An automatic control system for a thermal power plant comprises a master controller controlling a turbine in response to an externally applied load command signal, and producing a boiler input command signal by correcting the load command signal on the basis of the detected pressure of main steam generated from a boiler, and a water/steam process controller, a fuel process controller, a combustion process controller and a draft process controller to all of which the boiler input command signal is applied from the master controller. The process controllers apply control signals to equipments controlling a water/steam process, a fuel process, a combustion process and a draft process respectively among the terminal actuating equipments of the various parts of the boiler.
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1. An automatic control system for a thermal power plant including a boiler, a turbine and power generator, comprising means for correcting a load command signal applied to the thermal power plant by comparing the load command signal with a feedback signal indicative of a detected pressure of main steam of the boiler thereby producing a boiler input command signal, and means including a plurality of function generators for generating setting signals of the flow rates of feed water, fuel and air respectively in response to the application of said boiler input command signal, so that the flow rates of feed water, fuel and air are feed-back controlled based on said setting signals.
6. An automatic control system for a thermal power plant, comprising a master controller controlling a turbine in response to an extenrally externally applied load command signal and producing a boiler input command signal by correcting said load command signal on the basis of the detected pressure of main steam generated from a boiler so as to control various parts of the boiler by said boiler input command signal, a water/steam process controller applying, in response to the application of said boiler input command signal, control signals to equipments controlling a water/steam process among terminal actuating equipments of various parts of the boiler, a fuel process controller applying, in response to the application of said boiler input command signal, control signals to equipments controlling a fuel process among the terminal actuating equipments of various parts of the boiler, a combustion process controller applying, in response to the application of said boiler input command signal, control signals to equipments controlling a combustion process among the terminal actuating equipments of various parts of the boiler, and a draft process controller applying, in response to the application of said boiler input command signal, control signals to equipments controlling a draft process among the terminal actuating equipments of various parts of the boiler.
7. An automatic control system for an electric power plant comprising:
a master controller responsive to an external load command signal for producing a first command signal indicative of an amount of electric power to be generated by the power plant; a plurality of subsystems providing individual flows of materials for executing respective processes relating to generation of the electric power by controlling the flows of materials, respectively; subsystem controllers coupled to the subsystems, respectively, each of said subsystem controllers being solely responsive to said first command signal for determining definitely a second command signal indicative of a set value of given variable of the process executed by the associated subsystem for generating the electric power indicated by said first command signal; means coupled to each of said subsystem controllers and responsive to the second command signal predetermined definitely by the associated subsystem controller for producing a third command signal for controlling the flow of material in the associated subsystem so that the given variable of the process executed by the associated subsystem assumes the set value indicated by the second command signal; and means responsive to the third command signal for controlling the flow of material in the associated subsystem based on the third command signal.
3. An automatic control system for a thermal power plant including a boiler, a turbine and a power generator, comprising means for correcting a load command signal applied to the thermal power plant by comparing the load command signal with a feedback signal indicative of a detected pressure of main steam of the boiler thereby producing a boiler input command signal, means including function generators for generating setting signals of the flow rates of feed water and main steam temperature respectively for the purpose of controlling steam produced by the boiler in response to the application of said boiler input command signal, means including a function generator for generating a setting signal of the flow rate of fuel for controlling a fuel supplied to the boiler in response to the application of said boiler input command signal, means including a function generator for generating a setting signal for a total flow rate of air for controlling fuel combustion in the boiler in response to the application of said boiler input command signal, and means including a function generator for generating a setting signal of the flow rate of draft at the outlets of forced draft fans for controlling a draft process of the boiler in response to the application of said boiler input command signal, so that individual terminal actuating equipments can be controlled on the basis of said setting signals.
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8. An automatic control system as claimed in
a master controller responsive to an external load command signal for producing a first command signal indicative of an amount of electric power to be generated by the power plant; subsystem controllers coupled to a plurality of subsystems providing individual flows of materials for executing respective processes relating to generation of the electric power by controlling the flows of materials, respectively, each of said subsystem controllers being solely responsive to said first command signal for predetermined definitely a second command signal indicative of a target value of given variable of the process executed by the associated subsystem for generating the electric power indicated by said first command signal; and means coupled to each of said subsystem controllers and responsive to said second command signal determined definitely by the associated subsystem controller for controlling the flow of material in the associated subsystem so that the given variable of the process executed by the associated subsystem assumes the target value indicated by said second command signal. 10. An automatic control system as claimed in claim 9, wherein each of said subsystem controllers includes a function generator having a preset program solely responsive to said first command signal for determining definitely the second command signal as an output thereof. 11. An automatic control system for an electric power plant comprising: a master controller responsive to an external load command signal for producing a main command signal indicative of an amount of electric power to be generated by the power plant; subsystem controllers coupled to a plurality of subsystems providing individual flows of at least fuel, air and water for executing respective processes relating to generation of the electric power by controlling the flows of the fuel, air and water, respectively, and solely responsive to said main command signal for determining definitely a fuel command, air command and water command, respectively, indicative of target values relating to the flows of the fuel, air and water to enable the subsystems to execute the respective processes for generating the electric power indicated by said main command signal; and means coupled to said subsystem controllers and responsive to the fuel command, the air command and the water command, respectively, determined definitely by said respective subsystem controllers for controlling the respective flows of the fuel, air and water in execution of the processes by the subsystems so that the respective flows in the subsystems assume the target values indicated by the respective commands. 12. An automatic control system as claimed in claim 11, wherein said respective subsystem controllers each include a function generator having a preset program responsive solely to said main command signal for determining definitely the respective command. 13. An automatic control system of an electric power plant for generating electric power according to a main command signal externally applied thereto, said system comprising: a plurality of driving means coupled to a plurality of subsystems, providing flows of different materials, respectively, which cooperate with each other for controlling generation of the electric power by said power plant, each of said plurality of driving means controllably driving a flow of material in the associated subsystem; and plurality of driving means controllers coupled to said subsystems, respectively, each of said controllers being responsive to the main command signal and independent of signals applied to others of said subsystem controllers for providing a non-intermediate output signal solely controlling said driving means in the associated subsystem thereby controlling the generation of the electric power according to the main
command signal. 14. An automatic control system as claimed in claim 13, wherein each of said subsystem controllers being responsive to the main command signal includes a function generator having a preset program solely responsive to the main command signal for providing the non-intermediate output signal for controlling said driving means in the associated subsystem. 15. An automatic control system for an electric power plant comprising: means responsive to an externally applied load command for producing a main command signal indicative of an amount of electric power to be generated by said power plant; and subsystem controllers coupled to subsystems providing flows of different materials relating to generation of electric power, said flows of different materials cooperating with each other for generating electric power by said power plant, respectively, each of said controllers including first means solely responsive to the main command signal for determining definitely a target signal indicative of a target value relating to the flow of the material solely in the associated subsystem according to the main command signal and second means for controlling the flow of the material in the associated subsystem according to the target signal determined definitely by said first means. 16. An automatic control system as claimed in claim 15, wherein said first means includes a function generator having a preset program responsive solely to the main command signal for providing the target signal determined definitely. 17. An automatic control system of an electric power plant for generating electric power according to a main command signal externally applied thereto, said system comprising: a plurality of driving means coupled to a plurality of subsystems providing flows of different materials, respectively, which cooperate with each other for controlling generation of the electric power by said power plant each of said plurality of driving means controllably driving the flow of material in the associated subsystem; and a plurality of subsystem controllers coupled to said plurality of driving means, respectively, a respective one of said plurality of subsystem controllers being responsive to the main command signal and independent of signals applied to others of said subsystem controllers for providing a non-intermediate output signal controlling said driving means in the associated subsystem without controlling said driving means associated with another one of said subsystem controllers, thereby controlling the generation of the electric power according to the main command signal. 18. An automatic control system of an electric power plant for generating electric power according to a main command signal externally applied thereto, said system comprising: a plurality of driving means coupled to a plurality of subsystems, respectively, each for controllably driving a flow of material in the associated subsystem; and a plurality of subsystem controllers coupled to said plurality of driving means, respectively, a respective one of said plurality of subsystem controllers being responsive to the main command signal for providing a non-intermediate output signal controlling said driving means in the associated subsystem without controlling said driving means associated with another one of said subsystem controllers, thereby controlling a parameter according to the main command signal; wherein at least one of said plurality of subsystem controllers provides an intermediate output signal for controlling another one of said plurality of subsystem controllers. 19. An automatic control system of an electric power plant for generating electric power according to a main command signal externally applied thereto, said system comprising: a plurality of driving means coupled to a plurality of subsystems, respectively, each for controllably driving a flow of material in the associated subsystem; and subsystem controllers coupled to said plurality of driving means, respectively, each of said subsystem controllers being responsive to the main command signal for providing a non-intermediate output signal solely controlling said driving means in the associated subsystem thereby controlling a parameter according to the main command signal; wherein at least one of said plurality of subsystem controllers provides an intermediate output signal for controlling another one of said plurality of subsystem controllers. |
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produoe produce a fuel flow-rate command signal LF as a function of the boiler input command signal LB, as shown in FIG. 3d. The output signal of the proportional plus integral circuit 228, indicative of the amount of correction of the setting of the outlet temperature of the first-stage desuperheater 313, is as shown in dashed line, may be optionally applied together with the output signal of the function generator 231 to a correction circuit 233 which corrects the fuel flow-rate command signal LF on the basis of the output signal of the proportional plus integral circuit 228 for the purpose of constant spray control. A fuel distribution circuit 234 distributes the fuel flow-rate command signal LF to the fuel valve 6b for the main burners M and to the fuel valve 6a for the planet burners P. A signal 73 indicative of the detected flow rate of fuel supplied to the main burners M is compared in a subtractor 235 with the command signal applied from the fuel distribution circuit 234, and the resultant signal is applied to a proportional plus integral circuit 236 which produces a command signal applied to the main-burner fuel flow-rate controller 210. Also, a signal 75 indicative of the detected flow rate of fuel supplied to the planet burners P is compared in a subtractor 237 with the command signal applied from the fuel distribution circuit 234, and the resultant signal is applied to a proportional plus integral circuit 238 which produces a command signal applied to the planet-burner fuel flow-rate controller 211.
The fuel process controller 204 includes a seventh function generator 239 which is programmed to produce an air flow-rate command signal LA as a function of the boiler input command signal LB, as shown in FIG. 3e. An eighth function generator 240 is programmed to produce a signal for setting the concentration of O2 in exhaust gases as a function of the boiler input command signal LB, as shown in FIG. 3f. A signal 58 indicative of the detected O2 concentration is compared in a subtractor 241 with the setting applied from the function generator 240, and the resultant signal is applied to a proportional plus integral circuit 242. The output signal of the proportional plus integral circuit 242 is applied together with the air flow-rate command signal LA from the function generator 239 to a correction circuit 243. In the correction circuit 243, the air flow-rate command signal LA is corrected to provide a corrected air flow-rate command signal LAA. A signal 63 indicative of the detected total flow rate of air is compared in a subtractor 244 with the setting signal applied from the correction circuit 243, and the resultant signal is applied to a proportional plus integral circuit 245 to appear as a signal indicative of the corrected flow rate of air to be supplied to each of the burner stages. Such a command signal is applied to each of the air and gas flow-rate controllers 212a to 212n. The output signals of the controllers 212a to 212n control the window-box inlet air dampers 303, GM dampers 304 and primary gas dampers 305 respectively. On the basis of the boiler input command signal LB, a circuit 247 determines the optimum number of burners and the optimum pattern for each of the burner stages. An advanced control circuit 248 prevents an unbalance between the flow rates of air and fuel at the time of ignition and extinction of the burners.
In the draft process controller 205, a ninth function generator 249 is programmed to produce a signal for setting the flow rate of draft at the outlets of the forced draft fans (FDF) 7a and 7b as a function of the boiler input command signal LB, as shown in FIG. 3g. A signal 100 indicative of the detected flow rate of draft at the outlets of the forced draft fans 7a and 7b is compared in a subtractor 250 with the setting signal applied from the function generator 249, and the resultant signal is applied to a proportional plus integral circuit 251. The proportional plus integral circuit 251 produces a command signal commanding the angular position of the rotor blades of the forced draft fans 7a and 7b, and this command signal is applied to the forced draft fan controllers 213a and 213b through a load distribution circuit 252, thereby controlling the forced draft fans 7a and 7b. A tenth function generator 253 is programmed to produce a signal for setting the flow rate of draft at the outlets of gas recirculating fans (GRF) 8a and 8b as a function of the boiler input command signal LB, as shown in FIG. 3h A signal 106 indicative of the detected flow rate of draft at the outlets of the gas recirculating fans 8a and 8b is compared in a subtractor 254 with the setting signal applied from the function generator 253, and the resultant signal is applied to a proportional plus integral circuit 255. The proportional plus integral circuit 255 produces a command signal commanding the opening of the inlet dampers of the gas recirculating fans 8a and 8b, and this command signal is applied to the gas recirculating fan controllers 214a and 214b through a load distribution circuit 256, thereby controlling the gas recirculating fans 8a and 8b.
The advantages of the plant control system embodying the present invention will now be described.
Objects to be controlled by the master controller 201 are limited to the load and the pressure of main steam, and the boiler input command signal LB only is applied from the master controller 201 to the process controllers 202 to 205. The process controllers 202 to 205 can simultaneously set the controlled parameters for the associated equipments in response to the application of the boiler input command signal LB. Thus, the characteristics in response of the system are improved as compared with the prior system in which the various parameters are set successively upon receiving the load command signal. Further, for that reasons, the correction control of a parameter of a certain processor relative to the other processor is almost unnecessary, resulting in improved stability in operation of the system.
The equipment controllers belonging to some of the process controllers control a plurality of same equipments. Therefore, the so-called N:1 design, where design of one controller is applicable to N controllers, can be realized to standardize and simplify the design.
Further, the control of the flow rates of air and gas and the control of the burner in each burner stage of the boiler can be attained by one and the same controller, thereby greatly decreasing the number of required signal lines.
It will be understood from the foregoing detailed description of the present invention that unit processes and unit equipments in a thermal power plant can be independently controlled with least mutual interference therebetween.
According to the present invention, the master controller participates in the control of the load and the control of the pressure of main steam, and a boiler input command signal only is applied from the master controller to the process controllers. In response to the application of the boiler input command signal, the process controllers control the associated processes independently of one another and control also the load distribution to their subordinate equipment controllers. The so-called N:1 design of the equipment controllers belonging to some of the process controllers can be realized to permit standardization of the design. Therefore, the present invention provides a plant control system which can operate with high reliability and can be easily designed without redundancy of the master and process controllers.
Sugano, Akira, Yamanobe, Sachio
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| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Dec 04 1991 | Hitachi, Ltd. | (assignment on the face of the patent) | / | |||
| Dec 04 1991 | Hitachi Engineering Co., Ltd. | (assignment on the face of the patent) | / |
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