JPS6172314A - Controller for average flow rate liquid level - Google Patents

Abstract

PURPOSE:To avoid the over-correction of a flow rate due to an integrating action by delivering an adverse hysteresis signal when a control deviation signal exceeds a range of deviation corresponding to a blind sector area and using the adverse hysteresis signal to control the application of a control signal to an operating terminal. CONSTITUTION:A control deviation signal B is sent to an adverse hysteresis signal producing part 19 as well as to a blind sector area forming part 143. The signals of low levels are delivered as long as the signal B is kept within a range of deviation corresponding to a blind sector area and then set at high levels when the signal B exceeds said range of deviation and is set at >=H1 to show the adverse hysteresis characteristics. This signal of a high level serves as an ON control signal of an adverse hysteresis adding circuit 16. As a result, a flow rate control valve is controlled. Then the flow rate is controlled by a control signal D produced at a PI control arithmetic part 15. Thus the level of the signal B is lowered gradually. When the signal B is set at <=H2, an adverse hysteresis signal F is delivered. Thus the circuit 16 is turned off.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] ∆ The present invention utilizes the driftwood accumulation effect of, for example, a tank or tank (hereinafter collectively referred to as a tank) to reduce the flow rate from the tank to the tongue. The present invention relates to an improvement in an equalizing liquid level control device for smoothing the /I movement of the outflow flow rate.

[Technical background of the invention and its problems]

In general, continuous processes such as petroleum refining and petrochemical processes have various steps such as heat, distillation, compression, reaction, cooling, absorption, separation, and refining connected in series or parallel. A buffer tank is installed to absorb the four changes in the amount of light. By the way, the stability of continuous process operation depends on the quality of the control of the liquid level control using the tank. It is no exaggeration to say that.In other words, if the restraint control is not performed properly, flow rate fluctuations will occur, and the control of each downstream process will be affected in a chain reaction, resulting in disrupted and unstable operation. As a result, there are problems such as a decline in product quality and an increase in power consumption.In particular, in continuous processes such as oil refining and petrochemicals, it is difficult to control the balance surface using metal tanks. It is said that if you can control the limits, you can control the stable operation of the process.In this way, the retained liquid level control is a very important control, but with conventional technology, it is possible to control the stable operation of the process. However, the limits of restraint have not been reached.

The conventional device will be explained in detail below.

FIG. 3 shows a single-loop control type equalizing liquid level control device, in which fluid such as raw materials or intermediate products is supplied from a previous process, for example, through the entire inflow pipe 1 to the tongue 2. The liquid level in tank 2 is detected by liquid level detector 3. The next liquid level detection signal detected by this liquid level detector 3 is P
I (P: ratio 14 LI: integral) is introduced into the controller 4, where it is compared with the set value Sv and PI calculation with insensitive area is performed to obtain an operation output signal, and this signal controls the opening degree of the flow rate control valve 5. I of the fluid to be adjusted and sent from tongue 2 to the next process
It controls tit. 6 is an outflow pipe.

Next, FIG. 4 shows an equal flow liquid level control device having a cascade control system for controlling the liquid level and the flow rate. In this device, a specific output signal obtained from a liquid level controller (o-ra) 4 is given to a total flow rate controller 7 as a flow rate set value signal, and a flow rate of an outflow pipe σ is detected by a flow rate detector 8 to generate a detection signal. 1
c After linearization by the square root calculation unit 9, the flow rate controller)
Introduced as an o-ra 7 heb a access signal.

In this flow rate controller 7, a square root calculating section 9
The process signal from the liquid level controller 4 is compared with the set value signal from the liquid level controller 4, and a PI adjustment calculation with a total dead band area is performed to obtain an operation output signal.
It controls the ait of KK which adjusts the relationship and sends it to the next process.

By the way, the purpose of a buffer tank interposed between unit operations in a continuous process is to absorb and concentrate the fLt4 movement. However, when the inflow flow rate increases, the controller 4.7 of the PI calculation with a dead zone area of the above device functions by controlling the chest tip in the dead zone area and turning off the PI outside the dead zone area, but it is particularly difficult to operate during construction work. In this case, an overcorrection of the flow rate occurs because the opening operation continues from the time when the deviation between the process and the set value goes outside the dead band area until it enters the dead band area. As you move into the area, repeat this series of actions.

As a result, the flow equalization time is shortened, and the difference between the previous restricted flow rate and the subsequent equalized R and flow rate becomes large, and the flow suppression effect is halved.

[Purpose of the invention]

The present invention has been made with attention to the above-mentioned points, and it is possible to prevent over-correction of the flow rate due to integral operation and make the most of the flow suppression effect, thereby eliminating unnecessary disturbances to the plant. Our goal is to provide a complete equalization liquid level control device that achieves stable operation.

[Summary of the invention]

In addition to the PI calculation means with a dead band area, the present invention generates a reverse hysteresis on/off signal when a difference of 1 between the liquid level detection signal and skin level setting II signal goes outside the dead band area. A reverse hysteresis signal generating means and an adjusting operation are executed when an ON signal is output from the reverse hysteresis signal generating means.

This liquid level control device has output control means for forcibly holding all the operation output signals when an off signal is output, and prevents over-correction of the flow rate during integral operation.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In the figure, 11 is a tank including a tank having a buffer function, and i pieces of raw materials or intermediate products are introduced into this tank 11 from the previous process via an inlet pipe 12. This tank 11 is provided with a liquid level detector 13, which detects the liquid level of the tank 11. As the liquid level detector 13, a differential pressure detector may be used, or a capacitance type level meter may be used if the fluid itself has a di ratio specific to it. The entire liquid level may be detected using a float-type liquid level detector. The liquid level detection signal A detected by the liquid level detector 13VC is sent to the dead zone type means 14.

This dead zone area forming means 14 compares a liquid level detection signal proportional to the liquid level from the liquid level detector 13 with a liquid level detection signal set by a fixed foot type or variable type liquid level setting unit 14. A deviation calculation element 142 that calculates a control deviation signal o2, and a control deviation signal output from this deviation calculation element 142 are outside the dead zone region up to a predetermined positive and negative monthly difference range centered on zero, and exceed the deviation range. and a dead band region forming unit 143 that outputs an effective difference signal C proportional to the deviation from there.
It has the following.

Reference numeral 15 denotes a speed-type PI adjustment calculation section which takes in the effective@difference signal C and performs speed-type PI adjustment calculation to obtain a speed-type adjustment signal 2'. i via velocity type-position shadow signal converter 1
7.

This signal conversion f! iJ, 17 converts the speed type control signal 27 into a position type signal and obtains the operation output signal HO7, which is sent to the flow control valve 181 to adjust the opening degree of this flow rate control valve 18, and is used in the primary process. This is to adjust the flow rate to.

Furthermore, this device has an inverse 7 sterility signal generator 19 to which a control deviation signal port from the deviation calculation element 142 is input. This reverse hysteresis signal generator 19 has a reverse hysteresis characteristic of a predetermined width in a portion where the positive and negative deviations exceed the dead zone region around zero, and has a predetermined two-way signal necessary for on/off control of the switch. A reverse hysteresis signal 7 having a value level is generated and sent to the reverse hysteresis circuit 16. This circuit 16 with reverse hysteresis is turned on when the reverse hysteresis signal is turned on.

The speed type adjustment signal 2 is sent to the signal converter 17 to execute the adjustment calculation, and when it is off, the speed type adjustment signal 2 is not sent to the signal converter 12, but the operation output signal H is forced in the signal converter 17. It has the function of holding the

Next, we will discuss the operation of the device configured as described above.
The explanation will be made with reference to FIG. 2 and FIG. 8g2. In addition, FIG. , the change to the inverse hysteresis signal which is the output of the section 19, (cl shows the change in the equivalent control deviation signal when the inverse 1-flix function is added to the conventional control method.0 First, (ii) The difference calculation element 142 compares the liquid level detection signal A and the liquid level setting signal to obtain a control deviation signal which is the (2) distortion of these two signals and supplies it to the dead band region forming section 143. As shown in FIG. 2 (al), the dead zone area form fJx, section 143 is such that even if the control deviation signal port gradually increases, the output remains zero until a predetermined positive/negative deviation range predetermined as the center of 4. When the dead zone area is expressed as a dead zone area, and when it exceeds a predetermined monthly difference range and becomes H1 or higher, an effective deviation signal C is obtained which is a ratio of partial strain IVC from Hl.Then, this effective deviation signal C is expressed as a speed type. The PI is sent to the J section IE 15, where the speed type I PI adjustment calculation is performed to obtain the speed type adjustment signal 2.

It is sent to the velocity type/position shadow signal converting section 17 via the inverse hysteresis signal attached circuit 16, where the inverse hysteresis signal outputted from the inverse hysteresis signal generating section 19 is In response to the hysteresis signal, the introduction of the speed type adjustment signal 2 to the signal converting section 17 is controlled.

That is, the control deviation signal port is sent not only to the dead band region forming section 143 but also to the reverse error signal generating section 19,
Here, in the signal output section 19, the control IJi difference signal port outputs, for example, a-level up to a predetermined deviation range corresponding to the above-mentioned dead zone region, and when the predetermined deviation range is exceeded, H, J
d, it exhibits a reverse hysteresis characteristic and becomes high level as shown in FIG. As a result, the adjustment signal 2 from the speed type PI adjustment calculation section 15 is introduced into the signal conversion section 17, and the adjustment operation of the flow rate adjustment valve 18 is effected. This adjustment operation is performed when the control deviation signal port is H.
Even if tk is exceeded or VcH is exceeded, the reverse hysteresis will continue to be effective due to the high level of the reverse hysteresis signal. After that, when the flow rate is adjusted by the adjustment signal 2 from the PIyU @ calculation unit 15 and the control deviation signal port gradually decreases, the bottom g19 of the reverse hysteresis signal is different from when the control deviation signal port rises and is ! The reverse hysteresis signal adding circuit 16 is turned off because it outputs the reverse hysteresis signal which becomes low level when the voltage is below.

Therefore, the adjustment signal 2 of the speed type PI adjustment calculation unit 15 is no longer seen in the signal conversion unit 17, and the operation output signal is held here and the control is shifted to the suppression control as shown in FIG. 2 (cl). .

The above explanation was about the positive side deviation, but as shown in Figure 2, even for the negative side deviation, the reverse hysteresis operation when the negative side slope, L, vc is reached is the same as the operation for the positive side deviation. It is.

Therefore, in the embodiment device described above, as is clear from the column equivalently replaced with the operation of the control 1Jii difference signal shown in FIG. 2(C), after the control deviation signal port becomes H8 or higher or When turning in the convergence direction, the reverse upward 1 flick function locks the adjustment rM operation early and shifts to suppression control to prevent the integral operation from going too far.

Note that the T-invention device is not limited to the above-mentioned I column. That is, although the above embodiment has been explained using a hardware configuration, each component 141 to 143% 15, 17, 19, etc. can be processed in a software manner using a micro combinator.

In addition, the PI adjustment/control unit 15 performs a speed-type PI adjustment operation and converts it into a position shadow signal by the subsequent signal conversion unit 11VfC, but it is possible to reach the IC bottom in the same way by processing only one position-type signal. . moreover.

Although the above-mentioned Actual Control-J was applied to the control of the miscarriage of 6n of fluid from the tank 1, VC can be similarly applied to the control of the inflow of fluid. In addition, a reverse hysteresis signal was created using the control (6) signal port.

Dead band region form 1'l! ! It may also be created using the output of r143. Other 1 The present invention can be implemented with various modifications without departing from the gist thereof.

〔Effect of the invention〕

As detailed above, according to the present invention, upon receiving a control deviation signal, the deviation is set as a dead band region of zero output up to a predetermined deviation range with the center of 47, and flow rate adjustment control is performed using all terms of the predetermined adjustment signal. In this case, when the control deviation signal or the effective deviation signal is used to deviate from the predetermined deviation range, a reverse hysteresis signal is stolen and this signal is used to fully control the introduction of the adjustment signal to the operating end side. Using the reverse hysteresis signal, it is possible to stop the introduction of the adjustment signal to the operating end before the control deviation signal returns to the predetermined deviation range, and it is possible to completely prevent over-correction of the flow rate due to the product X operation.

This makes it possible to make maximum use of the flow suppression effect of the tank, thereby reducing unnecessary disturbances to the plant and ensuring stable operation of the plant. As a result, chain disturbances can be minimized in multi-process plants, and a level-level control device can be provided that contributes to energy savings and higher product quality.

[Brief explanation of the drawing]

Fig. 1 shows the device of the present invention. The configuration diagram shown. FIG. 2 is a diagram showing the relationship between the reverse hysteresis function and control deviation in the device of the present invention, and FIGS. 3 and 4 are configuration diagrams illustrating the conventional device, respectively. DESCRIPTION OF SYMBOLS 11... Tank (driftwood accumulation container), 13... Liquid level detector, 14... Dead zone area forming means, 142...
Deviation calculation element, 143... Dead zone area shape g section. 15... PI adjustment calculation unit, 16... Rabbit circuit with reverse hysteresis signal, 18... T:! 1. t14 seasonal valve, 19
...The bottom of the reverse hysteresis signal. Applicant's agent Patent attorney Suzu Ushiki Hiko 3 Figure 4

Claims (7)

[Claims] (1) In an equal flow liquid level control device using a fluid storage container, an effective deviation signal with a dead band region is derived from a control deviation signal that is the deviation between the fluid level detection signal in the fluid storage container and the liquid level set value signal. dead band area forming means for calculating the dead band area; adjustment calculation means for calculating an adjustment signal by adjusting the effective deviation signal obtained by this means; a reverse hysteresis signal generating means for outputting a reverse hysteresis signal having a reverse hysteresis characteristic when the voltage exceeds the limit; and controlling introduction of the adjustment signal to the operating end side using the reverse hysteresis signal obtained by the reverse hysteresis signal generating means. An equalizing liquid level control device comprising: an adjustment signal output control means for controlling the level of the liquid. (2) The dead zone area forming means includes a deviation calculation element that compares the fluid level detection signal and the liquid level set value signal to obtain a control deviation signal that is the deviation between these two signals, and a control deviation signal obtained by this deviation calculation element. When a control deviation signal is received, this control deviation signal forms a dead band region of zero output within a predetermined deviation range from zero, and when it exceeds the predetermined deviation range, an effective 2. The equalizing liquid level control device according to claim 1, further comprising a dead zone region forming section that outputs a deviation signal. (3) The liquid level setting value signal is set in advance and output from a variable liquid level setting section.
2. The equalizing liquid level control device according to any one of Items 1 and 2. (4) The dead zone region forming section forms a dead zone region in which the output is zero when the control deviation signal is in a predetermined positive or negative deviation range centered around zero. Surface control device. (5) The equalizing liquid level control device according to claim 1, wherein the reverse hysteresis signal obtained by the reverse hysteresis signal generating means has a binary level necessary for controlling on/off of the switch. . (6) The equalizing liquid level control device according to claim 1, wherein the adjustment calculation means performs PI adjustment calculation on the execution deviation signal. (7) The adjustment signal output control means is turned on in response to one level of the reverse hysteresis signal, applies the adjustment signal to the operating end side to execute the flow rate adjustment operation, and outputs another level of the reverse hysteresis signal. claim 1, wherein the control signal is turned off in response to the control signal, and the control end is controlled by forcibly holding the signal before turning off without giving the adjustment signal to the operating end.
The equalizing liquid level control device described in .