JPH07102907A - Boiler water drum water level control device - Google Patents

Abstract

PURPOSE:To improve responsiveness by outputting an adding signal to a feedwater valve according to the amount of change in a drum water level commanding signal and compensating the amount of an increase and decrease in the opening degree of a feedwater valve by means of a feed forward feedwater valve operating quantity signal in the direction opposite to the direction to increase and decrease the opening degree of the feedwater valve by means of a feedback feedwater valve operating quantity signal. CONSTITUTION:A feedwater feed operating quantity signal alpha is output by a water level control section 6 from a drum water signal command A and a drum water level feedback signal B. A feedwater valve operating quantity signal beta is output from a drum outflow steam flow rate signal C and a drum feedwater flow rate signal D through a water level compensation control section 10. A feedwater valve operating quantity signal delta is added to the feedwater quantity operating signals alpha and beta, and total feedwater valve operating signal E is output to a feedwater valve 20 to control the water level of a boiler water drum. The feedwater valve operating quantity signal deltaconvert the amount of change in the drum water level command signal A into a detection signal F and becomes a compensation signal through a primary delay device 15. This constitution serves to compensate decreased quantity by feed forward control and to improve responsiveness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level control device for a steam drum which constitutes steam generating equipment in a steam power plant.

[0002]

2. Description of the Related Art As a drum water level control method, a one-element system for detecting only the drum water level and controlling the feed water flow rate according to the change and a two-element system for detecting the steam flow rate in addition to the drum water level and performing advance control There is a formula and a three-element formula that controls the feed water flow rate by detecting the drum water level and steam flow rate.

FIG. 5 shows an example of a schematic system for controlling the water level of the steam drum.

In the figure, water is heated by a economizer (not shown) or the like through a water supply valve 20 and flows into a steam drum 18. The hot water that has flowed into the steam / water drum 18 is supplied to an evaporator or the like (not shown), is further heated, and returns to the steam / water drum 18.
Hot water and steam are stored in the steam drum 18, and the steam is supplied to a turbine or the like.

In the water level controller 19, the drum water flow rate signal D from the drum water flow rate detector 8 and the drum water level feedback value signal B from the drum water level detector 5 arranged in the water supply pipe.
And a drum outflow steam flow rate signal C from the drum outflow steam flow rate detector 7 are input, and a water supply valve total operation amount signal E is output to the water supply valve 20 as a control signal.

Here, the water level control device 19 will be described with reference to FIG.

In the figure, the drum water level command value signal A set by the drum water level command value setter 1 is limited to a predetermined value by an upper and lower limit limiter 2, and this upper and lower limit limiter 2
The output signal of is input to the adder / subtractor 4 via the change rate limiter 3. Further, the drum water level feedback value signal B detected by the drum water level detector 5 is input to the adder / subtractor 4 as a negative feedback value.

In the adder / subtractor 4, the deviation signal obtained by addition and subtraction according to the symbols shown is input to the water level controller 6.
The water level control section 6 outputs a water supply valve operation amount signal α which is an operation variable for suppressing and controlling the expansion of the deviation signal between the drum water level command value signal A and the drum water level feedback value signal B.

On the other hand, the drum outflow steam flow rate signal C detected by the drum outflow steam flow rate detector 7 and the drum feedwater flow rate signal D detected by the drum feedwater flow rate detector 8 are input to the adder / subtractor 9 and the above-mentioned drum. An amount obtained by subtracting the drum feed water flow rate signal D from the outflow steam flow rate signal C, that is, a volume reduction amount signal of the drum content per unit time is output,
It is input to the water level compensation control unit 10.

The water level compensation control unit 10 outputs an operation variable for suppressing the expansion of this signal. This output signal is limited to a predetermined value by the upper and lower limit limiter 11, and becomes the water supply valve operation amount signal β.

Next, the water addition valve operation amount signal α and the water supply valve operation amount signal β are added by the adder / subtractor 12. This output signal is limited to a predetermined value by the upper and lower limit limiter 13, and is supplied as the water supply valve total operation amount signal E to the water supply valve 20 of the water / water drum 18.
Is output to control the water supply flow rate to control the water level of the steam drum 18.

[0012]

However, the conventional water level control device shown in FIG. 6 has a problem that the water level control characteristic, particularly responsiveness, is not good.

That is, that is, the water level control device 19
Performs three-element control, and also performs combined control of feedback control and feedforward control, but even in this case, there is a problem that the conventional method cannot always respond quickly to fluctuations that occur when the command value is changed. .

First, the case where the drum water level command value signal A is constant will be described with reference to FIG. 7, assuming that the feed water flow rate Qw fluctuates at time t1 due to disturbance or the like. In this case, the feedforward control is immediately performed based on the decrease of the steam flow rate Qv-the feed water flow rate Qw. As a result, the water supply valve total operation amount signal E increases and the water supply flow rate Qw gradually increases. After that, feedforward control is performed in a direction in which the feedwater flow rate Qw decreases and stabilizes at time t2, that is, feedforward control is performed as indicated by the chain line in the figure. Further, at time t3, the drum water level feedback value signal B rises, but the feedforward control suppresses the rise of the drum water level feedback value signal B.

Thus, the feed water flow rate Qw and the steam flow rate Qv
Since the feed-forward control precedes the control of the difference of, it is possible to follow the difference more quickly than in the case of the solid line shown in the figure which only includes the feedback control.

However, a case where the drum water level command value is changed to change the drum water level from the case where the water level of the steam / water drum 18 is held at an arbitrary value will be described with reference to FIG. When the drum water level command value signal A is increased stepwise, the water supply amount operation amount signal M is correspondingly increased.
Is increased.

At this time, the feed water flow rate Qw increases at time t2, and the preceding signal component by the feed forward control is in the opposite direction to the changing direction of the drum water level command value signal A in accordance with the deviation between the feed water flow rate Qw and the steam flow rate Qv. The operation amount is calculated and output.
Further, when the drum water supply flow rate detector 8 returns to the same value as before time t1 at time t3, it also acts to reduce the water supply amount operation amount signal M in the direction opposite to the changing direction of the drum water level command value signal A.

Therefore, the compensation amount of the feedforward control acts in the direction opposite to the original direction, and the feed water flow rate Qw.
And the steam flow rate Qv become equal, there is a problem that the response cannot be made at high speed and the followability is poor.

Further, referring to FIG. 9, time t1
When the drum water level command value signal A increases stepwise, the drum feed water flow rate signal D and the drum outflow steam flow rate signal C
The deviation of the water supply valve total operation amount signal E acts to decrease the increase of the water supply valve total operation amount signal E. Therefore, similarly to FIG. 8, at time t2, the drum water level feedback value signal B finally follows.

Therefore, it is an object of the present invention to provide a water level control device for a water / water drum which can obtain excellent water level control characteristics in the water level control of the water / water drum of a steam generating facility.

[0021]

According to a first aspect of the present invention, a feedback water supply valve operation amount signal obtained by feedback control calculation of a deviation signal between a drum water level command value signal and a drum water level feedback value signal, and a drum outflow steam. The deviation signal between the flow rate signal and the drum water supply flow rate signal is feed forward controlled, and the addition signal obtained by adding the feed forward water supply valve operation amount signal obtained by calculation is used as the water supply valve operation amount signal to open and close the water supply valve. In a water level control device for a water / water drum that controls the water level of a water drum, when the drum water level command value signal changes abruptly, the feedback water supply valve operation amount signal increases or decreases the opening of the water supply valve in the opposite direction. The amount of change in the drum water level command value signal is adjusted so as to compensate for the operation amount signal corresponding to the amount by which the feedforward water supply valve operation amount signal increases or decreases. Flip and is obtained by so providing a means for outputting a compensation signal to increase or decrease the sum signal to be output to the water supply valve.

According to a second aspect of the present invention, a feedback water supply valve operation amount signal obtained by performing feedback control calculation of a deviation signal between the drum water level command value signal and the drum water level feedback value signal detected by the drum water level detector is output. A water level control unit, a water level compensation control unit that outputs a feedforward water feed valve operation amount signal obtained by feedforward control calculation of a deviation signal between the drum outflow steam flow rate signal and the drum feedwater flow rate signal, and the feedback water feed valve operation amount In the water level control device for the water / water drum, the drum water level command value is provided with an adder that opens and closes the water supply valve with the addition signal obtained by adding the signal and the feedforward water supply valve operation amount signal as the water supply valve operation amount signal. A signal is taken in, and when this signal changes suddenly, the feed water valve is operated by the feedback feed water valve operation amount signal. The rate of change detection signal is detected by detecting the amount of change in the drum water level command value signal so as to compensate for the operation amount signal corresponding to the amount by which the feedforward water valve operation amount signal increases or decreases in the direction opposite to the direction in which the opening degree is increased or decreased. A change rate detector for outputting, a first-order delay device for outputting a change rate detection signal detected by this change rate detector with a predetermined time delay, and an output signal from this first-order delay device for a predetermined range The upper and lower limit limiter for opening and closing the water supply valve as a water supply valve operation amount signal by adding the signal limited to the above to the addition signal of the adder is provided.

According to the third aspect of the present invention, a feedback water supply valve operation amount signal obtained by performing feedback control calculation of a feedback deviation signal between the drum water level command value signal and the drum water level feedback value signal detected by the drum water level detector is output. A water level control unit, a water level compensation control unit that outputs a feedforward water feed valve operation amount signal obtained by performing feedforward control calculation of a feedforward deviation signal between the drum outflow steam flow rate signal and the drum feedwater flow rate signal, and the feedback water supply In the water level control device for a water / water drum, which is provided with an adder that opens and closes the water supply valve by using an addition signal obtained by adding the valve operation amount signal and the feedforward water supply valve operation amount signal as the water supply valve operation amount signal, It takes in the water level command value signal, detects the amount of change in the drum water level command value signal, and changes it. A rate-of-change detector that outputs a rate detection signal, a primary delayer that outputs the rate-of-change detection signal detected by the rate-of-change detector with a predetermined time delay, and the drum water level command value signal changes abruptly. At this time, the primary controller is configured to compensate the operation amount signal corresponding to the increase / decrease of the feedforward water supply valve operation amount signal in the direction opposite to the direction in which the opening degree of the water supply valve is increased / decreased by the feedback water supply valve operation amount signal. A command value compensating water level control unit is provided for compensating the output signal from the delay device and adding the compensation calculation signal to the feedback deviation signal to obtain a signal for feedback control calculation.

[0024]

According to the first aspect of the present invention, when the drum water level command value signal suddenly changes, a compensation signal for increasing or decreasing the addition signal output to the water supply valve is output according to the amount of change of the drum water level command value signal. Thereby, the operation amount signal corresponding to the amount by which the feedforward water supply valve operation amount signal increases or decreases in the direction opposite to the direction in which the opening degree of the water supply valve is increased or decreased by the feedback water supply valve operation amount signal is compensated. Therefore, when the drum water level command value signal changes abruptly, the feedforward water feed valve operation amount signal based on the deviation signal between the drum water supply flow rate signal and the drum outflow steam flow rate signal can be used to increase or decrease the operation amount in the opposite direction to the original control direction. Because of the compensation, the drum water level feedback value signal can quickly follow.

According to the second aspect of the present invention, the change rate detector outputs the change rate detection signal as the change amount of the drum water level command value signal. The change rate detection signal is output by the first-order delay device as a signal having a predetermined time delay. This one
The output signal from the next delay device is limited to a predetermined range by the upper and lower limiter, and the signal is added to the addition signal of the adder and output to the water supply valve as a water supply valve operation amount signal. Thereby, the operation amount signal corresponding to the amount by which the feedforward water supply valve operation amount signal increases or decreases in the direction opposite to the direction in which the opening degree of the water supply valve is increased or decreased by the feedback water supply valve operation amount signal is compensated. Therefore, when the drum water level command value signal changes abruptly, the feedforward water feed valve operation amount signal based on the deviation signal between the drum water supply flow rate signal and the drum outflow steam flow rate signal can be used to increase or decrease the operation amount in the opposite direction to the original control direction. Because of the compensation, the drum water level feedback value signal can quickly follow.

According to the third aspect of the present invention, the change rate detector outputs the change rate detection signal as the change amount of the drum water level command value signal. As the change rate detection signal, a signal having a predetermined time delay is output by the first-order delay device. The output signal from the first-order delay device is subjected to compensation calculation by the command value compensation water level control unit, and this compensation calculation signal is added to the feedback deviation signal to be a signal for feedback control calculation. Thereby, the operation amount signal corresponding to the amount by which the feedforward water supply valve operation amount signal increases or decreases in the direction opposite to the direction in which the opening degree of the water supply valve is increased or decreased by the feedback water supply valve operation amount signal is compensated. Therefore, when the drum water level command value signal changes abruptly, the feedforward water feed valve operation amount signal based on the deviation signal between the drum water supply flow rate signal and the drum outflow steam flow rate signal can be used to increase or decrease the operation amount in the opposite direction to the original control direction. Because of the compensation, the drum water level feedback value signal can quickly follow.

[0027]

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

FIG. 1 is a block diagram of a water level control device for a steam / water drum showing a first embodiment of the present invention. The same reference numerals as those in FIG. 6 designate the same or corresponding parts. 1 is different from FIG. 6 in that a change rate detector 14, a first-order delay device 15, and an upper / lower limit limiter 16 are additionally provided.

The change rate detector 14 receives the drum water level command value signal A, detects the amount of change in the drum water level command value signal A per unit time, and outputs a change rate detection signal F. . The first-order delay device 15 outputs the output signal G with a predetermined delay time with respect to the change rate detection signal F. The upper / lower limit limiter 16 limits the output signal G to a predetermined upper / lower limit and outputs the water supply valve operation amount signal δ.

With the above configuration, the drum water level command value setting device 1
The drum water level command value signal A set by is limited by the upper / lower limit limiter 2 to a predetermined value, and the output signal of the upper / lower limit limiter 2 is input to the adder / subtractor 4 via the change rate limiter 3. . Further, the drum water level feedback value signal B detected by the drum water level detector 5 is input to the adder / subtractor 4 as a negative feedback value.

In the adder / subtractor 4, the deviation signal obtained by addition and subtraction according to the symbols shown is input to the water level controller 6.
The water level control section 6 outputs a water supply valve operation amount signal α which is an operation variable for suppressing and controlling the expansion of the deviation signal between the drum water level command value signal A and the drum water level feedback value signal B.

On the other hand, the drum outflow steam flow rate signal C detected by the drum outflow steam flow rate detector 7 and the drum feedwater flow rate signal D detected by the drum feedwater flowrate detector 8 are input to the adder / subtractor 9 and the above-mentioned drum. An amount obtained by subtracting the drum feed water flow rate signal D from the outflow steam flow rate signal C, that is, a volume reduction amount signal of the drum content per unit time is output,
It is input to the water level compensation control unit 10.

The water level compensation control unit 10 outputs an operation variable for suppressing the expansion of this signal. This output signal is limited to a predetermined value by the upper and lower limit limiter 11, and becomes the water supply valve operation amount signal β.

Next, the adder / subtractor 12 adds the feed water valve operation amount signal α, the feed water valve operation amount signal β, and a water feed valve operation amount signal δ described later. This output signal is the upper and lower limit limiter 1
It is limited to a predetermined value in 3 and is output to the water supply valve 20 of the water / water drum 18 as the water supply valve total operation amount signal E to control the water supply flow rate to control the water level of the water / water drum 18.

On the other hand, the change rate detector 14 detects the change amount of the drum water level command value signal A per unit time, and the change rate detection signal F is input to the first-order delay device 15. In the first-order delay device 15, an output signal G that operates with a predetermined delay time is set, and a feed water valve operation amount signal δ whose value is limited to a predetermined value by the upper / lower limit limiter 16 is output to the adder / subtractor 12.

In the adder / subtractor 12, the output signal limited to a predetermined value by the upper and lower limiter 13 is newly output to the water supply valve 20 as the water supply valve total operation amount signal E to control the water level of the water / water drum 18.

Here, the operation of the first embodiment will be described with reference to FIG. 2 corresponding to the conventional operation described in FIG.

First, at time t1, the drum water level command value signal A
If the water supply valve operation amount signal M increases rapidly, the water supply valve operation amount signal M starts to increase at time t2. When the water supply valve operation amount signal M increases, the steam flow rate Qv−the water supply flow rate Qw decreases as shown in the figure, and the drum water level feedback value signal B accompanying the feedforward control decreases in the direction opposite to the control direction by the feedback control. .

On the other hand, in the change rate detector 14, the water supply valve operation amount signal β is generated in accordance with the change amount of the drum water level command value signal A.
Output the change rate detection signal F for compensating the decrease of
The feed valve operation amount signal δ as a compensation signal is output to the adder / subtractor 12 via the next delay device 15 and the upper and lower limiter 16.
As a result, the reduction amount reduced by the feedforward control is supplemented by the compensation signal.

Further, as shown in FIG. 3, the tracking of the drum water level feedback value signal B when the drum water level command value signal A is increased stepwise at time t1 will be described.

First, since the drum water supply flow rate signal D increases in advance, the water supply valve operation amount signal β corresponding to the increase in the deviation between the drum water supply flow rate signal D and the drum outflow steam flow rate signal C is the water supply valve total operation amount signal. E is reduced, and the water level is reduced in the opposite direction to the original direction. In response to this, the change rate detector 14 increases the change rate detection signal F to increase the first-order lag device 1
Input to 5.

The output signal G is output from the first-order delay device 15 to the upper and lower limiter 16 with a predetermined time delay so that the feed water valve operation amount signal δ compensates for the decrease in the water feed valve operation amount signal β. Is input to the adder / subtractor 12. As a result, the feed water valve operation amount signal δ is output so as to cancel the compensation amount of the water level control device 19 shown in FIG. 6 that temporarily performs a reverse response by the feed forward control based on the deviation between the feed water flow rate and the steam flow rate. There is no increase or decrease in the overall water supply valve operation amount signal E, and the drum water level feedback value signal B follows the drum water level command value signal A at time t2 by the feedback control of the water level control unit 6.

As described above, according to the present embodiment, compared with the conventional drum water level feedback value signal B shown in FIG. 9, the drum water level command value signal A does not have a slow response, but the drum water level feedback value signal B. Responds rapidly and settles. This calculates the feed valve operation amount that quickly compensates for the water level of the water / water drum from the drum water level command value, and as a result, the effect of the temporary reverse response of the preceding control compensation amount based on the deviation between the water supply flow rate and the steam flow rate is calculated. By canceling and combining these two preceding control compensating elements in good condition to control the drum water level of the water / water drum which shows the operation of the integrating element with a large time constant.

By the way, the present invention is not limited to the configuration of the first embodiment, and can be implemented in the second embodiment shown in FIG. 4, for example, as in the first embodiment.

In the second embodiment, the change rate detector 14 detects the change amount of the drum water level command value signal A per unit time, and the change rate detection signal F is detected by the first-order delay device 15 with a predetermined time constant. Is calculated and output to the command value compensating water level controller 17.

Then, in the command value compensation water level controller 17,
A calculation is performed based on this value, and a signal that covers the decrease of the feed valve operation amount signal β of the first embodiment is output to the adder / subtractor 4. With such a configuration, the same effect as that of the first embodiment can be obtained and implemented.

As described above, when the drum water level command value signal A is suddenly changed, the operation amount in the direction opposite to the original control direction by the preceding control based on the deviation between the drum feed water flow rate signal D and the drum outflow steam flow rate signal C. In order to compensate the increase / decrease, the drum water level feedback value signal B can quickly follow up.

[0048]

As described above, according to the present invention, when the drum water level command value signal suddenly changes, the feedforward water supply valve is operated in the direction opposite to the direction in which the opening degree of the water supply valve is increased or decreased by the feedback water supply valve operation amount signal. Since the operation amount signal corresponding to the increase / decrease of the operation amount signal is compensated, the drum water level feedback value signal can quickly follow the drum water level command value signal.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a water level control device for a steam / water drum showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the first operation of FIG.

FIG. 3 is an explanatory diagram showing a second operation of FIG.

FIG. 4 is a configuration diagram of a water level control device for a steam / water drum showing a second embodiment of the present invention.

FIG. 5 is a system diagram for controlling the water level of a steam / water drum.

FIG. 6 is a configuration diagram of a water level control device for a steam drum showing a conventional example.

FIG. 7 is an explanatory diagram showing the first operation of FIG.

FIG. 8 is an explanatory diagram showing a second operation of FIG.

FIG. 9 is an explanatory diagram showing a third action of FIG. 6.

[Explanation of symbols]

 1 Drum water level command value setter 2, 11, 13, 16 Upper / lower limit limiter 3 Change rate limiter 4, 9, 12 Adder / subtractor 5 Drum water level detector 6 Water level controller 7 Drum outflow steam flow rate detector 8 Drum feed water flow rate Detector 10 Water level compensation control unit 14 Change rate detector 15 Primary delay device 17 Command value compensation water level control unit 18 Steam drum 19 Water level control device 20 Water supply valve

Claims (3)

[Claims] 1. A feedback water feed valve operation amount signal obtained by feedback control calculation of a deviation signal between a drum water level command value signal and a drum water level feedback value signal, and a deviation signal between a drum outflow steam flow rate signal and a drum feed water flow rate signal. Of the feed water feed valve operation amount signal obtained by adding the feed forward control calculation signal to the feed water control valve In the water level control device, when the drum water level command value signal changes abruptly, the feedforward water supply valve operation amount signal increases or decreases in the opposite direction to the direction in which the feedback water supply valve operation amount signal increases or decreases the opening of the water supply valve. In accordance with the amount of change in the drum water level command value signal so as to supplement the operation amount signal commensurate with Water level control device of the air-water drum, characterized in that it comprises means for outputting a compensation signal to increase or decrease the signal. 2. A water level control unit for outputting a feedback water supply valve operation amount signal obtained by performing feedback control calculation of a deviation signal between a drum water level command value signal and a drum water level feedback value signal detected by a drum water level detector, A water level compensation control unit that outputs a feedforward water feed valve operation amount signal obtained by feedforward control calculation of a deviation signal between the drum outflow steam flow rate signal and the drum feedwater flow rate signal, the feedback water supply valve operation amount signal, and the feedforward In a water level control device of a water / water drum equipped with an adder that opens and closes the water supply valve as an addition signal obtained by adding the water supply valve operation amount signal, the drum water level command value signal is taken in, When the signal suddenly changes, the feedback water valve operation amount signal is used to increase or decrease the opening of the water supply valve. Change rate detection that detects the change amount of the drum water level command value signal and outputs a change rate detection signal so as to compensate for the operation amount signal corresponding to the amount by which the feedforward water supply valve operation amount signal increases or decreases in the opposite direction. A first-order delay device that outputs a change-rate detection signal detected by the change-rate detector with a predetermined time delay, and an output signal from the first-order delay device as a signal limited to a predetermined range. A water level control device for a water / water drum, comprising: an upper / lower limit limiter for adding the addition signal of the adder to the feed water valve operation amount signal for opening / closing the water feed valve. 3. A water level control section for outputting a feedback water supply valve operation amount signal obtained by performing feedback control calculation of a feedback deviation signal between the drum water level command value signal and the drum water level feedback value signal detected by the drum water level detector. A water level compensation control unit for outputting a feedforward feed valve operation amount signal obtained by performing feedforward control calculation of a feedforward deviation signal between the drum outflow steam flow rate signal and the drum feedwater flow rate signal; and the feedback water supply valve operation amount signal. In the water level control device of the water / water drum, which is provided with an adder that opens and closes the water supply valve as an addition signal obtained by adding the feedforward water supply valve operation amount signal, the drum water level command value signal Captured, the amount of change in the drum water level command value signal is detected and the rate of change detection signal is output. Change rate detector, a primary delay device that outputs a change rate detection signal detected by this change rate detector with a predetermined time delay, and when the drum water level command value signal suddenly changes, Output from the primary delay device so as to compensate the operation amount signal corresponding to the amount of increase / decrease of the feedforward water supply valve operation amount signal in the direction opposite to the direction in which the opening degree of the water supply valve is increased / decreased by the feedback water supply valve operation amount signal. Compensate the signal,
A water level control device for a water / water drum, comprising: a command value compensating water level control unit that adds the compensation operation signal to the feedback deviation signal to provide a signal for feedback control operation.