Direct current furnace turbine-furnace coordination system dynamic modeling method suitable for wet condition

Abstract

The invention relates to a direct current furnace machine-furnace coordination system dynamic modeling method suitable for a wet condition. Based on the law of mass conservation and energy conservation, a lumped parameter method is adopted to construct a dynamic model comprising a coal pulverizing system, a coal economizer-water wall system, a water storage tank system, a superheater system and a steam turbine system; identifying parameters are optimized step by step by only utilizing unit variable load dynamic operation data and combining with the mechanism constraint that the heat absorption capacity of a working medium is monotonically increased along with the coal quantity as fired: static parameters are determined through dynamic data regression, nonlinear parameters are optimized based on a preset water-cooled wall outlet flow and dryness function structure, and the heat absorption capacity of the working medium is calculated. And finally, identifying dynamic parameters step by step by adopting an immune genetic algorithm. The dynamic characteristics and the physical consistency of the established model are verified through open-loop simulation, and the technical problems that dynamic description of the water level of the water storage tank is missing and the modeling precision is low under the wet working condition are solved.

Description

Technical Field

[0001] This invention relates to a dynamic modeling method for a DC furnace-machine coordination system applicable to wet operating conditions, belonging to the field of energy and power system process control technology. Background Technology

[0002] To help the power grid absorb the random and intermittent power generation from renewable energy sources, once-through (DC) boiler coal-fired units need to improve their deep peak-shaving capabilities and operational safety, constructing a new power system primarily based on renewable energy. However, DC boiler coal-fired units operating under wet conditions and varying loads experience reduced boiler water circulation safety characteristics and water-cooled wall operational stability. Furthermore, due to the small capacity of the unit's water tank, varying loads can cause significant fluctuations in the water level, easily leading to water carryover in the superheater inlet steam and reducing superheater operational safety. Therefore, it is necessary to establish a dynamic model of the boiler-machine coordination system of DC boiler coal-fired units under wet conditions to reflect the dynamic characteristics of the system operation under wet conditions and to use this model in control system design, thereby improving the operational flexibility and safety of DC boiler coal-fired units under wet conditions.

[0003] Currently, there is considerable research on dynamic modeling of the boiler-turbine coordination system of once-through coal-fired power units under dry conditions, but less research on dynamic modeling of the boiler-turbine coordination system under wet conditions. Gao Zheng et al. established a dynamic model of the boiler-turbine coordination system of ultra-supercritical coal-fired power units suitable for dry-wet transitions; however, this study did not provide the dynamic characteristics of the system model to prove the correctness of the system model structure. Wang Guotao et al. used a composite modeling method to establish a simplified control model of the boiler-turbine coordination system of supercritical coal-fired power units under wet conditions; however, this model lacks a physical description of the water level in the storage tank, increasing the difficulty of control system design. Deng Tuoyu et al. combined the core model of the once-through boiler steam-water system with the traditional drum boiler load system model to obtain a nonlinear dynamic model of once-through boiler units suitable for both dry and wet conditions; however, due to the lack of a system mechanism modeling process, the dynamic accuracy and structural correctness of the model need to be verified. Therefore, further research is needed on dynamic modeling of the boiler-turbine coordination system of once-through coal-fired power units under wet conditions to improve the operational flexibility and safety of the units.

[0004] Drawing on research into dynamic modeling of the boiler-turbine coordination system of once-through coal-fired power units under dry-state conditions is beneficial for conducting research on dynamic modeling of the system under wet-state conditions. Currently, the main methods for dynamic modeling of the boiler-turbine coordination system of once-through boiler units include composite modeling and data-driven modeling. Composite modeling uses physical conservation laws and mechanistic analysis of the system's operation process to establish the physical structure of the system model, and identifies the system model functions and parameters through operational data. The advantages of this method are a reliable physical model structure, the ability to describe the system's dynamic characteristics, and appropriate model accuracy. Liu Jizhen et al. used the lumped parameter method to mechanistically analyze the variable load operation process of the boiler-turbine coordination system and established a nonlinear dynamic model for ultra-supercritical units. This model can describe the variable load operation process of the unit under dry-state conditions and reflect the system's dynamic characteristics. To describe the system's low-load operation process, Niu Yuguang et al. used the lumped parameter method to establish a dynamic model of the boiler-turbine coordination system of a 600MW supercritical unit. This model can describe the variable load operation process of the unit under dry-state conditions at 30%-50% of rated load and reflects the system's dynamic characteristics. Tian Liang et al. established energy balance processes for the metal in the heat transfer zone and the steam-water heat storage process in the volumetric zone, respectively, and built a core model of the once-through boiler steam-water system, quantitatively analyzing the coupling characteristics of steam pressure and intermediate point temperature. Tian Zhen et al. used a composite modeling method and model reduction technique to establish a dynamic model of the boiler-turbine coordination system for a 1000MW ultra-supercritical coal-fired unit. In addition, Fan He et al. established a dynamic model of the boiler-turbine coordination system for an ultra-supercritical coal-fired unit within the 50%-100% rated load range, and based on this, established a dynamic model of the boiler-turbine coordination system within the 35%-100% rated load range and a dynamic model of the boiler-turbine coordination system including superheated steam temperature.

[0005] Liu Xiangjie et al. used fuzzy neural networks, combined with dynamic operating data of the unit, to establish a data-driven model of the 1000MW ultra-supercritical boiler-turbine coordination system, achieving modeling accuracy superior to the recursive least squares algorithm. In addition, long short-term memory neural networks, deformable neural networks, and input convex neural networks were also used to establish neural network models of boiler-turbine coordination systems. Hou Guolian et al. used fuzzy models to establish a boiler-turbine coordination system model for a once-through coal-fired unit.

[0006] In the aforementioned composite modeling method, the model parameters and functions need to be identified 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, which limits the use of this method.

[0007] Unlike composite modeling methods, data-driven modeling combines dynamic operating data of the unit with intelligent modeling methods, such as neural networks and fuzzy systems, to establish a system model. This model has high dynamic accuracy, but due to the lack of mechanistic analysis, its structural reliability is relatively low.

[0008] To describe the dynamic characteristics of the boiler-generator coordination system of a once-through coal-fired power unit under wet operating conditions, this invention employs a composite modeling method to establish a dynamic model of the system. It also proposes a parameter identification method that utilizes only dynamic operating data and integrates mechanistic characteristics to determine the system model parameters and establish the dynamic model. Furthermore, open-loop simulation analysis and dynamic accuracy data verification of the model are conducted, demonstrating the effectiveness of the established model. Summary of the Invention

[0009] To achieve the goal of obtaining a dynamic model of the boiler-generator coordination system of a DC-fired power plant under wet operating conditions, it is necessary to establish a dynamic model of the boiler-generator coordination system through a composite modeling method. This invention proposes a parameter identification method that uses only dynamic operating data and integrates mechanistic characteristics to determine the system model parameters and establish a dynamic model of the system. Through open-loop simulation analysis and verification of the model's dynamic accuracy data, the effectiveness of the modeling method and the established model is demonstrated, thereby overcoming the shortcomings of existing technologies.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A dynamic modeling method for a DC furnace-furnace coordination system suitable for wet operating conditions includes the following steps:

[0012] Step 1: Based on the laws of conservation of mass and energy, a dynamic model including the pulverizing system, economizer-water-cooled wall system, water tank system, superheater system and turbine system is constructed using the lumped parameter method.

[0013] Step 2: Using only the unit's dynamic operating data under varying loads, execute the following sub-steps in the order of dependency:

[0014] (a) Static parameters k1 and k2 are determined by fitting a quadratic function, where k1 is the heat absorption coefficient of the working fluid in the economizer and water-cooled wall, and k2 is the heat absorption coefficient of the working fluid in the superheater, and Q1 = k1·r is ensured. B and Q2=k2·r B Satisfying the monotonically increasing constraint, r B This refers to the amount of coal fed into the furnace.

[0015] (b) Defining the working fluid flow rate D at the water-cooled wall outlet based on physical mechanisms lb and dryness x lb The function structure;

[0016] (c) Based on k1, k2 and the function structure, identify dynamic parameters in the order of system flow: boiler water circulation pump inertia time, pulverizing system parameters and economizer-water-cooled wall parameters, superheater parameters, and steam turbine parameters;

[0017] Step 3: Based on the parameterized dynamic model from Step 2, verify the output variable, main steam pressure p. st Economizer inlet flow rate Dsm Water level in storage tank (l), unit power (N) e Its dynamic accuracy and open-loop response characteristics.

[0018] Preferably, in step 1:

[0019] The dynamic model of the powder-making system is as follows:

[0020]

[0021] In the formula, c0 is the inertial time of the pulverizing system; u B It is a fuel quantity command; τ represents the time delay in the pulverizing system;

[0022] Economizer and water-cooled wall system model:

[0023]

[0024] in,

[0025]

[0026] c2=ρ lb V lb ,

[0027]

[0028] In the formula, h sm D represents the enthalpy of the working fluid at the economizer inlet. lb h is the outlet flow rate of the water-cooled wall. lb m is the enthalpy of the working fluid at the outlet of the water-cooled wall. j For the metal mass of the boiler tube wall, c j p is the specific heat capacity of the boiler tube wall. m The working fluid pressure of the steam-water separator, ρ lb V is the density of the working fluid at the outlet of the water-cooled wall. lb For the volume of the economizer and water-cooled wall; T j C1, C2, D1, and D2 are the boiler tube wall metal temperatures, and C1, C2, D1, and D2 are the economizer-water-cooled wall parameters.

[0029] Water storage tank system model:

[0030]

[0031] In the formula, ρ w Where is the density of saturated water; F is the bottom area of ​​the water storage tank;

[0032] Dynamic model of superheated steam pressure in superheater system:

[0033]

[0034] in,

[0035] In the formula, p st k is the working fluid pressure at the superheater outlet; k3 is the turbine fitting coefficient; u t For the turbine control valve opening; h st ρ is the enthalpy at the superheater outlet. st c is the density of the working fluid at the superheater outlet; c4 is the rate of change of the total energy of the working fluid in the system caused by the pressure change; h vbh This is the enthalpy of saturated steam at the superheater inlet.

[0036] Dynamic model of steam turbine system:

[0037]

[0038] In the formula, N e c5 is the unit power; c5 is the turbine inertia time; k4 is the turbine efficiency coefficient.

[0039] The state-space form of the dynamic model of the boiler-generator coordination system of a once-through coal-fired unit under wet conditions is as follows:

[0040]

[0041] In the formula, U, Y, and X are the model input, output, and state variables, respectively, as follows:

[0042] U = [u1, u2, u3, u4] T =[u B D fw D xh ,u t ] T Y = [y1, y2, y3, y4] T =[p st D sm ,H,N e ] T ,

[0043] X = [x1, x2, x3, x4, x5, x6, x7, x8] T =[r B D sm ,p m ,h lb ,h st ,p st N e [H] T ,

[0044] The specific form of this state-space model is as follows:

[0045]

[0046] In the formula,

[0047] x lb =x(p m ,h lb ),D lb =f(p m ,h lb ), Q1=k1x1, Q2=k2x1, h vbh =h(x3),ρ w =ρ(x3),

[0048] c 31 c 32 The heat storage coefficient of the working fluid.

[0049] Preferably, the function structure in step (b) is constructed based on the following physical mechanism:

[0050] D lb The function structure is based on the turbine control valve opening u. t Water-cooled wall outlet pressure p m and enthalpy h lb The coupling relationship is determined;

[0051] x lb The function structure is determined based on the thermodynamic properties of wet steam and the data correlation of the steam properties software;

[0052] The function structure is implemented in the following form:

[0053] D lb =u t (a1p m +b1) / (a2h lb +b2), x lb =(a 11 h lb +b 11 ) / (a 22 p m +b 22 );

[0054] Nonlinear function parameters a1, b1, a2, b2, a 11 b 11 a 22 b 22 The saturation line data generated by the water vapor thermodynamic property software is used as a boundary constraint for optimization.

[0055] Preferably, the dynamic parameters in step (c) are optimized using an immune genetic algorithm, and the specific steps include:

[0056] (i) The dynamic parameters are divided into four groups according to the pulverizing system, economizer-water-cooled wall system, superheater system, and steam turbine system;

[0057] (ii) Optimize the parameters of each group in sequence, and fix the parameters of the previous group as the identified optimal values ​​when optimizing the current group;

[0058] (iii) Perform immune genetic optimization independently for each set of parameters, including antibody initialization, affinity calculation based on weighted error of output variables, immune selection and cloning, mutation recombination and antibody inhibition;

[0059] (iv) The optimization results of the subsequent group are fed back to the preceding group for error verification and re-optimization.

[0060] Preferably, the model validation metrics satisfy:

[0061] Within the load range of 50MW-350MW, the output variable main steam pressure p st Economizer inlet flow rate D sm Water level in storage tank (l), unit power (N) e The average relative error is less than 7.8%;

[0062] The open-loop simulation response curves conform to the physical characteristics of the unit operation, including: when the fuel quantity command increases stepwise, the water level in the storage tank decreases; when the feedwater pump flow rate increases stepwise, the water level in the storage tank rises; when the turbine control valve opening decreases stepwise, the main steam pressure rises and the water level in the storage tank first decreases and then rises.

[0063] Preferably, the model construction in step 1 needs to meet the following simplification conditions:

[0064] (A1) The economizer and water-cooled wall are considered as a single heat-receiving tube system;

[0065] (A2) Superheated steam temperature is stably controlled, and the superheater is regarded as a single-tube system;

[0066] (A3) Ignore axial heat transfer between flue gas, pipe wall and working fluid;

[0067] (A4) The heat release of flue gas is directly proportional to the heat of coal combustion;

[0068] (A5) The fluid characteristics are uniform across any cross-sectional area of ​​the heated tube;

[0069] (A6) The high-pressure, intermediate-pressure, and low-pressure cylinders of a steam turbine are considered as a single system;

[0070] (A7) The heat absorbed by the reheater is converted into the turbine coefficient.

[0071] This invention also provides a dynamic modeling system for a DC furnace-machine coordination system suitable for wet operating conditions, comprising:

[0072] Data acquisition module: used to acquire dynamic operating data of the unit under varying loads;

[0073] Model building module: configured to perform the method described in any one of claims 1-6 to build a dynamic model;

[0074] Parameter identification module: It is configured to use only dynamic operating data of variable load, and complete parameter optimization by integrating mechanistic constraints in the order of static parameters, nonlinear function parameters, and dynamic parameters. The dynamic parameters are identified by an immune genetic algorithm.

[0075] Simulation verification module: Outputs the open-loop response curve of the model and the dynamic accuracy verification results.

[0076] The present invention also provides a non-transitory readable storage medium for storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the above method.

[0077] The present invention also provides an electronic device, including a processor and a memory, wherein the memory stores a computer program, and the processor executes the program to implement the steps of the above method.

[0078] The beneficial effects of the above technical solution adopted in this invention are as follows:

[0079] The above-mentioned scheme proposes a dynamic modeling method for the boiler-machine coordination system of a DC boiler under wet operating conditions, aiming to solve the problem of difficult modeling of the coordinated control system of ultra-supercritical coal-fired power generating units under wet operating conditions. Based on the laws of conservation of mass and energy, the operating process of a DC boiler coal-fired unit under wet operating conditions is analyzed mechanistically. A lumped parameter method is used to establish a dynamic model of the boiler-machine coordination system of a DC boiler coal-fired unit under wet operating conditions, and a parameter identification method integrating system characteristics is proposed to determine the model parameters and functions. Dynamic accuracy verification and open-loop simulation tests show that the model can describe the variable load operation process of a DC boiler coal-fired unit in the range of 50MW-350MW under wet operating conditions, with an average relative error of less than 7.8%. Furthermore, the model can accurately reflect the dynamic characteristics of the system, indicating the correctness of the established model structure. The embodiments of this invention can be used for simulation analysis and control system design of the boiler-machine coordination system of a DC boiler coal-fired unit under wet operating conditions, providing effective support for the optimization of coordinated control of ultra-supercritical coal-fired power generating units and improving the operational flexibility and safety of the unit. Attached Figure Description

[0080] Figure 1 This is a schematic diagram of the operation process of an ultra-supercritical coal-fired power unit under wet conditions (red line: steam; blue line: liquid water; black line: coal).

[0081] Figure 2 This is a schematic diagram of the boiler-generator coordination system model for a once-through coal-fired power unit under wet operating conditions (solid line: strong correlation; dashed line: weak correlation).

[0082] Figure 3 A flowchart for parameter identification based on fusion mechanism characteristics.

[0083] Figure 4 This is the main steam pressure response curve under wet-state variable load conditions of the unit.

[0084] Figure 5 The economizer inlet working fluid response curve is shown under wet variable load conditions of the unit.

[0085] Figure 6 This is the water level response curve of the water storage tank under wet variable load conditions of the unit.

[0086] Figure 7 This is the power response curve of the unit under wet-state variable load conditions.

[0087] Figure 8 The system output variable response curve after a step increase in the fuel quantity command.

[0088] Figure 9 The system output variable response curve after a step increase in the flow rate of the water pump.

[0089] Figure 10 The system output variable response curve after a step increase in the flow rate of the boiler water circulation pump.

[0090] Figure 11 The system output variable response curve after a step reduction in the turbine control valve opening. Detailed Implementation

[0091] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0092] 1.1 Operation process of the boiler-generator coordination system of ultra-supercritical coal-fired power units under wet conditions

[0093] This invention focuses on a 1000MW ultra-supercritical coal-fired power unit. The unit operates under wet conditions as follows: Figure 1 As the unit load 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, generally 30% of the boiler's maximum continuous evaporation rate, 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 avoid water 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 storage 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. Table 1 shows the key operating parameters of the unit.

[0094] Table 1. Main operating parameters of the unit under the condition of maximum continuous evaporation rate of the boiler.

[0095]

[0096] 1.2 Model of Coordination System of Ultra-Supercritical Coal-fired Unit under Wet Conditions

[0097] To improve the safety and economy of unit operation, the boiler-turbine coordination system model of a once-through coal-fired unit under wet conditions has four inputs, namely the 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 rate D xh (kg / s), four output quantities, namely the economizer inlet flow rate D sm (kg / s), Unit load N e (MW), main steam pressure Pst (MPa) and water level l (m) in the storage tank. Figure 2 Provide the correspondence between the model input and output.

[0098] 2 Dynamic Modeling of the Coordination System of Ultra-Supercritical Coal-fired Units under Wet Conditions

[0099] Before modeling the system, simplifying assumptions need to be made about the model, including:

[0100] (A1) The economizer and water-cooled wall are considered as a single heat-receiving tube system;

[0101] (A2) The temperature of the superheated steam can be stably controlled, and the flow rate of the desuperheating water is integrated into the flow rate of the superheater inlet, so the superheater is regarded as a single-tube heating system.

[0102] (A3) Ignore axial heat transfer between flue gas, boiler tube wall and working fluid;

[0103] (A4) The heat released by flue gas on the boiler tube wall is approximately proportional to the heat released by coal combustion.

[0104] (A5) The fluid characteristics are uniform across any cross-sectional area of ​​the heated tube;

[0105] (A6) The high-pressure, intermediate-pressure, and low-pressure cylinders of a steam turbine are considered as a single steam turbine system;

[0106] (A7) The heat absorbed by the reheater is converted into the turbine coefficient.

[0107] 2.1 Dynamic Modeling of the Powder Making System

[0108] The dynamic operation of the pulverizing system can be considered as a first-order inertial plus time-delay process; therefore, the dynamic model of the pulverizing system is:

[0109]

[0110] In the formula, c0 is the inertial time of the pulverizing system, in seconds; r B This refers to the amount of coal fed into the furnace, in kg / s; u B τ represents the fuel quantity instruction, in kg / s; τ represents the time delay in the pulverizing system, in seconds.

[0111] 2.2 Dynamic Modeling of Economizer and Water-Cooled Wall System

[0112] 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 ) can be represented as

[0113]

[0114] In the formula, T xh It is inertial time, s; D sm The economizer inlet flow rate is kg / s; D fw D is the flow rate of the water pump, kg / s; xh The flow rate of the boiler water circulation pump is kg / s.

[0115] This paper analyzes the operation of the economizer and water-cooled wall system from a mechanistic perspective. Based on the laws of conservation of mass and energy, a lumped parameter modeling method is adopted, using the system outlet as the lumped parameter point to establish a dynamic model of the economizer and water-cooled wall system.

[0116]

[0117] 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 c is the enthalpy of the working fluid at the water-cooled wall outlet, in kJ / kg; j Specific heat capacity of boiler metal tube wall, kJ / (kg·℃); m j The mass of the boiler tube wall metal is expressed in kg and 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 expressed in kJ / kg; h. lb Q1 is the enthalpy of the working fluid at the outlet of the water-cooled wall, kJ / kg; Q1 is the heat absorbed by the working fluid in the economizer and water-cooled wall, kJ / s; k1 is the heat absorbed by the working fluid in the economizer and water-cooled wall when 1 kg of pulverized coal is burned, kJ / (kg·s).

[0118] Based on assumptions (A1), (A3)-(A5), and differentiating equation (2.3) with respect to the steam pressure and enthalpy at the water-cooled wall outlet, we can obtain...

[0119]

[0120] In the formula, p lb and h lb Let p be the working fluid pressure at the water-cooled wall outlet (MPa) and p be the enthalpy (kJ / kg). Since the working fluid at the steam-water separator outlet is subjected to uniform force, the working fluid pressure at the water-cooled wall outlet can be considered equal to the working fluid pressure at the steam-water separator, i.e., p. lb =p m .

[0121] Equation (2.4) can be further written as

[0122]

[0123] In the formula,

[0124] Equation (2.5) can be further written as

[0125]

[0126] In the formula, c1 = b 21 -b 11 b 22 / b 12 d1 = b 22 / b 12 c2 = b 22 -b 12 b 21 / b 11 d1 = b 21 / b 11 .

[0127] 2.3 Dynamic Modeling of Water Storage Tank System

[0128] According to equation (2.6), the dryness model of the working fluid at the water-cooled wall outlet can be obtained, 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:

[0129]

[0130] Since the water tank is saturated, the mass of the working fluid in the water tank, V H ρ H =V s ρ s +V wρ 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. H ρ H ≈V w ρ w V w =FH, where F is the bottom area of ​​the water storage tank, in meters. 2 H represents the height of the water 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:

[0131]

[0132] 2.4 Dynamic Modeling of Superheater System

[0133] Based on hypothesis (A2), the operation of the superheater system is analyzed mechanistically. A lumped parameter modeling method is used, with the system outlet as the lumped parameter point, to establish a dynamic model of the superheated steam enthalpy of the superheater system.

[0134]

[0135] 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 expressed in kJ / kg; h. st Q1 is the enthalpy of the superheater outlet steam, kJ / kg; Q2 is the heat absorbed by the working fluid in the superheater, kJ / s; k2 is the heat absorbed by the superheater working fluid when 1 kg of pulverized coal is burned, kJ / (kg·s). Let c 32 =ρ st V st .

[0136] Energy balance of steam-water thermal storage process in reference volume region

[11] Based on the equations and equation (2.9), a dynamic model of the superheated steam pressure in the superheater system is established, namely...

[0137]

[0138] In the formula, p st k is the working fluid pressure at the superheater outlet, MPa; k3 is the turbine fitting coefficient, kJ / (MPa·s); u t To set the turbine control valve opening, and let

[0139] 2.5 Dynamic Modeling of Steam Turbine System

[0140] Based on assumptions (A6) and (A7), the steam turbine system can be described by a first-order inertial element.

[14] ,Right now

[0141]

[0142] In the formula, N e c5 is the unit power, in MW; c5 is the turbine inertial time, in s; k4 is the turbine efficiency coefficient.

[0143] 2.6 Dynamic Model Structure of the Coordination System of a DC-fired Coal-fired Unit under Wet Conditions

[0144] In summary, the state-space form of the dynamic model of the boiler-generator coordination system of a once-through coal-fired unit under wet conditions is as follows:

[0145]

[0146] In the formula, U, Y, and X are the model input, output, and state variables, respectively, as follows:

[0147]

[0148] The specific form of this state-space model is as follows:

[0149]

[0150] In the formula,

[0151] x lb =x(p m ,h lb ),D lb =f(p m ,h lb ), Q1=k1x1, Q2=k2x1, h vbh =h(x3),ρ w =ρ(x3),(2.15)3 Parameter Identification

[0152] The dynamic model of the boiler-turbine coordination system, equations (2.14) and (2.15), requires identification of seven static parameters: k1, k2, k3, k4, and h. vbh , ρ w hsm Two nonlinear functions, x lb and D lb and 11 dynamic parameters, τ, c0, T x c1, d1, c2, d2, c 31 c 32 C4, C5. Under wet-state variable load operation, the unit experiences a limited steady-state load range. Therefore, this study proposes a parameter identification method that integrates mechanistic characteristics. This method utilizes only variable load dynamic data to identify the system's static and dynamic parameters and nonlinear functions. The flowchart of this parameter identification method is as follows:

[0153] Step 1: Select a set of variable load operation data, and uniformly select unit load interval points to roughly grasp the system parameter change pattern, determine the system variable values ​​corresponding to each unit load point, and construct a system variable data set with uniform unit load intervals.

[0154] Step 2: For the heat absorption of the working fluid, Q1 and Q2, the established functions need to ensure that the heat absorption of the working fluid increases proportionally with the coal feed rate. That is, the parameter structure is determined, k1 = k(x1) and k2 = g(x1), which are a system of quadratic functions in one variable. By differentiating the functions, Q... i =k i x1, i = 1, 2, ensure that the derivative of the heat absorbed by the working fluid is always greater than zero within the load variation range, satisfying the system operating mechanism characteristics; otherwise, reselect the data and identify parameters k1 and k2.

[0155] Step 3: Based on the system variable data set, use regression analysis to identify the static parameters k3, k4, and h. vbh and ρ w ;

[0156] Step 4: When the unit is operating under varying load, 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, i.e., D. sm ≈D lb Based on the analysis of mechanistic characteristics and literature, the function structure is determined to be D. lb =u t (a1p m +b1) / (a2h lb +b2); Since the working fluid at the water-cooled wall outlet is in a wet steam state, the wet steam dryness model x is determined by combining the wet steam mechanism characteristics and steam thermodynamic properties software. lb =(a 11 h lb +b 11 ) / (a 22 p m +b 22 );

[0157] Step 5: For dynamic parameters, combine runtime data and optimization algorithms to gradually identify the dynamic parameters of each system. First, identify the dynamic parameters, T... x Secondly, identify the dynamic parameters τ, c0, c1, d1, c2, d2; furthermore, identify the dynamic parameters c 31 c 32 Finally, the dynamic parameters c4 and c5 are identified sequentially.

[0158] Based on the parameter identification method of the fusion mechanism characteristics, a dynamic operating data set is selected, and Table 2 gives the system variable values ​​corresponding to the load points of each unit.

[0159] Table 2 System variable groups corresponding to the load points of each unit

[0160]

[0161] Based on equation (2.14), the static parametric equation is determined.

[0162]

[0163] Based on parameter identification methods, operational data, and the thermodynamic properties of water vapor, h is determined. vbh and ρ w h sm Take it as a constant, that is

[0164]

[0165]

[0166] ρ m =-16.695p m +855.44,(2.25)

[0167] By combining the operational data and taking the average, we can obtain h. sm =1118.2kJ / kg.

[0168] By combining operational data and the parameter identification methods described above, D can be identified. lb and x lb ,Right now

[0169]

[0170] 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:

[0171] 4. Model Validation

[0172] 4.1 Model Dynamic Accuracy Verification

[0173] Since this data set 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 of the boiler-generator coordination system of a once-through coal-fired unit under wet conditions, with a sampling time of 1 second. The system output variation curve is shown below. Figures 4 to 7 As shown in Table 3, the root mean square error (RMSE) and mean relative error (MRE) of the system output variables are given.

[0174] Table 3 shows the root mean square error and average relative error of the system output variables corresponding to the load points of each unit.

[0175]

[0176] Depend on Figures 4-7 As shown, under wet operating conditions, when the unit operates with varying loads between 50MW and 350MW, the model simulation values ​​can track the actual operating values ​​well and exhibit the same trend. In Table 3, 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.

[0177] 4.2 Dynamic Characteristics Analysis and Verification of the Model

[0178] This section conducts open-loop simulation experiments on the system model, analyzes the dynamic characteristics of the system model, and verifies the correctness of the model structure. Figures 8-11 The open-loop response curve of the system model.

[0179] like Figure 8 As shown, with the increase in pulverized coal quantity, the boiler furnace heat load increases, and the working fluid in the economizer and water-cooled walls absorbs more heat, producing more saturated steam. Therefore, the main steam pressure and unit power gradually increase. 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 constant. Due to the increase in 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. Therefore, the water level in the water storage tank gradually drops to zero meters.

[0180] like Figure 9As shown, with the step increase in the feedwater pump flow rate, the flow rate of the working fluid entering the economizer immediately increases. Therefore, the working fluid in the economizer and water-cooled wall is compressed. With the coal feed rate remaining unchanged, the total mass of the working fluid in the economizer and water-cooled wall 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.

[0181] Furthermore, the increased feedwater pump flow rate leads to a larger working fluid storage volume in the economizer and water-cooled walls. Consequently, the steam dryness at the water-cooled wall outlet decreases, increasing the working fluid flow rate into the 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.

[0182] like Figure 10 As shown, with a step increase in the flow rate of the boiler water circulation pump, the flow rate of the working fluid at the economizer inlet immediately increases. Therefore, the working fluid in the economizer and water-cooled walls is compressed, and 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, resulting in slight fluctuations in the main steam pressure and unit power. Regarding the water level in the storage tank, a step increase in the boiler water circulation pump flow rate causes the water level in the storage tank to gradually decrease. However, as the feedwater flow rate entering 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. Therefore, the water level in the storage tank gradually rises to its maximum value.

[0183] like Figure 11 As shown, with a step decrease in the turbine control valve opening, the main steam flow area decreases, thus the main steam pressure gradually increases. 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 constant. The step increase in main steam flow rate increases the mass stored in the boiler tubes, causing an immediate decrease in superheated steam flow rate, resulting in an immediate drop in unit load. However, with the coal feed rate remaining constant, as the main steam pressure gradually stabilizes, the superheated steam flow rate gradually increases and remains constant, and the unit power gradually recovers to a stable value. Regarding the water tank level, the sudden decrease in the control valve opening leads to a decrease in the working fluid flow rate. Therefore, 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 increase, thus the water tank level gradually increases to its maximum value.

[0184] In summary, based on the analysis of the system's dynamic characteristics, Figures 8-11 The system dynamic response curves in the model conform to the operating characteristics of the unit, verifying the correctness of the established model and parameter structure.

[0185] Based on the same technical solution, a computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform the data source importance determination method based on highway business and data networks as described above.

[0186] Based on the same technical solution, an electronic device includes one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing the data source importance determination method based on highway business and data networks as described above.

[0187] 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.

[0188] 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, and 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 illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0189] 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.

[0190] 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.

[0191] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A dynamic modeling method for a DC furnace-furnace coordination system suitable for wet operating conditions, characterized in that, Includes the following steps: Step 1: Based on the laws of conservation of mass and energy, a dynamic model including the pulverizing system, economizer-water-cooled wall system, water tank system, superheater system and turbine system is constructed using the lumped parameter method. Step 2: Using only the unit's dynamic operating data under varying loads, execute the following sub-steps in the order of dependency: (a) Static parameters k1 and k2 are determined by fitting a quadratic function, where k1 is the heat absorption coefficient of the working fluid in the economizer and water-cooled wall, and k2 is the heat absorption coefficient of the working fluid in the superheater, and Q1 = k1·r is ensured. B and Q2=k2·r B Satisfying the monotonically increasing constraint, r B This refers to the amount of coal fed into the furnace. (b) Defining the working fluid flow rate D at the water-cooled wall outlet based on physical mechanisms lb and dryness x lb The function structure; (c) Based on k1, k2 and the function structure, identify dynamic parameters in the order of system flow: boiler water circulation pump inertia time, pulverizing system parameters and economizer-water-cooled wall parameters, superheater parameters, and steam turbine parameters; Step 3: Based on the parameterized dynamic model from Step 2, verify the output variable, main steam pressure p. st Economizer inlet flow rate D sm Water level in storage tank (l), unit power (N) e Its dynamic accuracy and open-loop response characteristics.

2. The method according to claim 1, characterized in that, In step 1: The dynamic model of the powder-making system is as follows: In the formula, c0 is the inertial time of the pulverizing system; u B It is a fuel quantity command; τ represents the time delay in the pulverizing system; Economizer and water-cooled wall system model: in, c2=ρ lb V lb , In the formula, h sm D represents the enthalpy of the working fluid at the economizer inlet. lb h is the outlet flow rate of the water-cooled wall. lb m is the enthalpy of the working fluid at the outlet of the water-cooled wall. j For the metal mass of the boiler tube wall, c j p is the specific heat of the boiler tube wall. m The working fluid pressure of the steam-water separator, ρ lb V is the density of the working fluid at the outlet of the water-cooled wall. lb For the volume of the economizer and water-cooled wall; T j C1, C2, D1, and D2 are the boiler tube wall metal temperatures, and C1, C2, D1, and D2 are the economizer-water-cooled wall parameters. Water storage tank system model: In the formula, ρ w Where is the density of saturated water, and F is the bottom area of ​​the water storage tank; Dynamic model of superheated steam pressure in superheater system: in, In the formula, p st k is the working fluid pressure at the superheater outlet; k3 is the turbine fitting coefficient; u t For the turbine control valve opening; h st ρ is the enthalpy at the superheater outlet. st c is the density of the working fluid at the superheater outlet; c4 is the rate of change of the total energy of the working fluid in the system caused by the pressure change; h vbh The enthalpy of saturated steam at the superheater inlet; Dynamic model of steam turbine system: In the formula, N e c5 is the unit power; c5 is the turbine inertia time; k4 is the turbine efficiency coefficient. The state-space form of the dynamic model of the boiler-generator coordination system of a once-through coal-fired unit under wet conditions is as follows: In the formula, U, Y, and X are the model input, output, and state variables, respectively, as follows: U=[u1,u2,u3,u4] T =[u B ,D fw ,D xh ,u t ] T ,Y=[y1,y2,y3,y4] T =[p st ,D sm ,H,N e ] T , X=[x1,x2,x3,x4,x5,x6,x7,x8] T =[r B ,D sm ,p m ,h lb ,h st ,p st ,N e ,H] T . The specific form of the spatial model is as follows: In the formula, x lb =x(p m ,h lb ),D lb =f(p m ,h lb ),Q1=k1x1,Q2=k2x1,h vbh =h(x3),ρ w =ρ(x3), c 31 c 32 The heat storage coefficient of the working fluid.

3. The method according to claim 2, characterized in that, The function structure in step (b) is constructed based on the following physical mechanism: D lb The function structure is based on the turbine control valve opening u. t Water-cooled wall outlet pressure p m and enthalpy h lb The coupling relationship is determined; x lb The function structure is determined based on the thermodynamic properties of wet steam and the data correlation of the steam properties software; The function structure is implemented in the following form: D lb =u t (a1p m +b1) / (a2h lb +b2),x lb =(a 11 h lb +b 11 ) / (a 22 p m +b 22 ); Nonlinear function parameters a1, b1, a2, b2, a 11 b 11 a 22 b 22 The saturation line data generated by the water vapor thermodynamic property software is used as a boundary constraint for optimization.

4. The method according to claim 2, characterized in that, In step (c), the dynamic parameters are optimized using an immune genetic algorithm. The specific steps include: (i) The dynamic parameters are divided into four groups according to the pulverizing system, economizer-water-cooled wall system, superheater system, and steam turbine system; (ii) Optimize the parameters of each group in sequence, and fix the parameters of the previous group as the identified optimal values ​​when optimizing the current group; (iii) Perform immune genetic optimization independently for each set of parameters, including antibody initialization, affinity calculation based on weighted error of output variables, immune selection and cloning, mutation recombination and antibody inhibition; (iv) The optimization results of the subsequent group are fed back to the preceding group for error verification and re-optimization.

5. The method according to claim 1, characterized in that, The model validation metrics are satisfied: Within the load range of 50MW-350MW, the output variable main steam pressure p st Economizer inlet flow rate D sm Water level in storage tank (l), unit power (N) e The average relative error is less than 7.8%; The open-loop simulation response curves conform to the physical characteristics of the unit operation, including: when the fuel quantity command increases stepwise, the water level in the storage tank decreases; when the feedwater pump flow rate increases stepwise, the water level in the storage tank rises; when the turbine control valve opening decreases stepwise, the main steam pressure rises and the water level in the storage tank first decreases and then rises.

6. The method according to claim 1, characterized in that, The model construction in step 1 must meet the following simplification conditions: (A1) The economizer and water-cooled wall are considered as a single heat-receiving tube system; (A2) Superheated steam temperature is stably controlled, and the superheater is regarded as a single-tube system; (A3) Ignore axial heat transfer between flue gas, pipe wall and working fluid; (A4) The heat release of flue gas is directly proportional to the heat of coal combustion; (A5) The fluid characteristics are uniform across any cross-sectional area of ​​the heated tube; (A6) The high-pressure, intermediate-pressure, and low-pressure cylinders of a steam turbine are considered as a single system; (A7) The heat absorbed by the reheater is converted into the turbine coefficient.

7. A dynamic modeling system for a DC furnace-machine coordination system suitable for wet operating conditions, characterized in that, include: Data acquisition module: used to acquire dynamic operating data of the unit under varying loads; Model building module: configured to perform the method described in any one of claims 1-6 to build a dynamic model; Parameter identification module: It is configured to use only dynamic operating data of variable load, and complete parameter optimization by integrating mechanistic constraints in the order of static parameters, nonlinear function parameters, and dynamic parameters. The dynamic parameters are identified by an immune genetic algorithm. Simulation verification module: Outputs the open-loop response curve of the model and the dynamic accuracy verification results.

8. A non-transitory readable storage medium for storing computer programs, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1-6.

9. An electronic device, comprising a processor and a memory, characterized in that, The memory stores a computer program, and when the processor executes the program, it implements the steps of the method according to any one of claims 1-6.

Images