JPS61205703A - Automatic controller for thermal power plant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a system configuration of an automatic control device for a thermal power plant, and in particular to a plant suitable for reducing mutual interference between systems and applying a system-based distributed control system. Related to automatic control equipment.

[Background of the Invention] First, a schematic configuration of a thermal power plant will be described with reference to FIG. 2. In the figure, 1 is a boiler, 2 is a turbine, 3 is a generator, 4 is a water pump, 5 is a spray valve, 6 is a fuel valve, 7 is a forced draft fan, and 8 is a gas recirculation fan.

Furthermore, in the figure, 301 is an air preheater that preheats combustion air using combustion exhaust gas, and 302 is a burner section, which is a system that performs denitrification in the furnace by adjusting the air-fuel ratio for each stage. 303 is a W/B inlet air damper which increases the amount of combustion air in each burner stage by +1[11]. 304 is a 0M gas damper that adjusts the amount of combustion exhaust gas injected into the combustion air.

305 is a primary gas damper that adjusts the amount of combustion exhaust gas directly injected into the burner section. 306 is a condenser,
307 is a low pressure feed water heater, 308 is a deaerator, 309 is a water supply valve, 310 is a high pressure feed water heater, 311 is an evaporator, 31
2 is a primary superheater, 313 is a first stage desuperheater, 314 is a secondary superheater, 315 is a second stage desuperheater, 316 is a tertiary superheater,
317 is a reheater. Further, 330 is a turbine inlet control valve. If this is classified into systems according to boiler state quantities, it can be divided into four systems: combustion process 9, steam process 10, fuel process 11, and ventilation process 12.

An example of a control device of the conventional system according to FIG. 3 is shown.

In the figure, 20 is the power generation plant of FIG. 2, and 21 is a plant automatic control device. 22 is a complement relay board that performs interlock control of various ON-OFF control auxiliary machines that make up the plant; 23 is a burner control device that performs burner on/off control; and 24 is a main turbine that performs speed governing control of the main turbine. The control device 25 is a turbine control device for driving the water supply pump. The plant automatic control device 21 has a hierarchical configuration including a plurality of microcontrollers 31 to 35.

Of these, 31 is a master controller that controls the overall output of the plant and creates command values for each controller 32-35. 40 is a load command to the plant from the central power supply station. 41 is a circuit that creates a load command by adding restrictions such as a load change rate and a lower limit to this command. 4
2 is a subtracter which compares the above-mentioned load command L1 with the amount of power generation 43. The output is input to the proportional integral calculator 44, and the output is given to the main turbine control device 24 via a switch 45 switched by an interlock described later to control the turbine inlet control valve 330 shown in FIG. 46
is the main steam pressure (boiler outlet pressure) detector and subtractor 4
At step 7, it is compared with the value set by the setter 48, and its deviation output is input to the proportional-integral calculator 49. The output of 49 is added to the load command by an adder 50, and the boiler input command becomes a roar. Further, the output 4 of the proportional-integral calculator 49 is given to the main turbine control device 24 via the switch 45. The switch 45 is switched depending on the operation mode of the plant.

That is, in the turbine follow mode in which the main steam pressure is controlled by the main turbine input control valve 330, the output of the switch 45 becomes the input from the proportional integral calculator 49. In the normal cooperative mode, the output of the switch 45 becomes the input from the proportional-integral calculator 44. The boiler input command R, which is the output of the adder 50, is given to the water supply controller 32 as a water supply command, and on the other hand, is input to the interval generator 51. This function generator 51 is programmed with the fuel amount relative to the water supply amount, and its output is the fuel amount command. Reference numeral 52 denotes a main steam temperature detector, which is compared with a value set by a setter 54 by a subtracter 53, and the deviation is inputted to a proportional integrator 55 and becomes a main steam temperature correction command LT. This deviation, in turn, is provided to the main steam temperature controller 33 to operate the spray valve 5 of FIG.

The output of the proportional integrator 55 is sent to the function generator 5 by an adder 56.
The fuel amount command value added to the output of 1 and corrected becomes 1. 57 is a function generator which programs the optimum air amount L1 for the fuel amount. 58 is 0 remaining in combustion exhaust gas
It is a two-concentration detector, and is compared with a set value programmed according to the fuel amount by a function generator 59 in a subtracter 60, and the deviation is inputted to a proportional-integral calculator 61. The output of the proportional-integral calculator 61 is input to a multiplier 62 and becomes the corrected air amount command value LAA. Reference numeral 63 denotes a total air flow rate detector supplied to the boiler, which is compared with a command value LAA by a subtracter 64, and its deviation output is input to a proportional-integral calculator 65. The output of the proportional integral calculator 65 becomes a correction signal LAIl of the air amount command value for each burner stage and is given to the air amount control controller 34 a ''n for each burner stage. is given to the ventilation control controller 35.

Next, each controller 32 to 35 will be explained.

32 is a water supply controller. Reference numeral 66 denotes a detector for the total water supply flow rate to the boiler, which is compared with the command value by a subtractor 67, and its deviation output is input to a proportional integrator 68. The output of the proportional integrator 68 becomes a flow rate command to each water supply pump 4. 69 is a flow rate detector of the water supply pump, and subtractor 7
0 is the set value, and the deviation output is compared with the proportional integrator 7.
1 is input. The output of the proportional integrator 71 becomes a command for each pump and serves as a turbine control device 25a, 2 for driving the water supply pump.
Water supply pump turbine 4a via 5b.

4b and to the water supply valve 309.

33 is a temperature controller. Here, 72 is an M burner fuel valve 6b and a P burner fuel valve 6b for denitration in the boiler furnace.
This circuit distributes the amount of fuel.

Reference numeral 73 designates a fuel flow rate detector on the M burner fuel valve 6b side, which is compared by a subtractor 74, and its deviation output is input to a proportional integrator 77 and becomes an operating signal for the M burner flow valve 6b. 75
is a fuel flow rate detector on the P burner fuel valve 6a side, which is compared with a subtractor 76, and its deviation output is input to a proportional integrator 78 and becomes an operation signal for the P burner flow valve 6a. Further, in the controller 33, 79 is a proportional calculator, and a subtracter 5
By inputting the main steam temperature deviation which is the output of step 3, the set value of the outlet temperature of the attemperators 313 and 315 shown in FIG. 2 is obtained.

Reference numeral 80 denotes a desuperheater outlet temperature detector, which is compared with a set value in a subtractor 81, and its deviation output is input to a proportional integrator 82 and becomes an operating signal for the spray valve 5 in FIG. 83 is an adder and represents the total fuel flow rate.

34a to 34n are air flow rate controllers for each burner stage. Here, 34a will be explained as an example. 84 is a ratio signal of the number of ignited burners in the burner stage to all ignited burners. A multiplier 85 calculates the amount of fuel in the burner stage based on the ratio signal 84 and the output (total fuel) of the adder 83. Reference numeral 86 denotes a function generator, which programs the air amount of the burner stage based on the fuel flow rate of the burner stage. A multiplier 87 corrects the air amount command value for the burner stage in accordance with the total air flow rate correction signal LA1 output from the proportional integrator 65.

88 is an air flow rate detector for the burner stage concerned, and a subtractor 89
The output of the deviation is input to the proportional integrator 90 and becomes the W/B input rotor damper 303 operation signal that controls the air amount in the burner stage. Reference numeral 91 is a function generator that programs the exhaust gas mixture flow rate corresponding to the air amount in the burner stage. 92 is a flow rate detector for exhaust gas mixed with the air in the burner stage, which is compared with a subtractor 93;
The deviation is input to the proportional integrator 94 and becomes an operating signal for the OM damper 304 that controls the amount of mixture of exhaust gas. Reference numeral 95 denotes a function generator that programs the primary gas flow rate corresponding to the air amount in the burner stage. Reference numeral 96 denotes a flow rate detector of exhaust gas (primary gas) injected into the burner of the burner stage, which is compared with a set value in a subtractor 97, and the deviation is inputted into a proportional integrator 98, and the primary gas damper 305 It becomes the operation signal.

35 is a ventilation control controller. Reference numeral 99 is a function generator that programs the outlet draft setting of the forced draft fan from the total air flow rate command LAA. 100 is the outlet draft detector of the forced draft fan, and the subtractor 1
01, and the deviation output thereof is inputted to a proportional integrator 103 via a switch 102, and further provided by a load distribution circuit 104 as a moving blade operation signal for a forced draft fan (FIGS. 7a and 7b). A switch 102 switches the control mode of the forced draft fan.1 Normally, the input from the subtractor 101 is output to control the fan outlet draft, and when the plant is started, the input from the subtractor 65 is output to control the total air flow. It controls the flow rate. 105 is a function generator that programs the outlet draft setting of the gas recirculation fan from the total air flow command LAA. Reference numeral 106 is a gas recirculation fan outlet draft detector, which is compared with a subtractor 107, and its deviation output is input to a proportional integrator 108, and further transmitted to the gas recirculation fan (FIGS. 8a and 8b) by a load distribution circuit 109. This is the operation signal for the inlet damper.

As mentioned above, conventional plant automatic control devices are composed of multiple microcontrollers, and the risk of failure in the controller is distributed, but as can be seen from the figure, the control range of the master controller 31 is large. The master controller 31&llR is unable to control not only the power generation amount but also the main control variables such as main steam pressure, main steam temperature, and exhaust gas 021 total air flow rate, which has a large pumping effect on the system, so the master controller 31 is duplicated. There was a problem that it had to be done.

In addition, the controllers (lO) -ra 32 to 35 other than the master controller 31 are distributed for water supply, temperature, and air 2 ventilation, but the control range of these subloop controllers is large and a controller failure will affect the entire process. Therefore, these controllers also required redundancy such as duplication or N:1 backup.

The division of functions of the sub-loop controller is determined based on the control target. For example, in the case of main steam temperature control, the master controller 31 is responsible for the main steam temperature control, and the control operation amount is the fuel flow valve 6a, 6b. The SH spray valve 5 is within the range of the temperature controller 33. By the way, as shown in Fig. 2, the fuel flow valves 6a and 6b originally belong to the fuel process, and the SH spray valve 5 belongs to the steam process, based on the distributed configuration of plant system equipment units, but these can be classified according to the objects to be controlled. Therefore, there is a drawback that a failure of the temperature controller 33 affects two systems, the fuel process and the steam process.

In the case of exhaust gas 02 concentration control, the master controller 31 takes over the exhaust gas 02 concentration control, and the air control of each stage, which is the control operation amount, is performed by air amount controllers 34a to 34n provided for each burner stage. By the way, the burner lighting/extinguishing control, which is closely related to the air amount control of each burner stage, was assigned to another burner control device @23. This not only increases the number of signal exchanges between the burner controllers at each stage and the number of exchanges with the burner control device 23, but also has the drawback that the adjustment control between these controllers becomes extremely complicated.

As an example of the configuration of such a conventional system, see Hitachi Hyoron, VOL 65, Nn9 (1983-9) p.
, 603 to 608, page 605 shows an example of the system configuration, and page 606, FIG. 7 shows a basic control block diagram.

[Purpose of the invention]

As stated above, an object of the present invention is to realize a control method that has the least interconnection and is highly independent in accordance with the plant system in the control of a thermal power plant, thereby facilitating design and providing common parts. An object of the present invention is to provide a plant automatic control device that does not require multiplexing.

[Summary of the invention]

The feature of the present invention is that the control range of the master controller is limited to load control and main steam pressure control, and the system controller is provided to control main steam temperature, exhaust gas 02 control, and total air flow rate control, respectively, corresponding to the process system. to share in the
The master controller provides only boiler input commands to each system controller. A feature of this system is that each process system is independently controlled based on boiler input commands from a master controller. That is, the system has a configuration in which the coupling between the processes is loose and there is little mutual interference, which strengthens the durability of the entire system and eliminates the need for duplicating the remaster controller, making it possible to simplify control.

Furthermore, although the system controller issues commands to lower-level equipment controllers, the equipment controller can perform N:1 design within each system, allowing for standardization of design and simplification of design. The system controller only needs to issue commands to each device controller, and the system controller can concentrate on controlling the load distribution of each device, and the control method can be simplified.

[Embodiments of the invention]

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

FIG. 1 is a control block diagram of the automatic plant control system of the present invention. In the figure, 201 is a master controller, 202 is a steam process system controller, 203 is a fuel process system controller, 204 is a combustion process controller, and 205 is a ventilation process controller. These 201 to 205 are system level controllers. Further, 206 is a main turbine speed control controller, 20
7 is a feed water pump controller, 208 is a secondary SH spray controller, 209 is a primary SH spray controller, 210 is an M burner fuel flow controller, 211 is a P burner fuel flow controller, and 212 is an air controller for each burner stage. - A controller that performs gas flow rate control and burner control; 213 is a forced draft fan control controller; 214 is a gas recirculation control controller; These 206-214 are device controllers. Symbols 41 to 45 in the master controller 201 in FIG. 1 and
Items 47 to 50 are the same as in FIG. The function of this controller is the same as that shown in FIG. 3, so its explanation will be omitted. The output of the adder 50 is assigned to the boiler input command, which is the plant load command L from the central power supply station plus a correction signal due to the main steam pressure deviation, and is assigned to each system controller 202.
~205.

Next, in the steam process controller 202, 2
15 is a function generator, which is programmed to create a feed water flow rate command from the boiler input command LB, which is the output of the adding device 50. A216 is a subtracter, which converts the feed water flow rate 66 into the command value (the output of the function generator 215). ) and provide the deviation to the proportional-integral calculator 217. Proportional integral calculator 217
The output is the feed water pump flow rate command, and the load distribution control circuit 218 controls each feed water pump controller 207.
The output of the water pump 207 is distributed to the water supply pump turbine 4.
a, 4b, and water supply valve 309 are controlled. In this steam process controller 202, 219 is a function generator which receives a reboiler input command and programs a set value of the main steam temperature. 220 is a subtracter which compares the main steam temperature 52 with a set value (output of the function generator 219) and calculates the deviation from the proportional-integral calculator 221. give to 222 is for programming the set value of the outlet temperature of the second stage desuperheater 315 from the boiler input command Lll.

223 is an adder whose output is sent to the function generator 222 output as a correction signal from the main steam temperature deviation (proportional-integral calculator 22
1 output) is the outlet temperature setting signal of the second stage attemperator 315, which is given to the attemperator outlet temperature controller 208, and is sent to the second stage attemperator 315 via the spray valve 5 by the output of 208. Water injection amount is controlled.

In addition, in the same controller 202, 224 is a function generator which receives the boiler input command Lll from the secondary SH (Fig. 2 31).
4) Program the outlet temperature setting. 22
5 is the set value of the secondary SH outlet temperature (output of the function generator 224) based on the amount of correction of the outlet temperature of the second stage attemperator 315 (output of the proportional-integral calculator 221) due to the deviation of the main steam temperature.
The first stage spray 313 and the second stage spray 31 were modified.
This is a correction circuit that balances the 226 is secondary 5H
314, and the correction circuit 22 at the subtracter 227.
It is compared with the set value from 5 and the deviation is calculated by proportional integral calculator 2.
28. 229 is a function generator that programs the setting of the outlet temperature of the first stage attemperator 313 based on the boiler input command.

230 is an adder, which applies a correction signal (proportional integrator 228
(output) to create a setting for the first stage attemperator outlet temperature and provide it to the attemperator outlet temperature controller 209. The amount of water injected into the first stage attemperator 313 is controlled by the output of the pump 209 via the spray valve 5 .

In the fuel process control controller 203, 231
is a function generator that programs the fuel flow rate command from the boiler input command L5. 233 is the first stage desuperheater 313
This circuit corrects the constant spray control based on the amount of correction of the set value of the outlet temperature (output of the proportional-integral calculator 228). 234 is the M burner fuel valve 6b and the P burner fuel valve 6a.
This circuit distributes fuel commands. A subtractor 235 compares the fuel flow rate 73 of the M burner with the command value from the fuel distribution circuit 234, and further generates a control command to the fuel flow rate control controller 210 of the M burner by means of a proportional-integral calculator 236. Further, 237 is a subtracter which compares the P burner fuel flow rate 95 with the command value and generates a control command to the P burner fuel flow controller 211- by means of a proportional integral calculator 238.

In the combustion process controller 204, 239 is a function generator that programs a boiler input command and an air flow rate command. 240 is a function generator that programs the set value of the exhaust gas 02 concentration from the boiler input command LB;
241 is a subtracter which compares the exhaust gas O2 concentration 58 and the setting value from the function generator 240, inputs it to the proportional integral calculator 242, and corrects the air flow rate command value LA by the correction circuit 243 to obtain a corrected air flow rate command LAA. obtain. 244 is a subtracter that compares the total air flow rate 63 with the command value (18) and inputs it into a proportional integrator 245 to create an air flow rate correction value for each burner stage and send it to the air/gas flow rate control controller 212 for each burner stage. . By the output of 212, W/B inlet air damper 303M damper 304. Primary gas damper 3
05 are controlled respectively.

247 is a circuit which determines the optimum number and pattern of burners from the boiler input command and controls the number of burners in each stage. 248 is a circuit for preventing an imbalance between the amount of air and fuel when each burner is turned on and off.

In the ventilation process controller 205, 249 is a function generator that programs the set value of the outlet draft of the forced draft fan 7 from the boiler input command LI1. 250
is a subtractor and the outlet draft 100 of the forced draft fan 7
The set values are compared, a proportional-integral calculator 251 creates a command for the moving blades of the forced draft fan 7, and the command is given to the forced draft fan controller 213 via the load distribution circuit 252. Fans 7a and 7b are controlled by the output of 213. 253 is the gas recirculation fan 8 from the boiler input command LB
is a function generator that programs the exit draft settings of . 254 is a subtracter that compares the set value with the gas recirculation fan outlet draft 106, creates an opening command for the artificial damper of the gas recirculation fan 8 using the proportional integral calculator 255, and then outputs the gas recirculation fan 8 via the load distribution circuit 256. A command is given to the m-ring fan controller 214. Fans 8a and 8b are controlled by the output of 214.

The effects of this embodiment will be described below.

The scope of control of the master controller is limited to load control and main steam pressure control, and only boiler input commands are given to each system controller, and each system controller independently controls each system when given a boiler input command. This makes it possible to eliminate the need for a duplicated master controller.

The system controller receives boiler input commands from the master controller and concentrates on controlling the assigned system, making it possible to construct an independent control system for each system with less mutual interference with other systems. In addition, equipment controllers are distributed under each system controller and are responsible for direct control of the equipment, so the system controller only needs to give commands to the equipment controllers, resulting in a simple configuration that only controls the load distribution of each equipment. . Furthermore, independence of equipment control is ensured by the equipment controller, and there is no need to multiplex system controllers.

Since a plurality of identical devices exist in a system, the device controller can perform an N:1 design in which the design of one device can be applied to N devices, thereby realizing standardization and simplification of the design.

Air/gas flow rate control for each burner stage and burner control are combined into the same controller, which greatly reduces mutual signal exchange.

〔Effect of the invention〕

According to the present invention, in controlling a thermal power plant, it is possible to realize a control method that has the least mutual relationship with each system equipment unit of the plant and is highly independent.

That is, the master controller is in charge of load control and main steam pressure control, and gives only boiler input commands to each system controller. Each system controller performs independent control of the system based on boiler input commands, and performs load distribution control of equipment controllers provided below it. The equipment controller can be designed in an N:1 manner within each system, allowing standard design.

Therefore, it is possible to construct a highly reliable control system that is easy to design without making the master controller or system controller redundant.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, FIG. 2 shows the overall configuration of a thermal power plant, and FIG. 3 shows a conventional system. 201...Master controller, 202-205...
- System controller, 206-214...equipment controller.

Claims (1)

[Claims] 1. Thermal power generation that controls the turbine load using an external load request signal and outputs a boiler input command by correcting the load request signal using the boiler main steam pressure, and controls each part of the boiler using the boiler input command. In a plant, a main steam temperature controller that inputs the boiler input command and controls the boiler to bring the boiler main steam temperature to a predetermined value, and an exhaust gas controller that receives the boiler input command and controls the boiler to bring the boiler exhaust gas O_2 concentration to a predetermined value. An automatic control device for a thermal power plant, comprising: an O_2 concentration control controller; and a total air amount control controller that inputs a boiler input command and controls the boiler to make the boiler total air amount a predetermined value.