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

Abstract

To execute compensation control with respect to the fluctuation of system frequency with favorable responsiveness, while favorably maintaining the combustion state of a gas turbine, at the time of the fluctuation of the system frequency.SOLUTION: A gas turbine control device is for controlling a gas turbine having a turbine connected to a power generator electrically connected to a power system. The gas turbine control device adjusts the opening of a flow rate adjusting valve provided in a fuel supply system so that rotational frequency of the turbine becomes target rotational frequency corresponding to system frequency of the power system, and controls the opening of an inlet guide vane of a compressor so that a fuel-air ratio in a combustor becomes an allowable range. A fuel flow rate command is controlled in such a manner that, when the system frequency increases, after the fuel flow rate command decreases it at a first change rate, the fuel flow rate command decreases it at a second change rate smaller than the first change rate.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Power generation facilities using gas turbines as a power source are known. In this type of power generation facility, fuel supplied from a fuel supply system is mixed with compressed air generated by a compressor and combusted to produce combustion gas, which drives the turbine. The generator is electrically connected to an electric power grid having a predetermined system frequency, enabling it to supply power to the electric power grid.

[0003] In power generation facilities electrically connected to a power grid, so-called governor-free operation is performed to maintain the turbine rotation speed at a target rotation speed corresponding to the grid frequency. In governor-free operation, for example, if the grid frequency fluctuates upward due to some factor, compensation control is performed to suppress fluctuations in the grid frequency of the power grid to which the power is supplied. This is done by reducing the fuel supply rate to lower the turbine rotation speed. In this case, to maintain a favorable combustion state in the gas turbine, it is necessary to appropriately adjust the ratio of fuel to compressed air supplied to the combustor (fuel-air ratio). For example, if the amount of fuel supplied from the fuel supply system is reduced, the amount of compressed air supplied from the compressor can be correspondingly reduced to maintain an appropriate fuel-air ratio.

[0004] The amount of fuel supplied by the fuel supply system is adjusted by opening and closing a flow control valve provided in the fuel supply system. On the other hand, the amount of compressed air supplied from the compressor is adjusted by adjusting the opening degree of an inlet guide vane (IGV) provided in the compressor. Here, when the system frequency fluctuates suddenly, there is a limit to the speed at which the amount of compressed air supplied can be adjusted because there are mechanical constraints on the opening and closing operation of the inlet guide valve (for example, to prevent surging in the compressor). Therefore, if the adjustment of the amount of compressed air supplied is delayed relative to the adjustment of the amount of fuel supplied by the flow control valve, the fuel-air ratio may deviate from the allowable range, which may cause misfires or combustion oscillations in the gas turbine.

[0005] To address this issue, Patent Document 1 limits the rate of change of the input system frequency signal when the system frequency fluctuates, and adjusts the fuel flow rate command for the fuel supply system based on the limited signal change rate. This delays the rate of change of the fuel flow rate command when the system frequency fluctuates, thereby shortening the time difference with the change in the amount of compressed air supplied, and making it possible to stabilize the combustion state of the gas turbine. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-239763 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the above-mentioned Patent Document 1, the rate of change of the fuel flow command is reduced when the system frequency fluctuates, so it takes time for the gas turbine load to stabilize at the target load, which reduces the responsiveness of the compensation control to fluctuations in the system frequency.

[0008] At least one embodiment of the present disclosure has been made in consideration of the above-described circumstances, and an object of the present disclosure is to provide a gas turbine control device, a gas turbine control method, and a gas turbine control program that are capable of performing compensation control for fluctuations in system frequency with good responsiveness while maintaining a favorable combustion state of the gas turbine when the system frequency fluctuates. [Means for solving the problem]

[0009] In order to solve the above problem, a gas turbine control device according to at least one embodiment of the present disclosure includes: a combustor capable of generating combustion gas by mixing and burning fuel supplied from a fuel supply system and compressed air generated by a compressor; a turbine drivable by the combustion gas; a generator coupled to the turbine and electrically connected to an electric power grid; A gas turbine control device for controlling a gas turbine, comprising: a fuel flow rate command control unit that controls a fuel flow rate command for adjusting an aperture of a flow rate control valve provided in the fuel supply system so that the rotation speed of the turbine becomes a target rotation speed corresponding to a system frequency of the power system; an inlet guide vane control unit for controlling an opening degree of an inlet guide vane of the compressor so that a fuel-air ratio in the combustor is within an allowable range; Equipped with The fuel flow rate command control unit controls the fuel flow rate command so that, when the system frequency increases, the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change smaller than the first rate of change.

[0010] In order to solve the above problem, a gas turbine control method according to at least one embodiment of the present disclosure includes: a combustor capable of generating combustion gas by mixing and burning fuel supplied from a fuel supply system and compressed air generated by a compressor; a turbine drivable by the combustion gas; a generator coupled to the turbine and electrically connected to an electric power grid; A gas turbine control method for controlling a gas turbine, comprising: controlling a fuel flow rate command to adjust an opening degree of a flow rate control valve provided in the fuel supply system so that the rotation speed of the turbine becomes a target rotation speed corresponding to a system frequency of the power system; controlling an opening degree of an inlet guide vane of the compressor so that a fuel-air ratio in the combustor is within an allowable range; Equipped with The fuel flow rate command is controlled so that, when the system frequency increases, the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change smaller than the first rate of change.

[0011] In order to solve the above problem, a gas turbine control program according to at least one embodiment of the present disclosure includes: a combustor capable of generating combustion gas by mixing and burning fuel supplied from a fuel supply system and compressed air generated by a compressor; a turbine drivable by the combustion gas; a generator coupled to the turbine and electrically connected to an electric power grid; A gas turbine control program for controlling a gas turbine, comprising: To the computer device, controlling a fuel flow rate command to adjust an opening degree of a flow rate control valve provided in the fuel supply system so that the rotation speed of the turbine becomes a target rotation speed corresponding to a system frequency of the power system; controlling an opening degree of an inlet guide vane of the compressor so that a fuel-air ratio in the combustor is within an allowable range; is executable, The fuel flow rate command is controlled so that, when the system frequency increases, the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change smaller than the first rate of change. [Effects of the Invention]

[0012] According to at least one embodiment of the present disclosure, it is possible to provide a gas turbine control device, a gas turbine control method, and a gas turbine control program that are capable of performing compensation control for fluctuations in system frequency with good responsiveness while maintaining a favorable combustion state of the gas turbine when the system frequency fluctuates. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic configuration diagram of a gas turbine according to an embodiment. [Figure 2] FIG. 2 is a configuration diagram of the gas turbine control device of FIG. 1. [Figure 3] FIG. 1 is a configuration diagram of a fuel flow rate command control unit included in a gas turbine control device according to a reference technology. [Figure 4] 1 is a timing chart showing changes over time in each control parameter of a gas turbine control device according to a reference technology. [Figure 5] FIG. 3 is a configuration diagram of a fuel flow rate command control unit in FIG. 2. [Figure 6] 4 is a timing chart showing time variations of each control parameter of the gas turbine control device of FIG. 3. [Figure 7] This is a modification of FIG. [Figure 8] 8 is a timing chart showing time variations of each control parameter of the gas turbine control device of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the configurations described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0015] First, a gas turbine 1 that is a control target of a gas turbine control device 100 according to at least one embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram of a gas turbine according to one embodiment.

[0016] The gas turbine 1 includes a fuel supply system 2 for supplying fuel F, a compressor 3 for generating compressed air Ac, a combustor 4 for generating combustion gas Gc by mixing and burning the fuel F supplied from the fuel supply system 2 with the compressed air Ac generated by the compressor 3, and a turbine 6 driven by the combustion gas Gc. The compressor 3 and the turbine 6 are connected to one shaft by a rotor 5.

[0017] In the gas turbine 1 having such a configuration, fuel F from the fuel supply system 2 and compressed air Ac generated by the compressor 3 are supplied to the combustor 4, and these are mixed and burned to generate combustion gas Gc. The combustion gas Gc flows into the turbine 6 and functions as power for driving the turbine 6. A generator 8 is connected to an output shaft 7 of the turbine 6, and the rotational energy of the turbine 6 is converted into electrical energy by the generator 8. The electric power generated by the generator 8 is supplied to an electric power system 10 to which the generator 8 is electrically connected. After the combustion gas Gc has finished its work in the turbine 6, it is discharged to the outside as exhaust gas Gex.

[0018] The fuel supply system 2 is configured to supply fuel F to the combustor 4. The fuel F is a fossil fuel such as liquefied natural gas (LNG), but may also be a mixed fuel containing other fuels such as ammonia and hydrogen.

[0019] The fuel supply system 2 includes a fuel supply source 12 capable of supplying fuel F, and a fuel supply line 14 connecting the fuel supply source 12 and the combustor 4. The fuel supply line 14 is provided with a flow rate adjustment valve V1 for adjusting the flow rate of the fuel F, and a shutoff valve V2 for shutting off the fuel F.

[0020] The compressor 3 is configured to generate compressed air Ac by compressing combustion air A (e.g., atmospheric air) taken in from the outside. The compressor 3 is connected to a turbine 6 via a rotor 5, and is thereby able to generate compressed air Ac by utilizing the rotational force of the turbine 6. An inlet guide vane (IGV) is provided at the inlet of the combustion air A in the compressor 3. The inlet guide vane 16 is one of the objects controlled by a gas turbine control device 100, which will be described later, and by variably controlling its opening, the amount of compressed air Ac supplied to the combustor 4 can be adjusted.

[0021] Next, a description will be given of a specific configuration of the gas turbine control device 100. Fig. 2 is a configuration diagram of the gas turbine control device 100 of Fig. 1.

[0022] The gas turbine control device 100 is a control unit for controlling the gas turbine 1 and is configured with, for example, a central processing unit (CPU), a random access memory (RAM), a read-only memory (ROM), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example. The CPU reads the program into the RAM or the like and executes information processing and arithmetic operations to realize various functions. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0023] The gas turbine control device 100 includes a system frequency detection unit 102, a system frequency fluctuation determination unit 104, an actual rotation speed acquisition unit 106, an actual load acquisition unit 108, a target rotation speed calculation unit 110, a target load acquisition unit 112, a frequency fluctuation compensation bias setting unit 114, a fuel flow rate command control unit 116, a flow rate control valve control unit 118, and an inlet guide vane control unit 120.

[0024] The system frequency detection unit 102 is configured to detect the system frequency f of the power system 10. For example, the system frequency detection unit 102 can detect the system frequency f by acquiring a detection signal from a sensor installed in the power system 10. Furthermore, the detection of the system frequency f is repeatedly performed at a predetermined sampling frequency, so that it can be acquired as time-series data for identifying changes in the system frequency f.

[0025] The system frequency fluctuation determination unit 104 is configured to determine whether or not there is a fluctuation in the system frequency f, based on the system frequency f detected by the system frequency detection unit 102. The system frequency fluctuation determination unit 104 identifies the amount of change in the system frequency f as the difference between the system frequency f detected by the system frequency detection unit 102 and a reference frequency fr (for example, 50 Hz or 60 Hz in the case of a commercial power system) that is set in advance for the system frequency f. If the amount of change exceeds a preset threshold, the system frequency fluctuation determination unit 104 determines that there is a fluctuation in the system frequency f. Furthermore, if it determines that there is a fluctuation in the system frequency f, the system frequency fluctuation determination unit 104 is capable of distinguishing whether the fluctuation is in an upward direction or a downward direction based on the magnitude relationship between the system frequency f and the reference frequency fr.

[0026] The actual rotation speed acquisition unit 106 is configured to acquire the actual rotation speed R of the gas turbine 1. The actual rotation speed R can be acquired by acquiring a detection signal of a sensor installed in the turbine 6, for example.

[0027] The actual load acquisition unit 108 is configured to acquire the actual load L of the gas turbine 1. The actual load L can be acquired by acquiring a detection signal of a sensor installed in the gas turbine 1, for example.

[0028] The target rotation speed calculation unit 110 is configured to calculate a target rotation speed Rt corresponding to the actual rotation speed R. When compensation control is performed to compensate the system frequency f to the reference frequency fr by governor-free control, the target rotation speed Rt is set based on parameters related to the operating point of the gas turbine 1, such as the reference frequency fr and the actual load L. For example, the target rotation speed Rt is expressed using a conversion parameter SPSET that is correlated with the actual load L. In this embodiment, the conversion parameter SPSET is set based on the deviation ΔL (=Lt−L) between the actual load L and the target load Lt. For example, when the deviation ΔL is a positive value, a command is given to the conversion parameter SPSET to increase at a constant rate, and when the deviation ΔL is a negative value, a command is given to the conversion parameter SPSET to decrease at a constant rate.

[0029] The target load acquisition unit 112 is configured to acquire a target load Lt corresponding to the actual load L. The target load Lt is acquired, for example, based on a command signal received from a central control room (not shown) that manages the power system 10. In the following description, the target load Lt is constant unless otherwise specified, but during compensation control (governor-free control) of the system frequency f, the target load Lt may be corrected by subtracting a frequency fluctuation compensation bias Lb, which will be described later (hereinafter, when the corrected target load Lt is to be distinguished, it will be referred to as the "corrected target load Lt'" as appropriate).

[0030] The frequency fluctuation compensation bias setting unit 114 is configured to add a load setting equivalent to the actual output that decreases when the frequency increases to the target load Lt as a frequency fluctuation compensation bias Lb. The frequency fluctuation compensation bias Lb is set based on the grid frequency. The frequency fluctuation compensation bias setting unit 114 can set the corresponding frequency fluctuation compensation bias Lb by inputting the grid frequency into a function that defines the relationship between the grid frequency and the frequency fluctuation compensation bias Lb.

[0031] The fuel flow rate command control unit 116 is configured to control a fuel flow rate command CSO corresponding to the amount of fuel supplied to the gas turbine 1. Specific control contents of the fuel flow rate command CSO will be described later, but the fuel flow rate command control unit 116 is able to control the fuel flow rate command CSO by receiving the determination result of the system frequency fluctuation determination unit 104, the deviation ΔR between the actual rotation speed R and the target rotation speed Rt, and the deviation ΔL between the actual load L and the target load Lt.

[0032] The flow rate regulating valve control unit 118 is configured to control the flow rate regulating valve V1 provided in the fuel supply system 2. The flow rate regulating valve control unit 118 acquires a fuel flow rate command CSO from the fuel flow rate command control unit 116, and generates a control signal SG1 for controlling the opening degree of the flow rate regulating valve V1 provided in the fuel supply system 2 so as to realize a fuel supply amount corresponding to the fuel flow rate command CSO.

[0033] The inlet guide vane control unit 120 is configured to control the opening degree of the inlet guide vane 16 of the compressor 3. The inlet guide vane control unit 120 estimates the fuel-air ratio of the gas turbine 1 that is expected from the fuel supply amount specified based on the fuel flow rate command CSO from the fuel flow rate command control unit 116, and generates a control signal SG2 for controlling the opening degree of the inlet guide vane 16 so that the fuel-air ratio falls within a preset allowable range. However, since the change speed when controlling the opening degree of the inlet guide vane 16 is restricted by surging prevention in the compressor 3 and mechanical use of the inlet guide vane 16, the change rate of this control signal SG2 is limited within a preset range.

[0034] Here, a gas turbine control device 100' according to the reference technology and a gas turbine control method implemented by the gas turbine control device 100' will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a configuration diagram of a fuel flow rate command control unit 116' included in the gas turbine control device 100' according to the reference technology, and Fig. 4 is a timing chart showing changes over time in each control parameter of the gas turbine control device 100' according to the reference technology.

[0035] The gas turbine control device 100′ differs from the gas turbine control device 100 in that it includes a fuel flow rate command control unit 116′ instead of the fuel flow rate command control unit 116, and unless otherwise specified, the other configurations are common to the gas turbine control device 100.

[0036] As shown in Fig. 4, when the system frequency f fluctuates to rise at time t1, this upward fluctuation is detected by the system frequency fluctuation determination unit 104. Then, the frequency fluctuation compensation bias Lb set by the frequency fluctuation compensation bias setting unit 114 is subtracted from the target load Lt. As a result, at time t1, the corrected target load Lt' (=Lt-Lb) suddenly decreases with respect to the target load Lt, and accordingly, the fuel flow rate command CSO also suddenly decreases (for convenience of explanation, Fig. 4 shows the fuel flow rate command CSO decreasing at a constant rate from time t1 to t3, but this decrease in the fuel flow rate command CSO may also be instantaneous).

[0037] Here, the configuration of the fuel flow rate command control unit 116′ in the reference technology will be described with reference to Fig. 3. The fuel flow rate command control unit 116′ in the reference technology includes a first fuel flow rate command calculation unit 122, a second fuel flow rate command calculation unit 124, a third fuel flow rate command calculation unit 126, and a low value selection unit 128.

[0038] A first fuel flow rate command calculation unit 122, a second fuel flow rate command calculation unit 124, and a third fuel flow rate command calculation unit 126 calculate a first fuel flow rate command CSO1, a second fuel flow rate command CSO2, and a third fuel flow rate command CSO3, respectively, as candidates for the fuel flow rate command CSO. In the fuel flow rate command control unit 116', a low value selection unit 128 calculates the smallest one of the first fuel flow rate command CSO1, the second fuel flow rate command CSO2, and the third fuel flow rate command CSO3 as the final fuel flow rate command CSO.

[0039] The first fuel flow rate command calculation unit 122, the second fuel flow rate command calculation unit 124, and the third fuel flow rate command calculation unit 126 calculate the first fuel flow rate command CSO1, the second fuel flow rate command CSO2, and the third fuel flow rate command CSO3, respectively, as candidates for the fuel flow rate command CSO from different perspectives. For example, the first fuel flow rate command calculation unit 122 calculates the first fuel flow rate command CSO1 based on the deviation ΔL between the actual rotation speed R acquired by the actual rotation speed acquisition unit 106 and the target rotation speed Rt calculated by the target rotation speed calculation unit 110.

[0040] In this embodiment, as described above, it is assumed that the system frequency f fluctuates upward at time t1. In such a case, the fuel flow rate command control unit 116′ selects the first fuel flow rate command CSO1 as the fuel flow rate command CSO because the first fuel flow rate command CSO1 is smaller than the second fuel flow rate command CSO2 and the third fuel flow rate command CSO3 (that is, in the reference technology, the fuel flow rate command CSO is equivalent to the first fuel flow rate command CSO1). The calculation methods of the second fuel flow rate command calculation unit 124 and the third fuel flow rate command calculation unit 126 for the second fuel flow rate command CSO2 and the third fuel flow rate command CSO3 will not be described, but may be according to known examples and are not particularly limited.

[0041] 4 again, when the fuel flow rate command CSO decreases at time t1, the actual load L also starts to decrease a little later at time t2. At this time, in order to correspond to the decrease in the amount of fuel supplied to the gas turbine 1, the inlet guide vane control unit 120 starts to decrease the opening degree of the inlet guide vane 16 from time t2 so that the fuel-air ratio in the gas turbine 1 falls within the allowable range.

[0042] At time t3 when the decrease in the fuel flow command CSO has leveled off, the deviation ΔL (=L-Lt') has a positive value. Therefore, until the deviation ΔL reaches zero at time t4, the conversion parameter SPSET is instructed to decrease at a constant rate, and accordingly, the fuel flow command CSO also behaves to decrease at a constant rate.

[0043] The deviation ΔL reaches zero at time t4 and then becomes a negative value. From time t4 to t5, when the deviation ΔL (= L - Lt') becomes a negative value, the conversion parameter SPSET is commanded to gradually increase at a constant rate, and accordingly, the fuel flow command CSO also behaves as if it is increasing at a constant rate. At this time, the actual load L lags behind the fuel flow command CSO, so it shows an undershoot at some point before beginning to increase. Then, at time t5, each parameter settles and compensation control for the upward fluctuation of the system frequency f is completed.

[0044] In the gas turbine control according to the reference technology, the fuel flow command CSO decreases sharply from time t1 to time t3. When the fuel flow command CSO decreases sharply, the flow control valve V1 provided in the fuel supply system 2 is closed, thereby reducing the amount of fuel supplied to the gas turbine 1. Although the closing operation of the flow control valve V1 depends on the specifications of the flow control valve V1, such a closing operation of the flow control valve V1 is generally sufficient. Meanwhile, in response to the decrease in the amount of fuel supplied to the gas turbine 1, the inlet guide vane control unit 120 attempts to reduce the amount of compressed air Ac supplied by closing the inlet guide vane 16 in order to appropriately maintain the fuel-air ratio within an allowable range. However, as described above, the rate of change in the opening degree of the inlet guide vane 16 during the closing operation is limited, and therefore, the adjustment of the amount of compressed air Ac supplied is delayed relative to the adjustment of the amount of fuel supplied. In particular, between time t1 and time t3, the fuel flow command CSO decreases sharply, and this delay is likely to be large. This may cause the fuel-air ratio of the gas turbine 1 to deviate from the allowable range, potentially resulting in misfires, combustion oscillations, or the like in the gas turbine 1. Furthermore, in the reference technology, as described above with reference to Fig. 4, undershoot occurs between times t4 and t5, and it takes time for the compensation control to stabilize, which causes a decrease in the responsiveness of the compensation control to fluctuations in the system frequency f. These problems can be suitably solved by the gas turbine control according to this embodiment, which will be described below.

[0045] Next, gas turbine control according to this embodiment will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a configuration diagram of the fuel flow rate command control unit 116 in Fig. 2, and Fig. 6 is a timing chart showing time variations of each control parameter of the gas turbine control device 100 in Fig. 3.

[0046] 5, the fuel flow rate command control unit 116 includes a change rate limiting unit 130, as compared to the fuel flow rate command control unit 116' according to the above-described reference technology. The change rate limiting unit 130 is configured to further impose a change rate limit on the fuel flow rate command CSO selected as a low value by the low value selecting unit 128. That is, the fuel flow rate command control unit 116 is configured to output the result of applying the change rate limit by the change rate limiting unit 130 to the fuel flow rate command selected as a low value as the final fuel flow rate command CSO. The change rate limiting unit 130 includes a first change rate setting unit 132, a second change rate setting unit 134, and a high value selecting unit 136. In the configuration example of FIG. 5, the high value selection unit 136 selects a fuel flow rate command CSO with a change rate limit, and thereby a change rate limit is imposed on the final fuel flow rate command CSO to be output. However, in other configuration examples, the change rate limit may be imposed at a stage prior to the low value selection unit 128.

[0047] The first change rate setting unit 132 is configured to set the first change rate K1. The first change rate K1 is a limit value for the change rate of the fuel flow rate command CSO, which is controlled to decrease when an upward fluctuation in the system frequency f is detected. In FIG. 6 , when an upward fluctuation in the system frequency f is detected at time ta, the fuel flow rate command CSO is decreased at the first change rate K1 from time ta to time tb. This decrease in the fuel flow rate command CSO at the first change rate K1 is performed so that the fuel-air ratio of the gas turbine 1 falls within an allowable range. Specifically, the first change rate K1 is set so that the fuel-air ratio corresponding to the value CSOmin of the fuel flow rate command CSO at time tb falls within the maximum value of the allowable range. As a result, by rapidly decreasing the fuel flow rate command CSO within a range in which the fuel-air ratio does not deviate from the allowable range between times ta and tb, it is possible to improve the responsiveness of the compensation control to the upward fluctuation in the system frequency f and effectively prevent misfires and combustion oscillations.

[0048] The second change rate setting unit 134 is configured to set the second change rate K2. The second change rate K2 is the rate at which the fuel flow rate command CSO decreases after decreasing at the first change rate K1, and is set to be smaller than the first change rate K1. Fig. 6 shows how the fuel flow rate command CSO is controlled to decrease at the first change rate K1 from time ta to time tb, and then controlled to decrease at the second change rate K2 from time tb to time te.

[0049] Between times tb and te, the fuel flow rate command CSO is controlled to decrease at a second change rate K2 that is smaller than the first change rate K1, thereby reducing the likelihood of a delay occurring between the fuel flow rate command CSO and the closing operation of the inlet guide vane 16. This prevents the fuel-air ratio of the gas turbine 1 from deviating from the allowable range, and effectively prevents misfires and combustion oscillations from occurring in the compensation control that is performed when the system frequency f fluctuates upward.

[0050] Furthermore, when the fuel flow rate command CSO decreases at the second change rate K2 from time tb to time te, the deviation ΔL becomes zero at time td. Because the deviation ΔL has a positive value from time tc to time td, the conversion parameter SPSET is instructed to decrease at a constant rate. On the other hand, because the deviation ΔL has a negative value from time td to time te, the conversion parameter SPSET is instructed to increase at a constant rate.

[0051] In this embodiment, the time td at which the deviation ΔL reaches zero is earlier than the time t4 at which the deviation ΔL reaches zero in the reference technology described above, because the fuel flow command CSO is suddenly decreased at a large first rate of change K1 between times ta and tb. Furthermore, in this embodiment, the magnitude of the undershoot that occurs after the deviation ΔL turns negative after time td is also smaller than in the reference technology (or no undershoot occurs). These results indicate that the time from time t1 when an upward fluctuation occurs in the system frequency f to time tf when the system frequency f reaches a static state is also shorter than in the reference technology, improving responsiveness in compensation control for upward fluctuations in the system frequency f.

[0052] Next, a modified example will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a modified example of Fig. 5, and Fig. 8 is a timing chart showing the time variation of each control parameter of the gas turbine control device 100 of Fig. 7.

[0053] In this modification, the fuel flow rate command CSO decreases at the first rate of change K1 from time ta to time tb, and then is maintained constant for a predetermined period T indicated by time tb to time tb'. The predetermined period T during which the fuel flow rate command CSO is maintained constant can be adjusted by the maintenance control unit 138 shown in FIG. 7. In one aspect, the maintenance control unit 138 is configured to implement a timer function for counting the predetermined period. In this case, the fuel flow rate command CSO, which has completed decreasing at the first rate of change K1 at time tb, is maintained constant while the maintenance control unit 138 is counting the predetermined period T. Then, when the maintenance control unit 138 completes counting the predetermined period T at time tb', the fuel flow rate command CSO starts to decrease at the second rate of change K2, as in the above-described embodiment.

[0054] Between times ta and tb, the fuel flow rate command CSO suddenly decreases at the first change rate K1, causing a delay in the closing operation of the inlet guide vane 16. Therefore, by performing the closing operation of the inlet guide vane 16 while the fuel flow rate command CSO is maintained constant between times tb and tb', it is possible to effectively reduce the delay in the closing operation of the inlet guide vane 16 relative to the closing operation of the flow control valve V1.

[0055] The predetermined period T during which the fuel flow rate command CSO is maintained constant by the maintenance control unit 138 may be adjusted so that the value CSOm reached by decreasing the fuel flow rate command CSO at the second change rate K2 from time tb' becomes the value CSOend corresponding to the time when the compensation control is completed. In other words, the predetermined period T may be adjusted so that the compensation control is completed at time tf as a result of decreasing the fuel flow rate command CSO at the second change rate K2 from time tb'.

[0056] In the embodiment shown in FIG. 6 , the fuel flow rate command CSO decreases at the second rate of change K2 from time tb′ to reach the value CSOm at time te. The fuel flow rate command CSO is controlled to increase again from time te to tf so that it reaches the value CSOend at time tf, when the compensation control is completed. Therefore, in the embodiment described above, the opening and closing frequency of the flow control valve V1 increases, which is likely to accelerate deterioration of the flow control valve V1. In contrast, in this modified example, the predetermined period T is adjusted so that the value CSOm, which the fuel flow rate command CSO reaches by decreasing at the second rate of change K2 from time tb′, matches the value CSOend at time tf, when the compensation control is completed. This prevents a period during which the fuel flow rate command CSO increases again. As a result, the opening and closing frequency of the flow control valve V1 decreases compared to the embodiment described above, effectively suppressing deterioration of the flow control valve V1.

[0057] Furthermore, in this modification, the magnitude of the undershoot that occurs after the deviation ΔL turns negative after time td is further reduced (or no undershoot occurs), compared to the above-described embodiment. This result indicates that the time required to reach a static state at time tf is also further shortened, and excellent responsiveness is obtained in the compensation control for the upward fluctuation of the grid frequency f.

[0058] As described above, the maintenance control unit 138 may adjust the predetermined period T by setting the time of the timer function, but may also set it as the period until the deviation ΔL between the actual load L and the corrected target load Lt' becomes equal to or less than a preset threshold. In this case, the time tb' is controlled on the condition that the deviation ΔL becomes equal to or less than the threshold.

[0059] As described above, according to each of the above embodiments, when the system frequency f changes upward, the fuel flow rate command CSO is controlled so that the fuel flow rate command CSO is decreased at the first rate of change K1 and then at the second rate of change K2. Because the first rate of change K1 is larger than the second rate of change K2, when the system frequency f changes upward, it is possible to shorten the time required for the actual load L of the gas turbine 1 to stabilize at the corrected target load Lt' in the compensation control. This effectively improves the responsiveness of the compensation control to the system frequency f. Furthermore, because the second rate of change K2 is smaller than the first rate of change K1, it is possible to reduce the delay in the supply amount of compressed air Ac relative to the fuel supply amount due to the control of the opening degree of the inlet guide vane 16 when the system frequency f changes upward. This makes it possible to suppress deviation of the fuel-air ratio in the gas turbine 1 from the allowable range when the system frequency f changes, and effectively prevent misfires and combustion oscillations.

[0060] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments may be combined as appropriate.

[0061] The contents described in each of the above embodiments can be understood, for example, as follows.

[0062] (1) A gas turbine control device according to one aspect includes: a combustor capable of generating combustion gas by mixing and burning fuel supplied from a fuel supply system and compressed air generated by a compressor; a turbine drivable by the combustion gas; a generator coupled to the turbine and electrically connected to an electric power grid; A gas turbine control device for controlling a gas turbine, comprising: a fuel flow rate command control unit that controls a fuel flow rate command for adjusting an aperture of a flow rate control valve provided in the fuel supply system so that the rotation speed of the turbine becomes a target rotation speed corresponding to a system frequency of the power system; an inlet guide vane control unit for controlling an opening degree of an inlet guide vane of the compressor so that a fuel-air ratio in the combustor is within an allowable range; Equipped with The fuel flow rate command control unit controls the fuel flow rate command so that, when the system frequency increases, the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change smaller than the first rate of change.

[0063] According to the above aspect (1), when the grid frequency increases, the fuel flow rate command is controlled so that the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change. Because the first rate of change is larger than the second rate of change, when the grid frequency fluctuates, the time required for the gas turbine load to stabilize at the target load in compensation control can be shortened. This effectively improves the responsiveness of the compensation control to the grid frequency. Furthermore, because the second rate of change is smaller than the first rate of change, when the grid frequency increases, the delay in the compressed air supply amount relative to the fuel supply amount due to inlet guide vane opening control can be reduced. This prevents the fuel-air ratio in the gas turbine from deviating from the allowable range when the grid frequency fluctuates, effectively preventing misfires and combustion oscillations.

[0064] (2) In another embodiment, in the above embodiment (1), The fuel flow rate command control unit sets the amount of decrease in the fuel flow rate command at the first rate of change so that the fuel-air ratio when the fuel flow rate command is decreased at the first rate of change falls within the maximum value of the allowable range.

[0065] According to the above aspect (2), The range within which the fuel flow rate command can be decreased at the first rate of change when the system frequency increases is limited to a range within which the fuel-air ratio falls within the maximum value of the allowable range. As a result, by decreasing the fuel flow rate command at the first rate of change within a range within which it is possible to avoid an abnormal combustion state caused by the fuel-air ratio of the gas turbine deviating from the allowable range when compensation control for fluctuations in the system frequency is performed, it is possible to effectively shorten the time required for the load of the gas turbine to stabilize at the target load.

[0066] (3) In another aspect, in the above aspect (1) or (2), The fuel flow rate command control unit maintains the fuel flow rate command constant after decreasing the fuel flow rate command at the first rate of change until the fuel flow rate command starts to decrease at the second rate of change.

[0067] According to the above aspect (3), the fuel flow rate command, which decreases at the first rate of change when the system frequency increases, is maintained substantially constant until it starts to decrease at the second rate of change thereafter.

[0068] (4) In another embodiment, in any one of the above (1) to (3), The fuel flow rate command control unit controls the fuel flow rate command so that the fuel flow rate command starts to decrease at the second change rate after a predetermined period of time has elapsed since the fuel flow rate command decreased at the first change rate.

[0069] According to the above aspect (4), when the system frequency increases, the fuel flow rate command that has decreased at the first rate of change is controlled to start decreasing at the second rate of change after a predetermined period of time has elapsed.

[0070] (5) In another embodiment, in any one of the above (1) to (3), The fuel flow rate command control unit controls the fuel flow rate command so that, after the fuel flow rate command has decreased at the first rate of change, when a deviation between the turbine load and a target load becomes equal to or smaller than a threshold value, the fuel flow rate command starts to decrease at the second rate of change.

[0071] According to the above aspect (5), when the system frequency increases, the fuel flow command that has been decreased at the first rate of change is controlled to start decreasing at the second rate of change thereafter, on condition that the deviation of the gas turbine load from the target load becomes equal to or smaller than a threshold value.

[0072] (6) In another embodiment, in any one of the above (1) to (5), The allowable range is defined as a range in which no misfire or combustion fluctuation occurs in the combustor.

[0073] According to the above aspect (6), when compensation control is performed when the system frequency increases, it is possible to effectively prevent misfires and combustion oscillations from occurring in the gas turbine due to the fuel-air ratio deviating from the allowable range.

[0074] (7) A gas turbine control method according to one aspect includes: a combustor capable of generating combustion gas by mixing and burning fuel supplied from a fuel supply system and compressed air generated by a compressor; a turbine drivable by the combustion gas; a generator coupled to the turbine and electrically connected to an electric power grid; A gas turbine control method for controlling a gas turbine, comprising: controlling a fuel flow rate command to adjust an opening degree of a flow rate control valve provided in the fuel supply system so that the rotation speed of the turbine becomes a target rotation speed corresponding to a system frequency of the power system; controlling an opening degree of an inlet guide vane of the compressor so that a fuel-air ratio in the combustor is within an allowable range; Equipped with The fuel flow rate command is controlled so that, when the system frequency increases, the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change smaller than the first rate of change.

[0075] According to the above aspect (7), when the grid frequency increases, the fuel flow rate command is controlled so that the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change. Because the first rate of change is larger than the second rate of change, when the grid frequency fluctuates, the time required for the gas turbine load to stabilize at the target load in the compensation control can be shortened. This effectively improves the responsiveness of the compensation control to the grid frequency. Furthermore, because the second rate of change is smaller than the first rate of change, it is possible to reduce the delay in the amount of compressed air supplied relative to the amount of fuel supplied by controlling the opening of the inlet guide vane when the grid frequency increases. This makes it possible to suppress deviation of the fuel-air ratio in the gas turbine from the allowable range when the grid frequency fluctuates, and effectively prevent misfires and combustion oscillations.

[0076] (8) A gas turbine control program according to one aspect includes: a combustor capable of generating combustion gas by mixing and burning fuel supplied from a fuel supply system and compressed air generated by a compressor; a turbine drivable by the combustion gas; a generator coupled to the turbine and electrically connected to an electric power grid; A gas turbine control program for controlling a gas turbine, comprising: To the computer device, controlling a fuel flow rate command to adjust an opening degree of a flow rate control valve provided in the fuel supply system so that the rotation speed of the turbine becomes a target rotation speed corresponding to a system frequency of the power system; controlling an opening degree of an inlet guide vane of the compressor so that a fuel-air ratio in the combustor is within an allowable range; is executable, The fuel flow rate command is controlled so that, when the system frequency increases, the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change smaller than the first rate of change.

[0077] According to the above aspect (8), when the grid frequency increases, the fuel flow rate command is controlled so that the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change. Because the first rate of change is larger than the second rate of change, when the grid frequency fluctuates, the time required for the gas turbine load to stabilize at the target load in the compensation control can be shortened. This effectively improves the responsiveness of the compensation control to the grid frequency. Furthermore, because the second rate of change is smaller than the first rate of change, it is possible to reduce the delay in the amount of compressed air supplied relative to the amount of fuel supplied by controlling the opening of the inlet guide vane when the grid frequency increases. This makes it possible to suppress deviation of the fuel-air ratio in the gas turbine from the allowable range when the grid frequency fluctuates, and effectively prevent misfires and combustion oscillations. [Explanation of symbols]

[0078] 1. Gas turbine 2 Fuel supply system 3. Compressor 4 Combustor 5 rotors 6 Turbine 7 Output shaft 8. Generator 10 Power system 12 Fuel supply source 14 Fuel supply line V1 flow control valve V2 shutoff valve 16 Inlet guide vane 100 Gas turbine control device 102 System frequency detector 104 System frequency fluctuation determination unit 106 Actual rotation speed acquisition unit 108 Actual load acquisition unit 110 Target rotation speed calculation unit 112 Target load acquisition section 114 Frequency fluctuation compensation bias setting section 116 Fuel flow command control unit 118 Flow control valve control section 120 Inlet guide vane control section 122 1st fuel flow rate command calculation unit 124 2nd fuel flow rate command calculation unit 126 3rd fuel flow rate command calculation unit 130 Change rate limiter 132 First rate of change setting unit 134 Second rate of change setting unit 136 High Price Selection Section 138 Maintenance Control Unit

Claims

1. a combustor capable of generating combustion gas by mixing and burning fuel supplied from a fuel supply system and compressed air generated by a compressor; a turbine drivable by the combustion gas; a generator coupled to the turbine and electrically connected to an electric power grid; A gas turbine control device for controlling a gas turbine, comprising: a fuel flow rate command control unit that controls a fuel flow rate command for adjusting an aperture of a flow rate control valve provided in the fuel supply system so that the rotation speed of the turbine becomes a target rotation speed corresponding to a system frequency of the power system; an inlet guide vane control unit for controlling an opening degree of an inlet guide vane of the compressor so that a fuel-air ratio in the combustor is within an allowable range; Equipped with the fuel flow rate command control unit controls the fuel flow rate command so that, when the system frequency increases, the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change smaller than the first rate of change.

2. 2. The gas turbine control device according to claim 1, wherein the fuel flow rate command control unit sets a decrease amount of the fuel flow rate command at the first change rate so that the fuel-air ratio when the fuel flow rate command is decreased at the first change rate falls within a maximum value of the allowable range.

3. 3. The gas turbine control device according to claim 1, wherein the fuel flow rate command control unit maintains the fuel flow rate command constant during a period from when the fuel flow rate command has decreased at the first change rate to when the fuel flow rate command starts to decrease at the second change rate.

4. 3. The gas turbine control device according to claim 1, wherein the fuel flow rate command control unit controls the fuel flow rate command so that the fuel flow rate command starts to decrease at the second change rate after a predetermined period has elapsed after the fuel flow rate command has decreased at the first change rate.

5. 3. The gas turbine control device according to claim 1, wherein the fuel flow rate command control unit controls the fuel flow rate command so that the fuel flow rate command starts to decrease at the second change rate when a deviation between the load of the turbine and a target load becomes equal to or smaller than a threshold value after the fuel flow rate command has decreased at the first change rate.

6. 3. The gas turbine control device according to claim 1, wherein the allowable range is defined as a range in which no misfire or combustion fluctuation occurs in the combustor.

7. a combustor capable of generating combustion gas by mixing and burning fuel supplied from a fuel supply system and compressed air generated by a compressor; a turbine drivable by the combustion gas; a generator coupled to the turbine and electrically connected to an electric power grid; A gas turbine control method for controlling a gas turbine, comprising: controlling a fuel flow rate command to adjust an opening degree of a flow rate control valve provided in the fuel supply system so that the rotation speed of the turbine becomes a target rotation speed corresponding to a system frequency of the power system; controlling an opening degree of an inlet guide vane of the compressor so that a fuel-air ratio in the combustor is within an allowable range; Equipped with the fuel flow rate command is controlled so that, when the system frequency increases, the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change smaller than the first rate of change.

8. a combustor capable of generating combustion gas by mixing and burning fuel supplied from a fuel supply system and compressed air generated by a compressor; a turbine drivable by the combustion gas; a generator coupled to the turbine and electrically connected to an electric power grid; A gas turbine control program for controlling a gas turbine, comprising: To the computer device, controlling a fuel flow rate command to adjust an opening degree of a flow rate control valve provided in the fuel supply system so that the rotation speed of the turbine becomes a target rotation speed corresponding to a system frequency of the power system; controlling an opening degree of an inlet guide vane of the compressor so that a fuel-air ratio in the combustor is within an allowable range; is executable, the fuel flow rate command is controlled so that, when the system frequency increases, the fuel flow rate command is decreased at a first rate of change and then decreased at a second rate of change smaller than the first rate of change.

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