JPS631634B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an n:1 backup method for subloop controllers in a distributed hierarchical system consisting of a host computer and a plurality of subloop controllers.

Traditionally, as a highly reliable control device for large-scale control systems, computers are duplicated, and when a computer malfunctions, it switches to manual mode and displays an alarm at the same time.
A method is known in which the computer is switched based on the operator's judgment.

However, this method has disadvantages in that it is impossible to accurately diagnose abnormalities and it is not possible to save the labor of the operator.

Furthermore, conventional distributed systems in which the system is decentralized and the sub-loop control section is assigned to a plurality of controllers in accordance with the objects to be controlled have the disadvantage that there is no suitable backup method.

Furthermore, for n subloop control units, 1
In the conventional n:1 backup system in which multiple backups are provided, the backup range of the host controller cannot be arbitrarily set. For this reason, conventionally,
Mainly adopted are a method in which all specification tables of the subloop controller are stored in the upper controller, or a method in which a program for the upper controller is newly created independently of the subloop.

With the conventional backup method as described above, the program becomes extremely complex and large-scale, and
A drawback is that each time the program of the subloop controller is changed, the program of the upper controller must also be changed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hierarchical distributed control system that does not require an excessive increase in the scale of a backup host computer, allows easy program changes, and is inexpensive and highly reliable.

In order to improve the accuracy of abnormality diagnosis of the subloop controller, the present invention uses both the self-diagnosis of the subloop controller and the diagnosis by the master controller, and on the other hand, a part of the control contents of the subloop controller is stored in the host computer, such as By storing control processing contents such as normal load operation (for example, a specification table in the operating program), the host computer can directly control the operating terminal via analog memory in the event of an abnormality in the subloop controller. This is how it was done.

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

FIG. 1 shows an example of an application to which the present invention is applied, APC (Automatic
-matic Plant Control) system.

The solid-line rectangles in the figure are calculation elements that perform addition, subtraction, etc., and the areas surrounded by dashed-dotted lines each indicate the range of calculation processing performed by one microcontroller.

In the figure, 2 is the master controller, 3
is a subloop controller, 4 is an input processing controller, 5 is a switching relay, 6 is an analog memory,
7 is an electropneumatic converter, 8 is a solenoid valve, 9 is an oscillator, 10
a to 10c are control valves.

Also, 13 is a subtracter, 14 is a proportional integrator, 15
is an adder, 19 is a setter, 20 is a rate of change limiter,
21 is a control drive, and MWD is a central power supply command. Please note that this diagram is a simplification, and in an actual example, the number of calculation elements will vary from 500 to 500.
It will be 1000 pieces.

The APC system controls the main turbine governor valve, water supply valve, and other control valves to generate the amount of steam commensurate with the central power supply command MWD while maintaining the main steam pressure and main steam temperature constant.

That is, in response to the power generation command value S ₁ from the central power supply command MWD, the rate of change limiter 20 creates a signal that follows the command value within a predetermined rate of change, and sets a command for the main turbine and boiler input amount. Output as value _S2 .

This boiler input amount command value _S2 is corrected to keep the main steam pressure constant, and is set as a water supply command _S3 .
Furthermore, in order to keep the main steam temperature constant, the ratio between the water supply amount and the fuel amount is adjusted, and the command value for the fuel amount is
S ₄ is created and a command value S ₅ for the air amount that keeps the gas O ₂ constant is created and output.

The master controller 2 is the part that creates command values for the main turbine, water supply amount, fuel amount, and air amount.

According to these command values _S2 to _S5 , the main turbine governor valve 10a, the water supply control valve 10b, and the fuel valve 1
The subloop controller 3 is a part that directly controls control valves such as 0c and operating ends such as the control drive 21 that controls the amount of air.

Input processing also takes in signals from the transmitter 9, such as main steam pressure, main steam temperature, and gas _O2 , applies temperature correction and pressure correction to these signals, and sends the corrected signals to the master controller 2, etc. This is controller 4.

By the way, each of the above-mentioned microcontrollers can be configured by selecting and combining standardized calculation elements. Therefore, the software configuration is
As shown in the figure, a fixed processing program section 22 that executes standardized operations, the types of those operations,
It is divided into a specification table section 23 that describes the order of calculations.

Here, the fixed processing program section 22 is common to each controller, and only the specification table section 23 is unique to each controller and represents the control content of each controller.

Now, the specification table section 23 consists of an operation order table that represents the order of operations, and an operation specification table that represents the types of operations, connections, and the like.

For example, an adder (AD) 2 as shown in FIG.
4 and the PI computing unit (PI) 25, (a) For each computing element such as AD and PI, create a parameter table that stores the type, output, input point number, gain, etc. of each computing element. For each of the arithmetic specification table 27 that describes the start address, etc., and (b) the arithmetic specification table of (a) above, each start address and the total number of arithmetic elements N are described, and the order of operation of each arithmetic element is indicated. It can be expressed as the calculation order table 26.

Although FIG. 3 shows a case in which there is a single operation order table 26, it may be described in multiple pieces depending on the type of control, for example, normal control and startup control. Can be done.

In particular, in the present invention, among the control contents of the subloop controller having the above configuration, control contents with high necessity or urgency (for example, the above-mentioned normal control) and control contents with low necessity or urgency ( For example, the above-mentioned startup control). Then, the operation order table is divided into sections according to the above-mentioned divisions, and the specification table of the subloop controller is divided into two as shown in FIG.

That is, in FIG. 4, 3-1 and 3-2 are first and second subloop controllers. As is clear from the figure, each subloop controller 3-1, 3-2 includes a fixed processing program section 22-1, 22-2, and a specification table section 23-1, 23A-1, 23 divided into two. -2,
It is divided into 23A-2.

On the other hand, in the host computer 28, among the control contents of each subloop controller, only those with particularly high necessity and urgency are backed up, thereby simplifying the configuration.

That is, in the present invention, the host computer 28
are subloop controllers 3-1, 3-2,...
3-N has only a portion 23-1, 23-2, . . . 23-N of the specification table.

At this time, the host computer 28 and the subloop controllers 23-1, 23-2,...23-N,
Generally, there are different types of computers, such as minicomputers and microcomputers. Therefore, the languages used will also be different.

However, as mentioned above, if the software configuration is divided into the fixed processing program section and the specification table, even if the fixed processing program section is written in a different language, the format of the specification table section can be kept the same. becomes possible.

By utilizing this, even if the control content of the subloop controller is changed and the specification table is changed accordingly, the program on the host computer can be changed by simply transferring this to the host computer. It can be made highly maintainable.

The method for limiting the backup target range of a host computer has been described in general above, and the backup target range and non-backup target range will be further explained using a specific example.

FIG. 5 shows various characteristics at the time of startup of a thermal power plant. That is, the process is divided into a (startup control) process that involves raising the main steam temperature, pressure, etc., and a normal load control process after these are raised to predetermined values.

Among these, in a large-scale plant that performs n:1 backup, the start-stop operation is performed at most once every one to two weeks, and the time required for this is short. That is, it can be said that the time required for start/stop control is sufficiently short compared to the time for normal control.

For this reason, it is very advantageous to make the start-up control part a non-backup target range from the viewpoint of simplifying the configuration without significantly reducing the reliability of the system.

FIG. 6 is a control block diagram when the present invention is applied to the heavy oil control system in the APC system of FIG. In the figure, the same reference numerals as in FIGS. 1 and 4 represent the same or equivalent parts. 3
0 is a high value selection circuit, 31 is a sign discriminator, SW1~
SW3 is a changeover switch.

In FIG. 6, the portion surrounded by a dotted line is a portion involved in startup control, and in this example, is a portion that is not backed up by the host computer 28.

As is well known, when starting up, first connect switch SW2 to side 2.
Perform leak checks and warm up piping, etc. After the warming is completed, the ignition opening signal for the first cell is output, and the heavy oil judgment valve 10c is opened to the ignition opening of the first cell.

When one cell is ignited, the selector switch
The SW2 is moved to the 1 side, and the heavy oil valve 10 is moved to keep the header pressure constant based on the signal from the heavy oil burner header pressure transmitter 9 and the signal from the specified pressure setting device 19.
The opening degree control of c is performed.

As described above, while keeping the header pressure constant, the second cell, third cell, etc. are ignited to ignite the required number of burner sets. After the required number of cells have been ignited, the process moves to the heavy oil control valve opening degree control section according to the fuel amount command value _S4 according to the load. At this time, each of the changeover switches SW1 to SW3 is connected to the 1 side.

As is clear from the figure, the host computer 28 is
The subloop controller 3 does not have means corresponding to the startup control part, and therefore the startup control cannot be backed up. In this embodiment, the host computer 28 backs up only the heavy oil burner header pressure constant control and the fuel amount control according to the load during normal control.

For this purpose, the heavy oil control opening command from the subloop controller 3 is sent to the analog memory (AM) 6.
is memorized. On the other hand, the host computer 28 is supplied with the same input as the subloop controller 3, executes the same calculation, and generates the valve opening signal.

When an abnormality occurs in the subloop controller 3, the changeover switch SW3 is switched to the 2 side, and the immediately preceding valve opening signal is transferred to the subtractor 13 of the host computer 28. The subtracter 13 compares the transferred valve opening signal with the valve opening signal obtained by its own calculation, and supplies the difference to the sign determination section 31 .

The sign determination unit 31 supplies a raise or lower signal to a counter (not shown) in the analog memory 6 according to the sign of the difference, and updates the count value. The count value is converted into an analog quantity via a digital-to-analog converter, for example, and output as a valve opening signal.

That is, when the present invention is applied to a heavy oil control system as shown in Fig. 6, a specification table corresponding to the control range for burner ignition and extinguishing (the area surrounded by the dotted line) and other control ranges will be created. Separate the specification table and create it separately, and in the host computer,
It is possible to have only the specification table section other than the dotted line section.

By doing so, the configuration can be simplified without substantially reducing the actual backup function.

As is clear from the above explanation, according to the present invention, the specification table indicating control contents can be divided into two parts, and only important parts of the table can be stored in the host computer and backed up. , the scale of the host computer can be simplified and it can be made highly economical.

Furthermore, since the specification tables of the subloop controller and the host computer can be the same, the specification table of the subloop controller can be used as is on the host computer. Therefore, there is no need to change the program of the host computer, making it highly maintainable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a distributed hierarchical system to which the present invention is applied, FIG. 2 is a diagram showing the software configuration of a microcontroller, FIG. 3 is a diagram showing an example of the configuration of a specification table, and FIG. FIG. 4 is a diagram showing an example of the software configuration of a host computer and a subloop controller in an embodiment of the present invention.
FIG. 5 is a starting characteristic diagram of a thermal power plant, and FIG. 6 is a block diagram showing the control contents of a master controller, a subloop controller, and a host computer in a heavy oil control system to which the present invention is applied. 2... Master controller, 3... Sub loop controller, 6... Analog memory, 22... Fixed processing program section, 23... Specification table section, 26...
Calculation order table, 27... Calculation specification table, 2
8...Upper computer, 31...Sign discriminator.

Claims (1)

[Claims] 1. n subloop controllers that directly control the operating end, and a master controller that supplies command values (target signals) to each subloop controller so as to achieve mutual cooperation among the subloop controllers. This is an n:1 backup method of a distributed hierarchical system having a host computer that stores the specification table of the operating program of each subloop controller, and the specification table of each subloop controller is divided into the target range and non-backup target range. In addition to dividing into ranges, the host computer has only a specification table corresponding to the range to be backed up, and in the event of a failure of the subloop controller, the host computer directly controls the operating end via analog memory. n:1 backup method for hierarchical system. 2. The distributed hierarchical system according to claim 1, characterized in that the format of the specification table of the backup target range provided in the host computer is the same as that of the specification table of the backup target range of the subloop controller. n:
1 backup method.