JPH01314304A - Process controller - Google Patents

Abstract

PURPOSE:To maintain invariably stable and high controllability by using a two-degree-of-freedom PI or PID control means as a process quantity control means and subtracting the variation quantity of a command signal from the speed type control arithmetic output signal of a speed type two-degree-of- freedom control means. CONSTITUTION:The two-degree-of-freedom PI or PID control means 4 is applied as a steam flow rate control means to optimize both a steam flow rate target value follow-up characteristic and a disturbance suppression characteristic at the same time. Further, a subtracting means 6 subtracts the variation quantity DELTASVn of the steam flow rate target value signal SVn from the speed type control arithmetic output signal DELTACn to eliminate the double repetition of variation to an operation output signal MVn at the time of the variation of the steam flow rate target value signal SVn as to the combination of the steam flow rate target value signal SVn and speed type two-degree-of-freedom control means 4, thereby preventing vibration at the time of the variation of the steam flow rate target value signal SVn. Consequently, stable steam supply of high quantity is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a process control device that can safely and accurately control a process amount to be controlled.

(Prior art) In recent years, for example, industrial boilers have been equipped with multiple boilers,
Increasingly, boilers are being operated economically by optimally distributing load to each boiler according to steam consumption. In this case, each boiler must be accurately controlled to an optimally distributed steam flow rate. However, conventional boiler steam flow rate control devices have problems as described below, and recently, low-grade fuels such as pulverized coal and by-product fuels have been increasingly used as fuel, and the unit calorific value of the fuel has increased. The boiler characteristics are changing due to factors such as fluctuations in fuel flow rate and inability to accurately measure fuel flow rate, and the controllability of steam flow rate is becoming increasingly poor. has been requested to appear.

FIG. 3 is a block diagram showing an example of a configuration in which a conventional boiler steam flow rate control device is applied to a load distribution control system for multiple boilers. In addition, the boiler steam flow rate control device is
Of course, it is also applied to China and Germany, but typical applications are load distribution control systems for multiple boiler and train operation systems as shown in FIG.

In FIG. 3, the generated steam flow rate of each boiler is measured by steam flow rate detectors 21-1, 21-2. ..., detected by 21-n,
This detection signal is calculated by square root calculation means 22-1, 22-2, and 22-2, respectively. ....

22-n and proportional to the generated steam flow rate of each boiler. f2. ... + fN is obtained.

These signals f++f2. ... r fN is introduced into the adding means 23 to calculate a signal f proportional to the total flow rate, and this signal f is introduced into the adding means 24. In addition, the steam pressure detector 25 detects the pressure of the steam header common to each boiler,
This detection signal is introduced into the steam pressure adjusting means 26 and compared with the steam pressure target value signal Ps, and an adjustment calculation is performed so that the two match, thereby obtaining an adjustment calculation output signal fP. and,
This adjustment calculation white signal fr is introduced into the adding means 24, and is added and synthesized with Hiki Reiko f to obtain a substantial total flow 1iii tg No. f
Calculate T.

Next, this total flow rate signal fT is calculated using the optimum load distribution coefficient α1 for each boiler. α2. ..., load distribution coefficient means 27-1, 27-2, in which αN is set. ....

27-N, and as its output the distributed flow f of each boiler.
f1sV1. SV2. −． SVN is determined and used as a flow rate target value signal for each boiler B I + 82, . . .・・・
・, input to 28-H. (Here, αl+α2+,・
..., +αN-1, and the idle boiler αl-0. ) and this steam flow rate control device 28-1.28-2.・・・
. , 28-N, each output signal Mv1. MV2, ・
, MVN for each boiler 29-1.29-2. ..., 2
9-N as a fuel command signal, each boiler 29-1, 29-2. ..., 29-N, the steam flow rate target value signal sv1. sv2. ..., S.V.
It is controlled so that it becomes N.

By the way, each of the above-mentioned steam flow rate control devices 2g-1゜28-
2. ..., 2g-N (here, the steam flow rate control device 28-1 will be illustrated and explained) includes a steam flow rate adjustment means 28-IA, a signal restriction means 28-IB, and an addition means 2.
8-IC. That is, the basic signal is the steam flow target value signal SV1, and the steam flow If
The k adjustment means 28-IA performs adjustment calculations so that the steam flow rate target value signal Sv and the steam flow rate signal f1 match,
This adjustment calculation output signal is limited by the signal limiting means 28-IB and introduced into the adding means 28-IC, where it is added and synthesized with the steam flow rate target value signal Sv1 to generate the boiler combustion command signal MV.
is given to the boiler (Bt) 29-1 for control.

However, this type of conventional boiler steam flow rate control device has various problems as follows.

(a) Steam flow rate adjustment means (28-IA).

28-2A, ..., 28-NA) are PI or PID control systems with one degree of freedom, it is not possible to simultaneously optimize both the steam flow rate target value tracking characteristics and the disturbance suppression characteristics, resulting in poor controllability. is very bad.

(b) Steam flow rate target value signal Sv1 and steam flow rate adjustment means 2
In combination with 8-IA, the steam flow rate target value signal S
When V1 is changed, the boiler combustion command signal Mv1, which is the operation output signal, contains a change in the steam flow rate control device j5Sv1 and the control output signal from the steam flow rate adjustment means 2g-IA. The gain with respect to the change in the value signal Sv1 is doubled and becomes oscillatory.

(c) The unit calorific value of the fuel changes due to the use of low-grade fuel, and the fuel flow rate detection error.

Due to changes in boiler efficiency due to movement of boiler operating point, etc.
Boiler gain characteristics change and controllability deteriorates.

Note that the above-mentioned problems occur not only in the boiler steam flow rate control device but also in other process control devices such as the heating furnace total heat amount control device.

(Problems to be Solved by the Invention) As described above, in the past, there was a problem in that stable and high controllability could not always be maintained. .

An object of the present invention is to provide a highly reliable process control device that can always maintain stable and high controllability.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the first invention includes a process amount detection means for detecting a process amount from a controlled object, and a process amount target value signal. The process amount setting means to be set, the process amount from the process amount detection means, and the target value signal from the process amount setting means are input, and an adjustment calculation is performed so that the deviation between the two becomes zero, and an adjustment calculation output signal is obtained. A speed-type two-degree-of-freedom adjustment means for outputting, and a position-type/velocity-type signal conversion means for manually inputting a position-type signal, which is a target value signal from the process amount setting means, and converting the change into a speed-type signal and outputting it. and subtracting means for subtracting the output signal of the position/velocity signal conversion means from the adjustment calculation output signal of the velocity type-2 degrees of freedom adjusting means, and converting the speed type signal, which is the output signal from the subtraction means, into a position type signal. The speed type/position type signal conversion means converts and outputs the output signal from the speed type/position type signal conversion means and the target value signal from the process amount setting means are added and synthesized to generate the manipulated output signal of the controlled object. Further, in the second invention, in addition to each of the above-mentioned means, the speed is determined based on the ratio of the operation output signal from the addition means and the target value signal from the process amount setting means. and gain modification means for modifying the gain of the change in the adjustment calculation output signal from the two-degree-of-freedom adjustment means.

(Function) Therefore, in the present invention, by using the process ff1fi node means as a two-degree-of-freedom PI or PID adjusting means, it is possible to simultaneously optimize both the process quantity target value follow-up characteristic and the disturbance suppression characteristic, and the speed By subtracting the change in the target value signal from the speed type adjustment calculation output signal of the two-degree-of-freedom adjustment means, it is possible to prevent the target value signal from becoming oscillatory when changing, and furthermore, the operation output signal By correcting the gain corresponding to the change in the adjustment calculation output signal from the speed type 2 degrees of freedom adjusting means based on the ratio between the speed type 2 and the target value signal, the speed type 2 Optimum controllability can always be obtained by automatically modifying the gain of the degree of freedom adjusting means. This makes it possible to maintain stable and optimal control characteristics at all times.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example when the present invention is applied to a boiler steam flow rate control device.

In FIG. 1, a boiler 1 to be controlled is supplied with fuel and air from a fuel supply source and an air supply source (not shown), and the fuel is combusted together with the air, and the heat is used to heat water, which is a fluid to be heated. evaporates to produce steam,
This steam is co-supplied to the consumer side.

On the other hand, the flow rate of steam, which is a process amount generated from the boiler 1, is detected by a steam flow rate detector 2, which is a process amount setting means, and this detected signal is linearized by a square root operator stage 3,
The steam flow rate signal f is manually inputted to the speed type two degrees of freedom adjusting means 4. Further, a steam flow rate target value signal 5Vn (suffix n
indicates the current value by sampling calculation, and n-1 indicates the previous previous value), and inputs this to the speed type two degrees of freedom adjusting means 4 as a target value signal. Furthermore, speed type 2
The degree of freedom adjusting means 4 compares the steam flow rate signal f from the steam flow rate detector 2 and the steam flow rate target value signal SVn from the steam flow rate setting means 5, and performs adjustment calculations so that the deviation between the two becomes zero. This is performed to obtain an adjustment calculation output signal ΔCn, which is manually input to the subtraction means 6.

On the other hand, the steam flow rate target value signal S from the steam flow rate setting means 5
Vn is input to the position/velocity signal converting means 7, the change amount ΔSVn-5Vn-SVn-1 is obtained, this is converted to a velocity signal, and the signal is input to the subtracting means 6. Further, in the subtraction means 6, the speed type adjustment calculation output signal ΔCn of the speed type two degree of freedom adjustment means 4 is calculated from the position type/velocity type signal conversion means 7.
The output signal (ΔC
n-Δ5Vn) is input to the velocity/position signal converting means 8 and converted into a position signal. Furthermore, the output signal m V Q from the velocity type/position type signal converting means 8 is inputted to the signal limiting means 9 to provide a limit limit for the adjustment signal, and this is manually inputted to the adding means ][ ]. Furthermore, the steam flow rate target value signal SVn from the steam flow rate setting means 5 is input to the adding means 10, and this and the output signal from the signal limiting means 9 are added and synthesized to obtain a manipulation output signal M V n. Boiler 1
By giving the fuel command signal to the boiler 1 as a fuel command signal, the flow rate of steam generated by the boiler 1 is controlled.

In the boiler steam flow rate control device configured as described above, the steam flow rate adjustment means is configured as a conventional one-degree-of-freedom PI or PID.
By changing the adjustment means to a two-degree-of-freedom PI or PID adjustment means 4, it is possible to simultaneously optimize both the steam flow rate target value follow-up characteristic and the disturbance suppression characteristic. Further, the steam flow rate target value signal SVn is inputted to the position type/velocity type signal conversion means 7, and its change Δ5Vn=S Vn −
S vn-7 is obtained, converted to a speed type signal, manually inputted to the subtraction means 6, and subtracted from the speed type adjustment calculation output signal ΔCn of the speed type two degrees of freedom adjustment means 4, thereby obtaining the steam flow rate target value. It is possible to prevent the signal SVn from becoming oscillatory when changing. That is, considering the overall signal change in terms of the manipulated output signal MVn, this effect is expressed as mvn-mvn-1+ΔCn-ΔSVn"mvn
−1+ΔCn −8Vn +SVn−IMVn =SV
n +mvn ”” m V n-1+ΔCn+5Vn-1...(1
). Here, m v n-1 is the previous adjustment output signal, and ΔCn is the current adjustment output signal, 5Vn-.

is the previous steam flow rate target value signal.

Therefore, the steam flow rate target value signal is s v n-', while S
When the voltage changes to Vn, only the current change ΔCn of the adjustment output signal is reflected in the operation output signal MVn, as shown in equation (1). Hence, steam.

When the flow rate target value signal changes from 5Vn-+ to SVn, the influence on the manipulated output signal MVn is different from S as in the conventional case.
The direct change on the Vn side and the change on the flow rate adjustment side no longer overlap, and together with the effect of having two degrees of freedom in the flow rate adjustment operation, controllability is greatly improved.

'' As described above, the boiler steam flow rate control device of this embodiment provides the following effects.

(a) As a steam flow rate adjustment means, conventional one degree of freedom PI
Or 2 degrees of freedom PI or PI instead of PID adjustment means
By applying the D adjustment means 4, it is possible to simultaneously optimize both the steam flow rate target value follow-up characteristic and the disturbance suppression characteristic.

(b) By subtracting the change in the steam flow rate target value signal SVn from Cn to the speed type adjustment calculation output signal, the steam flow rate target It is possible to eliminate double superimposition of changes in the operation output signal M V n when the value signal SVn changes, and to prevent oscillations when the steam flow rate target value signal SVn changes.

As a result of the above, it is possible to improve the sophistication of the boiler steam flow rate control device, and this sophistication makes it possible to supply stable and high-quality steam, and also contributes to energy savings through optimal load distribution, etc. It becomes possible.

Furthermore, it is predicted that the use of low-grade fuels such as pulverized coal and by-product fuels will increase in the future due to the limited availability of petroleum resources and rising energy costs. By doing so, controllability can be improved, and it can be expected to greatly contribute to the development of industry.

Next, other embodiments of the present invention will be described.

FIG. 2 is a block diagram showing another configuration example when the present invention is applied to a boiler steam flow rate control device, and the same parts as in FIG. Now, I will only discuss the different parts.

That is, this embodiment includes gain correction means consisting of gain correction coefficient calculation means 11 and multiplication means 12 in addition to that shown in FIG. Based on the ratio with the steam flow rate target value signal SVn, the gain corresponding to the change in the adjustment calculation output signal ΔCn from the speed type two-degree-of-freedom adjustment means 4 is corrected. The gain correction coefficient calculating means 11 includes the dividing means 11
a, delay means 11b, and filter means 11C. That is, the current value MV n of the operation output signal and the current value SV of the steam flow rate target value signal are stored in the dividing means 11a.
n, divide the former by the latter to calculate the current value kn of the gain correction coefficient, input this to the delay means 11b, and
The gain correction coefficient k n-1 for the previous time is extracted by sending only the previous time. Then, this is inputted to the filter means 11c and smoothed, and a gain correction section B that removes transient fluctuation components,
kn-1 is obtained and inputted into the multiplication means 12 to obtain the velocity form 2.
By multiplying the :Am calculation output signal ΔCn from the degree of freedom adjustment means 4, the gain of the speed type 2 degree of freedom adjustment means 4 is automatically corrected in response to the change in the gain characteristics of the boiler 1. .

In the boiler steam flow rate control device configured as described above, as in the embodiment shown in FIG. By setting it as 4,
Both the steam flow rate target value tracking characteristic and the disturbance suppression characteristic can be simultaneously optimized. In addition, the steam flow rate target value signal SVn is input to the position type/velocity type signal converting means 7, and its change ΔSVn = SVn-3Vn- is obtained, which is converted to a speed type signal and inputted to the subtracting means 6. and speed type 2
By subtracting it from the speed type adjustment calculation output signal ΔCn of the degree of freedom adjustment means 4, it is possible to prevent the steam flow rate target value signal SVn from becoming oscillatory when changing.

Furthermore, in FIG. 2, the influence of the change in the gain characteristics of the boiler 1 is determined by the steam flow rate target value signal SVn and the operation output signal M V
It appears as a difference from n. Also, since only the previous coefficient can be used to correct the gain of the current adjustment calculation output signal ΔCn, the previous gain correction coefficient k n
-1 is obtained by the dividing means 11a.

kn-1 - MVn-1/S vn-, - (2) To remove ° transient fluctuations of the gain modification coefficient k n-1,
Average gain correction coefficient k n through filter means 11C
-1 is obtained, and this is multiplied by the adjustment calculation output signal ΔCn from the velocity type two-degree-of-freedom adjustment means 4 by the multiplication means 12 to perform gain correction. As a result, the manipulated output signal M V
n is m V n ” m V n-1+ k n-, XΔC
n-Δ5Vn-m v n-1+ k n-I XΔC
n -5Vn+5 V Q-1 MVn =mvn +s Vn -m V n-10k n-l XΔC1+5Vn-t
...(3), and in response to the change in the gain characteristics of boiler 1, the speed type 2
The gain of the adjustment calculation output signal ΔCn from the degree of freedom adjustment means 4 is automatically corrected, and stable and highly accurate control can be realized at all times.

As described above, the boiler steam flow rate control device of this embodiment not only provides the same effect as the case shown in FIG. By correcting the gain corresponding to the change in the d number ΔCn from the speed type two-degree-of-freedom adjustment means 4 based on the ratio of By automatically modifying the gain of the speed-type two-degree-of-freedom adjusting means 4, it becomes possible to always obtain optimal controllability.

Incidentally, the gain correction coefficient calculation means 11 is not limited to the above-mentioned configuration, but may include, for example, a delay means, a division means, and a filter means, and the current value MVn of the manipulated output signal is taken once through the delay means. Alternatively, the signal may be divided by a signal obtained by taking the current value SVn of the steam flow rate target value signal once through the delay means, and then input to the filter means to obtain the smoothed result as the gain correction coefficient. good.

Further, in each of the above embodiments, the present invention is applied to a boiler steam flow rate control device, but the present invention is not limited to this and can be similarly applied to other process control devices such as a heating furnace total heat amount control device. be.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to provide an extremely reliable process control device that can always maintain stable and high controllability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention applied to a boiler steam flow rate control device, and FIG. 2 is a block diagram showing another embodiment of the present invention applied to a boiler steam flow rate control device. , FIG. 3 is a block diagram showing a configuration example when a conventional boiler steam flow rate control device is applied to a load distribution control system for multiple boilers. DESCRIPTION OF SYMBOLS 1...Boiler, 2...Steam flow rate detector, 3...Square root calculation means, 4...Speed type 2 degrees of freedom adjusting means, 5...
- Steam flow rate setting means, 6... Subtraction means, 7... Position type/speed type signal converting means, 8... Speed type/position type signal converting means, 9... Signal limiting means, 10. ... addition means, 11... gain correction coefficient calculation means, lla... division means, llb... delay means, llc... filter means, 12... multiplication means. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (2)

[Claims] (1) A process quantity detection means for detecting a process quantity from a controlled object; a process quantity setting means for setting a target value signal for the process quantity; and a process quantity from the process quantity detection means and a process quantity setting means. a speed-type two-degree-of-freedom adjustment means that inputs a target value signal, performs adjustment calculation so that the deviation between the two becomes zero, and outputs an adjustment calculation output signal; and a target value signal from the process amount setting means. a position/velocity signal converting means that inputs a positional signal, converts the change thereof into a velocity signal, and outputs the same; subtracting means for subtracting the output signal of the signal converting means; speed type/position type signal converting means for converting the speed type signal, which is the output signal from the subtracting means, into a position type signal and outputting the same; an addition means for adding and synthesizing the output signal from the shape signal conversion means and the target value signal from the process amount setting means and outputting an operation output signal of a controlled object; . (2) process quantity detection means for detecting a process quantity from a controlled object; process quantity setting means for setting a target value signal for the process quantity; a speed-type two-degree-of-freedom adjustment means that inputs a target value signal, performs adjustment calculation so that the deviation between the two becomes zero, and outputs an adjustment calculation output signal; and a target value signal from the process amount setting means. a position/velocity signal converting means that inputs a positional signal, converts the change thereof into a velocity signal, and outputs the same; subtracting means for subtracting the output signal of the signal converting means; speed type/position type signal converting means for converting the speed type signal, which is the output signal from the subtracting means, into a position type signal and outputting the same; addition means for adding and synthesizing the output signal from the shape signal conversion means and the target value signal from the process amount setting means and outputting a manipulated output signal of a controlled object; Based on the ratio with the target value signal from the setting means, the speed type 2
A process control device comprising: gain modification means for modifying the gain of a change in the adjustment calculation output signal from the degree of freedom adjustment means;