JPH05231605A - Feed water controller - Google Patents

Abstract

PURPOSE:To permit smooth control of a feed water recirculation control valve by adopting the maximum algebraic difference in a predetermined period of time when the minimum suction flow amount difference of a feed water pump is negative. CONSTITUTION:A fuzzy controller 60 is constituted to a preprocessing unit 61, an post processing unit 62, a fuzzy rule base 63 and a fuzzy inference engine 64 while the post processing unit 62 is constituted of a limiter 65 and an integrator 66. The preprocessing unit 61 takes in a valve opening degree difference E to effect a predetermined preprocessing and outputs the valve opening degree difference E, the maximum valve opening degree difference E1 and a past valve opening degree difference E2. The fuzzy inference engine 64 reads the fuzzy rule base 63, in which control rules are described, and estimates inputs E, E1, E2 in accordance with a described control rule. The post processing unit 62 outputs a valve opening degree signal through the limiter 65 and the integrator 66. According to this method, smooth control of a feed water recirculation control valve can be effected.

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 controlling the water supply supplied to a boiler or a nuclear reactor, and more particularly to a water supply control device for a water supply pump which controls a boiler water supply flow rate by a rotation speed.

[0002]

2. Description of the Related Art In thermal power plants and nuclear power plants,
A water supply control device is installed to control the water supply to the boiler and reactor.

FIG. 7 shows an example of a water supply control system in a thermal power plant. Water supply to a boiler 1 flows in from a water supply source pipe 2, passes through a suction flow rate detector 3, and is driven by a steam turbine 4. After the pressure is increased by the water supply pump 5, it passes through the discharge flow rate control valve 6, the discharge flow rate detector 7 and the boiler water supply pipe 8,
It is supplied to the boiler 1. The rotation speed of the turbine 4 is controlled by operating the steam control valve 9, and the rotation speed detector 1
Detected at 0. In order to ensure a minimum suction flow rate in the water supply pump 5, a water supply recirculation pipe 12 having a water supply recirculation adjustment valve 11 is connected between the discharge side and the inflow side thereof.
It constitutes the recirculation system. A bypass valve 13 is connected in parallel to the discharge flow rate control valve 6.

The water supply control device having such a configuration is controlled as follows. That is, the water supply amount request signal 20 from the master automatic control system is obtained by the adder 21 with a deviation from the actual discharge flow rate signal of the discharge flow rate detector 7 provided on the outlet side of the water supply pump 5, and the water supply regulator is obtained. After being subjected to proportional-plus-integral processing at 22, it is input to the switching controller 23. The minimum rotation speed setting signal 24 and the actual rotation speed signal from the rotation speed detector 10 provided on the turbine shaft are also input to the switching regulator.
Based on these signals, the switching controller 23 selects an output signal depending on whether the turbine speed is equal to or greater than the minimum speed, and distributes the signals to the speed controller 25 and the discharge flow rate controller 26. One of the signals output from the switching controller 23 is proportionally processed by the rotation speed controller 25, and then guided to the steam control valve 9 of the steam turbine 4, and the speed of the steam turbine 4, that is, the rotation speed of the water supply pump 5. The discharge flow rate is controlled by controlling The other signal output from the switching controller 23 is proportional-integral-processed by the discharge flow rate controller 26, and then controls the discharge flow rate control valve 6 to control the discharge flow rate of the water supply pump 5.
In the two discharge flow rate control, when the rotation speed of the steam turbine 4 exceeds the minimum rotation speed, the discharge flow rate is controlled by controlling the rotation speed of the feed water pump 5, and the full-open signal is output from the discharge flow rate controller 26. Is output, and the discharge flow rate control valve 6 is fully opened. When the rotation speed of the steam turbine 4 is about to shift to the minimum rotation speed or less, the steam control valve 9 is controlled so that the rotation speed of the turbine 4 becomes the minimum rotation speed, and the discharge flow rate controller 26 is fully closed to fully opened. To output a continuous signal to control the discharge flow rate control valve 6 to control the discharge flow rate. In addition, the minimum suction flow rate request signal 2 determined by the number of revolutions of the water supply pump 5, etc.
In the adder 28, the deviation 29 from the signal from the suction flow rate detector 3 provided on the inlet side of the water supply pump 5 is obtained, and after the proportional integration processing is performed by the water supply recirculation controller 30, By controlling the opening degree of the circulation adjusting valve 11, the minimum flow rate of the water supply pump 5 is secured and the water supply pump 5 is prevented from overheating.

FIG. 8 shows the details of the water supply control device centering on the water supply recirculation controller 30. The function generator 40 receives the signal from the rotation speed detector 10 of the steam turbine as input. A required minimum suction flow rate request signal 27 is output according to the value. As described above, the adder 28 takes the difference between the minimum suction flow rate request signal 27 and the signal from the suction flow rate detector 3, and outputs the suction flow rate deviation 29.

This suction flow rate deviation 29 is converted from the number of rotations into a valve opening degree by a converter 31, and becomes a feed water recirculation adjusting valve target opening degree signal 32. This target opening signal 32 is subjected to proportional limit processing by the control gain 34 after subtracting the feedback signal of the valve opening setting signal 36 in the adder 33,
It is an input to the integrator 35. The integrator 35 integrates this signal to obtain a valve opening setting signal 36. This valve opening degree setting signal 36 is affected by the temporary delay 51 and dead time 52 due to the actuator of the water supply recirculation adjusting valve 11, and the valve opening degree 53.
Becomes

By operating the water supply recirculation adjusting valve 11 in this manner, the suction flow rate of the water supply pump 5 is controlled to be the minimum necessary amount or more.

[0008]

In the conventional control device,
It is necessary to increase the gain of the control gain 34 of the feedwater recirculation adjusting valve 11 for the purpose of preventing overheating to some extent. In this case, if the gain is increased, the control of the water supply recirculation adjustment valve 11 becomes unstable. Therefore, a limit is set in the decreasing direction so that the speed in the closing direction is slowed to prevent divergence.

However, since the discharge flow rate and the recirculation flow rate influence each other via the suction flow rate, the feed water recirculation controller 30
And the rotational speed adjuster 25 interfere with each other, and each flow rate causes hunting. In order to avoid this, it is conceivable to reduce the lower limit of the control gain 34 to reduce the closing speed. However, if the closing speed is reduced, hunting is suppressed, but an excessive suction against the required minimum suction flow rate request signal 27 is generated. Since the flow rate is long, the power required to drive the pump becomes excessive and the power loss of the system increases.

As described above, in the prior art, the feed water recirculation controller is required to have a high responsiveness, so that it has a drawback that the flow rate causes hunting. Further, if the speed in the closing direction is suppressed in order to suppress the hunting, it will be closed. The directional stability increases, but the controllability deteriorates, resulting in an increase in power loss.

An object of the present invention is to provide a water supply control device which has a good quick response in the opening direction of the water supply recirculation control valve and a good stability and controllability in the closing direction. To do.

[0012]

The water supply control device of the present invention comprises a variable speed prime mover, a water supply pump driven by the variable speed prime mover, and recirculation for returning water on the outlet side of the water supply pump to the inlet side. In a water supply system including a system, a water supply recirculation adjustment valve provided on the recirculation system, and a water supply recirculation controller that controls the water supply recirculation adjustment valve, a pump minimum suction flow rate deviation of the water supply pump When is negative, a fuzzy controller that adopts the maximum algebraic deviation within a predetermined time is provided.

[0013]

In the water supply control apparatus of the present invention configured as described above, when the suction flow rate deviation is positive, that is, when the suction flow rate is insufficient and the recirculation flow rate needs to be increased, the high speed control is performed as in the conventional case. In response, open the feedwater recirculation control valve at high speed to prevent overheating. On the other hand, when the suction flow rate deviation is negative, that is, when the suction flow rate is excessive and the recirculation flow rate may be reduced, the maximum deviations E1 and E2 are controlled by the larger value. Therefore, once an open command is issued,
The closing operation is not performed for a certain time. When the closing command continues for a certain time, the closing operation is started. By doing so, wasteful opening / closing operations can be suppressed and smooth control can be performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a constitutional example of a feedwater recirculation controller 30 of a feedwater control system in the apparatus of the present invention, which has the same constitution as that of FIG. 8 except for a fuzzy controller 60. That is, the water supply recirculation controller 30 is a converter 31 for converting the suction flow rate deviation 29 into the target opening signal 32 of the water supply recirculation adjustment valve.
And an adder 33 that takes the difference between the target opening signal 32 and the valve opening setting signal 36 of the feedwater recirculation adjusting valve, and the valve opening setting signal 36.
And a fuzzy controller 60 for calculating

The fuzzy controller 60 includes a pre-processing unit 61 for pre-processing input, a post-processing unit 62 for post-processing output, a fuzzy rule base 63 describing fuzzy control rules, and a fuzzy inference for fuzzy inference. It is composed of an engine 64. The post-processing unit 62 includes a limiter 65 and an integrator 66.

In the device of the present invention having such a configuration, the suction flow rate deviation 29 is converted from the rotational speed into the valve opening degree by the converter 31, and becomes the target opening degree signal 32 of the feed water recirculation adjusting valve. This target opening degree signal 32 is supplied to the valve opening degree setting signal 3 by the adder 33.
After the feedback signal of No. 6 is subtracted, the fuzzy controller 60 performs a control calculation to obtain the valve opening signal 36. Hereinafter, the suction flow rate of the water supply pump 6 is controlled to be equal to or more than the minimum required amount in the same manner as the conventional technique.

Inside the fuzzy controller 60, the input valve opening deviation E is used for calculating a maximum value E1 for each constant time (ΔT) in the preprocessing section 61, as shown in FIG. The maximum value E2 is a value before ΔT time.

The preprocessing unit 61 takes in the valve opening deviation E, performs the above-mentioned preprocessing, and outputs the valve opening deviation E, the maximum valve opening deviation E1 and the past valve opening deviation E2. The fuzzy inference engine 64 deciphers the fuzzy rule base 63 describing the control rules, infers the inputs E 1, E1, E2 according to the described control rules, and outputs the variation ΔU of the valve opening setting signal 36. To do. Further, the post-processing unit 62 is
The limiter 65 and the integrator 66 enable the valve opening setting signal 36
To calculate.

The membership function of the fuzzy inference engine 64 is shown in FIG. 3 for inputs and FIG. 4 for outputs.
As shown in. An example of the control rule described in the fuzzy rule base 63 is shown in FIG.

In the apparatus of the present invention, when the feed water recirculation regulating valve is opened, it is opened at a high speed as in the conventional case, and when it is closed, it is controlled by the algebraic maximum value of the deviation within a certain period. Therefore, when it is necessary to increase the suction flow rate, control is performed with a high gain to follow at high speed. On the other hand, when it is necessary to reduce the suction flow rate, look at the situation for a while, and only after a certain time reduction signal continues, the maximum algebraic value of the deviation for a certain time,
That is, since the reduction operation is performed using the smallest negative deviation, smooth and stable control can be performed. Moreover, since the state is observed for a certain period of time, the deceleration can be made faster than in the conventional case, and as a result, the suction flow rate can be controlled closer to the minimum required amount, and the pump driving power can be reduced.

FIG. 6 (a) shows a simulation of the control result according to the prior art, in which an excessive flow rate flows for a long time, and hunting is recognized near the fully closed position of the valve. On the other hand, FIG. 6B shows a simulation of the control result according to the present invention, in which the excess flow rate is small and hunting is not recognized.

As described above, according to the present invention, it is possible to provide a water supply control device in which control of the pump minimum suction flow rate is safe and stable, and power loss can be reduced.

[0024]

According to the present invention, the minimum suction amount of the pump can be controlled rapidly and stably, and the wasteful recirculation flow rate can be suppressed as a result, so that a water supply control device with less power loss of the pump can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a feedwater recirculation controller in a device of the present invention.

FIG. 2 is an explanatory diagram showing an input process of a fuzzy controller in the device of the present invention.

FIG. 3 is an explanatory diagram illustrating an input membership function in the device of the present invention.

FIG. 4 is an explanatory diagram illustrating an output membership function in the device of the present invention.

FIG. 5 is an explanatory diagram illustrating a fuzzy control rule in the device of the present invention.

6A is an explanatory view illustrating a simulation result of a conventional device, and FIG. 6B is an explanatory view illustrating a simulation result of the present invention device.

FIG. 7 is a system diagram of a conventional water supply control system.

FIG. 8 is an explanatory view showing a water supply recirculation controller in a conventional device.

[Explanation of symbols]

1 ... Boiler, 2 ... Water supply source pipe, 3 ... Suction flow rate detector, 4 ...
Steam turbine, 5 ... water supply pump, 6 ... discharge flow control valve,
7 ... Discharge flow rate detector, 8 ... Boiler water supply pipe, 9 ... Steam control valve, 10 ... Rotation speed detector, 11 ... Water supply recirculation adjusting valve, 1
2 ... Water supply recirculation pipe, 13 ... Bypass valve, 22 ... Water supply regulator, 23 ... Switching regulator, 25 ... Rotation speed regulator, 26 ...
Discharge flow rate controller, 29 ... Suction flow rate deviation, 30 ... Water supply recirculation controller, 36 ... Valve opening setting signal, 60 ... Fuzzy controller, 62 ... Post-processing section, 65 ... Limiter, 66 ...
Integrator,

Claims (1)

[Claims] 1. A variable speed prime mover, a feed water pump driven by the variable speed prime mover, a recirculation system for returning water on the outlet side of the water feed pump to the inlet side, and a recirculation system provided on the recirculation system. In a water supply system including a water supply recirculation adjustment valve and a water supply recirculation controller that controls the water supply recirculation adjustment valve,
A water supply controller comprising a fuzzy controller that adopts a maximum algebraic deviation within a predetermined time period when the pump minimum suction flow rate deviation is negative.