Method for operating steam turbine power generation plant, storage medium, and steam turbine power generation plant

Abstract

A steam turbine power generation plant according to the present invention comprises: a steam turbine (21) that is connected to a generator (31); a main steam line (501) that is provided upstream of the steam turbine 21; a bypass line (503) that is branched from the main steam line (501), that is provided for causing steam to flow in a manner bypassing the steam turbine (21), and that has a bypass valve (61); and an atmospheric diffusion line (505) that is branched from the main steam line (501), that is provided so as to diffuse steam into the atmosphere, and that has an atmospheric diffusion valve (63), said steam turbine power generation plant including a supplied steam identification step for identifying the supplied steam flow rate in the main steam line (501), a steam turbine operation state determination step for determining whether the steam turbine is in an unsteady operation state, and a degree-of-opening adjustment step for adjusting the degree of opening of the bypass valve (61) and the atmospheric diffusion valve (63) in correspondence with the supplied steam flow rate, when the steam turbine (21, 22) is determined to be in the unsteady operation state.

Description

Steam turbine power plant operation method, storage medium, and steam turbine power plant

[0001] The present invention relates to a technique for continuing stable operation of a steam turbine in response to large changes in steam consumption during unsteady operating conditions of the steam turbine.

[0002] Generally, a steam turbine power plant (hereinafter simply referred to as a "power plant") generates electricity by using steam generated in a boiler to rotate the rotor blades of a steam turbine, which drives a generator connected to the rotor shaft of the rotor blades. During steady-state operation, a flow rate of steam balanced with the consumption of steam by the steam turbine is supplied from the boiler, maintaining a stable operating state.

[0003] On the other hand, when a steam turbine undergoes an emergency shutdown or during unsteady operation in which steam consumption in the steam turbine is significantly reduced, the steam supplied from the boiler becomes surplus. However, it is difficult to immediately shut down the boiler in response to an emergency shutdown of the steam turbine. Furthermore, even if the boiler continues to operate with a reduced steam supply flow rate, it is difficult to continue operation when the boiler's steam supply flow rate is below the lower limit set due to equipment constraints, etc. Therefore, when a turbine undergoes an emergency shutdown or when steam consumption is significantly reduced, it is necessary to take measures to ensure stable operation of the power plant under conditions in which the steam supply flow rate from the boiler is excessive compared to the steam consumption of the equipment.

[0004] Patent Document 1 describes that in a thermal power plant that generates electricity using a steam turbine, the bypass valve in the bypass line of the steam turbine typically opens when the steam turbine starts up or when steam pressure rises. Patent Document 1 also describes that in an AFC (Automatic Frequency Control) response mode, which requires response to relatively rapid frequency fluctuations, opening and closing the turbine bypass valve while adding a positive bias value to the boiler input command value enables load adjustment with higher responsiveness than when controlling the boiler output. However, the above-mentioned load adjustment is performed to fulfill the obligation to maintain the frequency of the power system, and only describes a load adjustment technique under steady-state operating conditions. On the other hand, Patent Document 1 does not describe at all how to respond to excess steam under unsteady operating conditions.

[0005] Furthermore, Patent Document 2 describes a technique for adjusting the output ratio of a combined cycle power generation facility that includes a gas turbine, a gas turbine generator, a heat recovery boiler that generates steam using gas turbine exhaust gas as a heat source, a steam turbine, and a steam turbine generator. Patent Document 2 points out a problem in which if either the gas turbine or the steam turbine reaches its load limit first, the other will enter a partial operation state, and the power generation facility as a whole will not reach its rated output.

[0006] As a method for solving this problem, Patent Document 2 exemplifies a method of providing a bypass system with a bypass valve to bypass the steam supplied to the steam turbine from the steam turbine inlet, and a method of providing an atmosphere relief valve to discharge the steam from the heat recovery steam generator outlet. According to this technique, for example, when the steam turbine reaches its load limit first and the gas turbine is in a partial operation state, the amount of steam flowing into the steam turbine is reduced by directing a portion of the steam toward the bypass system or atmosphere relief valve. As a result, the steam turbine is able to accept steam, and the gas turbine load can be adjusted to increase the amount of steam generated in order to achieve rated output.

[0007] As confirmed above, what is described in D2 is an operation adjustment technology for a steady state operation in which a combined cycle power plant is required to achieve rated output. However, D2 does not describe or suggest what problems may arise during unsteady states in which it is difficult for the combined cycle power plant to maintain rated output, such as when the steam turbine is suddenly stopped or when steam consumption in the steam turbine is significantly reduced, or what methods can be used to solve those problems.

[0008] JP 2022-104052 A JP 2007-92721 A

[0009] The present method for operating a steam turbine power plant has been made against this background, and provides a technique for stably operating a steam turbine power plant in response to the operating state of the steam turbine in an unsteady operating state.

[0010] This method for operating a steam turbine power plant includes: a steam turbine connected to a generator; a main steam line provided upstream of the steam turbine; a bypass line branching from the main steam line to allow at least a portion of the steam in the main steam line to bypass the steam turbine and having a bypass valve with an adjustable opening; and an atmosphere discharge line branching from the main steam line to discharge at least a portion of the steam in the main steam line to the atmosphere and having an atmosphere discharge valve with an adjustable opening, and the method includes the following steps: a supply steam flow rate specifying step for specifying a supply steam flow rate in the main steam line upstream of the bypass line and the atmosphere discharge line; a steam turbine operating state determination step for determining whether the steam turbine is in a predetermined non-steady operating state; and an opening adjustment step for adjusting openings of the bypass valve and the atmosphere discharge valve in accordance with the supply steam flow rate when it is determined in the steam turbine operating state determination step that the steam turbine is in the predetermined non-steady operating state.

[0011] The method for operating a steam turbine power plant may include the following: (a) the steam turbine operating state determination step determines that the steam turbine is in the predetermined unsteady operating state based on any one of a turbine trip signal issued during an emergency shutdown of the steam turbine, a load shedding command signal issued when the load of the generator is shedding, or an on-site islanding operation transition command signal issued when electricity generated by the generator is consumed only within a utility facility where the steam turbine power plant is installed; and (b) the steam turbine operating state determination step determines that the steam turbine is in the predetermined unsteady operating state when the supplied steam flow rate exceeds a required steam flow rate of the steam turbine by a predetermined value or more, or when a rate of decrease of the required steam flow rate of the steam turbine within a predetermined time period exceeds a predetermined value or more. (c) a turbine-row steam line connected to the steam turbine and provided downstream of a branch point of the main steam line with the bypass line and a branch point of the atmosphere release line is provided with a turbine-row valve whose opening is adjustable, and the steam flow rate specifying step specifies the supply steam flow rate based on the opening of the bypass valve, the opening of the atmosphere release valve, and the opening of the turbine-row valve. (d) The steam turbine power plant has a pressure gauge that measures the steam pressure upstream of the steam turbine, and further includes a first pressure control step of adjusting the opening of the bypass valve when the steam pressure upstream of the steam turbine exceeds a first predetermined pressure. (e) The steam turbine power plant has a pressure gauge that measures the steam pressure upstream of the atmosphere release valve, and further includes a second pressure control step of adjusting the opening of the atmosphere release valve when the steam pressure upstream of the atmosphere release valve exceeds a second predetermined pressure.

[0012] (f) the atmosphere release valve is closed when the steam turbine is in a steady operating state, and in the opening adjustment step, the bypass valve is opened prior to the atmosphere release valve, and the opening of the atmosphere release valve is adjusted so that steam exceeding an acceptance constraint downstream of the bypass line is released to the atmosphere. (g) In (f), a water injection line is connected to the bypass line, the water injection line being provided for injecting cooling water to lower the temperature of the steam flowing through the bypass line and having a water injection valve whose opening is adjustable, and the acceptance constraint is determined based on the total flow rate of the steam flowing into the bypass line from the main steam line and the cooling water injected from the water injection line. Furthermore, the opening of the water injection valve is set, when the bypass valve is opened in the opening adjustment step, based on the supply steam flow rate specified in the supply steam flow rate specifying step and the temperature of the main steam, so that cooling water is injected at a flow rate that makes the temperature of the steam flowing through the bypass line downstream of the cooling water injection position equal to or lower than a predetermined temperature constraint. (h) In (f), the downstream end of the bypass line is connected to a condenser, and the acceptance constraint is the amount of steam that can be processed per unit time of the condenser. (i) The downstream side of the bypass line is connected to a boiler that heats steam received through an outlet line of the steam turbine.

[0013] (j) The steam turbine power plant comprises a low-pressure turbine to which low-pressure steam discharged from the steam turbine is supplied via a low-pressure steam line and to which steam discharged from the bypass line is supplied via the low-pressure steam line, and a low-pressure steam bypass line provided to allow at least a portion of the low-pressure steam in the low-pressure steam line to bypass the low-pressure turbine and having a low-pressure bypass valve whose opening is adjustable, and in the steam turbine operating state determination step, it is determined whether the low-pressure turbine is in an unsteady operating state in addition to the steam turbine, and in the opening adjustment step, the opening of the low-pressure steam bypass valve is adjusted in addition to the bypass valve and the atmosphere release valve.

[0014] (k) In (a), when the steam turbine operating state determining step determines that the steam turbine is in the unsteady operating state based on the turbine trip signal, the opening adjustment step adjusts the openings of the bypass valve and the atmosphere release valve to allow the entire amount of steam supplied from the main steam line to flow into at least one of the bypass line and the atmosphere release line. (l) In (a), when the steam turbine operating state determining step determines that the steam turbine is in the unsteady operating state based on the load shedding command signal or the stationary islanding operation transition command signal, the opening adjustment step adjusts the openings of the bypass valve and the atmosphere release valve to allow the surplus amount, obtained by subtracting the flow rate of steam supplied to the steam turbine from the flow rate of steam supplied from the main steam line, to flow into at least one of the bypass line and the atmosphere release line.

[0015] Furthermore, the present invention provides an operating method for a steam turbine power plant comprising: a steam turbine connected to a generator; a main steam line provided upstream of the steam turbine; a bypass line branching from the main steam line for allowing at least a portion of the steam in the main steam line to bypass the steam turbine and having a bypass valve with an adjustable opening; and an atmosphere discharge line branching from the main steam line for dissipating at least a portion of the steam in the main steam line to the atmosphere and having an atmosphere discharge valve with an adjustable opening, the operating method comprising the steps of: a supply steam flow rate specifying step of specifying a supply steam flow rate of the main steam line upstream of the bypass line and the atmosphere discharge line; and, when the supply steam flow rate significantly exceeds the flow rate of main steam consumed by the steam turbine, adjusting the opening rates of the bypass valve and the atmosphere discharge valve in accordance with the supply steam flow rate.

[0016] This storage medium is a storage medium that stores a computer program that operates a control device that controls the operation of the steam turbine power plant, and the computer program is organized into a group of steps that executes any of the above-mentioned steam turbine power plant operation methods.

[0017] This steam turbine power plant comprises: a steam turbine connected to a generator; a main steam line provided upstream of the steam turbine; a bypass line branching from the main steam line to allow at least a portion of the steam in the main steam line to bypass the steam turbine, the bypass line having an adjustable bypass valve with an adjustable opening; an atmosphere discharge line branching from the main steam line to discharge at least a portion of the steam in the main steam line to the atmosphere, the atmosphere discharge valve with an adjustable opening; and a control unit, wherein the control unit outputs control signals to execute: a supply steam flow rate specifying step of specifying a supply steam flow rate in the main steam line upstream of the bypass line and the atmosphere discharge line; a steam turbine operating state determination step of determining whether the steam turbine is in a predetermined non-steady operating state; and an opening adjustment step of adjusting the openings of the bypass valve and the atmosphere discharge valve in accordance with the supply steam flow rate, if it is determined in the steam turbine operating state determination step that the steam turbine is in the predetermined non-steady operating state.

[0018] The present invention adjusts the openings of the bypass valve and the atmospheric discharge valve when it is determined that the steam turbine is in a predetermined unsteady operating state. As a result, the flow rate of steam flowing through the bypass line and the atmospheric discharge line can be appropriately set according to the main steam consumption balance in the unsteady operating state, so that the operation of the steam turbine power plant can be stably adjusted even in the unsteady operating state.

[0019] Fig. 1 is a configuration diagram of a power plant according to an embodiment. Fig. 2 is an explanatory diagram showing the flow of steam in a steady operating state. Fig. 3 is a flowchart relating to valve opening adjustment in an unsteady operating state of the power plant. Fig. 4 is a first explanatory diagram showing the flow of steam during a turbine trip. Fig. 5 is a second explanatory diagram showing the flow of steam during a turbine trip. Fig. 6 is a first explanatory diagram showing the flow of steam when steam consumption is reduced. Fig. 7 is a second explanatory diagram showing the flow of steam when steam consumption is reduced. Fig. 8 is a configuration diagram of a power plant according to another embodiment.

[0020] 1 is a configuration diagram showing an example of a steam turbine power plant (power plant) according to this embodiment, which includes a high-pressure turbine 21 (steam turbine) and a low-pressure turbine 22. The power plant includes a high-pressure boiler 11 that generates main steam (high-pressure steam), a high-pressure turbine 21 that drives a generator 31 with the main steam supplied from the high-pressure boiler 11, a low-pressure boiler 12 that reheats steam exhausted from the high-pressure turbine 21 to generate low-pressure steam, a low-pressure turbine 22 that drives the generator 31 together with the high-pressure turbine 21 with the low-pressure steam supplied from the low-pressure boiler 12, and a condenser 41 connected to the exhaust side of the low-pressure turbine 22.

[0021] The high-pressure boiler 11 generates high-pressure steam as main steam, for example, at a pressure in the range of 12.0 to 16.0 MPa (A) and a temperature in the range of 450 to 550°C, and supplies the high-pressure steam to the main steam line 501. There are no particular limitations on the configuration of the high-pressure boiler 11, but examples include a boiler with a well-known configuration that burns a liquid fuel such as heavy oil or a solid fuel such as coal or biomass pellets to generate steam.

[0022] The high-pressure turbine 21 rotates rotor blades using main steam supplied from the high-pressure boiler 11, driving a generator 31 connected to the rotor blade's rotation shaft to generate electricity. A reducer 32 is provided between the high-pressure turbine 21 and the generator 31 in this example. The inlet of the high-pressure turbine 21 is connected to the main steam line 501 via a high-pressure turbine steam line 502, and receives main steam via this high-pressure turbine steam line 502. The high-pressure turbine 21 in this example is configured as a back-pressure turbine, and discharges steam at a pressure within a range of, for example, 2.0 to 5.0 MPa (A) and 280 to 380°C toward the high-pressure turbine exhaust line 506.

[0023] The downstream end of the high-pressure turbine exhaust line 506 is connected to the low-pressure boiler 12. The low-pressure boiler 12 heats the steam discharged from the high-pressure turbine 21 and supplies the low-pressure steam to the low-pressure steam line 507 as low-pressure steam at a pressure within a range of, for example, 1.8 to 4.2 MPa (A) and 440 to 550°C. There are no particular limitations on the configuration of the low-pressure boiler 12, but an example of the low-pressure boiler is a waste heat boiler that utilizes the combustion exhaust gas discharged when fuel is combusted in the high-pressure boiler 11.

[0024] The low-pressure turbine 22 rotates rotor blades using low-pressure steam supplied from the low-pressure boiler 12, driving a generator 31 connected to the rotor blade's rotating shaft to generate electricity. In the power plant of this example, the low-pressure turbine 22 is connected to the same generator 31 as the high-pressure turbine 21, and these turbines 21, 22 jointly generate electricity. The inlet of the low-pressure turbine 22 is connected to a low-pressure steam line 507 via a low-pressure turbine row steam line 508, and receives low-pressure steam via this low-pressure turbine row steam line 508. Furthermore, the low-pressure turbine 22 of this example is configured as a condensing turbine, and a condenser 41 is provided at the downstream end of a low-pressure turbine exhaust line 511 connected to the outlet side of the low-pressure turbine 22.

[0025] The condenser 41 cools and condenses the steam discharged from the low-pressure turbine 22, and adjusts the outlet pressure of the low-pressure turbine 22 to a vacuum pressure in the range of, for example, 3.0 to 30 kPa (A). In the power plant of this example, an air-cooled condenser 41 is provided, but the method for cooling the steam discharged from the low-pressure turbine 22 is not limited to using a gas refrigerant (atmosphere in the case of an air-cooled condenser). For example, the steam may be cooled using a liquid refrigerant such as industrial water or seawater. A liquid pump 43 is connected downstream of the condenser 41 via a condensate drum 42, and the steam condensate is reused as boiler water.

[0026] A power plant having the above-described basic configuration is provided with a configuration for stably operating the power plant when, in an unsteady operating state, the flow rate of main steam supplied from the main steam line 501 becomes unbalanced with the flow rate of main steam consumed by the high-pressure turbine 21. That is, the main steam line 501 is provided with a first bypass line 503 branching from the main steam line 501 and connected to a high-pressure turbine exhaust line 506 on the outlet side of the high-pressure turbine 21. The low-pressure steam line 507 is provided with a second bypass line 509 branching from the low-pressure steam line 507 and connected to a low-pressure turbine exhaust line 511 on the outlet side of the low-pressure turbine 22. Here, the first bypass line 503 constitutes a "bypass line" of this power plant, provided to allow at least a portion of the steam in the main steam line 501 to bypass the high-pressure turbine (steam turbine) 21. In addition, the second bypass line 509 constitutes the "low-pressure steam bypass line" of this power plant, which is provided to allow at least a portion of the low-pressure steam in the low-pressure steam line 507 to bypass the low-pressure turbine 22.

[0027] A first bypass valve (bypass valve) 61 is provided in the first bypass line 503. For example, when a pressure gauge detects that the pressure in the high-pressure turbine steam line 502 upstream of the high-pressure turbine 21 exceeds a preset operating pressure (first predetermined pressure), the first bypass valve 61 adjusts its opening from a closed state to an open state, allowing main steam to flow toward the first bypass line 503 (first pressure control step). The first bypass valve 61 also performs pressure control by increasing its opening as the detected pressure in the high-pressure turbine steam line 502 becomes higher than the operating pressure, thereby keeping the pressure in the high-pressure turbine steam line 502 below the operating pressure. These control operations are performed by a controller that controls the operation of the first bypass valve 61 (the pressure controller is designated by the letter "P" in the figure; the same applies to the control operations of various valves below). The pressure controller controls the operation of the first bypass valve 61 based on the steam pressure measured by a pressure gauge (not shown). The operating pressure is set, for example, to be equal to the upper limit of the operating range of the pressure upstream of the high-pressure turbine 21 .

[0028] Furthermore, a first water injection line 504 is connected to the first bypass line 503. The first water injection line 504 injects cooling water to lower the temperature of the steam flowing from the main steam line 501 toward the high-pressure turbine exhaust line 506. For example, room-temperature boiler water is supplied as cooling water from the first water injection line 504. A first water injection valve 62 is also provided in the first water injection line 504. For example, the first water injection valve 62 detects the temperature of the steam flowing through the first bypass line 503 downstream of the cooling water injection position using a thermometer. When the detected temperature exceeds a predetermined target temperature, the first water injection valve 62 switches from a closed state to an open state, thereby injecting cooling water toward the first bypass line 503. The first water injection valve 62 performs temperature control by increasing its opening degree as the detected steam temperature increases above the target temperature, thereby lowering the temperature of the steam flowing through the first bypass line 503. The target temperature is set, for example, to be equal to the temperature of the steam discharged from the high-pressure turbine 21 toward the high-pressure turbine exhaust line 506.

[0029] Similarly to the first bypass line 503, a second bypass line 509 for bypassing the low-pressure steam supplied from the low-pressure steam line 507 is also provided with a second bypass valve (low-pressure bypass valve) 64 that adjusts its opening degree to allow the low-pressure steam to flow toward the second bypass line 509 when the pressure in the low-pressure turbine steam line 508 upstream of the low-pressure turbine 22 measured by a pressure gauge exceeds a predetermined operating pressure. The second bypass valve 64 operates in the same manner as the first bypass valve 61, except that the operating pressure is set to be equal to, for example, the upper limit of the operating range of the pressure upstream of the low-pressure turbine 22. The above-mentioned operating pressure corresponds to the "first predetermined pressure" for the second bypass valve 64, and the operation of flowing low-pressure steam using the second bypass valve 64 also corresponds to the "first pressure control step" using the second bypass line 509.

[0030] Furthermore, a second water injection line 510 is connected to the second bypass line 509, through which cooling water is injected to lower the temperature of steam flowing from the low-pressure steam line 507 side toward the low-pressure turbine exhaust line 511 side. A second water injection valve 65 is also interposed in the second water injection line 510. The second water injection valve 65 detects the temperature of steam downstream of the cooling water injection position using a thermometer, and when the detected temperature becomes higher than a predetermined target temperature, the second water injection valve 65 switches from a closed state to an open state, thereby injecting cooling water. The second water injection valve 65 operates in the same manner as the first water injection valve 62, except that the target temperature is set to be equal to, for example, the temperature of steam discharged from the low-pressure turbine 22 toward the low-pressure turbine exhaust line 511.

[0031] Furthermore, in addition to the first bypass line 503 described above, the main steam line 501 is provided with an atmosphere release line 505 branching off from the main steam line 501. For example, the base end of the atmosphere release line 505 is connected downstream of the position where the first bypass line 503 branches off from the main steam line 501 and upstream of the installation position of a pressure gauge that detects pressure for controlling the operation of the first bypass valve 61. The end end of the atmosphere release line 505 is configured to be able to release steam to the atmosphere. An atmosphere release valve 63 is interposed in this atmosphere release line 505. For example, when a pressure gauge measures that the pressure in the atmosphere release line 505 before the atmosphere release valve 63 exceeds a preset operating pressure (second predetermined pressure), the atmosphere release valve 63 adjusts its opening from a closed state to an open state to release the main steam to the atmosphere. Furthermore, the atmosphere release valve 63 performs pressure control by increasing the opening degree as the measured pressure in the atmosphere release line 505 becomes higher than the operating pressure, thereby reducing the pressure in the atmosphere release line 505 to below the operating pressure. The operating pressure is set, for example, higher than the upper limit of the operating range of the pressure upstream of the high-pressure turbine 21 and lower than the design pressure of the piping that constitutes the atmosphere release line 505. In other words, the operating pressure (second predetermined pressure) of the atmosphere release valve 63 is set to a value higher than the operating pressure (first predetermined pressure) of the first bypass valve 61.

[0032] In the power plant having the basic configuration described above, operation control is performed via a Distributed Control System (DCS) 7, which is a control system (control unit) that performs overall control of control devices provided at various locations in the power plant, including the above-mentioned control valves (first and second bypass valves 61 and 64, first and second water injection valves 62 and 65, and atmosphere release valve 63). The DCS has the function of setting control target values ​​(operating pressures and target temperatures in the case of the above-mentioned control valves 61 to 65) for the controllers of each control device, and of acquiring measurement data at predetermined time intervals from measuring devices such as thermometers, pressure gauges, and flow meters provided at various locations in the power plant, thereby monitoring the operating status of the power plant.

[0033] The high-pressure turbine 21 and the low-pressure turbine 22 are connected to a safety instrumentation system (not shown). The generator 31 and other devices that use electricity in the power plant are connected to a power distribution system (not shown). Electric power generated by the generator 31 and power received from an external source are supplied to the devices that use electricity via this power distribution system.

[0034] Furthermore, the DCS 7 can acquire signals indicating that the high-pressure turbine 21 and the low-pressure turbine 22 are in an unsteady operating state from the equipment constituting the power plant and the equipment installed in the auxiliary facilities. Examples of such signals include a turbine trip signal issued from the safety instrumentation system when the high-pressure turbine 21 or the low-pressure turbine 22 undergoes an emergency shutdown (hereinafter also referred to as a "turbine trip"), a load shedding command signal issued from the power distribution system when the load on the generator 31 is shedding, and an islanding command signal issued from the power distribution system when the power plant stops transmitting generated power to the outside and operates to generate power consumed only within the facility where the power plant is installed. Based on any of these signals, the DCS 7 can determine that the high-pressure turbine 21 and the low-pressure turbine 22 are in a predetermined unsteady operating state (steam turbine operating state determination process).

[0035] Furthermore, the method by which the DCS 7 determines whether the power plant is in an unsteady operating state is not limited to receiving a signal from the relevant equipment. For example, the power plant may be determined to be in an unsteady operating state when the flow rate of main steam (supply steam flow rate) flowing through the main steam line 501 exceeds the required steam flow rate of the high-pressure turbine 21 by a predetermined value or more. Here, the "required steam flow rate" refers to a steam flow rate determined based on a demand from the consumer side that uses the main steam, such as the required amount of power generation required for the generator 31 or the steam flow rate required for the high-pressure turbine 21 during load rejection. From this perspective, the required steam flow rate has a different definition from the flow rate of main steam flowing through the high-pressure turbine flow steam line 502 (the "high-pressure turbine flow rate F1" described below).

[0036] The actual required steam flow rate varies depending on the required power generation amount required for the generator 31 and the power required to rotate the turbines 21, 22 during the load shedding described above. When determining the required steam flow rate based on the required power generation amount, for example, the DCS 7 has a function of calculating the required steam flow rate according to the required power generation amount. Then, when the flow rate of the main steam flowing through the main steam line 501 exceeds this required steam flow rate by, for example, 30% or more, it is determined that the system is in an unsteady operating state. For example, when the required steam flow rate is 60 tons / hour, it is determined that the system is in an unsteady state when the main steam flow rate is 78 tons / hour or more (exceeding the required steam flow rate by 18 tons / hour or more).

[0037] As another example, the DCS 7 may determine that the high-pressure turbine 21 is in an unsteady operating state when, for example, the rate of decrease of the required steam flow rate on the high-pressure turbine 21 side within a predetermined time exceeds a predetermined value or more. ０ If the required steam flow rate after a predetermined time has elapsed is FD', the decrease rate is "(FD ０ -FD')×100 / FD ０ A specific example is a case where the reduction rate of the required steam flow rate is between 50% and 100% within a predetermined time period of between 0.1 and 10 seconds. The method to be used to determine whether the high-pressure turbine 21 and the low-pressure turbine 22 are in an unsteady operating state is preset in the DCS 7. The following describes an example where a signal indicating that the high-pressure turbine 21 and the low-pressure turbine 22 are in an unsteady operating state is acquired.

[0038] The DCS 7 is composed of a computer including a storage unit storing a program, a memory, and a CPU. The program contains instructions (steps) for outputting control signals such as control target values ​​to each control device in the power plant, acquiring measurement data from each measurement device, and operating the power plant. The program is stored in the computer's storage unit, such as a flexible disk, compact disk, hard disk, or non-volatile memory, and is read from this storage unit and installed in the DCS 7.

[0039] In Figure 2, the steam flow in the above-described power plant during steady operation is indicated by a bold line. Here, "steady operation" refers to a state in which the DCS 7 does not receive a signal indicating that the high-pressure turbine 21 and the low-pressure turbine 22 are in an unsteady operation state. In the power plant shown in Figures 2 to 8, components common to those described using Figure 1 are denoted by the same reference numerals. During steady operation, main steam is supplied from the high-pressure boiler 11 at a flow rate F0 (unit: ton / hour, for example; hereinafter, this applies to the steam flow rate and the water injection flow rate) and temperature T1 corresponding to the power output to be generated. The entire amount of main steam is supplied to the high-pressure turbine 21 via a main steam line 501 and a high-pressure turbine-flow steam line 502 (high-pressure turbine-flow flow rate F1 = F0). The high-pressure turbine-flow steam line (turbine-flow steam line) 502 is provided with a turbine-flow valve (not shown) whose opening is adjustable. That is, this turbine-row valve is provided downstream of the branch point of the main steam line 501 with the atmosphere release line 505 and the branch point with the first bypass line 503. In this case, for example, the flow rate F0 of the main steam flowing through the main steam line 501 can be determined based on the aperture of the first bypass valve 61 provided in the first bypass line 503, the aperture of the atmosphere release valve 63 provided in the atmosphere release line 505, and the aperture of the turbine-row valve provided in the high-pressure turbine-row steam line 502. Note that a flow meter for measuring the steam flow rate may be provided in the main steam line 501, and the flow rate F0 of the main steam may be determined by this flow meter.

[0040] Next, the steam discharged from the high-pressure turbine 21 is heated in the low-pressure boiler 12 and is re-supplied as low-pressure steam with a flow rate of F3 (=F0) and a temperature of T2. The entire amount of the low-pressure steam is supplied to the low-pressure turbine 22 via a low-pressure steam line 507 and a low-pressure turbine steam line 508. By supplying main steam and low-pressure steam to the high-pressure turbine 21 and low-pressure turbine 22, the rotor blades in each turbine are rotated to drive the generator 31, thereby generating electricity.

[0041] The steam discharged from the low-pressure turbine 22 flows into the condenser 41 via the low-pressure turbine exhaust line 511, where it is cooled and condensed to form condensed water. The processable amount C per unit time [tons / hour] of the condenser 41 (hereinafter simply referred to as the "processable amount C") is set to a value greater than the flow rate of steam exhausted from the low-pressure turbine 22 within the range of power output during steady-state operation of the power plant. In some cases, the high-pressure turbine 21 and the low-pressure turbine 22 extract a portion of steam from an intermediate stage and supply it to other steam users. In such cases, the flow rate of steam exhausted from the low-pressure turbine 22 is less than the flow rate F0 of main steam supplied from the high-pressure boiler 11. Therefore, the processable amount C of the condenser 41 may also be set to a value smaller than the main steam flow rate F0.

[0042] Moreover, under pressure conditions in a steady operating state, the first bypass valve 61 and the second bypass valve 64 are closed, and steam does not flow through the first bypass line 503 and the second bypass line 509. Therefore, no cooling water is injected from the first water injection line 504 and the second water injection line 510 (f1 = f2 = 0). Moreover, under pressure conditions in a steady operating state, the atmosphere release valve 63 is also closed, and steam is not released from the atmosphere release line 505 to the atmosphere.

[0043] On the other hand, even in a steady operating state, due to a delay in control when changing the power plant output, the pressure in the high-pressure turbine row steam line 502 and the low-pressure turbine row steam line 508 may rise and exceed the operating pressure of the first bypass valve 61 and the second bypass valve 64. In this case, the first and second bypass valves 61 and 64 are operated based on the results of detecting the pressure in the high-pressure turbine row steam line 502 and the low-pressure turbine row steam line 508, and a portion of the steam (main steam directed to the high-pressure turbine row steam line 502 and low-pressure steam directed to the low-pressure turbine row steam line 508) is caused to flow toward the first and second bypass lines 503 and 509, thereby performing the above-mentioned pressure control to restore the pressure below the operating pressure. Note that, for convenience, the operations of the first and second bypass valves 61 and 64 are described together here, but the pressure control operations of the first and second bypass valves 61 and 64 based on the results of detecting the pressure in the high-pressure and low-pressure turbine row steam lines 502 and 508 are performed independently of each other.

[0044] Furthermore, when the temperature of the steam detected downstream of the water injection position becomes higher than the target temperature due to the flow of steam through the first and second bypass lines 503 and 509, the first and second water injection valves 62 and 65 are activated to start injecting cooling water. Then, the amount of water injected is increased or decreased according to the temperature detection results of each bypass line 503 and 509, thereby executing the above-mentioned temperature control to maintain the temperature of the bypass lines 503 and 509 at the target temperature.

[0045] Here, in a steady-state operating state, the processing capacity C of the condenser 41 is set to be greater than the sum of the flow rate of the low-pressure steam flowing into the second bypass line 509 and the flow rate f2 of the cooling water injected from the second water injection line 510, relative to the flow rate of the steam exhausted from the low-pressure turbine 22, when a pressure control operation is performed to flow steam into each bypass line 503, 509.

[0046] Furthermore, in a steady-state operating state, even if the first bypass valve 61 is operated to control the pressure, if the pressure continues to rise and it is detected that the pressure in the atmospheric release line 505 is greater than the operating pressure described above, the atmospheric release valve 63 opens and releases steam into the atmosphere.

[0047] As described above, in steady-state operation, unless the pressures in the high-pressure and low-pressure turbine steam lines 502 and 508 reach or exceed the operating pressures of the first and second bypass valves 61 and 64, operation is performed without steam flowing into the first and second bypass lines 503 and 509. Then, once the pressures in the high-pressure and low-pressure turbine steam lines 502 and 508 reach or exceed the operating pressures, the first and second bypass valves 61 and 64 are opened as described above to allow steam to flow into the first and second bypass lines 503 and 509, and water is injected through the first and second water injection lines 504 and 510. Furthermore, once the pressure upstream of the high-pressure turbine 21 rises and the pressure in the atmospheric release line 505 reaches or exceed the operating pressure, the atmospheric release valve 63 is opened to release a portion of the steam into the atmosphere.

[0048] In this way, for the first bypass line 503, the second bypass line 509 and the atmospheric release line 505, the opening of each valve 61, 64, 63 is adjusted to allow steam to flow depending on the pressure before the high-pressure turbine 21 (high-pressure turbine steam line 502 or atmospheric release line 505) or before the low-pressure turbine 22 (low-pressure turbine steam line 508).

[0049] On the other hand, during the aforementioned turbine trip, the steam consumption in the high-pressure turbine 21 and the low-pressure turbine 22 becomes zero in an extremely short time of less than a few seconds, usually less than one second. Meanwhile, it is preferable to continue operating the high-pressure boiler 11 (including the low-pressure boiler 12, which is a waste heat boiler) as long as possible, because it is difficult to significantly reduce the steam supply flow rate in a short time in response to a turbine trip, and restarting the boiler once it has stopped is difficult. Therefore, there continues to be a period in which the flow rate F0 of the main steam supplied from the high-pressure boiler 11 via the main steam line 501 significantly exceeds the flow rate of steam consumed by the high-pressure turbine 21 and the low-pressure turbine 22 (F1 = F3 = 0 during a turbine trip).

[0050] If no action is taken at this time, the main steam flow rate F0 will exceed the steam flow rates (high-pressure turbine flow rate F1 and low-pressure turbine flow rate F3) directed toward the high-pressure turbine 21 and low-pressure turbine 22, causing a rise in pressure in the high-pressure and low-pressure turbine-directed steam lines 502 and 508. This pressure rise causes the first and second bypass valves 61 and 64 to open and allow steam to flow toward the first and second bypass lines 503 and 509. Furthermore, even after these pressure adjustment operations have been performed, there is still excess steam, and if this causes a rise in pressure in the atmospheric release line 505, the atmospheric release valve 63 will operate and the steam will be released into the atmosphere.

[0051] However, when the main steam flow rate F0 significantly exceeds the high-pressure turbine flow rate F1 and the low-pressure turbine flow rate F3, opening and closing the valves 61, 64, and 63 in response to the pressure detection results of the lines 502, 508, and 505 as described above causes severe pressure fluctuations during the transient response period until the pressure stabilizes, resulting in an unstable power plant. In particular, if the flow rate of steam flowing into the bypass lines 503 and 509 increases suddenly, the water injection control from the water injection lines 504 and 510 may be unable to keep up, resulting in an over-temperature condition, an emergency shutdown of each component, and ultimately a trip of the entire power plant, including the high-pressure boiler 11. Furthermore, when a turbine trips, a large amount of excess steam is generated in an extremely short time, and pressure control by the valves 61, 64, and 63 may be unable to keep up, causing a safety valve (not shown) installed in the system to operate, resulting in a loss of a large amount of steam being released to the outside.

[0052] To avoid such an unstable state, the power plant of this embodiment is configured to directly adjust the openings of the first bypass valve 61, the second bypass valve 64, the atmospheric release valve 63, etc., instead of the pressure control described above, when the main steam flow rate F0 greatly exceeds the high-pressure turbine flow rate F1 and the low-pressure turbine flow rate F3, as occurs during a turbine trip.

[0053] However, if the only measure to be taken is to prevent the power plant from becoming unstable, operation with a margin can be achieved by maximizing the aperture of the atmospheric release valve 63, fixing the amount of atmospheric release, and then flowing the remaining steam through the first bypass line 503 and the second bypass line 509. However, because variable costs and other expenses are required to produce pure water for generating steam, there are cases where it is desirable to avoid aperture adjustment that prioritizes atmospheric release. Therefore, in the power plant of this embodiment, aperture adjustment of the first and second bypass valves 61 and 64, the atmospheric release valve 63, and the like is performed to enable stable operation while suppressing an increase in loss due to prioritizing atmospheric release. Specific details of aperture adjustment will be described below.

[0054] As also shown in FIG. 2 and other figures, in response to a turbine trip, the DCS 7 uses information on the main steam flow rate F0, the main steam temperature T1, and the low-pressure steam temperature T2. By identifying the flow rate of the main steam flowing through the main steam line 501 (a supply steam flow rate identification process), it is possible to determine the steam flow rates that need to be flowed toward the first and second bypass lines 503 and 509 or the atmospheric release line 505 in the event of a turbine trip. A specific method for determining these steam flow rates will be described in detail later. Alternatively, the main steam flow rates F0, the main steam temperature T1, and the low-pressure steam temperature T2 may be calculated in real time based on actual values ​​of the main steam flow rate F0, the main steam temperature T1, and the low-pressure steam temperature T2. Alternatively, the steam flow rates may be calculated in advance based on estimated values ​​of the main steam flow rate F0, the main steam temperature T1, and the low-pressure steam temperature T2. In this case, a table may be created in which the estimated values ​​of the main steam flow rate F0, the main steam temperature T1, and the low-pressure steam temperature T2 correspond to the steam flow rates of the first and second bypass lines 503 and 509 and the atmospheric release line 505.

[0055] Furthermore, once the main steam temperature T1 is specified, the water injection flow rate f1 from the first water injection line 504 can be calculated according to the flow rate of main steam flowing into the first bypass line 503 and the target temperature of the steam after water injection. Similarly, once the low-pressure steam temperature T2 is specified, the water injection flow rate f2 from the second water injection line 510 can be calculated according to the flow rate of low-pressure steam flowing into the second bypass line 509 and the target temperature of the steam after water injection. Then, the openings of the first and second water injection valves 62, 65 are determined based on these water injection flows f1, f2.

[0056] If the flow rate of main steam flowing into first bypass line 503 and the flow rates f1 and f2 of water injection from first and second water injection lines 504 and 510 can be determined from the results of these calculations, it is possible to determine the flow rate of steam to be treated in condenser 41. DCS 7 determines opening degrees Q1 to Q5 of first and second bypass valves 61 and 64, first and second water injection valves 62 and 65, and atmosphere release valve 63 so as to direct the entire amount of steam that has become surplus due to a turbine trip toward at least one of first and second bypass lines 503 and 509 and atmosphere release line 505, while avoiding atmospheric release of steam from atmosphere release line 505 as much as possible (opening degree adjustment step).

[0057] In order to avoid venting steam to the atmosphere as much as possible, the DCS 7 determines the opening degrees Q1, Q3, and Q2 so as to open the first and second bypass valves 61, 64 prior to the atmospheric vent valve 63. Meanwhile, as a criterion for determining whether venting steam to the atmosphere is necessary, the DCS 7 determines whether the total flow rate of the main steam flow rate F0 and the water injection flow rates f1, f2 exceeds the downstream acceptance constraint of the first and second bypass lines 503, 509. In this embodiment, a case is illustrated in which the acceptance constraint is the processable amount C of the condenser 41 connected to the downstream end of the bypass line (the entirety of the first bypass line 503 and the second bypass line 509). However, the acceptance constraint is not limited to the processable amount C of the condenser 41. For example, the acceptance constraint may be an upper limit of the liquid feed flow rate of the liquid feed pump 43, a constraint on the piping flow rate, or a flow rate constraint of equipment or meters installed in the flow path.

[0058] The operation of the power plant in an unsteady operating state will be described below based on the flowchart in Fig. 3 and the above-described flows shown in Figs. 4 and 5. In Fig. 4, the thick line indicates the steam flow when the total flow rate of the main steam flow rate F0 and the water injection rates f1 and f2 does not exceed the processing capacity C of the condenser 41 (F0 + f1 + f2 < C) during turbine trip. During operation (start) of the power plant, the DCS 7 acquires the main steam flow rate (supply steam flow rate) F1 in the main steam line 501 measured by a flow meter at preset time intervals (step S101 in Fig. 3, supply steam flow rate determination step). If the DCS 7 has not received a signal indicating an unsteady operating state (a turbine trip signal in the examples of Figs. 4 and 5) (step S102: NO in Fig. 3), it continues to acquire the supply steam flow rate F1.

[0059] When a turbine trip occurs in the high-pressure turbine 21 or the low-pressure turbine 22 and a turbine trip signal is received, the DCS 7 determines that the turbines 21 and 22 that have experienced the turbine trip are in an unsteady operating state (step S102: YES, steam turbine operating state determination step). If it is determined that the turbines are in an unsteady operating state, the DCS 7 calculates the water injection flow rates f1 and f2 based on the measurement results of the main steam flow rate F0, the main steam temperature T1, and the low-pressure steam temperature T2, and determines the openings of the bypass valves 61 and 64, the atmospheric release valve 63, and the water injection valves 62 and 65 (step S103).

[0060] As a result, if the total flow rate of F0, f1, and f2 does not exceed the processable amount C of the condenser 41, the DCS 7 adjusts the aperture Q1 of the first bypass valve 61 so that the entire amount F0 of main steam flows into the first bypass line 503 (step S104, aperture adjustment step). Then, the DCS 7 adjusts the aperture Q4 of the first water injection valve 62 so that cooling water is injected at an injection flow rate f1 corresponding to the main steam flow rate F0 and temperature T1. As a result, the flow rate of steam downstream of the cooling water injection position in the first bypass line 503 (high-pressure bypass line flow rate) becomes F2 (= F0 + f1).

[0061] Since this steam flow rate F2 corresponds to the flow rate of low-pressure steam supplied from the low-pressure boiler 12, the DCS 7 adjusts the aperture Q3 of the second bypass valve 64 so that the entire amount of low-pressure steam flows into the second bypass line 509 (step S104, aperture adjustment step). Furthermore, the DCS 7 adjusts the aperture Q5 of the second water injection valve 65 so that cooling water is injected at an injection flow rate f2 corresponding to the low-pressure steam flow rate F2 and temperature T2. Meanwhile, as described above, since the entire amount of main steam flowing through the main steam line 501 can flow into the first bypass line 503, the DCS 7 keeps the atmosphere release valve 63 closed (aperture Q2 = 0) (step S104, aperture adjustment step) and ends the operation to deal with excess steam in the unsteady operating state (end).

[0062] Here, when determining whether the total flow rate of F0, f1, and f2 exceeds the processable capacity C of the condenser 41, it is not essential to perform a calculation to determine the total value of these flow rates. The water injection flow rates f1 and f2 can be determined in advance by assuming the main steam and low-pressure steam temperatures T1 and T2. Therefore, an upper limit value of the main steam flow rate F0 that is allowable from the processable capacity C may be determined in advance based on the results of determining these water injection flow rates f1 and f2 in advance. In this case, it is only necessary to determine whether the main steam flow rate F0 exceeds the upper limit value at the time of turbine trip, allowing for more rapid control.

[0063] Here, the injection water flow rates f1 and f2 are small compared to the flow rates of steam flowing through the bypass lines 503 and 509. Therefore, when the above-described method is adopted, even if the actual steam temperatures T1 and T2 deviate from the assumed values, the rate of increase or decrease in the injection water flow rates f1 and f2 is small. Furthermore, taking the injection water flow rates f1 and f2 into consideration, the upper limit value of the main steam flow rate F0 can be set so that the flow rate of steam flowing through the bypass lines 503 and 509 is in a state with a margin relative to the processable amount C. Therefore, even when the openings Q1 to Q5 of the valves 61, 64, 62, 65, and 63 are adjusted using the upper limit value of the main steam flow rate F0, which is set by determining the injection water flow rates f1 and f2 in advance, as a criterion, operation control during a turbine trip can be stably executed.

[0064] By adjusting the valve openings Q1 to Q5 as described above, when a turbine trip occurs, all of the excess main steam flows into the first bypass line 503, passes through the first bypass line 503, passes through the low-pressure boiler 12, and passes through the second bypass line 509, and is recovered as condensate in the condenser 41, as shown by the bold lines in Figure 4. At this time, the valve openings Q1 to Q5 are adjusted based on the measurement results of the main steam flow rate F0, the main steam temperature T1, and the low-pressure steam temperature T2 at the time of the turbine trip, and the water injection flow rates f1 and f2 determined from these measurement results. This reduces fluctuations in pressure and flow rate, enabling stable disposal of the excess main steam, compared to when control is performed in which the openings Q1 to Q5 are changed based on the results of detecting the pressures in the high-pressure turbine steam line 502, the low-pressure turbine steam line 508, and the atmospheric release line 505.

[0065] 5 shows, with a bold line, the flow of steam when the total flow rate of the main steam flow rate F0 and the injection water flow rates f1 and f2 exceeds the processing capacity C of the condenser 41 (F0+f1+f2≧C) during a turbine trip. In this case, the condenser 41 cannot process the entire amount of main steam supplied to the main steam line 501, so the steam must be released into the atmosphere.

[0066] 3 , the DCS 7, which has received the turbine trip signal in step S102, calculates the water injection flow rates f1 and f2 based on the measurement results of the main steam flow rate F0, the main steam temperature T1, and the low-pressure steam temperature T2, and determines the openings of the bypass valves 61 and 64, the atmospheric release valve 63, etc. (step S103), as in the previously described example. As a result, if the total flow rate of F0, f1, and f2 exceeds the processable capacity C of the condenser 41, the DCS 7 executes the following operation. Note that, as already described, the above determination is not limited to the case of performing a calculation to determine the total value of the flow rates of F0, f1, and f2, and it is also possible to only determine whether the main steam flow rate F0 exceeds a preset upper limit value.

[0067] For example, the DCS 7 calculates, by back-calculating from the processable amount C, which is the acceptance constraint, for example, the low-pressure steam flow rate (i.e., the steam flow rate flowing in from the first bypass line 503 side) F2 (=F0+f1) and the water injection flow rate f2 from the second water injection line 510 so that F0+f1+f2≦C holds. In the following example, in order to minimize the atmospheric release flow rate F4, the maximum steam flow rate F2 is calculated so that F0+f1+f2=C holds. ＭＡＸ , water injection flow rate f1 ＭＡＸ , f2 ＭＡＸ However, the flow rates F2, f1, and f2 may be calculated so that a margin is provided for the processable amount C of the condenser 41 and F2+f2=αC (for example, α=0.6 to 0.9).

[0068] When the target temperature of the second bypass line 509 after the cooling water injection is constant, the flow rate ratio (f2 / F2) between the low-pressure steam flow rate F2 and the injection water flow rate f2 can be determined according to the low-pressure steam temperature T2. From this flow rate ratio and the relationship F0+f1+f2=F2+f2=C, the maximum value of each flow rate (F2 ＭＡＸ , f2 ＭＡＸ Next, the DCS 7 calculates the maximum values ​​of the main steam flow rate F5 and the water injection flow rate f1 that can be received in the first bypass line 503 (F5 ＭＡＸ , f1 ＭＡＸ In this calculation, the maximum value of each flow rate can also be calculated from the relationship of F2=F5+f1 and the flow rate ratio (f1 / F5) between the main steam flow rate F5 and the water injection flow rate f1 that can be received by the first bypass line 503.

[0069] Then, the value obtained by subtracting the maximum value of the main steam flow rate that can be accepted into the first bypass line 503 from the actual main steam flow rate F0 specified at the time of turbine trip (F0-F5) is calculated. ＭＡＸ ) can be identified as corresponding to the atmospheric release flow rate F4 that must be released into the atmosphere from the atmospheric release line 505.

[0070] After specifying the atmospheric release flow rate F4, the DCS 7 determines the maximum value F5 of the steam flow rate flowing into the first bypass line 503 and the second bypass line 509. ＭＡＸ , F2 ＭＡＸ , and the water injection flow rate f1 corresponding to these steam flow rates ＭＡＸ , f2ＭＡＸ , and the valve openings Q1 to Q5 are adjusted to realize the atmospheric diffusion flow rate F4 (step S104, opening adjustment step).

[0071] By adjusting the valve openings Q1 to Q5 as described above, when a turbine trip occurs, excess main steam flows into the first bypass line 503 at a flow rate that corresponds to the processable amount C (acceptance constraint) of the condenser 41, flows through the first bypass line 503 → low-pressure boiler 12 → second bypass line 509, and is recovered as condensate in the condenser 41, as shown by the thick line in Figure 5. At this time, in the balance of flow rates also shown in Figure 5, the steam flow rate (high-pressure bypass line flow rate) in the first bypass line 503 downstream of the water injection position is "F2≦C−f2" (in the case of the maximum value described above, F2=C−f2), and the atmospheric release flow rate is "F4=F0−(F2−f1)>0".

[0072] At this time, the flow rate of main steam released into the atmosphere (atmospheric release flow rate F4) can be limited to only the amount in excess of the processable amount C of the condenser 41, thereby reducing losses associated with release into the atmosphere. Also in these operations, the valve openings Q1 to Q5 are adjusted based on the measurement results of the main steam flow rate F0, main steam temperature T1, and low-pressure steam temperature T2 when a turbine trip signal is issued, and the water injection flows f1 and f2 determined from these measurement results, so fluctuations in pressure and flow rate are small, and excess main steam can be processed stably.

[0073] According to the power plant operation method of this embodiment, when the flow rate of main steam supplied from main steam line 501 exceeds the flow rate consumed by high-pressure turbine 21 and low-pressure turbine 22 (F1 → 0, F3 → 0 during turbine trip), the openings of first bypass valve 61, second bypass valve 64, and atmosphere release valve 63 are adjusted. Therefore, the flow rates of steam flowing through first bypass line 503, second bypass line 509, and atmosphere release line 505 can be appropriately set according to the degree of surplus main steam, so that the operation of the power plant can be stably adjusted even in an unsteady operating state in which the steam supply-consumption balance changes significantly.

[0074] In the above-described embodiment, when a turbine trip occurs and the valve openings Q1 to Q5 are adjusted, the water injection flow rates f1 and f2, the steam flow rates F5 and F2 flowing into the bypass lines 503 and 509, and the atmospheric diffusion flow rate F4 are calculated in real time by the DCS 7, and the valve openings Q1 to Q5 are adjusted. However, as described above, when a turbine trip occurs, the balance of steam consumption changes suddenly in an extremely short time, from less than one second to several seconds, and therefore, it is also required to adjust the valve openings Q1 to Q5 even more quickly.

[0075] Therefore, the water injection flow rates f1 and f2, the steam flow rates F5 and F2 flowing into the bypass lines 503 and 509, and the atmospheric diffusion flow rate F4 may be calculated in advance according to the estimated values ​​of the main steam flow rate F0, the main steam temperature T1, and the low-pressure steam temperature T2, and a table may be created in which the valve openings Q1 to Q5 correspond to these flow rates. In this case, after receiving a turbine trip signal and detecting the main steam flow rate F0, the steam temperature T1, and the steam temperature T2, the valve openings Q1 to Q5 that match these conditions are searched for in the table, and the opening adjustments can be immediately performed based on the search results.

[0076] The above example is a method of preparing a table that associates estimated values ​​of the main steam supply steam flow rate (main steam flow rate F0), the main steam temperature T1, and the low-pressure steam temperature T2 with the opening degrees Q1, Q3, and Q2 of the bypass valves 61, 64 and the atmosphere relief valve 63 (predetermined relationships that have been set in advance).Then, in this pattern, the opening degrees Q1, Q3, and Q2 of the bypass valves 61, 64 and the atmosphere relief valve 63 are determined from the table based on the supply steam flow rate (main steam flow rate F0), the main steam temperature T1, and the low-pressure steam temperature T2 that were measured when a turbine trip signal was issued, and adjustment of the opening degrees is performed.

[0077] As another pattern, the following method may be adopted. In this method, a table is prepared in advance that associates estimated values ​​of the main steam supply steam flow rate (main steam flow rate F0), the main steam temperature T1, and the low-pressure steam temperature T2 with steam flow rates F5, F2, and F4 flowing through the bypass lines 503 and 509 and the atmospheric release line 505 (predetermined relationships). As described above, when a turbine trip occurs, the steam flow rate F2 discharged from the first bypass line 503 becomes the steam flow rate flowing into the second bypass line 507. Based on the supply steam flow rate, main steam temperature T1, and low-pressure steam temperature T2 measured when a turbine trip signal was issued, the openings Q1, Q3, and Q2 of the bypass valves 61 and 64 and the atmospheric release valve 63 are adjusted so that the steam flow rates flowing through the bypass lines 503 and 501 and the atmospheric release line 505 become the predetermined flow rates defined in the table.

[0078] An example of an unsteady operating state to which the above-described patterns can be applied is not limited to a turbine trip. The above-described patterns can also be applied to unsteady operating states such as load shedding and isolated operation, which will be described below with reference to Figures 6 and 7, when the main steam supply flow rate exceeds the required steam flow rate by a predetermined value or more, or when the rate of decrease in the required steam flow rate within a predetermined time exceeds a predetermined value or more. That is, in order to flow the surplus steam flow rate obtained by subtracting the steam flow rates supplied to the high-pressure turbine 21 and the low-pressure turbine 22 from the steam flow rate supplied from the main steam line 501 into at least one of the bypass line 503 and the atmospheric release line 505, adjustment of the opening degrees Q1, Q3, and Q2 of the bypass valves 61 and 64 and the atmospheric release valve 63 based on the above-described patterns can be applied.

[0079] 6 and 7 show examples of how to deal with an excess of main steam under unsteady operating conditions different from those during a turbine trip. That is, in these figures, the high-pressure turbine 21 and the low-pressure turbine 22 continue to operate, but because the steam consumption rate has decreased, the flow rate of main steam supplied from the main steam line 501 exceeds the flow rate of main steam consumed by the high-pressure turbine 21 and the low-pressure turbine 22.

[0080] To give a specific example, in a power plant, when a fault occurs in the power grid, the generator 31 may be disconnected from the power grid, and a load shedding operation may be performed to operate the power plant without load. The power plant may also enter an islanded operation state, in which electricity generated by the generator 31 is consumed only within the facility where the power plant is installed, without selling the electricity. Regarding the load shedding operation, the DCS 7 can determine that an unsteady operating state has occurred by acquiring a load shedding command signal issued from the power distribution system when the generator 31 is disconnected from the power grid. Regarding the islanded operation state, the DCS 7 can determine that an unsteady operating state has occurred by acquiring a command signal for transitioning to islanded operation issued from the power distribution system. All of the above-mentioned determination operations correspond to the steam turbine operating state determination process.

[0081] In these unsteady operating states, the steam consumption in the high-pressure turbine 21 and the low-pressure turbine 22 drops significantly. On the other hand, a lower limit of the steam supply flow rate is set in the high-pressure boiler 11 due to, for example, equipment constraints, and it may not be possible to adjust the supply flow rate below this lower limit. As a result, the main steam flow rate supplied from the main steam line 501 may not balance with the flow rate consumed in the high-pressure turbine 21 and the low-pressure turbine 22, resulting in a surplus.

[0082] 6 shows the steam flow indicated by a bold line when the total flow rate of the main steam flow rate F0 and the injected water flow rates f1 and f2 does not exceed the processing capacity C of the condenser 41 (F0 + f1 + f2 < C) during a decrease in steam consumption (supply steam flow rate specification step). When the steam flow rates of the high-pressure turbine 21 and low-pressure turbine 22 decrease from F1 to F1' (F1 > F1') and from F3 to F3' (F3 > F3'), respectively, the excess main steam is the main steam flow rate F0 minus the high-pressure turbine steam flow rate F1'. Using this excess and the main steam temperature T1, the DCS 7 calculates the injected water flow rate f1 that would be obtained if the entire excess were to flow into the first bypass line 503, and determines the high-pressure bypass line flow rate F2 (= F0 - F1' + f1).

[0083] The steam flowing through the first bypass line 503 is combined with steam exhausted from the high-pressure turbine 21 at a flow rate F1' and then heated in the low-pressure boiler 12. As a result, low-pressure steam at a flow rate F0+f1 is supplied from the low-pressure boiler 12. The flow rate obtained by subtracting the low-pressure turbine steam flow rate F3' from the supplied low-pressure steam is the surplus. Furthermore, the DCS 7 calculates the injection water flow rate f2 that would be achieved if the entire surplus amount were to flow into the second bypass line 509, based on this surplus low-pressure steam and the temperature T2.

[0084] The steam flowing through the second bypass line 509 is then merged with steam at a flow rate F3' exhausted from the low-pressure turbine 22, and is then cooled and condensed in the condenser 41. Therefore, in the condenser 41, steam at a flow rate F0+f1+f2 is processed, and if the condition F0+f1+f2<C is satisfied as described above, excess main steam can be made to flow through the first bypass line 503 and the second bypass line 509 and processed in the condenser 41 without steam dissipation from the atmosphere release valve 63. The DCS 7 adjusts the valve openings Q1 to Q5 so as to achieve the above-mentioned flow rate balance (opening adjustment step).

[0085] By adjusting the valve openings Q1 to Q5 as described above, when steam consumption decreases, all of the excess main steam flows into the first bypass line 503, as shown by the bold line in Figure 6. The steam then flows through the high-pressure turbine 21 and first bypass line 503 → low-pressure boiler 12 → low-pressure turbine 22 and second bypass line 509, and is recovered as condensate in the condenser 41. In this case, by adjusting the valve openings Q1 to Q5 based on the measurement results of the main steam flow rate F0, main steam temperature T1, and low-pressure steam temperature T2 when the turbine trip signal is issued, and the injection water flow rates f1 and f2 determined from these measurement results, fluctuations in pressure and flow rate are reduced, and the excess main steam can be stably treated, just like in the case of a turbine trip.

[0086] 7 shows, with a bold line, the flow of steam when the total flow rate of the main steam flow rate F0 and the water injection flow rates f1 and f2 exceeds the processable amount C of the condenser 41 (F0+f1+f2≧C) during a decrease in steam consumption. In this case, the condenser 41 cannot process all of the excess main steam, so it is necessary to release it to the atmosphere through the atmospheric release line 505.

[0087] Therefore, when the steam consumption rates of the high-pressure turbine 21 and the low-pressure turbine 22 decrease to the above-mentioned F1' and F3', respectively, the DCS 7 calculates the injection water flow rates f1 and f2 based on the measurement results of the main steam flow rate F0, the main steam temperature T1, and the low-pressure steam temperature T2. As a result, when the total flow rate of F0, f1, and f2 exceeds the processing capacity C of the condenser 41, the DCS 7 performs the following operation.

[0088] 5, the DCS 7 calculates, for example, the steam flow rate F0+f1-F3' (hereinafter, this flow rate will be referred to as F6) flowing into the second bypass line 509 and the water injection flow rate f2 from the second water injection line 510 by back-calculating from the processable amount C, which is the acceptance constraint, so that F0+f1+f2≦C holds. In this example, too, in order to minimize the atmospheric release flow rate F4, the maximum steam flow rate F5 that can be accepted by each of the first and second bypass lines 503 and 509 is calculated so that F0+f1+f2=C holds. ＭＡＸ , F6 ＭＡＸ , water injection flow rate f1 ＭＡＸ , f2 ＭＡＸ The calculation of

[0089] As described above, when the target temperature of the second bypass line 509 after the cooling water injection is constant, the flow rate ratio (f2 / F6) of the steam flow rate F0+f1-F3'=F6 flowing into the second bypass line 509 to the water injection flow rate f2 can be determined according to the low-pressure steam temperature T2. From this flow rate ratio, the low-pressure turbine steam flow rate F3', and the relationship of F0+f1+f2=F3'+F6+f2=C, the maximum value of each flow rate (F6 ＭＡＸ , f2 ＭＡＸ ) can be obtained.

[0090] Next, the DCS 7 calculates the maximum values ​​of the main steam flow rate F and the injection water flow rate f1 that can be accepted by the first bypass line 503 (F5 ＭＡＸ , f1 ＭＡＸ ) Taking into consideration the constraint of F5+f1+F1′+f2=C, in this calculation as well, the maximum value of each flow rate can be calculated from the flow rate ratio (f1 / F) between the main steam flow rate F and the injected water flow rate f1 that can be accepted by the first bypass line 503.

[0091] Therefore, the DCS 7 calculates the maximum values ​​of the main steam flow rate and the injection water flow rate f1 that can be accepted by the first bypass line 503 (F5 ＭＡＸ , f1 ＭＡＸ Then, the actual main steam flow rate F0 determined when the steam consumption rate is reduced is subtracted from the maximum value of the main steam flow rate that can be received by the first bypass line 503 and the high-pressure turbine steam flow rate F1' (F0-F5). ＭＡＸ −F1′) can be identified as corresponding to the atmospheric release flow rate F4 that must be released into the atmosphere from the atmospheric release line 505.

[0092] After specifying the atmospheric release flow rate F4, the DCS 7 determines the maximum value F5 of the steam flow rate flowing into the first and second bypass lines 503 and 509. ＭＡＸ , F6 ＭＡＸ , and the water injection flow rate f1 corresponding to these steam flow rates ＭＡＸ , f2 ＭＡＸ and adjusting the valve openings Q1 to Q5 to realize the atmospheric emission flow rate F4 (opening adjustment step).

[0093] By adjusting the valve openings Q1 to Q5 as described above, when the steam consumption rate decreases, excess main steam flows into the first bypass line 503 at a flow rate that corresponds to the processable amount C (acceptance constraint) of the condenser 41, as shown by the bold line in Fig. 7 , flows through the high-pressure turbine 21 and the first bypass line 503 → low-pressure boiler 12 → low-pressure turbine 22 and the second bypass line 509, and is recovered as condensate in the condenser 41. At this time, in the balance of the flow rates also shown in Fig. 7 , the steam flow rate (high-pressure bypass line flow rate) in the first bypass line 503 downstream of the water injection position is "F2≦C−(F1′+f2)", and the atmospheric release flow rate is "F4=F0−(F1′+F2−f1)>0".

[0094] Even in this case, the flow rate of main steam released into the atmosphere (atmospheric release flow rate F4) can be limited to only the amount in excess of the processable amount C of the condenser 41, so that loss due to release into the atmosphere can be minimized. Also in these operations, the valve openings Q1 to Q5 are adjusted based on the measurement results of the main steam flow rate F0, main steam temperature T1, and low-pressure steam temperature T2 when a turbine trip signal is issued, and the water injection flows f1 and f2 determined from these measurement results, so fluctuations in pressure and flow rate are small, and excess main steam can be processed stably.

[0095] 6 and 7, real-time calculation of the steam balance by the DCS 7 is not essential. As described above, in the case of a turbine trip, the valve openings Q1 to Q5 may be adjusted based on the result of determining only whether the assumed main steam flow rate F0 exceeds a preset upper limit. Alternatively, a table may be created in which the valve openings Q1 to Q5 correspond to the steam consumptions F1', F2', main steam temperature T1, and low-pressure steam temperature T2 in the turbines 21 and 22. The valve openings Q1 to Q5 may be searched for in the table based on the values ​​of F0, F1', F2', T1, and T2 when the steam consumption is reduced, and the valve openings may be adjusted.

[0096] The above-described method of adjusting the first bypass valve 61, the second bypass valve 64, and the atmospheric release valve 63 when a turbine trips or when steam consumption is reduced is not limited to application to a power plant in which multiple steam turbines (high-pressure turbine 21, low-pressure turbine 22) are connected via a low-pressure boiler 12, as shown in Figures 1 to 7. For example, a similar method can be applied to a power plant equipped with a single steam turbine 21a, as shown in Figure 8.

[0097] 8 , when a turbine trips or steam consumption rate decreases, the need for atmospheric release is determined based on whether the main steam flow rate F0 supplied from the main steam line 501 exceeds a steam acceptance constraint downstream of the bypass line 503a (for example, the processable amount C of the condenser 41).Then, the flow rates of the main steam to be flowed toward the bypass line 503a and the atmospheric release line 505 and the flow rate of cooling water to be injected from the water injection line 504a are determined, and the openings of the bypass valve 61a, the water injection valve 62a, and the atmospheric release valve 63 are directly controlled. Note that, for convenience of illustration, a single-stage steam turbine 21a is illustrated in FIG. 8 , but a multi-stage steam turbine may also be used.

[0098] Furthermore, when the main steam flow rate F0 supplied from the main steam line 501 exceeds the flow rate consumed by the steam turbines 21, 22, and 21a, it is not essential to adjust the opening of the bypass valves 61, 64, and 61a to avoid atmospheric release. During a turbine trip or when steam consumption is low, a minimum release flow rate F4' to be released into the atmosphere may be determined in advance, prioritizing stable operation of the power plant. Then, the valve openings Q1 to Q5 may be determined by calculating the steam balance for the main steam at a flow rate F0-F4', obtained by subtracting the minimum release flow rate F4' from the main steam flow rate F0, using the method described with reference to FIGS. 4 to 8. According to this method, for example, in the case shown in FIG. 4, the atmospheric release flow rate is F4' > 0, and in the case shown in FIG. 5, the atmospheric release flow rate is F4 + F4'.

[0099] 1, 2, and 4 to 8 illustrate the configuration of the power plant in a simplified manner. In reality, steam may be extracted from intermediate stages of the steam turbines 21, 22, and 21a or from the bypass lines 503, 509, and 503a and consumed within the power plant. In such cases, the steam balance described with reference to FIGS. 4 to 8 (the consumption flow rate of each steam turbine 21, 22, and 21a, the steam flow rate flowing into each bypass line 503, 509, and 503a, the water injection flow rate, comparison with the intake constraint, etc.) may be calculated taking into account the flow rate of steam extracted to the outside. In this case, the flow rate of steam extracted to the outside may be measured by a flow meter, or a predetermined fixed value may be used.

[0100] Furthermore, in each of the above-described embodiments, a case has been described in which an opening adjustment step is performed to adjust the openings of the bypass valves 61, 64 and the atmospheric release valve 63 based on the results of an operating state determination step that determines whether the high-pressure turbine 21, the low-pressure turbine 22, and the steam turbine 21a are in a predetermined unsteady operating state (turbine trip, load rejection, station islanding, or the rate of decrease in the required steam flow rate within a predetermined time exceeds a predetermined value). However, it is not essential to perform the operating state determination step in order to perform the opening adjustment step.

[0101] For example, the opening degree adjustment step may be performed when it is determined that the supply steam flow rate of the main steam greatly exceeds the flow rate of the main steam consumed in the high-pressure turbines 21, 21 a. Here, an example of "greatly exceeding the flow rate of the main steam consumed in the high-pressure turbines 21, 21 a" can be a case where the supply steam flow rate F0 of the main steam is F0≧2.0F1 with respect to the flow rate F1 of the main steam flowing through the high-pressure turbine flow steam line 502 (high-pressure turbine flow rate), for example, where the supply steam flow rate F0 is 2 to 3 times the main steam flow rate F1.

[0102] 11 High-pressure boiler 12 Low-pressure boiler 21 High-pressure turbine 21a Steam turbine 22 Low-pressure turbine 31 Generator 32 Reducer 41 Condenser 42 Condensate drum 43 Liquid feed pump 501 Main steam line 502 High-pressure turbine steam line 503 First bypass line 503a Bypass line 504 First water injection line 504a Water injection line 505 Atmospheric release line 506 High-pressure turbine exhaust line 507 Low-pressure steam line 508 Low-pressure turbine steam line 509 Second bypass line 510 Second water injection line 511 Low-pressure turbine exhaust line 512 Pure liquid feed line 61 First bypass valve 61a Bypass valve 62 First water injection valve 62 Water injection valve 63 Atmospheric release valve 64 Second bypass valve 65 Second water injection valve 7 DCS

Claims

1. A method for operating a steam turbine power plant including: a steam turbine connected to a generator; a main steam line provided upstream of the steam turbine; a bypass line branching off from the main steam line to allow at least a portion of the steam in the main steam line to bypass the steam turbine, the bypass line having an adjustable bypass valve whose opening is adjustable; and an atmosphere discharge line branching off from the main steam line to discharge at least a portion of the steam in the main steam line to the atmosphere, the atmosphere discharge valve whose opening is adjustable, the method comprising: a supply steam flow rate specifying step for specifying a supply steam flow rate in the main steam line upstream of the bypass line and the atmosphere discharge line; a steam turbine operating state determination step for determining whether the steam turbine is in a predetermined non-steady operating state; and an opening adjustment step for adjusting the openings of the bypass valve and the atmosphere discharge valve in accordance with the supply steam flow rate when it is determined in the steam turbine operating state determination step that the steam turbine is in the predetermined non-steady operating state.

2. A method for operating a steam turbine power plant as described in claim 1, wherein the steam turbine operating state determination step determines that the steam turbine is in the predetermined non-steady operating state based on either a turbine trip signal issued during an emergency shutdown of the steam turbine, a load shedding command signal issued when the load on the generator is shedding, or an on-site isolated operation transition command signal issued when the electricity generated by the generator is consumed only within the business premises where the steam turbine power plant is installed.

3. A method for operating a steam turbine power plant as described in claim 1, wherein the steam turbine operating state determination step determines that the steam turbine is in the predetermined non-steady operating state when the supply steam flow rate exceeds the steam flow rate required by the steam turbine by a predetermined value or more, or when the rate of decrease in the steam flow rate required by the steam turbine within a predetermined time period exceeds a predetermined value or more.

4. A method for operating a steam turbine power plant according to any one of claims 1 to 3, wherein a turbine-row steam line connected to the steam turbine is provided downstream of the branch point of the main steam line with the bypass line and the branch point with the atmospheric release line, and a turbine-row valve whose opening is adjustable is provided in the turbine-row steam line, and the steam flow rate specifying step specifies the supply steam flow rate based on the opening of the bypass valve, the opening of the atmospheric release valve, and the opening of the turbine-row valve.

5. A method for operating a steam turbine power plant according to any one of claims 1 to 4, wherein the steam turbine power plant has a pressure gauge for measuring the steam pressure upstream of the steam turbine, and further includes a first pressure control step for adjusting the opening of the bypass valve when the steam pressure upstream of the steam turbine exceeds a first predetermined pressure.

6. A method for operating a steam turbine power plant according to any one of claims 1 to 5, wherein the steam turbine power plant has a pressure gauge for measuring the steam pressure upstream of the atmosphere release valve, and further includes a second pressure control step for adjusting the opening of the atmosphere release valve when the steam pressure upstream of the atmosphere release valve exceeds a second predetermined pressure.

7. A method for operating a steam turbine power plant according to any one of claims 1 to 6, wherein the atmospheric release valve is in a closed state when the steam turbine is in a steady operating state, and the opening adjustment step opens the bypass valve in preference to the atmospheric release valve, and adjusts the opening of the atmospheric release valve so as to release steam that exceeds the acceptance constraint downstream of the bypass line into the atmosphere.

8. A method for operating a steam turbine power plant as described in claim 7, wherein a water injection line having an adjustable opening water injection valve is connected to the bypass line for injecting cooling water to lower the temperature of the steam flowing through the bypass line, and the acceptance constraint is determined based on the total flow rate of the steam flowing from the main steam line into the bypass line and the cooling water injected from the water injection line.

9. A method for operating a steam turbine power plant as described in claim 8, wherein the opening of the water injection valve is set so that when the bypass valve is opened in the opening adjustment step, cooling water is injected at a flow rate that keeps the temperature of the steam flowing through the bypass line downstream of the cooling water injection position below a preset temperature constraint, based on the supply steam flow rate identified in the supply steam flow rate identification step and the temperature of the main steam.

10. A method for operating a steam turbine power plant according to claim 7, wherein the downstream end of the bypass line is connected to a condenser, and the acceptance constraint is the amount of steam that can be processed per unit time by the condenser.

11. A method for operating a steam turbine power plant according to any one of claims 1 to 10, wherein the downstream side of the bypass line is connected to a boiler that heats steam received via an outlet line of the steam turbine.

12. A method for operating a steam turbine power plant according to any one of claims 1 to 11, wherein the steam turbine power plant comprises: a low-pressure turbine to which low-pressure steam discharged from the steam turbine is supplied via a low-pressure steam line and to which steam discharged from the bypass line is supplied via the low-pressure steam line; and a low-pressure steam bypass line provided to allow at least a portion of the low-pressure steam in the low-pressure steam line to bypass the low-pressure turbine and have a low-pressure bypass valve whose opening is adjustable; wherein the steam turbine operating state determination step determines whether the low-pressure turbine is in an unsteady operating state in addition to the steam turbine; and wherein the opening adjustment step adjusts the opening of the low-pressure steam bypass valve in addition to the bypass valve and the atmospheric release valve.

13. A method for operating a steam turbine power plant as described in claim 2, wherein, when the steam turbine operating state determination step determines that the plant is in the unsteady operating state based on the turbine trip signal, the opening adjustment step adjusts the openings of the bypass valve and the atmospheric release valve so that the entire amount of steam supplied from the main steam line flows into at least one of the bypass line and the atmospheric release line.

14. A method for operating a steam turbine power plant as described in claim 2, wherein, when the steam turbine operating state determination step determines that the plant is in the unsteady operating state based on the load shedding command signal or the stationary isolated operation transition command signal, the opening adjustment step adjusts the openings of the bypass valve and the atmospheric release valve so that the surplus steam obtained by subtracting the flow rate of steam supplied to the steam turbine from the flow rate of steam supplied from the main steam line flows into at least one of the bypass line and the atmospheric release line.

15. A method for operating a steam turbine power plant comprising: a steam turbine connected to a generator; a main steam line provided upstream of the steam turbine; a bypass line branching off from the main steam line for allowing at least a portion of the steam in the main steam line to bypass the steam turbine and having an adjustable bypass valve; and an atmospheric discharge line branching off from the main steam line for dissipating at least a portion of the steam in the main steam line to the atmosphere and having an adjustable atmospheric discharge valve, the method comprising: a supply steam flow rate specifying step for specifying a supply steam flow rate in the main steam line upstream of the bypass line and the atmospheric discharge line; and an opening adjustment step for adjusting the opening rates of the bypass valve and the atmospheric discharge valve in accordance with the supply steam flow rate when the supply steam flow rate significantly exceeds the flow rate of main steam consumed by the steam turbine.

16. A storage medium storing a computer program for operating a control device that controls the operation of the steam turbine power plant, wherein the computer program is a storage medium having a group of steps organized to execute the steam turbine power plant operation method described in any one of claims 1 to 15.

17. A steam turbine power plant comprising: a steam turbine connected to a generator; a main steam line provided upstream of the steam turbine; a bypass line branching from the main steam line to allow at least a portion of the steam in the main steam line to bypass the steam turbine and having an adjustable bypass valve; an atmosphere release line branching from the main steam line to release at least a portion of the steam in the main steam line to the atmosphere and having an adjustable atmosphere release valve; and a control unit, wherein the control unit outputs control signals to execute the following: a supply steam flow rate specifying step for specifying a supply steam flow rate in the main steam line upstream of the bypass line and the atmosphere release line; a steam turbine operating state determination step for determining whether the steam turbine is in a predetermined non-steady operating state; and an opening adjustment step for adjusting the openings of the bypass valve and the atmosphere release valve in accordance with the supply steam flow rate if it is determined in the steam turbine operating state determination step that the steam turbine is in the predetermined non-steady operating state.

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