Water supply control system, water supply control device, water supply control method and program

Abstract

To provide a system for controlling water supply of a steam generator.SOLUTION: A water supply control system includes a main water supply flow passage constituting a water supply system of a steam generator, a main water supply valve, a bypass flow passage of the main water supply flow passage, a main water supply bypass valve, and a water supply control device. The water supply control device calculates a first target opening on the basis of a steam flow rate supplied to a steam turbine from the steam generator, closes the main water supply bypass valve so that the valve opening becomes the first target opening, and calculates a second target opening to compensate a water supply flow rate which is decreased by closing of the main water supply bypass valve, and places the main water supply valve and the main water supply bypass valve under an open state by opening the closed main water supply valve so that the opening becomes the second target opening.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a water supply control system, a water supply control device, a water supply control method, and a program for a steam generator. [Background technology]

[0002] In a nuclear power plant, the feedwater flow path of a steam generator is provided with a bypass flow path in addition to a main feedwater flow path. The main feedwater flow path is provided with a main feedwater valve, and the bypass flow path is provided with a main feedwater bypass valve. Conventionally, under high load conditions where the steam flow rate from the steam generator to the turbine is high, the main feedwater bypass valve is closed to supply cooling water to the steam generator through the main feedwater flow path. Under low load conditions where the steam flow rate is low, the main feedwater valve is closed to supply cooling water to the steam generator through the bypass flow path (see Patent Document 1). In this manner, conventional control switches between the main feedwater flow path and the bypass flow path depending on the load, and cooling water is supplied through either one of the flow paths. Meanwhile, for plants requiring a larger feedwater flow rate, methods of supplying cooling water to the steam generator using both the main feedwater flow path and the bypass flow path are being considered. One possible method of supplying cooling water using the main feedwater flow path and the bypass flow path is to gradually open the main feedwater valve while keeping the main feedwater bypass valve open during the load increase process. However, with this method, the water supply flow rate may fluctuate when the main water supply valve is slightly open, which may result in unstable water supply control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-253007 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a need for a method for supplying water to a steam generator by controlling both the main feedwater valve and the main feedwater bypass valve to an open state while suppressing fluctuations in the feedwater flow rate.

[0005] The present disclosure provides a water supply control system, a water supply control device, a water supply control method, and a program that can solve the above problems. [Means for solving the problem]

[0006] The feedwater control system of the present disclosure includes a main feedwater flow path that constitutes a feedwater system that supplies cooling water to a steam generator, a main feedwater valve that is provided in the main feedwater flow path, a main feedwater bypass flow path that constitutes the feedwater system and bypasses the main feedwater flow path, and a valve that is provided in the main feedwater bypass flow path. The valve capacity is smaller than that of the main water supply valve. a main feedwater bypass valve; and a feedwater control device that controls the main feedwater valve and the main feedwater bypass valve to control the feedwater flow rate of the cooling water, wherein the feedwater control device calculates a first target opening based on the steam flow rate supplied from the steam generator to the steam turbine, closes the main feedwater bypass valve to achieve the first target opening, calculates a second target opening that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, opens the main feedwater valve that is in a closed state to achieve the second target opening, and closes the main feedwater valve and the main feedwater bypass valve to an open state. The main feedwater bypass valve is not fully closed regardless of the steam flow rate.

[0007] The feedwater control device of the present disclosure includes a main feedwater flow path that supplies cooling water to a steam generator, a main feedwater valve provided in the main feedwater flow path, a main feedwater bypass flow path that bypasses the main feedwater flow path, and a The valve capacity is smaller than that of the main water supply valve. a main feedwater bypass valve, and a feedwater control device that controls a feedwater flow rate of the cooling water to the steam generator by controlling the main feedwater valve and the main feedwater bypass valve, the feedwater control device calculates a first target opening based on a steam flow rate supplied from the steam generator to a steam turbine, closes the main feedwater bypass valve to achieve the first target opening, calculates a second target opening that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, opens the main feedwater valve that is in a closed state to achieve the second target opening, and closes the main feedwater valve and the main feedwater bypass valve to an open state. The main feedwater bypass valve is not fully closed regardless of the steam flow rate.

[0008] The feedwater control method of the present disclosure includes a main feedwater flow path that supplies cooling water to a steam generator, a main feedwater valve provided in the main feedwater flow path, a main feedwater bypass flow path that bypasses the main feedwater flow path, and a The valve capacity is smaller than that of the main water supply valve. a main feedwater bypass valve, and a feedwater control method for controlling a feedwater flow rate by controlling the main feedwater valve and the main feedwater bypass valve in a feedwater system including the main feedwater bypass valve, the method comprising: calculating a first target opening based on a steam flow rate supplied from the steam generator to a steam turbine; closing the main feedwater bypass valve so as to achieve the first target opening; calculating a second target opening that compensates for a feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve; opening the main feedwater valve that is in a closed state so as to achieve the second target opening; The main feedwater bypass valve is not fully closed regardless of the steam flow rate.

[0009] The program of the present disclosure includes causing a computer to execute a program for controlling a main feedwater flow path for supplying cooling water to a steam generator, a main feedwater valve provided in the main feedwater flow path, a main feedwater bypass flow path that bypasses the main feedwater flow path, and a The valve capacity is smaller than that of the main water supply valve. a main feedwater bypass valve, and a computer that controls the feedwater flow rate by controlling the main feedwater valve and the main feedwater bypass valve, calculates a first target opening based on the steam flow rate supplied from the steam generator to the steam turbine, closes the main feedwater bypass valve to achieve the first target opening, calculates a second target opening that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, opens the main feedwater valve that is in a closed state to achieve the second target opening, and closes the main feedwater valve and the main feedwater bypass valve to an open state. The main feedwater bypass valve is not fully closed regardless of the steam flow rate. Execute the process. [Effects of the Invention]

[0010] According to the above-described water supply control system, water supply control device, water supply control method, and program, water can be supplied to the steam generator by opening both the main water supply valve and the main water supply bypass valve. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a steam generator feedwater control system according to an embodiment; [Figure 2] FIG. 2 is a block diagram showing an example of a water supply control device according to an embodiment. [Figure 3] FIG. 10 is a diagram illustrating an example of control when a load increases according to the embodiment. [Figure 4A] FIG. 3 is a first diagram showing an example of a function used to calculate an opening degree according to the embodiment. [Figure 4B] FIG. 10 is a second diagram showing an example of a function used to calculate an opening degree according to the embodiment. [Figure 4C] FIG. 10 is a third diagram showing an example of a function used to calculate an opening degree according to the embodiment. [Figure 5] FIG. 10 is a diagram illustrating an example of control during a load drop according to the embodiment. [Figure 6A] 10 is a flowchart illustrating an example of a process when a load increases according to the embodiment. [Figure 6B] 10 is a flowchart illustrating an example of a process performed when a load drops according to the embodiment. [Figure 7] A diagram showing an example of the hardware configuration of a water supply control device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The water supply control system of the present disclosure will be described below with reference to FIGS. <Embodiment> (composition) The configuration of the water supply control system of this embodiment will be described with reference to FIGS. FIG. 1 shows a schematic diagram of a steam generator feedwater control system in a pressurized water reactor (PWR) nuclear power plant. The feedwater control system 100 includes a steam generator 1, a steam turbine 4, a condenser 5, a secondary cooling loop 6, and a feedwater control device 10. A primary cooling loop 2 is connected to the steam generator 1. The primary cooling loop 2 forms a flow path for circulating primary cooling water between the nuclear reactor (not shown) and the steam generator 1. The primary cooling loop 2 has a primary cooling pump P1 for circulating the primary cooling water. The steam generator 1 heats the primary cooling water circulating through the primary cooling loop 2 to generate steam. The generated steam is supplied to the steam turbine 4 through a steam supply flow path 3. The steam turbine 4 is driven to rotate using the thermal energy of the steam supplied from the steam generator 1. The rotating shaft of the steam turbine 4 is connected to a generator (not shown), and the rotational drive of the steam turbine 4 causes the generator (not shown) to generate electricity. The secondary cooling loop 6 forms a flow path for circulating secondary cooling water between the steam generator 1 and the steam turbine 4. The secondary cooling loop 6 includes a steam supply flow path 3, a main feedwater flow path 7, and a main feedwater bypass flow path 8. The condenser 5 is disposed downstream of the steam turbine 4 in the secondary cooling loop 6 and condenses the steam into water after it has performed work in the steam turbine 4. The main feedwater flow path 7 has a pump P2 for circulating secondary cooling water. The pump P2 circulates the water (secondary cooling water) condensed in the condenser 5 between the steam generator 1 and the steam turbine 4. The main feedwater bypass flow path 8 branches off from the main feedwater flow path 7 at a branch point 71 downstream of the pump P2 in the main feedwater flow path 7 in the flow direction of the secondary cooling water. A main feedwater bypass valve V2 is provided in the main feedwater bypass flow path 8. The flow rate of secondary cooling water flowing through the main feedwater bypass flow path 8 is controlled by adjusting the opening of the main feedwater bypass valve V2. A main feedwater valve V1 is provided downstream of the branch point 71 in the main feedwater flow path 7. The flow rate of the secondary cooling water flowing through the main feedwater flow path 7 is controlled by adjusting the opening of the main feedwater valve V1. The main feedwater bypass flow path 8 is connected to (confluent with) the main feedwater flow path 7 at a confluence point 72 downstream of the main feedwater valve V1.The main feedwater valve V1 has a larger valve capacity than the main feedwater bypass valve V2, making it difficult to adjust its opening precisely. Furthermore, the main feedwater valve V1 experiences fluctuations in flow rate when its opening is small. On the other hand, the main feedwater valve V1 has the advantage of being able to control large flow rates.

[0013] The steam generator 1 is provided with a sensor c1 that measures the cooling water level. The steam supply passage 3 is provided with a sensor c2 that measures the flow rate of steam supplied from the steam generator 1 to the steam turbine 4. The main feedwater passage 7 is provided with a sensor c3 that measures the feedwater flow rate of secondary cooling water returned to the steam generator 1 via the secondary cooling loop 6. These sensors c1 to c3 are connected to a feedwater control device 10. The water level, steam flow rate, and feedwater flow rate measured by the sensors c1 to c3 are sent to the feedwater control device 10 and used to control the feedwater flow rate of secondary cooling water supplied to the steam generator 1, i.e., to control the opening of the main feedwater valve V1 and the main feedwater bypass valve V2. The steam flow rate measured by the sensor c2 is positively correlated with the power generation load of the generator (not shown) and is used as an index of the load (for example, the power generation load and the steam flow rate can be converted into each other). In other words, feedwater control is performed to achieve a steam flow rate corresponding to the power generation load. There is also a positive correlation between the steam flow rate measured by the sensor c2 and the feedwater flow rate measured by the sensor c3.

[0014] Next, the function and configuration of the feedwater control device 10 will be described. The feedwater control device 10 controls the flow rate of feedwater supplied to the steam generator 1. FIG. 2 is a block diagram showing an example of a feedwater control device according to an embodiment. The feedwater control device 10 includes a sensor data acquisition unit 11, an input reception unit 12, a control unit 13, an output unit 14, and a memory unit 15. The sensor data acquisition unit 11 acquires the measurement values ​​measured by the sensors c1 to c3. The input receiving unit 12 receives input from a user. For example, the input receiving unit 12 receives input of an operation to instruct the start of automatic switching control of the main water feed valve V1 and the main water feed bypass valve V2. The automatic switching control of the main water feed valve V1 and the main water feed bypass valve V2 will be described later.

[0015] The control unit 13 controls the operation of the secondary cooling loop 6. For example, the control unit 13 starts and stops the pump P2 and controls the opening degrees of the main feedwater valve V1 and the main feedwater bypass valve V2. In particular, the control unit 13 performs automatic switching control of the main feedwater valve V1 and the main feedwater bypass valve V2 according to this embodiment. The automatic switching control is control that switches between a state in which only the main feedwater bypass valve V2 is open and a state in which both the main feedwater valve V1 and the main feedwater bypass valve V2 are open, depending on the power generation load of the nuclear power plant (the load of the generator, not shown). The control unit 13 includes an opening degree calculation unit 131, a main feedwater valve control unit 132, and a main feedwater bypass valve control unit 133.

[0016] The opening calculation unit 131 calculates the target openings of the main feedwater valve V1 and the main feedwater bypass valve V2. The main water supply valve control unit 132 controls the opening degree of the main water supply valve V1 based on the target opening degree of the main water supply valve V1 calculated by the opening degree calculation unit 131. The main feedwater bypass valve control unit 133 controls the opening degree of the main feedwater bypass valve V2 based on the target opening degree of the main feedwater bypass valve V2 calculated by the opening degree calculation unit 131.

[0017] The output unit 14 outputs various pieces of information to a display device or an electronic file. The storage unit 15 stores various information, such as the measurement values ​​acquired by the sensor data acquisition unit 11, functions F1 to F3 used to calculate the opening degrees of the main feedwater valve V1 and the main feedwater bypass valve V2, and threshold values.

[0018] (Control of main feedwater valve V1 and main feedwater bypass valve V2) Next, automatic switching control of the main feedwater valve V1 and the main feedwater bypass valve V2 will be described with reference to Figures 3 to 5. Automatic switching control refers to opening both the main feedwater valve V1 and the main feedwater bypass valve V2 when the load increases, from a state in which the main feedwater valve V1 is closed and the main feedwater bypass valve V2 is open. When the load decreases, automatic switching control refers to fully closing the main feedwater valve V1 while leaving the main feedwater bypass valve V2 open, from a state in which both the main feedwater valve V1 and the main feedwater bypass valve V2 are open. In conventional control, when the load on the generator (not shown) is low, the main feedwater bypass valve V2 is opened and the main feedwater valve V1 is closed. When the load increases, the main feedwater valve V1 is opened and the main feedwater bypass valve V2 is closed. In contrast, in this embodiment, when the load is low, the main feedwater bypass valve V2 is opened and the main feedwater bypass valve V1 is closed, as in conventional control. During high loads, both the main feedwater valve V1 and the main feedwater bypass valve V2 are opened to allow a larger amount of secondary cooling water to be supplied to the steam generator 1. During automatic switching, the main feedwater valve V1 and the main feedwater bypass valve V2 are controlled to be open while suppressing fluctuations in the feedwater flow rate.

[0019] [When load increases] FIG. 3 is a diagram illustrating an example of control when the load increases according to the embodiment. In the upper diagram 31 of Figure 3, the vertical axis represents the feedwater flow rate, and the horizontal axis represents time. In the lower diagram 32 of Figure 3, the vertical axis represents the main feedwater bypass valve control signal (opening command value of the main feedwater bypass valve V2) or the main feedwater valve control signal (opening command value of the main feedwater bypass valve V1), and the horizontal axis represents time. The same position on the horizontal axis in the upper diagram 31 and the lower diagram 32 represents the same time. The solid line in graph g1 represents the opening of the main feedwater bypass valve V2 under the control of this embodiment, and the solid line in graph g2 represents the opening of the main feedwater valve V1 under the control of this embodiment. The dashed line portion of graph g1 represents the opening of the main feedwater bypass valve V2 under conventional control, and the dashed line portion of graph g2 represents the opening of the main feedwater valve V1 under conventional control. Graph g3 represents the feedwater flow rate measured by sensor c3. At time t0, the main feedwater bypass valve V2 (graph g1) is open (for example, 70%), and the opening of the main feedwater valve V1 (graph g2) is fully closed (0%). In this state, the opening of the main feedwater bypass valve V2 is controlled so that the liquid phase water level in the steam generator 1 measured by the sensor c1 is within a predetermined range and the steam flow rate measured by the sensor c1 is a flow rate corresponding to the power generation load.

[0020] Here, in preparation for an increase in the power generation load, the user instructs the feedwater control device 10 to start automatic switching control (automatic switching control related to load increase) at time t1. Then, based on the current (pre-switching) steam flow rate measured by sensor c2, the opening calculation unit 131 calculates the target opening of the main feedwater bypass valve V2 by referencing function F1, which defines the relationship between the steam flow rate and the main feedwater bypass valve opening, as exemplified in Fig. 4A. For example, when the pre-switching steam flow rate measured by sensor c2 is 20% (the steam flow rate at rated output is 100%), the opening calculation unit 131 calculates the target opening of the main feedwater bypass valve V2 to be 20%.

[0021] Next, the opening calculation unit 131 refers to a function F2 that defines the relationship between the main feedwater bypass valve opening illustrated in Fig. 4B and the feedwater flow rate of secondary cooling water flowing through the main feedwater bypass flow path 8 (passing through the main feedwater bypass valve V2), and calculates the feedwater flow rate through the main feedwater bypass flow path 8 when the main feedwater bypass valve V2 is set to the above-mentioned target opening. For example, when the target opening of the main feedwater bypass valve V2 is 20%, the opening calculation unit 131 calculates the feedwater flow rate passing through the main feedwater bypass valve V2 to be 100 (tons / h).

[0022] Next, the opening calculation unit 131 subtracts the flow rate of secondary cooling water borne by the main feedwater bypass flow path 8 from the current (pre-switching) feedwater flow rate to calculate the feedwater flow rate that should be borne by the main feedwater flow path 7 (the feedwater flow rate that should be supplied through the main feedwater valve V1). For example, if the feedwater flow rate before switching measured by sensor c3 is 250 (tons / h), the opening calculation unit 131 calculates the feedwater flow rate that should be borne by the main feedwater flow path 7 as follows: 250 - 100 (tons / h) = 150 (tons / h). Next, the opening calculation unit 131 calculates the target opening of the main feedwater valve V1 by referring to function F3, which defines the relationship between the main feedwater valve opening and the feedwater flow rate of secondary cooling water passing through the main feedwater valve V1, as shown in FIG. 4C. For example, the opening calculation unit 131 calculates a target opening of 15% of the main feedwater valve V1 required to flow 150 (tons / h), by referring to function F3, as shown in FIG. 4C. This calculates the target opening of the main water supply valve V1 after switching to 15% and the target opening of the main water supply bypass valve V2 to 20%, compared to the opening of the main water supply valve V1 of 0% and the opening of the main water supply bypass valve V2 of 70% before switching.

[0023] Next, the main feedwater valve control unit 132 begins opening the main feedwater valve V1 at time t1, opening it at a constant speed to the target opening of 15%. The speed at which the main feedwater valve V1 is opened is predetermined. The main feedwater bypass valve control unit 133 begins closing the main feedwater bypass valve V2 at time t2, reducing the opening of the main feedwater bypass valve V2 at a constant speed to the target opening of 20%. In the example of Figure 3, the target opening of 15% for the main feedwater valve V1 and the target opening of 20% for the main feedwater bypass valve V2 are achieved at time t3, and then, as the load increases, the openings of the main feedwater valve V1 and the main feedwater bypass valve V2 begin to increase at time t4. From time t4 onwards, opening control is performed to achieve the required load using logic different from that used for the automatic switching control from times t1 to t4. As a result, under high load conditions, both the main feedwater valve V1 and the main feedwater bypass valve V2 can be opened, and a larger volume of secondary cooling water can be supplied to the steam generator 1 compared to conventional water supply systems in which only the main feedwater valve V1 is open. Furthermore, by opening the main feedwater bypass valve V2, the load on the main feedwater valve V1 is not placed solely on the main feedwater valve V1, and the load on the main feedwater valve V1 can be reduced.

[0024] Furthermore, in this embodiment, the main feedwater valve V1 is not left slightly open and gradually opened, but is instead increased to the target opening of 15%. This suppresses fluctuations in the feedwater flow rate due to automatic switching control, as shown in graph g3 in Figure 31, and allows both the main feedwater valve V1 and the main feedwater bypass valve V2 to be opened with only relatively small fluctuations. As shown in graph g3, by opening both the main feedwater valve V1 and the main feedwater bypass valve V2, fluctuations in the feedwater flow rate can be quickly stabilized. For comparison with the automatic switching control of this embodiment, control was performed in which the main feedwater valve V1 was gradually opened while the main feedwater bypass valve V2 was left open. It was confirmed that larger fluctuations occurred with shorter cycles than those shown in graph g3. This is thought to be because fluctuations in the feedwater flow rate occurred during the process of gradually opening the main feedwater valve V1 because the main feedwater valve V1 was left slightly open.

[0025] [When load drops] FIG. 5 is a diagram illustrating an example of control during a load drop according to the embodiment. The vertical axis of Figure 5 represents the main feedwater bypass valve control signal (opening command value of the main feedwater bypass valve V1) or the main feedwater valve control signal (opening command value of the main feedwater bypass valve V2), and the horizontal axis represents time. The solid line in graph g1 represents the opening of the main feedwater bypass valve V2 under the control of this embodiment, and the solid line in graph g2 represents the opening of the main feedwater valve V1 under the control of this embodiment. The dashed line in graph g1 represents the opening of the main feedwater bypass valve V2 under conventional control, and the dashed line in graph g2 represents the opening of the main feedwater valve V1 under conventional control. In conventional control, as shown by the dashed line in graph g1, switching control is initiated from a fully closed state of the main feedwater bypass valve V2, whereas in this embodiment, automatic switching control is initiated from a state in which the main feedwater bypass valve V2 is somewhat open. The main feedwater valve V1 is changed from an open state to a fully closed state in both conventional control and the automatic switching control of this embodiment, but the opening of the main feedwater valve V1 is reduced by the amount that the main feedwater bypass valve V2 is open before the switching begins. For example, at time t1, the user instructs the feedwater control device 10 to start automatic switching control (automatic switching control related to load drop). The opening calculation unit 131 then calculates the opening of the main feedwater bypass valve V2 after the switching. The target opening of the main feedwater valve v1 is 0%. For example, the opening calculation unit 131 may calculate the target opening of the main feedwater bypass valve V2 based on a steam flow rate based on a target load by referencing a function (not shown) that defines the relationship between the steam flow rate and the main feedwater bypass valve opening.

[0026] Next, the main feedwater valve control unit 132 begins closing the main feedwater valve V1 at time t2, and closes the main feedwater valve V1 at a constant speed until the target opening degree reaches 0%. The speed at which the main feedwater valve V1 is closed is predetermined. The main feedwater bypass valve control unit 133 begins opening the main feedwater bypass valve V2 at time t1, and increases the opening degree of the main feedwater bypass valve V2 at a constant speed until the target opening degree reaches 0%. When the switching is completed at time t4, opening degree control of the main feedwater bypass valve V2 is executed using logic different from that of the automatic switching control from time t1 to t4. Even when the load drops, the main feedwater valve V1 and the main feedwater bypass valve V2 are controlled so that the feedwater flow rate during the automatic switching control remains constant. Furthermore, even when the load drops, the main feedwater valve V1 is fully closed without being slightly open, thereby suppressing fluctuations in the feedwater flow rate.

[0027] (operation) Next, the operation of the water supply control system 100 will be described with reference to FIGS. 6A and 6B. [When load increases] FIG. 6A is a flowchart illustrating an example of processing when a load increases according to the embodiment. The sensor data acquiring unit 11 acquires the measurement values ​​measured by the sensors c1 to c3 (step S1). For example, the sensor data acquiring unit 11 acquires the water level measured by the sensor c1, the steam flow rate measured by the sensor c2, and the feedwater flow rate measured by the sensor c3, and records them in the storage unit 15.

[0028] Next, the control unit 13 determines whether or not there is a switching instruction for the main water supply valve V1 and the main water supply bypass valve V2 (an instruction to execute automatic switching control in response to an increase in load) (step S2). For example, if a user inputs an operation to instruct switching into the water supply control device 10, the input receiving unit 12 receives this operation and notifies the control unit 13 that a switching instruction has been issued. The control unit 13 determines whether or not there is a switching instruction based on the notification from the input receiving unit 12. If there is no switching instruction (step S2; No), the process from step S1 is repeated. If there is a switching instruction (step S2; Yes), the control unit 13 determines whether or not the water supply flow rate acquired in step S1 is within a predetermined allowable range (step S3). If the water supply flow rate is too low or too high, it is not appropriate to execute automatic switching control, so an allowable range for the water supply flow rate is preset in the memory unit 15. The control unit 13 determines whether or not the water supply flow rate measured by the sensor c3 is within an allowable range. If the water supply flow rate exceeds the allowable range (step S3; No), the process is repeated from step S1. The output unit 14 outputs to a display device or the like that the water supply flow rate is not within the allowable range and therefore automatic switching control cannot be executed.

[0029] If the feedwater flow rate is within the allowable range (step S3; Yes), the control unit 13 determines to switch from a state in which the main feedwater valve V1 is closed and the main feedwater bypass valve V2 is open to a state in which both the main feedwater valve V1 and the main feedwater bypass valve V2 are open (step S4). The opening calculation unit 131 calculates the target opening after the switching (step S5). As described with reference to Figures 3 and 4A to 4C, the opening calculation unit 131 calculates the target opening of the main feedwater bypass valve V2 after the switching based on the steam flow rate before the switching and function F1 (Figure 4A). The opening calculation unit 131 also calculates the target opening of the main feedwater valve V1 after the switching based on the supply flow rate of secondary cooling water that should pass through the main feedwater valve V1 and be supplied to the steam generator 1 after the switching and function F3 (Figure 4C). Next, the main feedwater valve control unit 132 controls the main feedwater valve V1 to open at a constant speed to the target opening degree of the main feedwater valve V1, and the main feedwater bypass valve control unit 133 controls the main feedwater bypass valve V2 to open at a constant speed to the target opening degree of the main feedwater bypass valve V2 (step S6). The main feedwater valve control unit 132 determines whether the opening degree of the main feedwater valve V1 has reached the target opening degree, and the main feedwater bypass valve control unit 133 determines whether the opening degree of the main feedwater bypass valve V2 has reached the target opening degree. When the opening degree of the main feedwater valve V1 has reached the target opening degree, the main feedwater valve control unit 132 stops controlling the opening of the main feedwater valve V1 (step S7). When the opening degree of the main feedwater bypass valve V2 has reached the target opening degree, the main feedwater bypass valve control unit 133 stops controlling the closing of the main feedwater bypass valve V2 (step S7). This makes it possible to control both the main feedwater valve V1 and the main feedwater bypass valve V2 to an open state while suppressing fluctuations in the feedwater flow rate.

[0030] [When load drops] Next, the processing when the load drops will be described. Processing similar to that in Fig. 6A will be briefly described. Fig. 6B is a flowchart showing an example of the processing when the load drops according to the embodiment. The sensor data acquisition unit 11 acquires the measurement values ​​measured by the sensors c1 to c3 (step S11). Next, the control unit 13 determines whether or not there is a switching instruction for the main water supply valve V1 and the main water supply bypass valve V2 (an instruction to execute automatic switching control related to load drop) (step S12). If there is no switching instruction (step S12; No), the process from step S11 is repeated. If there is a switching instruction (step S12; Yes), the control unit 13 determines whether the water supply flow rate acquired in step S1 is within a predetermined allowable range (step S13). If the water supply flow rate exceeds the allowable range (step S13; No), the output unit 14 outputs a warning, and the process from step S11 is repeated.

[0031] If the feedwater flow rate is within the allowable range (step S13; Yes), the control unit 13 determines to switch the main feedwater valve V1 and the main feedwater bypass valve V2 from an open state to a state in which the main feedwater valve V1 is closed and the main feedwater bypass valve V2 is open (step S14). The opening calculation unit 131 calculates a target opening after the switching (step S15). For the main feedwater valve V1, the opening calculation unit 131 sets the target opening to 0%. For the main feedwater bypass valve V2, for example, the opening calculation unit 131 calculates the target opening of the main feedwater bypass valve V2 based on the steam flow rate corresponding to the target load after the switching. For example, a function F4 (not shown) that defines the relationship between the steam flow rate and the main feedwater bypass valve opening is registered in the memory unit 15, and the opening calculation unit 131 references the function F4 based on the steam flow rate corresponding to the target load to calculate the target opening of the main feedwater bypass valve V2 after the switching. 4A defines the opening of the main feedwater bypass valve V2 when both the main feedwater valve V1 and the main feedwater bypass valve V2 are open, whereas function F4, which is referenced in automatic switching control during load drop, defines the opening of the main feedwater bypass valve V2 when only the main feedwater bypass valve V2 is open. Therefore, for example, function F4 is set to a larger opening than that defined by function F1 for the same load (for example, a steam flow rate of 20%).

[0032] Next, the main feedwater valve control unit 132 controls the main feedwater valve V1 to be fully closed at a constant speed, and the main feedwater bypass valve control unit 133 controls the main feedwater bypass valve V2 to be opened at a constant speed to the target opening degree of the main feedwater bypass valve V2 (step S16). For example, the main feedwater valve control unit 132 closes the main feedwater valve V1 at a speed that can offset the increase in feedwater flow rate caused by opening the main feedwater bypass valve V2, so as to maintain a constant feedwater flow rate. The main feedwater valve control unit 132 determines whether the opening degree of the main feedwater valve V1 has reached the target opening degree (0%), and the main feedwater bypass valve control unit 133 determines whether the opening degree of the main feedwater bypass valve V2 has reached the target opening degree. When the opening degree of the main feedwater valve V1 has reached the target opening degree, the main feedwater valve control unit 132 stops controlling the opening of the main feedwater valve V1 (step S17). When the opening degree of the main feedwater bypass valve V2 reaches the target opening degree, the main feedwater bypass valve control unit 133 stops the control to close the main feedwater bypass valve V2 (step S17). This makes it possible to control the main feedwater valve V1 to the closed state while suppressing fluctuations in the feedwater flow rate.

[0033] 6A and 6B, the user issues a switching instruction (step S2 in FIG. 6A, step S12 in FIG. 6B), but the control unit 13 may automatically determine to perform automatic switching control related to a load increase if the steam flow rate measured by the sensor c2 increases from a steam flow rate of less than 20% when operating at rated load to 20% and the feedwater flow rate is within an allowable range (step S3; Yes). Similarly, the control unit 13 may determine to perform automatic switching control related to a load decrease if the steam flow rate decreases from a steam flow rate of more than 20% to 20% and the feedwater flow rate is within an allowable range (step S13; Yes).

[0034] 3 above, automatic switching control is performed when the load increases to a certain level, and then the load is increased using another control logic. However, automatic switching control may be performed while the load is increased. In this case, the opening calculation unit 131 may calculate the target openings of the main feedwater valve V1 and the main feedwater bypass valve V2 as follows. For example, the opening calculation unit 131 sets the target opening of the main feedwater bypass valve V2 using a target steam flow rate corresponding to the target load after switching and the function F1 of FIG. 4A, and calculates the feedwater flow rate passing through the main feedwater bypass valve V2 after switching based on the function F2 of FIG. 4B. The opening calculation unit 131 then calculates the target feedwater flow rate corresponding to the target load using, for example, a predetermined function that defines the relationship between the load and the feedwater flow rate, and calculates the feedwater flow rate passing through the main feedwater valve V1 to achieve the target feedwater flow rate by subtracting the feedwater flow rate passing through the main feedwater bypass valve V2 from the calculated target feedwater flow rate. Furthermore, the opening calculation unit 131 calculates the target opening of the main feedwater valve V1 using the calculated flow rate of water passing through the main feedwater valve V1 and the function F3 of FIG. 4C.

[0035] (effect) As described above, according to this embodiment, when the power generation load of the nuclear power plant reaches a certain level or more, both the main feedwater valve V1 and the main feedwater bypass valve V2 are controlled to an open state to supply water to the steam generator. This makes it possible to increase the feedwater flow rate under high loads compared to when water is supplied using only the main feedwater valve V1. Furthermore, when switching from a state in which only the main feedwater bypass valve V2 is open to opening both the main feedwater valve V1 and the main feedwater bypass valve V2, the main feedwater valve V1 is opened to a certain degree of opening without maintaining a slightly open state. This makes it possible to control both the main feedwater valve V1 and the main feedwater bypass valve V2 to an open state while preventing fluctuations in the feedwater flow rate due to the main feedwater valve V1, whose flow rate is unstable when in a slightly open state.

[0036] FIG. 7 is a diagram illustrating an example of a hardware configuration of a water supply control device according to an embodiment. The computer 900 includes a CPU 901, a main memory device 902, an auxiliary memory device 903, an input / output interface 904, and a communication interface 905. The water supply control device 10 described above is implemented in the computer 900. The functions described above are stored in the auxiliary memory device 903 in the form of a program. The CPU 901 reads the program from the auxiliary memory device 903, expands it in the main memory device 902, and executes the above processing in accordance with the program. The CPU 901 also allocates a memory area in the main memory device 902 in accordance with the program. The CPU 901 also allocates a memory area in the auxiliary memory device 903 for storing data being processed in accordance with the program.

[0037] A program for implementing all or part of the functions of the water supply control device 10 may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed to perform processing by each functional unit. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, if a WWW system is used, the term "computer system" also includes the homepage provision environment (or display environment). Furthermore, the term "computer-readable recording medium" refers to portable media such as CDs, DVDs, and USBs, as well as storage devices such as hard disks built into the computer system. Furthermore, if the program is distributed to the computer 900 via a communication line, the computer 900 that receives the program may load the program into the main storage device 902 and execute the above-described processing. Furthermore, the program may be for implementing part of the above-described functions, or may be capable of implementing the above-described functions in combination with a program already stored in the computer system.

[0038] As described above, several embodiments according to the present disclosure have been described, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as defined in the claims, as well as in the scope and spirit of the invention.

[0039] <Additional Notes> The water supply control system, water supply control device, water supply control method, and program described in each embodiment can be understood, for example, as follows.

[0040] (1) A feedwater control system 100 according to a first aspect includes a main feedwater passage 7 constituting a feedwater system that supplies cooling water to a steam generator 1, a main feedwater valve V1 provided in the main feedwater passage, a main feedwater bypass passage 8 constituting the feedwater system and bypassing the main feedwater passage, a main feedwater bypass valve V2 provided in the main feedwater bypass passage, and a feedwater control device 10 that controls the main feedwater valve and the main feedwater bypass valve to control the feedwater flow rate of the cooling water, wherein the feedwater control device calculates a first target opening based on the steam flow rate supplied from the steam generator to the steam turbine, closes the main feedwater bypass valve so as to achieve the first target valve opening, calculates a second target opening of the main feedwater valve so as to compensate for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, and opens the main feedwater valve, which is in a closed state, so as to achieve the second target opening, thereby opening the main feedwater valve and the main feedwater bypass valve. This makes it possible to control both the main water supply valve and the main water supply bypass valve to an open state while suppressing fluctuations in the water supply flow rate.

[0041] (2) A second aspect of the water supply control system is the water supply control system of (1), wherein the water supply control device opens the main water supply bypass valve and closes the main water supply valve when the load on the steam turbine is lower than a first threshold value, and when the load reaches the first threshold value from that state, closes the main water supply bypass valve to the first target valve opening degree and opens the main water supply valve to the second target opening degree. As a result, only the main feedwater bypass valve is opened during low loads, and both the main feedwater valve and the main feedwater bypass valve are opened during high loads, which allows the feedwater flow rate during high loads to be increased compared to when only the main feedwater valve is open.

[0042] (3) A water supply control system according to a third aspect is the water supply control system of (2), in which, when the load is equal to or greater than a first threshold and the main water supply bypass valve and the main water supply valve are open, the water supply control device opens the main water supply bypass valve and closes the main water supply valve when the load decreases to a second threshold from a state in which the load is equal to or greater than a first threshold and the main water supply bypass valve and the main water supply valve are open. This allows control so that during high loads, both the main feedwater valve and the main feedwater bypass valve are open, and during low loads, only the main feedwater bypass valve is open.

[0043] (4) A water supply control system according to a fourth aspect is a water supply control system according to any one of (1) to (3), wherein the water supply control device closes the main water supply bypass valve at a constant speed to the first target valve opening degree and opens the main water supply valve at a constant speed to the second target valve opening degree. This allows the main water supply valve and the main water supply bypass valve to be opened and closed at a constant speed, thereby suppressing fluctuations in the water supply flow rate while controlling both the main water supply valve and the main water supply bypass valve to an open state.

[0044] (5) A feedwater control system according to a fifth aspect is a feedwater control system according to any one of (1) to (4), wherein the feedwater control device has a first function that defines the relationship between the target opening of the main feedwater bypass valve and the steam flow rate when both the main feedwater valve and the main feedwater bypass valve are in an open state, a second function that defines the relationship between the opening of the main feedwater bypass valve and the feedwater flow rate passing through the main feedwater bypass valve, and a third function that defines the relationship between the opening of the main feedwater valve and the feedwater flow rate passing through the main feedwater valve, and The first target opening is calculated based on the first function, the supply water flow rate of the cooling water that passes through the main feedwater bypass valve when the first target opening is achieved is calculated based on the first target opening and the second function, a differential flow rate is calculated by subtracting the supply water flow rate of the cooling water that passes through the main feedwater bypass valve when the first target opening is achieved from the supply water flow rate of the cooling water that passes through the main feedwater bypass valve in a state before the main feedwater bypass valve is closed, and the second target opening is calculated based on the differential flow rate and the third function. This makes it possible to calculate the first target opening degree and the second target opening degree.

[0045] (6) A sixth aspect of the feedwater control device is a feedwater control device that controls the feedwater flow rate of the cooling water to the steam generator by controlling the main feedwater valve and the main feedwater bypass valve in a feedwater system that includes a main feedwater flow path that supplies cooling water to a steam generator, a main feedwater valve provided in the main feedwater flow path, a main feedwater bypass flow path that bypasses the main feedwater flow path, and a main feedwater bypass valve provided in the main feedwater bypass flow path, and that calculates a first target opening based on the steam flow rate supplied from the steam generator to a steam turbine, closes the main feedwater bypass valve to achieve the first target valve opening, calculates a second target opening that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, opens the main feedwater valve that is closed to achieve the second target opening, and opens the main feedwater valve and the main feedwater bypass valve.

[0046] (7) A seventh aspect of the feedwater control method is a feedwater control method for controlling a feedwater flow rate by controlling the main feedwater valve and the main feedwater bypass valve in a feedwater system including a main feedwater flow path that supplies cooling water to a steam generator, a main feedwater valve provided in the main feedwater flow path, a main feedwater bypass flow path that bypasses the main feedwater flow path, and a main feedwater bypass valve provided in the main feedwater bypass flow path, the method comprising: calculating a first target opening based on the steam flow rate supplied from the steam generator to a steam turbine; closing the main feedwater bypass valve to achieve the first target opening; calculating a second target opening that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve; opening the main feedwater valve that is closed to achieve the second target opening; and opening the main feedwater valve and the main feedwater bypass valve.

[0047] (8) A program according to an eighth aspect causes a computer that controls the feedwater flow rate by controlling the main feedwater valve and the main feedwater bypass valve in a feedwater system that includes a main feedwater flow path that supplies cooling water to a steam generator, a main feedwater valve provided in the main feedwater flow path, a main feedwater bypass flow path that bypasses the main feedwater flow path, and a main feedwater bypass valve provided in the main feedwater bypass flow path to calculate a first target opening based on the steam flow rate supplied from the steam generator to a steam turbine, close the main feedwater bypass valve to achieve the first target opening, calculate a second target opening that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, open the main feedwater valve that is closed to achieve the second target opening, and open the main feedwater valve and the main feedwater bypass valve. [Explanation of symbols]

[0048] 1. Steam generator 2. Primary cooling loop 3. Steam supply channel 4. Steam turbine 5. Condenser 6. Secondary cooling loop 7...Main water supply flow path 8. Main water supply bypass flow path 10. Water supply control device 11. Sensor data acquisition section 12 Input reception section 13 Control section 131 Opening degree calculation unit 132 Main water supply valve control section 133 Main water supply bypass valve control section 14. Output section 15...Storage section 100...Water supply control system P1 Primary cooling pump V1 Main water supply valve V2: Main water supply bypass valve c1, c2, c3... sensors 900···Computer 901 CPU 902...Main memory 903...Auxiliary storage device 904 Input / Output Interface 905···Communication Interface

Claims

1. a main feedwater flow path constituting a feedwater system for supplying cooling water to the steam generator; a main water supply valve provided in the main water supply flow path; a main water supply bypass flow path that constitutes the water supply system and bypasses the main water supply flow path; a main water supply bypass valve provided in the main water supply bypass flow path and having a valve capacity smaller than that of the main water supply valve; a water supply control device that controls the main water supply valve and the main water supply bypass valve to control the supply water flow rate of the cooling water, The water supply control device includes: calculating a first target opening based on a steam flow rate supplied from the steam generator to a steam turbine, and closing the main feedwater bypass valve so as to achieve the first target opening; calculating a second target opening degree that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, and opening the main feedwater valve that is in a closed state so as to achieve the second target opening degree; The main water supply valve and the main water supply bypass valve are opened, The main feedwater bypass valve is not fully closed regardless of the steam flow rate. Water supply control system.

2. When the load on the steam turbine is lower than a first threshold, the feedwater control device opens the main feedwater bypass valve and closes the main feedwater valve, and when the load increases from that state and reaches the first threshold, closes the main feedwater bypass valve to the first target opening degree and opens the main feedwater valve to the second target opening degree. The water supply control system according to claim 1 .

3. When the load is equal to or greater than a first threshold and the main water supply bypass valve and the main water supply valve are open, the water supply control device The main water supply bypass valve is opened, and then the main water supply valve is closed until it is fully closed. The water supply control system according to claim 2 .

4. the water supply control device closes the main water supply bypass valve at a constant speed to the first target opening degree, and opens the main water supply valve at a constant speed to the second target opening degree; The water supply control system according to claim 1 or 2.

5. The water supply control device includes: a first function that defines a relationship between a target opening of the main feedwater bypass valve and the steam flow rate when both the main feedwater valve and the main feedwater bypass valve are opened; a second function that defines the relationship between the opening degree of the main feedwater bypass valve and the flow rate of the feedwater passing through the main feedwater bypass valve; a third function that defines the relationship between the opening degree of the main water supply valve and the flow rate of the water supply passing through the main water supply valve; calculating the first target opening based on the steam flow rate before the main feedwater bypass valve is closed and the first function; calculating a feedwater flow rate of the cooling water passing through the main feedwater bypass valve when the first target opening is achieved based on the first target opening and the second function; calculating a differential flow rate by subtracting a feedwater flow rate of the cooling water passing through the main feedwater bypass valve when the first target opening degree is achieved from a feedwater flow rate of the cooling water passing through the main feedwater bypass valve in a state before the main feedwater bypass valve is closed; calculating the second target opening based on the differential flow rate and the third function; The water supply control system according to claim 1 or 2.

6. a main feedwater bypass flow path that bypasses the main feedwater flow path; and a main feedwater bypass valve that is provided in the main feedwater bypass flow path and has a smaller valve capacity than the main feedwater valve. calculating a first target opening based on a steam flow rate supplied from the steam generator to a steam turbine, and closing the main feedwater bypass valve so as to achieve the first target opening; calculating a second target opening degree that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, and opening the main feedwater valve that is in a closed state so as to achieve the second target opening degree; The main water supply valve and the main water supply bypass valve are opened, The main feedwater bypass valve is not fully closed regardless of the steam flow rate. Water supply control device.

7. A feedwater control method for a feedwater system including a main feedwater flow path that supplies cooling water to a steam generator, a main feedwater valve provided in the main feedwater flow path, a main feedwater bypass flow path that bypasses the main feedwater flow path, and a main feedwater bypass valve provided in the main feedwater bypass flow path and having a valve capacity smaller than that of the main feedwater valve, the method comprising: calculating a first target opening based on a steam flow rate supplied from the steam generator to a steam turbine, and closing the main feedwater bypass valve so as to achieve the first target opening; calculating a second target opening degree that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, and opening the main feedwater valve that is in a closed state so as to achieve the second target opening degree; The main water supply valve and the main water supply bypass valve are opened, The main feedwater bypass valve is not fully closed regardless of the steam flow rate. Water supply control method.

8. In a feedwater system including a main feedwater flow path that supplies cooling water to a steam generator, a main feedwater valve provided in the main feedwater flow path, a main feedwater bypass flow path that bypasses the main feedwater flow path, and a main feedwater bypass valve provided in the main feedwater bypass flow path and having a valve capacity smaller than that of the main feedwater valve, a computer that controls a feedwater flow rate by controlling the main feedwater valve and the main feedwater bypass valve includes: calculating a first target opening based on a steam flow rate supplied from the steam generator to a steam turbine, and closing the main feedwater bypass valve so as to achieve the first target opening; calculating a second target opening degree that compensates for the feedwater flow rate of the cooling water that is reduced by the closing operation of the main feedwater bypass valve, and opening the main feedwater valve that is in a closed state so as to achieve the second target opening degree; a process of opening the main feedwater valve and the main feedwater bypass valve and not fully closing the main feedwater bypass valve regardless of the steam flow rate; A program that executes the following.

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