Gas turbine control device, gas turbine control method, and gas turbine control program

Abstract

A gas turbine control device is a control device for controlling a gas turbine provided with a combustor capable of co-burning a first fuel and a second fuel. When a request for reducing the load of the gas turbine is acquired, the device controls the flow rate of the first fuel so that the flow rate reaches a flow rate target value. The flow rate target value at the time of acquiring the load reduction request is set by correcting the basic flow rate target value of the first fuel in accordance with the co-combustion rate, the basic flow rate target value being used for achieving the load corresponding to the load reduction request by the special combustion of the first fuel.

Description

Technical Field

[0001] The present invention relates to a gas turbine control device, a gas turbine control method and a gas turbine control program.

[0002] This application claims priority based on Japanese Patent Application No. 2023-043761 filed with the Japan Patent Office on March 20, 2023, and uses the contents thereof herein. Background Art

[0003] Gas turbines are known that can be driven by combustion gases generated by burning fuel. Gas turbines are used, for example, in gas turbine power plants, which generate electricity by coupling a generator to their output shaft. In recent years, due to growing awareness of environmental issues, these gas turbines are sometimes fueled by natural gas, a clean energy source. Natural gas, as a raw material, is extracted from gas fields and liquefied and purified to produce liquefied natural gas (LNG).

[0004] For example, when power demand for power generation equipment decreases or an abnormality in the power system is detected, a load reduction request may be issued to the gas turbine. In this case, to prevent a sudden increase in the gas turbine's rotational speed as the load is reduced, the fuel flow rate supplied to the combustor is controlled and reduced. Patent Documents 1 and 2, for example, describe gas turbine control during such load reduction. Patent Document 1 discloses limiting the fuel flow rate supplied to the combustor to a minimum fuel flow rate when the gas turbine's load is cut. Patent Document 2 discloses variably setting the minimum fuel flow rate based on the concentration of the fuel supplied to the combustor.

[0005] Previous technical literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-113487

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2-130226 Summary of the Invention

[0009] Technical issues to be solved by the invention

[0010] In recent years, the development of gas turbines capable of co-firing fuels such as LNG (the first fuel) with hydrogen (a second fuel) that has a relatively low calorific value per unit volume has been advancing. During such co-firing operation of gas turbines, the flow rates of the respective fuels are sometimes controlled to maintain a predetermined co-firing ratio.

[0011] In Patent Documents 1 and 2, when a load reduction request is issued, the fuel flow rate supplied to the combustor is instantaneously limited to the minimum fuel flow rate to prevent a sudden increase in the rotational speed. However, when a load reduction request is issued for a gas turbine operating in a co-firing mode, if the fuel flow rate supplied to the combustor is reduced regardless of the co-firing state, the operating state of the gas turbine may become unstable. Specifically, the calorific value per unit volume of a second fuel, such as hydrogen, is lower than that of a first fuel, such as LNG. Therefore, when a load reduction request is issued, if the fuel flow rate supplied to the combustor is transitioned to the same minimum fuel flow rate as when exclusively burning the first fuel, the possibility of a gas turbine misfire increases.

[0012] At least one embodiment of the present invention has been made in view of the above circumstances, and an object thereof is to provide a gas turbine control device, a gas turbine control method, and a gas turbine control program capable of stably maintaining an operating state when the load of the gas turbine decreases.

[0013] Means for solving technical problems

[0014] To solve the above-mentioned problems, a gas turbine control device according to at least one embodiment of the present invention is a gas turbine control device for controlling a gas turbine including a combustor capable of co-firing a first fuel and a second fuel having a lower calorific value per unit volume than the first fuel, the gas turbine control device comprising:

[0015] a load reduction request acquiring unit configured to acquire a load reduction request for the gas turbine;

[0016] a mixed-firing ratio acquiring unit configured to acquire the mixed-firing ratio of the burner when the load reduction request is obtained;

[0017] a flow rate target value setting unit for setting a flow rate target value of the first fuel when the load reduction request is received; and

[0018] a fuel flow rate control unit configured to control the flow rate of the first fuel to the target flow rate value when the load reduction request is received,

[0019] The target flow rate setting unit sets a basic target flow rate of the first fuel by correcting it according to the mixed combustion ratio, the basic target flow rate of the first fuel being used to achieve a load corresponding to the load reduction request by exclusively burning the first fuel.

[0020] To solve the above-mentioned problems, a gas turbine control method according to at least one embodiment of the present invention is a method for controlling a gas turbine including a combustor capable of co-firing a first fuel and a second fuel having a lower calorific value per unit volume than the first fuel, the method comprising the following steps:

[0021] obtaining a load reduction request for the gas turbine;

[0022] obtaining a mixed firing rate of the burner when the load reduction request is obtained;

[0023] setting a target flow rate value of the first fuel when the load reduction request is received; and

[0024] When the load reduction request is received, the flow rate of the first fuel is controlled so as to reach the flow rate target value;

[0025] In the step of setting the target flow rate value, the target flow rate value of the first fuel is set by correcting the target flow rate value of the first fuel according to the mixed combustion ratio. The target flow rate value of the first fuel is used to achieve the load corresponding to the load reduction request by exclusively burning the first fuel.

[0026] To solve the above-mentioned problems, a gas turbine control program according to at least one embodiment of the present invention is for controlling a gas turbine including a combustor capable of co-firing a first fuel and a second fuel having a lower calorific value per unit volume than the first fuel, wherein the program is capable of executing the following steps using a computer device:

[0027] obtaining a load reduction request for the gas turbine;

[0028] obtaining a mixed firing rate of the burner when the load reduction request is obtained;

[0029] setting a target flow rate value of the first fuel when the load reduction request is received; and

[0030] When the load reduction request is received, the flow rate of the first fuel is controlled so as to reach the flow rate target value;

[0031] In the step of setting the target flow rate value, the target flow rate value of the first fuel is set by correcting the target flow rate value of the first fuel according to the mixed combustion ratio. The target flow rate value of the first fuel is used to achieve the load corresponding to the load reduction request by exclusively burning the first fuel.

[0032] Effects of the Invention

[0033] According to at least one embodiment of the present invention, it is possible to provide a gas turbine control device, a gas turbine control method, and a gas turbine control program capable of stably maintaining an operating state when the load of the gas turbine decreases. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram showing a schematic configuration of a gas turbine according to an embodiment.

[0035] Figure 2 yes Figure 1 Example of a cross-sectional structure of a burner.

[0036] Figure 3 This is a block diagram showing the functional configuration of a gas turbine control device according to one embodiment.

[0037] Figure 4 Yes Figure 3 A block diagram of the structure of the flow target value setting unit.

[0038] Figure 5 1 is a time chart showing temporal changes in the opening degree of the shutoff valve, the target flow rate value of the fuel supplied to the burner, and the mixed combustion ratio when a load reduction request is obtained at time point t1.

[0039] Figure 6 Yes Figure 3 A block diagram of a structural example of a fuel ratio setting unit.

[0040] Figure 7 This is a time chart showing temporal changes in the opening degree of the shutoff valve, the target flow rate value of the fuel supplied to the burner, the mixed combustion ratio, and the pilot fuel ratio when a load reduction request is received at time point t1. DETAILED DESCRIPTION

[0041] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the configurations described or illustrated as the embodiments are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.

[0042] First, refer to Figure 1 Next, a description will be given of the gas turbine 1 that is a control target of a gas turbine control device 100 according to at least one embodiment of the present invention. Figure 1 This is a diagram showing a schematic configuration of a gas turbine 1 according to one embodiment.

[0043] The gas turbine 1 includes a compressor 3 that generates compressed air, a combustor 2 that generates combustion gas by mixing the compressed air generated by the compressor 3 with fuel, a fuel supply system 4 that supplies fuel to the combustor 2, and a turbine 6 driven by the combustion gas. The compressor 3 and the turbine 6 are connected to each other via a single shaft. In the gas turbine 1 having this structure, the compressed air compressed by the compressor 3 and the fuel supplied from the fuel supply system 4 are supplied to the combustor 2, where they mix and combust to generate combustion gas. This combustion gas flows into the turbine 6 and acts as power to drive the turbine 6.

[0044] The fuel supply system 4 uses a mixed fuel composed of a first fuel F1 and a second fuel F2 as the fuel supplied to the burner 2. The second fuel F2 has a lower calorific value per unit volume than the first fuel F1. In this embodiment, the first fuel F1 is liquefied natural gas (LNG) and the second fuel F2 is hydrogen.

[0045] The first fuel F1 is supplied via a first fuel supply line 8 connected to a first fuel supply source 7. The first fuel supply line 8 is provided with a flow meter 10 for detecting the flow rate of the first fuel F1.

[0046] The second fuel F2 is supplied via a second fuel supply line 16 connected to a second fuel supply source 14. The second fuel supply line 16 is provided with a first flow rate regulating valve 18 for regulating the flow rate of the second fuel F2 and a shutoff valve 13 for shutting off the second fuel F2.

[0047] The first fuel supply line 8 and the second fuel supply line 16 merge with each other on the downstream side and are connected to the main fuel supply line 22. The first fuel F1 and the second fuel F2 are mixed by merging at the merging portion 25 of the first fuel supply line 8 and the second fuel supply line 16, and the mixed fuel (hereinafter referred to as "mixed fuel Fm" as appropriate) is delivered through the main fuel supply line 22.

[0048] Furthermore, the main fuel supply line 22 is provided with a shutoff valve 24 for shutting off the mixed fuel Fm and a second flow rate regulating valve 26 for adjusting the flow rate of the mixed fuel Fm.

[0049] The downstream side of the main fuel supply line 22 branches into multiple fuel branch supply lines 28a, 28b, ..., corresponding to the multiple fuel injectors provided in the burner 2. In this embodiment, as described later, the multiple fuel injectors include the main fuel injector 52 and the pilot fuel injector 56, but may also include top hat fuel injectors. In this case, at least some of the main fuel injectors 52 may be grouped. Third flow control valves 30a, 30b, ..., are provided on each of the multiple fuel branch supply lines 28a, 28b, ..., for adjusting the flow rate of the mixed fuel flowing through each line. Of the multiple fuel branch supply lines 28a, 28b, ..., fuel branch supply lines 28a, 28b, 28c are connected to the main fuel injector 52, while fuel branch supply line 28d is connected to the pilot fuel injector 56.

[0050] Figure 2 yes Figure 1The combustor 2 is provided with an outer tube 32, a liner 34, a tail tube (not shown) and a burner 36. The outer tube 32 is a cylindrical component provided on the outer periphery of the turbine casing (not shown). Figure 2 The end (head) of the turbine 6 (left side) is closed by the end cover 38. The liner 34 is a cylindrical combustor inner tube that forms a combustion chamber 40 inside. It is arranged on the inner side of the outer tube 32 and forms an annular air flow path between it and the outer tube 32. A plurality of air holes are bored in the liner 34. The combustion chamber 40 is a space formed between the burner 36 and the tail cylinder by the liner 34, and the fuel ejected from the burner 36 is burned together with the air 42 here. The tail cylinder is a component that smoothly connects the inlet of the gas path of the turbine 6 (the primary stator blade inlet) and the liner 34. In addition, a fuel distributor 44 that distributes fuel to the burner 36 is provided on the end cover 38. In addition, although not specifically shown in the figure, the combustor 2 is also equipped with an ignition device that ignites the mixed gas of fuel and air in the combustion chamber 40.

[0051] The burner 36 is provided on the end cover 38 so as to be located between the burner 36 and the combustion chamber 40. The burner 36 includes a plurality of element burners, a pilot burner 46 is arranged in the center of the combustor 2, and a plurality of main burners 48 are arranged radially outward of the pilot burner 46 so as to surround the pilot burner 46.

[0052] Each main burner 48 includes an air hole plate 50 and a plurality of main fuel injection nozzles 52 serving as fuel injection nozzles. However, the air hole plate 50 connects the plurality of main burners 48 to one another. The air hole plate 50 is arranged so that its main surface (the surface with the largest area) faces the combustion chamber 40 and includes a plurality of air holes 54 extending from the end cover 38 toward the combustion chamber 40. Air 42 is ejected from these air holes 54 into the combustion chamber 40. The plurality of fuel injection nozzles 52 each include a pair of air holes 54, and each fuel injection nozzle 52 extends from the fuel distributor 44 coaxially with the corresponding air hole 54. Furthermore, the tip of each fuel injection nozzle 52 may be inserted into the air hole 54 (located within the air hole 54), but in this embodiment, the tip is arranged so that it faces the inlet of the air hole 54 (located closer to the end cover 38 than the air hole plate 50). The gaseous fuel injected from the fuel injection nozzle 52 is ejected into the combustion chamber 40 through the corresponding air holes 54 together with the air 42 passing through the air holes 54 .

[0053] The pilot burner 46 has a structure similar to that of the aforementioned main burner 48, and is located at the center of the plurality of main burners 48. The pilot burner 46 includes a pilot fuel injection nozzle 56 as a fuel injection nozzle.

[0054] Next, the gas turbine control device 100 for controlling the gas turbine 1 having the above-described structure will be described. The gas turbine control device 100 is a control unit for controlling the gas turbine 1 and is comprised of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. For example, a series of processes for implementing various functions is stored in the form of a program on a storage medium. The CPU reads this program into the RAM, executes information processing and calculations, and thus implements various functions. Alternatively, the program may be pre-installed in a ROM or other storage medium, provided as stored on a computer-readable storage medium, or transmitted via wired or wireless communication means. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like.

[0055] Figure 3 This is a block diagram showing the functional configuration of a gas turbine control device 100 according to one embodiment. The gas turbine control device 100 includes a load reduction request acquisition unit 102, an abnormality detection unit 103, a combustion ratio acquisition unit 104, a flow rate target value setting unit 106, a fuel ratio setting unit 107, and a fuel flow rate control unit 108.

[0056] The load reduction request acquisition unit 102 is configured to acquire a load reduction request for the gas turbine 1. A load reduction request is a command requesting that the load on the gas turbine 1 be reduced from its current value. For example, it may be a command requesting that the load on the gas turbine 1 be reduced to below a predetermined value. In this embodiment, as an example of a load reduction request, a command requesting that the load (output) of the gas turbine 1 be reduced to zero is acquired when the abnormality detection unit 103 detects that the gas turbine has been disconnected from the power transmission system and a load shedding operation has occurred on the gas turbine power generation facility.

[0057] The load reduction request is not limited to an instruction to set the load to zero, and can broadly include an instruction to operate the gas turbine 1 at a load lower than the current load. Furthermore, the load reduction request may be generated by the gas turbine control device through its own internal processing, in addition to receiving the load reduction request from another device.

[0058] The combustion ratio acquisition unit 104 is a structure for acquiring the combustion ratio when a load reduction request is received. The combustion ratio can be acquired, for example, as a result of calculation based on the flow rate of the first fuel F1 obtained by the flowmeter 10 disposed in the first fuel supply line 8 and the flow rate of the second fuel F2 obtained by the flowmeter 15 disposed in the second fuel supply line 16. Furthermore, the combustion ratio acquisition unit 104 can acquire parameters related to the combustion ratio instead of the combustion ratio itself, and calculate the combustion ratio based on these parameters.

[0059] The target flow rate setting unit 106 is configured to set the target flow rate CSO for the fuel supplied to the burner 2 when a load reduction request is received. The fuel supplied to the burner 2 is the fuel flow rate of the mixed fuel Fm of the first fuel F1 and the second fuel F2 when in a mixed combustion state, and the fuel flow rate of the first fuel F1 when burning exclusively the first fuel. The fuel flow rate supplied to the burner 2 can be adjusted by the second flow control valve 26. Although described in detail later, the target flow rate CSO is set by correcting the basic target flow rate CSOf1, which is the fuel flow rate required to achieve the load corresponding to the load reduction request through the exclusive combustion of the first fuel F1, based on the mixed combustion ratio when the load reduction request is received.

[0060] The fuel ratio setting unit 107 is a structure for setting the fuel ratio for a specific fuel injector among the multiple fuel injectors provided in the combustor 2. In the present embodiment, as an example of such a fuel ratio, the ratio of the fuel supply amount to the pilot fuel injector 56 by the fuel supply system 4 relative to the total fuel supply flow rate (so-called pilot fuel ratio Dpl) is used.

[0061] The fuel flow rate control unit 108 is configured to control the fuel flow rate of the fuel supply system 4. Upon receiving a load reduction request, the fuel flow rate control unit 108 controls the flow rates and fuel ratio of the first fuel F1 and the second fuel F2 based on the target flow rate set by the target flow rate setting unit 106 and the fuel ratio set by the fuel ratio setting unit 107.

[0062] Here, reference Figure 4 and Figure 5 , the detailed structure of the flow target value setting unit 106 is described. Figure 4 Yes Figure 3 A block diagram of the structure of the flow target value setting unit 106 is shown in FIG. Figure 5 This is a time chart showing temporal changes in the opening degree of the shutoff valve 13 , the target flow rate CSO of the fuel supplied to the burner 2 , and the co-firing ratio when a load reduction request is received at time point t1 .

[0063] like Figure 4As shown, the target flow rate setting unit 106 includes a basic target flow rate setting unit 110. The basic target flow rate CSOf1 set by the basic target flow rate setting unit 110 is determined to correspond to the load reduction request value when the first fuel F1 is burned exclusively. In the present embodiment, the load reduction request is a request to reduce the load of the gas turbine to zero. Therefore, the basic target flow rate CSOf1 is set to the minimum flow rate value at which the gas turbine 1 can operate when burning exclusively the first fuel F1.

[0064] The flow rate target value setting unit 106 sets the flow rate target value CSO by correcting the basic flow rate target value CSOf1 based on the co-firing ratio as needed. This correction is enabled or disabled by switching control of the switch T1 based on the load reduction request received by the load reduction request acquisition unit 102 .

[0065] A load reduction request is input from the load reduction request acquisition unit 102 to the timer 112. The timer 112 is configured to output an ON command to the switch T1 after a predetermined period Tr1 has elapsed since the time t1 at which the load reduction request was input. On the other hand, if no load reduction request has been received, or even if a load reduction request has been received, the switch T1 is turned OFF after the predetermined period Tr1 has elapsed since the time t1 at which the load reduction request was received.

[0066] Furthermore, in the target flow rate setting unit 106, the co-firing ratio acquired by the co-firing ratio acquisition unit 104 is input into a function FX1, thereby calculating a first correction value A1. Function FX1 is prepared in advance as a function that defines the correlation between the co-firing ratio and the first correction value A1. During a predetermined period Tr1 from time t1 when the load reduction request acquisition unit 102 acquires the load reduction request, i.e., the period during which switch T1 is turned on, the first correction value A1 output from function FX1 is multiplied by the basic target flow rate CSOf1. This corrects the basic target flow rate CSOf1 based on the first correction value A1, thereby determining the target flow rate CSO.

[0067] exist Figure 5In the example, a load reduction request is obtained at time t1. Subsequently, in the flow target value setting unit 106, the basic flow target value CSOf1 is corrected according to the first correction value A1 due to the switch T1 being switched ON, thereby setting a flow target value CSOfm that is larger than the basic flow target value CSOf1. In this way, the flow target value CSO of the fuel flow rate when the load reduction request is obtained is set according to the combustion ratio. The basic flow target value CSOf1 is corrected according to the combustion ratio so as to become a load value corresponding to the load reduction request (in this embodiment, zero load corresponding to the load cut-off), thereby obtaining the flow target value CSO. As a result, even when the fuel supplied to the combustor 2 is restricted in such a manner as to reduce the load of the gas turbine 1 in accordance with the load reduction request, the operating state of the gas turbine 1 can be stably maintained.

[0068] Specifically, when a load reduction request is received at time t1, the target flow rate CSO is temporarily set to be greater than the basic target flow rate CSOf1. This prevents the operating state of the gas turbine 1 from becoming unstable when the fuel flow rate is reduced to reduce the load of the gas turbine 1 in response to the load reduction request.

[0069] exist Figure 5 In the example shown in FIG. 1 , when a load reduction request is received, the shutoff valve 13 provided in the second fuel supply line 16 is fully closed to cut off the supply of the second fuel F2. This is because, when limiting the fuel flow rate to a minimum, it is easier to control the valve by controlling only the flow rate of the first fuel F1, which has a higher calorific value per unit volume, than by controlling the flow rates of both the first fuel F1 and the second fuel F2. A predetermined time Tr after the shutoff valve 13 provided in the second fuel supply line 16 is fully closed, the mixed fuel remaining in the fuel piping from the junction 25 to the burner 2 flows to the burner 2. After the predetermined time Tr has elapsed, only the first fuel F1 flows to the burner 2. Therefore, the target flow rate setting unit 106 sets the basic target flow rate CSOf1 as the target flow rate CSO at time t2, which is a predetermined period Tr1 after time t1 when the load reduction request is received. Specifically, the target flow rate CSO is changed to the basic target flow rate CSOf1 upon the elapse of a predetermined period Tr1 from the time point t1 at which the load reduction request is received. Thus, by setting a target flow rate greater than the basic target flow rate CSOf1 during the predetermined period Tr1 from the time point t1 at which the load reduction request is received, it is possible to suppress destabilization of the operating state of the gas turbine 1 due to load fluctuations. Furthermore, by setting the target flow rate CSO to the basic target flow rate CSOf1 after the predetermined period Tr1 has elapsed, a stable transition to a low-load operating state of the gas turbine 1 based on exclusive combustion of the first fuel F1 is achieved.

[0070] The predetermined period Tr1 is set based on the time required for the mixed fuel of the first fuel F1 and the second fuel F2 to reach the combustor 2 from the confluence 25 between the first fuel supply line 8 for supplying the first fuel F1 and the second fuel supply line 16 for supplying the second fuel F2. Thus, when the second fuel F2 is shut off, the target flow rate CSO of the fuel supplied to the combustor 2 is set to be greater than the basic flow rate target value CSOf1 until the mixed fuel remaining between the confluence 25 and the combustor 2 reaches the combustor 2. This can suppress destabilization of the operating state of the gas turbine 1 caused by limiting the fuel flow rate.

[0071] In addition, Figure 5 In the example shown in FIG. 1 , when a load reduction request is received, the shutoff valve 13 provided in the second fuel supply line 16 is fully closed. However, this does not necessarily cut off the supply of the second fuel F2. In this case, the switch T1 does not need to be turned OFF by the timer 112 after the predetermined period Tr1 has elapsed. Control is sufficient to maintain the target flow rate CSOfm, which is corrected based on the co-firing ratio, even after the predetermined period Tr1 has elapsed.

[0072] Next, refer to Figure 6 and Figure 7 , another embodiment is described. Figure 6 Yes Figure 3 A block diagram of a configuration example of the fuel ratio setting unit 107 is shown. Figure 7 It is a time chart showing temporal changes in the opening degree of the shutoff valve 13 , the target flow rate CSO of the fuel supplied to the combustor 2 , the combustion ratio, and the pilot fuel ratio Dpl when a load reduction request is received at time point t1 .

[0073] like Figure 6 As shown, the fuel ratio setting unit 107 includes a basic fuel ratio setting unit 114. The basic fuel ratio setting unit 114 is a structure for setting the basic fuel ratio. In the present embodiment, in particular, the basic fuel ratio setting unit 114 sets the basic fuel ratio in a manner that temporarily increases when a load reduction request is received. Specifically, the basic fuel ratio basically has a first value Dpl1, but if a load reduction request is received at time point t1, it increases to a second value Dpl2 (> first value Dpl1) within a predetermined period Tr2. Then, after the predetermined period Tr2 has passed, it returns to the first value Dpl1 again. In this way, when there is a load reduction request, the basic fuel ratio is set in a manner that temporarily increases the fuel ratio, thereby effectively preventing abnormal combustion or misfire of the gas turbine 1 associated with load changes.

[0074] In addition, the predetermined period Tr2 is set to be shorter than the aforementioned predetermined period Tr1, but the magnitude relationship between the two is not limited, and the two may be the same.

[0075] The fuel ratio setting unit 107 sets the fuel ratio by correcting the increase rate of the basic fuel ratio when the load reduction request is obtained according to the mixed combustion ratio. Figure 6 In the embodiment, the fuel ratio setting unit 107 corrects the basic fuel ratio by using the second correction value A2 calculated based on the combustion ratio, thereby setting the fuel ratio.

[0076] Correction using the second correction value A2 is enabled or disabled by switching control of switch T2 based on the load reduction request received by the load reduction request acquisition unit 102. The load reduction request received by the load reduction request acquisition unit 102 is input to the timer 116. Timer 116 is configured to output an ON command to switch T2 after a predetermined period Tr2 has elapsed from time t1 when the load reduction request was received. On the other hand, if a load reduction request has not been received, or even if a load reduction request has been received, switch T2 is switched OFF after a predetermined period Tr2 has elapsed from time t1 when the load reduction request was received.

[0077] Furthermore, in the fuel ratio setting unit 107, the combustion ratio acquired by the combustion ratio acquisition unit 104 is input into a function FX2, thereby calculating a second correction value A2. Function FX2 is prepared in advance as a function that specifies the correlation between the combustion ratio and the second correction value A2. During a predetermined period Tr2 from time t1 when the load reduction request acquisition unit 102 acquires the load reduction request as described above, i.e., during the period when switch T2 is turned on, the output of function FX2 is added to the base fuel ratio, which is at the second value Dpl2. Thus, the base fuel ratio Dpl2 is corrected according to the second correction value A2, and the fuel ratio is set to a third value Dpl3 during the predetermined period Tr2.

[0078] In this manner, the fuel ratio setting unit 107 sets the fuel ratio increase rate when a load reduction request is received based on the combustion ratio. Consequently, even when the second fuel F2 is shut off during load reduction of the gas turbine 1, the fuel ratio can be corrected based on changes in the combustion ratio of the gas turbine 1. This prevents abnormal combustion and misfires, and allows the gas turbine to maintain a stable operating state.

[0079] Furthermore, constituent elements in the above-described embodiments may be appropriately replaced with known constituent elements within a scope not departing from the spirit of the present invention, and the above-described embodiments may be appropriately combined.

[0080] The contents described in each of the above embodiments can be understood, for example, as follows.

[0081] (1) A gas turbine control device according to one embodiment is a gas turbine control device for controlling a gas turbine including a combustor capable of co-firing a first fuel and a second fuel having a lower calorific value per unit volume than the first fuel, the gas turbine control device comprising:

[0082] a load reduction request acquiring unit configured to acquire a load reduction request for the gas turbine;

[0083] a mixed-firing ratio acquiring unit configured to acquire the mixed-firing ratio of the burner when the load reduction request is obtained;

[0084] a flow rate target value setting unit for setting a flow rate target value of the first fuel when the load reduction request is received; and

[0085] a fuel flow rate control unit configured to control the flow rate of the first fuel to the target flow rate value when the load reduction request is received,

[0086] The target flow rate setting unit sets a basic target flow rate of the first fuel by correcting it according to the mixed combustion ratio, the basic target flow rate of the first fuel being used to achieve a load corresponding to the load reduction request by exclusively burning the first fuel.

[0087] According to the above-described embodiment (1), a target flow rate value of the fuel supplied to the combustor when a load reduction request is received is set based on the combustion ratio. This target flow rate value is obtained by correcting a basic target flow rate value of the fuel based on the combustion ratio. This basic target flow rate value of the fuel is used to control the gas turbine so that the load value corresponding to the load reduction request is achieved by exclusively burning the first fuel. Thus, even when the fuel supply is restricted so that the load of the gas turbine is reduced in response to the load reduction request, the operating state of the gas turbine can be stably maintained.

[0088] (2) In another embodiment, in the embodiment of (1),

[0089] The flow rate target value setting unit sets the flow rate target value when the load reduction request is received so as to be larger than the basic flow rate target value, using a first target value calculated based on the co-firing ratio.

[0090] According to the above-described aspect (2), the target flow rate of the fuel supplied to the combustor when a load reduction request is received is set to be greater than the basic flow rate target value corresponding to when exclusively burning the first fuel. This can prevent the operating state of the gas turbine from becoming unstable when the fuel flow rate is reduced to reduce the load of the gas turbine in response to the load reduction request.

[0091] (3) In another embodiment, in the embodiment of (2),

[0092] The fuel flow rate control unit cuts off the second fuel when the load reduction request is received.

[0093] The flow rate target value setting unit sets the basic flow rate target value as the flow rate target value when a predetermined period has elapsed from a time point when the load reduction request is acquired.

[0094] According to the above-described embodiment (3), the flow rate target value is changed to the basic flow rate target value upon the lapse of a predetermined period from the time when the load reduction request is received. Thus, by setting a flow rate target value greater than the basic flow rate target value during the predetermined period from the time when the load reduction request is received, it is possible to suppress instability in the gas turbine operating state caused by load fluctuations. Furthermore, by setting the flow rate target value to the basic flow rate target value after the predetermined period has elapsed, it is possible to stably transition to a low-load operating state of the gas turbine based on exclusive combustion of the first fuel.

[0095] (4) In another embodiment, in the embodiment of (3),

[0096] The predetermined period is set based on a time required for a mixed fuel of the first fuel and the second fuel to reach the burner from a merging portion of a first fuel supply passage for supplying the first fuel and a second fuel supply passage for supplying the second fuel.

[0097] According to the above-mentioned embodiment (4), a predetermined period is set during which the target flow rate of the first fuel is set to be greater than the basic target flow rate when the second fuel is cut off due to a request for load reduction of the gas turbine, based on the time required for the mixed fuel of the first fuel and the second fuel to reach the combustor from the confluence. Thus, when the second fuel is cut off, the target flow rate of the first fuel is set to be greater than the basic target flow rate until the mixed fuel remaining between the confluence and the combustor reaches the combustor, thereby suppressing instability in the operating state of the gas turbine caused by load fluctuations. Furthermore, after the predetermined period has elapsed, by setting the target flow rate to the basic target flow rate, a stable transition to a low-load operating state of the gas turbine based on exclusively burning the first fuel can be achieved.

[0098] (5) In another embodiment, in any one of the above embodiments (1) to (4), further comprising:

[0099] A fuel ratio setting unit for setting the fuel ratios of the plurality of different fuel injection nozzles of the burner.

[0100] The fuel ratio setting unit sets the fuel ratio so as to temporarily increase the fuel ratio when the load reduction request is acquired.

[0101] According to the above aspect (5), by setting the fuel ratio so as to temporarily increase when a load reduction request is received, abnormal combustion or misfire of the gas turbine accompanying a load change can be effectively prevented.

[0102] (6) In another embodiment, in the embodiment of (5),

[0103] The fuel ratio is a pilot fuel ratio that defines a fuel ratio for a pilot fuel injection nozzle among the plurality of different fuel injection nozzles.

[0104] According to the above aspect (6), by setting the fuel ratio to be controlled as the pilot fuel ratio, abnormal combustion or misfire of the gas turbine accompanying load changes can be effectively prevented.

[0105] (7) In another embodiment, in the embodiment of (5) or (6),

[0106] The fuel ratio setting unit sets an increase rate of the fuel ratio when the load reduction request is received, based on the co-firing ratio.

[0107] According to the above-mentioned embodiment (7), the rate of increase of the control target value of the fuel ratio when the load of the gas turbine changes due to a load reduction request is set according to the fuel ratio. Thus, when the load of the gas turbine is reduced, by correcting the fuel ratio according to the fuel ratio of the gas turbine, abnormal combustion or misfire can be prevented, and the operating state of the gas turbine can be maintained stably.

[0108] (8) In another embodiment, in any one of the above embodiments (1) to (7), further comprising:

[0109] The abnormality detection unit is configured to output the load reduction request when an abnormality of the gas turbine is detected.

[0110] According to the above-mentioned embodiment (8), when an abnormality is detected in the gas turbine, a load reduction request is output. By using the load reduction request thus output as a trigger to implement the aforementioned fuel flow rate control, it is possible to implement the load reduction control of the gas turbine while stably maintaining the operating state of the gas turbine when an abnormality is detected in the gas turbine.

[0111] (9) In another aspect, in any one of the aspects (1) to (8) above, the load reduction request is a request for setting the load of the gas turbine to zero load.

[0112] According to the aspect (9) above, when the load of the gas turbine is reduced to zero in response to a load reduction request, the operating state of the gas turbine can be stably maintained.

[0113] (10) A gas turbine control method according to one embodiment is a gas turbine control method for controlling a gas turbine having a combustor capable of co-firing a first fuel and a second fuel having a lower calorific value per unit volume than the first fuel, the method comprising the following steps:

[0114] obtaining a load reduction request for the gas turbine;

[0115] obtaining a mixed firing rate of the burner when the load reduction request is obtained;

[0116] setting a target flow rate value of the first fuel when the load reduction request is received; and

[0117] When the load reduction request is received, the flow rate of the first fuel is controlled so as to reach the flow rate target value;

[0118] In the step of setting the target flow rate value, the target flow rate value of the first fuel is set by correcting the target flow rate value of the first fuel according to the mixed combustion ratio. The target flow rate value of the first fuel is used to achieve the load corresponding to the load reduction request by exclusively burning the first fuel.

[0119] According to the above-mentioned embodiment (10), a target flow rate value of the fuel supplied to the combustor when a load reduction request is received is set based on the co-firing ratio. This target flow rate value is obtained by correcting a basic target flow rate value of the fuel based on the co-firing ratio. This basic target flow rate value of the fuel is used to control the gas turbine so that the load value corresponding to the load reduction request is achieved by exclusively burning the first fuel. Thus, even when the fuel is restricted so that the load of the gas turbine is reduced in response to the load reduction request when the gas turbine is co-firing, the operating state of the gas turbine can be stably maintained.

[0120] (11) A gas turbine control program according to one embodiment is for controlling a gas turbine having a combustor capable of co-firing a first fuel and a second fuel having a lower calorific value per unit volume than the first fuel, wherein the program is capable of executing the following steps using a computer device:

[0121] obtaining a load reduction request for the gas turbine;

[0122] obtaining a mixed firing rate of the burner when the load reduction request is obtained;

[0123] setting a target flow rate value of the first fuel when the load reduction request is received; and

[0124] When the load reduction request is received, the flow rate of the first fuel is controlled so as to reach the flow rate target value;

[0125] In the step of setting the target flow rate value, the target flow rate value of the first fuel is set by correcting the target flow rate value of the first fuel according to the mixed combustion ratio. The target flow rate value of the first fuel is used to achieve the load corresponding to the load reduction request by exclusively burning the first fuel.

[0126] According to the above-mentioned method (11), a target flow rate value of the fuel supplied to the combustor when a load reduction request is received is set according to the co-firing ratio. This target flow rate value is obtained by correcting a basic flow rate target value of the fuel according to the co-firing ratio. This basic flow rate target value of the fuel is used to control the gas turbine so that the load value corresponding to the load reduction request is achieved by exclusively burning the first fuel. Thus, even when the fuel is restricted so that the load of the gas turbine is reduced in response to the load reduction request when the gas turbine is co-firing, the operating state of the gas turbine can be stably maintained.

[0127] Explanation of symbols

[0128] 1- Gas turbine, 2- Combustor, 3- Compressor, 4- Fuel supply system, 6- Turbine, 7- First fuel supply source, 8- First fuel supply line, 10- Flowmeter, 13- Stop valve, 14- Second fuel supply source, 16- Second fuel supply line, 18- First flow control valve, 22- Main fuel supply line, 24- Stop valve, 25- Junction, 26- Second flow control valve, 28a, 28b, ... - Fuel branch supply line, 30a, 30b, ... - Third flow control valve, 32- Outer cylinder, 34- Liner, 36-burner, 38-end cover, 40-combustion chamber, 44-fuel distributor, 46-pilot burner, 48-main burner, 50-air hole plate, 52-main fuel injection nozzle, 54-air hole, 56-pilot fuel injection nozzle, 100-gas turbine control device, 102-load reduction request acquisition unit, 103-abnormality detection unit, 104-mixed combustion ratio acquisition unit, 106-flow rate target value setting unit, 107-fuel ratio setting unit, 108-fuel flow rate control unit, F1-first fuel, F2-second fuel.

Claims

1. A gas turbine control device for controlling a gas turbine including a combustor capable of co-firing a first fuel and a second fuel having a lower calorific value per unit volume than the first fuel, the gas turbine control device comprising: a load reduction request acquiring unit configured to acquire a load reduction request for the gas turbine; a mixed-firing ratio acquiring unit configured to acquire the mixed-firing ratio of the burner when the load reduction request is obtained; a flow rate target value setting unit for setting a flow rate target value of the first fuel when the load reduction request is received; and a fuel flow rate control unit configured to control the flow rate of the first fuel to the target flow rate value when the load reduction request is received, The target flow rate setting unit sets a basic target flow rate of the first fuel by correcting it according to the mixed combustion ratio, the basic target flow rate of the first fuel being used to achieve a load corresponding to the load reduction request by exclusively burning the first fuel.

2. The gas turbine control device according to claim 1, wherein: The flow rate target value setting unit sets the flow rate target value when the load reduction request is received so as to be larger than the basic flow rate target value, using a first target value calculated based on the co-firing ratio.

3. The gas turbine control device according to claim 2, wherein: The fuel flow rate control unit cuts off the second fuel when the load reduction request is received. The flow rate target value setting unit sets the basic flow rate target value as the flow rate target value when a predetermined period has elapsed from a time point when the load reduction request is acquired.

4. The gas turbine control device according to claim 3, wherein: The predetermined period is set based on a time required for a mixed fuel of the first fuel and the second fuel to reach the burner from a merging portion of a first fuel supply passage for supplying the first fuel and a second fuel supply passage for supplying the second fuel.

5. The gas turbine control device according to claim 1 or 2, further comprising: A fuel ratio setting unit for setting the fuel ratios of the plurality of different fuel injection nozzles of the burner. The fuel ratio setting unit sets the fuel ratio so as to temporarily increase the fuel ratio when the load reduction request is acquired.

6. The gas turbine control device according to claim 5, wherein: The fuel ratio is a pilot fuel ratio that defines a fuel ratio for a pilot fuel injection nozzle among the plurality of different fuel injection nozzles.

7. The gas turbine control device according to claim 5, wherein: The fuel ratio setting unit sets an increase rate of the fuel ratio when the load reduction request is received, based on the co-firing ratio.

8. The gas turbine control device according to claim 1 or 2, further comprising: The abnormality detection unit is configured to output the load reduction request when an abnormality of the gas turbine is detected.

9. The gas turbine control device according to claim 1 or 2, wherein: The load reduction request is a request for setting the load of the gas turbine to zero load.

10. A gas turbine control method for controlling a gas turbine including a combustor capable of co-firing a first fuel and a second fuel having a lower calorific value per unit volume than the first fuel, the gas turbine control method comprising the following steps: obtaining a load reduction request for the gas turbine; obtaining a mixed firing rate of the burner when the load reduction request is obtained; setting a target flow rate value of the first fuel when the load reduction request is received; and When the load reduction request is received, the flow rate of the first fuel is controlled so as to reach the flow rate target value; In the step of setting the target flow rate value, the target flow rate value of the first fuel is set by correcting the target flow rate value of the first fuel according to the mixed combustion ratio. The target flow rate value of the first fuel is used to achieve the load corresponding to the load reduction request by exclusively burning the first fuel.

11. A gas turbine control program for controlling a gas turbine including a combustor capable of co-firing a first fuel and a second fuel having a lower calorific value per unit volume than the first fuel, wherein: The following processes can be performed using a computer device: obtaining a load reduction request for the gas turbine; obtaining a mixed firing rate of the burner when the load reduction request is obtained; setting a target flow rate value of the first fuel when the load reduction request is received; and When the load reduction request is received, the flow rate of the first fuel is controlled so as to reach the flow rate target value; In the step of setting the target flow rate value, the target flow rate value of the first fuel is set by correcting the target flow rate value of the first fuel according to the mixed combustion ratio. The target flow rate value of the first fuel is used to achieve the load corresponding to the load reduction request by exclusively burning the first fuel.

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