JPH0979508A - Feed water controller for steam generating plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the change of water level as much as possible at the time of opening/closing of a feed water pump recirculation valve to become the disturbance of a feed water flow rate in the control of the water level of a steam generating plant. SOLUTION: The feed water controller for a steam generating plant comprises a main control system 22 for controlling the feed water flow rate of a feed water pump based on the water level detected value of a steam generator 1, and a correction control system for opening a switch 30 at the time of starting to switch the pump, storing the feed water flow signal S2 at this time in a memory 31 as a target feed water flow S7, comparing the flow S2 with the flow S7 during switching of the pump to obtain a feed water flow change and inputting the change to a feed water flow correcting circuit 33 to obtain a feed water flow correction amount S7 by control calculation. The correction amount of the control system is added to the feed water flow of the correction control system, and the water level change of the plant is suppressed prior to the control by the main control system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water supply control device for a steam generating plant in a steam generating plant provided with a water supply pump recirculation valve.

[0002]

2. Description of the Related Art A steam generating plant such as a nuclear power plant or a thermal power plant has a water supply facility including a plurality of water supply pumps. For the water supply pump, for example, a turbine drive pump or a motor drive pump is used, and the turbine drive pump controls the pump rotation speed and the motor drive pump controls the water supply control valve opening by the water supply control device. The water supply controller is
It takes in the water level, feed water flow rate, and main steam flow rate in the reactor pressure vessel or boiler, which is a steam generator, from the plant, and outputs a feed water pump control signal that keeps the water level in the steam generator constant. Since these water supply pumps have different capacities and water supply capacities, a plurality of water supply pumps are sequentially switched and used in order to obtain water supply performance corresponding to the output of the plant. Generally, motor driven pumps are used at low power, turbine driven pumps are used at high power and during rated operation. When the plant starts up, one motor-driven pump is switched to one turbine-driven pump in response to the increase in output, and another turbine-driven pump is added. Water is supplied by two turbine driven pumps during rated operation. When the plant is stopped, one turbine drive pump is stopped first, and then one turbine drive pump is switched to one motor drive pump in response to the output reduction.

Here, the switching of the water supply pump by the conventional water supply control device will be described below by taking the case where the turbine drive pump is started and the motor drive pump is stopped as the plant output rises when the plant starts. To do.
First, in the water supply control device, the turbine drive pump operating device is set to the manual mode, the increase command is output from the water supply control device, and the turbine speed is increased. The increase in turbine rotation speed increases the feedwater pump rotation speed, which increases the feedwater flow rate. The water level in the steam generator rises as the water supply flow rate increases. On the other hand, the motor driven pump is in the automatic mode, and the pump flow rate is controlled by the control calculation of the main water level controller so as to suppress the deviation between the water level in the steam generator and the target water level set value. In this case, since the water level has risen, the motor-driven pump performs an operation of reducing the water supply flow rate. The increase command to the turbine drive pump is issued until it becomes equal to the output signal of the main water level controller. After that, the motor-driven pump operating device is set to the manual mode, the water supply control device outputs a decrease command, and the control signal becomes 0, whereby the switching from the motor-driven pump to the turbine-driven pump is completed. Next, switching of the water supply pumps by the conventional water supply control device will be described below by taking as an example a case where the motor driven pump is started and the turbine driven pump is stopped when the plant output is reduced and the plant output is reduced. First, in the water supply control device, the motor-driven pump operating device is set to the manual mode, an increase command is output from the water supply control device, and the water supply control valve opening is increased. This increases the water supply flow rate. The water level in the steam generator rises as the water supply flow rate increases. On the other hand, the turbine driven pump is in the automatic mode, and the pump flow rate is controlled by the control calculation of the main water level controller so as to suppress the deviation between the water level in the steam generator and the target water level set value. In this case, since the water level is rising, the turbine drive pump performs the operation of reducing the feed water flow rate. The increase command to the motor driven pump is
Repeat until the output signal of the main water level controller becomes equal. After that, the turbine drive pump operating device is set to the manual mode, the water supply control device outputs a decrease command, and the control signal becomes 0, whereby the switching from the turbine drive pump to the motor drive pump is completed.

By the way, when the flow rate through the pump is reduced as in the case of switching the water supply pump, the temperature rise of the pump fluid and the pump shaft vibration easily occur due to the shutoff operation of the pump. Therefore, each water supply pump is provided with a recirculation valve (minimum flow valve) for ensuring a minimum flow rate (minimum flow) of the water supply pump for the purpose of protecting pump equipment. Each recirculation valve is opened manually or automatically when the suction flow rate of each water supply pump becomes equal to or lower than the minimum flow rate set value. Conversely, when the suction flow rate exceeds the minimum flow rate setting value, each recirculation valve closes. In this way, consideration is given to always ensuring the minimum flow rate of each pump. When switching the water supply pump,
In one of the aforementioned examples, the flow rate of the motor driven pump is reduced. When the suction flow rate of the motor-driven pump falls below the minimum flow rate set value, the recirculation valve provided on the discharge side of the motor-driven pump opens. Similarly, in another example of the above, when increasing the flow rate of the motor-driven pump, when the suction flow rate of the motor-driven pump exceeds the minimum flow rate setting value, the recirculation provided on the discharge side of the motor-driven pump is performed. The valve will close. In the conventional steam generating plant, the minimum flow rate of the water supply pump may be relatively small, so the so-called on-off control method (fully open-fully closed control method) is adopted as the opening / closing control method of the recirculation valve. There are many cases. However, with the recent increase in the scale of steam generation plants, the minimum flow rate of the water supply pump is required to be relatively large compared to the conditions for protecting the water supply pump. Along with the large change in flow rate, it greatly affects the water level of the steam generator. The fluctuation of the water level due to the opening / closing operation of the recirculation valve is another phenomenon that occurs when the second water supply pump is added or stopped. Therefore, as a control method for minimizing the influence on the water level of the steam generator, a program control method for opening and closing the recirculation valve at a constant rate, a proportional-integral control control method, etc. have been proposed. There is. Further, as a method of suppressing the fluctuation of the water level due to the opening / closing operation of the recirculation valve, for example, JP-A-4-75478 and JP-A-4-1945 are available.
As described in Japanese Patent Publication No. 03-2003, a valve opening transmitter is installed in each recirculation valve, and a valve opening signal when opening and closing the recirculation valve is taken in.
There is known a method of generating a correction signal of the water supply flow rate from this to suppress the water level fluctuation.

[0005]

The above-mentioned prior art has a structure in which the feed water flow rate fluctuation or the recirculation valve passing flow rate is estimated from the valve opening signal of the recirculation valve, and the main water level controller output is bias-corrected. ing. However, in particular, fluctuations in the feedwater flow due to opening and closing of the recirculation valve during switching of the feedwater pump are accompanied by pipe flow interference of the entire plant supply / condensation system and cannot be uniquely determined from the valve opening signal of the recirculation valve. The correction does not provide an appropriate correction of the water supply flow rate, so that not only the effect of suppressing the fluctuation of the water level is small, but also the fluctuation may be promoted.

It is an object of the present invention to control the water level of a steam generating plant, in which the fluctuation of the water level is suppressed as much as possible during the opening / closing operation of the water supply pump recirculation valve which causes disturbance of the feed water flow rate. To provide.

[0007]

[Means for Solving the Problems] The above object is to provide a main control system for controlling the feed water flow rate of a water feed pump based on the detected water level of a steam generator, and a target water feed flow rate and recirculation set at the start of switching of the water feed pump. There is a correction control system that calculates the amount of water supply flow rate change by comparing the amount of water supply flow that fluctuates due to opening and closing of the valve, and calculates a correction amount based on this amount of water supply flow rate change. It is achieved by adding to the water supply flow rate by the system.

[0008]

According to the present invention, the recirculation valve provided on the discharge side of the feed water flow rate control command for the control system for controlling the actual water level to the target water level based on the detected water level of the steam generator. Since it compensates in advance according to the change in the water supply flow rate due to the opening / closing operation of the steam generator, it is possible to greatly suppress the change in the water level of the steam generator. It is possible to suppress the fluctuation of the water level in the reactor and maintain the stability of the plant.

[0009]

Embodiments of the present invention will be described below. FIG.
1 is a water supply control device for a steam generating plant according to an embodiment of the present invention, showing a case where the present invention is applied to a BWR power generation plant which is one of the steam generating plants. In this embodiment, the reactor pressure vessel corresponds to the steam generator. The BWR power generation plant includes two turbine drive pumps 9A and 9B (hereinafter, TD-RFP) as water supply pumps and a motor drive pump 1.
It has two 1A and 11B (hereinafter, MD-RFP) units. During normal operation, the steam generated in the reactor pressure vessel 1
It passes through the main steam pipe 2, is adjusted by the main steam control valve 3, and is sent to the turbine 4. The turbine 4 causes the generator 5 to work and generate electricity. The steam exhausted from the turbine 4 is condensed in the condenser 6. The condensed water is reused as cooling water for the nuclear reactor 1. First, it is supplied to the condensate pump 8 through the water supply pipe 7. Further, during normal operation, the pressure is increased by the two TD-RFPs 9A and 9B and supplied to the reactor pressure vessel 1. Here, TD-RFP9
A and 9B are pump drive turbines 10A and 10B that use steam extracted from the turbine 4 as a drive source.
Control the pump speed and adjust the pump flow rate. On the other hand, since the two MD-RFs 11A and 11B are used for backup of the TD-RFP during normal operation, they are in a standby state and used for water supply control when starting and stopping the reactor 1. The flow rate control of MD-RFP is performed by the water supply control valves 12A and 12B. The water supply pipe 7 is provided with branch pipes 13A, 13B, 13C and 13D, and recirculation valves 14A, 14B attached to these branch pipes,
14C and 14D are TD-RFP and MD-RF
Opening and closing operations are performed when P is started and stopped to ensure the minimum flow rate of each water supply pump. The water passing through each recirculation valve returns to the condenser 6 again. The control of the feed water flow rate by TD-RFP and MD-RFP is performed by the water gauge 15 of the reactor pressure vessel 1,
This is performed by the water supply control device 20 that inputs the detection values of the water supply flow meter 16 provided in the water supply pipe 7 and the main steam flow meter 17 provided in the main steam pipe 2.

The water supply controller 20 includes a gain element 24, a main water level controller 27, turbine drive pump operators 28A and 28B in automatic / manual mode, motor drive pump operators 29A and 29B in automatic / manual mode, and a storage circuit 31. , Feed water flow rate correction circuit 33, comparators 22, 23, 32, adder 2
5, 34, a signal switch 26, and a switch 30. The operation of the water supply control device 20 will be described. At the time of high output of the plant (for example, 30% or more), the signal switch 26
Is switched to the adder 25, and the switch 30 is turned on. In this state, the reactor water level signal S1 of the water level gauge 15 is compared with the water level set value 21 in the comparator 22 to obtain the water level deviation. In addition, the water supply flow rate signal S of the water supply flow meter 16
2 and the deviation signal between the main steam flow signal S3 of the main steam flow meter 17 are output from the comparator 23, and the deviation signal has a gain K24.
Is added to the reactor water level deviation signal in the adder 25, and is input to the main water level controller 27 through the signal switch 26. The main water level controller 27 outputs the feed water flow rate control command S4 by a proportional integral calculation or the like. Water supply flow rate control command S
4 is input to turbine drive pump operators 28A and 28B to control pump drive turbines 10A and 10B, and is also input to motor drive pump operators 29A and 29B to control water supply control valves 12A and 12B. On the other hand, when the plant has a low output (for example, 30% or less), the signal switch 26 switches to the comparator 22,
Only the reactor water level deviation output from the comparator 22 is input to the main water level controller 27. Here, during normal operation of the plant, turbine driven pump operators 28A and 28B,
The motor driven pump operators 29A and 29B are in the automatic mode. On the other hand, when switching the water supply pump, the operating device of the pump to be started or stopped is set to the manual mode and the pump flow rate is increased or decreased.

The control operation of the water supply controller 20 when switching the water supply pump will be described below. In FIG. 1, when the feed water pump recirculation valve is opened / closed when the feed water pump is switched, the feed water flow rate supplied from the feed water pipe 7 to the reactor pressure vessel 1 changes, and the water level of the reactor pressure vessel 1 changes.
Therefore, first, when starting the switching of the water supply pump, the signal switch 26 is switched to the comparator 22 and the switch 30 is turned off. By switching the signal switch 26, the reactor water level deviation is input to the main water level controller 27, and the feed water flow rate control command S4 is output. Further, when the switch 30 is turned off, the water supply flow rate signal S2 at the start of switching the water supply pump is stored in the storage circuit 31. The stored value will be hereinafter referred to as the target water supply flow rate S7. Next, during switching of the water supply pump, the water supply flow rate signal S2 is compared with the target water supply flow rate S7 in the comparator 32 to obtain the water supply flow rate change amount. The water supply flow rate change amount is input to the water supply flow rate correction circuit 33, becomes a water supply flow rate correction signal S8 by control calculation, and is added to the water supply flow rate control command S4 of the main water level controller 27 by the adder 34. The corrected water supply flow rate control command S4 is input to the pump operator to correct and control the water supply flow rate. In this way, the water supply control device 20 corrects the water supply flow rate based on the amount of change in the water supply flow rate that fluctuates by opening and closing the water supply pump recirculation valve when switching the water supply pump.

Here, FIG. 2 shows respective operations of the feed water flow rate correction circuit 33 when the feed water pump recirculation valve is opened, and FIG. 3 is shown when the feed water pump recirculation valve is closed. In FIG. 2, at the start of switching of the water supply pump, as described above, the switch 30 is turned off and the water supply flow rate signal S2 is stored in the storage circuit 31. This stored value is used as the target water supply flow rate S
7 is assumed. During the switching of the water supply pump, the water supply pump recirculation valve opens, so the water supply flow rate to the reactor 1 decreases, and the water supply flow meter 1
The water supply flow rate signal S2 of 6 decreases as shown. This lowered feed water flow rate signal S2 is compared with the target feed water flow rate S7, and this deviation is obtained as the feed water flow rate change amount. This feed water flow rate change amount is input to the feed water flow rate correction circuit 33, and the feed water flow rate correction circuit 33 performs control calculation and outputs a feed water flow rate correction signal S8. As shown in the figure, the feed water flow rate correction signal S8 takes a positive value with respect to the decrease in the feed water flow rate due to the opening of the recirculation valve of the water feed pump, and functions as a correction signal for increasing the feed water flow rate. In FIG. 3, when the switching of the water supply pump is started, similarly, the switch 30 is turned off and the water supply flow rate signal S2 is stored in the storage circuit 31. The stored value is set as the target water supply flow rate S7. Since the water supply pump recirculation valve is closed during switching of the water supply pump, the water supply flow rate to the reactor 1 increases, and the water supply flow rate signal S2 of the water supply flow meter 16 rises as illustrated. The increased feed water flow rate signal S2 is compared with the target feed water flow rate S7, and this deviation is obtained as the feed water flow rate change amount. This feed water flow rate change amount is input to the feed water flow rate correction circuit 33, and the feed water flow rate correction circuit 33 performs control calculation and outputs a feed water flow rate correction signal S8. The feed water flow rate correction signal S8 takes a negative value with respect to an increase in the feed water flow rate due to the closing of the recirculation valve of the water feed pump, and functions as a correction signal that reduces the feed water flow rate.

FIG. 4 shows the internal structure of the feed water flow rate correction circuit 33. The gain element 331 inputs the fluctuation of the water supply flow rate,
The input signal to the integrator 332 is output. Gain element 33
1 has a constant or variable function with respect to fluctuations in the water supply flow rate. The integrator 332 outputs the feed water flow rate correction signal S8 according to the change in the feed water flow rate. The integration time constant can be set shorter than the integration time constant of the main water level controller 27 (for example, around 10 seconds), although it depends on the water supply control characteristic of the plant.

Next, the operation when the water supply control apparatus of the present embodiment is applied at the time of switching the water supply pumps when starting and stopping the BWR power plant will be described. In the BWR power generation plant, the feed water flow rate is controlled by one MD-RFP from the start of the plant to the output of about 25%, and then,
One TD-RFP is activated, and switching to MD-RFP is performed. In FIG. 1, MD-RFP11A to TD-R
When switching to the FP9A, first, the operator 28A of the TD-RFP 9A is set to the manual mode, and the TD-RFP control signal S5A is increased as shown in FIG. 5 (a). Along with this, the control signal S6A of the MD-RFP 11A gradually decreases. MD-RFP11A suction flow rate is recirculation valve 14
When the open setting value of C (for example, the flow rate of 700 t / h) is dropped, the recirculation valve 14C opens at the time point (1). Along with this, at the time of (1), the feed water flow rate of about 500 t / h flows into the branch pipe 13C of the water feed pipe, and the feed water flow rate S2 suddenly decreases as shown in FIG. 5 (b). The water supply flow rate S2 at this time is, as described in FIG. 2, the target water supply flow rate S7.
And the deviation is obtained as the feed water flow rate change amount and is input to the feed water flow rate correction circuit 33. A positive feed water flow rate correction signal S is calculated by control calculation in the feed water flow rate correction circuit 33.
8 is output and immediately added to the feed water flow rate control command S4 of the main water level controller 27, and the corrected feed water flow rate control command S4 is input to the motor-driven pump operator 29A. As a result, the MD-RFP control signal S6A once increases. As a result, as shown in FIG. 5 (c), the decrease in the reactor water level S1 is suppressed, and the reactor water level S1 is controlled to be substantially constant. In this way, MD-RFP11A to TD-R
When switching to FP9A, the feed water flow rate is corrected based on the feed water flow rate change amount that fluctuates due to the opening operation of the feed water pump recirculation valve 14C, so that fluctuations in the reactor water level are suppressed prior to control by the main water level controller 27. be able to.

Further, in the BWR power generation plant, when the output drops to about 25% when the plant is stopped, the MD-RFP is started, one TD-RFP used for controlling the feed water flow rate is stopped, and the MD-RFP is set. Switch. In FIG. 1, TD-RFP9A to MD-
When switching to RFP11A, first, MD-RFP11
The operation device 29A of A is set to the manual mode, and the MD-RFP control signal S6A is increased as shown in FIG. Along with this, the control signal S5A of the TD-RFP 9A gradually decreases. Control signal S5A of TD-RFP9A and MD
-After RFP control signal S6A is balanced, this time M
The controller 29A of the D-RFP 11A is set to the automatic mode, while the controller 28A of the TD-RFP 9A is set to the manual mode to decrease the TD-RFP control signal S5A. Eventually, when the suction flow rate of the MD-RFP 11A exceeds the closed setting value of the recirculation valve 14C (for example, the flow rate 1200 t / h),
The recirculation valve 14C is closed at the time of (2). Along with this,
At the time of (2), the flow rate that has passed through the branch pipe 13C of the water supply pipe flows into the water supply pipe 7, and the water supply flow rate S2 suddenly increases as shown in FIG. 6 (b). The water supply flow rate S2 at this time is compared with the target water supply flow rate S7 as described in FIG. 3, and this deviation is obtained as the water supply flow rate change amount,
It is input to the water supply flow rate correction circuit 33. The feed water flow rate correction circuit 33 performs a control operation to output a negative feed water flow rate correction signal S8, and immediately supplies the feed water flow rate control command S of the main water level controller 27.
4, and the corrected feed water flow rate control command S4 is input to the motor-driven pump operator 29A. This gives M
The D-RFP control signal S6A will once decrease.
As a result, as shown in FIG. 6 (c), the rise of the reactor water level S1 is suppressed and the reactor water level S1 is controlled to be substantially constant. In this way, TD-RFP9A to MD-RFP11
When switching to A, since the feed water flow rate is corrected based on the feed water flow rate change amount that fluctuates due to the closing operation of the feed water pump recirculation valve 14C, the fluctuation of the reactor water level is suppressed prior to the control by the main water level controller 27. be able to.

[0016]

As described above, according to the present invention,
When the switching of the water supply pump is started, the water supply flow rate is corrected based on the amount of change in the water supply flow rate that fluctuates due to the opening / closing of the water supply pump recirculation valve, so it is possible to significantly suppress the water level change of the steam generator, and it is extremely stable. The operation of a high plant can be realized. Further, according to the present invention, when the switching of the water supply pump is started, the correction signal according to the change of the water supply flow rate is used to control the flow rate of the water supply pump in advance of the control command by the main water level controller. It is possible to maintain the stability of the plant by suppressing the fluctuation of the water level of the steam generator due to the opening and closing of the water supply pump recirculation valve during the switching of the water supply pump. Further, according to the present invention, since the recirculation valve opening signal of the water supply pump is not required as in the conventional case, there is no need to newly install a valve opening transmitter or remodel the hardware of the water supply control device.
The device can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a system diagram of a water supply control device of a steam generation plant and a BWR power generation plant showing an embodiment of the present invention.

FIG. 2 is an explanatory view of a feed water flow rate correction operation when the feed pump recirculation valve according to the present invention is opened.

FIG. 3 is an explanatory diagram of a feed water flow rate correction operation when the feed pump recirculation valve is closed according to the present invention.

FIG. 4 is a configuration diagram of a feed water flow rate correction circuit of the present invention.

FIG. 5 is an explanatory view of the behavior of the plant when the water supply pump recirculation valve according to the present invention is opened.

FIG. 6 is an explanatory diagram of the behavior of the plant when the water supply pump recirculation valve is closed according to the present invention.

[Explanation of symbols]

1 Reactor Pressure Vessel 2 Main Steam Pipe 3 Main Steam Control Valve 4 Turbine 5 Generator 6 Condenser 7 Water Supply Pipe 8 Condensate Pump 9A, 9B Turbine Drive Pump 10A, 10B Pump Drive Turbine 11A, 11B Motor Drive Pump 12A, 12B Water supply control valve 13A, 13B, 13C, 13D Water supply pump recirculation flow pipe 14A, 14B, 14C, 14D Water supply pump recirculation valve 15 Reactor water level meter 16 Water supply flow meter 17 Main steam flow meter 20 Water supply control device 24 Gain element 27 Main Water Level Controller 28A, 28B Turbine Drive Pump Operator 29A, 29B Motor Drive Pump Operator 31 Memory Circuit 33 Water Supply Flow Rate Correction Circuit 34 Adder 331 Gain Element 332 Integrator

Claims (5)

[Claims] 1. A water supply controller for controlling the water level of a steam generating plant to a target value, which has a steam generator, a plurality of water supply pumps for supplying water to the steam generator, and a recirculation valve provided in these water supply pumps. In the main control system for controlling the water supply flow rate of the water supply pump based on the water level detection value of the steam generator, the target water supply flow rate set at the start of switching of the water supply pump, and the water supply that fluctuates by opening and closing the recirculation valve. There is a correction control system that calculates the amount of change in the water supply flow rate by comparing the flow rates and calculates a correction amount based on this amount of change in the water supply flow rate, and adds the correction amount of this correction control system to the amount of water supply by the main control system. A water supply control device for a steam generating plant, characterized in that 2. A correction control system according to claim 1, wherein the correction control system detects a feed water flow rate, a means for setting a target water feed flow rate at the start of switching of the water feed pump, a feed water flow rate which fluctuates by opening and closing a recirculation valve, and Steam generation comprising means for comparing target water supply flow rates, means for calculating a water supply flow rate correction amount based on the water supply flow rate change amount obtained by the comparison, and means for adding the water supply flow rate correction amount Water supply control device for plant. 3. The water supply control apparatus for a steam generating plant according to claim 2, further comprising means for storing the detected value of the water supply flow rate, wherein the detected value of the water supply flow rate at the start of switching the water supply pump is set as the target water supply flow rate. . 4. The steam according to claim 2, wherein the means for calculating the feed water flow rate correction amount comprises a constant or a gain element having a variable function for fluctuations in the feed water flow rate, and an integration element for setting an integration time constant. Water supply control device for generating plant. 5. A water supply controller for controlling the water level of a steam generating plant to a target value, which has a steam generator, a plurality of water supply pumps for supplying water to the steam generator, and a recirculation valve provided in these water supply pumps. In the main control system for controlling the feed water flow rate of the water feed pump based on the water level detection value of the steam generator, the switch means is turned off at the start of switching of the water feed pump, and the feed water flow rate signal at this time is stored in the memory circuit. Remember
While setting the target water supply flow rate, while the water supply pump is being switched, the target water supply flow rate and the water supply flow rate signal that fluctuates due to opening and closing of the recirculation valve are compared to obtain the water supply flow rate change amount, and this water supply flow rate change amount is used as the water supply flow rate correction circuit. A correction control system for calculating the feed water flow rate correction signal by inputting to the water supply flow rate control signal of the main control system is added to the feed water flow rate correction signal of the correction control system. Control device.