JPH10149219A - Controller for flow rate control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically and speedily open even a flow rate control value with inferior flow rate characteristics to shorten futile time, and to perform stable control by automatically and securely performing the valve opening operation throughout the time of a non-outflow extent of the flow rate control valve. SOLUTION: When the temperature of reheated steam 1 rises above a set value 9, the flow rate control valve 4 is opened. A deviation signal monitor switch 26 outputs an ON signal 25 to the set S side of a flip-flop circuit 32 immediately when a signal 11 of a difference is slightly generated. Consequently, a switching signal is outputted to switches 19, 23, and 24, which are switched to set sides (a). The switch 19 is so switched as to output a 100% signal from a signal generator 33. Then a variation rate limiter 22 outputs a variation rate addition signal 21. This variation rate addition signal 21 is inputted from the switches 23 and 24 to a PI controller 16 with a high/low signal limiter to controls the flow rate control valve 4 for quick valve closing operation at the variation rate of the variation rate addition signal 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a flow control valve.

[0002]

2. Description of the Related Art Conventionally, control devices for controlling the flow rate of a fluid by adjusting the opening of a flow control valve have been implemented in various fields.

For example, in a reheat steam temperature controller for a boiler, water is injected and mixed into the reheat steam from the reheater to protect the steam turbine so that the reheat steam does not exceed a set temperature. Control.

FIG. 2 shows an example of such a case. A spray mixer 3 is provided in a reheat steam pipe 2 through which reheat steam 1 flows.
A water supply pipe 5 provided with a flow control valve 4 in the spray mixer 3
Is connected to supply water 6 so that the temperature of the reheated steam 1 is adjusted.

In order to control the temperature of the reheat steam 1, the temperature of the reheat steam 1 is detected by a thermometer 7, and a detected value 8 of the temperature from the thermometer 7 and a set value 9 of the reheat steam temperature are set. Is input to a subtractor 10 to perform subtraction.
The difference signal 11 subtracted by 0 is input to a PI controller (proportional integrator) 12, and an opening command 13 is output to the flow control valve 4 so that the difference signal 11 disappears. 4
The flow control valve 4 controls the amount of water 6 to be mixed with the reheat steam 1 so that the temperature of the reheat steam 1 does not exceed the set value 9. ing.

However, in the control device for controlling the opening of the flow control valve 4 as described above, the signal 11 indicating the difference between the detected value 8 and the set value 9 is generated, so that the flow control valve 4 is closed. When the control that is gradually opened from the state is performed, as shown in FIG.
There may be a non-outflow opening A where the fluid does not flow at all even if the opening before and after the opening becomes large.

[0007] As described above, the phenomenon that the fluid does not flow even when the valve opening degree becomes large to a certain degree is generally caused by the supply fluid (water 6 in the example of FIG. 2) and the supplied fluid (water 6 in the example of FIG. 2). It is considered that this occurs when the pressure difference from the reheat steam 1) is small. Not only the factor due to the difficulty of fluid flow based on such a small pressure difference but also the flow control valve 4
It is known that the performance (flow characteristics) of the device itself is significantly related.

[0008] As shown in FIG.
The flow control valve 4 has a large non-outflow opening A such that no fluid flow occurs even when the opening of the flow control valve 4 becomes about 20%. The start of the valve opening operation 4 causes a large dead time between the time when the flow control valve 4 starts opening and the time when the fluid actually starts flowing out. The control delay caused by the dead time causes the reheat steam 1 to be set. It is conceivable that the temperature will be greatly exceeded.

For this reason, as shown in FIG. 2, the opening degree command 1 outputted from the PI controller 12 to the flow control valve 4
3 and the gain G corresponding to P (proportional) of the PI controller 12
A function generator 14 which outputs a _1, and a function generator 15 which outputs a PI controller 12 of the I (integral) component of the gain G ₂ by entering the opening command 13, the opening of the flow regulating valve 4 An embodiment is provided in which the gain of the PI adjuster 12 can be changed according to the degree.

FIG. 4 shows an example of the relationship between the opening degree of the flow control valve 4 and the gains G ₁ and G ₂ by the function generators 14 and 15. In the case of FIG. Opening 0
%, The gains G ₁ , G ₂ are 5 when the opening is 15%, the gains G ₁ , G ₂ are 0.2 when the opening is 15%, and the gains G ₁ , G ₂ are 0 when the opening is 20% or more. .05.

The gains G ₁ ,
G ₂ is, be the same value as in Figure 4, or different values may have been, but large gain G ₁ at a small opening of the flow regulating valve 4, as shown in FIG. 4 have a tendency to output values B G _2.

As shown in FIG. 2, the opening degree command 13 from the PI controller 12 is input to the function generators 14 and 15, so that the fluid does not flow even when the flow control valve 4 starts to open.
When the control is performed such that the gains G ₁ and G ₂ of the large value B are output to the PI controller 12 at the time of ( ₁₎ , the operating speed of the valve opening when the flow control valve 4 is opened from the closed state is reduced. As a result, the dead time is reduced, and the control delay due to the dead time is reduced.

[0013]

However, as described above, the opening degree command 13 from the PI controller 12 is transmitted to the function generator 1.
In the control system in which the gains G ₁ and G ₂ having large values B are output to the PI controller 12 at the non-outflow opening A where the fluid does not flow even when the flow control valve 4 starts to open, It is difficult to match the timing of applying the gains G ₁ and G ₂ of the large value B in FIG. 4 to the range of the non-outflow opening A shown in FIG. If the timings of the gains G ₁ and G ₂ of the large value B of 4 are shifted, the above-mentioned dead time occurs or the large value B of the gain G _{1 of} FIG. , resulting in problems such as control of the supply amount of water 6 is rapidly increased reheat steam temperature by G ₂ is added becomes unstable.

When the non-outflow opening A in FIG. 3 changes due to the deviation of the flow characteristic T of the flow control valve 4, the gain G ₁ based on the opening command 13 in the function generators 14 and 15 each time. , has a problem that it is necessary to re-adjust the G _2.

The present invention has been made in view of such circumstances, and is applicable to a flow control valve having a poor flow characteristic such that the dead time from the start of the valve opening operation of the flow control valve to the actual flow of the fluid is long. Provided is a control device for a flow control valve which can automatically and rapidly open a flow control valve until a fluid starts flowing according to the flow characteristics of the flow control valve, thereby reducing dead time and performing stable control. It is intended to be.

[0016]

SUMMARY OF THE INVENTION According to the present invention, a difference signal from a subtractor for subtracting a set value and a detected value is inputted, and an opening is set to a flow control valve so that the difference signal disappears. PI controller with high / low signal limiter that outputs command and 100% on set side
A first switch for inputting a signal and inputting a 0% signal to the reset side to switch and output a signal, and a change rate limiter for inputting a signal from the first switch and outputting a change rate added signal When,
A second switch for inputting the change rate addition signal from the change rate limiter to the set side, inputting a 100% signal to the reset side, and switching and outputting to the high signal side of the high / low signal limiter; A third switch for inputting the change rate addition signal from the change rate limiter, inputting a 0% signal to the reset side, and switching and outputting the signal to the low signal side of the high / low signal limiter; A deviation signal monitor switch that outputs an ON signal when the difference signal exceeds a certain set value, and a flow signal that outputs an ON signal when the detected value of the flow meter provided downstream of the flow control valve exceeds a certain set value A first switch when an ON signal is input from a monitor switch and the deviation signal monitor switch;
A flip-flop circuit for switching the second and third switches to a set side, respectively, and for switching the first, second and third switches to a reset side when an ON signal is input from the flow rate signal monitor switch; And a control device for a flow control valve, characterized by comprising:

According to the present invention, even if the flow characteristics of the flow control valve change, the operation of rapidly opening the valve only during the non-outflow opening of the flow control valve can be automatically and reliably performed. It is possible to constantly and stably perform high-precision flow control without requiring any adjustment, and without causing a control problem such as a dead time or a sudden flow of fluid as in the related art. it can.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment of the present invention applied to the apparatus shown in FIG. 2. The temperature of the reheated steam 1 is detected by a thermometer 7 and the temperature from the thermometer 7 is detected. And a set value 9 of the reheated steam temperature are input to a subtractor 10 for subtraction, and a difference signal 11 obtained by the subtracter 10 is used as a PI controller with a high / low signal limiter. 16 has been entered.

The PI controller 16 with a height signal limiter outputs an opening command 17 to the flow control valve 4 to control the opening of the flow control valve 4 so that the difference signal 11 disappears. I have.

The PI controller 16 with a high / low signal limiter includes:
A high / low signal limiter 18 having a high signal side 18a and a low signal side 18b is integrally provided with a function of proportional integration.

Also, a first 100% signal from the signal generator 33 is input to the set side a and a 0% signal from the signal generator 34 is input to the reset side b to switch and output the signal. , A change rate limiter 22 which receives a signal 20 from the first switch 19 and outputs a change rate addition signal 21, and a change rate from the change rate limiter 22 on the set side a. A second switch 23 for receiving the additional signal 21 and inputting a 100% signal from the signal generator 35 to the reset side b and switching to the high signal side 18a of the high / low signal limiter 18 for output; The change rate adding signal 21 from the change rate limiter 22 is input to a, the 0% signal from the signal generator 36 is input to the reset side b, and the signal is switched to the low signal side 18b of the high / low signal limiter 18. It has a third switch 24 for outputting.

Further, the difference signal 11 from the subtractor 10
And a deviation signal monitor switch 26 for outputting an ON signal 25 when the difference signal 11 exceeds a certain small set value, and a flow meter downstream of the flow control valve 4 of the water supply pipe 5. And a flow signal monitor switch 30 for inputting a flow detection value 28 of the flow meter 27 and outputting an ON signal 29 when the flow detection value 28 exceeds a certain small set value.

In the figure, reference numeral 32 denotes a flip-flop circuit for switching the first, second and third switches 19, 23 and 24. The ON signal 25 from the deviation signal monitor switch 26 is set to the set S side. When input, the signal is held and the first, second and third switches 19, 23 and 24 are switched to the set side a.
When an ON signal 29 from 0 is inputted to the reset R side, a switching signal 31 for switching the first, second and third switches 19, 23 and 24 to the reset side b is outputted.

The operation of the embodiment shown in FIG. 1 will be described below.

In FIG. 1, in a normal state, the first, second, and third switches 19, 23, and 24 are switched to the reset side b, and the thermometer detects the temperature of the reheated steam 1. Since the detected value 8 from 7 is lower than the set value 9, the difference signal 11 indicates a negative value.
The controller 16 outputs an opening command 17 for closing (opening 0%) to the flow control valve 4.

In this state, when the detected value 8 of the temperature from the thermometer 7 which detects the temperature of the reheated steam 1 becomes higher than the set value 9 of the reheated steam temperature, the subtracter 10 sets a positive value. Is output to a PI controller 16 with a high / low signal limiter,
The PI controller 16 with a height signal limiter outputs an opening command 17 to the flow control valve 4 so as to eliminate the difference signal 11 and attempts to adjust the flow control valve 4 to open.

At this time, the deviation signal monitor switch 26
When the difference signal 11 slightly occurs due to the setting of a small value in the flip-flop circuit 3, the deviation signal monitor switch 26 immediately outputs the ON signal 25.
2 to the set S side, whereby the flip-flop circuit 32 outputs the switching signal 31 held on the set S side to the first, second, and third switchers 19, 23, and 2.
4 and the first, second and third switches 19 and 2
Each of 3, 24 is switched to the set side a.

Then, the first switch is a signal generator 33
Is output to output a 100% signal from the controller, and the 100% signal is input to the rate-of-change limiter 22. The rate-of-change limiter 22 causes the flow rate control valve 4 to rapidly open at the maximum speed. The signal 21 is output.

Since the second switch 23 and the third switch 24 are respectively switched to the set side a, the change rate adding signal 21 is transmitted to the high signal side 18a and the low signal side 18b of the high / low signal limiter 18. Thus, the PI controller 16 with the height signal limiter controls the flow rate control valve 4 to rapidly open the valve at the change rate of the change rate addition signal 21.

Therefore, as shown in FIG.
The flow control valve 4 has a predetermined opening (FIG. 3).
Even in a valve in which the water 6 does not flow out up to about 20% opening), the valve opening operation at the non-outflow opening A is rapidly performed by the change rate addition signal 21, thereby reliably reducing the dead time. can do.

When the water 6 starts to flow due to the opening operation of the flow control valve 4, the flow meter 27 immediately detects that the water 6 has flown and outputs a detected flow value 28 to the flow signal monitor switch 30.

Since a small set value is set in the flow signal monitor switch 30, the ON signal 29 is output to the reset R side of the flip-flop circuit 32 with the water 6 flowing slightly. As a result, the flip-flop circuit 32 outputs the switching signal 31 held on the reset R side to each of the first, second, and third switches 19, 23, and 24, and performs the first, second, and third switching. Vessels 19, 23, 2
4 is switched to the reset side b.

The first switch 19 outputs the 0% signal from the signal generator 34 by being switched to the reset side b, while the second switch 23 outputs the 0% signal from the signal generator 35. The 100% signal is output to the high signal side 18a of the high / low signal limiter 18, and the third switch 24 is operated by the signal generator 36.
0% signal from the low signal side 18b of the high / low signal limiter 18.
Will be output to

Therefore, the PI controller 16 with the high / low signal limiter
Is the subtractor 1 between the opening of 0% and 100%.
The opening command 17 is output to the flow control valve 4 so that the signal 11 having a difference from 0 disappears.

As described above, when the flow control valve 4 is opened, as shown in FIG. 3, a flow control with a large non-outflow opening A and a poor flow characteristic T having no large flow of fluid (water 6). The first, second, and third valves are also provided for the valve 4 during the non-outflow opening degree A in FIG.
Are switched to the set side a, the valve is rapidly opened by the change rate addition signal 21, and the opening degree of the flow control valve 4 is increased to generate the flow of the fluid (water 6). Immediately, the first, second, and third switches 19, 23, and 24 are switched to the reset side b, and the difference signal 11 from the subtractor 10 is output.
The flow control valve 4 is controlled by the opening degree command 17 for eliminating
The opening degree of the flow control valve 4 is controlled, so that even if the flow characteristic of the flow control valve 4 changes, the operation of rapidly opening the valve only during the non-outflow opening A of the flow control valve 4 is automatically performed. Therefore, the present invention can be implemented reliably without any adjustment, and does not cause a control problem such as a dead time or a sudden flow of fluid as in the related art.

In the case shown in the figure, an example of a reheat steam temperature control device of a boiler in which water is injected and mixed with the reheat steam so that the reheat steam does not exceed the set temperature has been described. However, the present invention can be applied to control of any flow control valve other than the above.

[0038]

According to the present invention, even when the flow rate characteristic of the flow control valve changes, the operation of rapidly opening the valve only during the non-outflow opening of the flow control valve is automatically and reliably performed. It can be implemented and therefore does not require any adjustment, does not cause a control problem such as a conventional dead time or a sudden flow of fluid, and is always stable and highly accurate flow rate adjustment. Can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a conventional control device for a flow control valve.

FIG. 3 is a flow rate characteristic diagram showing a relationship between an opening degree of a flow rate control valve and a flow rate of a fluid.

FIG. 4 is a diagram illustrating an example of a gain of the function generator provided in FIG. 2;

[Explanation of symbols]

 4 Flow control valve 8 Detected value 9 Set value 10 Subtractor 11 Difference signal 16 PI controller with high / low signal limiter 17 Opening command 18 High / low signal limiter 18a High signal side 18b Low signal side 19 First switch Reference Signs List 20 signal 21 change rate addition signal 22 change rate limiter 23 second switch 24 third switch 25 on signal 26 deviation signal monitor switch 27 flow meter 28 detection value 29 on signal 30 flow signal monitor switch 32 flip-flop circuit a Set side b Reset side

Claims (1)

[Claims] A high / low signal limiter for inputting a difference signal from a subtracter for subtracting a set value and a detected value and outputting an opening command to a flow control valve so that the difference signal disappears. A PI controller, a first switch for inputting a 100% signal to the set side and inputting a 0% signal to the reset side to switch and output a signal, and inputting a signal from the first switch. A rate-of-change limiter for outputting a rate-of-change additional signal; a rate-of-change additional signal from the rate-of-change limiter input to the set side;
A second switch for inputting a% signal to switch to a high signal side of the high / low signal limiter, and a change rate addition signal from the change rate limiter to the set side and a 0% signal to the reset side. A third switch for inputting and switching to the low signal side of the high / low signal limiter, and a deviation signal monitor switch for outputting an ON signal when a difference signal from the subtractor exceeds a certain set value. A flow signal monitor switch that outputs an ON signal when a detection value of a flow meter provided downstream of the flow control valve exceeds a certain set value, and the first signal when an ON signal is input from the deviation signal monitor switch. Flip-flop for switching the first, second, and third switches to the set side, and switching the first, second, and third switches to the reset side when an ON signal is input from the flow rate signal monitor switch. Circuit. Controller of the flow control valve to.