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

Abstract

A gas turbine control device controls a gas turbine provided with a combustor capable of generating combustion gas for driving the gas turbine by co-combustion of a first fuel and a second fuel. When it is determined that the device is in a supply state in which at least a portion of the second fuel to the combustor is cut off, the device calculates a fuel flow rate at the time of cutting off which should be supplied to the combustor in accordance with a fuel co-combustion rate after the at least a portion of the second fuel is cut off. Furthermore, a fuel flow rate command value corresponding to the fuel flow rate at the time of shutoff is output before at least a part of the second fuel is shutoff and reaches the fuel co-combustion rate.

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. 2022-166116 filed with the Japan Patent Office on October 17, 2022, and incorporates its content herein. Background Art

[0003] There is known a gas turbine power generation device that generates electricity by driving a turbine connected to a generator with combustion gas generated by burning fuel. In recent years, due to increased awareness of environmental issues, sometimes clean energy, namely natural gas, is also used as fuel in such gas turbine power generation devices. Natural gas is extracted from gas fields and the like as raw natural gas, and is used as liquefied natural gas (LNG: Liquefied Natural Gas) through liquefaction / purification.

[0004] For example, Patent Document 1 discloses a technology related to a gas turbine that uses a mixture of liquefied natural gas and boil-off gas (BOG), which is a low-calorie gas generated in a liquefied natural gas storage facility or the like, as fuel for the gas turbine. The following is described in this document: When the supply of boil-off gas stops for some reason and the calorific value of the fuel supplied to the gas turbine increases, the operating state of the gas turbine is stabilized by reducing the fuel flow rate supplied to the gas turbine.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-227886 Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] In a gas turbine that co-fires fuel gases with different combustion characteristics, when the supply system of a part of the fuel gas stops due to some failure or defect, the combustion characteristics of the fuel gas change, which may pose an obstacle to the stable operation of the gas turbine. For example, in the case of burning a mixture of natural gas and hydrogen with a low calorific value per unit volume in a gas turbine, when at least a part of the hydrogen supply system stops, the proportion of natural gas with a high calorific value per unit volume in the fuel supplied to the gas turbine increases. As a result, due to an increase in the heat input to the turbine, effects such as excessive combustion with a sharp increase in the turbine inlet temperature occur.

[0010] In the above-mentioned Patent Document 1, when the supply of the boil-off gas mixed with the liquefied natural gas is stopped, the operating state of the gas turbine is stabilized by reducing the fuel flow rate to the gas turbine. However, in this document, the fuel flow rate is adjusted corresponding to the calorific value transition of the fuel supplied to the gas turbine accompanying the stop of the supply of the boil-off gas, so it is difficult to suppress sudden phenomena such as excessive combustion.

[0011] At least one embodiment of the present invention has been completed 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 that can suppress the influence caused by the change in the turbine inlet heat amount when at least a part of the fuel having a low heat amount per unit volume contained in the fuel supplied to the burner of the gas turbine is cut off.

[0012] Means for solving the technical problem

[0013] To solve the above problems, a gas turbine control device according to at least one embodiment of the present invention is for controlling a gas turbine, the gas turbine including a burner capable of generating combustion gas for driving the gas turbine by co-combusting a first fuel and a second fuel having a lower heat amount per unit volume than the first fuel, the gas turbine control device including: a supply state determination unit for determining the supply state of the second fuel to the burner; a fuel flow rate calculation unit at cut-off for calculating a fuel flow rate at cut-off to be supplied to the burner corresponding to the fuel co-combustion rate after at least a part of the second fuel is cut off when it is determined that the supply state is such that at least a part of the second fuel to the burner is cut off; and a fuel command value output unit for outputting a fuel flow rate command value corresponding to the fuel flow rate at cut-off before the fuel co-combustion rate becomes the fuel co-combustion rate after at least a part of the second fuel is cut off.

[0014] To solve the above problems, a gas turbine control method according to at least one embodiment of the present invention is for controlling a gas turbine, the gas turbine including a burner capable of generating combustion gas for driving the gas turbine by co-combusting a first fuel and a second fuel having a lower heat amount per unit volume than the first fuel,

[0015] The gas turbine control method includes the following steps:

[0016] Determining the supply state of the second fuel to the burner;

[0017] When it is determined that the supply state is such that at least a part of the second fuel to the burner is cut off, calculating a fuel flow rate at cut-off to be supplied to the burner corresponding to the fuel co-combustion rate after at least a part of the second fuel is cut off; and

[0018] Before the fuel mixing ratio is reached after at least a part of the second fuel is cut off, output a fuel flow command value corresponding to the fuel flow rate at the time of the cut-off.

[0019] To solve the above problems, a gas turbine control program according to at least one embodiment of the present invention is used to control a gas turbine, the gas turbine including a combustor that can generate combustion gas for driving the gas turbine by mixing a first fuel and a second fuel having a lower heat per unit volume than the first fuel.

[0020] The gas turbine control program enables a computer device to execute the following steps:

[0021] Determine the supply state of the second fuel to the combustor;

[0022] When it is determined that the supply state is such that at least a part of the second fuel to the combustor is cut off, calculate the fuel flow rate at the time of cut-off that should be supplied to the combustor corresponding to the fuel mixing ratio after at least a part of the second fuel is cut off; and

[0023] Before the fuel mixing ratio is reached after at least a part of the second fuel is cut off, output a fuel flow command value corresponding to the fuel flow rate at the time of the cut-off.

[0024] Advantages of the Invention

[0025] 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 that can suppress the influence caused by the change in the turbine inlet heat when at least a part of the fuel having a lower heat per unit volume contained in the fuel supplied to the combustor of the gas turbine is cut off. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a diagram showing a schematic configuration of a gas turbine according to an embodiment.

[0027] Figure 2 It is a block diagram showing a functional configuration of a gas turbine control device according to an embodiment.

[0028] Figure 3 It is a flowchart showing a gas turbine control method according to an embodiment.

[0029] Figure 4 It shows the Figure 3 corresponding control states of the respective structures of the gas turbine. DETAILED DESCRIPTION

[0030] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the structures described or illustrated as embodiments are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.

[0031] First, with reference to Figure 1 , the gas turbine 1, which is the control object of the gas turbine control device 50 according to at least one embodiment of the present invention, will be described. Figure 1 FIG. is a schematic diagram showing the general structure of the gas turbine 1 according to one embodiment.

[0032] The gas turbine 1 includes a compressor 3 that generates compressed air, a combustor 2 that generates combustion gas by mixing and burning 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 that is driven by the combustion gas. The compressor 3 and the turbine 6 are connected by a single shaft. In the gas turbine 1 having such a 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, and these are mixed and burned to generate combustion gas. This combustion gas flows into the turbine 6 and acts as power to rotate the turbine 6.

[0033] The fuel supply system 4 processes a mixed fuel in which the first fuel F1 and the second fuel F2 are mixed as the fuel supplied to the combustor 2. The second fuel F2 is a fuel having a lower heat per unit volume than the first fuel F1. In the present embodiment, the first fuel F1 is liquefied natural gas and the second fuel F2 is hydrogen.

[0034] The first fuel F1 is supplied via a first fuel supply line 8 connected to the first fuel supply source 7. A flowmeter 10 for detecting the flow rate of the first fuel F1 is provided on the first fuel supply line 8.

[0035] The second fuel F2 is supplied via a second fuel supply line 16 connected to the second fuel supply source 14. A first flow control valve 18 for adjusting the flow rate of the second fuel F2 and a shut-off valve 13 for shutting off the second fuel F2 are provided on the second fuel supply line 16.

[0036] The first fuel supply line 8 and the second fuel supply line 16 converge 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 converging at the convergence point 25 of the first fuel supply line 8 and the second fuel supply line 16, and the mixed fuel (hereinafter, appropriately referred to as "mixed fuel Fm") is transported through the main fuel supply line 22.

[0037] In addition, a shut-off valve 24 for shutting off the mixed fuel Fm and a second flow control valve 26 for adjusting the flow rate of the mixed fuel Fm are provided on the main fuel supply line 22.

[0038] The downstream side of the main fuel supply pipe 22 branches into a plurality of fuel branch supply pipes 28a, 28b,......, corresponding to a plurality of fuel injection nozzles (not shown) provided in the burner 2. The plurality of fuel injection nozzles may include a main fuel injection nozzle, a pilot fuel injection nozzle, a top hat fuel injection nozzle, etc. At this time, at least a part of the main fuel injection nozzles may be grouped. Flow rate regulating valves 30a, 30b,...... for adjusting the flow rate of the mixed fuel flowing in each pipe are respectively provided on the plurality of fuel branch supply pipes 28a, 28b,......

[0039] Next, a gas turbine control device 50 for controlling the gas turbine 1 having the above structure will be described. The gas turbine control device 50 is a control unit for controlling the gas turbine 1 and is composed of, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium. Moreover, as an example, a series of processes for realizing various functions are stored in a storage medium or the like in the form of a program, and the CPU reads the program into the RAM or the like and executes information processing / arithmetic processing, thereby realizing various functions. In addition, the program can also be applied in a manner of being pre-installed in the ROM or other storage media, in a state of being stored in a computer-readable storage medium, in a manner of being transmitted via wired or wireless communication means, etc. The computer-readable storage medium refers to a magnetic disk, an optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, etc.

[0040] Figure 2 It is a block diagram showing the functional structure of the gas turbine control device 50 according to an embodiment. The gas turbine control device 50 includes a cut-off determination unit 19, a fuel flow rate command value calculation unit 20, and a fuel flow rate control unit 29.

[0041] The cut-off determination unit 19 is a structure for determining whether at least a part of the second fuel F2 is cut off in the fuel supply system 4. For example, the cut-off determination unit 19 determines whether at least a part of the second fuel F2 is cut off based on the open / closed state of the cut-off valve 21 provided on the second fuel supply pipe 16 through which the second fuel F2 flows.

[0042] In Figure 1In the illustrated fuel supply system 4, the case where the second fuel F2 is supplied from a single second fuel supply source 14 via a single second fuel supply pipe 16 is exemplified. When the second fuel F2 cannot be supplied from the second fuel supply source 14 for some reason or when a blockage occurs in the second fuel supply pipe 16, the cut-off valve 13 is closed. When the cut-off determination unit 19 detects that the second fuel F2 is cut off based on the opening / closing state of such a cut-off valve 21, it outputs a cut-off detection signal Sa indicating this content.

[0043] In addition, in the following description, as the case where the second fuel F2 is cut off, the case where the second fuel F2 is completely cut off is described. However, for example, in the case where the second fuel supply pipe 16 branches into a plurality and the second fuel F2 can be supplied from a plurality of second fuel supply sources 14, at least a part of the second fuel F2 can be cut off by closing the cut-off valve 21 provided in a part of the second fuel supply pipe 16. At this time, by also setting the cut-off detection signal Sa to a signal corresponding to the cut-off amount of the second fuel F2, it can be handled equally.

[0044] The fuel flow command value calculation unit 20 acquires state quantities (turbine output P, rotational speed R, exhaust gas temperature EXT, blade passage temperature BPT, etc.) related to the operating state of the gas turbine 1 as input signals, and outputs a fuel flow command value CSO obtained through calculation. The fuel flow control unit 29 receives the input of the fuel flow command value CSO from the fuel flow command value calculation unit 20, and adjusts the fuel flow supplied by the fuel supply system 4 based on this fuel flow command value CSO.

[0045] The fuel flow command value calculation unit 20 includes a first fuel flow command value calculation unit 20a, a second fuel flow command value calculation unit 20b, a third fuel flow command value calculation unit 20c, a fourth fuel flow command value calculation unit 20d, and a low value selection unit 20e. The first fuel flow command value calculation unit 20a to the fourth fuel flow command value calculation unit 20d respectively calculate corresponding first fuel flow command values CSO1 to fourth fuel flow command values CSO4. The low value selection unit 20e selects and outputs the minimum value among the first fuel flow command values CSO1 to fourth fuel flow command values CSO4 as the fuel flow command value SCO.

[0046] The first fuel flow command value calculation unit 20a has a normal-time fuel flow command value calculation unit 20a1 and a cut-off-time fuel flow command value calculation unit 20a2 that can be switched with each other according to the operating mode of the gas turbine 1. The switching between the normal-time fuel flow command value calculation unit 20a1 and the cut-off-time fuel flow command value calculation unit 20a2 is performed based on the cut-off detection signal Sa input from the cut-off determination unit 19 to the first fuel flow command value calculation unit 20a.

[0047] When the fuel supply system 4 is in the normal state (i.e., the state in which the second fuel F2 is not cut off according to the cut-off detection signal Sa), the first fuel flow command value calculation unit 20a calculates the first fuel flow command value CSO1 through the normal-time fuel flow command value calculation unit 20a1. In the normal-time fuel flow command value calculation unit 20a1, the turbine output P and the target turbine output Pref corresponding to the turbine output P in the input signals for the fuel flow command value calculation unit 20 are input, and based on these deviations ΔP, a candidate for the fuel flow command value CSO, i.e., the first fuel flow command value CSO2, is calculated.

[0048] In the calculation of the first fuel flow command value CSO in the normal-time fuel flow command value calculation unit 20a1, the correlation between the deviation ΔP and the first fuel flow command value CSO1 is prepared in advance, and by inputting the deviation ΔP into this correlation, the corresponding first fuel flow command value CSO1 is obtained. This correlation is prepared in advance corresponding to the fuel mixing ratio of the first fuel F1 and the second fuel F2 obtained from the fuel supply system 4.

[0049] When the fuel supply system 4 is in the cut-off state (i.e., the state in which at least a part of the second fuel F2 is cut off according to the cut-off detection signal Sa), the first fuel flow command value calculation unit 20a calculates the first fuel flow command value CSO1 through the cut-off-time fuel flow command value calculation unit 20a2. In the cut-off-time fuel flow command value calculation unit 20a2, the turbine output P and the target turbine output Pref corresponding to the turbine output P in the input signals for the fuel flow command value calculation unit 20 are input, and based on these deviations ΔP, a candidate for the fuel flow command value CSO, i.e., the first fuel flow command value CSO2, is calculated.

[0050] In the calculation of the first fuel flow command value CSO in the cut-off-time fuel flow command value calculation unit 20a2, the correlation between the deviation ΔP and the first fuel flow command value CSO1 is prepared in advance, and by inputting the deviation ΔP into this correlation, the corresponding first fuel flow command value CSO1 is obtained. This correlation is prepared in the fuel supply system 4 corresponding to the fuel mixing ratio, which corresponds to the case where at least a part of the second fuel F2 is assumed to be cut off corresponding to the cut-off signal Sa.

[0051] The second fuel flow command value calculation unit 20b is a structure for calculating a candidate for the fuel flow command value CSO, i.e., the second fuel flow command value CSO2. In the second fuel flow command value calculation unit 20b, the rotational speed R and the target rotational speed Rref corresponding to the rotational speed R in the input signals for the fuel flow command value calculation unit 20 are input, and based on these deviations ΔR, the second fuel flow command value CSO2 is calculated.

[0052] The third fuel flow command value calculation unit 20c is configured to calculate the third fuel flow command value CSO3, which is one candidate for the fuel flow command value CSO. In the third fuel flow command value calculation unit 20c, the exhaust gas temperature EXT and the target exhaust gas temperature EXTref corresponding to the exhaust gas temperature EXT in the input signal for the fuel flow command value calculation unit 20 are input, and the third fuel flow command value CSO3 is calculated based on these deviations ΔEXT.

[0053] The fourth fuel flow command value calculation unit 20d is configured to calculate the fourth fuel flow command value CSO4, which is one candidate for the fuel flow command value CSO. In the fourth fuel flow command value calculation unit 20d, the blade passage temperature BPT and the target blade passage temperature BPTref corresponding to the blade passage temperature BPT in the input signal for the fuel flow command value calculation unit 20 are input, and the fourth fuel flow command value CSO4 is calculated based on these deviations ΔBPT.

[0054] Next, a turbine control method implemented by the gas turbine control device 50 having the above structure will be described. Figure 3 It is a flowchart showing a gas turbine control method according to an embodiment. Figure 4 It is shown in Figure 3 The timing chart of the control states of the respective structures of the gas turbine 1 corresponding to.

[0055] First, the gas turbine control device 50 controls the gas turbine 1 in the normal control mode (step S1). In the normal control mode, in the fuel supply system 4, since both the first fuel F1 and the second fuel F2 are normally supplied, the mixed fuel Fm is supplied to the burner 2. At this time, in the first fuel flow command value calculation unit 20a, the calculation of the first fuel flow command value CSO1 is performed by the normal fuel flow command value calculation unit 20a1.

[0056] In addition, in the present embodiment, for the sake of convenience of explanation, in the fuel flow command value calculation unit 20a, the case where the first fuel flow command value CSO1 is always selected as the fuel flow command value CSO in the low-value selection unit 20e because the second fuel flow command value CSO2 to the fourth fuel flow command value CSO4 are larger than the first fuel flow command value CSO1 will be described.

[0057] Next, the cut-off determination unit 19 determines whether at least a part of the second fuel F2 is cut off in the fuel supply system 4 (step S2). In step S2, in the gas turbine 1 controlled in the normal control mode, the fuel supply system 4 is monitored to determine whether the second fuel F2 is cut off. This determination can be made, for example, based on the opening degree of the cut-off valve 21 provided in the second fuel supply line 16 of the fuel supply system 4.

[0058] When it is determined by the cutoff determination unit 19 that at least a part of the second fuel F2 has been cut off (step S2: Yes), the gas turbine control device 50 switches from the normal control mode to the cutoff control mode (step S3). In the cutoff control mode, the calculation of the first fuel flow command value CSO1 in the first fuel flow command value calculation unit 20a is performed by the cutoff fuel flow command value calculation unit 20a2.

[0059] The cutoff fuel flow command value calculation unit 20a2 calculates the fuel mixing ratio after the second fuel F2 is cut off, and obtains the first fuel flow command value CSO1 by calculating the cutoff fuel flow that should be supplied to the burner 2 corresponding to this fuel mixing ratio. In the present embodiment, since the second fuel F2 is cut off, 100% of the fuel mixing ratio after the cutoff is the first fuel F1. Therefore, assuming that the mixed fuel Fm is only the first fuel F1, the first fuel flow command value CSO1 corresponding to the cutoff fuel flow that should be supplied to the burner 2 is calculated.

[0060] In addition, the correlation between the cutoff fuel flow and the turbine output is prepared in advance for each fuel mixing ratio. In the present embodiment, the correlation corresponding to the fuel mixing ratio when the first fuel F1 is cut off is prepared in advance, and the cutoff fuel flow corresponding to the current turbine output is calculated based on this correlation.

[0061] In Figure 4 , when the cutoff of the second fuel F2 is detected by the cutoff determination unit 19 at time t1, the first fuel flow command value CSO1 calculated by the normal fuel flow command value calculation unit 20a1 is switched to the first fuel flow command value CSO1 calculated by the cutoff fuel flow command value calculation unit 20a2. Since the heat per unit volume of the second fuel F2 is lower than that of the first fuel F1, the first fuel command value CSO1 calculated by the cutoff fuel flow command value calculation unit 20a2 becomes a value lower than the first fuel flow command value CSO1 calculated by the normal fuel flow command value calculation unit 20a1. Here, in the fuel supply system 4, there is a predetermined distance between the cutoff valve 13 and the burner 2, and there is a time lag from the start of the cutoff of the second fuel F2 until the fuel mixing ratio of the first fuel F1 in the burner 2 actually becomes high. In Figure 4In this case, before time t3, in the burner 2, the flow rate before cutoff remains unchanged, and the fuel co - firing rate also remains unchanged. On the other hand, the distance between the second flow rate regulating valve 26 for adjusting the flow rate of the mixed fuel Fm and the burner 2 is shorter than the distance between the cutoff valve 13 and the burner 2. Therefore, by immediately switching to the first fuel flow rate command value CSO1 calculated by the fuel flow rate command value calculation unit 20a2 at the time of cutoff after the cutoff of the cutoff valve 13, the heat input to the burner can be reduced before the fuel co - firing rate of the first fuel F1 in the burner actually becomes higher. In Figure 4 In this case, at time t2 when a time difference Δt has elapsed from time t1, the turbine inlet temperature T1T and the gas turbine load GTLoad decrease.

[0062] Next, the gas turbine control device 50 determines whether a predetermined time tp has elapsed since the switching to the control mode at the time of cutoff (step S4). The predetermined time tp is set to be larger than the time when the fuel co - firing rate of the first fuel F1 in the burner actually becomes higher after the second fuel F2 is cutoff at time t1. Therefore, from time t1 to the predetermined time tp, by effectively maintaining the control mode at the time of cutoff, compared with the normal control mode, the turbine inlet temperature T1T decreases, and thus the influence of excessive combustion can be effectively suppressed. In Figure 4 In this case, the predetermined time tp is set to a value larger than the time difference "t3 - t1". The fuel flow rate of the second fuel F2 decreases due to the cutoff of the cutoff valve 13, and the influence caused by the increase in the fuel co - firing rate of the first fuel F1 appears in the burner 2 at time t3, and the turbine inlet temperature T1T and the gas turbine load GTLoad increase sharply. However, since the flow rate of the mixed fuel is already more restricted than before cutoff and the heat input to the burner 2 also decreases, excessive combustion is effectively suppressed.

[0063] In addition, immediately after the second fuel F2 is cutoff, there remains the second fuel F2 supplied before cutoff on the downstream side of the confluence point 25 in the main fuel supply line 22. Therefore, the time t3 when excessive combustion occurs is delayed by the time required for the second fuel F2 remaining in the main fuel supply line 22 to be consumed by the burner 2 from the time t1 when the second fuel F2 is cutoff. In step S4, by maintaining the control mode at the time of cutoff from time t1 until the predetermined time tp, the flow rate of the mixed fuel Fm is restricted until the time when the influence of excessive combustion occurs with a time lag, and the turbine inlet temperature T1T is reduced in advance, thereby mitigating its influence.

[0064] Moreover, when a prescribed time tp has elapsed since the control mode was switched to the cut-off mode (step S4: YES), the gas turbine control device 50 returns the gas turbine 1 from the cut-off mode to the normal control mode (step S5). In this way, when a sufficient period (prescribed time) has elapsed since time t1 and the state where excessive combustion cannot occur is reached, by returning the control mode of the gas turbine 1 to the normal control mode, a smooth return to normal operation can be achieved.

[0065] As described above, according to each of the above embodiments, when at least a part of the second fuel F2 mixed with the first fuel F1 is cut off, the cut-off fuel flow rate corresponding to the fuel mixing ratio after the cut-off is calculated and reflected in the fuel flow command value CSO before the change in the fuel mixing ratio caused by the cut-off occurs. Thus, before the influence of the cut-off of at least a part of the second fuel F2 appears in the operating state of the gas turbine 1, the fuel flow command value CSO is set to a value corresponding to the fuel mixing value after the cut-off, and even when excessive combustion occurs, its influence can be effectively alleviated.

[0066] In addition, within the scope not departing from the gist of the present invention, the constituent elements in the above embodiments can be appropriately replaced with well-known constituent elements, and the above embodiments can be appropriately combined.

[0067] The content described in each of the above embodiments can be grasped as follows, for example.

[0068] (1) A gas turbine control device according to one embodiment is for controlling a gas turbine, and the gas turbine includes a combustor that can generate combustion gas for driving the gas turbine by mixing a first fuel and a second fuel having a lower heat per unit volume than the first fuel.

[0069] The gas turbine control device includes:

[0070] A supply state determination unit for determining the supply state of the second fuel to the combustor;

[0071] A cut-off fuel flow rate calculation unit for calculating a cut-off fuel flow rate to be supplied to the combustor corresponding to the fuel mixing ratio after at least a part of the second fuel is cut off when it is determined that the supply state is such that at least a part of the second fuel to the combustor is cut off; and

[0072] A fuel command value output unit for outputting a fuel flow command value corresponding to the cut-off fuel flow rate before the fuel mixing ratio becomes the fuel mixing ratio after at least a part of the second fuel is cut off.

[0073] According to the method in (1) above, when at least a part of the second fuel mixed with the first fuel is cut off, the fuel flow rate at the time of cut-off corresponding to the fuel mixing ratio after the cut-off is calculated and reflected in the fuel flow rate command value before the change in the fuel mixing ratio caused by the cut-off occurs. Thus, before the influence of the cut-off of at least a part of the second fuel appears in the operating state of the gas turbine, the fuel flow rate command value is set to a value corresponding to the fuel mixing value after the cut-off, and even in the case of excessive combustion, its influence can be effectively alleviated.

[0074] (2) In another method, in the method in (1) above,

[0075] The fuel flow rate calculation unit at the time of cut-off calculates the fuel flow rate at the time of cut-off corresponding to the current output of the gas turbine according to the correlation between the output of the gas turbine at the fuel mixing ratio and the fuel flow rate at the time of cut-off.

[0076] According to the method in (2) above, the correlation between the fuel flow rate at the time of cut-off when at least a part of the second fuel is cut off and the output of the gas turbine is prepared in advance. In the gas turbine, when at least a part of the second fuel is cut off, the fuel flow rate at the time of cut-off corresponding to the current output of the gas turbine is calculated according to this correlation.

[0077] (3) In other methods, in the method in (1) or (2) above,

[0078] The fuel flow rate at the time of cut-off is valid within a specified period after it is determined that the supply state is such that at least a part of the second fuel for the burner is cut off.

[0079] According to the method in (3) above, the fuel flow rate at the time of cut-off calculated when at least a part of the second fuel is cut off is valid within a specified period. Thus, even in the case of excessive combustion during this period, its influence can be effectively alleviated.

[0080] (4) In other methods, in the method in (3) above, it further includes:

[0081] A target quantity calculation unit for calculating the fuel flow rate to be supplied to the burner according to the target output value and the current output value of the gas turbine,

[0082] After the specified time has elapsed, the fuel command value output unit switches from the cut-off time control mode of outputting the fuel flow rate command value corresponding to the total fuel flow rate that should be supplied corresponding to the fuel mixing ratio to the normal time control mode of outputting the fuel flow rate command value using the fuel flow rate calculated by the target quantity calculation unit.

[0083] After the specified time during which the fuel flow rate is considered effective when cut off according to the method in (4) above, the control mode is switched from the cut-off time control mode to the normal time control mode, whereby the operating state of the gas turbine can be smoothly restored to normal.

[0084] (5) In other methods, in any one of the methods in (1) to (4) above,

[0085] The first fuel is natural gas and the second fuel is hydrogen.

[0086] According to the method in (5) above, in a gas turbine in which natural gas and hydrogen are co-fired, when at least a part of the hydrogen is cut off, the influence caused by the change in the heat input to the turbine can be effectively suppressed.

[0087] (6) A gas turbine control method according to one aspect is for controlling a gas turbine, the gas turbine including a burner capable of generating combustion gas for driving the gas turbine by co-firing a first fuel and a second fuel having a lower heat per unit volume than the first fuel,

[0088] The gas turbine control method includes the following steps:

[0089] Determine the supply state of the second fuel to the burner;

[0090] When it is determined that the supply state is such that at least a part of the second fuel to the burner is cut off, calculate the fuel flow rate at the time of cut-off that should be supplied to the burner corresponding to the fuel co-firing rate after at least a part of the second fuel is cut off; and

[0091] Before the fuel co-firing rate becomes the fuel co-firing rate after at least a part of the second fuel is cut off, output a fuel flow rate command value corresponding to the fuel flow rate at the time of cut-off.

[0092] According to the method in (6) above, when at least a part of the second fuel co-fired with the first fuel is cut off, calculate the fuel flow rate at the time of cut-off corresponding to the fuel co-firing rate after the cut-off, and reflect it in the fuel flow rate command value before the change in the fuel co-firing rate caused by the cut-off occurs. Thus, before the influence of the cut-off of at least a part of the second fuel appears in the operating state of the gas turbine, the fuel flow rate command value is set to a value corresponding to the fuel co-firing value after the cut-off, and even in the case of excessive combustion, its influence can be effectively alleviated.

[0093] (7) A gas turbine control program according to one aspect is for controlling a gas turbine, the gas turbine including a burner capable of generating combustion gas for driving the gas turbine by co-firing a first fuel and a second fuel having a lower heat per unit volume than the first fuel,

[0094] The gas turbine control program enables a computer device to perform the following processes:

[0095] Determine the supply state of the second fuel for the burner;

[0096] When it is determined that the supply state is such that at least a part of the second fuel for the burner is cut off, calculate the fuel flow rate at the time of cut-off that should be supplied to the burner corresponding to the fuel mixing ratio after at least a part of the second fuel is cut off; and

[0097] Before the fuel mixing ratio becomes the fuel mixing ratio after at least a part of the second fuel is cut off, output a fuel flow rate command value corresponding to the fuel flow rate at the time of cut-off.

[0098] According to the method in (7) above, when at least a part of the second fuel mixed with the first fuel is cut off, calculate the fuel flow rate at the time of cut-off corresponding to the fuel mixing ratio after the cut-off, and reflect it in the fuel flow rate command value before the change in the fuel mixing ratio caused by the cut-off occurs. Thus, before the influence of the cut-off of at least a part of the second fuel appears in the operating state of the gas turbine, the fuel flow rate command value is set to a value corresponding to the fuel mixing value after the cut-off. Even in the case of excessive combustion, its influence can be effectively alleviated.

[0099] Symbol Explanation

[0100] 1 - Gas turbine, 2 - Burner, 3 - Compressor, 4 - Fuel supply system, 6 - Turbine, 7 - First fuel supply source, 8 - First fuel supply pipeline, 10 - Flow meter, 13 - Shut-off valve, 14 - Second fuel supply source, 16 - Second fuel supply pipeline, 18 - First flow control valve, 19 - Cut-off determination unit, 20 - Fuel flow rate command value calculation unit, 20a - First fuel flow rate command value calculation unit, 20a1 - Normal fuel flow rate command value calculation unit, 20a2 - Fuel flow rate command value calculation unit at the time of cut-off, 20b - Second fuel flow rate command value calculation unit, 20c - Third fuel flow rate command value calculation unit, 20d - Fourth fuel flow rate command value calculation unit, 20e - Low value selection unit, 22 - Main fuel supply pipeline, 25 - Confluence point, 26 - Second flow control valve, 28a - 28d - Fuel branch supply pipelines, 29 - Fuel flow control unit, 30a - 30d - Third flow control valves, 50 - Gas turbine control device, F1 - First fuel, F2 - Second fuel, Fm - Mixed fuel.

Claims

1. A gas turbine control device for controlling a gas turbine, the gas turbine having a burner capable of generating combustion gas for driving the gas turbine by co-combusting a first fuel and a second fuel having a lower heat per unit volume than the first fuel. The gas turbine control device includes: a supply state determination unit for determining the supply state of the second fuel to the burner; a cut-off fuel flow rate calculation unit for calculating a cut-off fuel flow rate to be supplied to the burner corresponding to a fuel co-combustion rate after at least a part of the second fuel to the burner is determined to be in a cut-off supply state; and a fuel command value output unit for outputting a fuel flow rate command value corresponding to the cut-off fuel flow rate before the fuel co-combustion rate is reached after at least a part of the second fuel is cut off.

2. The gas turbine control device according to claim 1, wherein the cut-off fuel flow rate calculation unit calculates the cut-off fuel flow rate corresponding to the current output of the gas turbine based on the correlation between the output of the gas turbine at the fuel co-combustion rate and the cut-off fuel flow rate.

3. The gas turbine control device according to claim 1 or 2, wherein the cut-off fuel flow rate is valid within a specified period after it is determined that at least a part of the second fuel to the burner is in a cut-off supply state.

4. The gas turbine control device according to claim 3, further comprising: a target quantity calculation unit for calculating a fuel flow rate to be supplied to the burner based on a target output value and a current output value of the gas turbine, and the fuel command value output unit switches from a cut-off time control mode of outputting a fuel flow rate command value corresponding to the total fuel flow rate to be supplied corresponding to the fuel co-combustion rate to a normal time control mode of outputting the fuel flow rate command value using the fuel flow rate calculated by the target quantity calculation unit after the specified time has elapsed.

5. The gas turbine control device according to claim 1 or 2, wherein the first fuel is natural gas and the second fuel is hydrogen.

6. A gas turbine control method for controlling a gas turbine, the gas turbine having a burner capable of generating combustion gas for driving the gas turbine by co-combusting a first fuel and a second fuel having a lower heat per unit volume than the first fuel. The gas turbine control method includes the following steps: determining the supply state of the second fuel to the burner; calculating a cut-off fuel flow rate to be supplied to the burner corresponding to a fuel co-combustion rate after at least a part of the second fuel to the burner is determined to be in a cut-off supply state; and outputting a fuel flow rate command value corresponding to the cut-off fuel flow rate before the fuel co-combustion rate is reached after at least a part of the second fuel is cut off.

7. A gas turbine control program for controlling a gas turbine, the gas turbine having a burner capable of generating combustion gas for driving the gas turbine by co-combusting a first fuel and a second fuel having a lower heat per unit volume than the first fuel. The gas turbine control program enables a computer device to perform the following steps: Determine the supply state of the second fuel to the burner; When it is determined that the supply state is such that at least a part of the second fuel to the burner is cut off, calculate the fuel flow rate at the time of cut-off that should be supplied to the burner corresponding to the fuel co-combustion rate after at least a part of the second fuel is cut off; and Before the fuel co-combustion rate is reached after at least a part of the second fuel is cut off, output a fuel flow rate command value corresponding to the fuel flow rate at the time of cut-off.

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