Model construction method and device of coal-fired unit, computer equipment and medium

Abstract

The invention provides a model construction method and device for a coal-fired unit, computer equipment and a medium, and belongs to the field of energy optimization, and the method comprises the steps: respectively constructing dynamic models of a plurality of operation systems of the coal-fired unit based on a preset simplification condition; determining a mapping relation between the input parameters and the output parameters according to the plurality of dynamic models, and obtaining a state variable expression of the coal-fired unit according to the mapping relation; according to the variable load operation data of the coal-fired unit, constructing a data set of input parameters, output parameters and state variables under the condition of uniform load interval; determining constraint conditions of unknown parameters in the state variable expression according to operating mechanism characteristics of the coal-fired unit; and determining the unknown parameters according to the data set and the constraint condition, and further obtaining a dynamic model of the coal-fired unit under the wet condition. Therefore, the model constructed by the method not only has a reliable physical model structure and can describe the dynamic characteristics of the system, but also has relatively high dynamic precision.

Description

Technical Field

[0001] The present invention belongs to the field of energy optimization, and in particular relates to a model building method, device, computer equipment and medium for a coal-fired unit. Background Art

[0002] Variable load operation of a once-through coal-fired unit under wet conditions can compromise the safety characteristics of the boiler water circulation and the stability of the water-cooled wall. Furthermore, due to the small capacity of the unit's water storage tank, variable load operation can cause significant fluctuations in the tank water level, which can easily lead to water carryover from the superheater inlet steam, compromising superheater safety. Therefore, it is necessary to establish a dynamic model of the boiler-turbine coordination system for once-through coal-fired units under wet conditions. This model reflects the dynamic characteristics of the system's operation under wet conditions and can be used in control system design to enhance the operational flexibility and safety of once-through coal-fired units under wet conditions.

[0003] Currently, the main dynamic modeling methods for the coordinated system of DC coal-fired units include composite modeling and data-driven modeling. The composite modeling method uses physical conservation laws and mechanistic analysis of the system's operating process to establish the physical structure of the system model. The system model functions and parameters are then identified using operating data. However, in the composite modeling method, the model parameters and functions must be obtained by combining multiple sets of steady-state operating data and regression analysis. However, when the unit operates under variable load, it is difficult to obtain multiple sets of stable operating data, which limits the use of this method. The data-driven modeling method combines the unit's dynamic operating data with intelligent modeling methods such as neural networks and fuzzy systems to establish the system model. However, due to the lack of mechanistic analysis in this modeling method, the reliability of the model structure is relatively low. Therefore, there is currently a lack of practical, feasible, and highly accurate modeling methods for modeling DC coal-fired units under wet conditions. Summary of the Invention

[0004] In order to solve the problem of lack of practical, feasible and highly accurate modeling method for DC furnace coal-fired units under wet conditions, the present invention provides a model construction method, device, computer equipment and medium for coal-fired units.

[0005] In order to achieve the above object, the present invention provides the following technical solutions: First, a method for building a model of a coal-fired unit is provided, the method comprising: According to the input parameters and output parameters of the coal-fired unit under wet operating conditions, dynamic models of multiple operating systems of the coal-fired unit under preset simplified conditions are constructed respectively; Determining a mapping relationship between input parameters and output parameters based on multiple dynamic models, and obtaining a 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 working conditions; According to 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 changes; Determining the constraints of unknown parameters in the state variable expression according to the operating mechanism characteristics of the coal-fired unit; The unknown parameters are determined according to the data group and the constraint conditions, thereby obtaining a dynamic model of the coal-fired unit under wet working 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; and the dynamic models of the multiple operating systems include: The dynamic model of the milling system is: ; in, c 0 is the inertia time of the milling system; r B is the amount of coal fed into the furnace; u B is the fuel quantity command; τ Indicates the time delay in the milling system; t is a time variable; The dynamic model of the economizer and water wall system is: ; in, ρ lb is the working fluid density at the water wall outlet; V lb is the volume of economizer and water wall; D lb is the water wall outlet flow rate; h lb is the enthalpy of the working medium at the water wall outlet; c j is the specific heat capacity of the boiler metal tube wall; m j is the metal quality of the boiler tube wall; T j is the metal temperature of the boiler tube wall; h sm is the enthalpy of the working fluid at the economizer inlet; Q 1 is the amount of heat absorbed by the working medium in the economizer and water-cooled wall; k 1 is the heat absorbed by the working medium 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: ; in, V H is the volume of the water storage tank, ρH is the density of the working fluid in the water storage tank, x lb is the steam quality at the water wall outlet, D xh is the circulating water flow rate; The dynamic model of the superheater system includes a dynamic model of superheated steam enthalpy of the superheater system and a dynamic model of superheated steam pressure of the superheater system; The dynamic model of superheated steam enthalpy in the superheater system is: ; The dynamic model of superheated steam pressure in the superheater system is: ; in, ρ st is the working fluid density at the superheater outlet; V st is the superheater volume; D lb is the water wall outlet flow rate; h vbh is the enthalpy of saturated steam at the superheater inlet; h st is the steam enthalpy at the superheater outlet; Q 2 is the amount of heat absorbed by the working medium in the superheater; k 2 is the heat absorbed by the superheater working medium when 1 kg of pulverized coal is burned; p st is the working medium pressure at the superheater outlet; k 3 is the turbine fitting coefficient; u t Adjust the valve opening for the steam turbine; The dynamic model of the steam turbine system is: ; in, N e is the unit power; c 5 is the inertia time of the steam turbine; k 4 is the turbine efficiency coefficient.

[0007] Optionally, determining a mapping relationship between input parameters and output parameters according to multiple dynamic models includes: The state space form of the input parameters, output parameters and state variables of the dynamic model of the coal-fired unit under wet conditions is determined as follows: ; U 、 Y and X are the input parameter matrix, output matrix and state variable matrix of the model respectively, A (•),B (•), C (•) is a matrix function, specifically: ; in, D fw is the outlet water flow of the high pressure heater; u t Adjust the valve opening for the steam turbine; H is the water level in the water storage tank; p m is the steam pressure of the steam-water separator.

[0008] Optionally, the state variable expression is: ; in, T x is the recirculation inertia time; c 1 and c 2 is the inertia time of steam pressure and enthalpy in the economizer and water wall system; d 1 and d 2 is the dynamic parameter in the economizer and water wall system; c 31 and c 32 is the inertia time coefficient of the superheated steam temperature system; c 4 is the superheater heat storage coefficient; c 5 is the inertia time of the steam turbine generator system; ρ w is the density of saturated water in the water storage tank; F is the bottom area of ​​the water storage tank.

[0009] Optionally, according to the operating mechanism characteristics of the coal-fired unit, the constraint conditions for determining 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 Q i = k i x 1. Take the time derivative so that the derivative of the heat absorbed by the working medium is continuously greater than zero within the load variation range, and then determine the unknown parameters. k 1 and k 2 constraints; Based on the fact that the working fluid flow rate at the economizer inlet is the same as the working fluid flow rate at the water wall outlet, the constraint conditions are determined. D sm= D lb ; Based on the operating mechanism characteristics of coal-fired units, determine D lb = u t ( a 1 p m + b 1) / ( a 2 h lb + b 2), where a 1, a 2, b 1, b 2 is an unknown parameter; Combining the wet steam mechanism characteristics and water vapor thermodynamic properties, determine the wet steam dryness model x lb =( a 11 h lb + b 11 ) / ( a 22 p m + b 22 ),in a 11 , a 22 , b 11 , b 22 is an unknown parameter.

[0010] Optionally, the unknown parameters are determined according to the data set and the constraint conditions: Determine static parameters among the unknown parameters using a regression analysis method based on the data set; According to the constraints, the data set is combined with the immune genetic optimization algorithm to gradually identify the dynamic parameters of the unknown parameters of each system model.

[0011] Optionally, the preset simplified conditions include: Treat the economizer and water wall as a single heated tube system; The superheated steam temperature can be stably controlled, and the desuperheating water flow is integrated into the superheater inlet flow, and the superheater is regarded as a single-tube heating system; Ignore the axial heat transfer between the flue gas, boiler tube wall and working medium; The amount of heat released by flue gas to the boiler tube wall is proportional to the heat released by coal combustion; The fluid characteristics are uniform over any cross-sectional area of ​​the heated tube; The high, medium and low pressure cylinders of the steam turbine are regarded as a steam turbine system; The heat absorbed by the reheater is converted into the turbine coefficient.

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

[0013] In addition, a computer-readable storage medium is provided, wherein the storage medium stores a computer program, and when the computer program is executed by a processor, the above-mentioned method for constructing a model of a coal-fired unit is implemented.

[0014] Finally, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned method for constructing a model of a coal-fired unit when executing the program.

[0015] The model construction method of the coal-fired unit provided by the present invention has the following beneficial effects: By constructing dynamic models of multiple operating systems of coal-fired units separately, the operating mechanism characteristics of the unit are effectively described, and on this basis, the mapping relationship between input parameters and output parameters is constructed, and the advantages of the composite modeling method and the data-driven modeling method are organically combined. 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 group of variable load operation, the unknown parameters in the dynamic model are calculated. In this way, the model constructed by this method not only has a reliable physical model structure, can describe the dynamic characteristics of the system, but also has high dynamic accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more clearly illustrate the embodiments of the present invention and its design, the following briefly introduces the drawings required for this embodiment. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive 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 model of a coal-fired unit provided according to an exemplary embodiment of the present invention.

[0019] Figure 3 The present invention is a flow chart of a method for constructing a model of a coal-fired unit according to an exemplary embodiment of the present invention.

[0020] Figure 4 The present invention provides a block diagram of a model building device for a coal-fired unit according to an exemplary embodiment. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the technical solution of the present invention and to be able to implement it, the present invention is 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 solution of the present invention and are not intended to limit the scope of protection of the present invention.

[0022] The present invention is implemented on a 1000MW ultra-supercritical coal-fired unit. Figure 1 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 boiler decrease. To maintain boiler hydrodynamic stability, the feedwater flow rate is reduced to a certain value, generally 30% of the boiler's maximum continuous evaporation rate, and then no longer decreases. As the boiler heat load decreases, the heat absorbed by 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, with saturated steam entering the superheater and saturated water entering the water storage tank. To recover heat from the working fluid and saturated water, the boiler water circulating pump mixes the higher-temperature water with hot water from the high-pressure heater before feeding it into the economizer. This process is known as wet-state operation for coal-fired units. Wet-state operation 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 intrusion into the superheater or direct discharge of hot water from the storage tank, compromising unit safety and economic efficiency.

[0023] In order to improve the safety and economy of the unit operation, the boiler-turbine coordination system model of the DC coal-fired unit under wet working conditions has four input quantities, namely the fuel quantity command u B(kg / s), water pump flow rate D fw (kg / s), turbine valve opening u t and circulating water flow D xh (kg / s), four output quantities, namely economizer inlet flow D sm (kg / s), unit power N e (MW), main steam pressure P st(MPa) and water level in the water tank l (m). Figure 2 Give the corresponding relationship between the model input and output.

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

[0025] First, the present invention provides a method for constructing a model of a coal-fired unit, specifically Figure 3 As shown, the following steps are included: S301. Based on the input parameters and output parameters of the coal-fired unit under wet operating conditions, dynamic models of multiple operating systems of the coal-fired unit under preset simplified conditions are constructed respectively.

[0026] Among them, the preset simplified conditions include: the economizer and water-cooled wall are regarded as a single heated tube system; the superheated steam temperature can be stably controlled, and the cooling water flow rate is integrated into the superheater inlet flow rate, and the superheater is regarded as a single-tube heating system; the axial heat transfer between the flue gas, boiler tube wall and working medium is ignored; the heat release of the flue gas to the boiler tube wall is approximately proportional to the heat released by coal combustion. For the convenience of calculation, the present invention here equates the above conditions to: the heat release of the flue gas to the boiler tube wall is proportional to the heat released by coal combustion; the fluid characteristics are uniform over any cross-sectional area of ​​the heated tube; the high, medium and low pressure cylinders of the turbine are regarded as a turbine system; the heat absorption of the reheater is converted into the turbine coefficient.

[0027] Illustratively, 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 process of the milling system can be regarded as a first-order inertia plus time delay link, so the dynamic model of the milling system is: .

[0029] Where, c 0 is the inertia time of the milling system, s; r B is the amount of coal fed into the furnace, kg / s; u Bis the fuel quantity command, kg / s; τ Represents the time delay in the milling system, s.

[0030] Due to the feed water pump flow ( D fw ) and boiler water circulation pump flow ( D xh ), converge into one place and enter the economizer, so the working medium flow rate at the economizer inlet ( D sm ) can be expressed as: .

[0031] Where, T xh is the inertia time, s; D sm is the economizer inlet flow rate, kg / s; D fw is the flow rate of the water pump, kg / s; D xh is the flow rate of boiler water circulation pump, kg / s.

[0032] The mechanism analysis of the operation process of the economizer and water-cooled wall system is carried out. According to the law of conservation of mass and energy, the lumped parameter modeling method is adopted. The system outlet is used as the lumped parameter point to establish the dynamic model of the economizer and water-cooled wall system, namely: .

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

[0034] According to the preset simplified conditions, the steam pressure and enthalpy at the water wall outlet are derived respectively, and we can get: .

[0035] Where, p lb and h lb are the working fluid pressure (MPa) and enthalpy (kJ / kg) at the water wall outlet respectively; since the working fluid at the steam-water separator is subjected to uniform force, the working fluid pressure at the water wall outlet can be considered to be equal to the working fluid pressure at the steam-water separator, that is, p lb = p m .

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

[0037] Where, 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 ǝρ lb / ǝh lb + ρ lb V lb + c j m j ǝT j / ǝh lb .

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

[0039] Where, 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] According to the above formula, the working medium dryness model at the water wall outlet can be obtained: x lb = x ( p m , h lb ). Therefore, according to 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 in a saturated state, the quality of the working fluid in the water tank is V H ρ H = V s ρ s +V w ρ w , where V s is the volume of saturated steam, m 3 ; ρ s is the saturated steam density, kg / m 3 ; V w is the saturated water volume, m 3 ; ρ w is the saturated water density, kg / m 3 Since the mass of saturated steam is small, the mass of the working medium in the water tank can be approximated as V H ρ H ≈ V w ρ w , V w =F H , where F is the bottom area of ​​the water tank, m 2 ; H is the height of the water tank, m. In addition, the saturated water density can be expressed by the working fluid pressure, that is, ρ w = ρ ( p m ), so the water level dynamic model of the water storage tank is as follows:

[0043] .

[0044] Based on the preset simplified conditions, the operation process of the superheater system is analyzed by mechanism. The lumped parameter modeling method is adopted, and the system outlet is used as the lumped parameter point to establish the dynamic model of the superheated steam enthalpy of the superheater system, namely: .

[0045] Where, ρ st is the working medium density at the superheater outlet, kg / m 3 ; V st is the superheater volume, m 3 ; D lb is the water wall outlet flow rate, kg / s; h vbh is the saturated steam enthalpy at the superheater inlet, kJ / kg; h st is the steam enthalpy at the superheater outlet, kJ / kg;Q 2 is the heat absorption of the working medium in the superheater, kJ / s; k 2 is the heat absorbed by the superheater working medium when 1 kg of pulverized coal is burned, 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 of the steam-water heat storage process in the volume area, combined with the above formula, a dynamic model of the superheated steam pressure of the superheater system is established, namely: .

[0047] Where, p st is the working fluid pressure at the superheater outlet, MPa; k 3 is the turbine fitting coefficient, kJ / (MPa.s); u t is the turbine valve opening, and c 4= h st V st ǝρ st / ǝp st .

[0048] According to the preset simplified conditions, the steam turbine system can be described by a first-order inertia link, that is, .

[0049] Where, N e is the unit power, MW; c 5 is the inertia time of the steam turbine, s; k 4 is the turbine efficiency coefficient.

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

[0051] Among them, this state variable is used to characterize the state change of the coal-fired unit under wet conditions.

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

[0053] U, Y, and X are the input parameter matrix, output matrix, and state variable matrix of the model, respectively. Specifically: .

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

[0055] in, .

[0056] S303: Construct a data set of input parameters, output parameters and state variables under the condition of uniform load variation based on the variable load operation data of the coal-fired unit.

[0057] Based on the above state variable expressions, it can be seen that 7 static parameters need to be identified in the dynamic model of the turbine-boiler 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 is running under variable load in wet conditions, there are relatively few steady-state load segments. Therefore, the present invention proposes a parameter identification method that integrates mechanism characteristics, i.e., 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 unit power change interval points can be evenly selected to roughly grasp the change law of system parameters, determine the system variable values ​​corresponding to each unit power point, and construct a system variable data group with evenly spaced 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 each unit power point S304. Determine the constraints of the unknown parameters in the state variable expression according to the operating mechanism characteristics of the coal-fired unit.

[0060] For example, based on the heat absorption characteristics of the working medium, it can be determined k 1= k ( x 1) and k 2= g ( x 1); through Q i = k i x 1. Take the time derivative so that the derivative of the heat absorbed by the working medium is continuously greater than zero within the load variation range, and then determine the unknown parameters. k 1 and k 2 constraints.

[0061] Based on the fact that the working fluid flow rate at the economizer inlet is the same as the working fluid flow rate at the water wall outlet, the constraint conditions are determined. D sm = D lb .

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

[0063] Combining the wet steam mechanism characteristics and water vapor thermodynamic properties, determine the wet steam dryness model 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 condition, and then obtain a dynamic model of the coal-fired unit under wet operating conditions.

[0065] In this step, the static parameters of the unknown parameters are determined based on the data set using a regression analysis method; and the dynamic parameters of each system are gradually identified based on the constraints, combining the data set with an optimization algorithm.

[0066] For example, for the heat absorbed by the working fluid, Q 1 and Q 2. The function established needs to ensure that the heat absorption of the working medium increases in direct proportion to the amount of coal fed, that is, to determine the parameter structure. k 1= k ( x 1) and k 2= g ( x 1), is a quadratic function group, by taking the derivative of the function, that is Q i = k i x 1, i =1,2, so that the derivative of the working medium heat absorption is continuously greater than zero in the load variation range, satisfying the system operation mechanism characteristics, otherwise reselect the data and identify the parameters k 1 and k 2. Based on the system variable data set, use regression analysis method to identify static parameters k 3. k 4. h vbh and ρ w When the unit is running at variable load, it is assumed that the flow rate of the working medium at the economizer inlet is approximately equal to the flow rate of the working medium at the water wall outlet, that is, D sm ≈ D lb For the convenience of calculation, the present invention equates the working medium flow rate at the economizer inlet with the working medium flow rate at the water wall outlet, that is, D sm = D lb According to the analysis of mechanism characteristics, the function structure is determined to be D lb = u t (a 1 p m + b 1) / ( a 2 h lb + b 2) Since the working medium at the outlet of the water wall is in a wet steam state, the wet steam dryness model is determined by combining the wet steam mechanism characteristics and the water vapor thermodynamic properties software. x lb =( a 11 h lb + b 11 ) / ( a 22 p m + b 22 ); For dynamic parameters, the operating data and optimization algorithm are combined to gradually identify the dynamic parameters of each system.

[0067] In order to further clarify the parameter identification process, the present invention also selects a dynamic operation data set based on the parameter identification method of the fusion mechanism characteristics, as shown in Table 1 above.

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

[0069] .

[0070] .

[0071] .

[0072] For static parameters, the parameter identification method, operating data and water vapor thermodynamic properties are combined to determine h vbh and ρ w , h sm Take it as a constant, that is: .

[0073] .

[0074] .

[0075] .

[0076] .

[0077] .

[0078] Finally, combined with the running data, taking the average, we can get h sm =1118.2kJ / kg.

[0079] For nonlinear functions, combining the operating data and the above parameter identification method, it can be identified D lb and x lb ,Right now: .

[0080] .

[0081] For dynamic parameters, this study combines dynamic operation data with the parameter identification method of fusion mechanism characteristics, and uses the immune genetic algorithm to identify system parameters in sequence, as follows: .

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

[0083] When the unit is in wet working condition, 50MW-350MW, and variable load operation, the model simulation value can track the actual operation value well and has the same change trend. The average relative error of the system output variables is less than 7.8%, and the system output is p st , D sm , H , N e The root mean square errors of the proposed model are less than 0.3 MPa, 1.4 kg / s, 0.25 m, and 20.7 MW, respectively. The results show that the proposed model can accurately describe the large-scale variable load operation of the boiler-turbine coordinated system under wet conditions.

[0084] Simulations of this dynamic model show that as the boiler's pulverized coal load increases, the boiler furnace heat load rises. The working fluid in the economizer and water walls absorbs more heat, generating more saturated steam. Consequently, the main steam pressure and unit power gradually increase. Since the feedwater pump and boiler water circulation pump flows remain constant, the working fluid flow at the economizer inlet remains unchanged. However, due to the increased boiler heat load, the working fluid dryness at the water wall outlet increases, reducing the amount of working fluid entering the water storage tank. Consequently, the water level in the water storage tank gradually drops to zero meters.

[0085] As the feedwater pump flow rate increases stepwise, the flow rate of the working medium entering the economizer increases immediately. This squeezes the working medium in the economizer and water-walls. While the coal feed rate remains constant, the total mass of the working medium in the economizer and water-walls increases, causing fluctuations in the working medium flow rate at the water-wall outlet and, consequently, slight fluctuations in the main steam pressure and unit power. Furthermore, the increased feedwater pump flow rate increases the working medium storage mass in the economizer and water-walls. Consequently, the steam dryness at the water-wall outlet decreases, increasing the flow rate of the working medium entering the water storage tank. However, the boiler water circulating pump flow rate remains constant, causing the water level in the water storage tank to gradually rise to its maximum level.

[0086] As the boiler water circulating pump flow rate increases stepwise, the flow rate of the working medium at the economizer inlet increases immediately. Consequently, the working medium in the economizer and water-cooled wall is squeezed, and while the coal feed rate remains constant, the total mass of the working medium in the economizer and water-cooled wall increases, causing fluctuations in the working medium flow rate at the water-cooled wall outlet, resulting in slight fluctuations in the main steam pressure and unit power. Regarding the water level in the water storage tank, the water level in the water storage tank gradually decreases as the boiler water circulating pump flow rate increases stepwise. However, as the feed water flow rate entering the economizer inlet increases, the steam dryness at the water-cooled wall outlet decreases, resulting in an increase in the working medium flow rate entering the water storage tank. Consequently, the water level in the water storage tank gradually rises to its maximum value.

[0087] As the turbine throttle opening decreases, the main steam flow area decreases, causing the main steam pressure to gradually increase. Since the feedwater pump and boiler water circulation pump flows remain unchanged, the working fluid flow at the economizer inlet remains constant. A sudden increase in the main steam flow increases the mass accumulation on the boiler tube walls, immediately reducing the superheated steam flow and causing an immediate drop in unit power. However, with the coal feed remaining constant, as the main steam pressure gradually stabilizes, the superheated steam flow gradually increases and remains constant, allowing the unit power to gradually return to a stable value. Regarding the water storage tank level, the sudden decrease in the throttle opening reduces the working fluid flow. Consequently, the working fluid flow at the water wall outlet decreases, and the working fluid flow entering the water storage tank decreases, causing the water storage tank level to gradually drop. As the boiler steam pressure increases, the steam quality gradually decreases, causing the saturated water entering the water storage tank to gradually increase, causing the water storage tank level to gradually increase to its maximum value.

[0088] Based on the laws of conservation of mass and energy, this paper analyzes the operation of a DC coal-fired unit under wet conditions. Using a lumped parameter approach, a dynamic model of the coordinated system of a DC coal-fired unit under wet conditions is established. A parameter identification method that incorporates system characteristics is proposed to determine model parameters and functions. Verification of the model's dynamic accuracy and open-loop simulation tests demonstrate that the model can describe the variable load operation of a DC coal-fired unit in the wet range of 50MW to 350MW, with an average relative error of less than 7.8%.

[0089] By adopting the above method, the operating mechanism characteristics of the unit are effectively described by constructing dynamic models of multiple operating systems of the coal-fired unit respectively, and on this basis, the mapping relationship between input parameters and output parameters is constructed, and the advantages of the composite modeling method and the data-driven modeling method are organically combined, which not only reduces the dependence on the stable operating data of the unit during variable load operation, but also ensures the reliability of the model. Finally, according to the operating mechanism characteristics of the unit and the data group of variable load operation, the unknown parameters in the dynamic model are calculated. In this way, the model constructed by this method not only has a reliable physical model structure, can describe the dynamic characteristics of the system, but also has high dynamic accuracy.

[0090] Secondly, the present invention also provides a model building device for a coal-fired unit, such as Figure 4 Shown, including: A construction module 401 is used to construct dynamic models of multiple operating systems of the coal-fired unit under preset simplified conditions based on input parameters and output parameters of the coal-fired unit under wet operating conditions; Determination module 402 is used to 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; the state variable is used to represent the state change of the coal-fired unit under wet conditions; The construction module 401 is further configured to construct a data set of input parameters, output parameters, and state variables under the condition of uniform load changes based on the variable load operation data of the coal-fired unit; The determination module 402 is further configured to determine the constraints of the unknown parameters in the state variable expression according to the operating mechanism characteristics of the coal-fired unit; determine the unknown parameters according to the data set and the constraints, and thereby obtain a dynamic model of the coal-fired unit under wet operating conditions.

[0091] By adopting the above-mentioned device, the operating mechanism characteristics of the unit are effectively described by constructing dynamic models of multiple operating systems of the coal-fired unit respectively, and on this basis, the mapping relationship between input parameters and output parameters is constructed, and the advantages of the composite modeling method and the data-driven modeling method are organically combined, which 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, according to the operating mechanism characteristics of the unit and the data group of variable load operation, the unknown parameters in the dynamic model are calculated. In this way, the model constructed by this method not only has a reliable physical model structure, can describe the dynamic characteristics of the system, but also has high dynamic accuracy.

[0092] The present invention also provides a computer-readable storage medium, which stores a computer program, which can be used to execute the above Figure 3 The steps of the model building method of the coal-fired unit are provided.

[0093] The present invention also provides a computer device. At the hardware level, the computer device includes a processor, an internal bus, a network interface, a memory, and a non-volatile memory. Of course, it may also include hardware required for other services. The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it to achieve the above Figure 3 The steps of the model building method of the coal-fired unit are provided.

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

[0095] The present invention is described with reference to flowcharts and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts 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, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0096] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0097] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0098] It should be noted that the above specific embodiments can 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 this specification has described the present invention in detail, those skilled in the art should understand that the present invention can still be modified or replaced with equivalents; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention are included in the scope of protection of the patent for the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A method for constructing a model of a coal-fired unit, characterized in that: The method comprises: According to the input parameters and output parameters of the coal-fired unit under wet operating conditions, dynamic models of multiple operating systems of the coal-fired unit under preset simplified conditions are constructed respectively; Determining a mapping relationship between input parameters and output parameters based on multiple dynamic models, and obtaining a 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 working conditions; According to 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 changes; Determining the constraints of unknown parameters in the state variable expression according to the operating mechanism characteristics of the coal-fired unit; The unknown parameters are determined according to the data group and the constraint conditions, thereby obtaining a dynamic model of the coal-fired unit under wet working conditions.

2. The method for constructing a model of a coal-fired 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; and the dynamic models of the multiple operating systems include: The dynamic model of the milling system is: ； in, c 0 is the inertia time of the milling system; r B is the amount of coal fed into the furnace; u B is the fuel quantity command; τ Indicates the time delay in the milling system; t is a time variable; The dynamic model of the economizer and water wall system is: ； in, ρ lb is the working fluid density at the water wall outlet; V lb is the volume of economizer and water wall; D lb is the water wall outlet flow rate; D sm is the economizer inlet flow rate; h lb is the enthalpy of the working medium at the water wall outlet; c j is the specific heat capacity of the boiler metal tube wall; m j is the metal quality of the boiler tube wall; T j is the metal temperature of the boiler tube wall; h sm is the enthalpy of the working fluid at the economizer inlet; Q 1 is the amount of heat absorbed by the working medium in the economizer and water-cooled wall; k 1 is the heat absorbed by the working medium 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: ； in, V H is the water tank capacity, ρ H is the density of the working fluid in the water storage tank, x lb is the steam quality at the water wall outlet, D xh is the circulating water flow rate; The dynamic model of the superheater system includes a dynamic model of superheated steam enthalpy of the superheater system and a dynamic model of superheated steam pressure of the superheater system; The dynamic model of superheated steam enthalpy in the superheater system is: ； The dynamic model of superheated steam pressure in the superheater system is: ； in, ρ st is the working fluid density at the superheater outlet; V st is the superheater volume; D lb is the water wall outlet flow rate; h vbh is the enthalpy of saturated steam at the superheater inlet; h st is the steam enthalpy at the superheater outlet; Q 2 is the amount of heat absorbed by the working medium in the superheater; k 2 is the heat absorbed by the superheater working medium when 1 kg of pulverized coal is burned; p st is the working medium pressure at the superheater outlet; k 3 is the turbine fitting coefficient; u t Adjust the valve opening for the steam turbine; The dynamic model of the steam turbine system is: ； in, N e is the unit power; c 5 is the inertia time of the steam turbine; k 4 is the turbine efficiency coefficient.

3. A method for constructing a model of a coal-fired unit according to claim 2, characterized in that: Determining the mapping relationship between input parameters and output parameters according to multiple dynamic models includes: The state space form of the input parameters, output parameters and state variables of the dynamic model of the coal-fired unit under wet conditions is determined as follows: ； U 、 Y and X are the input parameter matrix, output matrix and state variable matrix of the model respectively, A (•), B (•), C (•) is a matrix function, specifically: ， in, D fw is the outlet water flow of the high pressure heater; u t Adjust the valve opening for the steam turbine; H is the water level in the water storage tank; p m is the steam pressure of the steam-water separator.

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

5. A method for constructing a model of a coal-fired unit according to claim 4, characterized in that: According to the operating mechanism characteristics of the coal-fired unit, the constraints for determining 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 Q i = k i x 1. Take the time derivative so that the derivative of the heat absorbed by the working medium is continuously greater than zero within the load variation range, and then determine the unknown parameters. k 1 and k 2 constraints; Based on the fact that the working fluid flow rate at the economizer inlet is the same as the working fluid flow rate at the water wall outlet, the constraint conditions are determined. D sm = D lb ; Based on the operating mechanism characteristics of coal-fired units, determine D lb = u t ( a 1 p m + b 1) / ( a 2 h lb + b 2), where a 1, a 2, b 1, b 2 is an unknown parameter; Combining the wet steam mechanism characteristics and water vapor thermodynamic properties, determine the wet steam dryness model x lb =( a 11 h lb + b 11 ) / ( a 22 p m + b 22 ),in a 11 , a 22 , b 11 , b 22 is an unknown parameter.

6. The method for constructing a model of a coal-fired unit according to claim 1, characterized in that: Determine the unknown parameters according to the data set and the constraints: Determine static parameters among the unknown parameters using a regression analysis method based on the data set; According to the constraints, the data set is combined with the immune genetic optimization algorithm to gradually identify the dynamic parameters of the unknown parameters of each system model.

7. The method for constructing a model of a coal-fired unit according to claim 1, characterized in that: The preset simplified conditions include: Treat the economizer and water wall as a single heated tube system; The superheated steam temperature can be stably controlled, and the desuperheating water flow is integrated into the superheater inlet flow, and the superheater is regarded as a single-tube heating system; Ignore the axial heat transfer between the flue gas, boiler tube wall and working medium; The amount of heat released by flue gas to the boiler tube wall is proportional to the heat released by coal combustion; The fluid characteristics are uniform over any cross-sectional area of ​​the heated tube; The high, medium and low pressure cylinders of the steam turbine are regarded as a steam turbine system; The heat absorbed by the reheater is converted into the turbine coefficient.

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

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

10. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 7 when executing the program.

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