JPH10183220A - Device for controlling pressure in furnace opening hole part of converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a furnace opening hole part pressure control device which can restrain and prevent pressure variation to disturbance as much as possible under as table condition due against a process fluctuation by arranging the furnace opening hole part pressure control device rationally executing a trade-off of the stability and the conrollability in a control system on a frequency. SOLUTION: At the time of recovering exhaust gas of a converter with an OG system, a linear model containing the delay of a pressure propagation from the furnace opening hole part 2 to a pressure adjusting device 4 in the converter 1, the delay of movement of the pressure adjusting device 4 and the delay of pressure detection with a pressure detector 5 fitted to the furnace opening hole part 2, is set. A compensator for reducing a complementary sensible function of a closed loop transfer characteristic in a pressure control system in a high frequency range based on an H infinity control theory to the pressure propagation delay variated with the operational condition in this linear model and a progress gain and for reducing this sensible function from low frequency range to the high frequency range as much as possible, is arranged. By this constitution, a time and an arithmetic load needed to the gain adjustment in a trial and error executed at the furnace opening hole part pressure control device 6 are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling a pressure at a furnace mouth of a converter when recovering a converter waste gas by an OG method.

[0002]

2. Description of the Related Art Generally, so-called PID control is used for pressure control of a furnace port when recovering converter waste gas by the OG method. That is, in the pressure control device as shown in FIG. 7, a pressure detector attached to the furnace port detects a pressure difference between the pressure in the furnace port and the atmospheric pressure, and the detected pressure difference and the target differential pressure are detected. The deviation from the pressure is input to a PID control device, and the control device is configured to instruct the pressure adjustment device to perform a PID operation amount corresponding to the differential pressure deviation. By controlling the pressure at the furnace mouth of the converter at approximately the same pressure as the atmospheric pressure by such control, it is possible to prevent the discharge of converter waste gas from the furnace mouth to the outside and the suction of air. Thus, it becomes possible to efficiently recover the converter waste gas.

[0003] In such a converter furnace port pressure control device, in order to sufficiently suppress the pressure fluctuation in the converter furnace port, for example, the gain of the PID control device is set as follows.
It is required that the control system be as large as possible within a stable range. However, in a control device having only three simple compensating elements such as PID control, it is difficult to set the control gain sufficiently large due to a change in process gain due to expected operating conditions or a delay factor of the process. is there.

Accordingly, for example, Japanese Patent Application Laid-Open No. Sho 61-174310
As disclosed in Japanese Patent Application Laid-Open No. 63-151506, a gain schedule method in which a control gain is changed while adapting a control gain in response to a change in process gain. A method has been proposed in which a disturbance observer control device for estimating a disturbance amount on-line in consideration of a delay element of a process as a model and compensating for the disturbance amount is applied. According to these control means,
Since the control device is set in consideration of the delay element of the pressure control system, the control gain can be further increased in a stable process range as compared with a simple PID control device.

[0005]

However, in these converter pressure control devices, when the pressure propagation delay or the process gain of the set process model changes due to the operating conditions, it does not match the actual process model. Since there is a difference between them, the stability of the control system may be impaired. Further, in order to avoid such a situation, in order to compensate for a trade-off between stability and controllability, for example, optimization control is incorporated, and a large amount of time and energy for arithmetic processing are used for control. There is a problem that the gain must be adjusted or switched.

The present invention has been developed in view of these problems. The stability of the control system is improved by considering the model error of the pressure control system from the setting stage while considering the model. Provide a converter furnace pressure control device that efficiently compensates for the trade-off with controllability due to the magnitude of control gain, is stable against process fluctuations, and can further prevent pressure fluctuations due to disturbances. It is intended to do so.

[0007]

The converter furnace pressure control device of the present invention is provided with a pressure regulator for adjusting the pressure of the furnace mouth of the converter. A device for controlling the pressure at the furnace mouth of the converter at the time of recovery, wherein a delay in pressure propagation from the furnace mouth of the converter to a pressure adjusting device, a delay in operation of the pressure adjusting device, and a A linear model including a delay in pressure detection by a pressure detector attached to the furnace opening is set. Based on the H-infinity control theory, a pressure propagation delay and a process gain that fluctuate depending on operating conditions in this linear model are set. A compensator for reducing a complementary sensitivity function of a closed loop transfer characteristic of the pressure control system in a high frequency region and reducing the sensitivity function from a low frequency region to a high frequency region as much as possible. .

According to the present invention, in order to solve the above-mentioned problems, when setting a control device using a model of a pressure control system, as described above, the pressure propagation delay and the fluctuation error range of the process gain can be assumed. Is evaluated by the complementary sensitivity function of the closed-loop transfer characteristic of the control system to ensure stability, and after determining the stability of the control system, a control device that reduces the sensitivity function so as to increase the control gain as much as possible, Set in the frequency domain based on H-infinity control theory.
More specifically, a stability weighting function represented by a transfer function to reduce the magnitude of the transfer function from the disturbance to the manipulated variable output in a desired high-frequency region, and from the disturbance to a point before the disturbance is added A controllability weight function represented by a transfer function is set to reduce the magnitude of the transfer function in a desired low-frequency region, and at least a model error due to a pressure propagation delay of the process model or a variation in process gain is set. A large stability weight function and a control weight function whose complementary sensitivity function based on the H-infinity control theory is small in a high frequency region and whose sensitivity function is small from a low frequency region to a high frequency region as much as possible are used. If the compensator, generally a controller, is constructed by solving based on the large control theory, the above-described stability and controllability are most efficiently achieved. And offs, for process variation stable and pressure fluctuations can be prevented as much as possible suppressed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows only a main part of a pressure control system of a furnace port by an OG system in which a converter furnace pressure control apparatus according to the present invention is implemented. The constituent elements of the pressure control system will be described in more detail. Waste gas generated inside the converter 1 is collected by a fan (not shown) through a pipe 3 disposed above the furnace port 2 of the converter 1. Is done. A pressure adjusting valve 4a of, for example, a poppet type is interposed in the pipe 3, and the movement amount of the poppet, that is, the opening of the pressure adjusting valve 4a is adjusted by a hydraulic cylinder 4b as an actuator. Therefore, the pressure regulating device 4 is controlled by the pressure regulating valve 4a and the hydraulic cylinder 4b.
Is configured. On the other hand, the furnace port 2 is
A pressure transmitter (pressure detector) 5 for detecting a pressure in the chamber and outputting a pressure difference from the atmospheric pressure as a furnace pressure PV is attached. The furnace pressure PV from the pressure transmitter 5 and a target not shown The target furnace pressure SV from the furnace pressure transmitter, that is, the target pressure difference between the pressure in the furnace port 2 and the atmospheric pressure, is a furnace port composed of, for example, a personal computer, a workstation, or a larger process computer. The pressure is input to a pressure control device (furnace pressure control device) 6, and the furnace pressure control device 6 outputs a command signal Y _(n) to the hydraulic cylinder using the deviation between the two.

The furnace pressure control device 6 includes an input / output interface (not shown) and a hard disk driver (HD).
D) and other storage devices, and ROs with built-in operation programs
M, a CPU that operates in accordance with the operation program, and an arithmetic processing unit that is composed of an electronic device such as a RAM that operates as a work area. It can be realized by a station or, in some cases, an information processing device such as a process computer. However, the output signal itself of such an information processing device cannot directly drive the hydraulic cylinder as the actuator, so that an appropriate interface or driver is required between the two.

Next, the configuration of the furnace pressure control device (hereinafter, also referred to as a controller in the system) will be described in detail. First, among the processes of the pressure control system shown in FIG. 1, as shown in FIG. 2, the detection delay of the pressure transmitter is reduced to (1 / T ₃ s + 1) of the first-order delay system, and the pressure propagation delay in the pipe is reduced to 1 The (1 / T ₂ s + 1) of the _second- order lag system and the operation delay of the pressure regulator, particularly the operation delay of the hydraulic system, are reduced by (T
₁ s + 1), and further, in consideration of the dead time e ^at and the pressure control gain K, these are connected in series to construct a process model P ₀ (s) of the system. Child). Therefore, the process model P ₀ (s) of this system is represented by the following equation.

[0012] Next, the process model P ₀ (s) and the above-described controller C (s) form a closed loop shown in FIG. 3, and further specify a location to which a disturbance is applied, and a transfer function from the disturbance to the manipulated variable output. And a stability weighting function W ₁ (s) represented by a transfer function to reduce the magnitude of the transfer function in a desired high-frequency region, and the magnitude of the transfer function from the disturbance to a point before the disturbance is added to the stability weight function. A controllability weight function W ₂ (s) expressed by a transfer function is set to reduce the frequency domain. And
In the control system of FIG. 3, the complementary sensitivity function (1 / (1 + P ₀ (s) C
(s)), the weighting function W ₁ (s) is set so that the closed-loop transfer characteristic is reduced in the high frequency region as shown in FIG. 4A, and the sensitivity function indicating the influence of disturbance on the reactor pressure fluctuation is set.
The weighting function W ₂ ((P ₀ (s) C (s)) / (1 + P ₀ (s) C (s)) is set to be as small as possible in the low frequency region as shown in FIG. By setting s), a process model P (s) that takes into account model errors called a generalized plant is constructed.

The above two weighting functions W ₁ (s) and W ₂ (s)
Is set as follows. First, the specific shape of the above-described complementary sensitivity function on the frequency is determined as follows. That is, in each element of FIG. 2 considered as a model this time, the pressure transmitter, which is a pressure adjusting device and a pressure detecting device, does not have a large difference between the model and the actual process. The model error of the transmission delay and the process gain is estimated as the model error Δ (s) shown in FIG. Here, as described above, with respect to the process model P ₀ (s) originally used, the generalized process model P (s) including the model error Δ (s) is expressed by the following equation (2). It appears in.

Δ (s) = (P (s) −P ₀ (s)) / · P ₀ (s) (2) In these two equations, the parameter of the above-described model error factor is changed within a fluctuation range. Thus, a model error Δ (s) is obtained, and the stabilizing weight function W ₁ (s) that always satisfies the following three equations is set for the model error Δ (s).

W ₁ (s)> Δ (s) (3) Therefore, even if the parameters of the above-described model error factors are changed, the stabilizing weight function W ₁ (s) that always satisfies the above equation (3).
If the complementary sensitivity function in FIG. 3 is set using the above equation, the process becomes stable even if there is a model error Δ (s). On the other hand, the above-described sensitivity function defines the sensitivity from disturbance, and it is desired to set the controllability weight function W ₂ (s) so that the sensitivity function becomes as small as possible. Since the sum of the complementary sensitivity function and the sensitivity function is always “1”, the weighting function W ₂ (s) is set so that the sensitivity function is as small as possible in a frequency region where the complementary sensitivity function has a large value. As described above, the stability weight function W ₁ (s) and the controllability weight function W ₂ (s) set in the present embodiment are expressed by the following equations (4) and (5).

[0016] Note that α, β, γ, c, d, e, f, g, and h in the equations are
Each represents a predetermined coefficient.

After calculating the weight functions W ₁ (s) and W ₂ (s) in this manner, the controller C (s) satisfying the following equation (6) is obtained.
Is obtained by the solution of Glover and Doyle in the H-infinity control theory (the Laplace operator s is omitted hereinafter).

[0018] When the controller C (s) is obtained in this manner, the following 7 is obtained.
Equations and matrices A, B,
Obtain C and D.

Dx (t) / dt = Ax (t) + Bu (t) (7) y (t) = Cx (t) + Du (t) (8) A: 8 × 8 , B: 8 × 1 matrix, C:
1 × 8 matrix, D: 1 × 1 parameter.

When this is discretized by bilinear transformation in order to be mounted on a digital arithmetic processing device such as a personal computer or a process computer as described above, the following equations 9 and 10 are obtained.

X (n + 1) = A "X (n) + B" U (n) ... (9) Y (n) = C "X (n) + D" U (n) ... (10) ) Where A ", B", C ", and D" are the bilinear transformations of the matrices A, B, C, and D, respectively, and U (n) is given by the following equation (11).

U (n) = SV (n) -PV (n) (11) This arithmetic processing is mounted on the digital arithmetic processing layer, and a converter furnace port pressure control device 6 is configured as an actual machine. .

FIG. 6 shows a state of the pressure fluctuation of the furnace port 2 when the auxiliary material is charged when a disturbance is applied to the control system in the furnace port pressure control apparatus of the present embodiment thus configured. FIG. 8 shows a state of the furnace port pressure fluctuation in the control. As is clear from both figures, it can be understood that the furnace port pressure control device of the present embodiment suppresses the pressure fluctuation of the furnace port 2 more than the conventional PID control. Further, it was confirmed that the present embodiment can reduce the pressure fluctuation which has conventionally occurred by about 40%. Also, the stability of the control system is applied without any problem in long-term continuous use. The adjustment after the initial setting can be performed without applying energy such as time and calculation load.

As described above, in the furnace port pressure control apparatus of the present embodiment, since the trade-off between the stability of the control system and the controllability is rationally performed by setting the frequency, the conventional error is included. It is possible to reduce the time and calculation load for gain adjustment by so-called trial and error, which was performed by setting the control device based on a model that does not have a furnace pressure, while maintaining the stability of the control system according to the accuracy of the model. Fluctuations can be improved to the limit.

[0025]

As described above, according to the converter furnace pressure control apparatus of the present invention, the trade-off between the stability of the control system and the controllability is rationally performed on the frequency. It is possible to reduce the time and calculation load required for the gain adjustment by trial and error, which must be performed in step (1), to stabilize the process variation and to prevent and suppress the pressure variation as much as possible.

[Brief description of the drawings]

FIG. 1 is a main schematic configuration diagram of a control system in which a converter furnace pressure control device of the present invention is implemented.

FIG. 2 is a block diagram of a basic process model of the control system shown in FIG.

FIG. 3 is a block diagram of a generalized process model including a model error in the process model shown in FIG. 2;

FIG. 4 is an explanatory diagram of a complementary sensitivity function and a frequency characteristic of the sensitivity function required in the process model shown in FIG. 3;

FIG. 5 is an explanatory diagram for setting each weighting function using a model error.

FIG. 6 is an explanatory diagram showing a furnace pressure fluctuation by the converter furnace port pressure control device of the present embodiment.

FIG. 7 is a main schematic configuration diagram of a conventional converter furnace port pressure control device.

FIG. 8 is an explanatory view showing a furnace pressure fluctuation by a conventional converter furnace port pressure control device.

[Explanation of symbols]

 1 is a converter 2 is a furnace mouth 3 is a pipe 4 is a pressure regulator 5 is a pressure transmitter (pressure detector) 6 is a furnace mouth pressure controller

Claims (1)

[Claims] An apparatus for controlling the pressure of a furnace mouth of a converter when recovering converter waste gas by an OG method, comprising a pressure adjusting device for adjusting the pressure of the furnace mouth of the converter. So,
A linear model including a delay in pressure propagation from the furnace mouth of the converter to a pressure regulator and a delay in operation of the pressure regulator and a delay in pressure detection by a pressure detector attached to the furnace mouth of the converter. In this linear model, the complementary sensitivity function of the closed-loop transfer characteristic of the pressure control system is reduced in the high frequency region based on H-infinity control theory with respect to the pressure propagation delay and the process gain that fluctuate depending on the operating conditions, and A converter furnace pressure control device comprising a compensator for reducing a sensitivity function from a low frequency range to a high frequency range as much as possible.