Supercritical unit feed water flow dynamic control system

Abstract

This invention discloses a dynamic control system for feedwater flow in supercritical power plants, relating to the field of coal-fired power generation control technology. The system includes a coal-water basic time relationship module, a feedwater feedforward decoupling calculation module, a separator outlet temperature bidirectional collaborative control module, and a feedwater flow setpoint generation module. The coal-water basic time relationship module generates a coal-water reference feedforward signal based on load commands, RB operating conditions, and load increase / decrease signals. The feedwater feedforward decoupling calculation module decouples the boiler main control signal and matches dynamic characteristics through multiple sets of parallel inertial links. The separator outlet temperature bidirectional collaborative control module achieves bidirectional collaborative correction of feedwater flow and fuel quantity based on the co-directionality of temperature and pressure deviations. After safety limit constraints by the feedwater flow setpoint generation module, a precise final feedwater flow setpoint is output. This invention can improve the dynamic matching accuracy of the coal-water ratio and enhance the unit's operational stability and adaptability to operating conditions.

Description

Technical Field

[0001] This invention relates to the field of thermal process control technology in thermal power plants, specifically to a dynamic control system for feedwater flow in supercritical units. Background Technology

[0002] Supercritical thermal power units have become the mainstay of the power industry. Supercritical DC unit generators inherently possess characteristics such as pure delay, large inertia, and nonlinearity. Multiple parameters within the unit are interconnected and constrained, exhibiting strong coupling characteristics. For supercritical thermal power units, the baseline for feedwater control is the fuel-to-water ratio control. Feedwater control primarily ensures a balance in heat exchange between the working fluid entering the water-cooled walls and the fuel. Changing energy patterns and increasingly stringent grid peak-shaving and frequency regulation requirements have introduced numerous uncertain external disturbances to unit generators. The marketization of coal and the blending of coal have led to variations in coal quality, further increasing the difficulty of unit generator control. Feedwater control in supercritical units is the most critical aspect in adjusting steam flow and enthalpy. The aforementioned constraints place higher demands on feedwater control in supercritical units. Improper feedwater flow control, in addition to affecting the unit's load regulation capacity, can also cause long-term exceedances or significant fluctuations in important parameters such as main steam temperature, impacting unit safety.

[0003] For supercritical once-through units, the core strategy for feedwater control is based on the water-to-coal ratio, supplemented by intermediate point temperature or enthalpy correction. By dynamically matching feedwater flow rate and fuel quantity, the strong coupling and large inertia issues arising from the single-pass nature of once-through boilers (no steam drum) are addressed, ensuring stable main steam temperature and pressure and a smooth transition between dry and wet states. Since supercritical once-through boilers lack a steam drum buffer, the feedwater flow rate directly determines the evaporation rate and main steam parameters. The water-to-coal ratio (feedwater flow rate / fuel quantity) is the core control element. Conventional control strategies dynamically calculate based on the boiler's main control (fuel quantity), increasing the water-to-coal ratio proportionally when fuel quantity increases to ensure evaporation matches load demand. On the other hand, the intermediate point enthalpy or intermediate point temperature (water-cooled wall outlet temperature) serves as feedback. When the enthalpy is higher than the set value, it indicates insufficient feedwater, leading to an increase in feedwater flow rate; conversely, when the enthalpy is lower than the set value, the feedwater flow rate is reduced, ensuring precise matching of the water-to-coal ratio. However, with the construction of new power systems, the load adjustment range and amplitude of thermal power units are becoming larger and larger. In order to improve the load response capability of the units, a large-scale fuel overshoot control strategy is often adopted. At the same time, due to the uncertainty of coal quality, a mismatch occurs between fuel quantity and feedwater flow, or the feedwater flow fluctuates greatly in a short period of time with the overshoot of fuel quantity, which in turn causes feedwater control abnormalities and affects the operational stability of the units. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to solve the problem of abnormal feedwater control caused by the inability to accurately match the fuel quantity and feedwater flow rate in supercritical DC units.

[0005] The present invention solves the above-mentioned technical problems through the following technical means: a dynamic control system for feedwater flow of a supercritical unit, comprising: a coal-water basic time relationship module (1), a feedwater feedforward decoupling calculation module (2), a separator outlet temperature bidirectional collaborative control module (3), and a feedwater flow setpoint generation module (4);

[0006] The coal-water basic time relationship module (1) is used to generate a coal-water reference feedforward signal that matches the unit's operating conditions based on the load command, RB condition trigger signal and unit load increase / decrease condition signal. The feedwater feedforward decoupling calculation module (2) is used to perform the following operations based on the boiler main control signal B, the load command differential feedforward B3, and the separator outlet temperature correction coal quantity B5 output by the separator outlet temperature bidirectional collaborative control module (3): after deducting the load command differential feedforward B3 and the separator outlet temperature correction coal quantity B5 from the boiler main control signal B, it converts and generates the feedwater basic setpoint; at the same time, it generates the feedwater dynamic feedforward value based on the load command differential feedforward B3. The input terminals of the bidirectional collaborative control module (3) for separator outlet temperature are respectively connected to the actual temperature T of separator outlet, the set value Tsp of separator outlet temperature, the actual pressure PT of main steam, and the set value PTSP of main steam pressure; the bidirectional collaborative control module (3) for separator outlet temperature is used to generate a temperature correction control signal based on the deviation of separator outlet temperature. The first output is the feedwater temperature correction value to the feedwater flow rate set value generation module (4), and the second output is the corrected coal amount B5 for separator outlet temperature based on the same direction of the deviation of main steam pressure and the deviation of separator outlet temperature, and output to the feedwater feedforward decoupling calculation module (2). The water supply flow rate setpoint generation module (4) is used to output the final water supply flow rate setpoint W based on the water supply basic setpoint, water supply dynamic feedforward value, and water supply temperature correction value, after being constrained by safety limits.

[0007] This invention constructs a complete dynamic feedwater flow control system by setting up a coal-water basic time relationship module, a feedwater feedforward decoupling calculation module, a separator outlet temperature bidirectional collaborative control module, and a feedwater flow setpoint generation module. This effectively solves the core problem of fuel quantity and feedwater flow imbalance in existing technologies. Specifically, the coal-water basic time relationship module generates a coal-water reference feedforward signal that matches the unit's operating conditions based on load commands, RB condition trigger signals, and unit load increase / decrease signals. The feedwater feedforward decoupling calculation module decouples and dynamically matches the boiler main control signals. The separator outlet temperature bidirectional collaborative control module accurately corrects the bidirectional flow of feedwater and fuel. Finally, the feedwater flow setpoint generation module, constrained by safety limits, outputs a precise final feedwater flow setpoint. This significantly improves the dynamic matching accuracy of the water-coal ratio in supercritical DC units, avoids abnormal feedwater control, enhances the unit's adaptability to load adjustments and coal quality changes, and improves the safety and stability of unit operation.

[0008] Furthermore, the coal-water basic time relationship module (1) includes: a first function generator (101), a first analog quantity assignment module (111), a second analog quantity assignment module (112), a third analog quantity assignment module (113), a fourth analog quantity assignment module (114), a first multiplexer (115), a second multiplexer (116), a third multiplexer (117), a fifth analog quantity assignment module (123), a sixth analog quantity assignment module (124), a seventh analog quantity assignment module (125), a fourth multiplexer (121), a fifth multiplexer (122), and a first multiplier (131); The load command is input to the input terminal of the first function generator (101), and the output terminal of the first function generator (101) outputs a coal-water feedforward base value that matches the current unit load to the first input terminal of the first multiplier (131); The first multiplexer (115), the second multiplexer (116), and the third multiplexer (117) are switches with RB condition triggering logic; the trigger terminal of the first multiplexer (115) is connected to the supply and exhaust air RB trigger signal, and its signal input terminal is connected to the preset RB correction coefficient of the first analog quantity assignment module (111); the trigger terminal of the second multiplexer (116) is connected to the primary air RB trigger signal, and its signal input terminal is connected to the preset RB correction coefficient of the second analog quantity assignment module (112); the trigger terminal of the third multiplexer (117) is connected to the corresponding supply and exhaust air RB enhancement trigger signal, and its signal input terminal is connected to the preset RB correction coefficient of the third analog quantity assignment module (113); The outputs of the first multiplexer (115), the second multiplexer (116), and the third multiplexer (117) are connected in parallel to the operating condition correction bus. The operating condition correction bus is connected to the output of the fourth analog quantity assignment module (114). When there is no RB operating condition trigger, the operating condition correction bus outputs the reference correction coefficient 1 of the fourth analog quantity assignment module (114). The final output of the operating condition correction bus outputs the RB operating condition correction coefficient matching the current RB operating condition to the second input of the first multiplier (131). The fourth multiplexer (121) and the fifth multiplexer (122) are switches with variable load triggering logic; the trigger terminal of the fourth multiplexer (121) is connected to the load increase trigger signal, and its signal input terminal is connected to the load increase correction coefficient of the fifth analog quantity assignment module (123). When there is no load increase trigger, it outputs a reference coefficient of 1; the trigger terminal of the fifth multiplexer (122) is connected to the load decrease trigger signal, and its signal input terminal is connected to the load decrease correction coefficient of the seventh analog quantity assignment module (124). When there is no load decrease trigger, it is connected to the steady-state reference coefficient of the sixth analog quantity assignment module (125); The outputs of the fourth multiplexer (121) and the fifth multiplexer (122) are combined and output to the third input of the first multiplier (131) with a variable load correction coefficient that matches the current variable load condition. The first multiplier (131) multiplies and corrects the input coal-water feedforward base value, RB condition correction coefficient, and variable load correction coefficient, and outputs the final coal-water reference feedforward signal to the feedwater feedforward decoupling operation module (2).

[0009] Furthermore, the feedwater feedforward decoupling operation module (2) also includes a boiler main control operation unit (21), which includes: a second function generator (211), a differential operation unit (212), a first PID controller (213), and a first adder (214). The load command is input to the input terminal of the second function generator (211), and the output terminal of the second function generator (211) outputs the static coal quantity B1 that matches the unit load to the first input terminal of the first adder (214); The load command is input to the input terminal of the differential operation unit (212), and the output terminal of the differential operation unit (212) outputs the load command differential feedforward B3 to the second input terminal of the first adder (214); The deviation signal between the main steam pressure setpoint PTSP and the actual main steam pressure PT is input to the input terminal of the first PID controller (213), and the output terminal of the first PID controller (213) outputs the boiler main control closed loop feedforward B2 to the third input terminal of the first adder (214); The separator outlet temperature correction coal quantity B5 output by the separator outlet temperature bidirectional collaborative control module (3) is input to the fourth input terminal of the first adder (214); The first adder (214) adds the input signals of each channel to perform the operation, satisfying the operation formula: Boiler main control signal B = static coal quantity B1 + boiler main control closed loop feedforward B2 + load command differential feedforward B3 + separator outlet temperature correction coal quantity B5.

[0010] Furthermore, the feedforward decoupling operation module (2) includes: a second adder (215), a third function generator (216), a first inertial element (217), a second inertial element (218), a third inertial element (219), a ninth analog quantity assignment module (221), a second multiplier (222), a fourth function generator (223), a fourth inertial element (224), a fifth inertial element (225), and a sixth inertial element (226); The boiler main control signal B output by the boiler main control calculation unit (21), the separator outlet temperature correction coal quantity B5 output by the separator outlet temperature bidirectional collaborative control module (3), and the load command differential feedforward B3 output by the boiler main control calculation unit (21) are respectively connected to the input terminal of the second adder (215); the calculation formula of the second adder (215) is: output value = boiler main control signal B - load command differential feedforward B3 - separator outlet temperature correction coal quantity B5, and its output terminal is connected to the input terminal of the third function generator (216); The third function generator (216) has a built-in preset fuel-water ratio conversion function, and its output is connected in parallel to the input of the first inertial element (217), the second inertial element (218), and the third inertial element (219); The coal-water reference feedforward signal output by the coal-water basic time relationship module (1) is also connected in parallel to the input terminals of the first inertial link (217), the second inertial link (218), and the third inertial link (219); The first inertial link (217), the second inertial link (218), and the third inertial link (219) are first-order inertial links with different preset time constants. The output of each inertial link is combined to output the dynamic feedforward value of water supply to the water supply flow rate setpoint generation module (4). The load command differential feedforward B3 of the boiler main control calculation unit (21) is input to the first input terminal of the second multiplier (222), and the preset differential feedforward gain correction coefficient output by the ninth analog quantity assignment module (221) is input to the second input terminal of the second multiplier (222). The output of the second multiplier (222) is connected to the input of the fourth function generator (223), and the output of the fourth function generator (223) is connected in parallel to the inputs of the fourth inertial element (224), the fifth inertial element (225), and the sixth inertial element (226); The fourth inertial link (224), the fifth inertial link (225), and the sixth inertial link (226) are first-order inertial links with different time constants set in parallel. They are used to fit the multi-order inertial characteristics of boiler fuel combustion. The outputs of each inertial link are combined to output the feedwater basic set value corresponding to the fuel dynamic feedforward, and the feedwater basic set value is output to the feedwater flow rate set value generation module (4).

[0011] Furthermore, the bidirectional collaborative control module (3) for the separator outlet temperature includes a second PID controller (311), a fifth function generator (312), a sixth multiplexer (313), and a working condition judgment logic unit (314). The actual outlet temperature T of the separator and the setpoint Tsp of the outlet temperature of the separator are respectively connected to the two input terminals of the second PID controller (311). The output terminal of the second PID controller (311) is divided into two paths: the first path directly outputs the feed water temperature correction value to the feed water flow setpoint generation module (4), and the second path is connected to the input terminal of the fifth function generator (312). The fifth function generator (312) has a built-in water-fuel conversion function, and its output is connected to the signal input of the sixth multiplexer (313). The actual temperature T at the separator outlet, the setpoint Tsp at the separator outlet, the actual pressure PT of the main steam, and the setpoint PTSP of the main steam pressure are all connected to the input terminal of the operating condition judgment logic unit (314). The output terminal of the operating condition judgment logic unit (314) outputs a switching trigger signal to the trigger terminal of the sixth multiplexer (313). The sixth multi-channel switch (313) is a switch with a holding function. Its output terminal outputs the corrected coal quantity B5 for the separator outlet temperature and connects to the feedwater feedforward decoupling calculation module (2).

[0012] Further, the operating condition judgment logic unit (314) presets a co-directional deviation conduction condition, which is: when (T < Tsp) and (PT < PTSP) are satisfied, or when (T > Tsp) and (PT > PTSP) are satisfied, the operating condition judgment logic unit (314) outputs a conduction trigger signal to the trigger terminal of the sixth multiplexer (313), and the sixth multiplexer (313) conducts, and the temperature - fuel correction signal output by the fifth function generator (312) is output as the separator outlet temperature corrected coal quantity B5; when the above conduction condition is not satisfied, the operating condition judgment logic unit (314) outputs a cut-off signal, the sixth multiplexer (313) is cut off, and the separator outlet temperature corrected coal quantity B5 remains unchanged at the current value.

[0013] Further, the feed water flow rate setting value generation module (4) includes a third adder (411), an eighth analog quantity assignment module (412), and a comparator (413); The feed water dynamic feedforward value output by the feed water feedforward decoupling operation module (2), the feed water basic setting value, and the feed water temperature correction value output by the separator outlet temperature two-way collaborative control module (3) are respectively connected to the input terminals of the third adder (411). The third adder (411) adds and operates the three input signals, and its output terminal outputs the feed water flow rate setting value to the first input terminal of the comparator (413); The output terminal of the eighth analog quantity assignment module (412) outputs a preset minimum feed water flow rate limit value to the second input terminal of the comparator (413); the comparator (413) outputs the larger value of the two input signals as the final feed water flow rate set point W.

[0014] The advantages of the present invention are as follows: 1. By setting the coal-water basic time relationship module and the feed water feedforward decoupling operation module, the present invention separates the feed water flow rate setting value into dynamic and static components and configures different inertia times respectively, abandoning the traditional coal-water decoupling method with a fixed inertia time. It not only uses the dynamic component to quickly adjust the main steam pressure, but also uses the static component as the core of the coal-water ratio adjustment, which can effectively reduce the disturbance of the dynamic fuel component on the main steam pressure and the main steam temperature during load change, and make the control parameters operate more smoothly.

[0015] 2. Through the separator outlet temperature two-way collaborative control module, according to the co-directionality of the main steam pressure deviation and the separator outlet temperature deviation, the present invention synchronously outputs the feed water temperature correction value and the separator outlet temperature corrected coal quantity, realizing the collaborative control of water adjustment and coal adjustment, and can accurately match the feed water flow rate and the fuel quantity according to the temperature and pressure operating state of the unit, avoiding the abnormal feed water control caused by the mismatch between the two.

[0016] 3. This invention employs operating condition judgment and multi-path switching logic, implementing coal quantity coordinated correction only when temperature and pressure deviations are in the same direction. Combined with the feedwater flow limit protection, it not only ensures the timeliness of coal-water ratio adjustment but also enhances the unit's adaptability under coal quality fluctuations and large-scale load changes, ensuring the stability of key parameters such as main steam pressure and separator outlet temperature, and improving the unit's operational safety and control stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a supercritical unit feedwater flow dynamic control system according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the boiler main control calculation unit in the feedwater feedforward decoupling calculation module of Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the structure of a conventional boiler main control scheme according to Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the conventional water supply flow control scheme of Embodiment 1 of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments: Example 1 First, the conventional boiler main control and feedwater flow control scheme will be explained: Figure 3 This is a schematic diagram of the conventional boiler main control scheme. The conventional boiler main control and feedwater flow control scheme is explained as follows: The conventional boiler main control B consists of three parts. The load command is processed by the function generator and outputs the boiler main control static feedforward B1. At the same time, the load command differential feedforward B3 is output after differential operation. The deviation between the actual value and the set value of the main steam pressure is processed by the PID controller and outputs the closed-loop regulation quantity B2 after proportional and integral operation. The above three signals are summed to generate the final boiler main control signal B.

[0020] Figure 4This is a schematic diagram of a conventional feedwater flow control scheme. The feedwater flow setpoint W is composed of two superimposed parts. The first part is the basic feedwater flow generated by the boiler main control B after processing by the fuel-feedwater function generator and passing through three inertial links in sequence. The time constant of the inertial link is generated by the load command through the coal-water basic time relationship function generator, and then comprehensively corrected by combining the outputs of multiple sets of switchers for forced draft RB, primary air RB operating conditions and load increase / decrease operating conditions to match the coal-water relationship under different operating conditions. The second part is the temperature correction amount obtained by the PID controller through the deviation between the actual value and the set value of the separator outlet temperature. The basic feedwater flow and the temperature correction amount are summed and then limited by the minimum feedwater flow limit through the high value selector to finally generate the feedwater flow setpoint W.

[0021] Conventional control schemes do not decouple the boiler main control signals, and the separator outlet temperature is only corrected by unidirectional feedwater, which cannot combine the main steam pressure and temperature deviation to achieve bidirectional coordinated control, making it difficult to accurately match fuel quantity and feedwater flow.

[0022] Figure 1 This is a schematic diagram of the structure of a supercritical unit feedwater flow dynamic control system according to the present invention. The supercritical unit feedwater flow dynamic control system includes: a coal-water basic time relationship module (1), a feedwater feedforward decoupling calculation module (2), a separator outlet temperature bidirectional collaborative control module (3), and a feedwater flow setpoint generation module (4).

[0023] The coal-water basic time relationship module (1) is used to generate a coal-water reference feedforward signal that matches the unit's operating conditions based on the load command, RB condition trigger signal and unit load increase / decrease condition signal.

[0024] Specifically, the coal-water basic time relationship module (1) includes: a first function generator (101), a first analog quantity assignment module (111), a second analog quantity assignment module (112), a third analog quantity assignment module (113), a fourth analog quantity assignment module (114), a first multiplexer (115), a second multiplexer (116), a third multiplexer (117), a fifth analog quantity assignment module (123), a sixth analog quantity assignment module (124), a seventh analog quantity assignment module (125), a fourth multiplexer (121), a fifth multiplexer (122), and a first multiplier (131).

[0025] The load command is input to the input terminal of the first function generator (101). The first function generator (101) is a linear function generator, and its output is related to the input as a linear function. The output terminal of the first function generator (101) outputs the coal-water feedforward base value that matches the current unit load to the first input terminal of the first multiplier (131).

[0026] The first multiplexer (115), the second multiplexer (116), and the third multiplexer (117) are switches with RB condition triggering logic.

[0027] The trigger terminal of the first multiplexer (115) is connected to the air supply and exhaust RB trigger signal, and its signal input terminal is connected to the preset RB correction coefficient of the first analog quantity assignment module (111).

[0028] The trigger terminal of the second multiplexer (116) is connected to the primary wind RB trigger signal, and its signal input terminal is connected to the preset RB correction coefficient of the second analog quantity assignment module (112).

[0029] The trigger terminal of the third multiplexer (117) is connected to the corresponding air supply and exhaust RB enhancement trigger signal, and its signal input terminal is connected to the preset RB correction coefficient of the third analog quantity assignment module (113).

[0030] The outputs of the first multiplexer (115), the second multiplexer (116), and the third multiplexer (117) are connected in parallel to the operating condition correction bus. When there is no RB operating condition trigger, the operating condition correction bus outputs the reference correction coefficient 1 of the fourth analog quantity assignment module (114). The final output of the operating condition correction bus outputs the RB operating condition correction coefficient that matches the current RB operating condition to the second input of the first multiplier (131).

[0031] The fourth multiplexer (121) and the fifth multiplexer (122) are switches with variable load triggering logic.

[0032] The trigger terminal of the fourth multiplexer (121) is connected to the load increase trigger signal, and its signal input terminal is connected to the load increase correction coefficient of the fifth analog quantity assignment module (123). When there is no load increase trigger, the output reference coefficient is 1.

[0033] The trigger terminal of the fifth multiplexer (122) is connected to the load reduction trigger signal, and its signal input terminal is connected to the load reduction correction coefficient of the seventh analog quantity assignment module (124). When there is no load reduction trigger, it is connected to the steady-state reference coefficient of the sixth analog quantity assignment module (125).

[0034] The outputs of the fourth multiplexer (121) and the fifth multiplexer (122) are combined to output a variable load correction coefficient that matches the current variable load condition to the third input of the first multiplier (131).

[0035] The first multiplier (131) multiplies and corrects the input coal-water feedforward base value, RB condition correction coefficient, and variable load correction coefficient, and outputs the final coal-water reference feedforward signal to the feedwater feedforward decoupling operation module (2).

[0036] The feedwater feedforward decoupling calculation module (2) is used to perform the following operations based on the boiler main control signal B, the load command differential feedforward B3, and the separator outlet temperature correction coal quantity B5 output by the separator outlet temperature bidirectional collaborative control module (3): after deducting the load command differential feedforward B3 and the separator outlet temperature correction coal quantity B5 from the boiler main control signal B, it converts and generates the feedwater basic setpoint; at the same time, it generates the feedwater dynamic feedforward value based on the load command differential feedforward B3.

[0037] Specifically, such as Figure 2 As shown, the feedwater feedforward decoupling operation module (2) includes a boiler main control operation unit (21), which includes: a second function generator (211), a differential operation unit (212), a first PID controller (213), and a first adder (214).

[0038] The load command is input to the input terminal of the second function generator (211). The second function generator (211) is a linear function generator, and its output is related to the input as a linear function. The output terminal of the second function generator (211) outputs the static coal quantity B1 that matches the unit load to the first input terminal of the first adder (214).

[0039] The load command is input to the input terminal of the differential operation unit (212), and the output terminal of the differential operation unit (212) outputs the load command differential feedforward B3 to the second input terminal of the first adder (214).

[0040] The deviation signal between the main steam pressure setpoint PTSP and the actual main steam pressure PT is input to the input terminal of the first PID controller (213), and the output terminal of the first PID controller (213) outputs the boiler main control closed loop feedforward B2 to the third input terminal of the first adder (214).

[0041] The separator outlet temperature correction coal quantity B5 output by the separator outlet temperature bidirectional collaborative control module (3) is input to the fourth input terminal of the first adder (214).

[0042] The first adder (214) adds the input signals of each channel to perform the operation, which satisfies the operation formula: Boiler main control signal B = static coal quantity B1 + boiler main control closed loop feedforward B2 + load command differential feedforward B3 + separator outlet temperature correction coal quantity B5.

[0043] The feedforward decoupling operation module (2) also includes: a second adder (215), a third function generator (216), a first inertial element (217), a second inertial element (218), a third inertial element (219), a ninth analog quantity assignment module (221), a second multiplier (222), a fourth function generator (223), a fourth inertial element (224), a fifth inertial element (225), and a sixth inertial element (226).

[0044] The boiler main control signal B output by the boiler main control calculation unit (21), the separator outlet temperature correction coal quantity B5 output by the separator outlet temperature bidirectional collaborative control module (3), and the load command differential feedforward B3 output by the boiler main control calculation unit (21) are respectively connected to the input terminal of the second adder (215); the calculation formula of the second adder (215) is: output value = boiler main control signal B - load command differential feedforward B3 - separator outlet temperature correction coal quantity B5, and its output terminal is connected to the input terminal of the third function generator (216).

[0045] The third function generator (216) has a built-in preset fuel-water ratio conversion function. This conversion function is a linear function, and the output and input are in a linear relationship. Its output is connected in parallel to the input of the first inertial element (217), the second inertial element (218), and the third inertial element (219).

[0046] The coal-water reference feedforward signal output by the coal-water basic time relationship module (1) is also connected in parallel to the input terminals of the first inertial link (217), the second inertial link (218), and the third inertial link (219).

[0047] The first inertial element (217), the second inertial element (218), and the third inertial element (219) are first-order inertial elements with different preset time constants. The outputs of each inertial element are combined to output the dynamic feedforward value of the water supply to the water supply flow setpoint generation module (4). The calculation formula for the first-order inertial element is: ;in, This is the current output. The output from the previous moment. The sampling period is The inertial time constant, This is the current input.

[0048] The load command differential feedforward B3 of the boiler main control calculation unit (21) is input to the first input terminal of the second multiplier (222), and the preset differential feedforward gain correction coefficient output by the ninth analog quantity assignment module (221) is input to the second input terminal of the second multiplier (222).

[0049] The output of the second multiplier (222) is connected to the input of the fourth function generator (223). The fourth function generator (223) has a built-in preset fuel-water ratio conversion function. This conversion function is a linear function, and its output has a linear relationship with the input. The output of the fourth function generator (223) is connected in parallel to the input of the fourth inertial element (224), the fifth inertial element (225), and the sixth inertial element (226).

[0050] The fourth inertial link (224), the fifth inertial link (225), and the sixth inertial link (226) are first-order inertial links with different time constants set in parallel. They are used to fit the multi-order inertial characteristics of boiler fuel combustion. The outputs of each inertial link are combined to output the feedwater basic setpoint corresponding to the fuel dynamic feedforward, and the feedwater basic setpoint is output to the feedwater flow rate setpoint generation module (4).

[0051] The input terminals of the separator outlet temperature bidirectional collaborative control module (3) are respectively connected to the actual outlet temperature T, the setpoint Tsp, the actual pressure PT, and the setpoint PTSP of the main steam. The separator outlet temperature bidirectional collaborative control module (3) is used to generate a temperature correction control signal based on the separator outlet temperature deviation. The first output is the feedwater temperature correction value to the feedwater flow rate setpoint generation module (4). The second output is the separator outlet temperature correction coal quantity B5 based on the same direction of the main steam pressure deviation and the separator outlet temperature deviation, and is output to the feedwater feedforward decoupling calculation module (2).

[0052] Specifically, the separator outlet temperature bidirectional collaborative control module (3) includes a second PID controller (311), a fifth function generator (312), a sixth multiplexer (313), and a working condition judgment logic unit (314).

[0053] The actual outlet temperature T of the separator and the setpoint Tsp of the outlet temperature of the separator are respectively connected to the two input terminals of the second PID controller (311). The output terminal of the second PID controller (311) is divided into two paths: the first path directly outputs the feed water temperature correction value to the feed water flow rate setpoint generation module (4), and the second path is connected to the input terminal of the fifth function generator (312). The fifth function generator (312) has a built-in water-fuel conversion function. This conversion function is a linear function, and the output is related to the input as a linear function. Its output is connected to the signal input of the sixth multiplexer (313).

[0054] The actual temperature T at the separator outlet, the set value Tsp of the separator outlet temperature, the actual pressure PT of the main steam, and the set value PTSP of the main steam pressure are all connected to the input end of the operating condition judgment logic unit (314). The output end of the operating condition judgment logic unit (314) outputs a switching trigger signal to the trigger end of the sixth multiplexer (313). The operating condition judgment logic unit (314) presets a co-directional deviation conduction condition, and the co-directional deviation conduction condition is: when (T < Tsp) and (PT < PTSP) are satisfied, or when (T > Tsp) and (PT > PTSP) are satisfied, the operating condition judgment logic unit (314) outputs a conduction trigger signal to the trigger end of the sixth multiplexer (313), and the sixth multiplexer (313) conducts, and the temperature - fuel correction signal output by the fifth function generator (312) is output as the coal quantity B5 for correcting the separator outlet temperature; when the above conduction condition is not satisfied, the operating condition judgment logic unit (314) outputs a cut-off signal, the sixth multiplexer (313) is cut off, and the coal quantity B5 for correcting the separator outlet temperature remains unchanged at the current value.

[0055] The sixth multiplexer (313) is a switch with a holding function, and its output end outputs the coal quantity B5 for correcting the separator outlet temperature, which is connected to the feedwater feedforward decoupling operation module (2).

[0056] The feedwater flow rate set value generation module (4) is used to output the final feedwater flow rate set point W after being constrained by the safety limit according to the feedwater basic set value, the feedwater dynamic feedforward value, and the feedwater temperature correction value.

[0057] Specifically, the feedwater flow rate set value generation module (4) includes a third adder (411), an eighth analog quantity assignment module (412), and a comparator (413).

[0058] The feedwater dynamic feedforward value output by the feedwater feedforward decoupling operation module (2), the feedwater basic set value, and the feedwater temperature correction value output by the separator outlet temperature two-way collaborative control module (3) are respectively connected to the input end of the third adder (411).

[0059] The third adder (411) adds and operates the three input signals, and its output end outputs the feedwater flow rate set value to the first input end of the comparator (413); The output end of the eighth analog quantity assignment module (412) outputs a preset minimum feedwater flow rate limit value to the second input end of the comparator (413); the comparator (413) outputs the larger value of the two input signals as the final feedwater flow rate set point W.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A supercritical unit feedwater flow dynamic control system, characterized by, include: The coal-water basic time relationship module (1), the feedwater feedforward decoupling calculation module (2), the separator outlet temperature bidirectional collaborative control module (3), and the feedwater flow rate setpoint generation module (4) are all included. The coal-water basic time relationship module (1) is used to generate a coal-water reference feedforward signal that matches the unit's operating conditions based on the load command, RB condition trigger signal and unit load increase / decrease condition signal. The feedwater feedforward decoupling calculation module (2) is used to perform the following operations based on the boiler main control signal B, the load command differential feedforward B3, and the separator outlet temperature correction coal quantity B5 output by the separator outlet temperature bidirectional collaborative control module (3): after deducting the load command differential feedforward B3 and the separator outlet temperature correction coal quantity B5 from the boiler main control signal B, it converts and generates the feedwater basic setpoint; at the same time, it generates the feedwater dynamic feedforward value based on the load command differential feedforward B3. The input terminals of the bidirectional collaborative control module (3) for separator outlet temperature are respectively connected to the actual temperature T of separator outlet, the set value Tsp of separator outlet temperature, the actual pressure PT of main steam, and the set value PTSP of main steam pressure; the bidirectional collaborative control module (3) for separator outlet temperature is used to generate a temperature correction control signal based on the deviation of separator outlet temperature. The first output is the feedwater temperature correction value to the feedwater flow rate set value generation module (4), and the second output is the corrected coal amount B5 for separator outlet temperature based on the same direction of the deviation of main steam pressure and the deviation of separator outlet temperature, and output to the feedwater feedforward decoupling calculation module (2). The water supply flow rate setpoint generation module (4) is used to output the final water supply flow rate setpoint W based on the water supply basic setpoint, water supply dynamic feedforward value, and water supply temperature correction value, after being constrained by safety limits.

2. The supercritical unit feedwater flow dynamic control system of claim 1, wherein, The coal-water basic time relationship module (1) includes: a first function generator (101), a first analog quantity assignment module (111), a second analog quantity assignment module (112), a third analog quantity assignment module (113), a fourth analog quantity assignment module (114), a first multiplexer (115), a second multiplexer (116), a third multiplexer (117), a fifth analog quantity assignment module (123), a sixth analog quantity assignment module (124), a seventh analog quantity assignment module (125), a fourth multiplexer (121), a fifth multiplexer (122), and a first multiplier (131); The load command is input to the input terminal of the first function generator (101), and the output terminal of the first function generator (101) outputs a coal-water feedforward base value that matches the current unit load to the first input terminal of the first multiplier (131); The first multiplexer (115), the second multiplexer (116), and the third multiplexer (117) are switches with RB condition triggering logic; the trigger terminal of the first multiplexer (115) is connected to the supply and exhaust air RB trigger signal, and its signal input terminal is connected to the preset RB correction coefficient of the first analog quantity assignment module (111); the trigger terminal of the second multiplexer (116) is connected to the primary air RB trigger signal, and its signal input terminal is connected to the preset RB correction coefficient of the second analog quantity assignment module (112); the trigger terminal of the third multiplexer (117) is connected to the corresponding supply and exhaust air RB enhancement trigger signal, and its signal input terminal is connected to the preset RB correction coefficient of the third analog quantity assignment module (113); The outputs of the first multiplexer (115), the second multiplexer (116), and the third multiplexer (117) are connected in parallel to the operating condition correction bus. The operating condition correction bus is connected to the output of the fourth analog quantity assignment module (114). When there is no RB operating condition trigger, the operating condition correction bus outputs the reference correction coefficient 1 of the fourth analog quantity assignment module (114). The final output of the operating condition correction bus outputs the RB operating condition correction coefficient matching the current RB operating condition to the second input of the first multiplier (131). The fourth multiplexer (121) and the fifth multiplexer (122) are switches with variable load triggering logic; the trigger terminal of the fourth multiplexer (121) is connected to the load increase trigger signal, and its signal input terminal is connected to the load increase correction coefficient of the fifth analog quantity assignment module (123). When there is no load increase trigger, it outputs a reference coefficient of 1; the trigger terminal of the fifth multiplexer (122) is connected to the load decrease trigger signal, and its signal input terminal is connected to the load decrease correction coefficient of the seventh analog quantity assignment module (124). When there is no load decrease trigger, it is connected to the steady-state reference coefficient of the sixth analog quantity assignment module (125); The outputs of the fourth multiplexer (121) and the fifth multiplexer (122) are combined and output to the third input of the first multiplier (131) with a variable load correction coefficient that matches the current variable load condition. The first multiplier (131) multiplies and corrects the input coal-water feedforward base value, RB condition correction coefficient, and variable load correction coefficient, and outputs the final coal-water reference feedforward signal to the feedwater feedforward decoupling operation module (2).

3. The supercritical unit feedwater flow dynamic control system of claim 1, wherein, The feedwater feedforward decoupling operation module (2) also includes a boiler main control operation unit (21), which includes: a second function generator (211), a differential operation unit (212), a first PID controller (213), and a first adder (214); The load command is input to the input terminal of the second function generator (211), and the output terminal of the second function generator (211) outputs the static coal quantity B1 that matches the unit load to the first input terminal of the first adder (214); The load command is input to the input terminal of the differential operation unit (212), and the output terminal of the differential operation unit (212) outputs the load command differential feedforward B3 to the second input terminal of the first adder (214); The deviation signal between the main steam pressure setpoint PTSP and the actual main steam pressure PT is input to the input terminal of the first PID controller (213), and the output terminal of the first PID controller (213) outputs the boiler main control closed loop feedforward B2 to the third input terminal of the first adder (214); The separator outlet temperature correction coal quantity B5 output by the separator outlet temperature bidirectional collaborative control module (3) is input to the fourth input terminal of the first adder (214); The first adder (214) adds the input signals of each channel to perform the operation, satisfying the operation formula: Boiler main control signal B = static coal quantity B1 + boiler main control closed loop feedforward B2 + load command differential feedforward B3 + separator outlet temperature correction coal quantity B5.

4. The supercritical unit feedwater flow dynamic control system of claim 1, wherein, The feedforward decoupling operation module (2) includes: a second adder (215), a third function generator (216), a first inertial element (217), a second inertial element (218), a third inertial element (219), a ninth analog quantity assignment module (221), a second multiplier (222), a fourth function generator (223), a fourth inertial element (224), a fifth inertial element (225), and a sixth inertial element (226); The boiler main control signal B output by the boiler main control calculation unit (21), the separator outlet temperature correction coal quantity B5 output by the separator outlet temperature bidirectional collaborative control module (3), and the load command differential feedforward B3 output by the boiler main control calculation unit (21) are respectively connected to the input terminal of the second adder (215); the calculation formula of the second adder (215) is: output value = boiler main control signal B - load command differential feedforward B3 - separator outlet temperature correction coal quantity B5, and its output terminal is connected to the input terminal of the third function generator (216); The third function generator (216) has a built-in preset fuel-water ratio conversion function, and its output is connected in parallel to the input of the first inertial element (217), the second inertial element (218), and the third inertial element (219); The coal-water reference feedforward signal output by the coal-water basic time relationship module (1) is also connected in parallel to the input terminals of the first inertial link (217), the second inertial link (218), and the third inertial link (219); The first inertial link (217), the second inertial link (218), and the third inertial link (219) are first-order inertial links with different preset time constants. The output of each inertial link is combined to output the dynamic feedforward value of water supply to the water supply flow rate setpoint generation module (4). The load command differential feedforward B3 of the boiler main control calculation unit (21) is input to the first input terminal of the second multiplier (222), and the preset differential feedforward gain correction coefficient output by the ninth analog quantity assignment module (221) is input to the second input terminal of the second multiplier (222). The output terminal of the second multiplier (222) is connected to the input terminal of the fourth function generator (223), and the output terminals of the fourth function generator (223) are respectively connected in parallel to the input terminals of the fourth inertia link (224), the fifth inertia link (225), and the sixth inertia link (226); The fourth inertia link (224), the fifth inertia link (225), and the sixth inertia link (226) are first-order inertia links with different time constants and are arranged in parallel, and are used to fit the multi-order inertia characteristics of boiler fuel combustion. The output terminals of each inertia link are combined to output the feedwater basic set value corresponding to the fuel dynamic feedforward, and the feedwater basic set value is output to the feedwater flow set value generation module (4).

5. The supercritical unit feedwater flow dynamic control system of claim 1, wherein, The separator outlet temperature two-way collaborative control module (3) includes a second PID controller (311), a fifth function generator (312), a sixth multiplexer (313), and a working condition judgment logic unit (314); The actual separator outlet temperature T and the separator outlet temperature set value Tsp are respectively connected to the two input terminals of the second PID controller (311). The output terminal of the second PID controller (311) is divided into two paths: the first path directly outputs the feedwater temperature correction value to the feedwater flow set value generation module (4), and the second path is connected to the input terminal of the fifth function generator (312); The fifth function generator (312) has a built-in feedwater-fuel conversion function, and its output terminal is connected to the signal input terminal of the sixth multiplexer (313); The actual separator outlet temperature T, the separator outlet temperature set value Tsp, the actual main steam pressure PT, and the main steam pressure set value PTSP are all connected to the input terminal of the working condition judgment logic unit (314), and the output terminal of the working condition judgment logic unit (314) outputs a switching trigger signal to the trigger terminal of the sixth multiplexer (313); The sixth multiplexer (313) is a switch with a hold function, and its output terminal outputs the separator outlet temperature corrected coal quantity B5, which is connected to the feedwater feedforward decoupling operation module (2).

6. The supercritical unit feedwater flow dynamic control system of claim 5, wherein, The working condition judgment logic unit (314) presets a co-directional deviation conduction condition, and the co-directional deviation conduction condition is: when (T < Tsp) and (PT < PTSP) are satisfied, or when (T > Tsp) and (PT > PTSP) are satisfied, the working condition judgment logic unit (314) outputs a conduction trigger signal to the trigger terminal of the sixth multiplexer (313), and the sixth multiplexer (313) conducts, and outputs the temperature-fuel correction signal output by the fifth function generator (312) as the separator outlet temperature corrected coal quantity B5; when the above conduction condition is not satisfied, the working condition judgment logic unit (314) outputs a cut-off signal, the sixth multiplexer (313) is cut off, and the separator outlet temperature corrected coal quantity B5 remains unchanged at the current value.

7. The supercritical unit feedwater flow dynamic control system of claim 1, wherein, The feedwater flow set value generation module (4) includes a third adder (411), an eighth analog quantity assignment module (412), and a comparator (413); The feedwater dynamic feedforward value output by the feedwater feedforward decoupling operation module (2), the feedwater basic setpoint, and the feedwater temperature correction value output by the separator outlet temperature bidirectional collaborative control module (3) are respectively connected to the input terminal of the third adder (411). The third adder (411) adds the three input signals together, and its output terminal outputs the water flow rate set value to the first input terminal of the comparator (413); The output terminal of the eighth analog quantity assignment module (412) outputs the preset minimum water supply flow limit to the second input terminal of the comparator (413); the comparator (413) outputs the larger value of the two input signals as the final water supply flow setpoint W.

Images