A direct calculation method of exergy flow in integrated energy system based on non-equilibrium node exergy

Abstract

The present invention discloses a method for directly calculating the flow of an integrated energy system based on unbalanced nodes, comprising: under the condition of known unbalanced nodes, establishing a direct calculation model of hydraulic-thermal-flow of a thermal system and solving to obtain the flow distribution of the thermal system; establishing a direct calculation model of three-phase flow of an electric power system and solving to obtain the flow distribution of the electric power system; establishing a direct calculation model of air pressure-flow of a natural gas system and using the Newton node method to solve to obtain the flow distribution of the natural gas system; updating the flow interaction information among the thermal system, the electric power system and the natural gas system in the integrated energy system by a hub model, updating the flow distribution of the thermal system, the electric power system and the natural gas system consumed or supplied by the energy station in each energy system during the iteration process until the operation conditions of the current integrated energy system are met; and obtaining the flow and potential distribution of the entire integrated energy system.

Description

Technical Field

[0001] The present invention relates to the field of integrated energy systems, energy system effective energy and energy quality analysis, and in particular to integrated energy systems under known unbalanced node power conditions. Stream direct calculation method. Background Art

[0002] The increasingly prominent environmental and resource problems have led to an increasing urgency for the use of efficient green energy throughout society. As a form of multi-energy utilization, the integrated energy system has received widespread attention from all walks of life. The quality of different forms of energy in the integrated energy system varies. As a measure that takes into account both the “quantity” and “quality” of energy, the current research on energy in integrated energy systems is Most of the research focuses on the changes in a specific energy conversion process, or regards the integrated energy system as a black box model. Efficiency is used as an evaluation index to guide system optimization or control. Theory of transmission in multi-energy pipelines. Some studies have considered the network properties of integrated energy systems and proposed flow mechanism and analysis methods, defining Momentum, The concepts of potential difference and so on are used to analyze the overall and local characteristics of the integrated energy system. Balanced relationship.

[0003] Integrated Energy Systems The flow mechanism and analysis method proposed make it possible to intuitively understand the flow and loss of effective energy in each energy network under steady state. The flow distribution reflects the energy quality characteristics of each energy link, which can realize high-quality energy flow trajectory tracking and provide an analytical basis for optimizing the quality of the energy system. The establishment of a flow calculation model is the basis for quantitative research on energy quality of large-scale systems. At present, the calculation models of multi-energy flows and carbon flows in integrated energy systems are relatively complete. Some studies have proposed an extended Newton-Raphson algorithm suitable for multi-energy flow calculations in electric-gas-heat coupled energy systems; some studies have established a unified energy path model for electric-gas-heat coupled systems to obtain the energy flow distribution of the system. Carbon flow calculation relies on energy flow. Some studies have established a theoretical framework for carbon flow based on power flow. Some studies have established a carbon flow calculation model for power systems based on this framework. Some studies have expanded the carbon flow calculation theory to multi-energy coupling systems based on multi-energy flows. It can be foreseen that As part of energy, it is built on the basis of multi-energy flow The stream computing model is feasible.

[0004] based on Flow computing models can effectively solve the problems of integrated energy systems. The energy quality characteristics of the whole system or part of it can be analyzed by analyzing the distribution of energy flow, that is, the distribution of effective energy. Therefore, it is necessary to study the different links of the integrated energy system. Flow computing methods to build integrated energy systems The flow computing model aims to provide a convenient and efficient analysis tool for the energy quality characteristics analysis of the integrated energy system. The present invention aims to propose a scenario based on unbalanced nodes. Integrated energy system Stream direct calculation method. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method based on an unbalanced node. Integrated energy system Stream direct calculation method.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] An unbalanced node Integrated energy system Stream direct calculation method, including:

[0008] S1, known unbalanced nodes Under the condition of thermal system Flow mechanism model, establish the thermal system hydraulic-thermal- Direct flow calculation model, using hydraulic model and thermal- Alternating Iterative Algorithm for Flow Model to Solve the Hydraulic-Thermal- The flow direct calculation model obtains the thermal system Flow distribution;

[0009] S2, known unbalanced nodes Under the condition of Flow calculation model, establish the power system three-phase The flow direct calculation model is proposed, and the solution algorithm is proposed; one of the algorithms, the Newton method, the PQ decomposition method or the forward back substitution method, is used to solve the three-phase power system The flow direct calculation model is used to obtain the power system Flow distribution;

[0010] S3, known unbalanced nodes Under the conditions of natural gas system Flow calculation model, establish the natural gas system pressure- The flow direct calculation model is proposed, and the solution algorithm is proposed; the Newton node method is used to solve the gas pressure- The direct calculation model of the flow of natural gas system Flow distribution;

[0011] S4. The hub model updates and iterates the connections between the thermal system, power system and natural gas system in the integrated energy system. The energy consumption or supply of each energy system is updated during the iteration process. , solving the thermal system, power system and natural gas system until the operating conditions of the current integrated energy system are met; obtain the entire integrated energy system Flow Potential distribution.

[0012] Furthermore, the thermal system Flow distribution consists of three parts:

[0013] Damage, including supply and return pipes Loss and Load damage;

[0014] Heat Source and load ;

[0015] element Flow, including supply and return pipes Flow, flow into heat source Flow, inflow load Inflow and outflow loads flow.

[0016] Furthermore, the thermal system hydraulic-thermal- The hydraulic model and thermal model are used in the direct calculation model of flow Solving the Thermodynamic System Using Alternating Iteration Method of Flow Model Flow distribution;

[0017] (101) Hydraulic model

[0018] The water flow satisfies the generalized Kirchhoff's first law at the thermal nodes. The thermal nodes include the water supply node, the return node, and the outlet node. The water pressure satisfies the generalized Kirchhoff's second law in the water supply network and the return network loop, which is described by the flow continuity equation and the water pressure drop equation:

[0019]

[0020] Where: A h is the node-branch association matrix of the water supply network; mh is the water flow rate column vector of the water supply pipeline; B h is the loop-branch association matrix of the water supply network; h f is the water pressure loss column vector of the water supply network; Formula (1) is solved by the Newton method; m h,N is the heat source water flow column vector;

[0021] (102) Heat - Flow model, that is, water flow rate-temperature and Relational Model of Streams

[0022] The thermal model of the thermal system includes: thermal source load power equation, pipeline water temperature drop equation and node water temperature mixed equation to describe the temperature changes at the thermal pipeline and nodes; if the non-equilibrium node It is known that the water supply temperature vector T in the thermal source load power equation s The product of the specific heat capacity of water c p and the outlet temperature vector T o The difference between the product of the specific heat capacity of water and the water supply node Potential vector p s and exit node Potential vector p o The difference between the thermal power vector Δφ and the thermal power vector Δφ is replaced by the thermal power vector Vector Δe h,N , that is, replaced by the thermal source load Flow equation, and then get the thermal- Flow model, as shown in formula (2);

[0023]

[0024] Where: T start and T end are the water temperatures at both ends of the pipe; T a is the ambient temperature; t λ is the thermal conductivity; L h is the length of the thermal pipeline; T in and T out are the water temperatures at the inflow node and outflow node respectively; m in and m out are the water flow rates into and out of the node respectively; Δe h,N Heat source Column vector, heat source outlet and return node The potential is equal, the heat absorbed by the heat source and the heat released by the load Both can be charged by the above heat source Flow equation representation.

[0025] Furthermore, it is known that the unbalanced node , combined with the hydraulic model shown in formula (1) and the thermal model shown in formula (2) Flow model, using alternating iterative method to solve the thermal system potential and water flow rate, and then based on the thermal system Flow mechanism model solution Flow distribution; the specific solution process is as follows:

[0026] 1) Obtain thermal system topology, pipeline parameters, balanced nodes, and unbalanced nodes , heat source water supply node temperature, load outlet node temperature parameters;

[0027] 2) Initialize the load water supply temperature, heat source and load return water temperature, and pipeline water flow rate parameters;

[0028] 3) By unbalanced nodes Constructing a reduced-order thermal source Column vector Δe' h,N , by Δe h,N The unbalanced node elements are composed of;

[0029] 4) Calculate the reduced-order thermal nodes based on the thermal node water temperature and ambient temperature Potential column vector p' s 、p' o and p' r , the reduced order represents the column vector composed of node parameters outside the equilibrium node. According to the thermal source load in formula (2), Flow equation, calculate the reduced-order thermal source water flow rate column vector m' h,N :

[0030] m' h,N =diag(p' s -p' o ) -1 Δe' h,N (19)

[0031] Where: p' s and p' o They are p s and p o The column vector of unbalanced node elements; p' r Non-balanced node return node The vector formed by the potential; m' h,N By m h,N The unbalanced node elements are composed of;

[0032] 5) Construct the water flow rate residual column vector from formula (1):

[0033]

[0034] Where: A' h,1 is the reduced-order node-branch association matrix of the water supply network; K h is the column vector of pipeline resistance coefficient;

[0035] 6) Construct the Jacobian matrix J of the thermal system h :

[0036]

[0037] 7) Update the water flow rate of the water supply pipe by the Jacobian matrix:

[0038]

[0039] Where: is a column vector consisting of water flow rate correction values ​​in the water supply pipeline; and are the water flow rate vectors of the water supply pipeline at the kth and k+1th iterations respectively; is the invertible matrix of the Jacobian matrix at the kth iteration; is the residual column vector of water flow rate at the kth iteration;

[0040] 8) Based on equation (2), the equation group (7) is constructed to solve the reduced-order node temperature column vector T' of the thermal system: s , T' o and T' r :

[0041]

[0042] Where: C s , C r 、b s 、b r is the water supply network characteristic matrix, the return network characteristic matrix, the water supply parameter characteristic vector, and the return parameter characteristic vector; T s * and T r * are the characteristic column vector of supply water temperature and the characteristic column vector of return water temperature respectively;

[0043] 9) Calculate the maximum value of the iterative residual Δf by formula (8): h,max , determine Δf h,max Is it less than the set threshold ε? If not, return to step 3) to continue iteration; otherwise, go to step 9);

[0044]

[0045] Where: max(·) represents the maximum value of the vector; | | represents the modulus of a complex number or the absolute value of a real number. and are the reduced-order water supply nodes for the k+1th and kth iterations respectively. potential vector; and are the reduced-order backwater nodes of the k+1th and kth iterations respectively potential vector; is the residual column vector of water flow rate at the k+1th iteration;

[0046] 10) According to the thermal node potential, thermal pipe water flow rate, thermal system Flow mechanism model calculation of thermal system Flow distribution.

[0047] Further, in step S2,

[0048] For the power system, if the unbalanced node Known, indicating that the unbalanced node power is known; at this time, the three-phase power system The flow calculation model is obtained from the power flow model and is expressed as follows:

[0049]

[0050] Where: e i and Q i are the nodes i Current and reactive power, Flow is also known as active power; U i and U j are the voltages of nodes i and j respectively; j∈i means nodes i and j are connected; G ij and B ij are the conductance and susceptance of the line between nodes i and j respectively; θ ij is the voltage phase angle difference between nodes i and j;

[0051] The power line between nodes i and j Loss Δe e It is expressed as:

[0052]

[0053] Where: and are the voltage phasors at both ends of the line respectively; | | indicates the modulus of a complex number or the absolute value of a real number;

[0054] Use one of the Newton method, PQ decomposition method or forward-backward substitution method to solve equation (9).

[0055] Further, in step S3,

[0056] natural gas Flow equals gas node The product of potential and gas flow rate, natural gas node The potential is obtained from the natural gas parameters and the ambient temperature. The potential is considered as a constant, and the natural gas flow rate satisfies Kirchhoff's first law at the node. The flow at the node also satisfies the generalized Kirchhoff's first law. The flow equation says:

[0057] e g,N =A g e g (27)

[0058] Where: A g is the node-branch association matrix of the natural gas system; e g For natural gas pipelines Flow column vector; e g,N Natural gas source vector;

[0059] For low-pressure, medium-pressure and high-pressure natural gas systems, the Lacey equation, Polyflo equation and Panhandle "A" equation are used to express the relationship between node pressure and airflow rate. Substituting the flow-airflow equation into the three types of pressure-airflow equations, we can get the relationship between the node pressure and the pipeline pressure at different pressure levels. Flow relationship of air pressure - Flow equation:

[0060]

[0061] Where pr1 and pr2 are the air pressures at both ends of the pipeline; D g is the diameter of the natural gas pipeline; L g is the length of the natural gas pipeline; E is the efficiency factor; the three formulas from top to bottom in formula (12) are respectively called: Lacey Flow equations, Polyflo-like Flow Equations and Class Panhandle "A" Flow equations;

[0062] Furthermore, the Newton node method is used to solve the pressure- Stream computing model, the specific solution process is as follows:

[0063] 301) Obtain natural gas system topology, pipeline parameters, and pressure parameters of balanced nodes; based on unbalanced nodes , forming a reduced-order natural gas source load Column vector e' g,N , e'g,N By e g,N The unbalanced node elements in the

[0064] 302) Initialize node air pressure;

[0065] 303) According to the node gas pressure, the natural gas pipeline is calculated by formula (12): Stream g , and then solve the reduced-order natural gas source load outside the equilibrium node e' g,N , get the source charge The residual difference between the calculated value and the actual value is:

[0066] Δf g =A g1 e g -e' g,N (29)

[0067] Where: A g1 is the reduced-order node-branch association matrix of the natural gas system; Δf g Natural gas source residual column vector;

[0068] 304) Based on the Newton node method, the Jacobian matrix J of the natural gas system is constructed g for:

[0069]

[0070]

[0071] Where: is the transpose of the reduced-order node-branch association matrix; e i for e g The i-th element of; low-pressure natural gas system m is 2, ΔΠ i is the difference in gas pressure between the nodes at both ends of the i-th pipeline. For the medium-pressure system, m is 1.848, and for the high-pressure system, m is 1.854. i is the difference between the squares of the gas pressures at the two ends of the i-th pipeline, and D is the diagonal natural gas parameter correction matrix;

[0072] 305) Update the node pressure from the node Jacobian matrix:

[0073]

[0074] Where: (k) represents the kth iteration; δΠ is the column vector of node pressure correction; Π for low-pressure natural gas system is the column vector of node pressure, and Π for medium-pressure and high-pressure system is the column vector of node pressure square;

[0075] 306) Determine Δf gWhether the absolute values ​​of the elements in are all less than the set threshold ε, if the condition is met, proceed to step 307), otherwise return to step 303) to continue iteration;

[0076] 307) Export natural gas system pipeline Flow distribution.

[0077] On the other hand, the present invention also provides a method based on an unbalanced node Integrated energy system A stream direct computing device, comprising:

[0078] Thermal System Hydraulic-Thermal- The flow direct calculation unit uses hydraulic models and thermodynamics- Flow model alternating iterative algorithm to solve the thermal system hydraulic-thermal- The flow direct calculation model obtains the thermal system Flow distribution;

[0079] Power system three phase The flow direct calculation unit solves the three-phase power system by using one of the algorithms: Newton method, PQ decomposition method or forward back substitution method. The flow direct calculation model is used to obtain the power system Flow distribution;

[0080] Natural gas system pressure - The flow direct calculation unit uses the Newton node method to solve the gas system pressure- The direct calculation model of the flow of natural gas system Flow distribution.

[0081] On the other hand, the present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the unbalanced node-based Integrated energy system Flow direct calculation method steps.

[0082] On the other hand, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method based on the unbalanced node Integrated energy system Flow direct calculation method steps.

[0083] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0084] 1. Compared with the medium flow and energy flow of traditional integrated energy systems, Taking into account both the "quantity" and "quality" of energy, That is effective energy, which is the part of energy that fully reflects the value. Stream computing can solve The flow distribution can then be used to obtain the effective energy distribution and loss of the comprehensive energy system, which is conducive to the coordinated analysis of the "quantity" and "quality" of the system.

[0085] 2. Known unbalanced nodes Under the condition of three-phase power flow, The relationship between flow and air pressure The relationship between flow and water flow is used to construct the power, natural gas and thermal systems respectively. Stream computing model, establish known unbalanced nodes Conditional A flow direct calculation model is proposed and a solution algorithm is proposed.

[0086] 3. The present invention has broad application prospects. The present invention comprehensively considers the "quantity" and "quality" of energy to establish a comprehensive energy system model. Integrated energy system Direct flow calculation method can solve known unbalanced nodes in actual engineering Integrated energy system under the condition of Flow distribution, such as measuring source current, air flow, water flow, etc. through the source position medium flow measurement device, measuring voltage, water supply temperature, etc. Potential Calculation Parameter Estimation Node potential, and then indirectly estimate the source load of the unbalanced node , based on unbalanced nodes Integrated energy system Direct flow calculation can solve the system in this scenario. Flow distribution.

[0087] 4. Considering With commodity attributes and on the premise of meeting energy demand, users can For the transaction object, if If the transaction volume is a constant, the source load of the unbalanced node It can also be considered as known, based on unbalanced nodes Integrated energy system Direct flow calculation can solve the system in this scenario. Flow distribution.

[0088] 5. At a known unbalanced node In this scenario, the unbalanced node Integrated energy system The direct calculation method of flow can effectively obtain the energy network in steady state. The distribution and loss of effective energy can be obtained by Flow distribution, tracking the effective energy flow trajectory, analyzing the source, network, and load The “origins and development” of. As a physical quantity reflecting the quality of energy, based on The flow calculation results can effectively analyze the overall or local energy quality characteristics of the system, and thus provide a theoretical basis for subsequent comprehensive energy system planning, operation optimization, control, trading and other technologies that consider energy quality, and realize the rational use of high-quality energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1a and Figure 1b Zero Analogy diagram of potential point and zero potential point;

[0090] Figure 2 For simple thermal system nodes and Schematic diagram of flow composition;

[0091] Figure 3 For a thermal system based on the alternating iterative method Flow solving methods;

[0092] Figure 4 For a natural gas system based on the Newton node method Flow solving methods;

[0093] Figure 5 Based on unbalanced nodes of Flowchart of the direct calculation method of the stream;

[0094] Figure 6 is a schematic diagram of a comprehensive energy system used as an example in this embodiment;

[0095] Figure 7 The structure of energy stations ES1 and ES2 for the example integrated energy system;

[0096] Figure 8 Node of the comprehensive energy system for the example Schematic diagram of potential distribution;

[0097] Fig. 9 Comprehensive energy system for the example Changes in losses;

[0098] Fig.10 For the example of comprehensive energy system energy efficiency, Efficiency changes. DETAILED DESCRIPTION

[0099] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0100] The present invention provides a method based on an unbalanced node Integrated energy system Stream direct calculation method, including:

[0101] S1, known unbalanced nodes Under the condition of thermal system Flow mechanism model, establish the thermal system hydraulic-thermal- Direct flow calculation model, using hydraulic model and thermal- Alternating Iterative Algorithm for Flow Model to Solve the Hydraulic-Thermal- The flow direct calculation model obtains the thermal system Flow distribution;

[0102] S2, known unbalanced nodes Under the condition of Flow calculation model, establish the power system three-phase The flow direct calculation model is proposed, and the solution algorithm is proposed; one of the algorithms, the Newton method, the PQ decomposition method or the forward back substitution method, is used to solve the three-phase power system The flow direct calculation model is used to obtain the power system Flow distribution;

[0103] S3, known unbalanced nodes Under the conditions of natural gas system Flow calculation model, establish the natural gas system pressure- The flow direct calculation model is proposed, and the solution algorithm is proposed; the Newton node method is used to solve the gas pressure- The direct calculation model of the flow of natural gas system Flow distribution;

[0104] S4. The hub model updates and iterates the connections between the thermal system, power system and natural gas system in the integrated energy system. The energy consumption or supply of each energy system is updated during the iteration process. , solving the thermal system, power system and natural gas system until the operating conditions of the current integrated energy system are met; obtain the entire integrated energy system Flow Potential distribution.

[0105] Specifically, 1. Thermal system Flow Mechanism Model

[0106] Thermal systems generally use water as a medium to supply heat energy from the source end to the load end. Thermal systems mainly include water supply networks and return water networks. Common topological forms are radial and ring. Based on the study of thermal flow in thermal systems, this example focuses on the heat flow carried by water. , regardless of pressure etc. that are not consumed by the load .

[0107] (1) Water transfers heat Calculation method

[0108] Under steady-state conditions, the heat ΔQ absorbed by a certain mass of water when its temperature changes from T2 to T1 (released when T1 changes to T2) is h (W) can be expressed as:

[0109] ΔQ h =c p m h (T1-T2) (33)

[0110] Where: c p is the specific heat capacity of water (J / (kg·K)); m h is the mass flow rate of water (kg / s).

[0111] From formula (17), we can see that the heat absorbed when the water temperature changes from T2 to T1 (released when T1 changes to T2) is Δe h (W) can be expressed as:

[0112]

[0113] Where: ∫ represents integration; T a is the ambient temperature; δQ h and δT are the differentials of heat and temperature change in the temperature change, respectively; T is the water temperature during the change process.

[0114] First, analyze the heat transferred by water in the thermal system components The main components involved include: water supply pipe, return pipe, heat source and load. Consider a thermal pipe with water temperatures at both ends of the pipe being T1 and T2 respectively. The heat released by the water in the pipe to the outside world is It can be expressed by formula (18). The heat absorbed and released by water at the heat source and load , which can also be obtained from formula (18):

[0115]

[0116] Where: Δe h,S The amount of heat absorbed by the water in the network at the heat source , that is, heat source ; Δe h,L The heat released by the water at the load to the user through the heat exchanger , that is, heat load ; T s,S and T r,S are the supply and return water temperatures of the heat source (K); T s,L and T o,L are the water supply and outlet temperatures of the load (K); m h,S and m h,L are the water mass flow rates through the heat source and load, respectively.

[0117] (2) Thermal system The concept of potential

[0118] From equations (18) and (19), we can see that the heat transferred by the element is It is related to the ambient temperature, the temperature at both ends of the element, the water flow rate, and the specific heat capacity. Flow theory describes heat in thermodynamic systems The present invention defines variables related to the component water temperature and the ambient temperature

[0119]

[0120] Where: Describes the difference between the water temperature of the component and the ambient temperature. In electrical theory, the electric field potential difference is the work done by a unit positive charge moving from one point to another. By analogy with formula (2), we can know that the water temperature at both ends of the component corresponds to and The difference can be expressed as the heat transferred by unit mass water from temperature T1 to T2 :

[0121]

[0122] Analogous to the concept of potential difference, the above formula corresponds to different water temperatures. difference Defined as Potential difference.

[0123] Furthermore, considering that the definition of potential in circuit theory is closely related to potential difference, such as Figure 1a As shown, the node potential is the potential difference (voltage) between the point and the reference point. The reference point can be any point in the circuit, and the earth is generally selected as the zero potential point. In thermal science, the environmental state is often regarded as The baseline state, such as Figure 1b As shown, based on Flow theory, analogous to the zero potential point in the circuit, select the corresponding ambient temperature As the reference point, define the zero point of the thermal system The temperature of a node in a thermal system corresponds to the ambient temperature. The potential difference is defined as the Potential T (J / kg), as shown in the following formula:

[0124]

[0125] Where: The ambient temperature corresponds to T = T a Substituting into equation (22), we can get the corresponding ambient temperature Potential Ta is zero, that is, the reference point of the thermal system The potential is zero.

[0126] (3) Thermal system Definition of Stream

[0127] According to the second law of thermodynamics, the energy of the environment is , so at ambient temperature water carries is zero. Define the heat flow at a certain location in a thermal system. =The heat absorbed by water when it is heated from ambient temperature to the current temperature T , this part As water flows in the network, this invention refers to it as the flow.

[0128] The power flow of the power system is often described by the power at the beginning and end of the line. Flow theory, this embodiment uses the first end of the element Stream Description Element Stream, based on the headend Flow and heat transferred by the element Available end Flow. Figure 2 As shown, the head and the end of the elements in the thermal system are connected through various nodes, which mainly include: heat source water supply node, heat source return water node, load water supply node, load outlet node, load return water node, connection node of water supply network and return water network, etc.

[0129] element Flow and connected nodes Potential related, near the node Flow is the surrounding directly connected elements From formula (18), we can see that the water near the node is controlled by the ambient temperature T a When heated to temperature T, the amount of heat absorbed Δe h,Ta It can be expressed as:

[0130] Δe h,Ta =(TT a lnT-T a +T a oeLh a )c p m h (39)

[0131] based on Flow theory, near nodes of thermal systems The flow can be calculated by formula (23), combined with formula (22) The potential definition is: when the node water temperature is T, the node near Flows can be represented as nodes The product of potential and water mass flow rate:

[0132] e h =Δe h,Ta =p T m h (40)

[0133] From equations (18), (21) and (22), we can see that the heat transferred by the element is It can be expressed as the water temperature at both ends of the element The product of the potential difference and the mass flow rate of water flowing through the element is:

[0134]

[0135] According to Ohm's law, the power consumed by the resistor in the circuit is equal to the product of the potential difference and the current. From formula (25), we can know that: The potential is similar to the electric potential in the circuit. The heat transferred by the components in the thermal system equal The product of potential difference and water mass flow rate. Analogous to the physical meaning of electric potential, Potential is the heat transferred by unit mass water from ambient temperature to actual temperature , The potential determines the amount of water of the same mass carried at different locations in the system. The value size can be regarded as A measure of flow. The potential difference means the amount of heat transferred by a unit mass of water during temperature change. size.

[0136] Figure 2 It is a typical double-layer topological thermal system with a symmetrical water supply and return network. The load and heat source can be regarded as elements between the water supply and return network. Flow distribution consists of three parts:

[0137] Damage, including supply and return pipes Loss and Load damage;

[0138] Heat Source and load ;

[0139] element Flow, including supply and return pipes Flow, flow into heat source Flow, inflow load Inflow and outflow loads flow.

[0140] Based on the above The flow distribution can obtain the flow of the effective energy of the entire thermal system. The following is a detailed analysis:

[0141] 1) Water supply and return pipes damage

[0142] There is heat loss in the water supply and return pipes, accompanied by loss, it can be seen from formula (25) that the pipeline The loss can be expressed as the two end nodes Potential difference and pipe water flow rate m h The product of:

[0143]

[0144] Where: Δe h,sl and Δe h,rl Water supply and return pipes Loss; p s1 and p s2 They are the nodes at both ends of the water supply pipeline. potential; p r1 and p r2 They are the nodes at both ends of the return pipe. Momentum.

[0145] 2) Heat source and load

[0146] The amount of heat absorbed by water at the heat source (Heat Source ) and the heat released at the load (load ) and pipeline The heat loss is similar to that of the heat source. Δe h,SCan be represented as a water supply node Potential s and return water node Potential r The product of the difference and the heat source water flow rate, load Δe h,L Can be represented as a water supply node Potential and exit nodes Potential o The product of the difference and the load water flow rate:

[0147]

[0148] Heat Source ,load With pipeline There are differences in the loss of pipeline The heat source is not used. To provide heat to the system ,load Heat consumed by the load , can be regarded as available Rather than damage.

[0149] 3) Load damage

[0150] like Figure 2 As shown in the figure, when the return water node is a mixed node, the water flowing out of the load mixes with the water in the return water network, and the water temperature changes. There are differences in potential, which leads to Changes in this section is not used by the load, so the present invention regards it as a kind of Loss, from formula (25), we can know that this part Heat loss Loss Δe h,Ll It can be expressed as:

[0151] Δe h,Ll =(p o -p r )m h,L (44)

[0152] 4) Components flow

[0153] like Figure 2 As shown, it is assumed that the supply and return water networks are completely symmetrical, and the water loss in the pipes is ignored. To ensure the continuity of the water flow, the water flow rates in the corresponding supply and return water pipes are the same but in opposite directions. The flow is in the same direction as the water flow, corresponding to the The flow direction is opposite. From formula (24), we can see that the supply and return pipes A flow can be represented as a head node The product of potential and water flow rate:

[0154]

[0155] Where: e h,s and e h,r Water supply and return pipes Flow, p s and p r The first end nodes of the water supply pipeline Potential and return pipe head end node Momentum.

[0156] Similarly, if Figure 2 As shown, the inflow load Stream h,sL Can be regarded as load Flow, which can be represented as a load water supply node The product of the potential and the load water flow rate; the flow into the heat source Stream h,rS Can be considered as heat source Flow, which can be represented as a heat source return node The product of potential and heat source water flow rate will not be repeated.

[0157] If the load The loss is regarded as the heat released by the components between the outlet node and the return node. , outflow load Stream h,oL This component can be considered Flow, flowing out from the load outlet node, can be represented as the load outlet node The product of the potential and the load water flow rate. h,oL Part of the load Loss Δe h,Ll , and the other part is connected to the return water network Streams meet.

[0158] From the above analysis, it can be seen that the thermal system Flow Distribution and Nodes potential, water flow rate, The potential can be obtained from the temperature calculation. Therefore, the water flow rate and temperature are obtained based on the measurement or multi-energy flow calculation, and then the thermal system is calculated by equations (26)-(29). Flow distribution.

[0159] 2. Power system Flow Mechanism Model

[0160] In energy quality analysis, electrical energy can be completely converted into work or other forms of energy, which is high-quality energy and can be regarded as Therefore, the active power flow of the power system is The active power loss is Three-phase symmetrical AC power system (hereinafter referred to as power system) flow and harmony The loss can be expressed as:

[0161] e e =P e (46)

[0162] Δe e =ΔP e (47)

[0163] Where: e e and P e The power lines flowing through Current and active power (kW); Δe e and ΔP e For lines loss and active power loss.

[0164] Based on measurement or power flow calculation, the active power flow distribution and active power loss of the power system can be obtained, and then calculated by equations (30) and (31): Flow distribution.

[0165] The present invention regards the current as the medium flow rate of the power system. flow and harmony The loss can be expressed as:

[0166]

[0167]

[0168] Where: Re[·] represents the real part of a complex number; is the line voltage phasor at the head end of the power line (kV∠rad); is the conjugate of the line current phasor flowing through the line (A∠rad); and are the line voltage phasors at both ends of the line respectively.

[0169] From equations (32) and (33), we can see that the line The flow can be represented by the line voltage and line current, The line loss can be expressed by the line voltage difference and line current. flow theory, the present invention regards the node voltage as the power system potential, reflecting the unit current carried flow. The potential difference reflects the unit current generated on the line damage.

[0170] 3. Natural gas system Flow Mechanism Model

[0171] The natural gas system supplies gas to users through the pipeline network. The current natural gas energy measurement standards "Technical Requirements for Natural Gas Metering System: GB / T18603-2014" and "Determination of Natural Gas Energy: GB / T 22723-2008" propose that the energy of a certain amount of natural gas can be expressed as the product of the amount of gas and the calorific value, and the calorific value is the calorific value. This energy measurement formula is widely used in engineering practice. In the IES multi-energy flow research, natural gas is regarded as a medium for transmitting energy. The above energy measurement formula is used to measure the energy of natural gas, and the conversion between the gas power and the airflow rate included in the load and multi-energy coupling links is realized. Therefore, thermal power is used to measure the natural gas energy in steady state, that is, gas power, and pressure energy and other energies that are not consumed by the multi-energy coupling links and loads are not taken into account. Gas power can be calculated from the airflow rate and the total calorific value:

[0172]

[0173] Where: φ g and m g are the natural gas power (kW) and flow rate (m 3 / h; G is the total calorific value of natural gas (MJ / m 3 ).

[0174] The energy of natural gas is measured in terms of thermal power, the fuel consumed by gas loads It is equivalent to the heat generated by heating the ambient temperature to the theoretical combustion temperature during the combustion of natural gas. Natural gas Stream g (kW) can be expressed as the energy quality coefficient λ of natural gas g The product of gas power:

[0175]

[0176] Where: T b is the theoretical combustion temperature of natural gas (K).

[0177] based on Flow theory, when the ambient temperature, natural gas theoretical combustion temperature and total calorific value are constant, natural gas The gas flow is determined by the gas flow rate. If the loss of pipeline natural gas and the change of gas quality are ignored, the natural gas system can be regarded as non- Lossless network, no Loss refers to the heat consumed by load and multi-energy coupling links. There is no loss in the transmission process. The pipeline pressure drop under steady-state conditions determines the distribution of airflow in the system, which in turn determines The distribution of gas flow Although the pressure effect is not considered in the flow analysis, However, it is necessary to consider its impact on The influence of flow distribution. From formula (35), we can see that The flow can be regarded as the natural gas flow rate m g With constant p g The product of:

[0178]

[0179] From equations (35) and (36), we can see that the constant p g Can be regarded as a natural gas system potential, which means the unit airflow rate , unit is kWh / m 3 . Gas pipeline The flow can be expressed as the natural gas flow rate and The product of the potential, both ends of the gas pipeline The potential difference is zero, The loss can be considered as the two ends The product of the potential difference and the gas flow rate, therefore, ignoring the loss of pipeline natural gas and the change in gas quality, the natural gas system meets the requirement of no The gas flow rate is obtained based on measurement or multi-energy flow calculation, and then the gas flow rate of the natural gas system is calculated by formula (35). Flow distribution.

[0180] In this embodiment, the pipeline refers to a pipe, and the loop is a closed loop composed of multiple pipes.

[0181] 4. Thermal system hydraulic-thermal- Stream Direct Computation Model

[0182] In the study of multi-energy flow of integrated energy system (IES), heat load is a known quantity, and both energy flow and load are related to temperature and water flow rate. The thermal flow can be solved by alternating iteration of hydraulic and thermal models. Similarly, as shown in equations (26)-(29), Flow, load Both potential and water flow rate, and The potential is also related to temperature, so the hydraulic model, water flow rate-temperature and Solving the Thermal System Using Alternative Iteration Method of Flow Relation Model Flow distribution.

[0183] (1) Hydraulic model

[0184] Water as a transfer agent in thermal systems The medium that affects flow, Loss and Load The important parameters of water flow distribution are obtained in The water flow at the thermal node satisfies the generalized Kirchhoff's first law, and the water pressure in the water supply network and return network loop satisfies the generalized Kirchhoff's second law, which is described by the flow continuity equation and the water pressure drop equation:

[0185]

[0186] Where: A h is the node-branch association matrix of the water supply network, with dimension n h,n ×n h,p , n h,n is the number of water supply nodes, n h,p is the number of thermal pipes; m h is the water flow rate column vector of the water supply pipe, with dimension n h,p ; B h is the loop-branch association matrix, with dimension n h,l ×n h,p , n h,l is the number of loops; h f n h,p dimensional water pressure loss column vector; Equation (37) can be solved by the Newton method. h,N n h,n dimensional source-water flow column vector.

[0187] (2) Heat - Flow model (water flow rate-temperature and Stream Relational Model)

[0188] The thermal model includes: thermal source load power equation, pipeline water temperature drop equation and node water temperature mixing equation to describe the temperature changes in thermal pipelines and nodes; if the non-equilibrium node It is known that the water supply temperature vector T in the thermal source load power equation s The product of the specific heat capacity of water c p and the outlet temperature vector T o The difference between the product of the specific heat capacity of water and the water supply node Potential vector p s and exit node Potential vector p o The difference between the thermal power vector Δφ and the thermal power vector Δφ is replaced by the thermal power vector Vector Δe h,N , that is, replaced by the thermal source load Flow equation, and then get the thermal- Flow model, as shown in formula (38);

[0189]

[0190] Where: T start and T end are the water temperatures at both ends of the pipe; t λ is the thermal conductivity; L h is the length of the thermal pipeline; T in and T out are the water temperatures at the inflow node and outflow node respectively; m in and m out are the water flow rates into and out of the node respectively; Δe h,N Heat source Column vector, heat source outlet and return node The potential is equal, the heat source absorbs and the load releases heat The above heat source can be Flow equation representation.

[0191] Known unbalanced nodes , combined with the hydraulic model shown in equation (37) and the thermal model shown in equation (38) Flow model, the thermal system can be solved by alternating iteration method potential and water flow rate, and then use equations (26)-(29) to solve Flow distribution. The calculation process is as follows Figure 3 As shown, the specific solution process is as follows:

[0192] 1) Obtain thermal system topology, pipeline parameters, balanced nodes, and unbalanced nodes , heat source water supply node temperature, load outlet node temperature and other parameters.

[0193] 2) Initialize parameters such as load water supply temperature, heat source and load return water temperature, and pipeline water flow rate.

[0194] 3) By unbalanced nodes Constructing a reduced-order thermal source Column vector Δe' h,N , Δe' h,N The dimension is n h,n -1, by Δe h,N The unbalanced node elements are composed of

[0195] 4) Calculate the reduced-order nodes based on the water temperature and ambient temperature of the thermal nodes Potential column vector p' s 、p' o and p' r, the reduced order represents the column vector composed of node parameters outside the equilibrium node. According to the thermal source load in formula (23), Flow equation, calculate the reduced-order thermal source water flow rate column vector m' h,N :

[0196] m' h,N =diag(p' s -p' o ) -1 Δe' h,N (55)

[0197] Where: p' s and p' o They are p s and p o The column vector of unbalanced node elements, with dimension n h,n -1; p' r Non-balanced node return water node The vector of potential is n h,n -1; m' h,N By m h,N The unbalanced node elements are composed of n h,n -1.

[0198] 5) Construct n from formula (37) h,p Dimensional water flow rate residual column vector:

[0199]

[0200] Where: A' h,1 is the reduced-order node-branch association matrix of the water supply network, with dimension (n h,n -1)×n h,p ; K h n h,p dimensional column vector of pipe resistance coefficients.

[0201] 6) Build n h,p ×n h,p Jacobian matrix J of the thermodynamic system h :

[0202]

[0203] 7) Update the water flow rate of the water supply pipe by the Jacobian matrix:

[0204]

[0205] Where: is a column vector of water flow rate corrections in the water supply pipeline, with a dimension of n h,p Where: is a column vector of water flow rate corrections in the water supply pipeline, with a dimension of n h,p ; and are the water flow rate vectors of the water supply pipeline at the kth and k+1th iterations respectively; is the invertible matrix of the Jacobian matrix at the kth iteration; is the residual column vector of water flow rate at the kth iteration.

[0206] 8) The equation group shown in equation (28) is constructed from equation (23) to solve the reduced-order node temperature column vector T of the thermal system: s '、T o ' and T r ':

[0207]

[0208] Where: C s , C r 、b s 、b r are the water supply network characteristic matrix, the return water network characteristic matrix, the water supply parameter characteristic vector, and the return water parameter characteristic vector; and are the characteristic column vector of supply water temperature and the characteristic column vector of return water temperature respectively;

[0209] 9) Calculate the maximum value of the iterative residual Δf by formula (29): h,max , determine Δf h,max Is it less than the set threshold ε? If not, return to step 3) to continue iteration; otherwise, go to step 10).

[0210]

[0211] Where: max(·) represents the maximum value of the vector; | | represents the modulus of a complex number or the absolute value of a real number. and are the reduced-order water supply nodes for the k+1th and kth iterations respectively. potential vector; and are the reduced-order backwater nodes of the k+1th and kth iterations respectively potential vector; is the residual column vector of water flow rate at the k+1th iteration.

[0212] 10) According to the node potential, pipe water flow rate, and the thermal system shown in equations (26)-(29) Flow mechanism model, calculation of thermal system Flow distribution.

[0213] 5. Three-phase power system Stream Direct Computation Model

[0214] From equations (30)-(31), we can see that if the unbalanced node Known, indicating that the unbalanced node power is known. At this time, the three-phase power system The flow calculation model can be obtained from the power flow model, which is expressed as follows:

[0215]

[0216] Where: e i and Q i are the nodes i Current (active power) and reactive power; U i and U j are the voltages of nodes i and j respectively; j∈i means nodes i and j are connected; G ij and B ij are the conductance and susceptance of the line between nodes i and j respectively; θ ij is the voltage phase difference between nodes i and j.

[0217] The power line between nodes i and j Loss Δe e It can be expressed as:

[0218]

[0219] Where: and are the voltage phasors at both ends of the line respectively; | | indicates the modulus of a complex number or the absolute value of a real number.

[0220] Formula (45) can be solved by using the Newton method, PQ decomposition method, forward back substitution method and other algorithms.

[0221] 6. Natural gas system pressure - Stream Direct Computation Model

[0222] From formula (35) and (36), we can see that natural gas Flow equals gas node The product of potential and gas flow rate. From equation (36), we can know that the natural gas node The potential is obtained from the natural gas parameters and the ambient temperature and can be regarded as a constant. The natural gas flow rate satisfies the generalized Kirchhoff's first law at the node. The flow at the node also satisfies the generalized Kirchhoff's first law, and the natural gas node can be used The flow equation says:

[0223] e g,N =A g e g (63)

[0224] Where: A g is the node-branch association matrix of the natural gas system, with dimension n g,n ×n g,p ;e g n g,p Maintenance pipeline Flow column vector; e g,N n g,n Natural gas source load Vector, n g,p is the number of natural gas pipelines, n g,n is the number of gas nodes.

[0225] The Lacey equation, Polyflo equation and Panhandle "A" equation can be used to represent the relationship between node pressure and airflow rate for low-pressure, medium-pressure and high-pressure natural gas systems respectively. Substituting equations (35) and (36) into the three types of pressure-airflow equations, we can obtain the relationship between node pressure and pipeline pressure at different pressure levels. Flow relationship of air pressure - Flow equation:

[0226]

[0227] Where pr1 and pr2 are the air pressures at both ends of the pipeline; D g is the pipe diameter; L g is the pipe length; E is the efficiency factor. The above three equations can be called: Lacey Flow equations, Polyflo-like Flow Equations and Class Panhandle "A" Flow equation.

[0228] Analogous to the solution of natural gas flow, the pressure- The flow calculation model can be solved using the Newton node method. The flow chart is as follows: Figure 4 As shown, the specific solution process is as follows:

[0229] 1) Obtain natural gas system topology, pipeline parameters, balance node pressure and other parameters; based on non-balanced nodes , forming a reduced-order natural gas source load Column vector e' g,N , e' g,N By e g,N The unbalanced node elements in the g,n -1.

[0230] 2) Initialize node air pressure.

[0231] 3) According to the node gas pressure, the natural gas pipeline is calculated by formula (32): Flow vector e g , and then solve the reduced-order natural gas source load outside the equilibrium node Column vector e' g,N , get the natural gas source load The residual difference between the calculated value and the actual value is:

[0232] Δf g =A g1 e g -e' g,N (65)

[0233] Where: A g1 is the reduced node-branch association matrix with dimension (n g,n -1)×n g,p ; Δf g For the source Residual column vector, dimension n g,n -1.

[0234] 4) Based on the Newton node method, construct the node Jacobian matrix J g for:

[0235]

[0236]

[0237] Where: is the transpose of the reduced-order node-branch association matrix; e i for e g The i-th element of; low-pressure natural gas system m is 2, ΔΠ i is the difference in gas pressure between the nodes at both ends of the i-th pipeline. For the medium-pressure system, m is 1.848, and for the high-pressure system, m is 1.854. i is the difference between the squares of the pressures at the nodes at both ends of the i-th pipeline, D is n g,p ×n g,p dimensional diagonal matrix; J g The dimension of (n g,n -1)×(n g,n -1).

[0238] 5) Update the node pressure from the node Jacobian matrix:

[0239]

[0240] Where: (k) represents the kth iteration; δΠ is the column vector of the node pressure correction, with dimension n g,n -1; low-pressure natural gas system Π is (n g,n-1)-dimensional column vector of node pressure. The medium and high pressure systems Π are column vectors composed of squares of node pressure, with a dimension of n g,n -1.

[0241] 6) Determine Δf g Are the absolute values ​​of the elements in all smaller than the set threshold ε? If so, proceed to step 7), otherwise return to step 3) to continue iterating.

[0242] 7) Export natural gas system pipeline Flow distribution.

[0243] 6. Hub Model

[0244] From equations (25), (36) and (30), we can get the energy station power λ e , Natural gas g , Thermal port λ h The energy quality coefficients can be expressed as follows:

[0245]

[0246] Where: e EH,e 、e EH,g and e EH,h are the electricity, gas and heat power at the energy station port respectively; P EH,e , P EH,g and P EH,h are the electricity, gas and heat power of the energy station port respectively; T1 and T2 are the water temperatures at both ends of the hot water that transfers heat, and p1 and p2 are the corresponding Momentum.

[0247] based on The hub model builds the energy station model:

[0248] e out =C λ e in (70)

[0249] Where: e in and e out Input and output ports respectively The flow column vector has dimensions n ES,in and n ES,out , where n ES,in and n ES,out are the number of energy forms of the input and output ports, C λ for The coupling matrix is ​​expressed as:

[0250]

[0251] Where: Cλ The dimension is n ES,out ×n ES,in ; in and λ out are the energy quality coefficient matrices of the input and output ports, respectively, and are the diagonal matrices of the energy quality coefficients of each energy of the input and output ports, where λ in The dimension is n ES,in ×n ES,in ,λ out The dimension is n ES,out ×n ES,out .

[0252] 7. Based on unbalanced nodes of Stream Direct Computation Method

[0253] Considering the regional scope of the integrated energy system, the power system adopts the forward-backward method to solve the system The natural gas system is solved by the Newton method. flow; thermal system using hydraulic model and thermal- Alternating Iterative Algorithm for Solving Flow Model The three are based on Hub model coupling, the coupling method depends on the system's operating mode, device type, etc. Overall system Flow solving model such as Figure 5 As shown, the specific process is as follows:

[0254] 1) Obtaining the load of the integrated energy system (IES) , determine the system's operating mode, grid topology, energy stations and other information;

[0255] 2) Calculate the electricity, natural gas and thermal systems separately Flow distribution;

[0256] 3) By Hub Model Update Iteration Energy Station Interaction information, return to 2) calculation Flow distribution until the current operating conditions are met;

[0257] 4) Get the IES as a whole Flow Potential distribution.

[0258] The following example implements the above-mentioned unbalanced node Integrated energy system The specific application of the stream direct calculation method is described below:

[0259] Select Figure 6The example shown is an integrated energy system analysis. In the figure, E1-E6 represents power nodes, G1-G7 represents natural gas nodes, and H1-H8 represents heat sources or heat loads. The medium-pressure natural gas system is based on the 5-node natural gas system parameter modification. The gas source pressure is 5 bar, the theoretical combustion temperature of natural gas is 1973℃, and the calorific value is 45.75MJ / m 3 The thermal system is modified based on the 8-node thermal system parameters. The system is heated by dual heat sources. The water supply temperature of the two heat sources is 100°C and the load outlet temperature is 50°C. The power system is modified based on the IEEE33-node distribution network parameters. The source voltage is 12.66kV. The power, natural gas and thermal systems are coupled through energy stations ES1 and ES2. The structures of ES1 and ES2 and the connection methods with each energy system are as follows: Figure 7 As shown in the figure, ES1 includes the combined heat and power unit CHP and the gas boiler GB. The CHP gas-to-electricity conversion efficiency Gas-heat conversion efficiency 0.3 and 0.4 respectively, GB gas-heat conversion efficiency is 0.85, and the CHP natural gas distribution coefficient v I ES1 is operated in a heat-to-electricity mode, connected to the power system node E6, the natural gas system load node G6, and the thermal system heat source node H1; ES2 includes electric boilers EB and GB, and the GB gas-heat conversion efficiency 0.85, EB electric-thermal conversion efficiency is 0.95, the heat production of EB and GB in ES2 is the same, and ES2 is connected to the power system load node E5, the natural gas system load node G7, and the thermal system heat source node H2.

[0260] According to the example non-equilibrium node shown in Table 1 Parameters, based on the present invention Direct calculation model of the flow, calculate and analyze the IES under typical operation scenarios Flow distribution.

[0261] Table 1 Non-equilibrium nodes of the example Parameters (kW)

[0262]

[0263] Assume that the electricity, gas and heat loads in the integrated energy system Known, and H2 supply is 129.309kW, based on Direct flow calculation model, solving examples The flow distribution results are shown in Table 2. ,load ,load The damage results are shown in Table 3. Loss, total supply at source , total load The results are shown in Table 4. The potential distribution results are as follows Figure 8 As shown in Table 4, the total supply of the source end of the example system is The load is 8145.406kW. The total power of the system is 6060.154kW. The data shows that the power supplied by the source end of the example Equal to the load consumption With all The sum of the losses verifies the example system balance.

[0264] In the direct flow calculation model, The hub builds an energy station model and obtains the current operating status of ES1 and ES2. The hub model is:

[0265]

[0266]

[0267] Where: e g,in1 Fuel for ES1 input port ;e e,out1 and e h,out1 The power of ES1 output port and heat ;e e,in2 and e g,in2 The power of ES2 input port and fuel ;e h,out2 Heat output port for ES2 .

[0268] The energy station is modeled based on energy flow analysis, and the energy station model is established using the energy hub. The energy hub model that represents the current operating status of ES1 and ES2 is as follows:

[0269]

[0270]

[0271] Where: P g,in1 P is the gas power of ES1 input port; e,out1 and P h,out1 are the electrical power and thermal power of the ES1 output port respectively; P e,in2 and Pg,in2 are the electric power and gas power of ES2 input port respectively; P h,out2 This is the thermal power of the ES2 output port.

[0272] From equations (56)-(59), we can see that the energy hub model describes the energy relationship between the input and output ports under steady-state conditions. The hub describes the effective relationship between the input and output ports. Based on the heat of the ES1 output port Calculates fuel at input port and the power of the output port . Given the heat generation ratio of GB and EB, according to the heat output of ES2 Can calculate the electrical energy of the input port and fuel , which precisely reflects the characteristics of the operation mode of determining electricity by heat.

[0273] The analytical formula (56) (57) describes The coupling matrix and the energy coupling matrix described by equations (58) and (59) have the same dimensions and positions of non-zero elements, but the values ​​of some elements are essentially different. Some elements in the coupling matrix correspond to the conversion relationship from high-quality energy to low-quality energy, and their values ​​are lower than the corresponding elements in the energy coupling matrix. For example, ES2 converts electricity and natural gas into low-quality heat. The value shown in formula (57) Each element of the coupling matrix is ​​smaller than the corresponding element of the energy coupling matrix shown in equation (59); similarly, Some elements in the coupling matrix correspond to the conversion relationship from low-quality energy to high-quality energy, and their values ​​are higher than the corresponding elements in the energy coupling matrix. For example, ES1 involves the conversion of natural gas to high-quality electricity, corresponding to the equation (56) The element 0.2139 in the first row and second column of the coupling matrix is ​​higher than the corresponding element 0.15 in equation (58); When the elements in the coupling matrix do not involve changes in energy quality, their values ​​are equal to the corresponding elements in the energy coupling matrix. There are similarities and differences between the coupling matrix and the energy coupling matrix. The coupling matrix takes into account both the "quantity" and "quality" of energy.

[0274] Energy efficiency, Efficiency is an important indicator for energy and energy quality evaluation, reflecting the utilization of energy and effective energy respectively. The present invention defines the energy efficiency of an energy station as the ratio of the output port power to the input port power of the energy station. Efficiency for energy station output port With input port The energy efficiency of ES1 and ES2 is calculated according to equations (56)-(59). The efficiency of ES1 is 77.50%, the efficiency of ES2 is 89.72%, and the efficiency of ES1 is 77.50%. The efficiency is 37.84%, ES2 The efficiency is 19.68%. The results show that the energy efficiency of ES1 is lower than that of ES2, but The efficiency is higher than that of ES2, which means that although the EB used in ES2 has higher energy efficiency, it converts most of the high-quality electrical energy into low-quality heat, which greatly reduces Efficiency, the CHP used in ES1 produces high-quality electricity, which is conducive to suppressing the degradation of energy quality. It can be seen that in addition to considering factors such as economy and energy efficiency, research on energy station equipment configuration, operation optimization, and control should also fully consider the impact of energy quality.

[0275] Table 2 Example Flow distribution calculation results (kW)

[0276]

[0277] Table 3 Source ,load and load Loss(kW)

[0278]

[0279] Table 4 Example system Loss, total supply at source and the total load Calculation result (kW)

[0280]

[0281] Taking into account the changes in external load demand, the heat generation of ES2 changes from 100kW to 2500kW, and the energy quality of the example system changes.

[0282] Keep v I The heat generation of EB and GB in ES2 is the same, and the relationship between the input and output power of ES1 and ES2 is not affected by the change of the heat generation of the energy station, which is expressed by equations (58) and (59). Therefore, the energy efficiency of ES1 and ES2 is constant at 77.50% and 89.72%. The change of ES2 heat generation affects the operation mode of the thermal system, so the water temperature of the return water node The potential has an impact. From formula (53), it can be seen that the energy quality coefficient of the heat output of the energy station changes. The In addition, changes in the operation mode of the thermal system will affect the flow rate of the medium and the nodes in the network. The distribution of potential, thereby changing the system Based on the above analysis, the change of heat generation of energy stations in the system will affect the local energy quality of each energy system.

[0283] The following quantitative analysis is carried out, such as Fig. 9 As shown in the figure, as the heat generation of ES2 increases, the energy station ES2 in the example The loss gradually increases, and the ES1 The loss gradually decreases, and the total energy station The loss accounts for a large proportion, and the The loss may show an opposite trend. The loss shows an increasing trend.

[0284] The present invention defines system energy efficiency as the ratio of total load power to total power supplied by the source. Efficiency equals total load Total energy supplied by the source The ratio of Fig.10 It can be seen that the system energy efficiency shows an increasing trend, The change trend of efficiency is opposite to that of energy efficiency, which decreases gradually. In ES2, EB has higher energy efficiency, which reduces system energy loss when heat generation increases. Under the condition of constant load, system energy efficiency increases. The example topology is relatively simple, and the load The change is small, as the system The increase of loss, the system The efficiency gradually decreases.

[0285] From the above analysis, it can be seen that the operation mode and network topology of energy stations in the actual integrated energy system (IES) are more complex. If the changes in energy stations, network structures and operation modes are comprehensively considered, the energy quality characteristics of the system will be affected by more factors, and the relationship between energy networks, energy stations, the whole and the local, and energy and energy quality will be more complex. Based on the #imgpt641# flow analysis and calculation model, the system #imgpt642# flow distribution can be obtained, and then nonlinear optimization technology can be used to find optimization solutions according to demand, improve the overall or certain link energy quality, and reduce high-quality energy losses. At the same time, it is also necessary to realize that energy and energy quality indicators may be mutually exclusive. IES planning, operation optimization, control and other technologies should comprehensively consider the differences in energy "quantity" and "quality" of the entire system, between energy stations, and between energy networks, and consider the coordinated optimization of energy and quality.

[0286] Unless otherwise specified, the models of the components in the embodiments of the present invention are not limited, and any device that can perform the above functions may be used.

[0287] Those skilled in the art will appreciate that the accompanying drawing is only a schematic diagram of a preferred embodiment, and the serial numbers of the embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0288] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

[0289] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solution of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, a person of ordinary skill in the art can also make many forms of specific changes under the guidance of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A method based on unbalanced nodes Integrated energy system The flow direct calculation method is characterized by: include: S1, known unbalanced nodes Under the condition of thermal system Flow mechanism model, establish the thermal system hydraulic-thermal- Direct flow calculation model, using hydraulic model and thermal- Flow model alternating iterative algorithm to solve the thermal system hydraulic-thermal- The flow direct calculation model obtains the thermal system Flow distribution; thermal system Flow distribution consists of three parts: Damage, including supply and return pipes Loss and Load damage; Heat Source and load ; element Flow, including supply and return pipes Flow, flow into heat source Flow, inflow load Inflow and outflow loads flow; Thermal System Hydraulic-Thermal- The hydraulic model and thermal model are used in the direct calculation model of flow Solving the Thermodynamic System Using Alternating Iteration Method of Flow Model Flow distribution: (101) Construction of hydraulic model: In the hydraulic model, the water flow at the thermal nodes satisfies the generalized Kirchhoff's first law. The thermal nodes include the supply nodes, return nodes, and outlet nodes. The water pressure in the supply network and return network loops satisfies the generalized Kirchhoff's second law. (102) Building Heat - Flow model, that is, water flow rate-temperature and Relational model of streams: The thermal model of the thermal system includes: thermal source load power equation, pipeline water temperature drop equation and node water temperature mixed equation to describe the temperature changes at the thermal pipeline and nodes; if the non-equilibrium node It is known that the water supply temperature vector T in the thermal source load power equation s The product of the specific heat capacity of water c p and the outlet temperature vector T o The difference between the product of the specific heat capacity of water and the water supply node Potential vector p s and exit node Potential vector p o The difference between the thermal power vector Δφ and the thermal power vector Δφ is replaced by the thermal power vector Vector Δe h,N , that is, replaced by the thermal source load Flow equation, and then get the thermal- Flow model; Known unbalanced nodes , using the alternating iterative method to solve the thermal system potential and water flow rate, and then based on the thermal system Flow mechanism model solution Flow distribution; S2, known unbalanced nodes Under the condition of Flow calculation model, establish the power system three-phase Direct calculation model of flow; use one of the algorithms such as Newton method, PQ decomposition method or forward back substitution method to solve the three-phase power system The flow direct calculation model is used to obtain the power system Flow distribution; S3, known unbalanced nodes Under the conditions of natural gas system Flow calculation model, establish the natural gas system pressure- Direct calculation model of flow; Newton node method is used to solve the gas pressure of natural gas system- The direct calculation model of the flow of natural gas system Flow distribution; S4. The hub model updates and iterates the connections between the thermal system, power system and natural gas system in the integrated energy system. The energy consumption or supply of each energy system is updated during the iteration process. , solving the thermal system, power system and natural gas system until the operating conditions of the current integrated energy system are met; obtain the entire integrated energy system Flow Potential distribution.

2. According to claim 1, a method based on unbalanced nodes Integrated energy system The flow direct calculation method is characterized by: (101) The hydraulic model is described by the flow continuity equation and the water pressure drop equation: Where: A h is the node-branch association matrix of the water supply network; m h is the water flow rate column vector of the water supply pipeline; B h is the loop-branch association matrix of the water supply network; h f is the water pressure loss column vector of the water supply network; Formula (1) is solved by the Newton method; m h,N is the heat source water flow column vector; (102) Building Heat - Flow model, that is, water flow rate-temperature and The relational model of streams, where: heat- The flow model is shown in formula (2); Where: T start and T end are the water temperatures at both ends of the pipe; T a is the ambient temperature; t λ is the thermal conductivity; L h is the length of the thermal pipeline; T in and T out are the water temperatures at the inflow node and outflow node respectively; m in and m out are the water flow rates into and out of the node respectively; Δe h,N Heat source Column vector, heat source outlet and return node The potential is equal, the heat absorbed by the heat source and the heat released by the load Both can be charged by the above heat source Flow equation representation.

3. According to claim 2, a method based on unbalanced nodes Integrated energy system The flow direct calculation method is characterized by: Known unbalanced nodes , combined with the hydraulic model shown in formula (1) and the thermal model shown in formula (2) Flow model, solving Flow distribution; the specific solution process is as follows: 1) Obtain thermal system topology, pipeline parameters, balanced nodes, and unbalanced nodes , heat source water supply node temperature, load outlet node temperature parameters; 2) Initialize the load water supply temperature, heat source and load return water temperature, and pipeline water flow rate parameters; 3) By unbalanced nodes Constructing a reduced-order thermal source Column vector Δe' h,N , by Δe h,N The unbalanced node elements are composed of; 4) Calculate the reduced-order thermal nodes based on the thermal node water temperature and ambient temperature Potential column vector p' s 、p' o and p' r , the reduced order represents the column vector composed of node parameters outside the equilibrium node. According to the thermal source load in formula (2), Flow equation, calculate the reduced-order thermal source water flow rate column vector m' h,N : m' h,N diag(p' s -p' o ) -1 Δe' h,N (3) Where: p' s and p' o They are p s and p o The column vector of unbalanced node elements; p' r Non-balanced node return node The vector formed by the potential; m' h,N By m h,N The unbalanced node elements are composed of; 5) Construct the water flow rate residual column vector from formula (1): Where: A' h,1 is the reduced-order node-branch association matrix of the water supply network; K h is the column vector of pipeline resistance coefficient; 6) Construct the Jacobian matrix J of the thermal system h : 7) Update the water flow rate of the water supply pipe by the Jacobian matrix: Where: is a column vector consisting of water flow rate correction values ​​in the water supply pipeline; and are the water flow rate vectors of the water supply pipeline at the kth and k+1th iterations respectively; is the invertible matrix of the Jacobian matrix at the kth iteration; is the residual column vector of water flow rate at the kth iteration; 8) Based on equation (2), the equation group (7) is constructed to solve the reduced-order node temperature column vector T of the thermal system: s '、T o ' and T r ': Where: C s , C r 、b s 、b r are the water supply network characteristic matrix, the return water network characteristic matrix, the water supply parameter characteristic vector, and the return water parameter characteristic vector; and are the characteristic column vector of supply water temperature and the characteristic column vector of return water temperature respectively; 9) Calculate the maximum value of the iterative residual Δf by formula (8): h,max , determine Δf h,max Is it less than the set threshold ε? If not, return to step 3) to continue iteration; otherwise, go to step 9); Where: max(·) represents the maximum value of a vector; || represents the modulus of a complex number or the absolute value of a real number. and are the reduced-order water supply nodes for the k+1th and kth iterations respectively. potential vector; and are the reduced-order backwater nodes of the k+1th and kth iterations respectively potential vector; is the residual column vector of water flow rate at the k+1th iteration; 10) According to the thermal node potential, thermal pipe water flow rate, thermal system Flow mechanism model calculation of thermal system Flow distribution.

4. A method based on unbalanced nodes according to claim 1 Integrated energy system The flow direct calculation method is characterized by: In step S2, For the power system, if the unbalanced node Known, indicating that the unbalanced node power is known; at this time, the three-phase power system The flow calculation model is obtained from the power flow model and is expressed as follows: Where: e i and Q i are the nodes i Current and reactive power, Flow is also known as active power; U i and U j are the voltages of nodes i and j respectively; j∈i means nodes i and j are connected; G ij and B ij are the conductance and susceptance of the line between nodes i and j respectively; θ ij is the voltage phase angle difference between nodes i and j; The power line between nodes i and j Loss Δe e It is expressed as: Where: and are the voltage phasors at both ends of the line respectively; || means taking the modulus of a complex number or the absolute value of a real number; Use one of the Newton method, PQ decomposition method or forward-backward substitution method to solve equation (9).

5. A method based on unbalanced nodes according to claim 1 Integrated energy system The flow direct calculation method is characterized by: In step S3, natural gas Stream equals gas node The product of potential and gas flow rate, natural gas node The potential is obtained from the natural gas parameters and the ambient temperature. The potential is considered as a constant, and the natural gas flow rate satisfies Kirchhoff's first law at the node. The flow at the node also satisfies the generalized Kirchhoff's first law. The flow equation says: And g,N =A g And g (11) Where: A g is the node-branch association matrix of the natural gas system; e g For natural gas pipelines Flow column vector; e g,N Natural gas source vector; For low-pressure, medium-pressure and high-pressure natural gas systems, the Lacey equation, Polyflo equation and Panhandle "A" equation are used to express the relationship between node pressure and airflow rate. Substituting the flow-airflow equation into the three types of pressure-airflow equations, we can get the relationship between the node pressure and the pipeline pressure at different pressure levels. Flow relationship of air pressure - Flow equation: Where pr1 and pr2 are the air pressures at both ends of the pipeline; D g is the diameter of the natural gas pipeline; L g is the length of the natural gas pipeline; E is the efficiency factor; the three formulas from top to bottom in formula (12) are respectively called: Lacey Flow equations, Polyflo-like Flow Equations and Class Panhandle "A" Flow equation.

6. A method based on unbalanced nodes according to claim 5. Integrated energy system The flow direct calculation method is characterized by: The Newton node method is used to solve the pressure- Stream computing model, the specific solution process is as follows: 301) Obtain natural gas system topology, pipeline parameters, and pressure parameters of balanced nodes; based on unbalanced nodes , forming a reduced-order natural gas source load Column vector e' g,N , e' g,N By e g,N The unbalanced node elements in the 302) Initialize node air pressure; 303) According to the node gas pressure, the natural gas pipeline is calculated by formula (12): Stream g , and then solve the reduced-order natural gas source load outside the equilibrium node e' g,N , get the source charge The residual difference between the calculated value and the actual value is: Δf g =A g1 e g -e' g,N (13) Where: A g1 is the reduced-order node-branch association matrix of the natural gas system; Δf g Natural gas source residual column vector; 304) Based on the Newton node method, the Jacobian matrix J of the natural gas system is constructed g for: Where: is the transpose of the reduced-order node-branch association matrix; e i for e g The i-th element of; low-pressure natural gas system m is 2, ΔΠ i is the difference in gas pressure between the nodes at both ends of the i-th pipeline. For the medium-pressure system, m is 1.848, and for the high-pressure system, m is 1.

854. i is the difference between the squares of the gas pressures at the two ends of the i-th pipeline, and D is the diagonal natural gas parameter correction matrix; 305) Update the node pressure from the node Jacobian matrix: Where: (k) represents the kth iteration; δΠ is the column vector of node pressure correction; Π for low-pressure natural gas system is the column vector of node pressure, and Π for medium-pressure and high-pressure system is the column vector of node pressure square; 306) Determine Δf g Whether the absolute values ​​of the elements in are all less than the set threshold ε, if the condition is met, proceed to step 307), otherwise return to step 303) to continue iteration; 307) Export natural gas system pipeline Flow distribution.

7. A method based on unbalanced nodes Integrated energy system A stream direct computing device, characterized in that include: Thermal System Hydraulic-Thermal- The flow direct calculation unit uses hydraulic models and thermodynamics- Flow model alternating iterative algorithm to solve the thermal system hydraulic-thermal- The flow direct calculation model obtains the thermal system Flow distribution; Thermal system Flow distribution consists of three parts: Damage, including supply and return pipes Loss and Load damage; Heat Source and load ; element Flow, including supply and return pipes Flow, flow into heat source Flow, inflow load Inflow and outflow loads flow; Thermal System Hydraulic-Thermal- The hydraulic model and thermal model are used in the direct calculation model of flow Solving the Thermodynamic System Using Alternating Iteration Method of Flow Model Flow distribution: (101) Hydraulic model The water flow at the thermal nodes satisfies the generalized Kirchhoff's first law. The thermal nodes include the supply nodes, return nodes, and outlet nodes. The water pressure in the supply network and return network loops satisfies the generalized Kirchhoff's second law. (102) Heat - Flow model, that is, water flow rate-temperature and Relational Model of Streams The thermal model of the thermal system includes: thermal source load power equation, pipeline water temperature drop equation and node water temperature mixed equation to describe the temperature changes at the thermal pipeline and nodes; If the unbalanced node It is known that the water supply temperature vector T in the thermal source load power equation s The product of the specific heat capacity of water c p and the outlet temperature vector T o The difference between the product of the specific heat capacity of water and the water supply node Potential vector p s and exit node Potential vector p o The difference between the thermal power vector Δφ and the thermal power vector Δφ is replaced by the thermal power vector Vector Δe h,N , that is, replaced by the thermal source load Flow equation, and then get the thermal- Flow model; Known unbalanced nodes , using the alternating iterative method to solve the thermal system potential and water flow rate, and then based on the thermal system Flow mechanism model solution Flow distribution; Power system three phase The flow direct calculation unit solves the three-phase power system by using one of the algorithms: Newton method, PQ decomposition method or forward back substitution method. The flow direct calculation model is used to obtain the power system Flow distribution; Natural gas system pressure - The flow direct calculation unit uses the Newton node method to solve the gas system pressure- The direct calculation model of the flow of natural gas system Flow distribution.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the method based on unbalanced nodes according to any one of claims 1 to 6 is implemented. Integrated energy system Flow direct calculation method steps.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the unbalanced node based method described in any one of claims 1 to 6 is implemented. Integrated energy system Flow direct calculation method steps.

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