JP7770222B2 - Water supply control system, water supply control device, water supply control method and program - Google Patents

Description

This disclosure relates to a steam generator water supply control system, a water supply control device, a water supply control method, and a program.

In addition to the main feedwater flow path, the steam generator in a nuclear power plant is equipped with a bypass flow path. The main feedwater flow path is equipped with a main feedwater valve, and the bypass flow path is equipped with a main feedwater bypass valve. Conventionally, under high load conditions (high steam flow rate from the steam generator to the turbine), 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 (low steam flow rate), the main feedwater valve is closed to supply cooling water to the steam generator through the bypass flow path (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 higher 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 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 could result in unstable water supply control.

Japanese Patent Application Publication No. 10-253007

A method is needed to supply water to the 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.

This disclosure provides a water supply control system, water supply control device, water supply control method, and program that can solve the above problems.

The feedwater control system of the present disclosure includes a main feedwater flow path constituting a feedwater system 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 constituting the feedwater system and bypassing the main feedwater flow path, a main feedwater bypass valve provided in the main feedwater bypass flow path and having a smaller valve capacity than the main feedwater 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, and the feedwater control device controls the main feedwater valve and the main feedwater bypass valve to control the steam generator. A first target opening is calculated based on the steam flow rate supplied from the generator to the steam turbine, the main feedwater bypass valve is closed so as to achieve the first target opening, a second target opening is calculated 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, the main feedwater valve that is in a closed state is opened so as to achieve the second target opening, the main feedwater valve and the main feedwater bypass valve are opened, and the main feedwater bypass valve is not fully closed regardless of the steam flow rate.

The feedwater control device of the present disclosure 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 that is provided in the main feedwater bypass flow path and has a smaller valve capacity than the main feedwater valve, and the feedwater control device 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 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, opens the main feedwater valve and the main feedwater bypass valve to open states , and does not fully close the main feedwater bypass valve regardless of the steam flow rate.

The feedwater control method disclosed herein 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 and having a smaller valve capacity than the main feedwater valve, 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; 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.

The program disclosed herein causes a computer to execute processing in a feedwater system including a main feedwater passage that supplies cooling water to a steam generator, a main feedwater valve provided in the main feedwater passage, a main feedwater bypass passage that bypasses the main feedwater passage, and a main feedwater bypass valve provided in the main feedwater bypass passage and having a smaller valve capacity than the main feedwater valve, the computer controlling the feedwater flow rate by controlling the main feedwater valve and the main feedwater bypass valve 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, open the main feedwater valve and the main feedwater bypass valve, and do not fully close the main feedwater bypass valve regardless of the steam flow rate .

The above-described water supply control system, water supply control device, water supply control method, and program enable water to be supplied to the steam generator by opening both the main water supply valve and the main water supply bypass valve.

1 is a schematic diagram of a steam generator feedwater control system according to an embodiment; FIG. 2 is a block diagram showing an example of a water supply control device according to an embodiment. FIG. 10 is a diagram illustrating an example of control when a load increases according to the embodiment. FIG. 10 is a first diagram showing an example of a function used to calculate an opening degree according to the embodiment. FIG. 10 is a second diagram showing an example of a function used to calculate an opening degree according to the embodiment. FIG. 10 is a third diagram showing an example of a function used to calculate an opening degree according to the embodiment. FIG. 10 is a diagram illustrating an example of control during a load drop according to the embodiment. 10 is a flowchart illustrating an example of a process when a load increases according to the embodiment. 10 is a flowchart illustrating an example of a process performed when a load drops according to the embodiment. A diagram showing an example of the hardware configuration of a water supply control device according to an embodiment.

The water supply control system of the present disclosure will be described below with reference to FIGS. 1 to 7. FIG.
<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). The rotational drive of the steam turbine 4 generates 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 the steam turbine 4 has performed work. 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. A 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 degree of the main feedwater bypass valve V2. A main feedwater valve V1 is provided downstream of a branch point 71 in the main feedwater flow path 7. The flow rate of 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 fine adjustment of its opening difficult. Furthermore, when the opening of the main feedwater valve V1 is small, fluctuations occur in the flow rate. On the other hand, the main feedwater valve V1 has the characteristic of being excellent in controllability of large flow rates.

The steam generator 1 is equipped with a sensor c1 that measures the cooling water level. The steam supply line 3 is equipped 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 line 7 is equipped 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-c3 are connected to the feedwater control device 10. The water level, steam flow rate, and feedwater flow rate measured by sensors c1-c3 are transmitted 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 sensor c2 is positively correlated with the power generation load of the generator (not shown) and is used as an indicator of the load (for example, the power generation load and 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 sensor c2 and the feedwater flow rate measured by sensor c3.

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. Figure 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 supply valve V1 and the main water supply bypass valve V2. The automatic switching control of the main water supply valve V1 and the main water supply bypass valve V2 will be described later.

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.

The opening degree calculation unit 131 calculates the target opening degrees of the main water supply valve V1 and the main water supply 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 water supply bypass valve control unit 133 controls the opening degree of the main water supply bypass valve V2 based on the target opening degree of the main water supply bypass valve V2 calculated by the opening degree calculation unit 131.

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.

(Control of the main water supply valve V1 and the main water supply 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 involves 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 involves 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 load conditions, both the main feedwater valve V1 and the main feedwater bypass valve V2 are opened, allowing 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 opened while suppressing fluctuations in the feedwater flow rate.

[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 for the main feedwater bypass valve V2) or the main feedwater valve control signal (opening command value for 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.

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. The opening calculation unit 131 then calculates the target opening of the main feedwater bypass valve V2 based on the current (pre-switching) steam flow rate measured by sensor c2, by referencing function F1, which defines the relationship between steam flow rate and main feedwater bypass valve opening rate, as shown in FIG. 4A. For example, if the pre-switching steam flow rate measured by sensor c2 is 20% (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%.

Next, the opening calculation unit 131 references function F2, which defines the relationship between the main feedwater bypass valve opening 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), as shown in FIG. 4B, 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).

The opening calculation unit 131 then 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). The opening calculation unit 131 then calculates the target opening rate of the main feedwater valve V1 by referencing function F3, which defines the relationship between the main feedwater valve opening rate and the feedwater flow rate of secondary cooling water passing through the main feedwater valve V1, as shown in Figure 4C. For example, the opening calculation unit 131 references the function F3 illustrated in Figure 4C and calculates the target opening of the main feedwater valve V1 of 15% required to flow 150 (tons/h). This calculates the target opening of the main feedwater valve V1 after switching to 15% and the target opening of the main feedwater bypass valve V2 to 20%, compared to the opening of the main feedwater valve V1 of 0% and the opening of the main feedwater bypass valve V2 of 70% before switching.

Next, the main water supply valve control unit 132 begins opening the main water supply valve V1 at time t1, opening it at a constant speed to the target opening of 15%. The speed at which the main water supply valve V1 is opened is predetermined. The main water supply bypass valve control unit 133 begins closing the main water supply bypass valve V2 at time t2, reducing the opening of the main water supply 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 water supply valve V1 and the target opening of 20% for the main water supply bypass valve V2 are achieved at time t3, and then, as the load increases, the openings of the main water supply valve V1 and the main water supply 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, during high loads, both the main feedwater valve V1 and the main feedwater bypass valve V2 can be opened, allowing a larger volume of secondary cooling water to be supplied to the steam generator 1 compared to conventional water supply systems where only the main feedwater valve V1 is open. Furthermore, by opening the main feedwater bypass valve V2, the burden on the main feedwater valve V1 alone is not placed, reducing the burden on the main feedwater valve V1.

In addition, in this embodiment, the main water supply 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 water supply flow rate due to automatic switching control, as shown in graph g3 in Figure 31 above, and allows both the main water supply valve V1 and the main water supply bypass valve V2 to be opened with only relatively small fluctuations. As shown in graph g3, by opening both the main water supply valve V1 and the main water supply bypass valve V2, fluctuations in the water supply flow rate can be quickly stabilized. For comparison with the automatic switching control of this embodiment, control was performed in which the main water supply valve V1 was gradually opened while the main water supply 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 water supply flow rate occurred during the process of gradually opening the main water supply valve V1 because the main water supply valve V1 was left slightly open.

[When load drops]
FIG. 5 is a diagram illustrating an example of control during a load drop according to the embodiment.
5, the vertical axis represents the main feedwater bypass valve control signal (opening command value for the main feedwater bypass valve V1) or the main feedwater valve control signal (opening command value for 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 degree of the main feedwater valve V1 is reduced by the amount that the main feedwater bypass valve V2 was open before the switching started. 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 degree calculation unit 131 then calculates the opening degree of the main feedwater bypass valve V2 after the switching. The target opening degree of the main feedwater valve v1 is 0%. For example, the opening degree calculation unit 131 may calculate the target opening degree 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 degree.

Next, the main water supply valve control unit 132 begins closing the main water supply valve V1 at time t2, closing it at a constant speed until the target opening degree reaches 0%. The speed at which the main water supply valve V1 is closed is predetermined. The main water supply bypass valve control unit 133 begins opening the main water supply bypass valve V2 at time t1, increasing the opening degree of the main water supply bypass valve V2 to the target opening degree at a constant speed. When switching is completed at time t4, opening degree control of the main water supply 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 water supply valve V1 and the main water supply bypass valve V2 are controlled so that the water supply flow rate during automatic switching control remains constant. Furthermore, even when the load drops, the main water supply valve V1 is fully closed rather than slightly opened, thereby suppressing fluctuations in the water supply flow rate.

(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 acquisition unit 11 acquires the measurement values measured by the sensors c1 to c3 (step S1). For example, the sensor data acquisition 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.

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 reception 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 reception unit 12. If there is no switching instruction (step S2; No), the process repeats from step S1. If there is a switching instruction (step S2; Yes), the control unit 13 determines whether 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 the water supply flow rate measured by sensor c3 is within the 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 automatic switching control cannot be performed because the water supply flow rate is not within the allowable range.

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 switch (Step S5). As described using Figures 3 and 4A to 4C, the opening calculation unit 131 calculates the target opening of the main feedwater bypass valve V2 after the switch based on the steam flow rate before the switch and function F1 (Figure 4A). The opening calculation unit 131 also calculates the target opening of the main feedwater valve V1 after the switch 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 switch 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 allows both the main water supply valve V1 and the main water supply bypass valve V2 to be controlled to an open state while suppressing fluctuations in the water supply flow rate.

[When load drops]
Next, the process when the load drops will be described. The same processes as those in Fig. 6A will be briefly described. Fig. 6B is a flowchart showing an example of the process 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.

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 their open states 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 the target opening after the switch (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, the opening calculation unit 131 calculates the target opening of the main feedwater bypass valve V2, for example, based on the steam flow rate corresponding to the target load after the switch. For example, the memory unit 15 stores a function F4 (not shown) that defines the relationship between the steam flow rate and the main feedwater bypass valve opening rate. 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 switch. Function F1 shown in Figure 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 (e.g., steam flow rate of 20%).

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

In the processing illustrated in Figures 6A and 6B, the user issues a switching instruction (step S2 in Figure 6A, step S12 in Figure 6B), but the control unit 13 may automatically determine to perform automatic switching control for a load increase if the steam flow rate measured by sensor c2 increases from, for example, a steam flow rate of less than 20% when operating at rated load to 20% and the feedwater flow rate is within an acceptable range (step S3; Yes). Similarly, the control unit 13 may determine to perform automatic switching control for 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 acceptable range (step S13; Yes).

In addition, in the above description of Figure 3, automatic switching control is performed when the load increases to a certain level, and then the load is increased using a different 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 the target steam flow rate corresponding to the target load after switching and the function F1 of Figure 4A, and calculates the feedwater flow rate passing through the main feedwater bypass valve V2 after switching based on the function F2 of Figure 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 water supply valve V1 using the calculated water supply flow rate passing through the main water supply valve V1 and the function F3 in Figure 4C.

(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 slightly open.

FIG. 7 is a diagram illustrating an example of the hardware configuration of the water supply control device according to the 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.

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. Here, "computer system" includes hardware such as the OS and peripheral devices. Furthermore, if a WWW system is used, "computer system" also includes the homepage provision environment (or display environment). Furthermore, "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 this program is distributed to the computer 900 via a communication line, the computer 900 that receives the program may deploy the program in the main storage device 902 and execute the above-mentioned processing. Furthermore, the program may be for implementing part of the above-mentioned functions, or may be capable of implementing the above-mentioned functions in combination with programs already stored in the computer system.

As described above, several embodiments of the present disclosure have been described. However, all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments may be embodied in a variety of other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope of the invention and its equivalents as set forth in the claims, as well as within the scope and spirit of the invention.

<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.

(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, The 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 that is closed 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.

(2) A second aspect of the feedwater control system is the feedwater control system of (1), wherein the feedwater control device opens the main feedwater bypass valve and closes the main feedwater 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 feedwater bypass valve to the first target valve opening degree and opens the main feedwater 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.

(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.

(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 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.

(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.

(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. 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 valve opening, calculates a second target opening that compensates for the decrease in the feedwater flow rate of the cooling water due to 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.

(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 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 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.

(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.

1...Steam generator 2...Primary cooling loop 3...Steam supply passage 4...Steam turbine 5...Condenser 6...Secondary cooling loop 7...Main feedwater passage 8...Main feedwater bypass passage 10...Feedwater control device 11...Sensor data acquisition unit 12...Input reception unit 13...Control unit 131...Opening calculation unit 132...Main feedwater valve control unit 133...Main feedwater bypass valve control unit 14...Output unit 15...Memory unit 100...Feedwater control system P1...Primary cooling pump V1...Main feedwater valve V2...Main feedwater bypass valves c1, c2, c3...Sensor 900...Computer 901...CPU
902: Main storage device 903: Auxiliary storage device 904: Input/output interface 905: Communication interface

Claims (8)

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. 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 achieve the first target opening degree and opens the main feedwater valve to achieve a second target opening degree.
The water supply control system according to claim 1 . 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 . 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. 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. 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. 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. 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.