Simulation method for high and medium parameter collaborative heat supply dynamic characteristics of large-scale unit

Abstract

The invention discloses a simulation method for high and medium parameter cooperative heat supply dynamic characteristics of a large unit, which belongs to the field of thermodynamic system simulation and comprises the following steps of: splitting a plant-level cooperative heat supply system into an ultra-supercritical primary reheat unit subsystem, an ultra-supercritical secondary reheat unit subsystem and a heat supply pipe network subsystem; splitting each subsystem into a plurality of basic units; performing mechanism analysis on the basic unit, and establishing a differential equation set for describing the physical process of the basic unit; a Modelica language is used for programming, and compiling is based on a Dymola simulation platform; packaging the basic units, establishing a connector, and connecting the basic units; all the basic units are connected according to the transfer sequence of the flow variables, and a differential equation set of a connected system is automatically established through the flow variables and the potential variables set by the connectors; according to the method, non-causal modeling is adopted, the modeling process is simplified, input and output do not need to be considered when the equation is established, and a large number of formula derivation processes are reduced.

Description

Technical Field

[0001] The present invention belongs to the field of thermal system simulation, and in particular relates to a simulation method for dynamic characteristics of high and medium parameter collaborative heating of large units. Background Art

[0002] For cogeneration units, due to the thermal inertia of the heating system, in order to accurately and quickly adjust the load and propose a coordinated control strategy after the thermal and electrical load distribution is completed, it is necessary to conduct in-depth research on the dynamic characteristics of each unit and the heating pipeline network.

[0003] At present, the methods for simulating the dynamic characteristics of heating units usually adopt simplified mechanism models and experimental modeling. The simplified mechanism model requires parameter assumptions before calculation, and the calculation process is relatively complicated, making it difficult to achieve the purpose of real-time dynamic calculation; experimental modeling can only analyze the dynamic characteristics under specific working conditions by fitting experimental data; and in complex engineering applications, the heating unit model must also be combined with other thermal equipment to construct a complete collaborative heating system simulation model, which has high requirements for the modularity, reusability, and scalability of the model. These are all technical issues that need to be optimized in the modeling of the dynamic characteristics of coordinated heating units. Summary of the Invention

[0004] In response to the problems mentioned in the background technology, the present invention proposes a simulation method for the dynamic characteristics of high- and medium-parameter collaborative heating of large units. It can establish a dynamic simulation model of multiple large units jointly providing high- and medium-parameter collaborative heating and coupling with the heating network, while realizing the scalability and reusability of the dynamic simulation model of the thermal system.

[0005] Technical solution: In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A simulation method for dynamic characteristics of high and medium parameter coordinated heating of large units includes the following steps:

[0007] S1: Split the plant-level coordinated heating system into the ultra-supercritical primary reheat unit subsystem, the ultra-supercritical secondary reheat unit subsystem, and the heating pipe network subsystem, and split each subsystem into multiple basic units;

[0008] S2: Analyze the mechanism of the basic unit and establish a set of differential equations to describe its physical process;

[0009] S3: Programming in Modelica language and compiling based on Dymola simulation platform;

[0010] S4: Encapsulate the basic units and establish connectors to connect the basic units;

[0011] S5: Connect each basic unit according to the transfer order of flow variables, and automatically establish the differential equation group of the connected system through the flow variables and potential variables set by the connector.

[0012] Preferably, in S1, the ultra-supercritical primary reheat unit is divided into a primary reheat boiler, a steam turbine, a condenser, a pump, a heater, a deaerator, and a valve;

[0013] The ultra-supercritical secondary reheat unit is divided into a secondary reheat boiler and an ultra-high pressure cylinder;

[0014] The heating network is divided into pipelines, heating cylinders, heat exchangers, and users.

[0015] As a preferred method, a mechanism analysis is conducted on the primary reheat boiler basic unit, a non-causal relationship model is constructed, and the flow variables and potential variables in the basic unit are identified;

[0016] Flow variables include coal mass flow, feed water mass flow and temperature, steam mass flow and temperature, and flue gas mass flow and temperature;

[0017] Potential variables include the heat generated by coal combustion, the pressure and enthalpy of feed water, the pressure and enthalpy of steam, and the pressure and enthalpy of flue gas.

[0018] As a preferred method, a differential equation group is established to describe the relationship between various quantities through conservation laws. The specific content of the differential equation group for the primary reheat boiler is:

[0019] The mass balance equation of flue gas is:

[0020]

[0021] in, is the flue gas mass flow rate, is the air mass flow rate, is the fuel mass flow rate;

[0022] The energy balance equation of flue gas is:

[0023]

[0024] in, is the flue gas mass flow rate, h g is the specific enthalpy of the flue gas after combustion, is the air mass flow rate, h a,i is the air inlet specific enthalpy, is the fuel mass flow rate, h f Fuel inlet specific enthalpy, η c is the combustion efficiency, LHV is the lower heating value of fuel, W l is heat loss;

[0025] The momentum balance equation of flue gas is:

[0026]

[0027] Among them, P f,o is the fuel outlet pressure, P f,i is the fuel inlet pressure, Λ f is the fuel pressure loss coefficient, ρ f is the fuel density; is the fuel mass flow rate.

[0028] Preferably, in S4, for the basic units to be connected, potential variables are associated with each other at the location of each unit connector, and flow variables flow through them;

[0029] For the potential variable rule, the potential variables of all connectors connected to the same node are equal. The specific calculation process is:

[0030] connector1.potential=connector2.potential=…=connector N .potential;

[0031] Among them, connector N .potential represents the potential variable of the Nth connector of the same node;

[0032] For the flow variable rule, the algebraic sum of all flow variables connected to the same node is zero. The specific calculation process is:

[0033]

[0034] Among them, connector k .flow represents the flow variable of the kth connector of the same node, and N represents the total number of connectors of the node.

[0035] Preferably, the differential equation group is a differential algebraic equation group formed by the Modeica compiler by combining the differential equation groups of each basic unit and the connection rule equations of potential variables and flow variables to describe the overall behavior of the system.

[0036] As a preferred method, the connectors of the ultra-supercritical primary reheat unit, the ultra-supercritical secondary reheat unit and the heating network are finally connected to realize the dynamic simulation of the dynamic characteristics of high and medium parameter collaborative heating for large units.

[0037] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0038] (1) The present invention adopts non-causal modeling, which simplifies the modeling process. When analyzing the mechanism and establishing the equation, there is no need to consider the input and output, which reduces a large amount of formula derivation process.

[0039] (2) Compared with the traditional thermal system dynamic model, the thermal system dynamic model of the present invention is scalable. Thermal equipment can be added or removed through the provided connectors without recalculating the differential equations of the entire system.

[0040] (3) The components in the system of the present invention can be reused and do not need to be repeatedly modeled.

[0041] (4) The present invention has the ability to achieve unified modeling across multiple disciplines. Thermal power plants involve the coupling of multiple disciplines, including thermodynamics, fluid dynamics, mechanical dynamics, electrical systems, and control logic. Modelica supports this unified modeling, allowing the integration of subsystems such as boilers, steam turbines, generators, and cooling systems in a single environment without switching tools. Traditional methods rely on multiple specialized tools (such as ASPEN Plus, Fluent, and MATLAB) to model each separately, and then couple them through interfaces, which can easily lead to data transmission errors and low computational efficiency.

[0042] (5) The present invention adopts object-oriented and modular design: through class inheritance and instantiation, the basic unit component model can be quickly reused; the basic unit component model is encapsulated as an independent module, which is convenient for team collaborative development and model maintenance.

[0043] Compared with traditional methods: Traditional code (such as Fortran / C++) or Simulink models are difficult to achieve highly flexible modular reconstruction, and modifying local parameters may require global adjustments.

[0044] (6) The present invention performs non-causal modeling: physical intuitive modeling, directly defining equations based on the laws of conservation of energy and mass, without the need to manually derive state equations or explicit causal relationships (such as input / output ports); flexible topological connection, components are naturally connected through physical ports (such as thermal ports, fluid ports), supporting dynamic system topology changes (such as valve opening and closing, fault injection).

[0045] Compared with traditional methods: Causal modeling tools (such as Simulink) require pre-definition of signal flow, which easily introduces human assumption errors when modeling complex physical systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a modeling flow chart of the present invention;

[0047] Figure 2 It is a schematic structural diagram of the decomposition of the thermodynamic system of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further illustrated below with reference to specific examples. The examples are implemented based on the technical solutions of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0049] This embodiment provides a simulation method for the dynamic characteristics of high and medium parameter coordinated heating of large units, which includes splitting the plant-level coordinated heating system into multiple basic units; then, analyzing the basic units of the architecture to derive a set of differential equations describing the basic unit system, programming with Modelica, subassembling the built basic units and establishing connectors, and then calling the basic units to form components, which in turn form a coordinated heating system. The constructed system includes ultra-supercritical primary reheat units and ultra-supercritical secondary reheat units after heating transformation, and a heating pipeline network. The specific implementation steps are:

[0050] S1: Split the plant-level coordinated heating system into the ultra-supercritical primary reheat unit subsystem, the ultra-supercritical secondary reheat unit subsystem, and the heating pipe network subsystem, and split each subsystem into multiple basic units;

[0051] First, the thermal system is decomposed to obtain the system architecture, that is, the entire thermal system is divided into three subsystems: ultra-supercritical primary reheat unit, ultra-supercritical secondary reheat unit and heating pipeline network.

[0052] like Figure 2 As shown in the figure, based on the Modelica language, the entire thermal system is divided into several basic units by adopting a top-down design approach. Specifically, the three subsystems are split separately to obtain their basic units.

[0053] The ultra-supercritical single-reheat unit subsystem is divided into a single-reheat boiler, a steam turbine (high-pressure cylinder, middle-pressure cylinder, and low-pressure cylinder), a condenser, a pump, a heater, a deaerator, and valves (diverter valves, combining valves, and throttle valves).

[0054] The ultra-supercritical secondary reheat unit subsystem is divided into a secondary reheat boiler and an ultra-high pressure cylinder. Due to the reusability of the modeling of basic units, only the basic units that are not included in the primary reheat unit are listed for the secondary reheat unit.

[0055] The heating network subsystem is divided into pipelines, heating cylinders, heat exchangers, and users.

[0056] S2: Analyze the mechanism of each basic unit and establish a set of differential equations that can express the physical process of the basic unit;

[0057] In this embodiment, a single reheat boiler is taken as an example for analysis, a non-causal relationship model is constructed, and flow variables and potential variables in the basic unit are identified.

[0058] Flow variables include coal mass flow rate, feed water mass flow rate and temperature, steam mass flow rate and temperature, and flue gas mass flow rate and temperature.

[0059] Potential variables include the heat generated by coal combustion, the pressure and enthalpy of feed water, the pressure and enthalpy of steam, and the pressure and enthalpy of flue gas.

[0060] Through the three conservation laws, a set of differential equations is established to describe the relationship between various quantities. The following is specifically explained using a single reheat boiler as an example:

[0061] The mass balance equation of flue gas is:

[0062]

[0063] in, is the flue gas mass flow rate, is the air mass flow rate, is the fuel mass flow rate.

[0064] The energy balance equation of flue gas is:

[0065]

[0066] in, is the flue gas mass flow rate, h g is the specific enthalpy of the flue gas after combustion, is the air mass flow rate, h a,i is the air inlet specific enthalpy, is the fuel mass flow rate, h f Fuel inlet specific enthalpy, η c is the combustion efficiency, LHV is the lower heating value of fuel, W l is heat loss (such as but not limited to heat loss through walls).

[0067] The boiler power exchange between the flue gas and water / steam circuits is calculated as follows:

[0068]

[0069] in, is the air mass flow rate, h a,i is the air inlet specific enthalpy, is the fuel mass flow rate, h f Fuel inlet specific enthalpy, η c is the combustion efficiency, LHV is the lower heating value of fuel, W l is the heat loss, is the flue gas mass flow rate; h g,o is the specific enthalpy of flue gas outlet, is the water / steam mass flow rate, h ws,ois the water / steam outlet specific enthalpy, h ws,i is the water / steam inlet specific enthalpy.

[0070] The formula for calculating boiler efficiency is:

[0071]

[0072] Where, η is the boiler efficiency; is the water / steam mass flow rate, h ws,o is the water / steam outlet specific enthalpy, h ws,i is the water / steam inlet specific enthalpy; is the air mass flow rate, h a,i is the air inlet specific enthalpy, is the fuel mass flow rate, h f Fuel inlet specific enthalpy; LHV fuel lower heating value.

[0073] The momentum balance equation (pressure loss) of flue gas is:

[0074]

[0075] Among them, P f,o is the fuel outlet pressure, P f,i is the fuel inlet pressure, Λ f is the fuel pressure loss coefficient, ρ f is the fuel density; is the fuel mass flow rate.

[0076] Momentum balance equation for water / steam (pressure loss):

[0077]

[0078] Among them, P ws,o is the water / steam outlet pressure, P ws,i is the water / steam inlet pressure, Λ ws is the water / steam pressure loss coefficient, is the water / steam mass flow rate, ρ ws is the water / vapor density.

[0079] The stoichiometric ratio of dry air for burning one kilogram of fuel is:

[0080]

[0081] Among them, E X M is the dry air stoichiometric ratio (theoretical dry air requirement) required for burning one kilogram of fuel. O is the atomic mass of oxygen, M C is the mass of carbon atoms, M H is the mass of hydrogen atom, M S is the mass of sulfur atoms, XC,f is the mass fraction of C in the fuel, X H,f is the mass fraction of H in the fuel, X S,f is the mass fraction of S in the fuel, X O,f is the mass fraction of O in the fuel, X o2,a is the mass fraction of oxygen in the inlet air, X h2o,a is the mass fraction of water in the inlet air.

[0082] The mass fraction of CO2 in flue gas is calculated as follows:

[0083]

[0084] Among them, X co2,g is the mass fraction of CO2 in the flue gas, X co2,a is the mass fraction of CO2 in the inlet air, M co2 is the molar mass of CO2, X C,f is the mass fraction of C in the fuel, M C is the mass of carbon atoms, is the air mass flow rate, is the fuel mass flow rate, is the flue gas mass flow rate.

[0085] The mass fraction of H2O in flue gas is calculated as follows:

[0086]

[0087] Among them, X h2o,g is the mass fraction of water in the flue gas, M h2o is the molar mass of water; is the air mass flow rate, is the fuel mass flow rate, is the flue gas mass flow rate; X H,f is the mass fraction of H in the fuel; X h2o,a is the mass fraction of water in the inlet air.

[0088] The mass fraction of O2 in flue gas is calculated as follows:

[0089]

[0090] Among them, X o2,g is the mass fraction of oxygen in the flue gas; is the air mass flow rate, is the fuel mass flow rate, is the flue gas mass flow rate; X o2,a is the mass fraction of oxygen in the inlet air, M O is the atomic mass of oxygen, M Cis the mass of carbon atoms, M H is the mass of hydrogen atom, M S is the mass of sulfur atoms, X C,f is the mass fraction of C in the fuel, X H,f is the mass fraction of H in the fuel, X S,f is the mass fraction of S in the fuel, X O,f is the mass fraction of O in the fuel.

[0091] S3: Programming in Modelica language, compiled based on the Dymola simulation platform (multidisciplinary system simulation platform);

[0092] A model is a unit of code that uses the Modelica language to describe the physical or logical system behavior of each unit. The name of the model begins with the keyword "model," followed by a custom model name, which defines the model's unique identifier for subsequent instantiation or inheritance. Next, declare variables (time-varying quantities that describe system states or intermediate results), constants (fixed physical or mathematical constants), and parameters (intrinsic properties of the unit that remain unchanged during the simulation).

[0093] Enter the differential equations established in S2 after the equation keyword to describe the mathematical relationship between variables. There is no need to distinguish between input or output variables. The equations are bidirectional and can be written in any order. The compiler automatically resolves the dependencies and ends with the keyword end.

[0094] S4: Encapsulate the basic units and establish connectors to connect the basic units;

[0095] The module is encapsulated. When the basic unit needs to form a system with other units, external influences need to be considered.

[0096] Connectors are created. For the basic units that need to be connected, potential variables are associated at each unit connector (connectors are defined in Modelica using the "connector" keyword), through which flow variables flow. Within a connector, potential variables are continuous, meaning their values are equal at the connection point, while flow variables follow conservation laws, with the sum of flow variables at all connection points being zero.

[0097] For the potential variable rule, the potential variables of all connectors connected to the same node are equal. The specific calculation process is:

[0098] connector1.potential=connector2.potential=…=connector N .potential,

[0099] Among them, connector N .potential represents the potential variable of the Nth connector of the same node.

[0100] For the flow variable rule, the algebraic sum of all flow variables connected to the same node is zero. The specific calculation process is:

[0101]

[0102] Among them, connector k .flow represents the flow variable of the kth connector of the same node, and N represents the total number of connectors of the node.

[0103] S5: Connect the basic units in the order of flow variable transfer. Modelica will then automatically establish the differential equations of the connected system using the flow variables and potential variables set by the connectors.

[0104] In this embodiment, the differential equation group is a differential algebraic equation group formed by the Modeica compiler by combining the equations of each component and the connection rule equations (including the flow variable conservation equations and the potential variable continuity equations) to describe the overall behavior of the system.

[0105] For example, basic unit 1 and basic unit 2 form a system, where the connector of basic unit 1 is connector1 and the connector of basic unit 2 is connector2. The two basic units are connected through the connectors to form a system through the statement connect(connector1, connector2). Then the differential equations of the system include the differential equations of basic unit 1 and basic unit 2. Specifically:

[0106] connector1.potential=connector2.potential,

[0107] connector1.flow+connector2.flow=0.

[0108] Finally, the connectors of the ultra-supercritical primary reheat unit, the ultra-supercritical secondary reheat unit and the heating network are connected to realize the dynamic simulation of the high and medium parameter collaborative heating dynamic characteristics of large units.

[0109] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A simulation method for dynamic characteristics of high and medium parameter collaborative heating of large units, characterized by: The following steps are involved: S1: Split the plant-level coordinated heating system into the ultra-supercritical primary reheat unit subsystem, the ultra-supercritical secondary reheat unit subsystem, and the heating pipe network subsystem, and split each subsystem into multiple basic units; S2: Analyze the mechanism of the basic unit and establish a set of differential equations to describe its physical process; S3: Programming in Modelica language and compiling based on Dymola simulation platform; S4: Encapsulate the basic units and establish connectors to connect the basic units; S5: Connect each basic unit according to the transfer order of flow variables, and automatically establish the differential equation group of the connected system through the flow variables and potential variables set by the connector.

2. The simulation method for dynamic characteristics of high and medium parameter coordinated heating of large units according to claim 1 is characterized in that: In S1, the ultra-supercritical single reheat unit is divided into a single reheat boiler, steam turbine, condenser, pump, heater, deaerator, and valves; The ultra-supercritical secondary reheat unit is divided into a secondary reheat boiler and an ultra-high pressure cylinder; The heating network is divided into pipelines, heating cylinders, heat exchangers, and users.

3. The simulation method for dynamic characteristics of high and medium parameter coordinated heating of large units according to claim 2 is characterized in that: Conduct mechanism analysis on the primary reheat boiler basic unit, build a non-causal relationship model, and identify the flow variables and potential variables in the basic unit; Flow variables include coal mass flow, feed water mass flow and temperature, steam mass flow and temperature, and flue gas mass flow and temperature; Potential variables include the heat generated by coal combustion, the pressure and enthalpy of feed water, the pressure and enthalpy of steam, and the pressure and enthalpy of flue gas.

4. The simulation method for dynamic characteristics of high and medium parameter coordinated heating of large units according to claim 3 is characterized in that: Through the conservation law, a differential equation group is established to describe the relationship between various quantities. The specific content of the differential equation group for the primary reheat boiler is: The mass balance equation of flue gas is: in, is the flue gas mass flow rate, is the air mass flow rate, is the fuel mass flow rate; The energy balance equation of flue gas is: in, is the flue gas mass flow rate, h g is the specific enthalpy of the flue gas after combustion, is the air mass flow rate, h a,i is the air inlet specific enthalpy, is the fuel mass flow rate, h f Fuel inlet specific enthalpy, η c is the combustion efficiency, LHV is the lower heating value of fuel, W l is heat loss; The momentum balance equation of flue gas is: Among them, P f,o is the fuel outlet pressure, P f,i is the fuel inlet pressure, Λ f is the fuel pressure loss coefficient, ρ f is the fuel density; is the fuel mass flow rate.

5. The simulation method for dynamic characteristics of high and medium parameter coordinated heating of large units according to claim 1 is characterized in that: In S4, for the basic units that need to be connected, there are potential variables associated with each other at the location of each unit connector, and flow variables flow through them; For the potential variable rule, the potential variables of all connectors connected to the same node are equal. The specific calculation process is: connector1.potential=connector2.potential=…=connector N .potential; Among them, connector N .potential represents the potential variable of the Nth connector of the same node; For the flow variable rule, the algebraic sum of all flow variables connected to the same node is zero. The specific calculation process is: Among them, connector k .flow represents the flow variable of the kth connector of the same node, and N represents the total number of connectors of the node.

6. The simulation method for dynamic characteristics of high and medium parameter coordinated heating of large units according to claim 1 is characterized in that: The differential equation system is a differential algebraic equation system constructed by the Modeica compiler by combining the differential equation system of each basic unit and the connection rule equations of potential variables and flow variables to describe the overall behavior of the system.

7. The simulation method for dynamic characteristics of high and medium parameter coordinated heating of large units according to claim 1 is characterized in that: Finally, the connectors of the ultra-supercritical primary reheat unit, the ultra-supercritical secondary reheat unit and the heating network are connected to realize the dynamic simulation of the high and medium parameter collaborative heating dynamic characteristics of large units.

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