JPH062802A - Steam temperature control device for boiler - Google Patents

Abstract

PURPOSE:To improve a controlling performance in a steam temperature control device for a boiler by a method wherein its controlling operation is carried out under a consideration of a state of a damper in another system. CONSTITUTION:Signals (DELTATA, DELTATB) 4a, 4b obtained by subtracting steam temperatures TA, TB from set temperatures TAS, TBS by subtractors 3a, 3b are inputted to PID controllers 5a, 5b and a control circuit 10. The control circuit 10 calculates a total control deviation R defined by control deviations DELTATA=TA-TAS, DELTATB=TB-TBS in both systems A and B, and outputs correction signals DELTAYA, DELTAYB to adders 17a, 17b in response to the control deviation R larger than a predetermined value RS. The adders 17a, 17b add output signals 6a, 6b of the PID controllers 5a, 5b and the correction signals DELTAYA, DELTAYB received from the control circuit 10 and then outputs a result of this addition as new damper opening degree instruction signals (YA, YB) 18a, 18b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a boiler flue divided into two passages, and is applied to a boiler applied when controlling the steam temperature in the heat transfer section of each passage by a gas damper of each passage. The present invention relates to a steam temperature control device.

[0002]

2. Description of the Related Art FIG. 5 is a schematic view of a relevant portion of a boiler. In FIG. 5, 100 is a boiler body,
Reference numeral 101 indicates a furnace, and reference numeral 102 indicates a gas flow in the furnace. The partition wall 104 allows the gas to pass through 105a (flow path A) and 105
It is divided into two flow paths b (flow path B). Each channel 105
The heat transfer part (A) that gives heat to the steam inside a and 105b
106a and the heat transfer part (B) 106b are arrange | positioned.
Internal steam temperature T in both heat transfer parts 106a and 106b
A and TB have been measured, and are referred to as 1a and 1b, respectively. Further, dampers 107a and 107b for adjusting the flow rate of gas are interposed in the respective flow paths 105a and 105b. Steam temperature TA and TB are dampers 107a
And 107b respectively set temperatures TAS, T
Must be maintained at BS.

A conventional steam temperature control device using the dampers 107a and 107b is constructed as shown in FIG. In FIG. 6, 1a and 1b are the steam temperatures TA and TB of the heat transfer parts A and B as described above, and 2a and 2b are the preset temperatures TAS and TBS for the steam temperatures TA and TB. 3a and 3b are subtractors, which are set temperatures TAS,
Signals 4a and 4b obtained by subtracting steam temperatures TA and TB from TBS
Is output and input to the controllers 5a and 5b. Controller 5a,
5b is proportional / integral / derivative (PID) to the signals 4a and 4b
And the like to output opening instruction signals (YA, YB) 6a, 6b for the dampers 107a, 107b.

The operation of the conventional steam temperature control device described above is
The system will be described as an example. Now, for example, steam temperature TA of system A
As a result of the PID calculation by the controller 5a, the opening command signal 6a of the damper 107a increases and the damper 107a opens. As a result, the gas flow path 105a
Gas flow rate increases, and the internal steam temperature TA of the heat transfer section 106a rises and returns to the original level. The same applies to the B side system.

[0005]

However, in the above-described conventional control method, the two control systems A and B perform control operation without considering movements of the other systems at all, so movements of the other systems adversely affect each other. And the control performance may be deteriorated.

For example, even when the damper of the A system needs to be opened, if the damper of the B system is opening, the gas also flows to the B system side, so the gas on the A system side does not increase as expected, and the steam temperature The way TA rises slows down. On the other hand, if the damper of the B system is closing, the gas on the A system side may increase more than necessary, and the steam temperature TA will rise excessively. This is because there is no suitable index that can comprehensively monitor the control states of both systems.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to perform an operation in consideration of the states of dampers of other systems, thereby improving the control performance. The purpose is to provide.

[0008]

A steam temperature control apparatus for a boiler according to the present invention has a flue gas duct having two parallel gas flow paths A and B.
And the internal steam temperatures TA and TB of the heat transfer section disposed in the two flow paths A and B are divided into the set temperatures TAS and TBS, respectively.
In order to control so that the opening of the gas damper provided in each flow path is automatically adjusted by the corresponding controller, the control deviation of both A and B systems in the steam temperature controller of the two gas path boilers. ΔTA = TA-TAS, Δ
A total control deviation R defined by TB = TB-TBS is obtained, and when the control deviation R is larger than a predetermined value RS, the opening command signal for the dampers of both the A and B systems is output according to the magnitude of the magnitude. It is characterized in that a correction signal for either open or closed is added.

[0009]

When the total control deviation R is R <RS, the same control as the conventional control is performed, but when R> RS, it is determined that the total control deviation R of both the A and B systems is large. Therefore, the appropriate opening / closing signal is added to the opening command signals of both the A and B dampers, so that the control performance is improved. Further, since the conventional PID control function is maintained as it is, each temperature is finally settled at the set temperature.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a steam temperature control device for a boiler according to an embodiment of the present invention. The same parts as those of the steam temperature control device shown in FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, signals (ΔTA, ΔTB) 4a, 4b obtained by subtracting the steam temperatures TA, TB from the set temperatures TAS, TBS by the subtractors 3a, 3b are supplied to the PID controllers 5a, 5b and the control circuit 10. To enter. Details of the control circuit 10 will be described later. 16a and 16b are two output signals ΔYA and ΔYB of the control circuit 10. 1
7a and 17b are adders, which are output signals 6a and 6b of the PID controllers 5a and 5b and an output signal ΔYA of the control circuit 10,
ΔYB is added, and the result is output as new damper opening command signals (YA, YB) 18a, 18b.

FIG. 2 shows the details of the control circuit 10. The same signals as those in FIG. 1 are designated by the same reference numerals. Reference numeral 11 denotes a total control deviation calculating means, which inputs the control deviations ΔTA and ΔTB of the respective systems output from the subtracters 3a and 3b, calculates the total control deviation R by the following formula, and outputs it as an output signal 12. . R = (ΔTA ² + TB ² ) ^1/2 ... (1)

The meaning of the comprehensive control deviation R is shown in FIG. This total control deviation R is ΔT when the current set of control deviations (ΔTA, ΔTB) is viewed as coordinates on a plane.
The “distance” of the point (ΔTA, ΔTB) on the A-ΔTB plane from the origin is shown. In this case, the "origin" is
The control deviations of both the A and B systems are both "0", which means that the "distance" from the "origin" is
It shows the degree of deviation from the ideal. That is, the control deviation R is a suitable index for comprehensively monitoring the control states of both systems. Further, in FIG. 2, 13 is a signal value control means, which outputs S calculated by the following equation from the input R and the predetermined value RS. S = 0: When Z ≦ 0 S = Z: When Z> 0 However, Z = R-RS The above S is a signal indicating the degree to which the total control deviation R exceeds the predetermined value RS. Reference numeral 15a is a proportional control means of system A, which outputs a damper opening correction signal ΔYA calculated by the following equation using two inputs ΔTA and S. ΔYA = −KA × S: When ΔTA> 0 ΔYA = KA × S: When ΔTA ≦ 0 where KA is a proportional gain for the A system

Reference numeral 15b denotes a B-system proportional control means, which performs the same calculation as that of the A-system proportional control means 15a for the B system by the following equation and outputs a damper opening correction signal ΔYB. ΔYB = −KB × S: When ΔTB> 0 ΔYB = KB × S: When ΔTB ≦ 0 where KB is a proportional gain for the B system

Next, the damper opening correction signals ΔYA, Δ
The meaning of YB will be described by taking ΔYA as an example. ΔTA
When> 0, that is, when the internal steam temperature TA of the A system is higher than the set temperature TAS, the damper of the A system is closed to reduce the gas flow rate of the gas flow path A, thereby reducing the steam temperature TA.
Need to lower. Therefore, the signal S indicating the degree to which the total control deviation R exceeds the predetermined value RS is multiplied by the proportional gain KA of the A system, and the sign thereof is set to a negative value as the damper opening correction signal ΔYA. The damper opening correction signal ΔYA is added by the adder 17a to the opening command signal 6a of the system A damper output from the PID controller 5a.
As a result, the A system damper achieves an operation that also considers the state of the B system. When ΔTA ≦ 0, ΔYA may be added without making the sign of ΔYA negative.

In the above embodiment, the control circuit 10 is (1)
Although the case where the total control deviation R is obtained by the equation has been described, the total control deviation R may be obtained by the following equation (2). R = {(ΔTA / α) ² + (TB / β) ² } ^1/2 ... (2)

The meaning of the comprehensive control deviation R is shown in FIG. Although FIG. 4 shows a case where α> β, α <
In the case of β, the ellipse becomes vertically long, and in the case of α = β, it becomes a perfect circle.

When the current set of control deviations (ΔTA, ΔTB) is viewed as orthogonal coordinates on the plane, when the point (ΔTA, ΔTB) on the plane ΔTA-ΔTB is inside the ellipse, R <
RS, and when outside the ellipse, R> RS.
The shape and size of the ellipse can be changed by appropriately selecting the values of α and β.

The fact that the points (ΔTA, ΔTB) are outside the ellipse means that the total control deviation of both systems is large to some extent, so that Δ may be changed according to the magnitude of the size.
The control performance can be improved by calculating YA and ΔYB and adding them to the damper opening command signal.

[0020]

As described above, according to the present invention,
In addition to the conventional control function that controls the set values for both A and B systems, a suitable index that can comprehensively monitor the control status of both systems is used to set the total control deviation of both systems to a predetermined value or less. Since a function is added, both dampers do not operate by ignoring each other's dampers as in the past, but when the total control deviation of both systems exceeds a specified value, the state of the other dampers is changed. The operation is taken into consideration, and the control performance can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a steam temperature control device for a boiler according to an embodiment of the present invention.

FIG. 2 is a block diagram showing details of a control circuit in the embodiment.

FIG. 3 is an explanatory diagram of a comprehensive control deviation in the embodiment.

FIG. 4 is an explanatory diagram of a comprehensive control deviation in another embodiment.

FIG. 5 is a schematic diagram showing a schematic configuration of a boiler.

FIG. 6 is a block diagram showing a configuration of a conventional steam temperature control device for a boiler.

[Explanation of symbols] 1a, 1b ... Steam temperature, 2a, 2b ... Steam temperature set temperature, 3a, 3b ... Subtractor, 5a, 5b ... PID controller,
10 ... Control circuit, 11 ... Total control deviation calculation means, 13 ...
Signal value control means, 15a, 15b ... Proportional control means, 18
a, 18b ... Damper opening command signal.

Claims (1)

[Claims] 1. A flue is divided into two parallel gas passages A and B, and internal steam temperatures TA and TB of heat transfer sections arranged in the two passages A and B are respectively set temperatures TAS. , TBS, in order to control so that the opening of the gas damper provided in each flow path is automatically adjusted by the controller corresponding to each, in the steam temperature control device of the two gas path boiler, Control deviation ΔTA = TA-TAS, ΔTB
= The total control deviation R defined by TB-TBS is obtained,
When the control deviation R is larger than a predetermined value RS, a correction signal for either opening or closing is added to the opening command signal for the dampers of both the A and B systems according to the magnitude of the magnitude. Steam temperature control device.