A model construction method and device of a coal-fired unit, a computer device and a medium

Abstract

The application provides a coal-fired unit model construction method and device, computer equipment and medium, and belongs to the field of energy optimization, and the method comprises the following steps: constructing dynamic models of multiple operation systems of a coal-fired unit based on preset simplified conditions respectively; determining a mapping relationship between input parameters and output parameters according to the multiple dynamic models, and obtaining a state variable expression of the coal-fired unit according to the mapping relationship; constructing a data group of input parameters, output parameters and state variables under the condition of uniform interval of loads according to variable load operation data of the coal-fired unit; determining constraint conditions of unknown parameters in the state variable expression according to the operation mechanism characteristics of the coal-fired unit; determining the unknown parameters according to the data group and the constraint conditions, and then obtaining a dynamic model under a wet state working condition of the coal-fired unit. In this way, the model constructed by the method not only has a reliable physical model structure, can describe system dynamic characteristics, and has high dynamic precision.

Description

Technical Field

[0001] This invention belongs to the field of energy optimization, specifically relating to a model construction method, apparatus, computer equipment, and medium for coal-fired power units. Background Technology

[0002] When a once-through coal-fired unit operates under wet conditions with variable load, the safety characteristics of the boiler water circulation and the operational stability of the water-cooled walls decrease. Furthermore, due to the small capacity of the unit's water storage tank, variable load operation leads to significant fluctuations in the tank level, which can easily cause water carryover in the superheater inlet steam, reducing superheater operational safety. Therefore, it is necessary to establish a dynamic model of the boiler-machine coordination system of a once-through coal-fired unit under wet conditions to reflect the dynamic characteristics of the system operation under wet conditions. This model can then be used in control system design to improve the operational flexibility and safety of the once-through coal-fired unit under wet conditions.

[0003] Currently, the main dynamic modeling methods for the boiler-generator coordination system of DC-DC boiler units are composite modeling and data-driven modeling. Composite modeling methods utilize physical conservation laws and mechanistic analysis of the system's operation to establish the physical structure of the system model and identify its functions and parameters using operational data. However, in composite modeling, model parameters and functions need to be obtained by combining multiple sets of steady-state operating data and regression analysis. However, when the unit is operating under varying loads, it is difficult to obtain multiple sets of stable operating data, thus limiting the applicability of this method. Data-driven modeling methods combine dynamic operating data of the unit with intelligent modeling methods, such as neural networks and fuzzy systems, to establish the system model. However, because this modeling method lacks mechanistic analysis, the reliability of the model structure is relatively low. Therefore, currently, there is a lack of practical, feasible, and highly accurate modeling methods for constructing models of DC-DC boiler coal-fired units under wet operating conditions. Summary of the Invention

[0004] To address the lack of practical, feasible, and accurate modeling methods for DC-fired coal-fired power units under wet operating conditions, this invention provides a modeling method, apparatus, computer equipment, and medium for coal-fired power units.

[0005] To achieve the above objectives, the present invention provides the following technical solution: First, a method for modeling coal-fired power units is provided, the method comprising: Based on the input and output parameters of the coal-fired power unit under wet operating conditions, dynamic models of multiple operating systems of the coal-fired power unit under preset simplified conditions are constructed respectively. The mapping relationship between input and output parameters is determined based on multiple dynamic models, and the state variable expression of the coal-fired unit is obtained based on the mapping relationship; the state variable is used to characterize the state change of the coal-fired unit under wet conditions. Based on the variable load operation data of the coal-fired unit, a data set of input parameters, output parameters and state variables is constructed under the condition of uniform load change intervals. Based on the operating mechanism characteristics of coal-fired power units, determine the constraints on the unknown parameters in the state variable expressions; The unknown parameters are determined based on the data set and the constraints, thereby obtaining a dynamic model of the coal-fired unit under wet operating conditions.

[0006] Optionally, the operating system includes a pulverizing system, an economizer and water-cooled wall system, a water storage tank system, a superheater system, and a steam turbine system; the dynamic model of the multiple operating systems includes: The dynamic model of the powder-making system is as follows: ; in, c 0 represents the inertia time of the powder-making system; r B This refers to the amount of coal fed into the furnace. u B It is a fuel quantity directive; τ This indicates the time delay in the flour milling system; t It is a time variable; The dynamic model of the economizer and water-cooled wall system is as follows: ; in, ρ lb The density of the working fluid at the outlet of the water-cooled wall; V lb For the volume of the economizer and water-cooled wall; D lb This refers to the outlet flow rate of the water-cooled wall. h lb This refers to the enthalpy of the working fluid at the outlet of the water-cooled wall. c j This refers to the specific heat capacity of the boiler's metal tube wall. m j For the metal quality of the boiler tube wall; T j This refers to the metal temperature of the boiler tube wall. h sm The enthalpy value of the working fluid imported into the economizer; Q 1 represents the heat absorbed by the working fluid in the economizer and water-cooled wall; k 1 represents the heat absorbed by the working fluid in the economizer and water-cooled wall when 1 kg of pulverized coal is burned. The dynamic model of the water storage tank system is as follows: ; in, V L For the volume of the water storage tank, ρL The density of the working fluid in the water storage tank. x lb The dryness of the steam at the water-cooled wall outlet. D xh This refers to the circulating water flow rate; The dynamic model of the superheater system includes a dynamic model of the superheated steam enthalpy and a dynamic model of the superheated steam pressure. The dynamic model of the superheated steam enthalpy of the superheater system is as follows: ; The dynamic model of superheated steam pressure in the superheater system is as follows: ; in, ρ st The density of the working fluid at the superheater outlet; V st This refers to the volume of the superheater; D lb This refers to the outlet flow rate of the water-cooled wall. h vbh The enthalpy of saturated steam at the superheater inlet; h st This refers to the enthalpy of the steam at the superheater outlet. Q 2 represents the heat absorbed by the working fluid in the superheater; k 2 represents the heat absorbed by the superheater working fluid when 1 kg of pulverized coal is burned; p st The working fluid pressure at the superheater outlet; k 3 represents the turbine fitting coefficient; u t For the turbine control valve opening; The dynamic model of the steam turbine system is as follows: ; in, N e For unit power; c 5 represents the turbine's inertial time; k 4 represents the turbine efficiency coefficient.

[0007] Optionally, determining the mapping relationship between input parameters and output parameters based on multiple dynamic models includes: The state-space form of the input parameters, output parameters, and state variables of the dynamic model of a coal-fired power unit under wet operating conditions is determined as follows: ; U , Y and X These are the model's input parameter matrix, output matrix, and state variable matrix, respectively. A (•),B (•), C (•) represents a matrix function, specifically: ; in, D fw To increase the outlet water flow rate; u t For the turbine control valve opening; H This refers to the water level in the storage tank. p m This refers to the steam pressure of the steam-water separator.

[0008] Optionally, the expression for the state variable is: ; in, T x For the recycle inertia time; c 1 and c 2 represents the inertial time of steam pressure and enthalpy in the economizer and water-cooled wall system; d 1 and d 2 represents the dynamic parameters in the economizer and water-cooled wall system; c 31 and c 32 The inertial time coefficient of the superheated steam temperature system; c 4 represents the heat storage coefficient of the superheater; c 5 represents the inertial time of the steam turbine generator system; ρ w The density of saturated water in the storage tank; F This refers to the bottom area of ​​the water storage tank.

[0009] Optionally, based on the operating mechanism characteristics of the coal-fired power unit, the constraints on the unknown parameters in the state variable expression include: Based on the heat absorption characteristics of the working fluid, determine k 1= k ( x 1) and k 2= g ( x 1); Through the analysis of Q i = k i x 1. Perform time-varying differentiation to ensure that the derivative of the heat absorbed by the working fluid remains greater than zero across the load variation range, thereby determining the unknown parameters. k 1 and k 2. Constraints; Based on the fact that the working fluid flow rates at the economizer inlet and the water-cooled wall outlet are the same, the constraint conditions are then determined. D sm= D lb ; Based on the operating mechanism characteristics of coal-fired power units, determine D lb = u t ( a 1 p m + b 1) / ( a 2 h lb + b 2), of which a 1, a 2, b 1, b 2 is an unknown parameter; Based on the mechanistic characteristics of wet steam and the thermodynamic properties of water vapor, a wet steam dryness fraction model is determined. x lb =( a 11 h lb + b 11 ) / ( a 22 p m + b 22 ),in a 11 , a 22 , b 11 , b 22 The parameter is unknown.

[0010] Optionally, the unknown parameters are determined based on the data set and the constraints: Based on the data set, regression analysis was used to determine the static parameters among the unknown parameters; Based on the constraints, and by combining the data set with the immune genetic optimization algorithm, the dynamic parameters in the unknown parameters of each system model are gradually identified.

[0011] Optionally, the preset simplification conditions include: The economizer and water-cooled wall are considered as a single heat-receiving tube system; The temperature of the superheated steam can be stably controlled, and the flow rate of the desuperheating water is integrated into the inlet flow rate of the superheater, thus treating the superheater as a single-tube heating system. Axial heat transfer between flue gas, boiler tube walls and working fluid is ignored; The heat released by flue gas on the boiler tube wall is directly proportional to the heat released by coal combustion. The fluid characteristics are uniform across any cross-sectional area of ​​the heated tube; The high-pressure, intermediate-pressure, and low-pressure cylinders of a steam turbine are considered as a single steam turbine system. The heat absorbed by the reheater is factored into the turbine coefficient.

[0012] Secondly, a model building device for a coal-fired power unit is also provided, the device comprising: The module is used to construct dynamic models of multiple operating systems of a coal-fired power unit under preset simplified conditions, based on the input and output parameters of the coal-fired power unit under wet operating conditions. The determination module is used to determine the mapping relationship between input parameters and output parameters based on multiple dynamic models, and to obtain the state variable expression of the coal-fired unit based on the mapping relationship; the state variable is used to characterize the state change of the coal-fired unit under wet conditions. The construction module is also used to construct a data set of input parameters, output parameters and state variables under the condition of uniform load change interval based on the variable load operation data of the coal-fired unit. The determining module is also used to determine the constraints of the unknown parameters in the state variable expression based on the operating mechanism characteristics of the coal-fired unit; and to determine the unknown parameters based on the data set and the constraints, thereby obtaining the dynamic model of the coal-fired unit under wet conditions.

[0013] Additionally, a computer-readable storage medium is provided, which stores a computer program that, when executed by a processor, implements the aforementioned method for modeling a coal-fired power unit.

[0014] Finally, a computer device is also provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described method for modeling a coal-fired power unit.

[0015] The model construction method for coal-fired power units provided by this invention has the following beneficial effects: By constructing dynamic models of multiple operating systems of the coal-fired power unit, the operating mechanism characteristics of the unit are effectively described. Based on this, a mapping relationship between input and output parameters is established, organically combining the advantages of composite modeling and data-driven modeling methods. This not only reduces the dependence on stable operating data during variable load operation of the unit but also ensures the reliability of the model. Finally, based on the operating mechanism characteristics of the unit and the data set of variable load operation, the unknown parameters in the dynamic model are calculated. Thus, the model constructed by this method not only has a reliable physical model structure and can describe the dynamic characteristics of the system but also has high dynamic accuracy. Attached Figure Description

[0016] To more clearly illustrate the embodiments and design schemes of the present invention, the accompanying drawings required for this embodiment will be briefly described below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the operation process of an ultra-supercritical coal-fired unit under wet conditions according to an exemplary embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of a coal-fired power unit provided by the present invention according to an exemplary embodiment.

[0019] Figure 3 This is a schematic flowchart of a model construction method for a coal-fired power unit provided by the present invention according to an exemplary embodiment.

[0020] Figure 4 This is a block diagram of a model building device for a coal-fired power unit according to an exemplary embodiment of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0022] The present invention pertains to a 1000MW ultra-supercritical coal-fired power unit. The unit operates under wet conditions as follows: Figure 1 As shown, as the unit power gradually decreases, the flow rate of the working fluid entering the water-cooled wall and the amount of coal fed into the furnace decrease. To maintain stable boiler hydrodynamics, the feedwater flow rate is reduced to a certain value, typically 30% of the boiler's maximum continuous evaporation capacity, and then stops decreasing. As the boiler heat load decreases, the heat absorption of the working fluid decreases, and the working fluid at the water-cooled wall outlet changes from slightly superheated steam to wet steam. To prevent water from entering the superheater, a steam-water separator separates the working fluid into steam and water; saturated steam enters the superheater, and saturated water enters the water storage tank. To recover heat from the working fluid and saturated water, the boiler water circulation pump mixes the higher-temperature water with the hot water from the high-pressure heater before it enters the economizer. This process is the wet operation process of the coal-fired unit. The wet operation process of the unit is complex. Due to the limited capacity of the water storage tank, the water level in the tank is difficult to control, which can easily lead to water entering the superheater or direct discharge of hot water from the storage tank, reducing the safety and economy of unit operation.

[0023] To improve the safety and economy of unit operation, the boiler-turbine coordination system model for once-through coal-fired units under wet conditions has four inputs: fuel quantity command. u B(kg / s), water pump flow rate D fw (kg / s), turbine control valve opening u t and circulating water flow D xh (kg / s), four output quantities, namely the economizer inlet flow rate. D sm (kg / s), unit power N e (MW), main steam pressure P st (MPa) and water level in the storage tank l (m). Figure 2 Provide the correspondence between the model input and output.

[0024] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] First, this invention provides a method for modeling coal-fired power units, specifically as follows: Figure 3 As shown, it includes the following steps: S301. Based on the input and output parameters of the coal-fired unit under wet conditions, construct dynamic models of multiple operating systems of the coal-fired unit under preset simplified conditions.

[0026] The pre-defined simplification conditions include: treating the economizer and water-cooled wall as a single-tube heating system; ensuring the superheated steam temperature is stably controlled and the desuperheating water flow is integrated into the superheater inlet flow, thus treating the superheater as a single-tube heating system; neglecting axial heat transfer between flue gas, boiler tube wall, and working fluid; and assuming the heat released by flue gas on the boiler tube wall is approximately proportional to the heat released by coal combustion. For ease of calculation, this invention equates the above conditions to: the heat released by flue gas on the boiler tube wall is proportional to the heat released by coal combustion; uniform fluid characteristics across any heating tube cross-sectional area; considering the high, medium, and low-pressure cylinders of the turbine as a single turbine system; and incorporating the reheater heat absorption into the turbine coefficient.

[0027] For example, the operating system includes a pulverizing system, an economizer and water-cooled wall system, a water storage tank system, a superheater system, and a steam turbine system.

[0028] For example, the dynamic operation of a pulverizing system can be considered as a first-order inertial plus time-delay process; therefore, the dynamic model of the pulverizing system is: .

[0029] In the formula, c 0 represents the inertial time of the powder-making system, in seconds; r B This refers to the amount of coal fed into the furnace, in kg / s. u BIt is a fuel quantity directive, in kg / s; τ The time delay in the flour milling system is expressed in seconds (s).

[0030] Due to the flow rate of the water supply pump ( D fw ) and boiler water circulation pump flow rate ( D xh The working fluid flows into the economizer from one point, therefore the economizer inlet working fluid flow rate ( D sm This can be represented as: .

[0031] In the formula, T xh It is inertial time, in seconds; D sm The economizer inlet flow rate is kg / s; D fw The flow rate of the water pump is kg / s; D xh The flow rate of the boiler water circulation pump is kg / s.

[0032] Mechanism analysis of the economizer and water-cooled wall system operation process: Based on the laws of conservation of mass and energy, a lumped parameter modeling method is adopted, with the system outlet as the lumped parameter point, to establish a dynamic model of the economizer and water-cooled wall system, namely: .

[0033] In the formula, ρ lb The density of the working fluid at the outlet of the water-cooled wall is kg / m³. 3 ; V lb For the volume of the economizer and water-cooled wall, m 3 ; D lb The outlet flow rate of the water-cooled wall is kg / s; h lb Enthalpy of the working fluid at the outlet of the water-cooled wall, kJ / kg; c j , where is the specific heat capacity of the boiler metal tube wall, kJ / (kg·℃); m j The mass of the boiler tube wall metal is expressed in kg. T j The temperature of the boiler tube wall metal is given in °C. h sm The enthalpy of the working fluid at the economizer inlet is kJ / kg; h lb Enthalpy of the working fluid at the outlet of the water-cooled wall, kJ / kg; Q 1 represents the heat absorbed by the working fluid in the economizer and water-cooled wall, in kJ / s; k1 represents the heat absorbed by the working fluid in the economizer and water-cooled wall when 1 kg of pulverized coal is burned, in kJ / (kg·s).

[0034] Based on the pre-defined simplified conditions, differentiating the steam pressure and enthalpy at the water-cooled wall outlet respectively yields: .

[0035] In the formula, p lb and h lb These represent the working fluid pressure (MPa) and enthalpy (kJ / kg) at the water-cooled wall outlet, respectively. Since the working fluid at the steam-water separator is subjected to uniform force, the working fluid pressure at the water-cooled wall outlet can be considered equal to the working fluid pressure within the steam-water separator. p lb = p m .

[0036] The above formula can be further written as: .

[0037] In the formula, b 11 = V lb ǝρ lb / ǝp m , b 12 = V lb ǝρ lb / ǝh lb , b 21 = h lb V lb ǝρ lb / ǝp m + c j m j ǝT j / ǝp m , b 22 = h lb V lb ǝ ρ lb / ǝhlb + ρ lb V lb + c j m j ǝT j / ǝh lb .

[0038] The above formula can be further written as: .

[0039] In the formula, c 1= b 21 - b 11 b 22 / b 12 , d 1= b 22 / b 12 , c 2= b 22 - b 12 b 21 / b 11 , d 1= b 21 / b 11 .

[0040] The dryness model of the working fluid at the water-cooled wall outlet can be obtained from the above formula. x lb = x ( p m , h lb Therefore, based on the law of conservation of mass, the dynamic model of the water storage tank system is established as follows:

[0041] .

[0042] Since the water tank is saturated, the mass of the working fluid in the water tank is... V L ρ L = V s ρs + V w ρ w In the formula, V s For saturated steam volume, m 3 ; ρ s The density of saturated steam is kg / m³. 3 ; V w For the saturated water volume, m 3 ; ρ w The density of saturated water is kg / m³ 3 Since the mass of saturated steam is small, the mass of the working fluid in the water storage tank can be approximated as... V L ρ L ≈ V w ρ w , V w =F H Where F is the bottom area of ​​the water storage tank, in m² 2 ; H Let be the water level in the storage tank, in meters (m). Furthermore, the density of saturated water can be expressed in terms of the working fluid pressure, i.e. ρ w = ρ ( p m Therefore, the dynamic model of the water level in the storage tank can be obtained as follows:

[0043] .

[0044] Based on the pre-defined simplified conditions, the operation process of the superheater system is analyzed by mechanism. A lumped parameter modeling method is adopted, using the system outlet as the lumped parameter point, to establish a dynamic model of the superheated steam enthalpy of the superheater system, namely: .

[0045] In the formula, ρ st Density of the working fluid at the superheater outlet, kg / m³ 3 ; V st For the superheater volume, m 3 ; D lb The outlet flow rate of the water-cooled wall is kg / s; h vbh The enthalpy of saturated steam at the superheater inlet is kJ / kg. h stThe enthalpy of the superheater outlet steam is expressed in kJ / kg. Q 2 represents the heat absorbed by the working fluid in the superheater, in kJ / s; k 2 represents the heat absorbed by the superheater working fluid during the combustion of 1 kg of pulverized coal, expressed in kJ / (kg·s). c 31 = h st V st ǝρ st / ǝh st , c 32 = ρ st V st .

[0046] Referring to the energy balance equation for the steam-water thermal storage process in the superheater zone, and combining it with the above equation, a dynamic model of the superheated steam pressure in the superheater system is established, namely: .

[0047] In the formula, p st The working fluid pressure at the superheater outlet is MPa. k 3 represents the turbine fitting coefficient, in kJ / (MPa.s); u t To set the turbine control valve opening, and let c 4= h st V st ǝρ st / ǝp st .

[0048] Based on the preset simplification conditions, the steam turbine system can be described by a first-order inertial element, i.e. .

[0049] In the formula, N e Unit power, in MW; c 5 represents the turbine's inertial time, in seconds; k 4 represents the turbine efficiency coefficient.

[0050] S302. Determine the mapping relationship between input parameters and output parameters based on multiple dynamic models, and obtain the state variable expression of the coal-fired unit based on the mapping relationship.

[0051] This state variable is used to characterize the state changes of a coal-fired unit under wet operating conditions.

[0052] For example, the state-space form of the input parameters, output parameters, and state variables of the dynamic model of a coal-fired unit under wet operating conditions is determined as follows: .

[0053] U, Y, and X are the model's input parameter matrix, output matrix, and state variable matrix, respectively, as follows: .

[0054] Therefore, the state variable expression of the coal-fired unit is obtained as follows: .

[0055] in, .

[0056] S303. Based on the variable load operation data of the coal-fired unit, construct a data set of input parameters, output parameters, and state variables under the condition of uniform load change intervals.

[0057] Based on the above state variable expressions, it can be seen that seven static parameters need to be identified in the dynamic model of the boiler-turbine coordination system. k 1, k 2, k 3, k 4, h vbh , ρ w , h sm Two nonlinear functions x lb and D lb and 11 dynamic parameters, τ , c 0, T x , c 1, d 1, c 2, d 2, c 31 , c 32 , c 4, c 5. When the unit operates under wet conditions and variable load, there are relatively few steady-state load segments. Therefore, this invention proposes a parameter identification method that integrates mechanistic characteristics, that is, using only variable load dynamic data to identify the static and dynamic parameters and nonlinear functions of the system.

[0058] In this step, a set of variable load operation data can be selected, and the intervals of unit power change can be evenly selected to roughly grasp the variation law of system parameters, determine the system variable values ​​corresponding to each unit power point, and construct a system variable data set with uniform intervals of unit power.

[0059] For example, Table 1 gives the system variable values ​​corresponding to the power points of each unit, as follows: Table 1. System variable values ​​corresponding to the power points of each unit. S304. Based on the operating mechanism characteristics of the coal-fired power unit, determine the constraints on the unknown parameters in the expression of the state variable.

[0060] For example, the heat absorption characteristics of the working fluid can be used to determine... k 1= k ( x 1) and k 2= g ( x 1); Through the analysis of Q i = k i x 1. Perform time-varying differentiation to ensure that the derivative of the heat absorbed by the working fluid remains greater than zero across the load variation range, thereby determining the unknown parameters. k 1 and k Constraints 2.

[0061] Based on the fact that the working fluid flow rates at the economizer inlet and the water-cooled wall outlet are the same, the constraint conditions are then determined. D sm = D lb .

[0062] Based on the operating mechanism characteristics of coal-fired power units, determine D lb = u t ( a 1 p m + b 1) / ( a 2 h lb + b 2).

[0063] Based on the mechanistic characteristics of wet steam and the thermodynamic properties of water vapor, a wet steam dryness fraction model is determined. x lb =( a 11 h lb + b11 ) / ( a 22 p m + b 22 ).

[0064] S305. Determine the unknown parameter based on the data set and the constraint conditions, and then obtain the dynamic model of the coal-fired unit under wet conditions.

[0065] In this step, based on the data set, regression analysis is used to determine the static parameters among the unknown parameters; based on the constraints, and combining the data set with the optimization algorithm, the dynamic parameters of each system are gradually identified.

[0066] For example, regarding the heat absorbed by the working fluid, Q 1 and Q 2. The established function needs to ensure that the heat absorption of the working fluid increases proportionally with the coal feed rate, i.e., the parameter structure needs to be determined. k 1= k ( x 1) and k 2= g ( x 1) is a system of quadratic functions in one variable. By taking the derivative of the function, we can obtain... Q i = k i x 1, i =1,2, ensuring the derivative of the heat absorbed by the working fluid remains positive at zero across the load variation range, thus satisfying the system's operating mechanism characteristics; otherwise, reselect data and identify parameters. k 1 and k 2. Based on the system variable data set, use regression analysis to identify static parameters. k 3, k 4, h vbh and ρ w When the unit is operating under varying loads, it is approximately assumed that the working fluid flow rate at the economizer inlet is approximately equal to the working fluid flow rate at the water-cooled wall outlet. D sm ≈ D lb For ease of calculation, this invention equates the economizer inlet working fluid flow rate with the water-cooled wall outlet working fluid flow rate, i.e. D sm = D lb Based on the analysis of mechanistic characteristics, the function structure is determined to be as follows: D lb = u t (a 1 p m + b 1) / ( a 2 h lb + b 2) Since the working fluid at the outlet of the water-cooled wall is in a wet steam state, a wet steam dryness model is determined by combining the wet steam mechanism characteristics and steam thermodynamic properties software. x lb =( a 11 h lb + b 11 ) / ( a 22 p m + b 22 For dynamic parameters, the dynamic parameters of each system are gradually identified by combining operational data and optimization algorithms.

[0067] To further clarify the parameter identification process, this invention also selects a dynamic running data set based on the parameter identification method of fusion mechanism characteristics, as shown in Table 1 above.

[0068] Based on the above state variable expression, the static parameter equation is determined as follows: .

[0069] .

[0070] .

[0071] .

[0072] For static parameters, the parameters are determined by combining parameter identification methods, operating data, and the thermodynamic properties of water vapor. h vbh and ρ w , h sm Take it as a constant, that is: .

[0073] .

[0074] .

[0075] .

[0076] .

[0077] .

[0078] Finally, by combining the running data and taking the average, we can obtain... h sm =1118.2kJ / kg.

[0079] For nonlinear functions, combining the running data and the parameter identification methods described above, identification can be achieved. D lb and x lb ,Right now: .

[0080] .

[0081] For dynamic parameters, this study combines dynamic operational data with parameter identification methods based on fusion mechanism characteristics, employing an immune genetic algorithm to sequentially identify system parameters, as follows: .

[0082] In addition, the present invention also verified the dynamic model. Since this set of data does not contain multiple steady-state data segments, only dynamic verification of the model is required. The selected data range is 50MW-350MW, used to describe the large-scale load variation operation process of the boiler-generator coordination system of a once-through coal-fired unit under wet conditions, with a sampling time of 1s.

[0083] Under wet operating conditions, ranging from 50MW to 350MW, and with varying loads, the simulated values ​​from the model closely track the actual operating values, exhibiting the same trend. The average relative error of the system output variables is less than 7.8%, and the system output... p st , D sm , H , N e The root mean square errors are less than 0.3 MPa, 1.4 kg / s, 0.25 m, and 20.7 MW, respectively. The results indicate that the established model can accurately describe the large-scale variable load operation process of the boiler-turbine coordination system under wet conditions.

[0084] Simulation of the dynamic model reveals that as the amount of pulverized coal in the boiler increases, the boiler furnace heat load increases, and the working fluid in the economizer and water-cooled walls absorbs more heat, generating more saturated steam. Therefore, the main steam pressure and unit power gradually increase. Since the feedwater pump flow rate and the boiler water circulation pump flow rate remain constant, the working fluid flow rate at the economizer inlet remains constant. Due to the increased boiler heat load, the dryness of the working fluid at the water-cooled wall outlet increases, reducing the amount of working fluid entering the water storage tank. Consequently, the water level in the water storage tank gradually decreases to zero meters.

[0085] As the feedwater pump flow rate increases dramatically, the flow rate of the working fluid entering the economizer immediately increases. This compresses the working fluid in the economizer and water-cooled walls, while the coal feed rate remains constant. The total mass of the working fluid in the economizer and water-cooled walls increases, causing fluctuations in the working fluid flow rate at the water-cooled wall outlet, resulting in slight fluctuations in the main steam pressure and unit power. Furthermore, the increased feedwater pump flow rate leads to a larger mass of working fluid stored in the economizer and water-cooled walls. Consequently, the steam dryness at the water-cooled wall outlet decreases, increasing the flow rate of the working fluid entering the water storage tank. However, the boiler water circulation pump flow rate remains constant, causing the water level in the storage tank to gradually rise to its maximum level.

[0086] As the flow rate of the boiler water circulation pump increases dramatically, the flow rate of the working fluid at the economizer inlet also increases immediately. This compresses the working fluid in the economizer and water-cooled walls. With the coal feed rate remaining constant, the total mass of the working fluid in the economizer and water-cooled walls increases, causing fluctuations in the working fluid flow rate at the water-cooled wall outlet. This results in slight fluctuations in the main steam pressure and unit power. Regarding the water level in the storage tank, a dramatic increase in the boiler water circulation pump flow rate initially lowers the water level. However, as the feedwater flow rate into the economizer inlet increases, the steam dryness at the water-cooled wall outlet decreases, leading to an increase in the flow rate of the working fluid entering the storage tank. Consequently, the water level in the storage tank gradually rises to its maximum value.

[0087] As the turbine control valve opening decreases abruptly, the main steam flow area shrinks, leading to a gradual increase in main steam pressure. Since the feedwater pump flow rate and boiler water circulation pump flow rate remain constant, the working fluid flow rate at the economizer inlet remains unchanged. This abrupt increase in main steam flow rate increases the mass stored in the boiler tubes, causing an immediate decrease in superheated steam flow rate and thus an immediate drop in unit power. However, with the coal feed rate remaining constant, the superheated steam flow rate gradually increases and remains constant as the main steam pressure stabilizes, allowing the unit power to gradually recover to a stable value. Regarding the water tank level, the sudden decrease in control valve opening leads to a reduction in working fluid flow rate. Consequently, the working fluid flow rate at the water-cooled wall outlet decreases, resulting in a decrease in the working fluid flow rate entering the water tank, causing the water tank level to gradually decrease. As the boiler steam pressure increases, the steam dryness gradually decreases, causing the saturated water entering the water tank to gradually rise, thus gradually increasing the water level in the tank to its maximum value.

[0088] This invention, based on the laws of conservation of mass and energy, analyzes the operation process of a once-through coal-fired unit under wet conditions. Using a lumped parameter method, a dynamic model of the boiler-machine coordination system of the once-through coal-fired unit under wet conditions is established. A parameter identification method incorporating system characteristics is proposed to determine the model parameters and functions. Dynamic accuracy verification and open-loop simulation experiments show that the model can describe the variable load operation process of a once-through coal-fired unit in the 50MW-350MW range under wet conditions, with an average relative error of less than 7.8%.

[0089] By employing the above method, dynamic models of multiple operating systems of a coal-fired power unit are constructed separately, effectively describing the unit's operating mechanism characteristics. Based on this, a mapping relationship between input and output parameters is established, organically combining the advantages of composite modeling and data-driven modeling methods. This not only reduces reliance on stable operating data during variable load operation but also ensures model reliability. Finally, based on the unit's operating mechanism characteristics and the variable load operating data set, unknown parameters in the dynamic model are calculated. Thus, the model constructed using this method not only possesses a reliable physical model structure and can describe the system's dynamic characteristics but also exhibits high dynamic accuracy.

[0090] Secondly, the present invention also provides a model building device for coal-fired power units, such as... Figure 4 As shown, it includes: Module 401 is used to construct dynamic models of multiple operating systems of a coal-fired unit under preset simplified conditions based on the input and output parameters of the coal-fired unit under wet operating conditions. The determination module 402 is used to determine the mapping relationship between input parameters and output parameters based on multiple dynamic models, and to obtain the state variable expression of the coal-fired unit based on the mapping relationship; the state variable is used to characterize the state change of the coal-fired unit under wet conditions. The construction module 401 is also used to construct a data set of input parameters, output parameters and state variables under the condition of uniform load change interval based on the variable load operation data of the coal-fired unit. The determining module 402 is further configured to determine the constraints of the unknown parameters in the state variable expression based on the operating mechanism characteristics of the coal-fired power unit; determine the unknown parameters based on the data set and the constraints, and thus obtain the dynamic model of the coal-fired power unit under wet operating conditions.

[0091] Using the aforementioned apparatus, dynamic models of multiple operating systems of a coal-fired power unit are constructed, effectively describing the unit's operating mechanism characteristics. Based on this, a mapping relationship between input and output parameters is established, organically combining the advantages of composite modeling and data-driven modeling methods. This not only reduces reliance on stable operating data during variable load operation but also ensures model reliability. Finally, based on the unit's operating mechanism characteristics and the variable load operating data set, unknown parameters in the dynamic model are calculated. Thus, the model constructed using this method not only possesses a reliable physical model structure and can describe the system's dynamic characteristics but also exhibits high dynamic accuracy.

[0092] The present invention also provides a computer-readable storage medium storing a computer program that can be used to execute the above-described... Figure 3 The steps of the provided coal-fired power unit model construction method.

[0093] This invention also provides a computer device. At the hardware level, the computer device includes a processor, an internal bus, a network interface, memory, and non-volatile memory, and may also include other hardware required for various operations. The processor reads the corresponding computer program from the non-volatile memory into memory and then executes it to achieve the above-mentioned functions. Figure 3 The steps of the provided coal-fired power unit model construction method.

[0094] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0095] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, as well as combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0096] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0097] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0098] It should be noted that the above specific embodiments enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. Therefore, although the present invention has been described in detail in this specification, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention are covered within the protection scope of the patent of the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for modeling a coal-fired power unit, characterized in that, The method includes: Based on the input and output parameters of the coal-fired power unit under wet operating conditions, dynamic models of multiple operating systems of the coal-fired power unit under preset simplified conditions are constructed respectively; the multiple operating systems include a water storage tank system; the dynamic model of the water storage tank system is as follows: ； in, V L For the volume of the water storage tank, ρ L The density of the working fluid in the water storage tank. x lb The dryness of the steam at the water-cooled wall outlet. D lb This refers to the outlet flow rate of the water-cooled wall. D xh The circulating water flow rate is [value missing]; the water storage tank is saturated, and the mass of the working fluid in the water storage tank is: V L ρ L = V s ρ s + V w ρ w In the formula, V s This represents the volume of saturated steam. ρ s The density is the saturated vapor density. V w This represents the volume of saturated water. ρ w This is the density of saturated water; The mass of the working fluid in the water tank is approximated to the mass of saturated water, and the volume of saturated water is... V w =F H Where F is the bottom area of ​​the water storage tank. H Given the water level in the storage tank, the dynamic model of the water level in the storage tank is as follows: ； The mapping relationship between input and output parameters is determined based on multiple dynamic models, and the state variable expression of the coal-fired unit is obtained based on the mapping relationship; the state variable is used to characterize the state change of the coal-fired unit under wet conditions. Based on the variable load operation data of the coal-fired unit, a data set of input parameters, output parameters and state variables is constructed under the condition of uniform load change intervals. Based on the operating mechanism characteristics of coal-fired power units, determine the constraints on the unknown parameters in the state variable expressions; The unknown parameters are determined based on the data set and the constraints, thereby obtaining a dynamic model of the coal-fired unit under wet operating conditions.

2. The method for model construction of a coal-fired power unit according to claim 1, characterized in that, The operating system includes a pulverizing system, an economizer and water-cooled wall system, a water storage tank system, a superheater system, and a steam turbine system; the dynamic models of the multiple operating systems include: The dynamic model of the powder-making system is as follows: ； in, c 0 represents the inertia time of the powder-making system; r B This refers to the amount of coal fed into the furnace. u B It is a fuel quantity directive; τ This indicates the time delay in the flour milling system; t It is a time variable; The dynamic model of the economizer and water-cooled wall system is as follows: ； in, ρ lb The density of the working fluid at the outlet of the water-cooled wall; V lb For the volume of the economizer and water-cooled wall; D lb This refers to the outlet flow rate of the water-cooled wall. D sm The economizer inlet flow rate; h lb This refers to the enthalpy of the working fluid at the outlet of the water-cooled wall. c j This refers to the specific heat capacity of the boiler's metal tube wall. m j For the metal quality of the boiler tube wall; T j This refers to the metal temperature of the boiler tube wall. h sm The enthalpy value of the working fluid imported into the economizer; Q 1 represents the heat absorbed by the working fluid in the economizer and water-cooled wall; k 1 represents the heat absorbed by the working fluid in the economizer and water-cooled wall when 1 kg of pulverized coal is burned. The dynamic model of the superheater system includes a dynamic model of the superheated steam enthalpy and a dynamic model of the superheated steam pressure. The dynamic model of the superheated steam enthalpy of the superheater system is as follows: ； The dynamic model of superheated steam pressure in the superheater system is as follows: ； in, ρ st The density of the working fluid at the superheater outlet; V st This refers to the volume of the superheater; D lb This refers to the outlet flow rate of the water-cooled wall. h vbh The enthalpy of saturated steam at the superheater inlet; h st This refers to the enthalpy of the steam at the superheater outlet. Q 2 represents the heat absorbed by the working fluid in the superheater; k 2 represents the heat absorbed by the superheater working fluid when 1 kg of pulverized coal is burned; p st The working fluid pressure at the superheater outlet; k 3 represents the turbine fitting coefficient; u t For the turbine control valve opening; The dynamic model of the steam turbine system is as follows: ； in, N e For unit power; c 5 represents the turbine's inertial time; k 4 represents the turbine efficiency coefficient.

3. The method for model construction of a coal-fired power unit according to claim 2, characterized in that, The process of determining the mapping relationship between input parameters and output parameters based on multiple dynamic models includes: The state-space form of the input parameters, output parameters, and state variables of the dynamic model of a coal-fired power unit under wet operating conditions is determined as follows: ； U , Y and X These are the model's input parameter matrix, output matrix, and state variable matrix, respectively. A (•), B (•), C (•) represents a matrix function, specifically: ， in, D fw To increase the outlet water flow rate; u t For the turbine control valve opening; H This refers to the water level in the storage tank. p m This refers to the steam pressure of the steam-water separator.

4. The method for model construction of a coal-fired power unit according to claim 3, characterized in that, The expression for the state variable is: ； in, T x For the recycle inertia time; c 1 and c 2 represents the inertial time of steam pressure and enthalpy in the economizer and water-cooled wall system; d 1 and d 2 represents the dynamic parameters in the economizer and water-cooled wall system; c 31 and c 32 The inertial time coefficient of the superheated steam temperature system; c 4 represents the heat storage coefficient of the superheater; c 5 represents the inertial time of the steam turbine generator system; ρ w The density of saturated water in the storage tank; F This refers to the bottom area of ​​the water storage tank.

5. The method for constructing a model of a coal-fired power unit according to claim 4, characterized in that, Based on the operating mechanism characteristics of coal-fired power units, the constraints on the unknown parameters in the state variable expressions include: Based on the heat absorption characteristics of the working fluid, determine k 1= k ( x 1) and k 2= g ( x 1); Through the analysis of Q i = k i x 1. Perform time-varying differentiation to ensure that the derivative of the heat absorbed by the working fluid remains greater than zero across the load variation range, thereby determining the unknown parameters. k 1 and k 2. Constraints; Based on the fact that the working fluid flow rates at the economizer inlet and the water-cooled wall outlet are the same, the constraint conditions are then determined. D sm = D lb ; Based on the operating mechanism characteristics of coal-fired power units, determine D lb = u t ( a 1 p m + b 1) / ( a 2 h lb + b 2), of which a 1, a 2, b 1, b 2 is an unknown parameter; Based on the mechanistic characteristics of wet steam and the thermodynamic properties of water vapor, a wet steam dryness fraction model is determined. x lb =( a 11 h lb + b 11 ) / ( a 22 p m + b 22 ),in a 11 , a 22 , b 11 , b 22 The parameter is unknown.

6. The method for model construction of a coal-fired power unit according to claim 1, characterized in that, Determine the unknown parameters based on the data set and the constraints: Based on the data set, regression analysis was used to determine the static parameters among the unknown parameters; Based on the constraints, and by combining the data set with the immune genetic optimization algorithm, the dynamic parameters in the unknown parameters of each system model are gradually identified.

7. The method for model construction of a coal-fired power unit according to claim 1, characterized in that, The preset simplification conditions include: The economizer and water-cooled wall are considered as a single heat-receiving tube system; The temperature of the superheated steam can be stably controlled, and the flow rate of the desuperheating water is integrated into the inlet flow rate of the superheater, thus treating the superheater as a single-tube heating system. Axial heat transfer between flue gas, boiler tube walls and working fluid is ignored; The heat released by flue gas on the boiler tube wall is directly proportional to the heat released by coal combustion. The fluid characteristics are uniform across any cross-sectional area of ​​the heated tube; The high-pressure, intermediate-pressure, and low-pressure cylinders of a steam turbine are considered as a single steam turbine system. The heat absorbed by the reheater is factored into the turbine coefficient.

8. A model building device for a coal-fired power unit, characterized in that, The apparatus, applied to the method of claim 1, comprises: The module is used to construct dynamic models of multiple operating systems of a coal-fired power unit under preset simplified conditions, based on the input and output parameters of the coal-fired power unit under wet operating conditions. The determination module is used to determine the mapping relationship between input parameters and output parameters based on multiple dynamic models, and to obtain the state variable expression of the coal-fired unit based on the mapping relationship; the state variable is used to characterize the state change of the coal-fired unit under wet conditions. The construction module is also used to construct a data set of input parameters, output parameters and state variables under the condition of uniform load change interval based on the variable load operation data of the coal-fired unit. The determining module is also used to determine the constraints of the unknown parameters in the state variable expression based on the operating mechanism characteristics of the coal-fired unit; and to determine the unknown parameters based on the data set and the constraints, thereby obtaining the dynamic model of the coal-fired unit under wet conditions.

9. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements the method described in any one of claims 1 to 7.

10. A computer device, characterized in that, The method includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method described in any one of claims 1 to 7.

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