JPH0628002B2 - Plant control equipment - Google Patents

Description

The present invention relates to a plant control device.

For example, in thermal power plants, the functions have been diversified in recent years, and a high degree of automation has been achieved with the aim of saving labor, and in response to this, the plant controller also uses a minicomputer instead of conventional analog control. However, the problem here is the reliability of the system. For example, if the central processing unit of the computer stops, the system will immediately go down, and in the worst case, There is a fear of becoming a plant trip due to this.

Therefore, in order to improve the reliability of the plant control device, the present inventor gives the same function to three minicomputers, always operates all three online, and outputs 2/3 circuits (3/3 circuit) at the output of each minicomputer. 2 out of 3 logic circuit)
It was considered that one plant equipment such as a control valve and a damper can be controlled via the control system so that even if one of the three minicomputers in operation fails, the remaining two control the plant normally.

However, in the configuration of the two out-of-three logic circuit that controls one plant device by using three minicomputers, if the three minicomputers independently perform proportional integral calculation, one of the three Proportional-integral operations can diverge. The reason is that the process input signals of the three minicomputers always have a difference in the read values, and due to this difference, there is a continuous deviation from the set value. For the computer, since the feedback control state is not formed, the deviation is integrated and diverged. As described above, when one or two of the three minicomputers diverge, the normal configuration of the two out-of-three logic circuit cannot be maintained.

However, the signal input accuracy of the minicomputer is
There is always some error, and it is difficult to read the three independent minicomputers with exactly the same value in terms of equipment accuracy.

The present invention has been proposed in view of such circumstances, and an object of the present invention is to solve the above problems and to provide a plant control device that improves reliability. For this reason, three units each having the same process signal and having the same algorithm are input. Computer and
A PI controller with tracking, which is provided in each of the computers and which tracks each of the computers to the control device position when the process value approaches the target value, and 2 out of 3 logic for inputting the outputs of the three computers. It is characterized by having a circuit.

That is, according to the present invention, even if there is a slight difference in the process input signal, the proportional-plus-integral calculation does not diverge.
By temporarily interrupting the proportional-plus-integral calculation and adjusting the output to the control valve opening (tracking), it is possible to prevent divergence and maintain the normal 2 out-of-3 logic circuit configuration. Is what you can do.

The present invention has been proposed in view of such circumstances, and an object of the present invention is to solve the above-mentioned problems and to provide a plant control device that improves reliability. Input of the outputs of the three computers, the PI controller with the tracking, which is attached to each of the computers and simultaneously tracks each of the computers to the control device position when the process value approaches the target value. It is characterized by having 2 out of 3 logic circuits.

An embodiment in which the present invention is applied to the water supply level control of a drum of a thermal power plant will be described with reference to the drawings. FIG. 1 is a block diagram showing the principle thereof, and FIG. 2 is a block line showing the circuit configuration of FIG. It is a figure.

In the figure above, NO.1CPTR, NO.2CPTR and NO.3CPTR are the first, second and third minicomputers 1-1 and 1-1, respectively.
2-1 and 3-1 are subtractors, 1-2, 2-2 and 3 respectively.
-2 is a signal oscillator (SG), 1-3, 2-3, respectively.
3-3 are PI controllers with tracking (TP
I), 1-4, 2-4, 3-4 are high and low monitors (HLM), 1-5, 2-5, 3-5 are comparators, 6 is 2 out of 3 logic circuit, 7 is An AND circuit, 8 is a pulse generator (PG), 9 is a pulse / pneumatic pressure converter (P / PN), and 10 is a control valve.

The tracking PI controller 1-3, 2-3,
3-3 has a tracking function in the comparison and integration calculator (PI controller).

In FIG. 2, the difference between the set value C output from the signal transmitters 1-2 to 3-2 and the process signals A _{1 to} A ₃ to be controlled is output by the subtracters 1-1 to 3-1. Then, the PI controllers 1-3 to 3-3 perform calculation to reduce this deviation to zero, and the opening command values Y ₁ (X) to Y for the control valve 10 are calculated.
_The state in which ₃ (X) is output is the feedback control state by normal proportional integration.

Further, the tracking function is a feedback control state based on the normal proportional-plus-integral, and the PI controllers 1-3 to 3-3 interrupt the proportional-plus-integral calculation to output the output Y.
It is a function of adjusting ₁ (X) to Y ₃ (X) to the opening X of the control valve 10.

In such a device, as the process signal, for example, the water level signal A of the drum is input to each CPTR and NO.
The values R1 and A2 for NO.2 CPTR and A3 for NO.3 CPTR are read by subtractors 1-1, 2-1, and 3-1 respectively. Since the structure of each CPTR is the same, the NO.1 CPTR will be mainly described in the following description. The subtractor 1-1 includes a drum level set value C set by the signal generator 1-2.
There are input, the deviation value deviation C-A ₁ is obtained between the drum level current value A ₁ by the subtractor 1-1 is input to TPI1-3, is input to HLM1-4. HLM1-4
The allowable error of the deviation value is detected with, that is, it is determined whether or not −ε <(C−A ₁ ) <ε, and −ε <(C−
When A ₁ ) <ε, the HLM 1-4 outputs a signal of Z = 1, and otherwise, outputs Z = 0. HLM2-4,3-4
However, the same calculation is performed and the signal is output.

The signal Z from HLM1-4 is input to TPI1-3 and Z = 0
When the In TPI1-3, calculation of proportional integral is performed on the basis of the deviation value C-A _1, although the value Y ₁ is output,
When a signal of Z = 1 is input to TPI1-3, the tracking function described above causes P / PN9 to TPI1-3.
The actual valve opening value X which is the value input to TPI1-
It is output from 3.

Further, the signal Y ₁ output from the TPI _1-3 and the valve opening value X are input to the comparator 1-5 and are compared with each other to obtain Y ₁ −.
Depending on the deviation of X, a digital signal of +, 0, or-is output.

The same calculation is independently performed in NO.2CPTR and NO.3CPTR, and the output signals of the comparators 1-5, 2-5, 3-5 are input to the 2/3 circuit 6, and at least two signals are the same. If so, the same signal (+ signal if NO.1 and NO.2 are + signals) is output and input to the AND circuit 7. In the AND circuit 7, the pulse sent from PG8 is cut based on this signal. It is turned off and sent to the P / PN 9, and in the P / PN 9, it is converted into air pressure based on the signal from the AND circuit 7, and the opening degree of the control valve 10 is controlled by the air pressure.

When the opening degree of the control valve 10 changes and the process value A changes to B, the same calculation is performed based on the process value B to control the control valve 10.

The present invention is, in addition to the above embodiment, a boiler turbine coordinated control,
This can be widely applied to turbine acceleration control, turbine load control, turbine bypass control, automatic mill burner control, and the like.

In short, according to the present invention, the three computers connected to the two out-of-three logic circuits respectively input the same process input signal, and when the process input signals approach the target value, the three computers are connected. Since the PI controllers provided inside each independently track, even if there is a difference in the read value of the process input signal among the three computers, a device for forcibly tracking from the outside is provided. It is possible to prevent the PI controllers in the three computers from diverging because the tracking can be done independently regardless of whether it is diverging or not. A controller is obtained,
It is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle of the present invention, and FIG. 2 is a block diagram showing an embodiment in which the present invention is applied to drum water level control of a thermal power plant. NO.1CPTR …… The first minicomputer, NO.2CPTR ……
2nd minicomputer, NO.3CPTR ... 3rd minicomputer, 1-1, 2-1, 3-1 ... Subtractor, 1-
2, 2-2, 3-2 ... Signal transmitter, 1-3, 2-3,
3-3 Proportional-integral calculator with tracking, 1-4, 2
-4,3-4 ... High and low monitor, 1-5,2
-5, 3-5 ... comparator, 6 ... 2 out-of-three logic circuit, 7 ... AND circuit, 8 ... pulse generator,
9 ... Pulse / pneumatic pressure converter, 10 ... Control valve.

Front page continued (72) Inventor Naomi Nakamura 1-1, Atsunoura-machi, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Miki Kurihara 1-1, Atsunoura-machi, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries Nagasaki Shipyard Co., Ltd.

Claims (1)

[Claims] 1. A computer provided with three computers each having the same algorithm for inputting the same process signal and having the same algorithm, and when each process value approaches a target value, each computer tracks the control device position. A plant control device comprising a tracking PI controller and a 2 out of 3 logic circuit for inputting outputs of the three computers.