Control system, power generation system comprising the same, control method and control program

Abstract

To provide a control system capable of compensating for torque shortage of a generator and stabilizing a system frequency connected to a power generation system even when the system frequency connected to the power generation system decreases, and to provide a power generation system comprising the control system, a control method and a control program.SOLUTION: A control system 200 for a power generation system comprises a generator driven by a gas turbine, and a variable transmission that is installed between the gas turbine and the generator and transmits power to the generator by changing a transmission ratio between a rotational speed of a rotational shaft of the gas turbine and a rotational speed of an input shaft of the generator. The control system comprises a detection unit 210 that detects change in a system frequency connected to the power generation system, a calculation unit 211 that uses the detection result from the detection unit to calculate a transmission ratio command value for controlling the transmission ratio, and a control unit 212 that controls the transmission ratio based on the transmission ratio command value.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a control system, a power generation system including the control system, a control method, and a control program. [Background technology]

[0002] Commercial thermal power plants include conventional thermal power plants, which use steam from a boiler to drive a steam turbine and generate electricity from a generator, and combined cycle power plants, which combine a gas turbine and a steam turbine and use the exhaust gas from the gas turbine to generate steam to drive the steam turbine, thereby increasing efficiency.Compared to other power generation methods, thermal power plants have the advantage of being able to respond flexibly to fluctuations in demand, making it easier to adjust the amount of power generated in response to demand fluctuations.

[0003] In a power generation system using a gas turbine and a generator, the generator is driven by a rotating shaft that is directly or indirectly connected to the output shaft of the gas turbine. For example, Patent Document 1 discloses a configuration in which the gas turbine and the generator are connected via a reducer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-96300 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a power generation facility equipped with a generator driven by a gas turbine, when the power supply of the power generation facility falls below the power demand, the frequency of the grid connected to the power generation facility begins to drop. To compensate for the drop in the frequency of the grid connected to the power generation facility, it is necessary to increase the driving torque for rotating the generator. However, when the power supply of the power generation facility falls below the power demand, the driving torque for rotating the generator cannot be provided by the output torque of the gas turbine, and the rotation speed of the generator may drop.

[0006] However, because the compressor and the generator are mounted on the same rotating shaft, it takes a certain amount of time for the compressor's rotational speed to increase after the fuel supply rate is increased to increase the output torque of the gas turbine. As a result, the amount of compressed air generated by the compressor may temporarily be insufficient to meet the required amount of fuel supplied to the gas turbine. Therefore, rapidly increasing the fuel flow rate to the gas turbine in order to increase the output torque of the gas turbine is undesirable because it creates an imbalance in the ratio of fuel to compressed air supplied to the gas turbine. For this reason, in a power generation system using a gas turbine and a generator, a method was needed to compensate for the lack of torque to drive the generator when the grid frequency connected to the power generation system drops.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a control system that can compensate for the lack of torque to drive the generator and stabilize the system frequency connected to the power generation system even when the system frequency connected to the power generation system drops, as well as a power generation system equipped with the same, a control method, and a control program. [Means for solving the problem]

[0008] A control system according to one aspect of the present disclosure is a control system for a power generation system including a generator driven by a gas turbine, and a variable transmission installed between the gas turbine and the generator, which transmits power to the generator by changing the gear ratio between the rotational speed of a rotating shaft of the gas turbine and the rotational speed of an input shaft of the generator, and which includes a detection unit that detects changes in the frequency of a grid connected to the power generation system, a calculation unit that calculates a gear ratio command value for controlling the gear ratio using the detection result of the detection unit, and a control unit that controls the gear ratio based on the gear ratio command value.

[0009] A power generation system according to one aspect of the present disclosure includes the above-described control system, a gas turbine, a generator driven by the gas turbine, and a variable speed transmission installed between the gas turbine and the generator.

[0010] A control method according to one aspect of the present disclosure is a control method for a power generation system including a generator driven by a gas turbine and a variable transmission installed between the gas turbine and the generator and configured to transmit power to the generator by changing the gear ratio between the rotational speed of a rotating shaft of the gas turbine and the rotational speed of an input shaft of the generator, the control method including a detection step of detecting a change in a system frequency connected to the power generation system, a calculation step of calculating a gear ratio command value for controlling the gear ratio using the detection result in the detection step, and a control step of controlling the gear ratio based on the gear ratio command value.

[0011] A control program according to one aspect of the present disclosure causes a computer to function as any one of the control systems described above. [Effects of the Invention]

[0012] According to the present disclosure, even when the frequency of a grid connected to a power generation system drops, the shortage of torque for driving the generator can be compensated for, and the frequency of the grid connected to the power generation system can be stabilized. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an illustration of a power plant according to one embodiment. [Figure 2] 1 is an enlarged view of a power generation system according to an embodiment. [Figure 3] This is an example of changing the gear ratio of a CVT variable transmission. [Figure 4] FIG. 1 is a diagram illustrating an example of a hardware configuration of a control system according to an embodiment. [Figure 5] FIG. 2 is a functional configuration diagram illustrating an example of functions possessed by a control system according to an embodiment. [Figure 6] 4 is an example of a calculation circuit for a gear ratio command value included in the control system according to one embodiment. [Figure 7] 3 is an example of a calculation circuit for a fuel flow rate command value included in the control system according to one embodiment. [Figure 8] 10 is a graph illustrating the behavior of each parameter when the frequency of a grid connected to a power generation system according to an embodiment drops. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, several embodiments according to the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. In the following description, "up" and "upper" refer to the upper side in the vertical direction, and "lower" and "lower" refer to the lower side in the vertical direction, and the vertical direction is not precise and may include errors.

[0015] FIG. 1 is an illustration of a power plant according to one embodiment. As shown in FIG. 1, the power generation system 300 includes a control system 200, a gas turbine 16, a generator 17 driven by the gas turbine 16, and a variable transmission CVT installed between the gas turbine 16 and the generator 17.

[0016] The gas turbine 16 includes a compressor 18, a combustor 19, and a turbine 20, and the compressor 18 and the turbine 20 are connected by a rotating shaft. Compressed air from the compressor 18 is supplied to the combustor 19. The combustor 19 generates combustion gas by mixing the compressed air with fuel and burning it, and supplies the generated combustion gas to the turbine 20. The turbine 20 uses the supplied combustion gas to rotate its rotating shaft, which then rotates and drives the generator 17 via a variable transmission CVT. The electric power generated by the generator 17 is sent to, for example, a power supply system (not shown).

[0017] The power generation system 300 may be a GTCC (Gas Turbine Combined Cycle) power plant equipped with a heat recovery steam generator (not shown). The heat recovery steam generator receives exhaust gas from a turbine 20 of the gas turbine 16 and generates steam by exchanging heat between feedwater supplied from a condenser and the exhaust gas from the turbine 20. The generated steam is supplied to a steam turbine that drives a generator and then recovered in the condenser. After heat exchange in the heat recovery steam generator, the exhaust gas is subjected to treatments such as denitrification and desulfurization and then released into the atmosphere.

[0018] Next, control relating to the gear ratio of the variable transmission CVT according to this embodiment will be described. FIG. 2 is an enlarged view of a power generation system 300 according to one embodiment. The control system 200 provided in the power generation system 300 controls the gear ratio of the variable transmission CVT. The power generation system 300 also includes a gas turbine rotation speed detection unit S1 that detects the rotation speed of the gas turbine 16, and a generator rotation speed detection unit S2 that detects the rotation speed of the generator 17. The detection results of the gas turbine rotation speed detection unit S1 and the generator rotation speed detection unit S2 are output to the control system 200.

[0019] When the power supply of the power generation system 300 falls below the power demand during operation of the power generation system 300, the frequency of the grid connected to the power generation system 300 drops. Furthermore, if the state in which the power supply of the power generation system 300 falls below the power demand continues, the output torque of the gas turbine 16 may not be sufficient to drive the generator 17, and the rotation speed of the generator 17 may drop.

[0020] In such a case, control system 200 detects a change in the frequency of the grid connected to power generation system 300, calculates a gear ratio command value for controlling the gear ratio of variable transmission CVT based on the detection result, and controls the gear ratio of variable transmission CVT using the gear ratio command value. Because control system 200 controls the gear ratio of variable transmission CVT, power generation system 300 can maintain the rotation speed of generator 17 even when the output torque of gas turbine 16 cannot keep up with the torque required to drive generator 17.

[0021] FIG. 3 shows an example of when the gear ratio of the variable transmission CVT is changed. 3(a) shows an example of a state in which the pulley diameter on the gas turbine 16 side is enlarged (pulley width is narrowed) and the pulley diameter on the generator 17 side is reduced (pulley width is widened). By changing the speed ratio in this way, the output rotation speed on the generator 17 side increases and the output torque decreases.

[0022] 3(b) shows an example of a state in which the pulley diameter on the gas turbine 16 side is reduced (pulley width is widened) and the pulley diameter on the generator 17 side is increased (pulley width is narrowed). This change in the gear ratio reduces the output rotation speed on the generator 17 side and increases the output torque.

[0023] In this way, the control system 200 controls the rotation speed of the generator 17 by changing the gear ratio of the variable speed transmission CVT as shown in FIG. For example, when the system frequency connected to the power generation system 300 drops, the control system 200 reduces the pulley diameter on the gas turbine 16 side (widens the pulley width) and increases the pulley diameter on the generator 17 side (closes the pulley width), as shown in Figure 3(b), to suppress a drop in rotation speed by increasing the torque that drives the generator 17, thereby changing the gear ratio.

[0024] Next, the control system 200 according to this embodiment will be described. Fig. 4 is a diagram showing an example of the hardware configuration of a control system 200 according to an embodiment. As shown in Fig. 4, the control system 200 is a computer, and includes, for example, a CPU (Central Processing Unit: processor) 201, a main memory 202, a secondary storage 203, a communication interface 204, etc. The control system 200 may also include an input device 205 that accepts input from a user, a display 206, etc. These components are connected via, for example, a bus 208.

[0025] The main memory device 202 is composed of writable memory such as cache memory and RAM (Random Access Memory), and is used as a working area for reading out programs executed by the CPU 201 and writing data processed by the programs. The secondary storage device 203 is a non-transitory computer-readable storage medium. Examples of the secondary storage device 203 include a magnetic disk such as a hard disk drive (HDD), a magneto-optical disk, a CD-ROM, a DVD-ROM, and a semiconductor memory such as a solid state drive (SSD).

[0026] FIG. 5 is a functional configuration diagram showing an example of functions of a control system 200 according to an embodiment. The control system 200 detects a change in the frequency of a grid connected to the power generation system 300, calculates a gear ratio command value for controlling the gear ratio of the variable transmission CVT using the detection result, and controls the gear ratio of the variable transmission CVT using the gear ratio command value. In addition to controlling the gear ratio of the variable transmission CVT, the control system 200 may also use the detection result to calculate a fuel flow rate command value for controlling the fuel flow rate supplied to the gas turbine 16, and control the fuel flow rate supplied to the gas turbine 16 using the fuel flow rate command value. Specifically, as shown in FIG. 5, the control system 200 includes a detection unit 210, a calculation unit 211, and a control unit 212.

[0027] A series of processes for realizing the various functions described below is stored in the secondary storage device 203 (see FIG. 4) in the form of a program (e.g., a control program), for example, and the CPU 201 reads this program into the main storage device 202 and executes information processing and arithmetic processing to realize the various functions. Note that the program may be pre-installed in the secondary storage device 203, provided in a state stored in another 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.

[0028] The detection unit 210 detects a change in the frequency of the system connected to the power generation system 300. The detection unit 210 is, for example, one of various sensors that detects a change in the frequency of the system connected to the power generation system 300. For example, the detection unit 210 detects a change in the frequency of the system connected to the power generation system 300 at predetermined intervals and detects a change in the frequency of the system connected to the power generation system 300 by calculating a difference between a current detected amount and a previous detected amount. The detection unit 210 also outputs the change in the frequency of the system connected to the power generation system 300 to the calculation unit 211. Furthermore, the detection unit 210 may detect a change in the frequency of the grid connected to the power generation system 300 when the difference between the current detected amount and the previous detected amount is equal to or greater than a predetermined threshold. Furthermore, the frequency of the grid connected to the power generation system 300 detected by the detection unit 210 may be stored sequentially in the secondary storage device 203.

[0029] Without being limited to this example, the detection unit 210 may detect the rotational speed of the gas turbine 16, the current value of the output of the generator 17, the rotational speed of the generator 17, the exhaust gas temperature of the gas turbine 16, and the internal pressure of the combustor 19 provided in the gas turbine 16, in addition to the frequency of the system connected to the power generation system 300, as various information for controlling the gear ratio of the variable transmission CVT. Furthermore, the detection unit 210 may acquire the detection results of the gas turbine rotational speed detection unit S1 and the generator rotational speed detection unit S2, and output them to the calculation unit 211.

[0030] Calculation unit 211 calculates a gear ratio command value for controlling the gear ratio of variable transmission CVT using the detection result of detection unit 210. Calculation unit 211 has the functions of, for example, a function generator, a comparator, an adder, a multiplier, a PI (Proportional-Integral) controller, and a minimum selector. Calculation unit 211 also outputs the calculated command value for the gear ratio of variable transmission CVT to control unit 212. Furthermore, the calculation unit 211 may use, as appropriate, planned values ​​or set values ​​of various parameters based on the operation plan of the power generation system 300 stored in the secondary storage device 203 as input values ​​for each calculation process.

[0031] In addition to calculating the gear ratio, the calculation unit 211 also calculates a fuel flow rate command value for controlling the flow rate of fuel supplied to the gas turbine 16 using the detection results of the detection unit 210. Specifically, the calculation unit 211 calculates the fuel flow rate command value for controlling the flow rate of fuel supplied to the gas turbine 16 using, for example, the detection results of the detection unit 210, the gas turbine rotation speed detection unit S1, and the generator rotation speed detection unit S2. The calculation unit 211 also uses, as input values, a rotation speed setting value of the gas turbine 16, a rotation speed setting value of the generator 17, and a correction value for the rotation speed of the generator 17 corresponding to the output of the generator 17, which are stored in the secondary storage device 203. The values ​​stored in the secondary storage device 203 may be used as these input values.

[0032] Control unit 212 controls the gear ratio of variable transmission CVT using the gear ratio command value calculated by calculation unit 211. Specifically, control unit 212 outputs the gear ratio command value to variable transmission CVT and controls the gear ratio of variable transmission CVT.

[0033] Furthermore, the control unit 212 controls the flow rate of fuel supplied to the gas turbine 16 using the fuel flow rate command value calculated by the calculation unit 211. Specifically, the control unit 212 outputs the fuel flow rate command value to a fuel flow rate control valve to control the flow rate of fuel supplied to the gas turbine 16. In this way, the control unit 212 controls the gear ratio of the variable transmission CVT and the flow rate of fuel supplied to the gas turbine 16, thereby maintaining the torque of the generator 17.

[0034] (Regarding the calculation process of the gear ratio command value) Fig. 6 shows an example of a calculation circuit for a gear ratio command value provided in control system 200 according to one embodiment. Hereinafter, a calculation process for calculating a gear ratio command value for changing the gear ratio of variable transmission CVT will be described with reference to Fig. 6. Note that in this embodiment, the calculations described below are performed by calculation unit 211, but this is not limiting and other components provided in control system 200 may perform the calculations.

[0035] In the following description, when calculation unit 211 calculates a gear ratio command value for changing the gear ratio of variable transmission CVT, it uses as input values ​​the set value of the rotation speed of generator 17, the current value of the rotation speed of generator 17 detected by generator rotation speed detection unit S2, and the system frequency connected to power generation system 300. Note that the input values ​​for calculating the gear ratio command value for changing the gear ratio of variable transmission CVT are not limited to these, and other parameters may be used as input values.

[0036] The set value of the rotation speed of the generator 17 and the current value of the rotation speed of the generator 17 are input to the comparator com1. The comparator com1 calculates the deviation between the set value of the rotation speed of the generator 17 and the current value of the rotation speed of the generator 17, and outputs the deviation to the multiplier mul1.

[0037] On the other hand, the frequency of the system connected to the power generation system 300 is input to a function generator F1. A function that outputs a correction value for the rotation speed of the generator 17 based on the frequency of the system connected to the power generation system 300 is set in the function generator F1. The function generator F1 then outputs the correction value for the rotation speed of the generator 17 to a multiplier mul1. Note that the function set in the function generator F1 is, for example, a function that calculates a correction value by predicting a decrease in the frequency of the system connected to the power generation system 300.

[0038] The multiplier mul1 multiplies the deviation between the set value of the rotation speed of the generator 17 input from the comparator com1 and the current value of the rotation speed of the generator 17 by the correction value of the rotation speed of the generator 17 input from the function generator F1. Then, the multiplier mul1 outputs the multiplication result to the PI controller PI1.

[0039] The PI controller PI1 performs proportional-integral control (PI control) based on the multiplied value input from the comparator com1. The PI controller PI1 calculates a gear ratio command value for the variable transmission CVT by proportional-integral control and outputs it to the adder Add.

[0040] Meanwhile, the current value of the rotation speed of the generator 17 detected by the generator rotation speed detection unit S2 is input to the comparator com1 and also to a function generator F2. The function generator F2 is set with a function that outputs a gear ratio command value for the variable transmission CVT based on the current value of the rotation speed of the generator 17. The function generator F2 then outputs the gear ratio command value for the variable transmission CVT to an adder Add.

[0041] Adder Add adds the gear ratio command value for variable transmission CVT input from PI controller PI1 and the gear ratio command value for variable transmission CVT input from function generator F2. Adder Add then outputs the gear ratio command value for variable transmission CVT, which is the addition result, to control unit 212. Then, the control unit 212 controls the variable transmission CVT based on the gear ratio command value for the variable transmission CVT input from the adder Add.

[0042] (Fuel flow command value calculation circuit) Next, Fig. 7 shows an example of a calculation circuit for a fuel flow rate command value included in the control system 200 according to one embodiment. Hereinafter, a calculation process for calculating a fuel flow rate command value for changing the fuel flow rate supplied to the gas turbine 16 will be described with reference to Fig. 7. Note that in this embodiment, each calculation described below is performed by the calculation unit 211, but this is not limiting and the calculations may be performed by other components included in the control system 200.

[0043] In the following description, the calculation unit 211 uses, as input values, for example, a fuel flow rate command value corresponding to the current value of the rotation speed of the generator 17 detected by the generator rotation speed detection unit S2, a load correction value of the generator 17, a fuel flow rate command value corresponding to the output of the generator 17, a fuel flow rate command value corresponding to the set value of the rotation speed of the gas turbine 16, a fuel flow rate command value corresponding to the current value of the rotation speed of the gas turbine 16, a fuel flow rate command value corresponding to the temperature of the exhaust gas of the gas turbine 16, and a fuel flow rate command value corresponding to the internal pressure of the combustor 19 included in the gas turbine 16. Note that the input values ​​for calculating the fuel flow rate command value for changing the flow rate of fuel supplied to the gas turbine 16 are not limited to these, and other parameters may be used as input values.

[0044] A fuel flow rate command value corresponding to the set value of the rotation speed of the generator 17 and a fuel flow rate command value corresponding to the current value of the rotation speed of the generator 17 are input to the comparator com2. The comparator com2 calculates the deviation between the fuel flow rate command value corresponding to the set value of the rotation speed of the generator 17 and the fuel flow rate command value corresponding to the current value of the rotation speed of the generator 17, and outputs the deviation to the multiplier mul2.

[0045] Meanwhile, a load correction value for the generator 17 is input to a function generator F3. A function that outputs a correction value for the fuel flow command value based on the load correction value for the generator 17 is set in the function generator F3. Then, the function generator F1 outputs the correction value for the fuel flow command value to a multiplier mul2.

[0046] The multiplier mul2 multiplies the deviation of the fuel flow command value input from the comparator com2 by the correction value for the rotation speed of the generator 17 input from the function generator F2, and then outputs the multiplied value, which is the result of the multiplication, to the minimum selector MS.

[0047] On the other hand, a fuel flow rate command value corresponding to the set value of the rotational speed of the gas turbine 16 and a fuel flow rate command value corresponding to the current value of the rotational speed of the gas turbine 16 are input to a comparator com3. The comparator com3 calculates the deviation between the fuel flow rate command value corresponding to the set value of the rotational speed of the gas turbine 16 and the fuel flow rate command value corresponding to the current value of the rotational speed of the gas turbine 16, and outputs the deviation to a multiplier mul3.

[0048] The multiplier mul3 multiplies the deviation of the fuel flow command value input from the comparator com3 by a stabilization rate α [%]. The stabilization rate α may be a predetermined value, or may be changed as appropriate based on various parameters based on the operation plan of the power generation system 300. Then, the multiplier mul3 outputs the fuel flow command value multiplied by the stabilization rate α to the minimum selector MS. The adjustment factor α is a numerical value that serves as an index for increasing or decreasing the output of the generator 17 in response to a change in the system frequency when the system frequency rises or falls.

[0049] In addition to the fuel flow rate command value input from multiplier mul2 and the fuel flow rate command value input from multiplier mul3, the minimum selector MS receives a fuel flow rate command value corresponding to the output of the generator 17, a fuel flow rate command value corresponding to the temperature of the exhaust gas of the gas turbine 16, and a fuel flow rate command value corresponding to the internal pressure of the combustor 19. The minimum selector MS selects the minimum value from the plurality of input fuel flow rate command values. The minimum selector MS then outputs the selected minimum value of the fuel flow rate command values ​​to the control unit 212. The control unit 212 then controls the flow rate of fuel supplied to the gas turbine 16 based on the fuel flow rate command value input from the minimum selector MS.

[0050] (Parameters when the grid frequency drops) FIG. 8 is a graph illustrating the behavior of each parameter when the frequency of a grid connected to the power generation system 300 according to one embodiment drops. As shown in Fig. 8, the frequency of the grid connected to the power generation system 300 drops after time t1. If the gear ratio of the variable transmission CVT is constant, and the frequency of the grid connected to the power generation system 300 drops, the drive torque of the generator 17 cannot be covered by the output torque of the gas turbine 16, and the rotation speed of the generator drops.

[0051] The control system 200 according to this embodiment calculates a gear ratio command value for the variable transmission CVT based on the system frequency connected to the power generation system 300 and the rotation speed of the generator 17, and controls the gear ratio of the variable transmission CVT based on the calculated gear ratio command value. When the system frequency connected to the power generation system 300 drops, the control system 200 reduces the pulley diameter on the gas turbine 16 side (widens the pulley width) and increases the pulley diameter on the generator 17 side (closes the pulley width), thereby changing the gear ratio of the variable transmission CVT (see FIG. 3(b)).

[0052] The control system 200 also calculates a fuel command value based on the load correction value of the generator 17 and the rotation speed of the generator 17, and selects an optimal value from the calculated multiple fuel flow rate command values. The control system 200 then controls the fuel flow rate to be supplied to the gas turbine 16 based on the selected fuel flow rate command value. Furthermore, the control system 200 calculates an opening command value for the inlet guide vanes of the compressor 18 included in the gas turbine 16 in response to the selected fuel flow rate command value, and controls the opening of the inlet guide vanes of the compressor 18 based on the calculated opening command value. In other words, the control system 200 controls the air flow rate taken in by the compressor 18 in response to the fuel flow rate to be supplied to the gas turbine 16.

[0053] In this way, the control system 200 changes the gear ratio command value for controlling the gear ratio of the variable transmission CVT and the fuel flow rate command value for controlling the fuel flow rate supplied to the gas turbine 16. As a result, even when the frequency of the system connected to the power generation system 300 drops, the rotation speed of the generator 17 is suppressed from dropping, and the frequency of the system connected to the power generation system 300 is stabilized.

[0054] According to the control system 200 described above, the control unit 212 controls the gear ratio of the variable transmission CVT based on changes in the frequency of the system connected to the power generation system 300. As a result, even when the frequency of the system connected to the power generation system 300 drops and it becomes difficult to provide the drive torque required by the generator 17 with the output torque of the gas turbine 16, the drive torque of the generator 17 can be provided by controlling the gear ratio of the variable transmission. Therefore, even when the frequency of the system connected to the power generation system 300 drops, the insufficient drive torque of the generator 17 can be compensated for during the period until the fuel flow rate supplied to the gas turbine 16 reaches the desired flow rate, thereby stabilizing the system frequency.

[0055] Furthermore, according to the control system 200 described above, the control unit 212 controls the speed ratio of the variable transmission CVT and also controls the fuel flow rate supplied to the gas turbine 16 based on changes in the frequency of the system connected to the power generation system 300. By controlling the fuel flow rate of the gas turbine 16 in addition to controlling the speed ratio of the variable transmission CVT, it is possible to increase the output of the generator 17 while appropriately maintaining a balance between the amount of compressed air generated by the compressor 18 and the fuel flow rate of the gas turbine 16, thereby improving the responsiveness of the power generation system 300.

[0056] Although the present disclosure has been described using embodiments, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. Various modifications and improvements can be made to the above embodiments without departing from the gist of the present disclosure, and such modifications and improvements are also included in the technical scope of the present disclosure. Furthermore, the above embodiments may be combined as appropriate. For example, the variable transmission installed between the gas turbine 16 and the generator 17 is not limited to a CVT, and a transmission mechanism such as a fluid coupling or a fluid transmission may be used.

[0057] (Additional notes) The control system, the power generation system including the control system, the control method, and the control program described in each of the above-described embodiments can be understood, for example, as follows. A control system according to a first aspect of the present disclosure is a control system (200) for a power generation system including a generator driven by a gas turbine and a variable transmission installed between the gas turbine and the generator, which transmits power to the generator by changing the gear ratio between the rotational speed of the rotating shaft of the gas turbine and the rotational speed of the input shaft of the generator, and includes a detection unit (210) that detects changes in the system frequency connected to the power generation system, a calculation unit (211) that calculates a gear ratio command value for controlling the gear ratio using the detection result of the detection unit, and a control unit (212) that controls the gear ratio based on the gear ratio command value.

[0058] According to the control system of the present disclosure, the controller controls the gear ratio of the variable transmission installed between the gas turbine and the generator based on changes in the frequency of the grid connected to the power generation system. As a result, even when the frequency of the grid connected to the power generation system drops and it becomes difficult to provide the drive torque required by the generator with the output torque of the gas turbine, the drive torque of the generator can be provided by controlling the gear ratio of the variable transmission. Therefore, even when the frequency of the grid connected to the power generation system drops, the insufficient drive torque of the generator can be compensated for, and the frequency of the grid connected to the power generation system can be stabilized by the gear ratio of the variable transmission.

[0059] In the control system according to a second aspect of the present disclosure, in the first aspect, the calculation unit calculates the gear ratio command value and, in addition, calculates a fuel flow rate command value for controlling a fuel flow rate supplied to the gas turbine using a detection result of the detection unit, and the control unit controls the fuel flow rate based on the fuel flow rate command value.

[0060] According to the control system of the present disclosure, the control unit controls the speed ratio of the variable transmission and also controls the fuel flow rate supplied to the gas turbine based on changes in the grid frequency connected to the power generation system. By controlling the fuel flow rate of the gas turbine in addition to controlling the speed ratio of the variable transmission, it is possible to increase the output of the generator while appropriately maintaining a balance between the amount of compressed air generated by the compressor and the fuel flow rate of the gas turbine, thereby improving the responsiveness of the power generation system.

[0061] A power generation system (300) according to a third aspect of the present disclosure includes the control system according to any one of the first and second aspects, a gas turbine (16), a generator (17) driven by the gas turbine, and a continuously variable transmission (CVT) installed between the gas turbine and the generator.

[0062] A control method according to a fourth aspect of the present disclosure is a control method for a power generation system including a generator driven by a gas turbine and a variable transmission installed between the gas turbine and the generator and configured to transmit power to the generator by changing the gear ratio between the rotational speed of a rotating shaft of the gas turbine and the rotational speed of an input shaft of the generator, the control method including a detection step of detecting a change in a system frequency connected to the power generation system, a calculation step of calculating a gear ratio command value for controlling the gear ratio using the detection result in the detection step, and a control step of controlling the gear ratio based on the gear ratio command value.

[0063] A control program according to a fifth aspect of the present disclosure causes a computer to function as the control system according to any one of the first and second aspects. [Explanation of symbols]

[0064] 16 Gas turbine 17. Generator 18 Compressor 19 Combustor 20 Turbine 200 Control System 201 CPU 202 Main storage 203 Secondary storage device 204 Communication Interface 205 Input Devices 206 Display 208 Bus 210 Detection unit 211 Arithmetic section 212 Control Unit 300 Power Generation System Add adder CVT variable transmission F1~F3 Function Generator MS Minimum Selector PI1 PI controller S1 Gas turbine rotation speed detection unit S2 Generator rotation speed detector com1~com3 comparator mul1~mul3 multipliers

Claims

1. A control system for a power generation system including a generator driven by a gas turbine, and a variable speed transmission installed between the gas turbine and the generator, the variable speed transmission changing a gear ratio between a rotational speed of a rotary shaft of the gas turbine and a rotational speed of an input shaft of the generator to transmit power to the generator, a detection unit that detects a change in a grid frequency connected to the power generation system; a calculation unit that calculates a gear ratio command value for controlling the gear ratio using the detection result of the detection unit; a control unit that controls the gear ratio based on the gear ratio command value; A control system comprising:

2. the calculation unit calculates the gear ratio command value and also calculates a fuel flow rate command value for controlling a fuel flow rate supplied to the gas turbine using a detection result of the detection unit; The control system according to claim 1 , wherein the control unit controls the fuel flow rate based on the fuel flow rate command value.

3. The control system according to claim 1 or 2; A gas turbine, a generator driven by the gas turbine; a variable speed transmission installed between the gas turbine and the generator; A power generation system comprising:

4. A control method for a power generation system including a generator driven by a gas turbine, and a variable speed transmission installed between the gas turbine and the generator, the variable speed transmission changing a gear ratio between a rotation speed of a rotary shaft of the gas turbine and a rotation speed of an input shaft of the generator to transmit power to the generator, the method comprising: a detecting step of detecting a change in a grid frequency connected to the power generation system; a calculation step of calculating a gear ratio command value for controlling the gear ratio using the detection result in the detection step; a control step of controlling the gear ratio based on the gear ratio command value; A control method comprising:

5. A control program that causes a computer to function as the control system according to claim 1 or 2.

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