JPH0525121B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention analyzes the characteristics of the plant in a thermal power plant, and optimally arranges control devices in a hierarchical manner in accordance with the characteristics. The present invention relates to an automatic control method that allows automatic operation to continue without stopping the plant even in the event of an abnormality.

[Background of the invention]

Conventionally, control devices in a thermal power plant have generally been arranged in groups of auxiliary machines constituting the plant. For example, it is a water supply control device that controls a group of water supply pumps that supply water to a boiler. In this case, failure of the control device makes it difficult to continue automatic operation of the plant, so methods such as duplication of control devices have been adopted as a measure to improve reliability.

Below, we will discuss the concept of system division based on plant characteristic analysis, the conventional method of arranging control equipment within it, and the problems associated with it.

Figure 6 shows system division focusing on the plant characteristics of a thermal power plant.

Thermal power plants are a collection of complex processes in which various functions are involved in a complex manner, and when classified based on the flow of materials and energy, they can be classified into combustion processes, water/steam processes, as shown in Figure 6. , power generation process, cooling process 4
It can be organized into one process.

The purpose of controlling a thermal power plant is to combine these four processes and cooperate with each other to stably supply power in response to external power demand.

Each process shown in FIG. 6 can be further classified into a plurality of sub-processes by focusing on its functions. Figure 2 shows the further classification of water/steam processes into sub-processes. 10 in the diagram
is a condensate subprocess, 11 is a low-pressure feedwater heating/deaeration subprocess, 12 is a water supply subprocess,
13 is a high pressure feed water heating subprocess, 14 is an evaporation/superheating subprocess, and 15 is a reburning subprocess.

The sub-processes include multiple small processes of equal capacity as necessary to strengthen the plant's capacity. Furthermore, small processes can be further subdivided into units of equipment.

Figure 3 shows the division of the 12 water supply sub-processes into smaller processes and equipment. 12A~
12C each indicate a water pump subprocess. The equipment in the small process is a water pump 12A1, a water pump transmission 12A2, and a water pump motor 12.
A3, water booster pump 12A4, water booster pump motor 12A5, water pump outlet valve 12A6, and water pump recirculation valve 12A7.

To summarize the above, the configuration of a power generation plant can be divided into process, subprocess, small process, and equipment levels as shown in FIG. If a failure occurs at the process level or subprocess level of the plant, it is impossible to continue operation of the plant, and the plant is often shut down. However, in the event of a failure at the small process level or equipment level, it should be possible to continue operation by reducing plant output.

However, in the past, the above-mentioned analysis of the plant was insufficient and the results were not reflected in the control device configuration. As shown in FIG. 5, an example of a water supply sub-process spans multiple small processes 12A to 12C. Focusing on the characteristics of the equipment, a water supply flow rate control device 30 for analog control equipment and a water supply flow rate control device 30 for ON-OFF control equipment are constructed. A water supply control sequencer 31 is arranged.

In this case, a failure of the control device 30 or 31 makes it impossible to continue automatic operation of the small processes 12A to 12C. This indicates that it becomes impossible to continue the automatic operation of all the small processes in the water supply subprocess 12, and poses a serious hindrance to the continuation of plant operation. Therefore, in order to enhance reliability, redundancy such as duplication of the control device or n:1 backup is required, and the system configuration of the control device becomes complicated. There are many examples of these, such as Special Publication No. 51-37744.

[Purpose of the invention]

From the above, the purpose of the present invention is to
It is an object of the present invention to provide a control method for a thermal power plant that can reduce the influence of control device abnormalities on plant operation as much as possible without duplicating control devices as much as possible.

[Summary of the invention]

The feature of the present invention is to classify plants by focusing on plant characteristics, and to control equipment at the lowest level.
DCM (Drive Control Module) SGC
(signal conditioning module), and above that a sub-loop control device corresponding to a small process, and above that a process,
By arranging a master control device corresponding to each sub-process to perform mutually coordinated control between processes and sub-processes, and installing a supervisory control device at the top level, all of these control devices are configured in a single system. be.

[Embodiments of the invention]

This basic idea is shown in Figure 1. 40 in the diagram
41 represents a device, 41 represents a small process, and 42 represents a subprocess. The SGC performs input signal processing of data from the process. A DCM is installed in each device and operates each device using control signals or manual commands. These SGCs and
The DCM is the smallest unit in the entire system and performs manual operations, equipment protection, and restrictions. The SLC is a sub-loop controller, which combines the DCM and SGC described above and is arranged to correspond to small processes, and performs analog control and sequence control. The MC is a master control device that supervises a plurality of subloop control devices MC and manages coordinated control between processes and subprocesses. SVC is a supervisory control device that performs high-function control such as comprehensive plant monitoring, man-machine interface, data logging, document creation, control program download, program modification, and predictive control.

Figure 7a shows an example of a control system configured for a drum boiler power generation plant based on the above basics.
Shown below. The control devices include a supervisory control device SVC, a master control device MC, and 15 subloop control devices SLC.
It consists of The master controller MC controls system frequency F, main steam pressure MSP, and economizer outlet gas O ₂
GO ₂ , air flow rate AIR, furnace draft FD, drum level DL, main steam temperature MST, reheat steam temperature
It controls the amount of control determined by the mutual relationship between multiple processes and sub-processes such as RST while cooperating with each other. subloop control device
SLC is power generation control (SLC1), mill control (SLC2)
~SLC7), air volume control (SLC8, 9), water supply volume control (SLC10-12), desuperheater outlet temperature control (SLC13, 14), gas distribution volume control (SLC15)
It performs control corresponding to each small process. FIG. 7b shows an example of a once-through boiler. As is clear from comparing these, the input signals and control circuits are somewhat different. However, in both cases the master controller MC provides the target signal for the subloop controller SLC. To briefly explain the circuit in Figure 7 using the example of the once-through boiler in Figure 7b, for the power generation command 1 from the central power supply command, correction due to fluctuations in the system frequency F, runback when large auxiliary equipment trips, and rate of change due to the plant. After performing the restriction, a command value 2 for the main turbine is output to the SLC1. This command value 2 is also the boiler input amount command value 2
The water supply amount command value is set to 3 by adding a correction to this to keep the main steam pressure MSP constant. Water supply amount command value 3
is compared with the water supply amount, the deviation is calculated by PI, and the water supply amount command value 4 of each water pump is set as SLC10 to 12.
is output to. Furthermore, the ratio of the water supply amount and the fuel amount is adjusted so that the main steam temperature MST is constant, and the command value 6 for the fuel amount is created, and the command value 8 for the air amount is set to SLC so that the gas O ₂ is constant.
Output to 8 and 9. The coal feeding amount command 6 is compared with the calorie-corrected total fuel amount, and the deviation is calculated by PI.
SLC2~7 as mill master command value 7 for each mill
Output to. Also, based on the set value, the main steam temperature,
A main steam temperature command value 5 that keeps the furnace draft and reheat steam temperatures constant is output to the SLCs 13 and 14, a furnace draft command value 9 is output to the SLCs 8 and 9, and a reheat steam temperature command value 10 is output to the SLC 15.

Main turbine, water supply amount, fuel amount, air amount,
The part that creates command values 1 to 10 for main steam/reheat steam temperature and furnace draft is the master controller MC.

The subloop controller SLC is a part that outputs control commands to operating terminals such as control valves and control drives according to these command values 1 to 10. The DCM outputs control commands from the subloop controller to the operating end, and also constitutes a manual operation circuit, which switches the output of the subloop controller and outputs manual operation commands during manual operation. In the case of a drum boiler, a command value corresponding to the water supply amount command 3 in the case of once-through flow is output as the fuel amount command 6'. In addition, the water supply amount command 3' is output by adding correction signals for the main steam flow rate and main water supply flow rate to the drum level command signal 3'' that keeps the drum level constant.Other than that, the output is the same as that of a once-through boiler. be done.

While FIG. 7 shows the system configuration with a focus on division of control functions, FIG. 8 shows the hardware configuration.

The symbols are the same as used in FIG.
50 is a serial data transmission loop that organically connects a plurality of distributed subloop control devices SLC, master control device MC, and supervisory control device SVC.

In this figure, 200 in the SVC is a printer, 201,
206 is a display, 202 is a keyboard, 2
03 is a floppy disk, 204 is a system console, 205 is a host controller used for predictive control, etc., and 207 is a monitoring controller. In addition, 208 is the SLC group, and 208
-1 is, for example, an SLC group for water supply control, and 208-
2 is an SLC group for mill control, and 208-3 is an SLC group for air amount control. One SLC has multiple
An SGC and a DCM are provided and connected by an I/O bus 60. In addition, the master control device MC has
There is no DCM and multiple SGCs are coupled by bus 60. Signal conditioning module
The SGC detects the state quantities of the power generation plant 100, and the drive control module DCM
drives equipment within the power generation plant 100. As described above, the control device of the present invention has a hierarchical structure as shown in FIG. 6, and as shown in FIG. Output.

FIG. 9 shows circuit parts related to one SLC. 50 is a serial data transmission loop that connects the subloop control device SLC to other control devices MC and SLC. Reference numeral 60 is an I/O bus that connects the subloop control device SLC and a plurality of SGCs and DCMs. The subloop controller SLC is
It is a processor consisting of BPU, memory, etc.
43 SGC and 44 DCM are a type of I/O device. Details of these SGC and DCM will be described later.

What is important here is that even if the sub-loop controller SLC, which is a processor, fails, the SGC will still transmit the signal received from the detection end of the plant 100 through a dedicated protection circuit 61 provided separately. The point is that the plant 100 can be protected by passing it to the DMC and operating the operating end as necessary. Because it has this protection function, the upper subloop controller SLC,
Even if the master control device MC is a single system, it is possible to construct a system that does not damage the plant.

Next, the details of the functions of the SGC will be explained with reference to FIG. For the signal from the detection end 70 in the figure
The SGC detects disconnection in block 71, performs signal processing such as nonlinear correction, square root, addition and subtraction in block 72 as necessary, and distributes the signal in block 73. The distribution destination is to a higher control device such as a subloop control device SLC via the I/O bus 60,
There are things that are distributed to indicators, DCMs, etc. without going through the I/O bus 60, so even if the upper control device fails, the I/O
Extracts and monitors process signals without going through the bus 60,
The biggest feature is that it can be controlled. Similarly, even in the event of a failure in the host controller, the process signal can be monitored by the block 74, and contact outputs for alarms and protection can be output to the outside without going through the I/O bus 60.
The feature is that the protection machine has autonomy.

The details of the function of the DCM for analog control will be explained with reference to FIG. A command signal inputted from the I/O bus 60 from the host controller SLC or the like normally drives the operating end 83 via a switch 80, an automatic/manual switch 81, and a voltage/current converter 82. The operation signal is compared with the operation end position feedback signal 85 in the abnormality diagnosis circuit 84 and checked. This check result and the operating end 8
3 automatic/manual status, operating end fully open/fully closed limit
The input from SW 86 is displayed as a lamp on manual operation station 88A by lamp logic circuit 87. Reference numeral 89 indicates an automatic/manual switching circuit, and 90 indicates an open/close logic circuit. The operating end 83 can be opened and closed by A feature of the DCM is that even if the upper control device fails and control commands from the I/O bus 60 are no longer input, the operating terminal can be opened and closed by manual operation and the operation of the protection circuit. Another DCM
The feature of this is a backup circuit 93. That is, in the event of a failure in the host controller SLC, the process feedback signal 211 taken in via the SGC is held in the holder 94 and used as a set value, compared with the process feedback signal in the comparator 95, and the proportional-integral calculator 96 and It has a function of controlling the process feed hack amount to the value immediately before the occurrence of the upper level failure via the switch 80.

The above SGC and DCM functions make it possible to ensure manual operation, protection functions, and minimum process feed hack control function even in the event of a failure of the upper control device (subloop control device SLC), resulting in a unified system configuration. It becomes possible.

Furthermore, the details of the function of the DCM for sequence control will be explained with reference to FIG. The automatic start/stop command from the host controller SLC given from the I/O bus 60 is condition-checked by the start/stop logic circuit 130, and the automatic/manual switching circuit 101 selects automatic when automatic, and the PB station 88D selects manual. When the switch gear 104 is activated by a manual start/stop command in conjunction with the conditions of the permission logic circuit 102,
Turn ON/OFF. Further, it is stopped by a command from the protection circuit 61. An abnormality diagnosis is performed by a diagnostic circuit 107 based on a feedback signal 106 from a switch gear 104 and an operation command. The diagnostic results and feedback signals are displayed on the PB station 103 by the ramp logic circuit 108. Even when used for sequence control, the main features of DCM are:
Even in the event of an abnormality in the upper control device (subloop control device), it is possible to ensure start/stop functions by manual operation and forced stop functions by protection logic.
In addition, in the figure, AND is a logical product, and OR is a logical sum.

An autonomous control method will be described in which, in the above configuration, when a higher-level controller fails, the lower-level controller backs up a part of the higher-level control function, thereby improving system reliability.

FIG. 13 shows a case where both the master MC and subloop SLC are normal. A breakdown of the control functions of the master MC will be explained. The system master main control 110 is an essential control regarding the cooperative control of the sub-loop. System master advanced control 111 is related to the subloop control and is provided to improve its controllability.

The system master auxiliary control 112 is a restriction circuit related to the subloop control, a control circuit for starting and stopping, and the like. The master creates commands for coordination among the subloop controls using 113 from these controls and load commands, and sends them to the subloop controllers SLC-A,
Give to SLC-B and SLC-C.

The details of each subloop control device SLC can be classified into a subloop main control 114 which is essential as subloop control, a restriction 115 which is additional control, and a nonlinear correction 116.

In the present invention, the functions are divided as shown in Fig. 13, and the characteristic feature here is that the subloop control device
The SLC has a processing section 110' similar to the system master main control section 110 of the master control device MC in its upper system, and the drive control module DCM has a processing section 110' similar to the subloop main control section 114 of the subloop control device SLC in its upper system. It has a processing section 114'. 110' or 114' usually only receives the same input as 110 or 114, and specifically is only on standby.

FIG. 14 is an explanatory diagram of functional degradation backup control by the subloop control device SLC when the master control device MC fails. 110'A has the same function as the system master main control 110 in FIG. 13 provided in the subloop control device SLC-A. In the event of master control device MC failure, subloop control device SLC-A
Among the control functions of the master controller MC, only the essential 110 functions are executed by the master controller 110'.
Instead of MC, subloop control SLC-C, SLC-
Give a command to B, and subloop SLC-A to SLC-
Maintain coordination between C. This is the functional degeneracy backup function of the subloop control device SLC when the master control device MC fails.

Next, Fig. 15 shows the subloop control device SLC.
-A also shows the function degradation backup by DCM when a failure occurs. 114' is the main control function 11 in the subloop control device SLC provided in the DCM.
This function is equivalent to that of 4, and this enables the DCM to execute only the main control function of the subloop when the subloop control device SLC-A fails.

The above is the basic principle of an autonomous control method using a highly reliable single system control system based on the optimal hierarchical distributed arrangement of control devices based on plant characteristics and functional degeneracy backup.

An embodiment of the functional degeneracy backup function of the present invention will be described below, taking water supply subprocess control as an example.

FIG. 16 shows the control of the water supply sub-process 12 during normal operation. A detection signal from the master controller MC is input through the I/O bus 60 via each SGC.

P _1ST is the pressure after the first stage of the turbine, and is converted into the main steam flow rate MSQ by the function generator 141.
MST is the main steam temperature, and the main steam flow rate is the output of 141 by the function generator 143 and multiplier 144.
Perform temperature correction for MSQ. DL is a drum level, which is compared with the set value of 147 by a comparator 146, subjected to nonlinear gain correction by a function generator 148, and then input to a proportional integrator 149, whose output is sent to an adder 15.
At 0, it is added to the main steam flow rate MSQ as the preceding signal to become the command value of the total water supply flow rate. MSF is the total feed water flow rate and the multiplier 1 is calculated by the feed water temperature TSF.
53, the temperature is corrected, a comparator 154 compares it with the command value, a function generator 155 and a multiplier 156 add gain correction from the main steam flow rate MSQ, and input it to a proportional integrator 157, whose output is used for each water supply small process. This is the water supply flow rate command. This command value is transmitted to each water supply subloop control device SLC-A, SLC-B, and SLC- via the serial data transmission loop 50.
given to C. 110A' is a degenerate backup function provided within the subloop control device SLC. Commands from the master MC pass through a 160A upper limit circuit via a switch 159A to comparator 1.
Water pump 1 detected at 162A by 61A
It is compared with the flow rate feedback signal of 63A, subjected to gain correction by a function generator 164A and a multiplier 165A, and inputted to a proportional integrator 166A. The output is non-linearly corrected by the function generator 167A and given to the DCM-A via the I/O bus 60 as a pump rotation speed command.

114A' is a degenerate backup function provided in DCM-A. Rotation speed command is switch 169
A, 171A is applied to the pump transmission 172A to control the speed.

FIG. 17 shows an example when the master control device MC fails. Water supply subloop controller SLC−
A's degenerate backup function 110A' operates and the subloop controller SLC-B, instead of the master, operates.
Outputs water supply command to SLC-C. SLC-A inputs drum level signal 145 and sets value 180.
A is compared with A by a comparator 181A, and the output is sent to a proportional integrator 182A, and the output becomes a water supply command for each pump.Through a switch 159A, one is used as an automatic water supply command, and the other is sent to a serial data transmission loop 5.
0 becomes the water supply command for the water supply sub-loop SLC-B and SLC-C. In this way the water supply subloop
SLC-A coordinates with SLC-B and SLC-C to continue drum level control.

The switch 159A is switched by constantly monitoring the water supply command signal from the master control device MC with the subloop controller SLC-A, and when the signal disappears.

FIG. 18 shows a case where the water supply subloop SLC-A also fails when the master controller MC fails. In this case, the control function of the master MC is the degenerate pack-up function 110 in the water supply subloop SLC-B.
The command value is transferred to the water supply subloop SLC-C via the serial data transmission loop 50.
It is possible to control the drum level in coordination with SLC-B and SLC-C.

Further, the DCM-A disposed in the water supply subloop SLC-A at this time can perform feedback control of the pump flow rate by operating the degenerate backup function 114A' provided therein. i.e.
Detector 162A given to DCM-A by SGC
The pump flow rate signal from is compared with a set value 190A by a comparator 191A and given to a proportional integrator 192A to become a pump speed command and a switch 169A.
It is applied to the transmission of the pump 172A through the 172A to control the speed.

Also, as in the case of the supply loop controller, switching of the switch 169A is performed by constantly monitoring the water supply flow rate command signal for the water supply small process from the supply loop controller SLC using the DCM, and when the signal stops coming.

Figure 19 shows the subloop control device SLC for each system.
shows an example of the process input signals required to back up part of the control function of the upper MC when the master control device MC fails. By configuring the system master main control circuit in the subloop control device SLC using this process signal as the control target signal, even if it is not possible to follow the fast load changes like when the master control device MC is normal, it is possible to It is possible to follow slow load changes. For example, for a drum boiler, the water system is at the drum level, the fuel system is at the main steam pressure, and the air system is at the gas O2 pressure.
2. Furnace draft in gas systems and reheating steam pressure in recirculation systems are the process signals to achieve the above objectives.

On the other hand, when the subloop control device SLC fails, cascade control using command signals from the subloop control device is not possible, but the process signal of the operating end controlled by the DCM is taken into the DCM, and this process signal is used as the control target signal to be used as the subloop main control. By configuring the control circuit, it is possible to perform fixed value feedback control using the set value in the DCM.
Minor process disturbances can be absorbed at each operating end. FIG. 20 shows an example of a process signal taken into the DCM at the time of SLC failure.

For example, in the water subloop, the flow rate of each water pump, in the fuel subloop, the coal flow rate of each mill,
In the primary air flow rate, air, gas, and recirculation subloop, each fan discharge pressure is the process signal to achieve the above objectives.

Furthermore, the normal subloop control device SLC is assigned to each of a plurality of groups of the same kind of operating terminals for each system.
(For example, 3 groups for water supply system, 6 groups for fuel system,
(Air system 2 groups, etc.) As a result, one SLC unit failed and the operating terminal controlled by the related lower DCM failed.
Even if fixed-value feedback control is performed using the set value in the DCM, the remaining normal operating terminals on the SLC side can perform cascade control, which makes it possible to follow even slight changes in load.

〔Effect of the invention〕

As described above, according to the present invention, even in a hierarchical distributed single configuration system of a power generation plant,
This has the effect of allowing plant operation to continue even in the event of a control device failure, making it possible to construct an economical and highly reliable control system.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the basic concept of the control device arrangement in the present invention, Figure 2 is a diagram showing the configuration of sub-processes in the water/steam process, and Figure 3 is a diagram showing the small processes in the water supply sub-process. Figure 4 is a diagram showing the structure of a thermal power plant, Figure 5 is a diagram showing the relationship between conventional processes and the arrangement of control devices, and Figure 6 is a diagram showing the structure of a thermal power plant. 7 is an example of the control system configuration based on the concept of the present invention, FIG. 8 is the hardware configuration, and FIG. 9 is a diagram showing the basic system configuration of the present invention. Figure 10 is a functional diagram of the SGC, - Figure 11 is a functional diagram of the DCM for analog control, Figure 12 is a functional diagram of the DCM for sequence control, and Figures 13 to 15 are backup diagrams in the event of a control device failure in the present invention. Figures 16 to 18 are diagrams showing the concept of the method, and Figures 16 to 18 are diagrams illustrating an embodiment of the present invention using a water supply system as an example. Figures 19 and 20 are diagrams showing the steps required to perform backup in the lower controller in the event of a failure in the upper controller. It is a figure which shows an example of a process signal. 43...SGC, 44...DCM, 45...Sub loop control device, 46...Master control device, 47
...Monitoring control device, 61...Protection circuit, 60...
I/O bus, 50...MΣNET, 110...System master main control, 111...System master advanced control, 112...System master auxiliary control, 11
3...Coordination, 114...Subloop main control, 11
5...Limit, 116...Nonlinear correction.

Claims (1)

[Claims] 1. A first controller that creates command signals regarding plant quantities necessary to generate a predetermined amount of power in response to load request commands from the outside;
a second controller that creates operation signals for operating various equipment of the power plant in response to command signals created by the controller; In a method for controlling a thermal power plant that controls equipment and generates power according to a load request command, the second controller controls the functions of the first controller, such as power generation amount, water supply amount, fuel amount, and air amount. , the control target command creation function for the control target command creation function for gas volume, or gas recirculation amount, which is necessary to continue automatic operation according to the load request command for the process that is shared by the second controller. has an alternative configuration to achieve the function, and when the first controller is out of function, of the plant quantity that was fed back to the first controller before the outage,
The predetermined plant amount for the automatic operation continuation function is fed back to the alternative configuration, the command signal is created using the alternative configuration, and the command signal is used to continue automatic operation according to the plant load request command. A method for controlling a thermal power plant, characterized by: