JPH0737122Y2 - Plant control equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a plant control device for controlling a process amount having a large delay such as a steam temperature of a boiler.

[Prior Art] For example, steam temperature control of a boiler is performed by controlling a fuel flow rate. The conventional example of this plant control device is the third
In the figure, 1 is a steam temperature detector which is a process amount detector, 2 is a steam temperature setter which is a process amount setter,
3 is the detected steam temperature signal T and the set steam temperature signal T ₀
Of the deviation signal .DELTA.T, 4 is a proportional-plus-integral controller for outputting a correction signal V obtained by integrating the deviation signal .DELTA.T obtained by the subtractor 3, and 5 is a fuel F which is a fluid. The control valve is provided in the pipe line 6 for supplying to the burner, and the opening degree is adjusted in proportion to the signal obtained by being integrated by the proportional-plus-integral adjuster 4.

In the above plant control device, the deviation signal ΔT is T−T _{0 in the} subtractor 3 based on the steam temperature signal T detected by the steam temperature detector 1 and the steam temperature signal T ₀ set by the steam temperature setting device 2. The deviation signal ΔT is given to the proportional-plus-integral adjuster 4 and integrated, and the correction signal V proportional to the signal obtained by the integration is given from the proportional-plus-integral adjuster 4 to the control valve 5 as a command signal. The opening of the control valve 5 is adjusted in proportion to the magnitude of the correction signal V.

[Problems to be Solved by the Invention] In the above plant control device, as described above, the steam temperature detector 1 detects the steam temperature as the process amount, and the opening degree of the control valve 5 is adjusted based on the result to the burner. The flow rate of the supplied fuel F is increased / decreased and controlled according to the set steam temperature. However, even if such control is performed, the steam temperature in the steam pipe does not immediately reach the set value and stabilizes at the set value. There is a large time lag before the operation.

That is, in the control of the process amount with such a large delay, for example, the steam temperature (process amount) of the boiler is higher than the steam temperature set with the passage of time as shown by the solid line in the time zone I of FIG. As the temperature deviation decreases and the temperature deviation increases, the correction signal V given to the control valve 5 increases and the opening of the control valve 5 increases, as shown by the solid line in FIG.

Therefore, the fuel F supplied to the burner increases, and the steam temperature of the boiler gradually rises as shown by the solid line in time zone II of FIG. 4, while the steam temperature rises as shown by the solid line of FIG. Thus, the control valve 5 is gradually throttled. Thus, at time t ₁ , the steam temperature rises to the steam temperature set as shown in FIG. At this time, the opening degree of the control valve 5 is larger than the opening degree corresponding to the set steam temperature as shown by the solid line in FIG. Even if the valve 5 is further throttled, the steam temperature of the boiler exceeds the set value and further rises as shown by the solid line in the time zone III of FIG. 4, and in some cases, it may exceed the upper limit value and give an alarm. .

Further, for example, when the steam temperature of the boiler rises with time and becomes larger than the set steam temperature as shown by the solid line in the time zone I of FIG. 6, the correction signal given to the control valve 5 is given. As shown in FIG. 7, V decreases and the opening degree of the control valve 5 decreases.

Therefore, the fuel F supplied to the burner decreases, and the steam temperature of the boiler gradually decreases as shown by the solid line in time zone II of FIG. 6, while the steam temperature of the boiler decreases as shown by the solid line of FIG. Thus, the control valve 5 is gradually opened. Thus, at time t ₁ , the steam temperature drops to the set temperature. At this time, the opening degree of the control valve 5 is smaller than the opening degree corresponding to the steam temperature set as shown by the solid line in FIG. 7 due to the time delay of the steam temperature decrease. Even if No. 5 is opened further, the steam temperature of the boiler exceeds the set value as shown by the solid line in time zone III in FIG. 6 and further falls, and in some cases, falls below the lower limit value, which may cause an alarm. is there.

In view of the above situation, the present invention provides that the deviation signal between the set steam temperature signal and the detected steam temperature signal remains large for a certain period of time, that is, the output from the proportional-plus-integral regulator becomes large to some extent. The purpose is to forcibly limit the correction signal applied to the control valve to reduce the time delay of the correction operation of the control valve.

[Means for Solving the Problem] The present invention is directed to a subtracter for obtaining a deviation signal between the detected process amount signal and a set process amount signal, and integrating the deviation signal from the subtractor. A proportional-plus-integral regulator that outputs the obtained signal, a function generator that outputs a signal corresponding to the deviation signal from the subtractor, and a detected process amount is lower or higher than a set process amount. When the time is short, the signal from the proportional-plus-integral regulator, which is lower than the signal from the function generator, is selected as the correction signal and is given to the control valve that controls the fluid flow rate, and the detected process amount is set. If the time is lower or higher than the process amount, the signal from the function generator, which is lower than the signal from the proportional-plus-integral regulator, is selected as the correction signal, and the upper limit signal limit is given to the control valve for controlling the fluid flow rate. vessel It is equipped with.

[Operation] The deviation between the detected process amount signal and the set process amount signal is given to the proportional-plus-integral regulator and the function generator, and the proportional-plus-integral regulator gives the integrated signal to the upper limit signal limiter, A signal corresponding to the deviation signal is given from the function generator to the upper limit signal limiter. Thus, the lower signal of the signals from the proportional-plus-integral regulator and the function generator is applied from the upper limit signal limiter to the control valve as a correction signal. Therefore, when the detected process amount is shorter or longer than the set process amount, the signal from the proportional-plus-integral regulator is lower than the signal from the function generator, so the control valve Is opened or narrowed by the correction signal from the proportional-plus-integral regulator, but if the detected process amount is longer or lower than the set process amount, the signal from the proportional-plus-integral regulator is a function. The signal from the function generator is selected in the upper limit signal limiter because it is larger than the signal from the generator and the control valve is throttled or opened by the correction signal from the function generator. Therefore, the control valve is forcibly throttled or opened further ahead of the opening corresponding to the deviation signal between the detected process amount signal and the set process amount signal. The excessive increase or decrease of the process amount that occurs when controlling the opening corresponding to
The fluctuation of the process amount stabilizes rapidly and does not deviate from the limit value.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which the same reference numerals as those in FIG. 3 represent the same parts.

Basically, in a plant controller having the same configuration as shown in FIG. 3, an upper limit signal limiter 7 is connected to the proportional-plus-integral adjuster 4, and the deviation signal ΔT obtained by the subtractor 3 is proportional-integral-adjusted. It can be applied to the function generator 8 as well as to the function generator 8. Further, a signal V'obtained by integrating the deviation signal .DELTA.T from the proportional-plus-integral adjuster 4 can be given to the upper limit signal limiter 7, and the function generator 8 outputs the signal V'to the upper limit signal limiter 7. As shown in Fig. 2, the signals F (x ₁ ), F corresponding to the deviation signals ΔT ₁ , ΔT ₂ ... ΔT _n
(X ₂ ) ... F (x _n ) can be given. Thus, for example, as shown in FIG. 2, the function generator 8 outputs a signal F (x) that is large when the deviation signal ΔT is large and a signal F that is output when the deviation signal ΔT is small.
A function that reduces (x) is input.

In the above plant control device, the deviation signal ΔT is T in the subtractor 3 based on the steam temperature signal T detected by the steam temperature detector 1 and the steam temperature signal T ₀ set by the steam temperature setting device 2.
The deviation signal ΔT obtained by −T ₀ is
And to the function generator 8.

The proportional-plus-integral adjuster 4 integrates the deviation signal ΔT and outputs the integrated signal V ′ to the upper limit signal limiter 7. Further, when the deviation signal ΔT given to the function generator 8 is ΔTn, the signal F (x _n ) from the function generator 8 is correspondingly generated.
Is output to the upper limit signal limiter 7.

When the absolute value of the deviation obtained by subtracting the steam temperature of the boiler from the set steam temperature increases with the passage of time, the signal V'output from the proportional-plus-integral controller 4 is the function generator. If the absolute value of the deviation becomes smaller as time passes, the signal V'becomes larger than the signal F (x). Adjustment of the proportional-plus-integral regulator 4 and the function generator 8 has been performed in advance by a test operation.

Therefore, when the set steam temperature is lower than the steam temperature of the boiler and the deviation thereof increases with the passage of time as indicated by the dotted line in the time zone I of FIG. Since the generated signal V ′ is smaller than the signal F (x _n ) output from the function generator 8, the signal V ′ from the proportional-plus-integral regulator 4 is selected by the upper limit signal limiter 7 and is corrected in the control valve 5. Given as signal V. Therefore, when the deviation signal ΔT gradually increases, the correction signal V increases with time as shown by the dotted line in FIG. 5, so that the opening of the control valve 5 increases and passes through the control valve 5. The flow rate of the fuel F supplied to the burner increases, and the steam temperature of the boiler begins to rise as shown by the dotted line in time zone II in FIG. 4, and the deviation between the set steam temperature and the detected steam temperature is Begins to decrease.

As in the time zone II, when the deviation between the set steam temperature and the detected steam temperature starts to decrease, the signal V'from the proportional-plus-integral controller 4 is the signal F'from the function generator 8.
Since the proportional-plus-integral controller 4 and the function generator 8 are adjusted to be larger than (x), the signal from the proportional-plus-integral controller 4 is limited by the upper limiter 7, and the control valve 5 generates the function. signal from the vessel _{8 F (x 1), F} (x 2) ... is corrected signals V _1,
V ₂ ... Is given to the control valve 5, and as shown by the dotted line in FIG. 5, the control valve 5 is more than the opening degree of the control valve 5 corresponding to the deviation between the set steam temperature and the detected steam temperature. It will be narrowed down in advance. Therefore, the steam temperature gradually rises to approach the set temperature as indicated by the dotted lines in time zones II and III in FIG. 4, and the opening of the control valve 5 gradually approaches a constant and stable opening. Become.

Further, when the set steam temperature is higher than the detected steam temperature and the deviation thereof increases with the passage of time as indicated by the dotted line in the time zone I in FIG. 6, the output from the proportional-plus-integral controller 4 The selected signal V'is selected by the upper limit signal limiter 7 and given to the control valve 5, as shown by the dotted line in FIG.
Since the correction signal V becomes smaller with time, the opening of the control valve 5 is narrowed and the fuel F supplied to the burner through the control valve 5 is reduced.
, The steam temperature begins to decrease as shown in time zone II in FIG. 6, and the deviation between the set steam temperature and the detected steam temperature begins to decrease. Therefore, in this time zone II, the signal V'from the proportional-plus-integral regulator 4 is limited by the upper limit signal limiter 7 for the reason described above, and the control valve 5 receives the signal F (x ₁ ) from the function generator 8. , F (x ₂ ) ... Is given to the control valve 5 as correction signals V ₁ , V ₂ ... And the control valve 5 simply indicates the set steam temperature and the detected steam temperature as shown by the dotted line in FIG. The opening is larger than the opening of the control valve 5 corresponding to the deviation. Therefore, the steam temperature will be
As indicated by the dotted line in III, the temperature gradually decreases to approach the set temperature, and the opening of the control valve 5 also approaches the constant and stable opening via the path shown by the dotted line in FIG.

As described above, the steam temperature is rapidly set to the set steam temperature by squeezing or opening the control valve 5 in advance in anticipation of the time when the deviation between the detected steam temperature and the set steam temperature begins to decrease. It is possible to bring them closer to each other, and it is possible to perform stable boiler operation.

In the embodiment of the present invention, the control valve is controlled by the correction signal from the function generator when the deviation signal between the detected process amount signal and the set process amount signal is started to decrease. , The timing to start the control of the control valve by the correction signal from the function generator can be appropriately determined according to the characteristics of the plant, can be applied to plants other than the boiler, and within the range not departing from the gist of the present invention It goes without saying that various changes can be made in.

[Advantages of Device] As described above, according to the plant control device of the present invention, it is possible to quickly reduce the fluctuation of the process amount by suppressing the recoil of the correction operation in advance.
An excellent effect that the operation of the plant can be easily and quickly stabilized can be exhibited.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the plant controller of the present invention, and FIG. 2 is a graph showing the relationship between the deviation signal and the correction signal of the function generator used in the plant controller of the present invention.
FIG. 3 is a block diagram of an example of a conventional plant control device,
FIG. 4 is a graph showing an example of the relationship between steam temperature and time in the present invention and the conventional plant control device, FIG. 5 is a graph showing an example of relationship between the correction signal and time for the control valve, and FIG. FIG. 7 is a graph showing another example of the relationship between steam temperature and time in the devised and conventional plant control apparatuses, and FIG. 7 is a graph showing another example of relationship between the correction signal and time for the control valve. In the figure, 1 is a steam temperature detector (process amount detector), 2 is a steam temperature setting device (process amount setting device), 3 is a subtractor, 4 is a proportional-plus-integral controller, 5 is a control valve, 6 is a conduit. , 7 is an upper limit signal limiter, 8 is a function generator, F is fuel, T is a detected steam temperature signal (a detected process amount signal), T ₀ is a set steam temperature signal (a set process amount). Signal), ΔT
Is a deviation signal, V, V ₁ , V ₂ ... V _n is a modified signal, V'is a signal obtained by integration, F (x), F (x ₁ ), F (x ₂ ) ... F (x _n )
Indicates the signal output from the function generator.

Claims (1)

[Scope of utility model registration request] 1. A subtractor for obtaining a deviation signal between the detected process amount signal and a set process amount signal, and a proportional for outputting a signal obtained by integrating the deviation signal from the subtractor. An integral regulator, a function generator that outputs a signal corresponding to the deviation signal from the subtractor, and a function when the detected process amount is shorter or shorter than the set process amount. The signal from the proportional-integral regulator, which is lower than the signal from the generator, is selected as the correction signal and is given to the control valve that controls the flow rate of the fluid, and the detected process amount is lower or higher than the set process amount. When the time is long, the upper limit signal limiter is provided, which selects the signal from the function generator lower than the signal from the proportional-plus-integral regulator as the correction signal and gives it to the control valve for controlling the fluid flow rate. Tosu The plant control system.