuel is to be corrected. According to this determination, a relay switching signal 50 is output from the temperature discrimination circuit 52. In addition, the other two temperature signals 56, which do not cause imbalance from the temperature difference determination circuit 51,
57 is sent to the average temperature calculation circuit 63, its average value is calculated, and a calculation device 61 calculates a deviation signal between the output 59 of the average value and the temperature signal 58 causing the imbalance, and calculates this signal. is output as the temperature correction signal 17. Temperature correction signal 17 is converted into temperature correction signal 1 by signal converter 54.
The load command correction signal is converted into a load command correction signal according to the magnitude of 7 and sent to the correction shoulder number switching device 18. The modified signal switching device 18 has a relay 55 corresponding to each gas turbine power plant, and the relay 55 is selected and activated by the relay switching signal 50. Therefore, the correction signal 17 is sent as the load command correction signal 19 by the correction strata switching system 18 only to the Gasterpin power plant to which the signal is to be sent. The load command modification signal 19 is sent to the gas turbine load command modification control devices 22, 32, 42 and added to the gas turbine load command signals 25, 35, 45 from the gas turbine control devices 21, 31, 41. The fuel control valve 3 is controlled by this added signal. In case 2, if the exhaust gas temperature levels of power plants 20, 30, and 40 correspond to ■, ■, and ■ in Figure 3, respectively, the gas turbine temperature command of power plant 40 corresponding to ■ is corrected. A load command correction signal 19 is given to the control device 42 . The load command correction signal 19 is sent to the gas turbine control device 41.
Since this is added to the load command signal 45 from the gas turbine power generation plant 40, the load sharing of the gas turbine power generation plant 40 increases, the exhaust gas temperature rises, and the deviation from the exhaust gas temperatures of the other plants 20 and 30 becomes smaller. On the other hand, the load sharing of the output of the gas turbine power plant 40 increases due to the load command correction signal 19, and the output increases accordingly.

Then, since the total output of the power generation plant exceeds the plant load request, the plant master issues a load command signal to the gas turbine controllers 21, 31, and 41 to reduce the output, and the plant load request and the plant total output are feedback control so that they match. Therefore, the total output of the plant is held constant,
The imbalance in exhaust gas temperature will be corrected.

In addition, the steam temperature generated in each boiler varies depending on the exhaust gas flow rate as well as the exhaust gas temperature, but in gas turbines for stimulating plants, the turbine rotation speed is constant regardless of the load. The flow rate of the compressor is constant, the exhaust gas flow rate is also constant, and if the deviation of the exhaust gas temperature is reduced by 4.0, the deviation of the generated steam temperature will also be reduced. Although the above embodiment has been described with respect to a case where there are three gas turbines, the present invention is also applicable to other cases where there are a plurality of gas turbines.

[Effects of the Invention] As described above, in the present invention, each gas turbine exhaust gas temperature is detected and the load sharing of each gas turbine is corrected and controlled so as to suppress the variation within an allowable range. As a result, the temperature imbalance of the steam generated from the poller, which uses exhaust gas as a heat source, is maintained within the permissible range, and the steam is merged directly into the steam turbine at the steam header. can be supplied.

Furthermore, it becomes possible to compensate for variations in exhaust gas temperature without changing the total output of the gas turbine power generation plant.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a steam-gas combined cycle plant to which the present invention is applied, Fig. 2 is a system diagram of a steam-gas combined cycle plant for carrying out the method of the present invention, and Fig. 3 is a system diagram illustrating the principle of the present invention. The explanatory diagram, FIG. 4, is a detailed explanatory diagram of the main part of FIG. 2. 2... Combustor, 3... Fuel control valve, 4... Gas turbine,
8... Boiler, 1 1... Steam header, 13... Steam turbine, 16... Temperature difference correction device, 18... Correction signal switching device, 20, 30, 40... Gas turbine power generation plant, 21, 31, 41... Gas turbine control device, 22, 32, 42... Gas turbine load command correction control device, 23, 33, 43... Temperature detector, 54...
・Signal converter. Younger brother's figure*2 figures, 4 figures, inferior 3 figures

Claims (1)

[Claims] 1. During operation under the same load, a plurality of gas turbines whose exhaust gas temperatures are set in advance to be equal, a plurality of boilers whose heat source is the exhaust gas of the gas turbines, and steam generated by each boiler. A multiple cycle plant having a common steam header that collects steam and a steam turbine communicating with the header, the load demand on the combined cycle plant being
In a plant equipped with a plant master that issues a load command to each gas turbine so that the actual output of the entire plant matches the load request while maintaining equal load sharing among each gas turbine, the exhaust gas temperature of each gas turbine is detected, These detected values are compared to determine which gas turbine's exhaust gas temperature has exceeded the allowable range and caused imbalance, and the average value of the detected exhaust gas temperature values that have not caused imbalance is compared. The deviation between the detected value of the exhaust temperature that is causing the imbalance is calculated, and the command load to the gas turbine that is causing the imbalance is corrected according to the deviation in a direction that eliminates the deviation. A gas turbine fuel control method for a combined cycle plant, characterized by controlling fuel supplied to a gas turbine based on a command load. 2. During operation under the same load, multiple gas turbines whose exhaust gas temperatures are set in advance to be the same, multiple boilers that use the exhaust gas of the gas turbines as a heat source, and a common steam generator that collects the steam generated by each boiler. A combined cycle plant having a header and a steam turbine in communication with the header, wherein the actual output of the entire plant matches the load demand placed on the plant, while maintaining an equal load share of each gas turbine. In a plant equipped with a plant master that issues a load command to each gas turbine, a temperature detector that detects the exhaust gas temperature of each gas turbine and each detected value of the temperature detector are compared with each other, and the difference between each detected value is determined. a temperature difference determination device that determines whether the temperature is within or outside the allowable range;
an unbalance temperature determination device that identifies a gas turbine in which the exhaust gas temperature is unbalanced based on the determination result of the temperature difference determination device; and an average that calculates the average value of the exhaust gas temperatures of the gas turbines that are not unbalanced. a temperature calculation device; a calculation device that calculates a load command correction signal from the deviation between the average temperature and the unbalanced exhaust gas temperature;
a correction signal switching device for applying the load command correction signal to a load command correction control device of a gas turbine causing an imbalance based on the signal of the unbalance temperature discriminating device; A gas turbine fuel control device for a combined cycle plant, characterized in that it controls a fuel flow signal of a gas turbine that is unbalanced due to.