Control device, control method, and control program for a steam power plant

Abstract

To provide a control device, a control method and a control program for a steam power generation plant which allows separation of some steam generators while maintaining a stable operation state.SOLUTION: At least one of steam supply systems in a composite cycle power generation plant comprises: a first steam generator; a first passage in which steam generated by the first steam generator flows; a second steam generator; a second passage in which steam generated by the second steam generator flows; a third passage connecting a merging part of the first passage and the second passage and a steam turbine; and a bypass passage branching from the first passage. A first cutoff valve and a second cutoff valve are arranged in the first passage and the second passage, and a bypass valve is arranged in the bypass passage. In such a plant, an opening operation from a full-closed state of the bypass valve is started at a separation start timing of starting a closing operation from a full-open state of the first cutoff valve with the second cutoff valve fully opened.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a control device, a control method, and a control program for a steam power plant.

Background Art

[0002] There is known a steam power plant that generates electricity with a generator connected to a steam turbine by driving the steam turbine with steam generated in a steam generation unit. The amount of steam required by the steam turbine changes according to the power generation load. The steam generation unit includes a plurality of steam generators in order to adjust the steam supply amount in response to such a power generation load, and may control the number of steam generators operating according to the power generation load. For example, when the power generation load decreases and the amount of steam required by the steam turbine decreases, the steam supply amount from the steam generation unit is controlled by disconnecting some of the steam generators constituting the steam generation unit from the steam supply system.

[0003] For example, Patent Document 1 discloses a control technique for disconnecting some of the steam generators from the steam supply system. In this document, a plurality of first passages through which steam from a plurality of steam generators flows merge with each other, and steam is supplied from the confluence point to the steam turbine through a second passage. And each of the plurality of first passages is provided with a shut-off valve, and a bypass passage provided with a bypass valve for bypassing the steam turbine is branched upstream of the shut-off valve. In such a configuration, when disconnecting a specific steam generator from the steam supply system to the steam turbine, when starting the closing operation of the shut-off valve corresponding to the steam generator from the fully open state, the opening degree control of the bypass valve is performed. The opening degree control of the bypass valve is performed so that the outlet pressure of the steam generator to be disconnected becomes a value obtained by adding a certain bias value to the outlet pressure set value of the remaining steam generators on the side where the operation continues, so that the outlet pressure of the steam generator to be disconnected becomes higher than the pressure downstream of the confluence point with the first passage of the other steam generators, thereby maintaining the forward flow of steam to the steam generator to be disconnected (that is, preventing the reverse flow of steam to the steam generator to be disconnected). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-31859 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the above-mentioned Patent Document 1, the control of the bypass valve opening degree during disconnection is performed after the shut-off valve begins to open from its fully open state. Furthermore, the control of the bypass valve opening degree at this time is performed so that the outlet pressure of the steam generator to be disconnected is a value obtained by adding a certain bias value to the outlet pressure set value of the steam generator on the side that continues to operate. Therefore, if the pressure on the second passage side rises before the shut-off valve reaches the fully closed state, the opening operation of the bypass valve may be delayed, and the outlet pressure of the steam generator may rise.

[0006] In addition, in steam power plants, steam is sometimes supplied to a steam turbine from steam generators that produce steam at different pressures (for example, a high-pressure steam generator that produces high-pressure steam and a low-pressure steam generator that produces low-pressure steam). In this case, the thrust balance of the steam turbine is ensured by the supply location and supply amount of steam at different pressures. In such a configuration, if the opening degree control of the bypass valve during disconnection described in Patent Document 1 is introduced, the outlet pressure of the steam generator to be disconnected will be set to a value obtained by adding a certain bias value to the outlet pressure set value of the steam generator that continues to operate. Depending on the magnitude of the bias value, the steam flow balance may be disrupted during disconnection.

[0007] At least one embodiment of this disclosure has been made in view of the above circumstances and aims to provide a control device, control method, and control program for a steam power plant that can disconnect some steam generators while maintaining a stable operating state. [Means for solving the problem]

[0008] A control device according to at least one embodiment of this disclosure solves the above problem, The generator is equipped with a high-pressure steam supply system and an intermediate-pressure steam supply system, which are capable of supplying high-pressure steam and intermediate-pressure steam, respectively, to the steam turbine connected to the generator. At least one of the high-pressure steam supply system or the medium-pressure steam supply system is First steam generator and, The first passage through which the steam generated in the first steam generator flows, The second steam generator, The second passage through which the steam generated in the second steam generator flows, A second shut-off valve provided in the second passage, A third passage connecting the confluence of the first passage and the second passage to the steam turbine, A first shut-off valve provided in the first passage, A bypass passage that branches off from the first passage upstream of the first shut-off valve, A bypass valve provided in the bypass passage, A control device for a combined cycle power plant, comprising: At the disconnection start timing, when the second shut-off valve is fully open and the first shut-off valve starts closing from its fully open state, the bypass valve starts opening from its fully closed state.

[0009] A control method according to at least one embodiment of this disclosure solves the above problem. The generator is equipped with a high-pressure steam supply system and an intermediate-pressure steam supply system, which are capable of supplying high-pressure steam and intermediate-pressure steam, respectively, to the steam turbine connected to the generator. At least one of the high-pressure steam supply system or the medium-pressure steam supply system is First steam generator and, The first passage through which the steam generated in the first steam generator flows, A first shut-off valve provided in the first passage, The second steam generator, The second passage through which the steam generated in the second steam generator flows, A second shut-off valve provided in the second passage, A third passage connecting the confluence of the first passage and the second passage to the steam turbine, A bypass passage that branches off from the first passage upstream of the first shut-off valve, A bypass valve provided in the bypass passage, A control method for a combined cycle power plant, At the disconnection start timing, when the second shut-off valve is fully open and the first shut-off valve starts closing from its fully open state, the bypass valve starts opening from its fully closed state.

[0010] A control program according to at least one embodiment of this disclosure solves the above problem. The generator is equipped with a high-pressure steam supply system and an intermediate-pressure steam supply system, which are capable of supplying high-pressure steam and intermediate-pressure steam, respectively, to the steam turbine connected to the generator. At least one of the high-pressure steam supply system or the medium-pressure steam supply system is First steam generator and, The first passage through which the steam generated in the first steam generator flows, A first shut-off valve provided in the first passage, The second steam generator, The second passage through which the steam generated in the second steam generator flows, A second shut-off valve provided in the second passage, A third passage connecting the confluence of the first passage and the second passage to the steam turbine, A bypass passage that branches off from the first passage upstream of the first shut-off valve, A bypass valve provided in the bypass passage, A control program for a combined cycle power plant, Using a computer At the disconnection start timing, when the second shut-off valve is fully open and the first shut-off valve is in the closing position, the bypass valve is in the opening position from its fully closed position.

Advantages of the Invention

[0011] According to at least one embodiment of the present disclosure, it is possible to provide a control device, a control method, and a control program for a steam power generation plant in which some steam generators can be disconnected while maintaining a stable operating state.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic configuration diagram of a combined cycle power generation plant according to an embodiment. [Figure 2] It is a diagram showing the opening and closing states of each valve before disconnecting the first steam generator in the combined cycle power generation plant of FIG. 1. [Figure 3] It is a diagram showing the opening and closing states of each valve after disconnecting the first steam generator in the combined cycle power generation plant of FIG. 1. [Figure 4] It is a block diagram showing a control device for a combined cycle power generation plant according to an embodiment. [Figure 5] It is a block diagram showing the internal configuration of the bypass steam pressure set value calculation unit of FIG. 4. [Figure 6] It is a flowchart showing a control method for a combined cycle power generation plant according to an embodiment. [Figure 7] It is a time chart showing changes in various indexes of a combined cycle power generation plant corresponding to the control method of FIG. 6.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the configurations described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0014] First, the configuration of the combined cycle power generation plant 1 that is the control target of the control device 100 according to at least one embodiment of the present disclosure will be described. FIG. 1 is a schematic configuration diagram of the combined cycle power generation plant 1 according to an embodiment.

[0015] In this embodiment, a multi-shaft combined cycle power plant 1 is described, which is equipped with a single steam turbine ST, multiple gas turbines GT, and multiple associated heat recovery boilers HRSG (Heat Recovery Steam Generators). The combined cycle power plant 1 shown in Figure 1 is equipped with a first gas turbine GT1 and a second gas turbine GT2 as the multiple gas turbines GT. The combined cycle power plant 1 is also equipped with a first heat recovery boiler HRSG1 that generates steam using the waste heat of the first gas turbine GT1, and a second heat recovery boiler HRSG2 that generates steam using the waste heat of the first gas turbine GT1 as the multiple heat recovery boilers HRSG.

[0016] The first waste heat recovery boiler HRSG1 is equipped with a first high-pressure steam generator SGHP1 that generates high-pressure steam and a first intermediate-pressure steam generator SGIP1 that generates intermediate-pressure steam, using the waste heat from the first gas turbine GT1. The second waste heat recovery boiler HRSG2 is equipped with a second high-pressure steam generator SGHP2 that generates high-pressure steam and a second intermediate-pressure steam generator SGIP2 that generates intermediate-pressure steam, using the waste heat from the second gas turbine GT2.

[0017] The steam turbine ST is a so-called high-pressure / intermediate-pressure integrated steam turbine, having a configuration in which a high-pressure turbine HP and an intermediate-pressure turbine IP are connected. The high-pressure turbine HP can be driven by high-pressure steam from the first high-pressure steam generator SGHP1 and the second high-pressure steam generator SGHP2, and the intermediate-pressure turbine IP can be driven by intermediate-pressure steam from the first intermediate-pressure steam generator SGIP1 and the second intermediate-pressure steam generator SGIP2. The steam turbine ST is provided with a high-pressure steam supply unit 4 that supplies high-pressure steam to the high-pressure turbine HP, and an intermediate-pressure steam supply unit 6 that supplies intermediate-pressure steam to the intermediate-pressure turbine IP. The high-pressure steam supply unit 4 and the intermediate-pressure steam supply unit 6 are provided at different axial positions of the steam turbine ST, respectively, so that the thrust balance of the steam turbine ST can be suitably adjusted.

[0018] The first high-pressure steam generator SGHP1 and the second high-pressure steam generator SGHP2 constitute the high-pressure steam supply system SSHP to the high-pressure turbine HP. In the high-pressure steam supply system SSHP, the high-pressure steam generated by the first high-pressure steam generator SGHP1 and the second high-pressure steam generator SGHP2 merges through the first passage P1HP and the second passage P2HP, which are connected to the outlet sides of the first high-pressure steam generator SGHP1 and the second high-pressure steam generator SGHP2, and is further supplied to the steam turbine ST via the third passage P3HP. The third passage P3HP connects the merging point 2HP of the first passage P1HP and the second passage P2HP to the high-pressure steam supply section 4 of the steam turbine ST.

[0019] The first passage P1HP branches off into a bypass passage PbHP1. Upstream of the branching point between the first passage P1HP and the bypass passage PbHP1, a valve VmHP1 is provided. Valve VmHP1 is a control valve whose opening degree can be controlled based on a control signal from the control device 100 described later, and the flow rate of high-pressure steam in the first passage P1HP can be adjusted by controlling its opening degree. Furthermore, a shut-off valve, valve VnHP1, is provided downstream of the branching point between the first passage P1HP and the bypass passage PbHP1, and a valve VbHP1 is provided in the bypass passage PbHP1. Valves VnHP1 and VbHP1 are control valves whose opening degree can be controlled based on a control signal from the control device 100 described later. By controlling the opening degree of valve VnHP1, the high-pressure steam from the first high-pressure steam generator SGHP1 can be shut off, and by controlling the opening degree of valve VbHP1, the flow rate of high-pressure steam bypassed from the first passage P1HP to the bypass passage PbHP1 can be adjusted.

[0020] The second passage P2HP branches off into a bypass passage PbHP2. Upstream of the branching point between the second passage P2HP and the bypass passage PbHP2, a valve VmHP2 is provided. Valve VmHP2 is a control valve whose opening degree can be controlled based on a control signal from the control device 100 described later, and the flow rate of high-pressure steam in the second passage P2HP can be adjusted by controlling its opening degree. Furthermore, a shut-off valve, valve VnHP2, is provided downstream of the branching point between the second passage P2HP and the bypass passage PbHP2, and a valve VbHP2 is provided in the bypass passage PbHP2. Valves VnHP2 and VbHP2 are control valves whose opening degree can be controlled based on a control signal from the control device 100 described later. The opening degree of valve VnHP2 can shut off the high-pressure steam from the second high-pressure steam generator SGHP2, and the opening degree of valve VbHP2 can adjust the flow rate of high-pressure steam bypassed from the second passage P2HP to the bypass passage PbHP2.

[0021] Furthermore, check valves are not provided in the first passage P1HP1 and the second passage P2HP. This reduces pressure loss and improves plant performance compared to when check valves are provided in the first passage P1HP and the second passage P2HP.

[0022] In a high-pressure steam supply system SSHP with this configuration, high-pressure steam can be supplied to the high-pressure turbine HP. Valves VhHP1 and VhHP2 are provided in series near the high-pressure steam supply section 4 connected to the high-pressure turbine HP in the third passage P3HP. Valves VhHP1 and VhHP2 are control valves whose opening degree can be controlled based on a control signal from the control device 100 described later, and by controlling their opening degrees, the amount of high-pressure steam supplied to the high-pressure turbine HP can be adjusted.

[0023] Steam that has finished its work in the high-pressure turbine HP can be supplied as intermediate-pressure steam to the intermediate-pressure steam supply system SSIP (described later) via the steam discharge line 10HP. The steam discharge line 10HP branches into a first steam discharge branch line 10HP1 and a second steam discharge branch line 10HP2. The first steam discharge branch line 10HP1 and the second steam discharge branch line 10HP2 are connected to the first passage P1IP and the second passage P2IP of the intermediate-pressure steam supply system SSIP (described later), respectively. A first circulation valve, valve Vc1, is provided upstream of the junction with the bypass passage PbHP1 in the first steam discharge branch line 10HP1, and a second circulation valve, valve Vc2, is provided upstream of the junction with the bypass passage PbHP2 in the second steam discharge branch line 10HP2. Valves Vc1 and Vc2 are control valves whose opening degree can be controlled based on a control signal from the control device 100 described later. By controlling their opening degrees, the amount of steam discharged from the high-pressure turbine HP supplied to the first passage P1IP and the second passage P2IP of the intermediate-pressure steam supply system SSIP can be adjusted, respectively.

[0024] Furthermore, a discharge line 10HP3 branches off from the high-pressure steam discharge line HP, making it possible to guide the steam discharged from the high-pressure turbine HP to a condenser (not shown) via the discharge line 10HP3. A valve Vc3 is provided in the discharge line 10HP3. Valve Vc3 is also a control valve whose opening degree can be controlled based on a control signal from the control device 100 described later, and by controlling its opening degree, the amount of steam discharged from the high-pressure turbine HP introduced into the condenser can be adjusted.

[0025] The first intermediate-pressure steam generator SGIP1 and the second intermediate-pressure steam generator SGIP2 constitute the intermediate-pressure steam supply system SSIP to the intermediate-pressure turbine IP. In the intermediate-pressure steam supply system SSIP, the intermediate-pressure steam generated by the first intermediate-pressure steam generator SGIP1 and the second intermediate-pressure steam generator SGIP2 merge via the first passage P1IP and the second passage P2IP, which are connected to the outlet sides of the first intermediate-pressure steam generator SGIP1 and the second intermediate-pressure steam generator SGIP2, and is further supplied to the intermediate-pressure turbine IP via the third passage P3IP. The third passage P3IP connects the merging point 2IP of the first passage P1IP and the second passage P2IP to the intermediate-pressure steam supply section 6 of the steam turbine ST.

[0026] The steam discharge branch line 10HP1 is connected to the first passage P1IP. This allows the first passage P1IP to be supplied with intermediate-pressure steam that has finished working in the high-pressure turbine HP, in addition to the intermediate-pressure steam generated by the first intermediate-pressure steam generator SGIP1. A valve VkIP1 is provided upstream of the confluence point with the steam discharge branch line 10HP1 in the first passage P1IP. Valve VkIP1 is a control valve whose opening degree can be controlled based on a control signal from the control device 100 described later, and it is possible to adjust the amount of intermediate-pressure steam supplied from the first intermediate-pressure steam generator SGIP1.

[0027] Furthermore, a bypass passage PbIP1 branches off from the first passage P1IP downstream of the point where it merges with the steam discharge branch line 10HP1. The bypass passage PbIP1 is connected to a condenser (not shown). A valve VbIP1 is provided in the bypass passage PbIP1, and a shut-off valve VnIP1 is provided downstream of the point where it branches off from the bypass passage PbIP1 in the first passage P1IP. Valves VbIP1 and VnIP1 are control valves whose opening degree can be controlled based on a control signal from the control device 100 described later. By controlling the opening degree of valve VbIP1, it is possible to adjust the balance between the amount of intermediate-pressure steam supplied to the condenser and the amount of intermediate-pressure steam supplied to the intermediate-pressure turbine IP via the third passage P3IP, and by controlling the opening degree of valve VnIP1, it is possible to shut off the supply of intermediate-pressure steam via the first passage P1IP.

[0028] Furthermore, a valve VmIP1 is provided in the first passage P1IP downstream of the confluence with the steam discharge branch line 10HP1 and upstream of the branching point with the bypass passage PbIP1. Valve VmIP1 is also a control valve whose opening degree can be controlled based on a control signal from the control device 100 described later, and the flow rate of medium-pressure steam in the first passage P1IP can be adjusted by controlling its opening degree.

[0029] The steam discharge branch line 10HP2 is connected to the second passage P2IP. This allows the second passage P2IP to be supplied with intermediate-pressure steam, including not only the intermediate-pressure steam generated by the second intermediate-pressure steam generator SGIP2, but also the steam that has finished working in the high-pressure turbine HP. A valve VkIP2 is provided upstream of the confluence point with the steam discharge branch line 10HP2 in the second passage P2IP. Valve VkIP2 is a control valve whose opening degree can be controlled based on a control signal from the control device 100 described later, and it is possible to adjust the amount of intermediate-pressure steam supplied from the second intermediate-pressure steam generator SGIP2.

[0030] Furthermore, a bypass passage PbIP2 branches off from the second passage P2IP downstream of the point where it merges with the steam discharge branch line 10HP2. The bypass passage PbIP2 is connected to a condenser (not shown). A valve VbIP2 is provided in the bypass passage PbIP2, and a shut-off valve VnIP2 is provided downstream of the point where it branches off from the bypass passage PbIP2 in the second passage P2IP. Valves VbIP2 and VnIP2 are control valves whose opening degree can be controlled based on a control signal from the control device 100 described later. The opening degree control of valve VbIP2 makes it possible to adjust the balance between the amount of intermediate-pressure steam supplied to the condenser and the amount of intermediate-pressure steam supplied to the intermediate-pressure turbine IP via the third passage P3IP, and the opening degree control of valve VnIP2 makes it possible to shut off the supply of intermediate-pressure steam via the second passage P2IP.

[0031] Furthermore, a valve VmIP2 is provided in the second passage P2IP downstream of the junction with the steam discharge branch line 10HP2 and upstream of the branching point with the bypass passage PbIP2. Valve VmIP2 is also a control valve whose opening degree can be controlled based on a control signal from the control device 100 described later, and the flow rate of medium-pressure steam in the second passage P2IP can be adjusted by controlling its opening degree.

[0032] In this type of intermediate-pressure steam supply system SSIP, intermediate-pressure steam can be supplied to the intermediate-pressure turbine IP of the steam turbine ST. Valves VhIP1 and VhIP2 are installed in series near the intermediate-pressure steam supply section 6 connected to the intermediate-pressure turbine IP in the third passage P3HP. Valves VhIP1 and VhIP2 are control valves whose opening degree can be controlled based on a control signal from the control device 100 described later, and by controlling their opening degrees, the amount of intermediate-pressure steam supplied to the intermediate-pressure turbine IP can be adjusted. Furthermore, the steam that has finished its work in the intermediate-pressure turbine IP is supplied to a low-pressure (LP) system (not shown) via the steam discharge line 10IP.

[0033] Furthermore, in the steam turbine ST, the high-pressure steam supply section 4 of the high-pressure turbine HP, which receives high-pressure steam from the high-pressure steam supply system SSHP, and the intermediate-pressure steam supply section 6 of the intermediate-pressure turbine IP, which receives intermediate-pressure steam from the intermediate-pressure steam supply system SSIP, are each configured to allow for suitable adjustment of the thrust balance. As mentioned above, valves VhHP1 and VhHP2 are provided in the third passage P3HP near the high-pressure steam supply section 4, and valves VhIP1 and VhIP2 are provided in the third passage P3IP near the intermediate-pressure steam supply section 6, and it is possible to adjust to an appropriate thrust balance by adjusting the opening degree of each of these valves.

[0034] Furthermore, in the combined cycle power plant 1 having the above configuration, various sensors are provided to detect the operating state. Specifically, the high-pressure steam supply system SSHP includes a first pressure sensor PT1 located downstream (or upstream) of the branching point between bypass passages PbHP1 and PbHP2 in the first passage P1HP and the second passage P2HP, and a second pressure sensor PT2 located in the third passage P3HP. Similarly, the medium-pressure steam supply system SSIP also includes a first pressure sensor PT1 located downstream (or upstream) of the branching point between bypass passages PbIP1 and PbIP2 in the first passage P1IP and the second passage P2IP, and a second pressure sensor PT2 located in the third passage P3IP. The detected values ​​from these various sensors are transmitted as electrical signals to the control device 100 described later and can be used.

[0035] In the combined cycle power plant 1 having the above configuration, during rated operation, high-pressure steam from the first high-pressure steam generator SGHP1 and the second high-pressure steam generator SGHP2 is supplied to the high-pressure turbine HP, and intermediate-pressure steam from the first intermediate-pressure steam generator SGIP1 and the second intermediate-pressure steam generator SGIP2 is supplied to the intermediate-pressure turbine IP. At this time, the open / closed state of each valve in the combined cycle power plant 1 is as shown in Figure 2, for example.

[0036] Specifically, when valves VmHP1, VnHP1, VmHP2, VnHP2, VhHP1, and VhHP2 are fully open, high-pressure steam is supplied to the high-pressure turbine HP from both the first high-pressure steam generator SGHP1 and the second high-pressure steam generator SGHP2. At this time, valves VbHP1 and VbHP2 are fully closed. Also, when valves Vc1 and Vc2 are fully open, all the steam discharged from the high-pressure turbine HP is supplied as intermediate-pressure steam to the intermediate-pressure steam supply system SSIP. At this time, valve Vc3 is fully closed. Furthermore, when valves VkIP1, VmIP1, VnIP1, VkIP2, VmIP2, VnIP2, VhIP1, and VhIP2 are fully open, intermediate-pressure steam is supplied to the intermediate-pressure turbine IP from both the first intermediate-pressure steam generator SGIP1 and the second intermediate-pressure steam generator SGIP2. At this time, valves VbIP1 and VbIP2 are fully closed.

[0037] On the other hand, if the required load for the combined cycle power plant 1 decreases, the components associated with the gas turbine GT scheduled to be shut down are disconnected from the steam supply system to the steam turbine ST in order to shut down one of the two gas turbines GT. For example, if the first gas turbine GT1 is to be disconnected, the open / closed state of each valve in the combined cycle power plant 1 after disconnection will be as shown in Figure 3, for example.

[0038] Specifically, compared to the case in Figure 2, when valves VnHP1 and VnIP1 are switched to the closed state, the first high-pressure steam generator SGHP1 and the first intermediate-pressure steam generator SGIP1, which correspond to the first gas turbine GT1, are disconnected. At this time, the opening degree of valves VbHP1 and VbIP1 is controlled as described later. Also, when valve Vc1 is switched to the closed state, the steam discharged from the high-pressure turbine HP is cut off from the first intermediate-pressure steam generator SGIP1, which is scheduled to be shut down.

[0039] Next, a control device 100 for controlling the combined cycle power plant 1 having the above configuration will be described. The control device 100 consists of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions are stored in the storage medium in the form of a program, for example, and the CPU reads this program into the RAM and executes information processing and calculations to realize various functions. The program may be pre-installed in the ROM or other storage medium, provided in a state where it is stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memory, etc.

[0040] Figure 4 is a block diagram showing a control device 100 of a combined cycle power plant 1 according to one embodiment. The control device 100 includes a disconnection condition determination unit 102, a detection value acquisition unit 104, a shut-off valve control unit 106, a bypass steam pressure setting value calculation unit 108, and a bypass valve control unit 110.

[0041] The disconnection condition determination unit 102 is configured to determine whether the conditions for performing a disconnection operation from the steam supply system are met for some of the aforementioned steam generators (SGHP1, SGHP2, SGIP1, SGIP2) provided in the combined cycle power plant 1. For example, when the number of operating steam generators SG is variably controlled according to the required load for the combined cycle power plant 1, the required load for the combined cycle power plant 1 is acquired, and the determination is made by comparing the required load with a reference load set in accordance with the number of operating steam generators SG. For example, as described above with reference to Figures 2 and 3, all steam generators are operated at rated load, but when the required load decreases and falls below the reference value, disconnection control is performed to stop the first high-pressure steam generator SGHP1 and the intermediate-pressure steam generator SGIP1 corresponding to the first gas turbine GT1 in order to suppress unnecessary energy consumption.

[0042] The detection value acquisition unit 104 is configured to acquire the detection values ​​of each of the aforementioned sensors installed in the combined cycle power plant 1.

[0043] The shut-off valve control unit 106 is configured to control the shut-off valves (valves VnHP1, VnHP2, VnIP1, VnIP2) corresponding to each steam generator SG in the combined cycle power plant 1. The specific control details by the shut-off valve control unit 106 will be described later, but in the example described above with reference to Figures 2 and 3, at the disconnection timing, the second shut-off valves VnHP2 and VnIP2 corresponding to the second high-pressure steam generator SGHP2 and the second intermediate-pressure steam generator SGIP2, which are not to be disconnected, remain fully open, while the first shut-off valves VnHP1 and VnIP1 corresponding to the first high-pressure steam generator SGHP1 and the first intermediate-pressure steam generator SGIP1, which are to be disconnected, are controlled to close from a fully open state.

[0044] The bypass steam pressure setting value calculation unit 108 is configured to calculate the setting value of the steam pressure in the bypass passages PbHP1, PbHP2, PbIP1, and PbIP2 (hereinafter referred to as "bypass steam pressure setting value PSV" as appropriate), and the bypass valve control unit 110 is configured to control the bypass valves VbHP1, VbHP2, VbIP1, and VbIP2 so that the steam pressure in the bypass passages PbHP1, PbHP2, PbIP1, and PbIP2 becomes the bypass steam pressure setting value PSV calculated by the bypass steam pressure setting value calculation unit 108, respectively.

[0045] Here, Figure 5 is a block diagram showing the internal configuration of the bypass steam pressure setting value calculation unit 108 in Figure 4. The bypass steam pressure setting value calculation unit 108 includes a first passage pressure acquisition unit 112, a second passage pressure acquisition unit 114, a calculation unit 116, a change rate limiting unit 118, and an output switching unit 120.

[0046] The first passage pressure acquisition unit 112 is configured to acquire the pressure in the first passage corresponding to each steam generator SG. This pressure can be acquired based on the detection value of the first pressure sensor PT1 set in each first passage P1HP and P1IP.

[0047] The third passage pressure acquisition unit 114 is configured to acquire the steam pressure (main pipe pressure) in the third passages P3HP and P3IP of the high-pressure steam supply system SSHP and the medium-pressure steam supply system SSIP. This pressure can be acquired based on the detection values ​​of the second pressure sensors PT2 installed in the third passages P3HP and P3IP, respectively.

[0048] The calculation unit 116 is configured to calculate the bypass steam pressure setpoint PSV based on the pressure difference ΔPT between the first passage pressure acquired by the first passage pressure acquisition unit 112 and the third passage pressure acquired by the third passage pressure acquisition unit 114. For example, the calculation unit 116 has a function that defines the relationship between the pressure difference ΔPT and the bypass steam pressure setpoint PSV, and calculates the corresponding bypass steam pressure setpoint PSV by inputting the pressure difference ΔPT to this function.

[0049] The rate of change limiting unit 118 is configured to limit the rate of change of the bypass steam pressure setpoint PSV calculated by the calculation unit 116. For example, if the bypass steam pressure setpoint PSV calculated by the calculation unit 116 exhibits rapid behavior, it is limited to a predetermined rate of change.

[0050] The output switching unit 120 is configured to switch the output of the bypass steam pressure setting value calculation unit 108 based on the operating state of the combined cycle power plant 1. In this embodiment, the output switching unit 120 is configured to switch the output of the bypass steam pressure setting value calculation unit 108 according to (i) before the disconnection operation, (ii) during the disconnection operation, and (iii) after the disconnection operation. Specifically, as will be described later with reference to Figure 7, (i) before the disconnection operation, the output switching unit 120 is switched to output a sufficiently large standby value (fixed value) as the bypass steam pressure setting value PSV. Also, (ii) during the disconnection operation, the output switching unit 120 is switched to output the calculation result of the calculation unit 116 (or the result after the change rate has been limited if it has been limited by the change rate limiting unit 118) as the bypass steam pressure setting value PSV. Also, (iii) after the disconnection operation, the output switching unit 120 is switched to output a preset minimum setting value as the bypass steam pressure setting value PSV.

[0051] (Control method) Next, a control method for the combined cycle power plant 1 implemented by the control device 100 having the above configuration will be described. Figure 6 is a flowchart showing a control method for the combined cycle power plant 1 according to one embodiment, and Figure 7 is a time chart showing the changes in various indicators of the combined cycle power plant 1 corresponding to the control method in Figure 6.

[0052] In the following explanation, we will use the example of selecting the first steam generator SGHP1 and the first steam generator SGIP1 on the first gas turbine GT1 side as the targets for disconnection. However, in the combined cycle power plant 1, the steam generators SG to be disconnected can be arbitrarily selected.

[0053] First, the disconnection condition determination unit 102 acquires the required load for the combined cycle power plant 1 (step S1) and determines whether the disconnection condition is met (step S2). The disconnection condition is a condition for determining whether a disconnection operation from the steam system is necessary for any of the multiple steam generators SG provided in the combined cycle power plant 1. In this embodiment, with reference to Figure 2, in the combined cycle power plant 1 which is normally operating at the rated load described above, the required load acquired in step S1 decreases to below a preset reference value, and it is determined whether or not disconnection of the first high-pressure steam generator SGHP1 and the first intermediate-pressure steam generator SGIP1 corresponding to the first gas turbine GT1 is necessary.

[0054] If the disconnection condition is met (step S2: YES), the shut-off valve control unit 106 controls the valves VnHP1 and VnIP1, which are the first shut-off valves corresponding to the first high-pressure steam generator SGHP1 and the first intermediate-pressure steam generator SGIP1 that are to be disconnected, to perform a closing operation (step S3). Figure 7 shows that at time t1, the valves VnHP1 and VnIP1, which are the shut-off valves that were in a fully open state, begin to close while the output of the first gas turbine GT1 corresponding to the first high-pressure steam generator SGHP1 and the first intermediate-pressure steam generator SGIP1 that are to be disconnected is maintained at a constant level. At this time, the valves VnHP2 and VnIP2, which are the second shut-off valves corresponding to the second high-pressure steam generator SGHP2 and the second intermediate-pressure steam generator SGIP2 that are not to be disconnected, remain in a fully open state.

[0055] Furthermore, at time t1, which is the disconnection timing, valves VnHP1 and VnIP1 begin to decrease their opening degree from the fully open state (100% opening) based on the fully open OFF signal received from the shut-off valve control unit 106. The rate at which the opening degree of valves VnHP1 and VnIP1 decreases is limited by a preset rate of change, and valves VnHP1 and VnIP1, which are in the fully open state at time t1, require a predetermined amount of time to reach the fully closed state (i.e., until the closing operation is completed) at times t2-1 and t2-2, respectively.

[0056] Next, the bypass valve control unit 110 starts controlling the opening degree of the bypass valves VbHP1 and VbIP1 at time t1 (the disconnection timing in step S3, when the second shut-off valves VnHP2 and VnIP2 remain fully open and the first shut-off valves VnHP1 and VnIP1 begin closing from their fully open state) (step S4). This control of the opening degree of valves VbHP1 and VbIP1 is performed so that the steam pressure in the bypass passages PbHP1 and PbIP1 becomes the bypass steam pressure setpoint PSV calculated by the bypass steam pressure setpoint calculation unit 108 described above.

[0057] Before time t1, the bypass steam pressure setting value calculation unit 108 outputs a sufficiently large standby value (fixed value) as the bypass steam pressure setting value PSV via the output switching unit 120. Therefore, the bypass valve control unit 110 controls the bypass valves, valves VbHP and VbIP, to be in a fully closed state.

[0058] On the other hand, from time t1 onward, the bypass steam pressure setting value calculation unit 108 outputs the calculation result of the calculation unit 116 (the bypass steam pressure setting value PSV calculated based on the pressure difference ΔPT between the first passage pressure acquired by the first passage pressure acquisition unit 112 and the third passage pressure acquired by the third passage pressure acquisition unit 114) as the bypass steam pressure setting value PSV via the output switching unit 120. As a result, the bypass valve control unit 110 starts the opening operation of the bypass valves VbHP1 and VbIP1 from their fully closed state.

[0059] The opening degree control of valves VbHP1 and VbIP1 is performed so that the steam pressure upstream of valves VnHP1 and VnIP1 in the first passages P1HP and P1IP, which correspond to the first high-pressure steam generator SGHP1 and the first intermediate-pressure steam generator SGIP1 that are to be disconnected, is equal to the steam pressure in the third passages P3HP and P3IP. As a result, the opening degree control of valves VbHP1 and VbIP1 effectively suppresses steam inflow (backflow) from the second passages P2HP and P2IP and the third passages P3HP and P3IP to the first high-pressure steam generator SGHP1 and the first intermediate-pressure steam generator SGIP1 that are to be disconnected.

[0060] Furthermore, in Figure 7, the valve VbHP1, which is a bypass valve on the SSHP side of the high-pressure steam supply system, gradually increases its opening degree from time t1 to the minimum opening degree VbHP1min according to a preset rate of change, and then remains at the minimum opening degree VbHP1min for a while. This is because immediately after time t1, the pressure difference ΔPT between the steam pressure of the first passage P1HP and the steam pressure of the third passage P3HP is large, resulting in a relatively large bypass steam pressure setpoint PSV. Therefore, although the bypass valve VbHP starts opening from a fully closed state in step S4, the control works in the direction of decreasing the opening degree due to the large bypass steam pressure setpoint PSV, and as a result, the opening degree of valve VbHP is stuck at the minimum opening degree VbHP1min specified in the specifications. Furthermore, as sufficient time elapses from time t1, the pressure difference ΔPT between the steam pressure of the first passage P1HP and the steam pressure of the third passage P3HP decreases, and the bypass steam pressure setpoint PSV also decreases, resulting in the valve VbHP opening degree increasing from the minimum opening degree VbHP1min.

[0061] Furthermore, the valve VbIP1, which is a bypass valve on the SSIP side of the intermediate-pressure steam supply system, gradually increases its opening degree from time t1. Near time t1, the pressure difference ΔPT between the steam pressure of the first passage P1IP and the steam pressure of the third passage P3IP is large, so the opening rate of valve VbIP1 is limited to a preset rate of change, and the opening rate of valve VbIP1 remains constant. After a sufficient amount of time has elapsed from time t1, as the pressure difference ΔPT between the steam pressure of the first passage P1IP and the steam pressure of the third passage P3IP decreases, the valve shows an opening degree change corresponding to the pressure difference ΔPT.

[0062] Furthermore, valve VbIP1, which is the bypass valve on the SSIP side of the medium-pressure steam supply system, does not exhibit the behavior of sticking to the minimum opening degree like valve VbHP1, which is the bypass valve on the SSHP side of the high-pressure steam supply system. However, depending on the specifications, it may be designed to exhibit the behavior of sticking to the minimum opening degree.

[0063] In this manner, when disconnecting the first high-pressure steam generator SGHP1 and the first intermediate-pressure steam generator SGIP1, the second shut-off valves VnHP2 and VnIP2, which are not to be disconnected, are in a fully open state. At the disconnection timing (time t1), when the first shut-off valves VnHP1 and VnIP1, which are to be disconnected, begin closing from their fully open state, the bypass valves VbHP1 and VbIP1 begin opening from their fully closed state. As a result, compared to the case where the opening operation of the bypass valves VbHP1 and VbIP1 begins from their fully closed state after this timing, even if the pressure on the third passage P3HP and P3IP side rises between times t2-1 and t2-2, when the valves VnHP1 and VnIP1 become fully closed, the opening operation of valves VbHP1 and VbIP1 will not be delayed. As a result, the responsiveness of valve VbHP1 and VbIP1 opening control to pressure fluctuations on the third passage P3HP and P3IP is improved, and the operating state of the combined cycle power plant 1 can be stably maintained before and after disconnection.

[0064] Furthermore, by improving the responsiveness of the opening control of the bypass valves VbHP1 and VbIP1, the inflow (backflow) of steam from the remaining second high-pressure steam generator SGHP2 and second intermediate-pressure steam generator SGIP2 to the disconnected first high-pressure steam generator SGHP1 and first intermediate-pressure steam generator SGIP1 can also be suppressed. As a result, even when some of the steam generators SG are disconnected, the impact on the steam turbine ST, which is the steam supply destination, can be minimized, and the disruption of the thrust balance can be effectively prevented.

[0065] Next, it is determined whether the first shut-off valves, valves VnHP1 and VnIP1, which began closing in step S3, have reached a fully closed state (step S5). If valves VnHP1 and VnIP1 are fully closed (step S5: YES), the bypass steam pressure setting value PSV for the bypass valves VbHP1 and VbIP1 is switched to the minimum setting value preset by the output switching unit 120 (step S6). As a result, the series of disconnection operations for the first high-pressure steam generator SGHP1 and the first medium-pressure steam generator SGIP1 in the high-pressure steam supply system SSHP are completed.

[0066] As shown in Figure 7, in this embodiment, in step S3, the first shut-off valves, valves VnHP1 and VnIP1, are controlled to simultaneously begin closing from a fully open state at time t1. When disconnecting multiple steam generators SG in this way, simultaneously starting the closing operation of the corresponding shut-off valves, valves VnHP1 and VnIP1, minimizes the impact of disconnection on the steam turbine ST and effectively prevents the thrust balance from being disrupted.

[0067] Furthermore, in Figure 7, at time t1, in step S3, in addition to the first shut-off valves VnHP1 and VnIP1, valve Vc1 is also controlled to start closing simultaneously. As a result, the steam discharged from the high-pressure turbine HP is shut off to the first intermediate-pressure steam generator SGIP1, which is to be disconnected.

[0068] Furthermore, valve VnIP1, which is the first shut-off valve corresponding to the first intermediate-pressure steam generator SGIP1, is controlled to reach a fully closed state earlier than valve VnHP1, which is the first shut-off valve corresponding to the first high-pressure steam generator SGHP1. As a result, pressure fluctuations that occur when valve VnHP1, the first shut-off valve corresponding to the first high-pressure steam generator SGHP1, closes through the bypass valve VbHP1 on the high-pressure steam side may propagate to the steam system of the first intermediate-pressure steam generator SGIP1 located downstream. However, by closing valve VnIP1, the first shut-off valve corresponding to the first intermediate-pressure steam generator SGIP1, before valve VnHP1, the impact of such pressure fluctuations on the steam turbine ST can be suppressed. Furthermore, valve Vc, along with valve VnIP1, which is the first shut-off valve corresponding to the first intermediate-pressure steam generator SGIP1, is controlled to reach a fully closed state earlier than valve VnHP1, which is the first shut-off valve corresponding to the first high-pressure steam generator SGHP1.

[0069] As described above, according to the above embodiment, it is possible to provide a control device, control method, and control program for a steam power plant that can disconnect some steam generators while maintaining a stable operating state.

[0070] Furthermore, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, without departing from the spirit of this disclosure, and the above-described embodiments may also be combined as appropriate.

[0071] The contents described in each of the above embodiments can be understood, for example, as follows:

[0072] (1) A control device for a steam power plant according to one embodiment is: The generator is connected to a steam turbine (SG) and is equipped with a high-pressure steam supply system (SSHP) and an intermediate-pressure steam supply system (SSIP) capable of supplying high-pressure steam and intermediate-pressure steam, respectively. At least one of the high-pressure steam supply system or the medium-pressure steam supply system is First steam generators (SGHP1, SGIP1), The first passage (P1HP, P1IP) through which the steam generated in the first steam generator flows, The first shut-off valves (VnHP1, VnIP1) provided in the first passage, The second steam generators (SGHP2, SGIP2), The second passage (P2HP, P2IP) through which the steam generated in the second steam generator flows, The second shut-off valves (VnHP2, VnIP2) provided in the second passage, A third passage (P3HP, P3IP) connects the junction of the first passage and the second passage to the steam turbine, The bypass passages (PbHP1, PbIP1) branch off from the first passage upstream of the first shut-off valve, Bypass valves (VbHP1, VbIP1) provided in the bypass passage, A control device (100) for a combined cycle power plant (1) comprising, At the disconnection start timing (t1) when the second shut-off valve is fully open and the first shut-off valve starts closing from its fully open state, the bypass valve starts opening from its fully closed state.

[0073] According to the embodiment of (1) above, when the first steam generator is disconnected from the steam supply system, the bypass valve starts opening from its fully closed state at the same disconnection timing when the second shut-off valve is fully open and the first shut-off valve starts closing from its fully open state. As a result, compared to the case where the bypass valve starts opening from its fully closed state after this timing, even if the pressure on the third passage side rises before the first shut-off valve is fully closed, the opening of the bypass valve is not delayed, and the outlet pressure of the first steam generator (pressure in the first passage) does not rise. As a result, the responsiveness of the bypass valve opening control to pressure fluctuations on the third passage side is improved, and the operating state of the combined cycle power plant can be stably maintained before and after disconnection. In addition, with the improved responsiveness of the bypass valve opening control, the remaining steam inflow (backflow) from the second steam generator side is also suppressed. As a result, even when the first steam generator is disconnected, the impact on the steam turbine, which is the steam supply destination, is minimized, and the disruption of the thrust balance can be effectively prevented.

[0074] (2) In other embodiments, in the embodiment of (1) above, A bypass steam pressure calculation unit (108) calculates a pressure set value for the bypass steam downstream of the bypass valve in the bypass passage so that, after the aforementioned disconnection timing, the steam pressure upstream of the first shut-off valve in the first passage becomes the steam pressure in the third passage. A bypass valve control unit (110) controls the opening degree of the bypass valve so that the bypass steam pressure becomes the pressure set value, It is equipped with.

[0075] According to the embodiment described in (2) above, the opening degree of the bypass valve is controlled so that the steam pressure upstream of the first shut-off valve in the first passage corresponding to the first steam generator to be disconnected becomes equal to the steam pressure in the third passage. This effectively suppresses the inflow (backflow) of steam from the third passage to the steam generator to be disconnected by controlling the opening degree of the bypass valve.

[0076] (3) In other embodiments, in the embodiment of (2) above, The system includes a rate of change limiting unit (118) for limiting the rate of change of the pressure setpoint.

[0077] According to the embodiment of (3) above, by limiting the rate of change of the bypass steam pressure setpoint used for controlling the opening of the bypass valve to be below a predetermined value, it is possible to suppress rapid changes in the bypass valve even when the steam pressure in the third passage fluctuates greatly, and to maintain a stable operating state.

[0078] (4) In other embodiments, in the embodiment of (2) or (3) above, The bypass valve control unit controls the bypass valve so as to gradually increase the opening degree of the bypass valve, which is in a fully closed state, from the aforementioned timing to a preset minimum opening degree.

[0079] According to the embodiment of (4) above, when the first steam generator is disconnected from the steam supply system, the opening degree of the bypass valve is controlled to gradually increase to the minimum opening degree at the timing when the first shut-off valve corresponding to the first steam generator starts closing from a fully open state.

[0080] (5) In other embodiments, in the embodiment of (4) above, The bypass valve control unit maintains the opening of the bypass valve at the minimum opening for a predetermined period of time after the opening of the bypass valve reaches the minimum opening.

[0081] According to the embodiment of (5) above, when the first steam generator is disconnected from the steam supply system, the opening of the bypass valve is maintained at the minimum opening for a period of time, thereby effectively suppressing steam inflow (backflow) from the third passage side to the disconnected first steam generator.

[0082] (6) In other embodiments, in any one embodiment of (2) to (5) above, The aforementioned pressure setting value is set to a constant standby value before the disconnection timing.

[0083] According to the embodiment of (6) above, in the stage before the bypass valve opening control is started, a standby value is set as the pressure setpoint for the bypass steam used to control the bypass valve opening. By setting the standby value to a sufficiently large value, the bypass valve can be suitably maintained in a fully closed state in the stage before the bypass valve opening control is started. By switching from such a pressure setpoint from the standby value to the result calculated by the bypass steam pressure setpoint calculation unit at the timing when the bypass valve opening control is started, it becomes possible to control the bypass valve opening with high accuracy and responsiveness.

[0084] (7) In other embodiments, in any one embodiment of (1) to (6) above, In both the high-pressure steam supply system and the medium-pressure steam supply system, the second shut-off valve is controlled to start closing from the fully open state of the first shut-off valve simultaneously when the second shut-off valve is fully open.

[0085] According to the embodiment of (7) above, when the first steam generators in the high-pressure steam supply system and the medium-pressure steam supply system are disconnected, the closing operation of the corresponding first shut-off valves is started simultaneously, thereby suppressing the impact on the steam turbine due to the disconnection and effectively preventing the thrust balance from being disrupted.

[0086] (8) In other embodiments, in any one embodiment of (1) to (7) above, The steam discharge line (10 HP) from which the steam that has finished working in the aforementioned steam turbine is discharged, A first steam discharge branch line (10HP1) and a second steam discharge branch line (10HP2) branch off from the steam discharge line and are connected to the first passage and the second passage of the medium-pressure steam supply system, respectively. A first circulation valve (Vc1) and a second circulation valve (Vc2) are provided in the first steam discharge branch line and the second steam discharge branch line, respectively. Furthermore, The first shut-off valves and the first circulation valves in the high-pressure steam supply system and the medium-pressure steam supply system are controlled to simultaneously begin closing from a fully open state.

[0087] According to the embodiment of (8) above, when steam that has finished working in the steam turbine is supplied as intermediate-pressure steam to the intermediate-pressure steam supply system, the first circulation valve on the first steam generator side is closed simultaneously with the first shut-off valve when the first steam generator is disconnected.

[0088] (9) In other embodiments, in any one embodiment of (1) to (8) above, The high-pressure steam and the medium-pressure steam are supplied to different positions in the axial direction of the steam turbine, respectively.

[0089] According to the embodiment of (9) above, in a steam turbine where high-pressure steam and medium-pressure steam are supplied to different positions in the axial direction, the effects of disconnecting the steam generator can be suppressed, and the disruption of the thrust balance can be effectively prevented.

[0090] (10) A control method for a steam power plant according to one embodiment is: The generator is connected to a steam turbine (SG) and is equipped with a high-pressure steam supply system (SSHP) and an intermediate-pressure steam supply system (SSIP) capable of supplying high-pressure steam and intermediate-pressure steam, respectively. At least one of the high-pressure steam supply system or the medium-pressure steam supply system is First steam generators (SGHP1, SGIP1), The first passage (P1HP, P1IP) through which the steam generated in the first steam generator flows, The first shut-off valves (VnHP1, VnIP1) provided in the first passage, The second steam generators (SGHP2, SGIP2), The second passage (P2HP, P2IP) through which the steam generated in the second steam generator flows, The second shut-off valves (VnHP2, VnIP2) provided in the second passage, A third passage (P3HP, P3IP) connects the junction of the first passage and the second passage to the steam turbine, The bypass passages (PbHP1, PbIP1) branch off from the first passage upstream of the first shut-off valve, Bypass valves (VbHP1, VbIP1) provided in the bypass passage, A control method for a combined cycle power plant (1) comprising, At the disconnection start timing (t1), when the second shut-off valve is fully open and the first shut-off valve starts closing from its fully open state, the bypass valve starts opening from its fully closed state.

[0091] According to the embodiment of (10) above, when the first steam generator is disconnected from the steam supply system, the bypass valve starts opening from its fully closed state at the same disconnection timing when the second shut-off valve is fully open and the first shut-off valve starts closing from its fully open state. As a result, compared to the case where the bypass valve starts opening from its fully closed state after this timing, even if the pressure on the third passage side rises before the first shut-off valve is fully closed, the opening of the bypass valve is not delayed, and the outlet pressure of the first steam generator (pressure in the first passage) does not rise. As a result, the responsiveness of the bypass valve opening control to pressure fluctuations on the third passage side is improved, and the operating state of the combined cycle power plant can be stably maintained before and after disconnection. In addition, with the improved responsiveness of the bypass valve opening control, the remaining steam inflow (backflow) from the second steam generator side is also suppressed. As a result, even when the first steam generator is disconnected, the impact on the steam turbine, which is the steam supply destination, is minimized, and the disruption of the thrust balance can be effectively prevented.

[0092] (11) A control program for a steam power plant according to one embodiment is: The generator is connected to a steam turbine (SG) and is equipped with a high-pressure steam supply system (SSHP) and an intermediate-pressure steam supply system (SSIP) capable of supplying high-pressure steam and intermediate-pressure steam, respectively. At least one of the high-pressure steam supply system or the medium-pressure steam supply system is First steam generators (SGHP1, SGIP1), The first passage (P1HP, P1IP) through which the steam generated in the first steam generator flows, The first shut-off valves (VnHP1, VnIP1) provided in the first passage, The second steam generators (SGHP2, SGIP2), The second passage (P2HP, P2IP) through which the steam generated in the second steam generator flows, The second shut-off valves (VnHP2, VnIP2) provided in the second passage, A third passage (P3HP, P3IP) connects the junction of the first passage and the second passage to the steam turbine, The bypass passages (PbHP1, PbIP1) branch off from the first passage upstream of the first shut-off valve, Bypass valves (VbHP1, VbIP1) provided in the bypass passage, A control program for a combined cycle power plant (1) comprising: Using a computer At the disconnection start timing (t1), when the second shut-off valve is fully open and the first shut-off valve starts closing from its fully open state, the bypass valve starts opening from its fully closed state.

[0093] According to the embodiment of (11) above, when the first steam generator is disconnected from the steam supply system, the bypass valve starts opening from its fully closed state at the same disconnection timing when the second shut-off valve is fully open and the first shut-off valve starts closing from its fully open state. As a result, compared to the case where the bypass valve starts opening from its fully closed state after this timing, even if the pressure on the third passage side rises before the first shut-off valve is fully closed, the opening of the bypass valve is not delayed, and the outlet pressure of the first steam generator (pressure in the first passage) does not rise. As a result, the responsiveness of the bypass valve opening control to pressure fluctuations on the third passage side is improved, and the operating state of the combined cycle power plant can be stably maintained before and after disconnection. In addition, with the improved responsiveness of the bypass valve opening control, the remaining steam inflow (backflow) from the second steam generator side is also suppressed. As a result, even when the first steam generator is disconnected, the impact on the steam turbine, which is the steam supply destination, is minimized, and the disruption of the thrust balance can be effectively prevented. [Explanation of symbols]

[0094] 1 Combined cycle power plant 2HP, 2IP junction 4. High-pressure steam supply unit 6. Medium-pressure steam supply unit 10HP, 10IP steam discharge line 10HP1 No. 1 Steam Discharge Branch Line 10HP2 No. 2 Steam Discharge Branch Line 100 Control device 102 Detachment condition determination unit 104 Detected Value Acquisition Unit 106 Shut-off valve control unit 108 Bypass steam pressure set value calculation unit 110 Bypass valve control unit 112 First passage pressure acquisition unit 114 Third passage pressure acquisition unit 116 Arithmetic section 118 Rate of Change Limit Section 120 Output switching section GT1 No. 1 Gas Turbine GT2 No. 2 Gas Turbine P1HP, P1IP First aisle P2HP, P2IP Second aisle P3HP,P3IP 3rd aisle PT1 First pressure sensor PT2 Second Pressure Sensor PbHP1, PbHP2, PbIP1, PbIP2 Bypass Passage VbHP1, VbHP2, VbIP1, VbIP2 valves (bypass valves) VnHP1, VnHP2, VnIP1, VnIP2 valves (shut-off valves) Vc1, Vc2 valves (circulation valves) SG steam generator SGHP1 First High-Pressure Steam Generator SGHP2 No. 2 High-Pressure Steam Generator SGIP1 No. 1 Intermediate Pressure Steam Generator SGIP2 Second Intermediate Pressure Steam Generator SSHP High-Pressure Steam Supply System SSHP Medium Pressure Steam Supply System ST Steam Turbine HP High-Pressure Turbine IP Intermediate Pressure Turbine

Claims

1. The generator is equipped with a high-pressure steam supply system and an intermediate-pressure steam supply system, which are capable of supplying high-pressure steam and intermediate-pressure steam, respectively, to the steam turbine connected to the generator. At least one of the high-pressure steam supply system or the medium-pressure steam supply system is First steam generator and, The first passage through which the steam generated in the first steam generator flows, The second steam generator, The second passage through which the steam generated in the second steam generator flows, A second shut-off valve provided in the second passage, A third passage connecting the confluence of the first passage and the second passage to the steam turbine, A first shut-off valve provided in the first passage, A bypass passage that branches off from the first passage upstream of the first shut-off valve, A bypass valve provided in the bypass passage, A control device for a combined cycle power plant, comprising: A control device for a combined cycle power plant, wherein the second shut-off valve is fully open, and at the disconnection start timing when the first shut-off valve starts closing from its fully open state, the bypass valve starts opening from its fully closed state.

2. A bypass steam pressure calculation unit calculates a pressure set value for the bypass steam downstream of the bypass valve in the bypass passage so that, after the aforementioned disconnection timing, the steam pressure upstream of the first shut-off valve in the first passage becomes the steam pressure in the third passage. A bypass valve control unit controls the opening degree of the bypass valve so that the bypass steam pressure becomes the pressure set value, The control device according to claim 1, comprising:

3. The control device according to claim 2, further comprising a change rate limiting unit for limiting the rate of change of the pressure set value.

4. The control device according to claim 2 or 3, wherein the bypass valve control unit controls the bypass valve so as to gradually increase the opening degree of the bypass valve, which is in a fully closed state, from the timing to a preset minimum opening degree.

5. The control device according to claim 4, wherein the bypass valve control unit maintains the opening degree of the bypass valve at the minimum opening degree for a predetermined period of time after the opening degree of the bypass valve reaches the minimum opening degree.

6. The control device according to claim 2, wherein the pressure setting value is set to a constant standby value before the disconnection timing.

7. The control device according to claim 1 or 2, wherein in each of the high-pressure steam supply system and the medium-pressure steam supply system, the closing operation of the first shut-off valve from the fully open state is simultaneously initiated when the second shut-off valve is fully open.

8. A steam discharge line through which steam that has finished working in the aforementioned steam turbine is discharged, A first steam discharge branch line and a second steam discharge branch line branch off from the steam discharge line and are connected to the first passage and the second passage of the medium-pressure steam supply system, respectively. A first circulation valve and a second circulation valve are provided in the first steam discharge branch line and the second steam discharge branch line, respectively. Furthermore, The control device according to claim 1 or 2, which controls the first shut-off valve and the first circulation valve in the high-pressure steam supply system and the medium-pressure steam supply system to simultaneously start closing operations from a fully open state.

9. The control device according to claim 1 or 2, wherein the high-pressure steam and the medium-pressure steam are supplied to different positions in the axial direction of the steam turbine, respectively.

10. The generator is equipped with a high-pressure steam supply system and an intermediate-pressure steam supply system, which are capable of supplying high-pressure steam and intermediate-pressure steam, respectively, to the steam turbine connected to the generator. At least one of the high-pressure steam supply system or the medium-pressure steam supply system is First steam generator and, The first passage through which the steam generated in the first steam generator flows, A first shut-off valve provided in the first passage, The second steam generator, The second passage through which the steam generated in the second steam generator flows, A second shut-off valve provided in the second passage, A third passage connecting the confluence of the first passage and the second passage to the steam turbine, A bypass passage that branches off from the first passage upstream of the first shut-off valve, A bypass valve provided in the bypass passage, A control method for a combined cycle power plant, A control method for a combined cycle power plant, wherein the second shut-off valve is fully open, and at the disconnection start timing when the first shut-off valve starts closing from its fully open state, the bypass valve starts opening from its fully closed state.

11. The generator is equipped with a high-pressure steam supply system and an intermediate-pressure steam supply system, which are capable of supplying high-pressure steam and intermediate-pressure steam, respectively, to the steam turbine connected to the generator. At least one of the high-pressure steam supply system or the medium-pressure steam supply system is First steam generator and, The first passage through which the steam generated in the first steam generator flows, A first shut-off valve provided in the first passage, The second steam generator, The second passage through which the steam generated in the second steam generator flows, A second shut-off valve provided in the second passage, A third passage connecting the confluence of the first passage and the second passage to the steam turbine, A bypass passage that branches off from the first passage upstream of the first shut-off valve, A bypass valve provided in the bypass passage, A control program for a combined cycle power plant, Using a computer A control program for a combined cycle power plant, which initiates the opening operation of the bypass valve from its fully closed state at the disconnection start timing when the closing operation of the first shut-off valve from its fully open state is initiated while the second shut-off valve is fully open.

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