Fuel control device, fuel control method, and program

Abstract

To prevent flashback from occurring even when the load is reduced by using simple control. [Solution] The system includes: a determination unit that determines whether a predetermined decrease in load has occurred in a gas turbine load supplied with a mixed gas obtained by mixing a first fuel gas with a second fuel gas having a faster combustion rate than the first fuel gas; a correction unit that, when the determination unit determines that the predetermined decrease has occurred, sets a bias value to a predetermined bias start value and performs a correction to reduce the bias value for a control reference mixing ratio, which indicates the proportion of the second fuel gas in the mixed gas and whose difference from an actually measured mixing ratio is used as a deviation for control; and a valve opening calculation unit that calculates a valve opening of a second fuel gas flow rate control valve that adjusts the flow rate of the second fuel gas, based on the actually measured mixing ratio and the corrected control reference mixing ratio.

Description

[Technical Field]

[0001] The present disclosure relates to a fuel control device, a fuel control method, and a program. [Background technology]

[0002] In recent years, with the aim of decarbonization, mixed gases in which hydrogen gas, which does not emit CO2, is mixed with natural gas, the main fuel for gas turbines, have been used as fuel for gas turbines.When using such mixed gases as fuel for gas turbines, the amount of hydrogen gas mixed with the natural gas is adjusted to control the hydrogen mixture ratio, which indicates the proportion of hydrogen gas contained in the mixed gas, to a target value set by the operator.

[0003] For example, in the two graphs shown in Figure 9, the graph in Figure 9(a) shows the change over time in the hydrogen mixing ratio [%], and the graph in Figure 9(b) shows the change over time in the load factor [%] of the gas turbine. As shown by the broken line labeled 500 in Figure 9(b), assume that at time tA, for example, a load change operation or runback is performed on the gas turbine. In this case, the amount of mixed gas supplied to the gas turbine decreases, and the load factor decreases after time tA. In contrast, as shown by the broken line labeled 300 in Figure 9(a), the supply amount of hydrogen gas is maintained for a while due to a delay in control to set the hydrogen mixing ratio to the target value, and therefore the hydrogen mixing ratio increases after time tA.

[0004] If the mixed gas contains a large amount of hydrogen gas, which has a high combustion rate, flashback may occur in the combustor of the gas turbine. To prevent the combustor from burning out due to flashback, the gas turbine is provided with an interlock that trips the gas turbine at time tB, for example, when the value of the broken line indicated by reference numeral 300 in Figure 9(a) reaches the threshold indicated by the dotted line indicated by reference numeral 400. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2022 / 149540 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if the gas turbine suddenly stops due to the above-mentioned interlock, this will reduce operability, and therefore there are circumstances in which it is desirable to carry out control that avoids the interlock in the first place.

[0007] For example, Patent Document 1 discloses a technology for preventing flashback by individually adjusting the amounts of natural gas and hydrogen gas supplied to the main fuel injector and the pilot fuel injector, respectively.

[0008] In a gas turbine that receives a mixed gas of natural gas and hydrogen gas, a typical configuration is to provide one flow control valve for each fuel injector, and to supply each fuel injector with a mixed gas having the same ratio of natural gas to hydrogen gas. In this configuration, a single flow control valve is provided exclusively for hydrogen gas, and the flow rate of the hydrogen gas is adjusted by this flow control valve to control the hydrogen mixing ratio of the mixed gas to a target value.

[0009] In contrast, the technology of Patent Document 1 does not set the hydrogen mixture ratio in the mixed gas to a target value, but rather adjusts the ratio of natural gas and hydrogen gas supplied to each fuel injector individually. To achieve this, the technology of Patent Document 1 provides two flow control valves for each fuel injector: one for natural gas and one for hydrogen gas. This requires many flow control valves, and also requires control to determine the valve opening for each flow control valve, resulting in more complex control than that required for a typical gas turbine.

[0010] The present disclosure has been made in consideration of the above circumstances, and aims to provide a fuel control device, a fuel control method, and a program that can prevent flashback from occurring even when the load is reduced through simple control. [Means for solving the problem]

[0011] In order to solve the above problems, a fuel control device according to the present disclosure includes: a determination unit that determines whether a predetermined decrease in load has occurred in a gas turbine to which a mixed gas obtained by mixing a first fuel gas and a second fuel gas having a faster combustion speed than the first fuel gas is supplied; a correction unit that, when the determination unit determines that the predetermined decrease in load has occurred, sets a bias value to a predetermined bias start value and performs a correction to reduce the bias value on a control reference mixing ratio, which indicates the proportion of the second fuel gas in the mixed gas and whose difference from an actual measured mixing ratio is used as a deviation for control; and a valve aperture calculation unit that calculates a valve aperture of a second fuel gas flow rate control valve that adjusts a flow rate of the second fuel gas, based on the actual measured mixing ratio and the corrected control reference mixing ratio.

[0012] A fuel control method according to the present disclosure determines whether a predetermined decrease in load has occurred in a gas turbine to which a mixed gas obtained by mixing a first fuel gas and a second fuel gas having a faster combustion speed than the first fuel gas is supplied, and if it is determined that the predetermined decrease has occurred, sets a bias value to a predetermined bias start value, corrects a control reference mixing ratio, which indicates the proportion of the second fuel gas in the mixed gas and whose difference from an actually measured mixing ratio is used as a deviation for control, by decreasing the bias value, and calculates a valve aperture of a second fuel gas flow rate control valve that adjusts a flow rate of the second fuel gas, based on the actually measured mixing ratio and the corrected control reference mixing ratio.

[0013] A program according to the present disclosure causes a computer to function as: a determination means for determining whether a predetermined decrease has occurred in the load of a gas turbine to which a mixed gas obtained by mixing a first fuel gas with a second fuel gas having a faster combustion speed than the first fuel gas is supplied; a correction means for, when the determination means determines that the predetermined decrease has occurred, setting a predetermined bias start value for a bias value and correcting a control reference mixing ratio, which indicates the proportion of the second fuel gas in the mixed gas and whose difference from an actually measured mixing ratio is used as a deviation for control, by reducing the bias value; and a valve aperture calculation means for calculating a valve aperture of a second fuel gas flow rate control valve that adjusts a flow rate of the second fuel gas, based on the actually measured mixing ratio and the corrected control reference mixing ratio. [Effects of the Invention]

[0014] According to the fuel control device, fuel control method, and program of the present disclosure, flashback can be prevented from occurring even when the load is reduced through simple control. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram illustrating an example configuration of a gas turbine power plant according to an embodiment of the present disclosure. [Figure 2] 1 is a block diagram illustrating an example of an internal configuration of a fuel control device according to an embodiment of the present disclosure and an example of a connection configuration of devices connected to the fuel control device. FIG. [Figure 3] FIG. 10 is a diagram illustrating an example of values ​​stored in a storage unit according to an embodiment of the present disclosure. [Figure 4] 4 is a flowchart illustrating an example of the operation of a determination unit of the fuel control device according to the embodiment of the present disclosure. [Figure 5] 4 is a flowchart illustrating an example of the operation of a correction unit of the fuel control device according to the embodiment of the present disclosure. [Figure 6] 4 is a flowchart illustrating an example of an operation when calculating a valve opening degree of a hydrogen gas flow rate control valve in a fuel control device according to an embodiment of the present disclosure. [Figure 7] 6 is a graph showing changes over time in hydrogen mixing ratio, bias value, and power value according to the present disclosure. [Figure 8] FIG. 1 is a schematic block diagram illustrating the configuration of a computer according to at least one embodiment. [Figure 9] 1 is a graph showing the change over time in the load factor and the change over time in the hydrogen mixing ratio of a typical gas turbine. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a fuel control device, a fuel control method, and a program according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the same or corresponding components in the drawings will be denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0017] (Gas turbine power plant configuration) 1 is a block diagram showing an example configuration of a gas turbine power plant 1 according to an embodiment of the present disclosure. The gas turbine power plant 1 includes a gas turbine 2, a natural gas fuel supply line 3, a hydrogen gas fuel supply line 4, a mixed gas fuel supply line 5, a fuel control device 6, a fuel supply line connection unit 10, a wattmeter 11, a thermometer 12, a pressure gauge 13, and a CSO signal output device 14.

[0018] The fuel supply line connection unit 10 is a three-way joint that connects, for example, the piping of three fuel supply lines: the natural gas fuel supply line 3, the hydrogen gas fuel supply line 4, and the mixed gas fuel supply line 5. At the fuel supply line connection unit 10, natural gas flows in from the natural gas fuel supply line 3, hydrogen gas flows in from the hydrogen gas fuel supply line 4, and a mixed gas of natural gas and hydrogen gas flows out to the mixed gas fuel supply line 5.

[0019] The natural gas fuel supply line 3 includes a natural gas supply source 31, a compressor 32, and a natural gas flow meter 33. Pipes are connected between the natural gas supply source 31 and the compressor 32, between the compressor 32 and the natural gas flow meter 33, and between the natural gas flow meter 33 and the fuel supply line connection part 10. Natural gas supplied from the natural gas supply source 31 is compressed by the compressor 32, and the compressed natural gas flows into the fuel supply line connection part 10 via the natural gas flow meter 33.

[0020] The hydrogen gas fuel supply line 4 includes a hydrogen gas supply source 41, a hydrogen gas flow meter 42, and a hydrogen gas flow rate control valve 43. Piping is provided between the hydrogen gas supply source 41 and the hydrogen gas flow rate meter 42, between the hydrogen gas flow rate meter 42 and the hydrogen gas flow rate control valve 43, and between the hydrogen gas flow rate control valve 43 and the fuel supply line connection part 10. Hydrogen gas supplied from the hydrogen gas supply source 41 flows into the hydrogen gas flow rate control valve 43 via the hydrogen gas flow meter 42. Hydrogen gas flows out of the hydrogen gas flow rate control valve 43 at a flow rate corresponding to the valve opening of the hydrogen gas flow rate control valve 43 and flows into the fuel supply line connection part 10. When the hydrogen gas flow rate control valve 43 receives a signal including the valve opening from the fuel control device 6, it opens or closes the valve to the valve opening included in the received signal.

[0021] Each of the natural gas flow meter 33 and the hydrogen gas flow meter 42 is, for example, a flow meter that measures the volumetric flow rate of a fluid passing through it. The natural gas flow meter 33 performs measurements, for example, at regular intervals, and outputs the volumetric flow rate of natural gas obtained by the measurements to the fuel control device 6. The hydrogen gas flow meter 42 performs measurements repeatedly, for example, at regular intervals, and outputs the volumetric flow rate of hydrogen gas obtained by the measurements to the fuel control device 6.

[0022] The mixed gas fuel supply line 5 includes three fuel supply systems to the gas turbine 2: a top hat fuel supply system 5-T, a pilot fuel supply system 5-P, and a main fuel supply system 5-M. The mixed gas fuel supply line 5 includes an inlet pipe 51, flow rate control valves 52T, 52P, and 52M, and outlet pipes 53T, 53P, and 53M. One end of the inlet pipe 51 is connected to a fuel supply line connection unit 10, and the other three ends are connected to one end of each of the flow rate control valves 52T, 52P, and 52M. The inlet pipe 51 branches the mixed gas flowing in from the fuel supply line connection unit 10 into three directions.

[0023] The mixed gas branched by the inlet pipe 51 flows into flow rate control valves 52T, 52P, and 52M. The other ends of the flow rate control valves 52T, 52P, and 52M are connected to outlet pipes 53T, 53P, and 53M, respectively. The mixed gas flows out from the other ends of the flow rate control valves 52T, 52P, and 52M at flow rates corresponding to the valve apertures of the flow rate control valves 52T, 52P, and 52M, and is supplied to the gas turbine 2 via the outlet pipes 53T, 53P, and 53M. When the flow rate control valves 52T, 52P, and 52M receive a signal including the valve aperture from the fuel control device 6, they open or close the valve so as to achieve the valve aperture included in the received signal.

[0024] Top hat fuel supply system 5-T is a portion of the piping after inlet piping 51 branches, and includes a portion of the piping that connects to flow control valve 52T, flow control valve 52T, and outlet piping 53T. Pilot fuel supply system 5-P is a portion of the piping after inlet piping 51 branches, and includes a portion of the piping that connects to flow control valve 52P, flow control valve 52P, and outlet piping 53P. Main fuel supply system 5-M is a portion of the piping after inlet piping 51 branches, and includes a portion of the piping that connects to flow control valve 52M, flow control valve 52M, and outlet piping 53M.

[0025] 1 shows the main components of the natural gas fuel supply line 3, the hydrogen gas fuel supply line 4, and the mixed gas fuel supply line 5. In practice, a heater may be inserted between the natural gas flow meter 33 of the natural gas fuel supply line 3 and the fuel supply line connection part 10, and shut-off valves or the like may be inserted at various locations in the natural gas fuel supply line 3, the hydrogen gas fuel supply line 4, and the mixed gas fuel supply line 5.

[0026] The gas turbine 2 includes an air compressor 21, a combustor 22, a turbine 23, a rotor 24, and a generator 25. The air compressor 21 draws in and compresses air through the rotation of the rotor 24, which passes through the air compressor 21, the combustor 22, and the turbine 23, and supplies the compressed air to the combustor 22. The combustor 22 includes three fuel injectors: a top hat fuel injector, a pilot fuel injector, and a main fuel injector. The top hat fuel injector receives mixed gas from outlet piping 53T of a top hat fuel supply system 5-T. The pilot fuel injector receives mixed gas from outlet piping 53P of a pilot fuel supply system 5-P. The main fuel injector receives mixed gas from outlet piping 53M of a main fuel supply system 5-M.

[0027] In the combustor 22, the top hat fuel injector, pilot fuel injector, and main fuel injector inject mixed gas into air supplied from the air compressor 21, and the mixed gas is burned. Combustion gas generated by the combustion of the mixed gas flows into the turbine 23, causing the rotor 24 to rotate, and the rotation of the rotor 24 generates electricity in the generator 25.

[0028] The thermometer 12 measures, for example, at regular intervals, the temperature of the mixed gas passing through the inlet pipe 51 before it branches into three ways, and outputs the measured temperature value of the mixed gas to the fuel control device 6. The pressure gauge 13 measures, for example, at regular intervals, the pressure of the mixed gas passing through the inlet pipe 51 before it branches into three ways, and outputs the measured pressure value of the mixed gas to the fuel control device 6. The wattmeter 11 measures, for example, at regular intervals, the power generated by the generator 25, and outputs the measured power value to the CSO signal output device 14 and the fuel control device 6. Here, the unit of the power value measured by the wattmeter 11 is, for example, [MW (Mega Watt)].

[0029] For example, every time the CSO signal output device 14 receives a power value output by the power meter 11, the CSO signal output device 14 calculates a fuel flow rate command value that brings the amount of power generated by the generator 25 closer to the target power value, based on the difference between the received power value and an externally provided target power value. The CSO signal output device 14 generates a CSO signal that represents the calculated fuel flow rate command value, and outputs the generated CSO signal to the fuel control device 6.

[0030] (Configuration of fuel control device) The fuel control device 6 can be configured using, for example, a computer such as a server, personal computer, or microcomputer, and peripheral devices of the computer, and is functionally configured by a combination of hardware such as the computer and software such as a program executed by the computer, including a mixed gas flow rate control valve control unit 61, a memory unit 71, an adder 72, a rate limiting unit 73, a hydrogen mixing ratio calculation unit 74, a hydrogen gas valve opening calculation unit 75, a power value memory unit 81, a determination unit 82, and a correction unit 83, as shown in Figure 2. The hydrogen gas valve opening calculation unit 75 includes a subtractor 76 and a PI (Proportional-Integral) control unit 77. The correction unit 83 includes a bias value setting unit 84 and a subtractor 85.

[0031] 3 in advance. The upper limit command value and the lower limit command value are the upper limit and lower limit values, respectively, of the command value calculated by the PI control unit 77 as a result of PI control. The bias start value is a value set by the bias value setting unit 84 when starting the bias. The bias decrease value is a value by which the bias value setting unit 84 decreases the bias value in one step. The mixed gas valve aperture calculation parameters are parameters including a plurality of constants such as the density of natural gas, and are referenced by the mixed gas flow rate control valve control unit 61 when calculating the valve apertures of the flow rate control valves 52T, 52P, 52M.

[0032] The mixed gas flow rate control valve control unit 61 calculates the valve aperture of each of the flow rate control valves 52T, 52P, 52M based on a fuel flow rate command value represented by the CSO signal output by the CSO signal output device, a fuel distribution ratio continuously supplied from the outside, mixed gas valve aperture calculation parameters stored in the memory unit 71, the mixed gas temperature value output by the thermometer 12, and the mixed gas pressure value output by the pressure gauge 13.

[0033] Here, the fuel distribution ratio is a ratio of the amount of fuel distributed to each of the top hat fuel supply system 5-T, pilot fuel supply system 5-P, and main fuel supply system 5-M, expressed as three values ​​in the unit of [%], with the sum of the three values ​​being 100 [%]. Hereinafter, the expression "each of the top hat fuel supply system 5-T, pilot fuel supply system 5-P, and main fuel supply system 5-M" will be abbreviated as "each of the fuel supply systems" or "each fuel supply system."

[0034] The fuel distribution ratio is a ratio that changes depending on the operating state of the gas turbine 2. For example, different fuel distribution ratios are selected by the operator of the gas turbine power plant 1 for ignition and for rated load operation, and are supplied to the mixed gas flow rate control valve control unit 61.

[0035] The adder 72 adds a target mixture ratio, which is a target value for the ratio of hydrogen gas contained in the mixed gas continuously supplied from outside, to a manual bias value, which is continuously supplied from outside, and outputs the sum obtained by the addition. The target mixture ratio is a value that is determined systematically by, for example, the operator of the gas turbine power plant 1, and is a value expressed in units of [%] as the volume ratio of hydrogen gas contained in the mixed gas per unit volume. The manual bias value is a value that is determined arbitrarily by, for example, the operator of the gas turbine power plant 1 depending on the daily operating conditions, and is a value expressed in units of [%].

[0036] When the sum output by the adder 72 increases suddenly due to a change in the target mixture ratio or manual bias value, the rate limiter 73 limits, for example, the rate of increase of the sum per unit time and outputs the limited value. The rate limiter 73 relaxes the limit over time. Therefore, if the sum output by the adder 72 remains constant after a sudden increase in the sum, the value output by the rate limiter 73 approaches the sum output by the adder 72 over time and eventually matches the sum. Hereinafter, the sum output by the rate limiter 73 is referred to as the control reference mixture ratio.

[0037] The determination unit 82 includes a timekeeping means such as a clock. Every time the determination unit 82 acquires a power value output by the power meter 11, the determination unit 82 acquires the time from the timekeeping means, and records the acquired power value in the power value storage unit 81 in association with the acquired time.

[0038] The determination unit 82 determines whether a predetermined decrease has occurred in the load of the gas turbine 2. This determination is made, for example, as follows: Every time the determination unit 82 acquires a power value, it reads out from the power value storage unit 81 the power value (hereinafter referred to as the previous power value) acquired a predetermined decrease determination time before the acquired power value (hereinafter referred to as the current power value), for example, 10 seconds before. However, if there is no power value before the decrease determination time, the power value at the time closest to the time before the decrease determination time is read out as the previous power value.

[0039] The determination unit 82 subtracts the previous power value from the current power value, and if the subtraction value obtained by the subtraction is a negative value and the absolute value of the subtraction value exceeds a predetermined power value decrease amount that is set in advance, it determines that a predetermined decrease has occurred in the load of the gas turbine 2.

[0040] The determination unit 82 determines whether the load change state of the gas turbine 2 can be considered to be steady. This determination is made, for example, as follows. Each time the determination unit 82 acquires a power value, it reads out from the power value storage unit 81 a power value (hereinafter referred to as a comparison power value) that is a predetermined number of steady-state determination times before the acquired power value (hereinafter referred to as a reference power value). Here, the predetermined number of steady-state determination times refers to a number of times before, for example, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, and 60 seconds. However, if a power value X seconds before does not exist, the power value at the time closest to the time X seconds before is read out as the comparison power value (here, X is any one of a number of time values ​​that are determined as a number of times before a steady-state determination time, such as 10, 20, 30, 40, 50, and 60 seconds).

[0041] The determination unit 82 calculates the absolute value of the difference between the reference power value and each of the plurality of comparison power values, and if all the absolute values ​​of the differences are within a predetermined range, determines that the state of the load change of the gas turbine 2 can be considered steady. Here, "within the predetermined range" ideally means within 0 MW, which indicates a completely steady state, but since there is some fluctuation in the power value output by the power meter 11, the range is determined taking this fluctuation into consideration.

[0042] In the correction unit 83, the bias value setting unit 84 outputs a bias value expressed in units of [%] for each control cycle. In the initial state after startup, the bias value setting unit 84 outputs a bias value whose value is "0" (hereinafter also referred to as "zero"). When the determination unit 82 determines that a predetermined decreasing change has occurred in the load of the gas turbine 2, the bias value setting unit 84 sets the bias start value stored in the memory unit 71 as the bias value and outputs the set bias value.

[0043] When the determination unit 82 determines that the load change state of the gas turbine 2 can be considered to be steady, the bias value setting unit 84 outputs a bias value as follows. That is, in each control cycle after the timing of the determination, the bias value setting unit 84 outputs a subtraction value obtained by subtracting the bias decrease value stored in the storage unit 71 from the bias value of the previous control cycle as a new bias value. However, when the subtraction value becomes a value less than "0," the bias value setting unit 84 outputs a bias value of zero.

[0044] The subtractor 85 subtracts the bias value output by the bias value setting unit 84 from the control reference mixture ratio output by the rate limiting unit 73, and sets the subtracted value obtained by the subtraction as the control reference mixture ratio corrected by the bias value (hereinafter referred to as the corrected control reference mixture ratio).

[0045] The hydrogen mixing ratio calculation unit 74 calculates a hydrogen mixing ratio (hereinafter referred to as the measured hydrogen mixing ratio) that indicates the ratio of hydrogen gas contained per unit volume from the volumetric flow rate of natural gas output by the natural gas flow meter 33 each time it is measured and the volumetric flow rate of hydrogen gas output by the hydrogen gas flow meter 42 each time it is measured. The measured hydrogen mixing ratio is expressed in units of [%].

[0046] In the hydrogen gas valve opening calculation unit 75, a subtractor 76 subtracts the actual measured hydrogen mixing ratio calculated by the hydrogen mixing ratio calculation unit 74 from the corrected control reference mixing ratio calculated by the subtractor 85, and the subtracted value obtained by the subtraction is used as the deviation for control.

[0047] When activated, the PI control unit 77 reads an upper limit command value and a lower limit command value from the storage unit 71. The PI control unit 77 records the valve opening degree most recently output to the hydrogen gas flow rate control valve 43 in an internal storage area. The PI control unit 77 calculates a command value that brings the control deviation closer to zero within the range between the upper limit command value and the lower limit command value, based on the control deviation calculated by the subtractor 76 and the valve opening degree stored in the internal storage area. The PI control unit 77 adds the calculated command value to the valve opening degree stored in the internal storage area to calculate a new valve opening degree of the hydrogen gas flow rate control valve 43. Note that if the command value is a positive value, the valve opening degree increases and the hydrogen gas flow rate control valve 43 opens, and if the command value is a negative value, the valve opening degree decreases and the hydrogen gas flow rate control valve 43 closes.

[0048] (Processing by fuel control device) The processing by the fuel control device 6 will be described with reference to Figures 4 to 7. Note that the processing by the mixed gas flow rate control valve control unit 61 shown below is performed in parallel with the processing of the flowcharts shown in Figures 4 to 6.

[0049] When the mixed gas flow rate control valve control unit 61 receives the CSO signal output by the CSO signal output device, it multiplies the fuel flow rate command value represented by the received CSO signal by each of the fuel allocation ratios continuously supplied from the outside. This multiplication results in three multiplication values ​​corresponding to the top hat fuel supply system 5-T, the pilot fuel supply system 5-P, and the main fuel supply system 5-M. A function for calculating the total mass flow rate of natural gas supplied to the gas turbine 2 from the fuel flow rate command value is predefined in the mixed gas flow rate control valve control unit 61. The mixed gas flow rate control valve control unit 61 substitutes each of the three calculated multiplication values ​​into the function to calculate the mass flow rate of natural gas for each fuel supply system.

[0050] The mixed gas flow rate control valve control unit 61 calculates the volumetric flow rate of the mixed gas supplied to the gas turbine 2 for each fuel supply system based on the calculated mass flow rate of natural gas for each fuel supply system and the mixed gas valve aperture calculation parameters stored in the memory unit 71. The mixed gas flow rate control valve control unit 61 calculates the volume of the mixed gas passing through each of the flow rate control valves 52T, 52P, and 52M based on the calculated volumetric flow rate of the mixed gas for each fuel supply system, the mixed gas valve aperture calculation parameters stored in the memory unit 71, the mixed gas temperature value output by the thermometer 12, and the mixed gas pressure value output by the pressure gauge 13. A function for calculating the valve aperture from the volume of the mixed gas passing through the valve is predefined in the mixed gas flow rate control valve control unit 61. The mixed gas flow rate control valve control unit 61 calculates the valve aperture corresponding to each of the flow rate control valves 52T, 52P, and 52M by substituting each of the mixed gas volumes passing through the valve into the function. The mixed gas flow rate adjustment valve control unit 61 outputs each of the calculated valve opening degrees to the corresponding flow rate adjustment valves 52T, 52P, 52M.

[0051] As described above, each time the CSO signal output device 14 receives a power value output by the power meter 11, it calculates a fuel flow rate command value that brings the amount of power generated by the generator 25 closer to the target power value based on the difference between the received power value and an externally provided target power value, and outputs the CSO signal. Each time the mixed gas flow rate control valve control unit 61 receives a CSO signal, it calculates the valve opening degree of each of the flow rate control valves 52T, 52P, and 52M based on the fuel flow rate command value represented by the received CSO signal. Therefore, the mixed gas is supplied to the gas turbine 2 at a flow rate adjusted by the flow rate control valves 52T, 52P, and 52M so as to bring the amount of power generated by the generator 25 closer to the target power value.

[0052] FIG. 4 is a flowchart showing the processing flow by the determination unit 82. FIG. 5 is a flowchart showing the processing flow by the bias value setting unit 84. The processing shown in FIGS. 4 and 5 will be described with reference to the graphs shown in FIG. 7. The graph in FIG. 7(a) is a graph showing the change over time in the hydrogen mixing ratio. The graph in FIG. 7(b) is a graph showing the change over time in the bias value output by the bias value setting unit 84. The graph in FIG. 7(c) is a graph showing the change over time in the power value output by the wattmeter 11. The vertical axes in FIGS. 7(a) and 7(b) are in [%], and the vertical axis in FIG. 7(c) is in [MW]. The horizontal axes in FIGS. 7(a), 7(b), and 7(c) are time, expressed on the same scale.

[0053] (Processing between time t0 and time t2) 4 is performed by the determination unit 82 each time the determination unit 82 acquires a power value output by the power meter 11. When the determination unit 82 acquires a power value, the determination unit 82 acquires the time from a clock means provided inside the determination unit 82, associates the acquired time with the acquired power value, and records the associated time in the power value storage unit 81 (Sa1).

[0054] Between time t0 and time t1, the gas turbine 2 is operated with its output statically determined, and the power value is in a state where it can be considered to be constant with almost no change, as shown by the polygonal line 110 in Fig. 7(c) (hereinafter referred to as polygonal line 110). At time t1, for example, when control to reduce the load, such as load varying operation or runback, is started, for example, control to reduce the target value of power to be given to the CSO signal output device 14, the power value output by the power meter 11 begins to decrease.

[0055] The determination unit 82 determines whether a predetermined decrease in the load of the gas turbine 2 has occurred, using the procedure described above, based on the acquired power value and the time associated with the power value (Sa2). Here, it is assumed that the time from time t1 to time t2 matches the decrease determination time set by the determination unit 82. Furthermore, it is assumed that, for the first time at time t2, the difference between the power value at time t2 and the power value at time t1 corresponding to the time before the decrease determination time, i.e., the amount of change in the power value indicated by reference numeral 111 in FIG. 7(c), exceeds the predetermined amount of decrease in the power value set by the determination unit 82.

[0056] In this case, the judgment unit 82 judges that a predetermined decrease in the load of the gas turbine 2 has not occurred from time t0 to just before time t2 (Sa2, No), and then judges whether the state of the load change of the gas turbine 2 can be considered steady (Sa4).

[0057] Between time t0 and time t1, the state of the power value at the time corresponding to each of the plurality of steady-state determination times before the time t1 is considered to be constant. Therefore, the determination unit 82 determines that the state of the load change of the gas turbine 2 is considered to be steady (Sa4, Yes), outputs a bias stop instruction signal to the bias value setting unit 84 (Sa5), and ends the processing.

[0058] In contrast, in the period from time t1 to just before time t2, the power value decreases, and therefore, depending on how each of the times before the plurality of steady-state determination times is defined, the determination unit 82 may determine that the state of the load change of the gas turbine 2 is not a state that can be considered steady (Sa4, No). If the determination is "No" in the processing of Sa4, the determination unit 82 ends the processing.

[0059] At time t2, the determination unit 82 acquires the power value output by the power meter 11, performs processing Sa1 on the acquired power value, and then performs determination processing Sa2 based on the power value at time t2 and the power value at time t1, which is the decrease determination time before time t2. In the determination processing Sa2, the determination unit 82 determines that a predetermined decrease has occurred in the load of the gas turbine 2 (Sa2, Yes), outputs a bias start instruction signal to the bias value setting unit 84 (Sa3), and ends the processing.

[0060] 5, when the bias value setting unit 84 is started, it sets the bias value to zero (Sb1) and repeats the process from Sb2 onwards for each control period. The bias value setting unit 84 determines whether or not it has received a bias start instruction signal from the determination unit 82 (Sb2). Between time t0 and just before time t2, the bias value setting unit 84 does not receive a bias start instruction signal from the determination unit 82, and therefore determines that it has not received a bias start instruction signal from the determination unit 82 (No in Sb2).

[0061] If the determination in step Sb2 is "No," the bias value setting unit 84 determines whether or not it has received a bias stop instruction signal from the determination unit 82 (Sb4). As described above, from time t0 to time t1, the bias value setting unit 84 receives a bias stop instruction signal from the determination unit 82 in each control cycle. From time t1 to just before time t2, the bias value setting unit 84 may or may not receive a bias stop instruction signal from the determination unit 82 in each control cycle.

[0062] Therefore, when bias value setting unit 84 receives a bias stop instruction signal from determination unit 82, it determines that it has received the bias stop instruction signal (Sb4, Yes), and determines whether the bias value at the time of determination is zero (Sb5). Because the bias value is zero from time t0 to immediately before time t2, bias value setting unit 84 determines that the bias value is zero (Sb5, Yes), and outputs the zero bias value to subtractor 85 (Sb9).

[0063] On the other hand, if the bias stop instruction signal has not been received from the determination unit 82, the bias value setting unit 84 determines that the bias stop instruction signal has not been received (Sb4, No). Since the bias value is zero from time t0 until immediately before time t2, the bias value setting unit 84 outputs a bias value of zero to the subtractor 85 (Sb9). After performing the process of Sb9, the bias value setting unit 84 performs the process of Sb2 in the next control cycle.

[0064] At time t2, bias value setting unit 84 receives a bias start instruction signal from determination unit 82, and therefore determines in the determination process of Sb2 that it has received a bias start instruction signal from determination unit 82 (Sb2, Yes). In this case, bias value setting unit 84 reads out the bias start value from storage unit 71, sets the read bias start value as the bias value (Sb3), and outputs the bias value to subtractor 85 (Sb9). As a result, at time t2, the bias value output by bias value setting unit 84 increases from zero to the bias start value, as shown by the broken line indicated by reference numeral 100 in FIG. 7(b) (hereinafter referred to as broken line 100).

[0065] (Processing between time t2 and time t3) Between time t2 and time t3, the power value decreases at a constant rate, as shown by the polygonal line 110 in Fig. 7(c) . Therefore, every time the determination unit 82 acquires a power value, it determines in the determination process Sa2 that a predetermined decrease has occurred in the load of the gas turbine 2 (Sa2, Yes), and outputs a bias start instruction signal to the bias value setting unit 84 in the process Sa3.

[0066] The bias value setting unit 84 determines that it has received a bias stop instruction signal from the judgment unit 82 in the judgment process of Sb2 for each control period (Sb2, Yes), and after processing of Sb3, outputs the bias value for which the bias start value is set to the subtractor 85 for each control period (Sb9).

[0067] (Processing between time t3 and time t5) As shown by the broken line 110 in Figure 7(c), when load-varying operation, runback, or other load-reducing control is completed, the power value changes from a decreasing state to a state that can be considered constant at time t3. Here, if time t4 is used as the reference, then time t3 is the time before the longest of the multiple steady-state determination times determined by the determination unit 82. Furthermore, if the power value at time t4 is used as the reference power value, then in the process from time t3 to time 4, it is only at time t4 that all of the absolute values ​​of the differences between the reference power value and the multiple comparison power values ​​become values ​​within the predetermined range determined by the determination unit 82.

[0068] In this case, from time t3 onwards, each time the determination unit 82 acquires a power value, the determination unit 82 determines in the determination process Sa2 of Fig. 4 that a predetermined decrease has not occurred in the load of the gas turbine 2 (Sa2, No). In the subsequent determination process Sa4, the determination unit 82 determines that the state of the load change of the gas turbine 2 from time t3 to just before time t4 is not a state that can be regarded as steady (Sa4, No), and ends the process. From time t4 onwards, in the determination process Sa4, the determination unit 82 determines that the state of the load change of the gas turbine 2 is a state that can be regarded as steady (Sa4, Yes), outputs a bias stop instruction signal to the bias value setting unit 84 (Sa5), and ends the process.

[0069] From time t3 to immediately before time t4, as described above, the determination unit 82 does not output a bias start instruction signal or a bias stop instruction signal. Therefore, the bias value setting unit 84 makes a determination of "No" in the determination process of Sb2 and the determination process of Sb4 in Fig. 5, and outputs the bias value that was output in the control cycle immediately before time t3, i.e., the bias value of the bias start value, to the subtractor 85 (Sb9).

[0070] At time t4, bias value setting unit 84 receives a bias stop instruction signal from determination unit 82, and so makes a "Yes" determination in the determination process of Sb4. Here, the bias value is the bias start value, so in the determination process of Sb5, bias value setting unit 84 determines that the bias value is not zero (Sb5, No). In this case, bias value setting unit 84 reads the bias decrease value from storage unit 71, and sets the subtraction value obtained by subtracting the read bias decrease value from the bias value as a new bias value (Sb6).

[0071] The bias value setting unit 84 determines whether the new bias value is less than zero (Sb7). If the bias value setting unit 84 determines that the new bias value is not less than zero (Sb7, No), it outputs the new bias value to the subtractor 85 (Sb9).

[0072] In the next control cycle, the bias value output in the previous control cycle is equal to "bias start value - bias decrease value." Therefore, based on the bias value in the previous control cycle, the bias value setting unit 84 calculates a new bias value as "bias value in the previous control cycle - bias decrease value," i.e., "bias start value - 2 × bias decrease value," through the process of Sb6. The process of subtracting the bias decrease value from the bias value in the previous control cycle is repeated for each control cycle. In other words, the process of calculating "bias start value - N × bias decrease value" (where N is the number of times the process of Sb6 is repeated) is repeated. As a result, the new bias value calculated by the bias value setting unit 84 in the process of Sb6 in any control cycle becomes a value less than "0."

[0073] In this case, the bias value setting unit 84 determines that the new bias value is less than zero (Sb7, Yes), sets the bias value to zero (Sb8), and outputs the bias value set to zero to the subtractor 85 (Sb9).

[0074] As a result, as shown by the broken line 100 in Figure 7(b), from time t4 onwards, the bias value decreases by the bias decrease value for each control cycle, and at time t5 the bias value becomes zero, after which the bias value is maintained at zero.

[0075] 6 is a flowchart showing the processing flow by the adder 72, the rate limiting unit 73, the subtractor 85, and the hydrogen gas valve opening calculation unit 75. In parallel with the processing shown in FIG. 6, the processing shown in FIG. 4 and FIG. 5 and the processing by the hydrogen mixing ratio calculation unit 74 shown below are performed.

[0076] The hydrogen mixing ratio calculation unit 74 receives the volumetric flow rate of natural gas output each time the natural gas flow meter 33 takes a measurement, and the volumetric flow rate of hydrogen gas output each time the hydrogen gas flow meter 42 takes a measurement. Each time the hydrogen mixing ratio calculation unit 74 receives the volumetric flow rates of natural gas and hydrogen gas, it calculates a hydrogen mixing ratio that indicates the ratio of hydrogen gas contained per unit volume from the received volumetric flow rates of natural gas and hydrogen gas, and outputs the calculated hydrogen mixing ratio to a subtractor 76 as the actually measured hydrogen mixing ratio.

[0077] 6 is performed each time the adder 72 receives a target mixture ratio, which is a target value for the ratio of hydrogen gas contained in a mixture gas continuously supplied from the outside, and a manual bias value, which is continuously supplied from the outside. The adder 72 adds the received target mixture ratio and manual bias value, and outputs the sum obtained by the addition (Sc1).

[0078] As described above, when the sum output by the adder 72 increases rapidly, the rate limiter 73 outputs the limited value as the control reference mixture ratio. Here, it is assumed that the sum output by the adder 72 is maintained at a constant value after time t0. Therefore, the rate limiter 73 does not impose any limit, and simply outputs the sum output by the adder 72 as the control reference mixture ratio (Sc2).

[0079] The subtractor 85 takes in the control reference mixture ratio output by the rate limiting unit 73 and the bias value output by the bias value setting unit 84, subtracts the bias value from the control reference mixture ratio, and outputs the subtracted value obtained by the subtraction as the corrected control reference mixture ratio (Sc3).

[0080] The subtractor 76 receives the corrected control reference mixture ratio output by the subtractor 85 and the measured hydrogen mixture ratio output by the hydrogen mixture ratio calculation unit 74. The subtractor 76 subtracts the measured hydrogen mixture ratio from the corrected control reference mixture ratio and outputs the resulting difference as a control deviation (Sc4). The PI control unit 77 receives the control deviation output by the subtractor 76. Based on the control deviation and the most recent valve opening output to the hydrogen gas flow rate control valve 43 stored in an internal memory area, the PI control unit 77 calculates a command value that brings the control deviation closer to zero within the range between an upper command value and a lower command value. The PI control unit 77 calculates the valve opening by adding the calculated command value to the valve opening stored in an internal memory area. The PI control unit 77 outputs the calculated valve opening to the hydrogen gas flow rate adjustment valve 43, rewrites the valve opening stored in the internal storage area with the calculated valve opening (Sc5), and ends the process.

[0081] (Effects of the embodiment) In the following description, "same" not only means completely same, but also generally means that the two would be the same if the effects of numerical fluctuations and the like that occur during the control process were eliminated, i.e., they would be almost the same.

[0082] 7(a), the solid polygonal line 90 (hereinafter referred to as polygonal line 90) shows the change over time in the corrected control reference mixture ratio output by the subtractor 85. The dashed-dotted polygonal line 91 (hereinafter referred to as polygonal line 91) shows the change over time in the hydrogen mixture ratio of the mixed gas supplied to the combustor 22. The dotted line 92 shows the hydrogen mixture ratio threshold (hereinafter referred to as threshold 92) at which interlock is initiated. Note that from time t0 to time t1 and from time t3-1 onwards, the change in the polygonal line 91 is the same as the change in the polygonal line 90.

[0083] When the gas turbine 2 is operated with its output statically stabilized from time t0 to time t1, the corrected control reference mixture ratio output by the subtractor 85, the measured hydrogen mixture ratio output by the hydrogen mixture ratio calculation unit 74, and the hydrogen mixture ratio of the mixed gas supplied to the combustor 22 are all the same.

[0084] At time t1, when control to reduce the load, such as load change operation or runback, is initiated, the mixed gas flow rate control valve control unit 61 changes the valve apertures of the flow rate control valves 52T, 52P, and 52M, and the flow rate of the mixed gas supplied to the combustor 22 begins to decrease. As a result, the output of the gas turbine 2 begins to decrease, and the power value measured by the wattmeter 11 also begins to decrease, as shown by the polygonal line 110 in FIG. 7( c). At time t1, the flow rate of the mixed gas begins to decrease, but the valve aperture of the hydrogen gas flow rate control valve 43 is not changed, and the flow rate of the hydrogen gas is maintained. Therefore, after time t1, the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 increases, as shown by the polygonal line 91 in FIG. 7( a).

[0085] At time t2, the bias value setting unit 84 starts outputting the bias value set by the bias start value, as shown by the polygonal line 100 in Fig. 7(b). Therefore, at time t2, the corrected control reference mixture ratio output by the subtractor 85 suddenly decreases by the amount of the bias start value, as shown by the polygonal line 90 in Fig. 7(a).

[0086] In contrast, the measured hydrogen mixing ratio output by the hydrogen mixing ratio calculation unit 74 is calculated from the volumetric flow rate of natural gas output by the natural gas flow meter 33 and the volumetric flow rate of hydrogen gas output by the hydrogen gas flow meter 42. When the valve apertures of the flow control valves 52T, 52P, and 52M are changed and the flow rate of the mixed gas supplied to the combustor 22 begins to decrease, the volumetric flow rate of natural gas measured by the natural gas flow meter 33 also begins to decrease. In contrast, at time t2, the valve aperture of the hydrogen gas flow control valve 43 has not been changed since before time t2, so the measured hydrogen mixing ratio output by the hydrogen mixing ratio calculation unit 74 increases. Because the corrected control reference mixing ratio rapidly decreases while the measured hydrogen mixing ratio increases, the control deviation calculated by the subtractor 76 rapidly increases in the negative direction.

[0087] However, because the PI control unit 77 cannot calculate a command value smaller than the lower limit command value, the valve opening of the hydrogen gas flow rate control valve 43 does not suddenly decrease. Therefore, the flow rate of hydrogen gas supplied from the hydrogen gas fuel supply line 4 to the fuel supply line connection unit 10 decreases little by little. On the other hand, because the flow rate of the mixed gas supplied to the combustor 22 continues to decrease, the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 continues to increase.

[0088] The bias start value is determined in advance so that, when the determination unit 82 first determines at time t2 that a predetermined decrease has occurred in the load of the gas turbine 2, the increase in the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 turns to a decrease due to a decrease in the hydrogen mixing ratio caused by a decrease in the hydrogen gas flow rate due to adjustment of the hydrogen gas flow rate control valve 43 performed using the bias start value. Therefore, as shown by the line 91 in FIG. 7( a) , at time t2, the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 begins to decrease little by little. Note that, due to the length of the piping from the hydrogen gas flow rate control valve 43 to the combustor 22, the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 actually begins to decrease slightly after time t2.

[0089] As the valve aperture of the hydrogen gas flow rate control valve 43 continues to decrease between time t2 and time t2-1, the difference between the measured hydrogen mixing ratio calculated by the hydrogen mixing ratio calculation unit 74 and the corrected control reference mixing ratio output by the subtractor 85 decreases. As this difference decreases, the control deviation also decreases, and the command value calculated by the PI control unit 77 no longer fluctuates significantly. Therefore, the rate at which the valve aperture of the hydrogen gas flow rate control valve 43 decreases also decreases. During this time, the flow rate of the mixed gas supplied to the combustor 22 continues to decrease, so the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 continues to increase.

[0090] For example, assume that at time t2-1, the increase in the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 exceeds the decrease in the hydrogen mixing ratio caused by the decrease in the flow rate of hydrogen gas supplied from the hydrogen gas fuel supply line 4 to the fuel supply line connection portion 10. In this case, as shown by the polygonal line 91 in Figure 7(a), at time t2-1, the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 begins to increase again.

[0091] At time t3, when load-reducing control such as load change operation or runback ends, the decrease in the flow rate of the mixed gas supplied to the combustor 22 stops, and therefore the increase in the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 also stops. Therefore, after time t3, the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 changes in accordance with the change in the valve aperture of the hydrogen gas flow rate control valve 43 output by the PI control unit 77. Therefore, as shown by the polygonal line 91 in FIG. 7(a), at time t3-1, which is a time slightly after time t3, the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 becomes equal to the corrected control reference mixing ratio shown by the polygonal line 90.

[0092] After time t4, as shown by the polygonal line 100 in Fig. 7(b), the bias value setting unit 84 decreases the bias value by the bias decrement value for each control cycle. Therefore, as shown by the polygonal line 90 in Fig. 7(a), the corrected control standard mixture ratio output by the subtractor 85 increases little by little, and the hydrogen mixture ratio of the mixed gas supplied to the combustor 22 also increases little by little, thereby enabling a gradual change in the combustion state in the combustor 22. At time t5, the hydrogen mixture ratio of the mixed gas supplied to the combustor 22 returns to the hydrogen mixture ratio of the mixed gas supplied to the combustor 22 before time t1, allowing a mixed gas with a desired hydrogen mixture ratio to be supplied to the gas turbine 2.

[0093] As described above, at time t2, the bias value setting unit 84 outputs the bias value of the bias start value, thereby preventing the hydrogen mixture ratio of the mixed gas supplied to the combustor 22 from reaching the threshold value 92. This prevents the interlock of the gas turbine 2 from operating, which would stop the gas turbine 2, and prevents the mixed gas with a hydrogen mixture ratio that would cause flashback from being supplied to the combustor 22.

[0094] In the technology disclosed in Patent Document 1, two flow control valves, one for natural gas and one for hydrogen gas, are provided for each fuel injector, and the mixing ratio of natural gas and hydrogen gas is controlled for each fuel injector. In contrast, in the gas turbine power plant 1 according to this embodiment, only one hydrogen gas flow control valve 43 is used to adjust the flow rate of hydrogen gas, and the valve opening of this single hydrogen gas flow control valve 43 is adjusted by a hydrogen gas valve opening calculation unit 75. Furthermore, when the determination unit 82 determines, based on the power value output by the wattmeter 11, that a predetermined decrease in the load of the gas turbine 2 has occurred, the bias value setting unit 84 simply outputs a bias value equal to the bias start value to increase the bias. Therefore, the fuel control device 6 according to this embodiment can prevent flashback from occurring even when the load decreases, with simpler control than that disclosed in Patent Document 1.

[0095] (Regarding bias start value) At time t2, the bias value setting unit 84 outputs the bias start value as the bias value, and the subtractor 85 subtracts the bias value from the control reference mixture ratio. This can be said to be feedforward control that compensates for the delay until the hydrogen mixture ratio calculation unit 74 outputs the actual hydrogen mixture ratio, i.e., the hydrogen mixture ratio of the mixed gas supplied to the combustor 22. Therefore, the effect of feedforward control changes depending on the bias start value.

[0096] The bias start value needs to be determined in consideration of, for example, the rate of increase when the hydrogen mixture ratio of the mixed gas supplied to the combustor 22 increases after time t1, as shown by the polygonal line 91 in FIG. 7(a), and the length of time from time t1 to time t3 during which the flow rate of the mixed gas supplied to the combustor 22 decreases.

[0097] The above has described a condition (hereinafter referred to as the first condition) for the bias start value, which is such that when the judgment unit 82 first judges that a predetermined decrease has occurred in the load of the gas turbine 2, the bias start value is set so that the increase in the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 turns into a decrease due to a decrease in the hydrogen mixing ratio caused by a decrease in the flow rate of hydrogen gas due to adjustment of the hydrogen gas flow control valve 43 performed by applying the bias start value.

[0098] Ideally, the bias start value should be set to satisfy the first condition and be large enough so that the polygonal line 91 continues to decrease between time t2 and time t3 without increasing again. However, depending on the magnitude of the bias start value, it is possible that the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 may increase again, as shown in the polygonal line 91 in FIG. 7(a) between time t2-1 and time t3. In this case, to prevent the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 from reaching the threshold value 92 before time t3, the following condition needs to be added as a condition for determining the bias start value.

[0099] If it is possible to cancel out the total amount of the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 between time t2 and time t3 that is equal to or greater than the threshold 92 when the hydrogen mixing ratio becomes equal to or greater than the threshold 92, it is possible to prevent the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 from reaching the threshold 92. Here, the total amount of the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 that is equal to or greater than the threshold 92 when the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 between time t2 and time t3 becomes equal to or greater than the threshold 92 is the amount corresponding to the area of ​​the portion indicated by reference numeral 93 in FIG. 7(a).

[0100] Therefore, a condition for determining the bias start value (hereinafter referred to as the second condition) is that the total amount of decrease in the hydrogen mixing ratio caused by the decrease in the flow rate of hydrogen gas supplied from the hydrogen gas fuel supply line 4 to the fuel supply line connection part 10 between time t2 and time t3 must be equal to or greater than the amount corresponding to the area indicated by reference numeral 93. If a bias start value that satisfies the second condition is determined, it is possible to prevent the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 from reaching the threshold value 92 by time t3, even if the hydrogen mixing ratio increases again.

[0101] The threshold value 92 is a threshold value used to determine whether or not to activate the interlock. If flashback occurs at a level lower than the threshold value 92, a threshold value at which flashback occurs (hereinafter referred to as the flashback threshold value) can be set separately. In this case, flashback can be prevented by setting a bias start value that satisfies the second condition, which is set by replacing the threshold value 92 with the flashback threshold value. Alternatively, a bias start value may be set that does not satisfy the first condition but satisfies the second condition, which is set by replacing the threshold value 92 with the flashback threshold value, and that prevents the increase in the hydrogen mixing ratio of the mixed gas supplied to the combustor 22 from time t2 to time t3 from reaching the flashback threshold value.

[0102] (Supplementary configuration example of the embodiment) The embodiments of the present disclosure have been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and includes designs within the scope that do not deviate from the gist of the present disclosure.

[0103] In the above-described embodiment, when determining whether the load change state of the gas turbine 2 can be considered steady, the determination unit 82 calculates the absolute value of the difference between the reference power value and each of the plurality of comparison power values, and determines that the load change state of the gas turbine 2 can be considered steady if all the absolute values ​​of the differences are within a predetermined range. In contrast, the determination unit 82 sets the acquired power value as a current power value each time it acquires a power value, and reads out a previous power value corresponding to this current power value from the power value storage unit 81, just as when determining whether a predetermined decreasing change has occurred in the load. The determination unit 82 may also be configured to subtract the previous power value from the current power value, and determine that the load change state of the gas turbine 2 can be considered steady if the absolute value of the subtracted value obtained by the subtraction continues to be within a predetermined range for a predetermined time, for example, about 60 seconds.

[0104] In the above embodiment, the determination unit 82 obtains the time from the internal clock means each time it obtains a power value output by the power meter 11, and associates the obtained time with the obtained power value and records them in the power value storage unit 81. In contrast to this, the power meter 11 may be provided with an internal clock means, and upon measuring a power value, obtain the time from the clock means, associate the measured power value with the obtained time and output them to the determination unit 82. In this case, when the determination unit 82 obtains a combination of the power value and time output by the power meter 11, it records the combination of the obtained power value and time in the power value storage unit 81.

[0105] In the above embodiment, the determination unit 82 determines whether the absolute value of the subtraction value exceeds a predetermined predetermined amount of power value decrease when determining whether a predetermined decrease in load has occurred in the gas turbine 2. However, depending on how the predetermined amount of power value decrease is defined, the determination unit 82 may replace the determination of whether it exceeds the predetermined amount with a determination of whether it is equal to or greater than the predetermined amount of power value decrease, and may determine that a predetermined decrease in load on the gas turbine 2 has occurred when the absolute value of the subtraction value is equal to or greater than the predetermined amount of power value decrease.

[0106] In the above embodiment, instead of storing the upper limit command value and the lower limit command value in the storage unit 71, a signal generator may be provided that outputs an upper limit command value to the PI control unit 77 in the control cycle of the PI control unit 77, and a signal generator that outputs a lower limit command value to the PI control unit 77 in the control cycle of the PI control unit 77. In this case, instead of reading out the upper limit command value and the lower limit command value from the storage unit 71, the PI control unit 77 takes in the upper limit command value and the lower limit command value received from the signal generator.

[0107] In the above embodiment, the mixed gas fuel supply line 5 is shown to include three fuel supply systems to the gas turbine 2: a top hat fuel supply system 5-T, a pilot fuel supply system 5-P, and a main fuel supply system 5-M. However, there may be a plurality of top hat fuel supply systems 5-T, a plurality of pilot fuel supply systems 5-P, or a plurality of main fuel supply systems 5-M. In this case, the fuel distribution ratio indicates the ratio of fuel distribution to each of the plurality of top hat fuel supply systems 5-T, each of the plurality of pilot fuel supply systems 5-P, and each of the plurality of main fuel supply systems 5-M.

[0108] In the above embodiment, a mixed gas obtained by mixing hydrogen gas with natural gas is supplied to the gas turbine 2. Here, the combination of natural gas and hydrogen gas is just one example, and other combinations of fuel gases may be used. When this combination is expressed as a first fuel gas and a second fuel gas, the combination of the first fuel gas and the second fuel gas may be any combination as long as the difference is that the second fuel gas is a gas with a higher combustion velocity than the first fuel gas, like the difference between natural gas and hydrogen gas.

[0109] (Computer Configuration) FIG. 8 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. The computer 200 includes a processor 201, a main memory 202, a storage 203, and an interface 204. The fuel control device 6 described above is implemented in the computer 200. The operations of the above-described processing units, namely the mixed gas flow rate control valve control unit 61, the adder 72, the rate limiting unit 73, the hydrogen mixing ratio calculation unit 74, the hydrogen gas valve opening calculation unit 75, the determination unit 82, and the correction unit 83, are stored in the storage 203 in the form of a program. The processor 201 reads the program from the storage 203, loads it into the main memory 202, and executes the above-described processing in accordance with the program. The processor 201 also allocates storage areas in the main memory 202 or the storage 203 corresponding to the above-described storage unit 71 and power value storage unit 81 in accordance with the program. In accordance with the program, the processor 201 connects the mixed gas flow rate control valve control unit 61 to the CSO signal output device 14, the thermometer 12, the pressure gauge 13, and the flow rate control valves 52T, 52P, and 52M via the interface 204, connects the hydrogen mixing ratio calculation unit 74 to the natural gas flow meter 33 and the hydrogen gas flow meter 42 via the interface 204, connects the PI control unit 77 to the hydrogen gas flow rate control valve 43 via the interface 204, and connects the judgment unit 82 to the power meter 11 via the interface 204.

[0110] The program may be for realizing some of the functions to be performed by the computer 200. For example, the program may be combined with other programs already stored in the storage 203 or other programs implemented in other devices to perform the functions. In other embodiments, the computer may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions realized by the processor may be realized by the integrated circuit.

[0111] Examples of storage 203 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a compact disc read-only memory (CD-ROM), a digital versatile disc read-only memory (DVD-ROM), and a semiconductor memory. Storage 203 may be an internal medium directly connected to the bus of computer 200, or an external medium connected to computer 200 via interface 204 or a communication line. Furthermore, when this program is distributed to computer 200 via a communication line, computer 200 that receives the program may load the program into main memory 202 and execute the above-described processing. In at least one embodiment, storage 203 is a non-transitory tangible storage medium.

[0112] <Additional Notes> The fuel control device 6 according to the embodiment of the present disclosure can be understood, for example, as follows.

[0113] (1) A fuel control device 6 according to a first aspect includes: a determination unit 82 that determines whether a predetermined decrease in load of a gas turbine 2 to which a mixed gas obtained by mixing a first fuel gas and a second fuel gas having a faster combustion rate than the first fuel gas is being supplied; a correction unit 83 that, when the determination unit determines that the predetermined decrease in load has occurred, sets a bias value to a predetermined bias start value and performs correction to a control reference mixing ratio, which indicates the proportion of the second fuel gas in the mixed gas and whose difference from an actually measured mixing ratio is used as a deviation for control, by decreasing the bias value; and a valve aperture calculation unit (e.g., a hydrogen gas valve aperture calculation unit 75) that calculates a valve aperture of a second fuel gas flow rate control valve that adjusts the flow rate of the second fuel gas, based on the actually measured mixing ratio and the corrected control reference mixing ratio. According to this aspect and the following aspects, flashback can be prevented from occurring even when the load is reduced through simple control.

[0114] (2) A fuel control device 6 according to a second aspect is the fuel control device of (1), wherein the bias start value is set so that, when the determination unit first determines that the predetermined decreasing change is occurring, an increase in the mixing ratio of the mixed gas supplied to the gas turbine turns to a decrease due to a decrease in the mixing ratio caused by a decrease in the flow rate of the second fuel gas by adjustment of the second fuel gas flow rate control valve performed with the bias start value applied. According to this aspect, when the occurrence of a predetermined decreasing change in the gas turbine 2 is first detected, the mixing ratio of the mixed gas supplied to the gas turbine 2 can be reduced, thereby more reliably preventing flashback.

[0115] (3) A fuel control device 6 according to a third aspect is the fuel control device of (1) or (2), wherein the determination unit determines whether the state of load change of the gas turbine is a state that can be considered steady, and the correction unit decreases the bias value over time until the bias value becomes zero when the determination unit determines that the state of load change of the gas turbine is a state that can be considered steady. According to this aspect, the combustion state of the gas turbine 2 can be gradually changed, and the mixture ratio of the mixed gas can be returned to a desired mixture ratio. [Explanation of symbols]

[0116] 1. Gas turbine power plant 2...Gas turbine 3...Natural gas fuel supply line 4...Hydrogen gas fuel supply line 5...Mixed gas fuel supply line 5-T…Top Hat fuel supply system 5-P...Pilot fuel supply system 5-M...Main fuel supply system 6...Fuel control device 10...Fuel supply line connection 11...Power meter 12...Thermometer 13...Pressure gauge 14...CSO signal output device 21...Air compressor 22...Combustor 23...Turbine 24...Rotor 25...Generator 31...Natural gas supply source 32...Compressor 33...Natural gas flow meter 41...Hydrogen gas supply source 42...Hydrogen gas flow meter 43...Hydrogen gas flow control valve 51...Inlet piping 52T, 52P, 52M...Flow control valve 53T,53P,53M…Outlet piping 61... Mixed gas flow rate control valve control section 71...Storage section 72...Adder 73...Rate limiter 74...Hydrogen mixture ratio calculation section 75...Hydrogen gas valve opening calculation unit 76...Subtractor 77...PI control unit 81...Power value storage unit 82…Judgment section 83...Correction unit 84...Bias value setting section 85...Subtractor

Claims

1. a determination unit that determines whether a predetermined decrease occurs in the load of a gas turbine to which a mixed gas obtained by mixing a first fuel gas and a second fuel gas having a combustion speed faster than that of the first fuel gas is supplied; and a correcting unit that, when the determining unit determines that the predetermined decreasing change has occurred, sets a bias value to a predetermined bias start value and performs correction to reduce the bias value with respect to a control reference mixing ratio, which is a mixing ratio indicating the proportion of the second fuel gas in the mixed gas, and whose difference from an actually measured mixing ratio is used as a deviation for control; a valve aperture calculation unit that calculates an aperture of a second fuel gas flow rate control valve that adjusts a flow rate of the second fuel gas, based on the actually measured mixing ratio and the corrected control reference mixing ratio; A fuel control device comprising:

2. The bias start value is when the determination unit first determines that the predetermined decreasing change is occurring, an increase in the mixing ratio of the mixed gas supplied to the gas turbine turns into a decrease due to a decrease in the mixing ratio caused by a decrease in the flow rate of the second fuel gas due to adjustment of the second fuel gas flow rate control valve performed by applying the bias start value. The fuel control system of claim 1.

3. The determination unit determining whether a load change state of the gas turbine is a state that can be considered steady; The correction unit When the determination unit determines that the load change state of the gas turbine is considered to be steady, the bias value is decreased over time until the bias value becomes zero. The fuel control system of claim 1.

4. determining whether a predetermined decrease in load has occurred in a gas turbine to which a mixed gas obtained by mixing a first fuel gas and a second fuel gas having a combustion speed faster than that of the first fuel gas is supplied, and When it is determined that the predetermined decreasing change has occurred, a bias start value is set as a bias value, and a control reference mixture ratio indicating the ratio of the second fuel gas in the mixed gas, the difference of which from an actually measured mixture ratio, is used as a deviation for control, is corrected by decreasing the bias value; calculating a valve aperture of a second fuel gas flow rate control valve that adjusts a flow rate of the second fuel gas based on the actually measured mixture ratio and the corrected control reference mixture ratio; Fuel control method.

5. Computer, a determination means for determining whether or not a predetermined decrease in load of a gas turbine to which a mixed gas obtained by mixing a first fuel gas and a second fuel gas having a combustion speed faster than that of the first fuel gas is supplied; a correcting means for setting a predetermined bias start value as a bias value when the determining means determines that the predetermined decreasing change has occurred, and for correcting the bias value by decreasing a control reference mixing ratio, which is a mixing ratio indicating the proportion of the second fuel gas in the mixed gas, and whose difference from an actually measured mixing ratio is used as a deviation for control; a valve aperture calculation means for calculating an aperture of a second fuel gas flow rate control valve that adjusts the flow rate of the second fuel gas, based on the actually measured mixture ratio and the corrected control reference mixture ratio; A program to function as a

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