CN111878796A - Supercritical once-through boiler unit intermediate point temperature four-quadrant control method and control loop thereof - Google Patents
Supercritical once-through boiler unit intermediate point temperature four-quadrant control method and control loop thereof Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B35/00—Control systems for steam boilers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B37/00—Component parts or details of steam boilers
- F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
- F22B37/38—Determining or indicating operating conditions in steam boilers, e.g. monitoring direction or rate of water flow through water tubes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B37/00—Component parts or details of steam boilers
- F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
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Abstract
The invention relates to a supercritical once-through boiler unit intermediate point temperature four-quadrant control method, which takes the difference delta P between the main steam pressure and the pressure set value as a horizontal coordinate, and the difference delta T between the intermediate point temperature and the temperature set value as a vertical coordinate to establish a four-quadrant coordinate system, and preferentially reduces the fuel quantity corrected value when the delta T and the delta P are both positive; when the delta T is positive and the delta P is negative, the feed water flow correction value is preferentially increased; when both delta T and delta P are negative, preferentially increasing the fuel quantity correction value; when Δ T is negative and Δ P is positive, the feed water flow correction value is preferentially decreased. The control method adopted by the invention can ensure that the fluctuation range of main steam pressure is small and the fluctuation of operation parameters such as water supply flow, coal supply quantity and the like is small while ensuring that the intermediate point temperature meets the operation requirement of the unit.
Description
Technical Field
The invention relates to the technical field of boiler unit intermediate point temperature control, in particular to a supercritical once-through boiler unit intermediate point temperature four-quadrant control method and a supercritical once-through boiler unit intermediate point temperature four-quadrant control loop.
Background
The intermediate point temperature control scheme of the existing supercritical unit adopts a PID control loop, the intermediate point temperature is set in a CRT operation picture or the intermediate point temperature set value is given by the heat load of a boiler through conversion, and then a corresponding feed water flow correction value and a corresponding coal feeding amount correction value are output through the PID control loop, the two correction values respectively act in a feed water flow instruction loop and a fuel amount instruction loop, so that the intermediate point temperature is corrected in real time, wherein the intermediate point temperature control loop is shown as a figure 1, and in the figure:
SP-T, midpoint temperature set point;
PV-T, mid-point temperature feedback values (001, 002 represent the serial number of the input quantity);
SUB, a subtraction function module;
PID, proportional-integral-derivative controller;
f (X), a broken line function module, wherein subscript numbers are a plurality of broken line functions;
FW, the output value of the control loop is a water supply correction value;
CW, the control loop output value is a fuel quantity correction value;
FW-X, the corrected value of the water supply amount becomes the input amount of the next control loop;
CW-X, the fuel quantity correction value will be the input quantity for the next control loop.
Function F in FIG. 11(X) and F2The direction of action of (X) is reversed, and in the case where the intermediate point temperature set value is lower than the actual value, the feed water flow correction value output is positive and the fuel quantity correction value output is negative, and vice versa.
Because the prior art scheme only determines the final correction value of the water supply quantity and the fuel quantity according to the deviation between the intermediate point temperature and the set value, the factors such as the main steam pressure of a unit, the calorific value of coal as fired and the like are not considered dynamically and globally, and the following conditions are generated:
under the condition that the actual value of the middle point temperature and the main steam pressure are higher than the set values, the loop of the prior control technology increases the correction value of the water supply flow, the fuel instruction correction value is reduced, the action of water on the main steam pressure is faster than the fuel quantity, so that the main steam pressure is increased rapidly, the main control of a boiler reduces the fuel quantity due to the increase of the main steam pressure, the system tends to be in an unstable state, and the safe operation of a unit is influenced;
when the actual value of the middle point temperature and the main steam pressure are both lower than the set values, the corrected value of the water supply flow is reduced, the corrected value of the fuel quantity is increased, the main steam pressure is accelerated to be higher than the set value of the main steam pressure due to the fact that the fuel has a slower effect on the main steam pressure, and the main steam pressure deviates from the set value of the pressure, and is slowly increased after being adjusted for a long time, so that the main control system of the boiler is greatly adjusted and the parameters are severely fluctuated;
when the actual value of the middle point temperature is lower than the set value and the main steam pressure is higher than the set value, the corrected value of the water supply flow is reduced, the corrected value of the fuel quantity is increased, the main steam pressure and the middle point temperature tend to the temperature in a period of time, so that the control is realized, but the main steam pressure and the middle point temperature are rapidly increased after the transient stable state due to the increase of the fuel quantity and the reduction of the water quantity, so that the conditions of large-amplitude adjustment and severe parameter fluctuation of the coordinated control system occur;
when the actual value of the middle point temperature is higher than the set value and the main steam pressure is lower than the pressure set value, the corrected value of the water supply flow is increased, the corrected value of the fuel quantity is reduced, and the main steam pressure cannot be compensated by the heat load of the boiler due to the reduction of the fuel quantity, so that the reduction range of the main steam pressure is increased, and the large adjustment of the main control of the boiler and the severe fluctuation of parameters are caused;
and fifthly, when the intermediate temperature is adjusted, the intermediate temperature is coupled with the control of the main steam pressure, so that the main steam pressure deviates from the specified range of the set value, the coordinated control system is triggered to perform reverse compensation on the main steam pressure, the power generation load of the unit is lost, the AGC (automatic gain control) performance of the unit is reduced, and the comprehensive economic benefit of two detailed rules is influenced.
Therefore, the existing control technology produces more side effects when controlling the temperature of the intermediate point, and does not utilize the safe, stable and economic operation of the unit.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a supercritical once-through boiler unit intermediate point temperature four-quadrant control method and a control loop thereof, which realize the function of stabilizing unit operation parameters such as intermediate point temperature, main steam pressure, water supply flow, coal supply quantity and the like. The working strength of operators is reduced, and the safe and economic operation level of the unit is improved.
The technical scheme adopted by the invention for solving the technical problems is as follows: the supercritical once-through boiler unit intermediate point temperature four-quadrant control method is characterized in that a four-quadrant coordinate system is established by taking the difference delta P between main steam pressure and a pressure set value thereof as an abscissa and taking the difference delta T between intermediate point temperature and a temperature set value thereof as an ordinate, and the intermediate point temperature control method is as follows:
when both delta T and delta P are positive, the engine is located in a first quadrant, the actual values of the intermediate point temperature and the main steam pressure are higher than the corresponding set values, and the fuel quantity correction value is preferentially reduced;
when the delta T is positive and the delta P is negative, the steam turbine is located in a second quadrant, the actual value of the temperature of the middle point is higher than the set value of the temperature, the actual value of the main steam pressure is lower than the set value of the main steam pressure, and the corrected value of the water supply flow is preferentially increased;
when both delta T and delta P are negative, the fuel quantity correction value is preferentially increased when the fuel quantity correction value is located in the third quadrant, the actual values of the intermediate point temperature and the main steam pressure are lower than the corresponding set values;
when the delta T is negative and the delta P is positive, the steam turbine is located in the fourth quadrant, the actual value of the intermediate point temperature is lower than the set value, the actual value of the main steam pressure is higher than the set value, and the corrected value of the water supply flow is preferentially reduced.
The invention also provides a control loop applying the supercritical once-through boiler unit intermediate point temperature four-quadrant control method, which comprises a four-quadrant PID control loop, wherein the four-quadrant PID control loop comprises an intermediate point temperature water supply correction PID control loop, a fire coal correction PID control loop and a data processing module, and the data processing module is respectively connected with the intermediate point temperature water supply correction PID control loop and the fire coal correction PID control loop.
In a preferred embodiment of the control loop provided by the present invention, the intermediate point temperature feedwater correction PID control loop comprises a subtraction function module i for receiving an intermediate point temperature set value and a feedback value, a selection output function module i with a dead zone, a PID controller i, and an addition function module i, which are connected in sequence;
the coal-fired correction PID control loop comprises a subtraction function module II for receiving a set value and a feedback value of the intermediate point temperature, a selection output function module II with a dead zone, a PID controller II and an addition function module II which are connected in sequence;
the data processing module comprises a feedforward signal control loop, a fold line function module I, an analog signal generator, a subtraction function module III, a first data processing module and a second data processing module, wherein the signal input end of the fold line function module I is connected with the feedforward signal control loop and the analog signal generator, the signal output ends of the fold line function module I are respectively connected with the first data processing module and the subtraction function module III, the signal input end of the first data processing module is connected with the signal output end of the PID controller I, the signal output end of the first data processing module is connected with the signal input end of the addition function module I, the signal output end of the subtraction function module III is connected with the signal input end of the second data processing module, the signal input end of the second data processing module is connected with the signal output end of the PID controller II, and the signal output end of the second data processing module is connected with the signal input end of the, and the first addition function module and the second addition function module respectively output a water supply quantity correction value and a fuel quantity correction value.
In a preferred embodiment of the control loop provided by the present invention, the first data processing module includes a first multiplication function module, a first high-low limit monitoring module, and a first rate function module, which are connected in sequence;
the second data processing module comprises a multiplication function module II, a high-low limit monitoring module II and a rate function module II which are connected in sequence.
In a preferred embodiment of the control loop provided in the present invention, the feedforward signal control loop comprises a quadrant feedforward signal control loop, and a quadrant feedforward signal control loop, wherein:
the first quadrant feedforward signal control loop comprises a second fold line function module, a third multiplication function module, a fourth subtraction function module, a third fold line function module, a fourth multiplication function module, a fifth subtraction function module and a selection loop function module, wherein the second fold line function module receives signals of the first subtraction function module or the second subtraction function module; the second broken line function module is connected with the third multiplication function module; the fourth subtraction function module, the third fold line function module and the fourth multiplication function module are sequentially connected; the third multiplication function module and the fourth multiplication function module are respectively connected with the input end of the fifth subtraction function module, and the output end of the fifth subtraction function module is connected with the selection loop function module;
the structures of the two-quadrant feedforward signal control loop, the three-quadrant feedforward signal control loop and the four-quadrant feedforward signal control loop are the same as the structure of the one-quadrant feedforward signal control loop.
In a preferred embodiment of the control loop provided by the present invention, the control loop further includes a third addition function module, an input end of the third addition function module is respectively connected to the signal output ends of the selection loop function modules of the first quadrant feedforward signal control loop, the second quadrant feedforward signal control loop, the third quadrant feedforward signal control loop and the fourth quadrant feedforward signal control loop, and a signal input end of the third addition function module is connected to the first polygonal line function module.
In a preferred embodiment of the control loop provided in the present invention, the selection loop function module of the one-quadrant feedforward signal control loop, the two-quadrant feedforward signal control loop, the three-quadrant feedforward signal control loop and the four-quadrant feedforward signal control loop is correspondingly connected to the one-quadrant feedforward enable signal control loop, the two-quadrant feedforward enable signal control loop, the three-quadrant feedforward enable signal control loop and the four-quadrant feedforward enable signal control loop, wherein:
the first quadrant feedforward enabling signal control loop comprises a first high-value signal selection module for receiving signals of a first subtraction function module or a second subtraction function module and a second high-value signal selection module for receiving signals of a fourth subtraction function module, the first high-value signal selection module and the second high-value signal selection module are both connected with a first switching value and operation function module, and the first switching value and operation function module is connected with a selection loop function module of the first quadrant feedforward signal control loop;
the two-quadrant feedforward enabling signal control loop comprises a high-value signal selection module III for receiving signals of a subtraction function module I or a subtraction function module II and a low-value signal selection module I for receiving signals of a subtraction function module IV, the high-value signal selection module III and the low-value signal selection module I are both connected with a switching value and operation function module II, and the switching value and operation function module II is connected with a selection loop function module of the two-quadrant feedforward signal control loop;
the three-quadrant feedforward enabling signal control loop comprises a second low-value signal selection module for receiving signals of the first subtraction function module or the second subtraction function module and a third low-value signal selection module for receiving signals of the fourth subtraction function module, the second low-value signal selection module and the third low-value signal selection module are both connected with a third switching value and operation function module, and the third switching value and operation function module is connected with a selection loop function module of the three-quadrant feedforward signal control loop;
the four-quadrant feedforward enabling signal control loop comprises a low-value signal selection module IV for receiving signals of the first subtraction function module or the second subtraction function module and a high-value signal selection module IV for receiving signals of the fourth subtraction function module, the low-value signal selection module IV and the high-value signal selection module IV are both connected with a switching value and operation function module IV, and the switching value and operation function module IV is connected with a selection loop function module of the four-quadrant feedforward signal control loop.
Compared with the prior art, the supercritical once-through boiler unit intermediate point temperature four-quadrant control method and the control loop thereof have the beneficial effects that: the control method adopted by the invention can ensure that the fluctuation range of main steam pressure is small and the fluctuation of operation parameters such as water supply flow, coal supply quantity and the like is small while ensuring that the intermediate point temperature meets the operation requirement of the unit; the temperature of the main steam is stable after the intermediate point temperature control effect is improved, the phenomenon of overtemperature of the heating surface is obviously reduced, pipe explosion is hardly caused, and the economic loss of a power plant is greatly reduced; after the control method is adopted, the interference to other related control systems is small.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without inventive efforts, wherein:
FIG. 1 is a SAMA diagram of a conventional intermediate point temperature control loop provided by the present invention;
FIG. 2 is a schematic diagram of a four-quadrant control method for mid-point temperature provided by the present invention;
FIG. 3 is a SAMA diagram of the four quadrant PID control loop provided by the present invention;
FIG. 4 is a SAMA diagram of the one-quadrant feedforward signal control loop provided by the present invention;
FIG. 5 is a SAMA diagram of the two-quadrant feedforward signal control loop provided by the present invention;
FIG. 6 is a SAMA diagram of the three quadrant feedforward signal control loop provided by the present invention;
FIG. 7 is a SAMA diagram of the four quadrant feedforward signal control loop provided by the present invention;
FIG. 8 is a SAMA diagram of the feed forward signal control loop provided by the present invention;
FIG. 9 is a SAMA diagram of the one-quadrant feedforward enable signal control loop provided by the present invention;
FIG. 10 is a SAMA diagram of the two-quadrant feedforward enable signal control loop provided by the present invention;
FIG. 11 is a SAMA diagram of the three quadrant feedforward enable signal control loop provided by the present invention;
FIG. 12 is a SAMA diagram of the four quadrant feedforward enable signal control loop provided by the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 2, the present invention provides a four-quadrant control method for the middle point temperature of a supercritical once-through boiler, which uses the difference Δ P between the main steam pressure and the pressure set value thereof as the abscissa and the difference Δ T between the middle point temperature and the temperature set value thereof as the ordinate to establish a four-quadrant coordinate system, wherein the middle point temperature control method is as follows:
when both delta T and delta P are positive, the engine is located in a first quadrant, the actual values of the intermediate point temperature and the main steam pressure are higher than the corresponding set values, and the fuel quantity correction value is preferentially reduced;
when the delta T is positive and the delta P is negative, the steam turbine is located in a second quadrant, the actual value of the temperature of the middle point is higher than the set value of the temperature, the actual value of the main steam pressure is lower than the set value of the main steam pressure, and the corrected value of the water supply flow is preferentially increased;
when both delta T and delta P are negative, the fuel quantity correction value is preferentially increased when the fuel quantity correction value is located in the third quadrant, the actual values of the intermediate point temperature and the main steam pressure are lower than the corresponding set values;
when the delta T is negative and the delta P is positive, the steam turbine is located in the fourth quadrant, the actual value of the intermediate point temperature is lower than the set value, the actual value of the main steam pressure is higher than the set value, and the corrected value of the water supply flow is preferentially reduced.
Referring to fig. 3 to 12, the present invention further provides a control loop capable of performing intermediate point temperature control by using the above control method.
As shown in fig. 3, the control loop of this embodiment includes a four-quadrant PID control loop, the four-quadrant PID control loop includes a middle point temperature water supply correction PID control loop 1, a coal combustion correction PID control loop 2, and a data processing module 3, and the data processing module 3 is respectively connected to the middle point temperature water supply correction PID control loop 1 and the coal combustion correction PID control loop 2.
The intermediate point temperature water supply correction PID control loop 1 comprises a subtraction function module I101, a selection output function module I102 with a dead zone, a PID controller I103 and an addition function module I104 which are sequentially connected and used for receiving an intermediate point temperature set value and a feedback value; in this embodiment, the first subtraction function module 101 calculates a set value of the intermediate point temperature and a feedback value to obtain a difference value, i.e., Δ T, and the first selection output function module 102 with the dead zone outputs 0 when the input quantity is within the dead zone range, and directly outputs the input quantity to the first PID controller 103 when the input quantity is greater than the dead zone value.
The coal-fired correction PID control loop 2 comprises a subtraction function module II 201 for receiving a set value and a feedback value of the intermediate point temperature, a selection output function module II 202 with a dead zone, a PID controller II 203 and an addition function module II 204 which are connected in sequence; in the same way, the subtraction function module two 201 of this embodiment obtains the difference between the intermediate point temperature setting value and the feedback value, that is: and delta T, the second selection output functional module 202 with the dead zone outputs 0 when the input quantity is in the dead zone range, and directly outputs the input quantity to the second PID controller 203 when the input quantity is greater than the dead zone value.
The data processing module 3 includes a feedforward signal control loop 4, a first polygonal line function module 301, an analog signal generator 302, a third subtraction function module 303, a first data processing module 304 and a second data processing module 305, a signal input end of the first polygonal line function module 301 is connected to the feedforward signal control loop 4 and the analog signal generator 302, and signal output ends thereof are respectively connected to the first data processing module 304 and the third subtraction function module 303, in this embodiment, the feedforward signal control loop 4 provides a feedforward coefficient, a variable is input through the analog signal generator 302, the polygonal line function module 301 processes the variable, and respectively outputs a signal to the first data processing module 304 and the third subtraction function module 303, the third subtraction function module 303 calculates a difference value with a set value, a signal input end of the first data processing module 304 is connected to a signal output end of the first PID controller 103, the signal output end of the first adding function module 104 is connected with the signal input end of the first PID controller 103 of the PID control loop 1 for correcting the intermediate point temperature water supply, the output signal and the feedforward signal of the PID controller are processed by the first data processing module 304 and then processed by the first adding function module 104 to output the water supply correction value, the signal output terminal of the subtraction functional module three 303 is connected to the signal input terminal of the second data processing module 305, a signal input terminal of the second data processing module 305 is connected to a signal output terminal of the second PID controller 203, the signal output end of the second addition function module 204 is connected to the signal input end of the second PID controller 203 of the fire coal correction PID control loop 2 of the present embodiment, and the output signal and the processed feedforward signal of the second PID controller of the fire coal correction PID control loop 2 are processed by the second data processing module 305 and then processed by the second addition function module 204 to output the fuel quantity correction value.
Preferably, the first data processing module 304 of the present embodiment includes a first multiplication function module 3041, a first high-low limit monitoring module 3042, and a first rate function module 3043, which are connected in sequence;
the second data processing module 305 comprises a second multiplication function module 3051, a second high-limit and low-limit monitoring module 3052 and a second rate function module 3053 which are connected in sequence.
The multiplication function module of this embodiment is: the two input values are multiplied, and the high-limit monitoring module and the low-limit monitoring module are as follows: when the input value is within the upper limit and the lower limit, the output value is equal to the input value, when the input value is greater than the upper limit, the output value is equal to the upper limit, when the input value is less than the lower limit, the output value is equal to the lower limit, and the speed function module is as follows: the output value is equal to the value at which the input value changes at a rate.
Preferably, referring to fig. 4 to 7, the feedforward signal control loop 4 of the present embodiment includes a quadrant feedforward signal control loop 401, a quadrant feedforward signal control loop 402, a quadrant feedforward signal control loop 403, and a quadrant feedforward signal control loop 404, wherein:
the one-quadrant feedforward signal control loop 401 comprises a second polygonal line function module 4011 for receiving signals of the first subtraction function module 101 or the second subtraction function module 102, a third multiplication function module 4012, a fourth subtraction function module 4013 for receiving a set value and a feedback value of the main steam pressure, a third polygonal line function module 4014, a fourth multiplication function module 4015, a fifth subtraction function module 4016 and a selection loop function module 4017; the second broken line function module 4011 is connected with the third multiplication function module 4012; the fourth subtraction function module 4013, the third broken line function module 4014 and the fourth multiplication function module 4015 are sequentially connected; the multiplication function module III 4012 and the multiplication function module IV 4015 are respectively connected with the input end of the subtraction function module V4016, and the output end of the subtraction function module V4016 is connected with the selection loop function module 4017.
In the one-quadrant feedforward signal control loop of the embodiment, Δ T and Δ P are respectively used as signal inputs of the second polygonal line function module 4011 and the third polygonal line function module 4014, and are respectively processed through the third multiplication function module 4012 and the fourth multiplication function module 4015, so that the signal is multiplied by a logic setting coefficient K to be output, and then the signal is processed by the fifth subtraction function module 4016 and the selection loop function module 4017 to output a one-quadrant feedforward signal.
Specifically, the structures of the two-quadrant feedforward signal control loop, the three-quadrant feedforward signal control loop and the four-quadrant feedforward signal control loop of the present embodiment are the same as those of the one-quadrant feedforward signal control loop, and the signal output principle is the same.
As shown in fig. 4 to 7, the selection loop function module 4017 of this embodiment outputs a value equal to Y when the enable terminal is 1, and outputs a value equal to N when the enable terminal is 0.
The feedforward signal control loop 4 of this embodiment further includes an addition function module three 405, an input end of the addition function module three 405 is respectively connected to signal output ends of selection loop function modules of the first quadrant feedforward signal control loop 401, the second quadrant feedforward signal control loop 402, the third quadrant feedforward signal control loop 403, and the fourth quadrant feedforward signal control loop 404, and a signal input end of the addition function module three 405 is connected to the first polygonal line function module 301.
The selection loop function modules of the one-quadrant feedforward signal control loop 401, the two-quadrant feedforward signal control loop 402, the three-quadrant feedforward signal control loop 403 and the four-quadrant feedforward signal control loop 404 are correspondingly connected with a one-quadrant feedforward enabling signal control loop 501, a two-quadrant feedforward enabling signal control loop 502, a three-quadrant feedforward enabling signal control loop 503 and a four-quadrant feedforward enabling signal control loop 504, wherein:
the one-quadrant feedforward enabling signal control loop 501 comprises a first high-value signal selection module 5011 for receiving a signal of the first subtraction function module 101 or a second subtraction function module 201 and a second high-value signal selection module 5012 for receiving a signal of the fourth subtraction function module 4013, wherein the first high-value signal selection module 5011 and the second high-value signal selection module 5012 are both connected with a first switching value and operation function module 5013, and the first switching value and operation function module 5013 is connected with a selection loop function module of the one-quadrant feedforward signal control loop 401;
the two-quadrant feedforward enable signal control loop 502 comprises a high-value signal selection module III 5021 for receiving signals of the first subtraction function module 101 or the second subtraction function module 201 and a low-value signal selection module I5022 for receiving signals of the fourth subtraction function module 4013, the high-value signal selection module III 5021 and the low-value signal selection module I5022 are both connected with a switching value and operation function module II 5023, and the switching value and operation function module II 5023 is connected with a selection loop function module of the two-quadrant feedforward signal control loop 402.
The three-quadrant feedforward enable signal control loop 503 comprises a low-value signal selection module II 5031 for receiving a signal of the first subtraction function module 101 or the second subtraction function module 201 and a low-value signal selection module III 5032 for receiving a signal of the fourth subtraction function module 4013, wherein the low-value signal selection module II 5031 and the low-value signal selection module III 5032 are both connected with a switching value and operation function module III 5033, and the switching value and operation function module III 5033 is connected with a selection loop function module of the three-quadrant feedforward signal control loop 403;
the four-quadrant feedforward enable signal control loop 504 includes a low-value signal selection module four 5041 receiving a signal from the first subtraction function module 101 or the second subtraction function module 201 and a high-value signal selection module four 5042 receiving a signal from the fourth subtraction function module 4013, the low-value signal selection module four 5041 and the high-value signal selection module four 5042 are both connected to a switching value and arithmetic function module four 5043, and the switching value and arithmetic function module four 5043 is connected to a selection loop function module of the four-quadrant feedforward signal control loop 404.
The high value signal selection module of the present embodiment represents that two data input into the module are output in a larger amount; the low value signal selection module represents that two data input into the module are smaller outputs; the switching value and operation function module indicates that when the two input values are true, the output is true, otherwise the output is false.
The control principle of the invention is as follows:
the original single PID control loop of the intermediate point temperature is replaced by an intermediate point temperature water supply correction PID control loop 1 and a fire coal correction PID control loop 2, and the data processing module 3 is used for processing data. Converting a feed water flow instruction reference value by a fuel instruction output by a boiler master control according to a coal-water ratio relation, and superposing an output feed water flow correction value of a four-quadrant feed water correction PID control loop to obtain a feed water flow instruction; the main control output fuel quantity instruction of the boiler is used as a coal feeding quantity instruction reference value, and the coal feeding instruction is obtained after the output coal feeding quantity corrected value of the four-quadrant coal-fired correction PID control loop is superposed. The invention respectively performs decoupling control on the intermediate point temperature and the main steam pressure by a four-quadrant intermediate point temperature water supply correction PID control loop and a four-quadrant fire coal correction PID control loop.
Specifically, the control loop shown in fig. 3 is designed with the four quadrant control principle of fig. 2.
When both Δ T and Δ P are positive, i.e., at the first quadrant, both the mid-point temperature and the main steam pressure are higher than the set values, coal should be preferentially subtracted. As shown in fig. 3, 4, and 9, the one-quadrant feedforward enable signal is 1, the feedforward signals in the quadrants other than the one-quadrant feedforward signal are all 0, and the output value of the feedwater correction PID control loop remains unchanged, so the feedwater flow correction value remains unchanged. Because the quadrant feedforward enable signal is 1, the coal feed correction value is the sum of the quadrant feedforward (now negative) and the output value of the fire coal correction PID control loop. The final control effect is that the water supply flow is basically unchanged, the coal supply quantity is gradually reduced, and the intermediate point temperature and the main steam pressure are close to the set value after being gradually reduced.
When Δ T is positive and Δ P is negative, i.e., at the second limit, the midpoint temperature is higher than the set point and the main steam pressure is lower than the set point, water should be preferentially added. As shown in fig. 3, 5, and 10, at this time, the two-quadrant feedforward enable signal is 1, the feedforward signals in the quadrants other than the two-quadrant feedforward signal are all 0, and the output value of the fire coal correction PID control loop remains unchanged, so the coal feeding amount correction value remains unchanged. Because the two-quadrant feedforward enable signal is 1, the feedwater flow correction value is the sum of the two-quadrant feedforward (which is now positive) and the output value of the feedwater flow correction PID control loop. The final control effect is that the coal feeding amount is basically unchanged, the water feeding flow is gradually increased, and the intermediate point temperature and the main steam pressure are gradually close to the set values.
When both Δ T and Δ P are negative, i.e., at the third quadrant, both the mid-point temperature and the main steam pressure are lower than the set points, coal should be preferentially added. As shown in fig. 3, 6, and 11, at this time, the three-quadrant feedforward enable signal is 1, the feedforward signals in the quadrants other than the three-quadrant feedforward signal are all 0, and the output value of the feedwater correction PID control loop remains unchanged, so the feedwater flow correction value remains unchanged. Because the three quadrant feedforward enable signal is 1, the coal feed correction value is the sum of the three quadrant feedforward (now positive) and the output value of the fire coal correction PID control loop. The final control effect is that the water supply flow is basically unchanged, the coal supply quantity is gradually increased, and the intermediate point temperature and the main steam pressure are close to the set value after being gradually increased.
When Δ T is negative and Δ P is positive, i.e., at the fourth quadrant, the midpoint temperature is lower than the set point and the main steam pressure is higher than the set point, water should be preferentially reduced. As shown in fig. 3, 7, and 12, at this time, the four-quadrant feedforward enable signal is 1, the feedforward signals in the quadrants other than the four-quadrant feedforward signal are all 0, and the output value of the fire coal correction PID control loop remains unchanged, so the coal supply correction value remains unchanged. Because the four quadrant feedforward enable signal is 1, the feedwater flow correction value is the sum of the four quadrant feedforward (now negative) and the feedwater flow correction PID control loop output value. The final control effect is that the coal feeding amount is basically unchanged, the water feeding flow is gradually reduced, and the intermediate point temperature and the main steam pressure are gradually close to the set values.
It is worth mentioning that: as shown in fig. 4 to 8, the middle point temperature four-quadrant control feedforward signal is a comprehensive signal formed according to the middle point temperature and the main steam pressure deviation, and a function f (x) and a gain coefficient K need to be adjusted according to the actual situation on site to obtain a proper four-quadrant feedforward value in the engineering implementation process.
As shown in fig. 9 to 12, the middle point temperature four-quadrant control feedforward enable signal is a switching value signal judged according to the middle point temperature and the main steam pressure deviation, and the boundary condition of the four-quadrant feedforward function can be modified according to the actual situation on site in the engineering implementation process.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (7)
1. A supercritical once-through boiler unit intermediate point temperature four-quadrant control method is characterized in that: a four-quadrant coordinate system is established by taking the difference delta P between the main steam pressure and the pressure set value thereof as an abscissa and taking the difference delta T between the intermediate point temperature and the temperature set value thereof as an ordinate, and the intermediate point temperature control mode is as follows:
when both delta T and delta P are positive, the engine is located in a first quadrant, the actual values of the intermediate point temperature and the main steam pressure are higher than the corresponding set values, and the fuel quantity correction value is preferentially reduced;
when the delta T is positive and the delta P is negative, the steam turbine is located in a second quadrant, the actual value of the temperature of the middle point is higher than the set value of the temperature, the actual value of the main steam pressure is lower than the set value of the main steam pressure, and the corrected value of the water supply flow is preferentially increased;
when both delta T and delta P are negative, the fuel quantity correction value is preferentially increased when the fuel quantity correction value is located in the third quadrant, the actual values of the intermediate point temperature and the main steam pressure are lower than the corresponding set values;
when the delta T is negative and the delta P is positive, the steam turbine is located in the fourth quadrant, the actual value of the intermediate point temperature is lower than the set value, the actual value of the main steam pressure is higher than the set value, and the corrected value of the water supply flow is preferentially reduced.
2. A control loop applying the supercritical once-through boiler unit intermediate point temperature four-quadrant control method as set forth in claim 1 is characterized in that: the system comprises a four-quadrant PID control loop, wherein the four-quadrant PID control loop comprises a middle point temperature water supply correction PID control loop, a fire coal correction PID control loop and a data processing module, and the data processing module is respectively connected with the middle point temperature water supply correction PID control loop and the fire coal correction PID control loop.
3. The control loop of claim 2, wherein:
the intermediate point temperature water supply correction PID control loop comprises a subtraction function module I for receiving an intermediate point temperature set value and a feedback value, a selection output function module I with a dead zone, a PID controller I and an addition function module I which are sequentially connected;
the coal-fired correction PID control loop comprises a subtraction function module II for receiving a set value and a feedback value of the intermediate point temperature, a selection output function module II with a dead zone, a PID controller II and an addition function module II which are connected in sequence;
the data processing module comprises a feedforward signal control loop, a fold line function module I, an analog signal generator, a subtraction function module III, a first data processing module and a second data processing module, wherein the signal input end of the fold line function module I is connected with the feedforward signal control loop and the analog signal generator, the signal output ends of the fold line function module I are respectively connected with the first data processing module and the subtraction function module III, the signal input end of the first data processing module is connected with the signal output end of the PID controller I, the signal output end of the first data processing module is connected with the signal input end of the addition function module I, the signal output end of the subtraction function module III is connected with the signal input end of the second data processing module, the signal input end of the second data processing module is connected with the signal output end of the PID controller II, and the signal output end of the second data processing module is connected with the signal input end of the, and the first addition function module and the second addition function module respectively output a water supply quantity correction value and a fuel quantity correction value.
4. The control loop of claim 3, wherein:
the first data processing module comprises a multiplication function module I, a high-low limit monitoring module I and a rate function module I which are sequentially connected;
the second data processing module comprises a multiplication function module II, a high-low limit monitoring module II and a rate function module II which are connected in sequence.
5. The control loop of claim 3, wherein: the feedforward signal control loop comprises a quadrant feedforward signal control loop, a two-quadrant feedforward signal control loop, a three-quadrant feedforward signal control loop and a four-quadrant feedforward signal control loop, wherein:
the first quadrant feedforward signal control loop comprises a second fold line function module, a third multiplication function module, a fourth subtraction function module, a third fold line function module, a fourth multiplication function module, a fifth subtraction function module and a selection loop function module, wherein the second fold line function module receives signals of the first subtraction function module or the second subtraction function module; the second broken line function module is connected with the third multiplication function module; the fourth subtraction function module, the third fold line function module and the fourth multiplication function module are sequentially connected; the third multiplication function module and the fourth multiplication function module are respectively connected with the input end of the fifth subtraction function module, and the output end of the fifth subtraction function module is connected with the selection loop function module;
the structures of the two-quadrant feedforward signal control loop, the three-quadrant feedforward signal control loop and the four-quadrant feedforward signal control loop are the same as the structure of the one-quadrant feedforward signal control loop.
6. The control loop of claim 5, wherein: the input end of the addition function module III is respectively connected with the signal output ends of the selection loop function modules of the first quadrant feedforward signal control loop, the second quadrant feedforward signal control loop, the third quadrant feedforward signal control loop and the fourth quadrant feedforward signal control loop, and the signal input end of the addition function module III is connected with the first fold line function module.
7. The control loop of claim 5, wherein: the selection loop function module of the one-quadrant feedforward signal control loop, the two-quadrant feedforward signal control loop, the three-quadrant feedforward signal control loop and the four-quadrant feedforward signal control loop is correspondingly connected with a one-quadrant feedforward enabling signal control loop, a two-quadrant feedforward enabling signal control loop, a three-quadrant feedforward enabling signal control loop and a four-quadrant feedforward enabling signal control loop, wherein:
the first quadrant feedforward enabling signal control loop comprises a first high-value signal selection module for receiving signals of a first subtraction function module or a second subtraction function module and a second high-value signal selection module for receiving signals of a fourth subtraction function module, the first high-value signal selection module and the second high-value signal selection module are both connected with a first switching value and operation function module, and the first switching value and operation function module is connected with a selection loop function module of the first quadrant feedforward signal control loop;
the two-quadrant feedforward enabling signal control loop comprises a high-value signal selection module III for receiving signals of a subtraction function module I or a subtraction function module II and a low-value signal selection module I for receiving signals of a subtraction function module IV, the high-value signal selection module III and the low-value signal selection module I are both connected with a switching value and operation function module II, and the switching value and operation function module II is connected with a selection loop function module of the two-quadrant feedforward signal control loop;
the three-quadrant feedforward enabling signal control loop comprises a second low-value signal selection module for receiving signals of the first subtraction function module or the second subtraction function module and a third low-value signal selection module for receiving signals of the fourth subtraction function module, the second low-value signal selection module and the third low-value signal selection module are both connected with a third switching value and operation function module, and the third switching value and operation function module is connected with a selection loop function module of the three-quadrant feedforward signal control loop;
the four-quadrant feedforward enabling signal control loop comprises a low-value signal selection module IV for receiving signals of the first subtraction function module or the second subtraction function module and a high-value signal selection module IV for receiving signals of the fourth subtraction function module, the low-value signal selection module IV and the high-value signal selection module IV are both connected with a switching value and operation function module IV, and the switching value and operation function module IV is connected with a selection loop function module of the four-quadrant feedforward signal control loop.
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