A dynamic modeling simulation method and system for steam heating system

Abstract

The present invention relates to a method and system for dynamic modeling and simulation of a steam heating system, the method comprising the following steps: step S1, establishing and simplifying a one-dimensional steam pipeline dynamic flow model; step S2, obtaining an analytical solution of the one-dimensional steam pipeline dynamic flow model using a function space transformation method; step S3, establishing a dynamic simulation model of the steam heating system based on a network topology and equipment characteristics; step S4, iteratively solving the dynamic simulation model of the steam heating system to obtain a simulation result. The method of the present invention simplifies the one-dimensional steam pipeline dynamic flow model using reference temperature, linearization of resistance terms, and ideal gas assumptions, and introduces solution time and cutoff frequency, thereby improving the solution efficiency of the dynamic simulation model while ensuring solution accuracy. The method of the present invention can be applied to dynamic simulation analysis of steam heating systems to support operation scheduling of steam heating systems.

Description

Technical Field

[0001] The present invention belongs to the field of dynamic modeling and simulation of steam heating systems, and in particular relates to a dynamic modeling and simulation method and system for steam heating systems. Background Art

[0002] Compared with hot water heating, steam heating system has the advantages of large supply, high quality and long distance. It is widely used as the main energy source and important material in the production process of industrial enterprises, thus meeting the industrial heating needs. However, steam heating also has the disadvantages of large fluctuations and unpredictability, which brings great challenges to the operation and scheduling of steam heating systems. Establishing a physical model of the steam heating system and obtaining accurate results is an important basis for obtaining its dynamic evolution process.

[0003] At present, the modeling research of steam heating system is focused on steady-state models and equipment in chemical scenes, and lacks attention to the dynamic evolution process of steam transportation network. At the same time, compared with energy flow media such as natural gas, hot water, and compressed air, the pressure, flow rate, and temperature of steam change constantly during the transportation process, and its mass, momentum, and energy equations are highly coupled and difficult to solve. Therefore, it is necessary to establish a dynamic modeling and simulation model of the steam heating system and design a corresponding efficient solution method to obtain the dynamic evolution characteristics of the steam heating system, so as to provide support for the operation and scheduling of the steam heating system and even the industrial energy supply system. Summary of the invention

[0004] The purpose of the present invention is to provide a steam heating system dynamic modeling simulation method and system to address the deficiencies in the prior art. The present invention can realize dynamic modeling of the steam heating system taking into account the dynamic characteristics of the steam network, and provide support for the operation and scheduling of the steam heating system and the industrial energy supply system.

[0005] The present invention is implemented by the following technical solutions:

[0006] Step S1, establishing and simplifying a one-dimensional steam pipeline dynamic flow model;

[0007] Step S2, obtaining an analytical solution of a one-dimensional steam pipeline dynamic flow model using a function space transformation method;

[0008] Step S3, establishing a dynamic simulation model of the steam heating system based on the network topology and equipment characteristics;

[0009] Step S4, iteratively solving the dynamic simulation model of the steam heating system to obtain simulation results.

[0010] In step S1 of establishing and simplifying the one-dimensional steam pipeline dynamic flow model:

[0011] Step S11, establishing a one-dimensional steam pipeline dynamic flow model

[0012]

[0013] Where ρ is the steam density, kg / m 3 ; t is time, s; v is steam velocity, m / s; P is pressure, Pa; g is gravity acceleration, m / s 2 ; θ is the pipeline inclination, °; ​​λ is the pipeline friction coefficient; D is the pipeline diameter, m; h is the steam enthalpy, J / kg; k is the heat dissipation coefficient, W / (m 2 ·K); T is the steam temperature, °C; T r is the ambient temperature, °C. The first equation is the mass conservation equation, the second equation is the momentum conservation equation, the third equation is the energy conservation equation, and the fourth and fifth equations are physical property equations.

[0014] Step S12, simplifying the one-dimensional steam pipeline dynamic flow model

[0015] Based on the following assumptions, a simplified one-dimensional steam pipeline dynamic flow model is proposed:

[0016] (1) The steam supplied by the steam heating system is superheated steam, and there is no condensation during the transportation process. Therefore, steam can be regarded as a single-phase compressible fluid.

[0017] (2) The steam transport velocity is much smaller than the speed of sound, so the convection term in the momentum equation can be ignored.

[0018] (3) The steam pipeline is arranged horizontally overhead or directly buried, and the resistance term caused by the pipeline inclination in the momentum and energy equations can be ignored.

[0019] (4) Linearize the squared velocity term of the resistance term in the momentum equation

[0020]

[0021] In the formula, v s is the steam velocity base value, which is the historical operating value, m / s; Δv is the fluctuation of the actual steam velocity relative to the base value. During the calculation process, v is iteratively updated. s , so that v s Closer to the actual steam flow rate.

[0022] (5) Introducing the definition of flow to simplify the equation

[0023] G=ρvA

[0024] Where G is the flow rate, kg / s; A is the cross-sectional area of ​​the pipe, m 2 .

[0025] (6) Steam is generally regulated in quantity during operation and scheduling, and the temperature change at the steam heat source outlet is very small and can be ignored. At the same time, the heat dissipation during steam transportation is not considered. Based on this, it is assumed that the temperature of steam in the steam heating system is fixed as the reference temperature, that is, the steam temperature does not change during dynamic transportation. The reference temperature is calculated using the weighted average of the steam heat source and the user.

[0026]

[0027] Where: c i is the specific heat capacity of steam, J / (kg·K); G i is the flow rate of the ith user or steam heat source, kg / s; T i is the temperature of the i-th user or steam heat source, K; ns is the number of steam heat sources; nu is the number of users;

[0028] (7) Steam operating conditions include low pressure, medium pressure and high pressure. Under any operating condition, steam can be regarded as an ideal gas, and its state equation can be described as

[0029] P=ρR g T b

[0030] The gas constant is calculated as follows:

[0031]

[0032] Based on the above simplification, the energy change of steam during the transportation process is ignored. Taking the flow rate G and pressure P as variables in the mass and momentum equations, the one-dimensional steam dynamic flow equation is simplified to

[0033]

[0034] In step S2, in which the function space transformation method is used to obtain the analytical solution of the steam pipeline dynamic flow model:

[0035] The function space transformation method is used to transform the dynamic flow model of the steam pipeline from the time domain to the frequency domain, so that the partial differential equations describing the steam flow are transformed into ordinary differential equations. The function space transformation method includes Fourier transform and Laplace transform. Here, Fourier transform is used as an example.

[0036] The simplified one-dimensional steam dynamic flow equation in step S1 is transformed by Fourier transform to obtain the equation system under a single frequency:

[0037]

[0038] Where j is the imaginary unit; w is the frequency;

[0039] According to the boundary conditions of flow and pressure G0 and P0, the above ordinary differential equations are solved to obtain the analytical solution of the distribution of flow and pressure in the pipeline.

[0040]

[0041] In the formula, l is the position.

[0042] In step S3, in which a dynamic simulation model of a steam heating system is established based on the network topology and equipment characteristics:

[0043] Step S31: Establishing a network topology

[0044] According to graph theory, two correlation matrices are defined to describe the fluid topology.

[0045]

[0046]

[0047]

[0048]

[0049] Where A is the node-branch association matrix; n is the number of nodes; m is the number of branches; a nm is the correlation coefficient between node n and branch m; B is the loop correlation matrix; s is the number of loops; b sm is the relationship between pipeline s and loop.

[0050] AG n T +G net =0

[0051] In the formula, G n is the pipeline flow vector, kg / s; G net is the pipeline net flow vector, kg / s.

[0052] BP n =0

[0053] Where P n is the pipeline net pressure drop vector, Pa.

[0054] Step S32: Establishing a device model

[0055] Steam production equipment in the steam heating system includes gas boilers and cogeneration units. The steam production of gas boilers is related to the amount of gas.

[0056] G GB (t) = C GB (t)η GB

[0057] In the formula, G GB (t) is the steam production of the gas boiler, kg / s; C GB (t) is the natural gas consumption of the gas boiler, kg / s; η GB For the operating efficiency of gas boilers.

[0058] The fuel consumed by the cogeneration unit may be coal or natural gas, and it produces electricity while producing steam.

[0059] G CHP (t) = C CHP (t)η CHP

[0060] In the formula, G CHP (t) is the steam production of the cogeneration unit, kg / s; C CHP (t) is the natural gas consumption or coal consumption of the cogeneration unit, kg / s; η CHP It is the operating efficiency of the cogeneration unit. The operating efficiency of coal-fired and gas-fired cogeneration units is different.

[0061] Step S33, based on the analytical solution of flow and pressure distribution obtained in step S2, combined with the network topology structure in step S31 and the equipment model in step S32, a dynamic simulation model of the steam heating system can be established.

[0062] In step S4, in which the dynamic simulation model of the steam heating system is iteratively solved to obtain the simulation results:

[0063] Step S41, preprocessing the original steam heating system data, deleting duplicate values ​​and filling missing values ​​with an interpolation method;

[0064] Step S42, determining the steam operating conditions according to the steam heating system data, calculating its gas constant; and calculating the reference temperature according to the temperature of the steam heat source and the user; at the same time, calculating the solution time and the cutoff frequency based on the input data; and transforming the input data in the time domain into the frequency domain using the function space transformation method;

[0065] To distinguish it from the actual operation time of the steam heating system, the solution time is defined as the data time length of the input dynamic simulation model.

[0066] τ=τ tf +τ st

[0067] Where τ is the solution time, s; τ tf is the steady-state running time added at the beginning and end of the running time, s; τ stis the running time, s. Extending the running time to the solution time can ensure the integrity and stability of the solution results. When supplementing data at the beginning and end of the running time, the real data at the beginning and end are used as the steady-state operating conditions, and extended by τ tf / 2 length. When outputting the final result, the solution within the running time can be obtained by removing the steady-state running time at the beginning and the end.

[0068] In the frequency domain, a large amount of information of the steam heating system operation data is retained in a few frequencies. Therefore, in order to improve the calculation efficiency, the cutoff frequency is defined as the number of frequency components in the solution.

[0069]

[0070] In the formula, f tr is the cutoff frequency; f tr,i is the cutoff frequency of the i-th input data; is the jth frequency component of the i-th input data; is the amplitude of the jth frequency component of the ith input data; ε is the truncation error.

[0071] The cutoff frequency takes the maximum value of the cutoff frequencies of all input data, which can ensure the solution accuracy of the simulation model. ε is a parameter that controls the solution accuracy and solution efficiency.

[0072] Step S43, calculating the steam velocity base value, and solving the flow and pressure distribution of the steam heating system in a single frequency domain;

[0073] Step S44, superimposing the solution results of multiple frequency components in the frequency domain and converting them to the time domain by the function space inverse transformation method to obtain the flow and pressure distribution results;

[0074] Step S45, determine the iterative exit condition, if not met, enter the next iteration, modify the steam velocity base value, and repeat steps S43 to S45; if met, convert the result to the result under the running time for output. The steam flow rate base value error is used as the iterative exit condition. The steam flow rate base value is an important parameter in the solution of the dynamic simulation model. If it is only given by historical conditions, the solution accuracy will be seriously affected. Therefore, the steam flow rate base value needs to be continuously corrected during the dynamic simulation model solution calculation process.

[0075]

[0076] In the formula, is the base value of steam velocity in the i-th iteration, m / s; av i Solve the average value of pipeline flow velocity results for the dynamic simulation model; is the iteration error.

[0077] The iteration exit condition is the iteration error The set allowable error is met or the number of iterations reaches the set number.

[0078] The dynamic simulation model solving module calculates the solving time and cutoff frequency, solves the dynamic simulation model of the steam heating system, and determines whether the calculation is completed according to the iterative exit conditions. After the solution is completed, the solution results within the running time are output.

[0079] The present invention also provides a steam heating system dynamic modeling simulation system, the system comprises a data preprocessing module, a steam heating system dynamic modeling module, and a dynamic simulation model solving module; the above modules are respectively packaged to establish a data transmission channel;

[0080] The data preprocessing module processes the input raw operation data of the steam heating system, deletes duplicate values ​​and fills in missing values ​​using interpolation methods to ensure data integrity; at the same time, it reads the steam heating system structure data and transmits it to the steam heating system dynamic modeling module;

[0081] The steam heating system dynamic modeling module establishes a dynamic simulation model based on the steam heating system structure data based on the network topology and equipment characteristics, and transmits the established dynamic simulation model to the dynamic simulation model solving module;

[0082] The dynamic simulation model solving module calculates the solving time and the cut-off frequency, solves the dynamic simulation model of the steam heating system, and determines whether the calculation is completed according to the iterative exit conditions; after the solution is completed, the solution result within the running time is output.

[0083] The beneficial effects of the present invention are:

[0084] The present invention establishes a method and system for dynamic modeling and simulation of a steam heating system. Based on the mass, momentum and energy conservation equations, a dynamic flow model of a steam pipeline is established. The model is simplified by using reference temperature, linearization of resistance terms and ideal gas assumptions, and an analytical solution is obtained by using the function space transformation method. Based on the steam network topology and equipment characteristics, the dynamic flow model of the steam pipeline is expanded into a dynamic simulation model of a steam heating system, and the model is solved by an iterative method to obtain the dynamic evolution process of the steam heating system. The present invention can predict the dynamic evolution of a steam heating system and provide support for the operation and scheduling of a steam heating system and even an industrial energy supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 Dynamic modeling and solution flow chart for the steam heating system of the present invention;

[0086] Figure 2 This is the structural diagram of a steam heating system;

[0087] Figure 3 This is a comparison chart of the dynamic simulation results of the steam heat source of a steam heating system;

[0088] Figure 4 This is a dynamic simulation error probability density and its cumulative distribution curve for a steam heating system. DETAILED DESCRIPTION

[0089] In order to make the content of the present invention more clearly understood, the technical solution of the present invention is further introduced below in conjunction with specific examples and drawings. Figure 1 As shown, the technical method of the present invention includes 4 steps:

[0090] Step S1, establishing and simplifying a one-dimensional steam pipeline dynamic flow model;

[0091] Step S2, obtaining an analytical solution of a one-dimensional steam pipeline dynamic flow model using a function space transformation method;

[0092] Step S3, establishing a dynamic simulation model of the steam heating system based on the network topology and equipment characteristics;

[0093] Step S4, iteratively solving the dynamic simulation model of the steam heating system to obtain simulation results.

[0094] Combine the following Figure 2 The present invention is further introduced by the steam heating system of the topological structure shown in FIG. The operating condition of the steam heating system on a certain day in December is selected as a research case.

[0095] In step S1 of establishing and simplifying the one-dimensional steam pipeline dynamic flow model:

[0096] Step S11, establishing a one-dimensional steam pipeline dynamic flow model

[0097]

[0098] Where ρ is the steam density, kg / m 3 ; t is time, s; v is steam velocity, m / s; P is pressure, Pa; g is gravity acceleration, m / s 2 ; θ is the pipeline inclination, °; ​​λ is the pipeline friction coefficient; D is the pipeline diameter, m; h is the steam enthalpy, J / kg; k is the heat dissipation coefficient, W / (m 2 ·K); T is the steam temperature, °C; T r is the ambient temperature, °C. The first equation is the mass conservation equation, the second equation is the momentum conservation equation, the third equation is the energy conservation equation, and the fourth and fifth equations are physical property equations.

[0099] Step S12, simplifying the one-dimensional steam pipeline dynamic flow model

[0100] Based on the following assumptions, a simplified one-dimensional steam pipeline dynamic flow model is proposed:

[0101] (1) The steam supplied by the steam heating system is superheated steam, and there is no condensation during the transportation process. Therefore, steam can be regarded as a single-phase compressible fluid.

[0102] (2) The steam transport velocity is much smaller than the speed of sound, so the convection term in the momentum equation can be ignored.

[0103] (3) The steam pipeline is arranged horizontally overhead or directly buried, and the resistance term caused by the pipeline inclination in the momentum and energy equations can be ignored.

[0104] (4) Linearize the squared velocity term of the resistance term in the momentum equation

[0105]

[0106] In the formula, v s is the steam velocity base value, which is the historical operating value, m / s; Δv is the fluctuation of the actual steam velocity relative to the base value. During the calculation process, v is iteratively updated. s , so that v s Closer to the actual steam flow rate.

[0107] (5) Introducing the definition of flow to simplify the equation

[0108] G=ρvA

[0109] Where G is the flow rate, kg / s; A is the cross-sectional area of ​​the pipe, m 2 .

[0110] (6) Steam is generally regulated in quantity during operation and scheduling, and the temperature change at the steam heat source outlet is very small and can be ignored. At the same time, the heat dissipation during steam transportation is not considered. Based on this, it is assumed that the temperature of steam in the steam heating system is fixed as the reference temperature, that is, the steam temperature does not change during dynamic transportation. The reference temperature is calculated using the weighted average of the steam heat source and the user.

[0111]

[0112] Where: c i is the specific heat capacity of steam, J / (kg·K); G i is the flow rate of the ith user or steam heat source, kg / s; T i is the temperature of the i-th user or steam heat source, K; ns is the number of steam heat sources; nu is the number of users;

[0113] (7) Steam operating conditions include low pressure, medium pressure and high pressure. Under any operating condition, steam can be regarded as an ideal gas, and its state equation can be described as

[0114] P=ρR g T b

[0115] The gas constant is calculated as follows:

[0116]

[0117] Based on the above simplification, the energy change of steam during the transportation process is ignored. Taking the flow rate G and pressure P as variables in the mass and momentum equations, the one-dimensional steam dynamic flow equation is simplified to

[0118]

[0119] In step S2, in which the function space transformation method is used to obtain the analytical solution of the steam pipeline dynamic flow model:

[0120] The function space transformation method is used to transform the dynamic flow model of the steam pipeline from the time domain to the frequency domain, so that the partial differential equations describing the steam flow are transformed into ordinary differential equations. The function space transformation method includes Fourier transform and Laplace transform. Here, Fourier transform is used as an example.

[0121] The simplified one-dimensional steam dynamic flow equation in step S1 is transformed by Fourier transform to obtain the equation system under a single frequency:

[0122]

[0123] Where j is the imaginary unit; w is the frequency;

[0124] According to the boundary conditions of flow and pressure G0 and P0, the above ordinary differential equations are solved to obtain the analytical solution of the distribution of flow and pressure in the pipeline.

[0125]

[0126] In the formula, l is the position.

[0127] In step S3, in which a dynamic simulation model of a steam heating system is established based on the network topology and equipment characteristics:

[0128] According to graph theory, two correlation matrices are defined to describe the fluid topology.

[0129]

[0130]

[0131]

[0132]

[0133] Where A is the node-branch association matrix; n is the number of nodes; m is the number of branches; a nm is the correlation coefficient between node n and branch m; B is the loop correlation matrix; s is the number of loops; b sm is the relationship between pipeline s and loop.

[0134] AG n T +G net =0

[0135] In the formula, G n is the pipeline flow vector, kg / s; G net is the pipeline net flow vector, kg / s.

[0136] BP n =0

[0137] Where P n is the pipeline net pressure drop vector, Pa.

[0138] exist Figure 2 In the case of , the outlet flow of the steam heat source is directly given, and there is no need to calculate it through coal consumption. Therefore, based on the analytical solution of the flow and pressure distribution obtained in step S2, combined with the network topology structure in step S31, a dynamic simulation model of the steam heating system can be established.

[0139] In step S4, in which the dynamic simulation model of the steam heating system is iteratively solved to obtain the simulation results:

[0140] Step S41, preprocessing the original steam heating system data, deleting duplicate values ​​and filling missing values ​​with an interpolation method;

[0141] Step S42, determining the steam operating conditions according to the steam heating system data, calculating its gas constant; and calculating the reference temperature according to the temperature of the steam heat source and the user; at the same time, calculating the solution time and the cutoff frequency based on the input data; and transforming the input data in the time domain into the frequency domain using the function space transformation method;

[0142] To distinguish it from the actual operation time of the steam heating system, the solution time is defined as the data time length of the input dynamic simulation model.

[0143] τ=τ tf +τ st

[0144] Where τ is the solution time, s; τ tf is the steady-state running time added at the beginning and end of the running time, s; τ stis the running time, s. Extending the running time to the solution time can ensure the integrity and stability of the solution results. When supplementing data at the beginning and end of the running time, the real data at the beginning and end are used as the steady-state operating conditions, and extended by τ tf / 2 length. When outputting the final result, remove the steady-state running time at the beginning and end to obtain the solution result within the running time. Figure 2 The operating time of the operating condition used in the calculation is 10 hours, and the solution time is 10 hours and 10 minutes.

[0145] In the frequency domain, a large amount of information of the steam heating system operation data is retained in a few frequencies. Therefore, in order to improve the calculation efficiency, the cutoff frequency is defined as the number of frequency components in the solution.

[0146]

[0147] In the formula, f tr is the cutoff frequency; f tr,i is the cutoff frequency of the i-th input data; is the jth frequency component of the i-th input data; is the amplitude of the jth frequency component of the ith input data; ε is the truncation error.

[0148] The cutoff frequency takes the maximum value of the cutoff frequencies of all input data, which can ensure the solution accuracy of the simulation model. ε is a parameter that controls the solution accuracy and solution efficiency. Figure 2 In the case of , the truncation error is 0.01% and the number of truncation frequencies is 120.

[0149] Step S43, calculating the steam velocity base value, and solving the flow and pressure distribution of the steam heating system in a single frequency domain;

[0150] Step S44, superimposing the solution results of multiple frequency components in the frequency domain and converting them to the time domain by the function space inverse transformation method to obtain the flow and pressure distribution results;

[0151] Step S45, determine the iteration exit condition, if not met, enter the next iteration, modify the steam speed base value, and repeat steps S43 to S45; if met, convert the result to the result under the running time for output.

[0152] The steam flow rate base value error is used as the iterative exit condition. The steam flow rate base value is an important parameter in the dynamic simulation model solution. If it is only given by historical conditions, the solution accuracy will be seriously affected. Therefore, the steam flow rate base value needs to be constantly corrected during the dynamic simulation model solution calculation process.

[0153]

[0154] In the formula, is the base value of steam velocity in the i-th iteration, m / s; av i Solve the average value of pipeline flow velocity results for the dynamic simulation model; is the iteration error.

[0155] The iteration exit condition is the iteration error The set tolerance is met or the number of iterations reaches the set number. Figure 2 In the case of , the iteration tolerance is set to 0.1 and the maximum number of iterations is set to 100.

[0156] Based on the above steps, we can obtain Figure 2 Dynamic simulation results for the cases shown are compared with actual operating data. Figure 3 The comparison results of heat source outlet flow are shown. Figure 3 The relative errors shown in are the absolute values ​​of the relative errors. Figure 4 The error of the simulation result is controlled within 5% and is mainly distributed in [-3%, 2%], which meets the requirements of industrial steam dynamic simulation. Figure 2 The case proves the effectiveness of the dynamic simulation model of the steam heating system proposed in this invention.

[0157] The relative error calculation formula is:

[0158]

[0159] Where: σ is the relative error; y r is the actual operation data; s Simulation data for dynamic models.

[0160] The method of the present invention predicts and simulates the dynamic evolution process of the steam heating system by establishing a dynamic simulation model of the steam heating system, thereby providing support for its operation scheduling.

Claims

1. A dynamic modeling and simulation method for a steam heating system, characterized in that: The following steps are involved: Step S1, establishing and simplifying a one-dimensional steam pipeline dynamic flow model; Step S2, obtaining an analytical solution of a one-dimensional steam pipeline dynamic flow model using a function space transformation method; Step S3, establishing a dynamic simulation model of the steam heating system based on the network topology and equipment characteristics; Step S4, iteratively solving the dynamic simulation model of the steam heating system to obtain simulation results; The step S1 specifically includes the following steps: Step S11, establishing a one-dimensional steam pipeline dynamic flow model Where ρ is the steam density, kg / m 3 ; t is time, s; v is steam velocity, m / s; P is pressure, Pa; g is gravity acceleration, m / s2; θ is the pipeline inclination, °; ​​λ is the pipeline friction coefficient; D is the pipeline diameter, m; h is steam enthalpy, J / kg; k is the heat dissipation coefficient, W / (m 2 ·K); T is the steam temperature, °C; T r is the ambient temperature, °C; Step S12, simplifying the one-dimensional steam pipeline dynamic flow model; Based on the following assumptions, a simplified one-dimensional steam pipeline dynamic flow model is proposed: (1) The steam supplied by the steam heating system is superheated steam, and there is no condensation during the transportation process; therefore, the steam can be regarded as a single-phase compressible fluid; (2) The steam transport velocity is much smaller than the speed of sound, so the convection term in the momentum equation can be ignored; (3) The steam pipeline is arranged horizontally overhead or directly buried, and the resistance term caused by the pipeline inclination in the momentum and energy equations can be ignored; (4) Linearize the squared velocity term of the drag term in the momentum equation; In the formula, v s is the base value of steam velocity, taking the historical operating value, m / s; Δv is the fluctuation of the actual steam velocity relative to the base value; (5) Introducing the definition of flow to simplify the equation G=ρvA Where G is the flow rate, kg / s; A is the cross-sectional area of ​​the pipe, m 2 ; (6) Assume that the temperature of steam in the steam heating system is fixed as the reference temperature, that is, the steam temperature does not change during the dynamic transport process; the reference temperature T b Calculated using the weighted average of steam heat sources and users Where: c i is the specific heat capacity of steam, J / (kg·K); G i is the flow rate of the ith user or steam heat source, kg / s; T i is the temperature of the i-th user or steam heat source, K; ns is the number of steam heat sources; nu is the number of users; (7) Steam operating conditions include low pressure, medium pressure and high pressure. Under any operating condition, steam is regarded as an ideal gas, and its state equation is described as QρR g T b The gas constant is calculated as follows: Based on the above simplification, the energy change of steam during the transportation process is ignored; the flow rate G and pressure P are used as variables in the mass and momentum equations, and the one-dimensional steam dynamic flow equation is simplified to 2. A steam heating system dynamic modeling simulation method according to claim 1, characterized in that: The step S2 specifically includes the following steps: The steam pipeline dynamic flow model is converted from the time domain to the frequency domain using the function space transformation method, so that the partial differential equations describing the steam flow are transformed into ordinary differential equations. The simplified one-dimensional steam dynamic flow equation in step S1 is transformed by Fourier transform to obtain the equation system under a single frequency: Where, j is the imaginary unit; w is the frequency; According to the boundary conditions of flow and pressure G0 and P0, the above ordinary differential equations are solved to obtain the analytical solution of the distribution of flow and pressure in the pipeline. In the formula, l is the position.

3. A steam heating system dynamic modeling simulation method and system according to claim 1, characterized in that: The step S3 specifically includes the following steps: Step S31: Establishing a network topology According to graph theory, two correlation matrices are defined to describe the fluid topology. Where A is the node-branch association matrix; n is the number of nodes; m is the number of branches; a nm is the correlation coefficient between node n and branch m; B is the loop correlation matrix; s is the number of loops; b sm is the relationship between pipeline s and loop; AT n T +G net =0 In the formula, G n is the pipeline flow vector, kg / s; G net is the pipeline net flow vector, kg / s; BP n =0 Where P n is the pipeline net pressure drop vector, Pa; Step S32: Establishing a device model Steam production equipment in the steam heating system includes gas boilers and cogeneration units; the steam production of gas boilers is related to the amount of gas. G GB (t)=C GB (t)η GB In the formula, G GB (t) is the steam production of the gas boiler, kg / s; C GB (t) is the natural gas consumption of the gas boiler, kg / s; η GB For the operating efficiency of gas boilers; The combined heat and power unit consumes coal or natural gas as fuel, and produces electricity while producing steam. G CHP (t)=C CHP (t)η CHP In the formula, G CHP (t) is the steam production of the cogeneration unit, kg / s; C CHP (t) is the natural gas consumption or coal consumption of the cogeneration unit, kg / s; η CHP is the operating efficiency of the cogeneration unit. The operating efficiencies of coal-fired and gas-fired cogeneration units are different. Step S33, based on the analytical solution of flow and pressure distribution obtained in step S2, combined with the network topology structure in step S31 and the equipment model in step S32, a dynamic simulation model of the steam heating system can be established.

4. A steam heating system dynamic modeling simulation method and system according to claim 1, characterized in that: The step S4 specifically includes the following steps: Step S41, preprocessing the original steam heating system data, deleting duplicate values ​​and filling missing values ​​with an interpolation method; Step S42, determining the steam operating conditions according to the steam heating system data, calculating its gas constant; and calculating the reference temperature according to the temperature of the steam heat source and the user; at the same time, calculating the solution time and the cutoff frequency based on the input data; and transforming the input data in the time domain into the frequency domain using the function space transformation method; Step S43, calculating the steam velocity base value, and solving the flow and pressure distribution of the steam heating system in a single frequency domain; Step S44, superimposing the solution results of multiple frequency components in the frequency domain and converting them to the time domain by the function space inverse transformation method to obtain the flow and pressure distribution results; Step S45, determine the iteration exit condition, if not met, enter the next iteration, modify the steam speed base value, and repeat steps S43 to S45; if met, convert the result to the result under the running time for output.

5. A steam heating system dynamic modeling simulation method and system according to claim 4, characterized in that: In the step S42: To distinguish it from the actual operation time of the steam heating system, the solution time is defined as the data time length of the input dynamic simulation model. τ=τ tf +t st Where τ is the solution time, s; τ tf is the steady-state running time added at the beginning and end of the running time, s; τ st is the running time, s; When supplementing data at the beginning and end of the running time, the real data at the beginning and end are used as the steady-state operating conditions, and the data are extended by τ tf / 2 length; when outputting the final result, the solution result within the running time can be obtained by removing the steady-state running time at the beginning and the end.

6. A steam heating system dynamic modeling simulation method and system according to claim 4, characterized in that: In the step S42: Define the cutoff frequency as the number of frequency components in the solution In the formula, f tr is the cutoff frequency; f tr,i is the cutoff frequency of the i-th input data; is the jth frequency component of the i-th input data; is the amplitude of the jth frequency component of the ith input data; ε is the truncation error.

7. A steam heating system dynamic modeling simulation method and system according to claim 4, characterized in that: In the step S45: In the process of solving the dynamic simulation model, the steam flow rate base value needs to be constantly corrected and used as the outlet condition for iterative calculation. In the formula, is the base value of steam velocity in the i-th iteration, m / s; av i Solve the average value of pipeline flow velocity results for the dynamic simulation model; is the iteration error; The iteration exit condition is the iteration error The set allowable error is met or the number of iterations reaches the set number.

8. A dynamic modeling and simulation system for a steam heating system, which uses the method according to any one of claims 1 to 7 to perform dynamic modeling and simulation on a steam heating system, characterized in that: The system includes a data preprocessing module, a steam heating system dynamic modeling module, and a dynamic simulation model solving module; the above modules are respectively packaged to establish a data transmission channel; The data preprocessing module processes the input raw operation data of the steam heating system, deletes duplicate values ​​and fills in missing values ​​using interpolation methods to ensure data integrity; at the same time, it reads the steam heating system structure data and transmits it to the steam heating system dynamic modeling module; The steam heating system dynamic modeling module establishes a dynamic simulation model based on the steam heating system structure data based on the network topology and equipment characteristics, and transmits the established dynamic simulation model to the dynamic simulation model solving module; The dynamic simulation model solving module calculates the solving time and the cut-off frequency, solves the dynamic simulation model of the steam heating system, and determines whether the calculation is completed according to the iterative exit conditions; after the solution is completed, the solution result within the running time is output.

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