CN114629124A - Comprehensive energy system load flow calculation method based on subareas - Google Patents
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Abstract
The invention discloses a partition-based comprehensive energy system power flow calculation method, which adopts a Czochralski method to calculate the radial block power flows of an electric power system, a thermodynamic system and a natural gas system, calculates the annular block power flow of the natural gas system according to a finite element method, combines the complementary advantages of the two calculation methods, effectively solves the nonlinear and non-convex problems of the natural gas power flow, and realizes the efficient solution of the comprehensive energy system power flow with a large-scale network structure.
Description
Technical Field
The invention relates to the technical field of power systems, in particular to a comprehensive energy system load flow calculation method based on partitions.
Background
With the advance of carbon neutralization strategy, in order to develop new energy patterns of fossil energy, renewable energy balanced development and complementary utilization, the comprehensive energy system is also more and more widely applied. Load flow calculation is an important basis for analysis and optimization work of the comprehensive energy system. The concept of load flow calculation is derived from the load flow calculation of a power system, and is gradually introduced into a natural gas system and a thermal system subsequently. However, when the conventional power flow calculation method is applied to the framework of the comprehensive energy system, the defect of poor convergence exists, the complex nonlinear and non-convex solving problems of the multi-energy power flow are difficult to solve, and a solving method with universal applicability is lacked in the face of the comprehensive energy system with a large-scale complex network structure.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a comprehensive energy system load flow calculation method based on partitions, which not only improves the calculation convergence, but also is suitable for a large-scale comprehensive energy system with a complex network structure.
In order to solve the technical problem, the invention provides a comprehensive energy system load flow calculation method based on partitions, which comprises the following steps:
(1) the natural gas system of the hybrid topology is divided into a plurality of blocks only containing radiation type topology and ring type topology based on the topology type, and each block only contains a single type topology structure; the topological scale and complexity in a single block are greatly simplified compared with the original system;
(2) determining connection nodes among the blocks according to the partitioning result, and forming an independent equivalent block of the connection nodes by aggregating the associated blocks to form an equivalent topology of the connection nodes, so that the load flow of the connection nodes can be independently calculated;
(3) setting an upper node of each block as a virtual balance node by taking the natural gas flow direction as the forward direction according to the distribution positions of the connecting nodes and each block, wherein each block is independent during load flow calculation; the calculation convergence of other blocks is prevented from being influenced due to the fact that the calculation of a single block is not converged, and the calculation convergence is further enhanced;
(4) establishing an electricity-gas-heat comprehensive energy system model, and establishing a steady-state power flow model based on an energy conservation principle and kirchhoff's law;
(5) establishing a Newton-Raphson method and finite element node method calculation model suitable for load flow calculation of the comprehensive energy system, calculating electric and thermal current and radiation type block load flow of the natural gas system according to the Newton method, and calculating the ring type block load flow of the natural gas system according to the finite element method;
(6) according to the load flow calculation result of each block, if a block with the load flow incapable of converging still exists, performing secondary partition on the block, if a plurality of compressors with consistent outlet pressure exist, constructing an equal air pressure point to realize equivalent topology reconstruction, splitting the equal air pressure point into a plurality of blocks only containing single type topology, and repeating the step (5) to calculate the load flow of the newly added block;
(7) and after the load flow calculation of each block is converged, restoring the topology according to the original topological structure, and summarizing the calculation result to obtain the load flow distribution of the whole network.
Preferably, in the step (4), the step of establishing an electricity-gas-heat comprehensive energy system model, and the step of establishing a steady-state power flow model based on the energy conservation principle and kirchhoff's law specifically comprises the following steps:
in the formula: x is a radical of a fluorine atomeThe method comprises the steps of providing a variable vector of a power system, wherein the variable vector comprises a voltage amplitude, a voltage phase, active power and reactive power; x is the number ofgThe method comprises the steps of obtaining a natural gas system variable vector comprising node pressure and node injection flow; x is the number ofhThe variable vector of the thermodynamic system comprises node injection power, branch flow, heat supply temperature and heat return temperature.
Preferably, in the step (5), the calculation sequence of the load flow of each block of the natural gas system is as follows: firstly, calculating the load flow of each connecting node according to the equivalent block of the connecting node established in the step (2); sequentially calculating the load flow of each block according to the natural gas flow direction; and an appropriate solving method is selected according to the block topology type, so that the advantage complementation of the algorithm can be realized, and the problems of nonlinearity and non-convexity of the flow of the natural gas system with a large-scale network structure and a complex structure are effectively solved.
Preferably, in the step (5), a newton-raphson method and a finite element node method calculation model suitable for load flow calculation of the integrated energy system are established, wherein the newton-raphson method calculation model is as follows:
F(x)＝Δf＝0 (2)
in the formula, Δ f is a deviation amount of each subsystem, such as active deviation and reactive deviation of an electric power system, node thermal power deviation of a thermodynamic system, pressure drop deviation of a heating network loop, heating temperature deviation and regenerative temperature deviation, and node flow deviation of a natural gas system;
in the formula, x represents the state quantity of each subsystem;
jacobian matrix J is represented as
The finite element node method is used for solving the natural gas system power flow of the ring topology, and is represented by a kirchhoff first law, the algebraic sum of the flow of any node is zero, the load of any node is equal to the sum of the flows of branches flowing into and out of the node, and the load is represented by a matrix form as follows:
AQ＝L (5)
in the formula: a is a node branch incidence matrix of the natural gas network; q is the natural gas flow of each pipeline; l is the flow rate of each node;
from kirchhoff's second law, the pressure drop along any one closed loop is zero, and the start and end points of one closed loop are the same point, so the pressure drop along the entire loop is zero, represented by a matrix:
BΔΠ＝0 (6)
in the formula: b is a natural gas network loop incidence matrix; delta pi is a pressure drop vector of each pipeline, and the element of the vector is obtained by the pressure difference of the starting point and the ending point of the pipeline;
transposing the incidence matrix A, and multiplying the transposed matrix A by the column vector of the relative pressure of the nodes, namely, the column vector is equal to the pressure drop of each pipeline, namely:
ΔΠ＝ATΠ (7)
the relationship between the pipe section flow and the pressure drop in the gas pipe network calculation formula is as follows:
ΔΠ＝CQ2 (8)
in the formula: Δ Π is the pressure drop across the pipe section; c is a characteristic parameter of the gas transmission pipeline; q is the pipeline flow; are all arranged in a matrix form,
if C' is CQ, then:
ΔΠ＝C′Q (9)
let G be 1/C', then:
Q＝GΔΠ (10)
the linear equation for the unknown quantity Π is obtained as:
AGATΠ＝L (11)
let Y equal to AGATThe above formula is written as:
YΠ＝L (12)
the relation between the pressure drop of the pipeline and the flow is linearized, Y is called an iterative matrix, G is called an admittance matrix, and the above formula is an iterative mathematical model of a finite element node method.
The invention has the beneficial effects that: according to the method, the radiation-type block tidal current of the electric power system, the thermodynamic system and the natural gas system is calculated by adopting a Czochralski method, the ring-type block tidal current of the natural gas system is calculated according to a finite element method, the advantages of the two calculation methods are combined for complementation, the problems of nonlinearity and non-convexity of the natural gas tidal current are effectively solved, and the high-efficiency solution of the tidal current of the comprehensive energy system with a large-scale network structure and a complex structure is realized.
Drawings
FIG. 1 is a schematic view of the topological partitioning of the present invention.
FIG. 2 is a schematic diagram of the present invention for realizing equivalent topology reconstruction according to an equal air pressure node.
FIG. 3 is a schematic flow chart of the method of the present invention.
Fig. 4 is a structural view of an electric-gas-heat integrated energy system used in the present invention.
FIG. 5 is a block diagram of a partitioned natural gas system according to the present invention.
Fig. 6 is a block partition-based connection node topology reconfiguration diagram according to the present invention.
FIG. 7 is an equivalent topological reconstruction diagram of the annular block for establishing the equal pressure points according to the embodiment of the present invention.
Detailed Description
A comprehensive energy system load flow calculation method based on subareas comprises the following steps:
step 4, establishing an electricity-gas-heat comprehensive energy system model, and establishing a steady-state power flow model based on an energy conservation principle and kirchhoff's law;
and 5, establishing a Newton-Raphson method and a finite element node method calculation model suitable for load flow calculation of the comprehensive energy system, calculating electric and thermal load flow and radiation type block load flow of the natural gas system according to the Newton method, and calculating the annular block load flow of the natural gas system according to the finite element method. The calculation sequence of the load flow of each block of the natural gas system is as follows, firstly, the load flow of each connecting node is calculated according to the equivalent block of the connecting node established in the step 2; and sequentially calculating the load flow of each block according to the natural gas flowing direction. An appropriate solving method is selected according to the block topology type, so that the advantage complementation of the algorithm can be realized, and the problems of nonlinearity and non-convexity of the flow of the natural gas system with a large-scale network structure and a complex structure are effectively solved;
and 7, after the load flow calculation of each block is converged, restoring the topology according to the original topological structure, and summarizing the calculation result to obtain the load flow distribution of the whole network.
In the step 1, the natural gas system with the hybrid topology is divided into a plurality of blocks only containing the radiation type topology and the ring type topology based on the topology type, each block only contains a single type topology structure, and the topology scale and the complexity in a single block are greatly simplified compared with the original system. As shown in Mode a in fig. 1, only a single type of topology exists in a single block, and the number of internal nodes and pipes and the complexity of the topology are greatly reduced compared with those of the original system.
In the step 2, the connection nodes between the blocks are determined according to the partitioning result. The definition of the connection node is not strictly limited, and for the blocks which can be obviously divided according to the topology type, the nodes which play the connection role among the blocks can be all determined as the connection nodes. The equivalent topology of the connection nodes is formed by aggregating the associated blocks to form an independent equivalent block of the connection nodes, so that the load flow of the connection nodes can be independently calculated. As shown in Mode B in fig. 1, the blocks after the initial aggregation may be partitioned and aggregated again according to the partitioning policy in step 1, so as to equivalently reconstruct the simplified independent blocks connected to the node, as shown in Mode C in fig. 1. The topological scale and the complexity of the system are greatly reduced compared with the original system, and the load flow of the equivalent block of the connecting node can be independently calculated.
In the step 3, the natural gas flow direction is set as the forward direction according to the distribution positions of the connection nodes and the blocks, and the upper node of each block is set as the virtual balance node, as shown in Mode a in fig. 1, the virtual balance nodes of the blocks R1 and L1 are both the upper connection nodes thereof. Each block is independent when the load flow calculation is carried out, the calculation convergence of other blocks is prevented from being influenced due to the fact that calculation of a single block is not converged, and the calculation convergence is further enhanced.
In the step 4, an electricity-gas-heat comprehensive energy system model is established, a steady-state power flow model is established based on an energy conservation principle and kirchhoff's law, and a comprehensive energy system containing electricity, gas and heat is established and modeled.
In the formula: x is the number ofeThe variable vector of the power system generally comprises a voltage amplitude value, a voltage phase, active power, reactive power and the like; x is the number ofgThe method comprises the following steps of (1) providing a natural gas system variable vector, wherein the variable vector generally comprises node pressure, node injection flow and the like; x is the number ofhThe variable vector of the thermodynamic system generally comprises node injection power, branch flow, heating temperature, regenerative temperature and the like.
The energy flow calculation of the power system is based on the active power and reactive power balance of the nodes, and an equation is constructed by taking the voltage amplitude and the voltage phase as state variables.
In the formula: pG,iAnd PL,iRespectively the active power generation power and the load power of the node i; qG,iAnd QL,iRespectively the reactive power generation power and the load power of the node i; u shapeiAnd UjThe voltage amplitudes of nodes i and j, respectively; thetaijIs the voltage phase difference between nodes i and j; gijAnd BijRespectively, the real part and the imaginary part of the ith row and the jth column element in the node admittance matrix.
Energy flow calculation of the natural gas system is based on node flow balance, node pressure is used as a state variable, and a Weymouth equation is constructed.
In the formula: piiAnd pijPressures at nodes i and j, respectively; qijNatural gas flow for branch i-j; cgIs the characteristic parameter of the gas transmission pipeline.
If there is a compressor between nodes i and k, the following equations must be supplemented.
πk＝γikπi (a4)
In the formula: gamma rayikA compressor transformation ratio; hikConsuming power for the compressor; tau isikThe flow rate of the natural gas of the branch i-k; etaikTo compressor efficiency; alpha is a parameter related to the temperature of the compressor and the adiabatic index.
The natural gas consumption amount of the compressor is as follows:
in the formula: f. ofikThe air consumption of the compressor is measured; alpha is alphaik，βik，χikThe compressor dissipation factor.
The thermodynamic system energy state variables are selected as branch (mass) flow, heating temperature and regenerative temperature, and the energy flow equation is composed of 2 parts of a hydraulic equation and a thermodynamic equation.
1) And (4) a hydraulic model.
The flow of hot water in the network should satisfy the basic network law: the flow of each pipeline at each node should satisfy a flow continuity equation, that is, the injection flow at the node is equal to the outflow flow; in a closed circuit consisting of pipes, the sum of the head losses of the water flowing in the pipes is 0.
Cpmq(Ts-To)-φ＝0 (a7)
CsTs-bs＝0
CrTr-br＝0 (a8)
BhKm|m|＝0 (a9)
In the formula: cpThe specific heat capacity of the working medium; m is a unit ofqFlow vectors are flowed out for each node;
a thermal load vector for each node; csAnd CrBranch-flow incidence matrixes of the heat supply network and the heat return network respectively; bpAnd bpColumn vectors related to the heating temperature and the regenerative temperature respectively; bhIs a loop-branch incidence matrix; k is a pipeline resistance coefficient vector; and m is branch quality flow vector.
2) And (4) a thermal model.
For each thermal load node, the heating temperature TsIndicating the temperature before hot water is injected into the load node, the output temperature ToIndicating the temperature of hot water flowing out of the load node, the regenerative temperature TrRepresenting the temperature of the hot water exiting the load node after mixing with the water of the other pipes at the pipe node. The thermal model is as follows:
(∑msTs)-moTo＝0
(∑mrTr)+moTo＝0 (a11)
in the formula: t isstart，Tend，TaRespectively a starting point temperature, an end point temperature and an external environment temperature vector of the pipeline; lambda is the heat transfer coefficient of the pipe; l is the length vector of the pipeline; m isoA flow vector injected to the load for the hybrid node; m issInjecting flow vectors for mixed nodes in a heat supply pipe network; m isrThe flow vectors injected into the hybrid node for the heat recovery pipe network.
The coupling equipment comprises an electric boiler and a gas boiler, the electric boiler takes electric energy as energy to convert the electric energy into heat energy and output heat carrying media, and the modeling method of the electric boiler comprises the following steps:
QEB＝REBηEB (a12)
in the formula: qEBThe output heat value of the electric boiler is obtained; rEBIs rated for the boilerThe amount of power supply; etaEBIs the thermal efficiency of the boiler. The gas boiler takes natural gas as fuel and provides heat energy for users, and the modeling method of the gas boiler comprises the following steps:
QGB＝RGBηGB (a13)
in the formula: qGBIs the output heat value of the gas boiler; rGBThe rated power supply of the boiler is provided; etaGBIs the thermal efficiency of the boiler. The amount of natural gas consumed by the gas boiler can be expressed as:
in the formula: vGBThe amount of natural gas consumed by the gas boiler; l isNGIs the low calorific value of natural gas, and the conventional value is 9.78 (kW.h)/m3。
In the step 5, a Newton-Raphson method and finite element node method calculation model suitable for load flow calculation of the comprehensive energy system is established. The calculation model of the Newton-Raphson method is as follows:
F(x)＝Δf＝0 (a15)
in the formula, Δ f is a deviation amount of each subsystem, such as an active deviation and a reactive deviation of an electric power system, a node thermal power deviation of a thermodynamic system, a heat supply network loop pressure drop deviation, a heat supply temperature deviation and a heat return temperature deviation, and a natural gas system node flow deviation.
In the formula, x represents the state quantity of each subsystem.
The Jacobian matrix J can be expressed as.
The finite element node method is used for solving the natural gas system trend of the annular topology, and the flow algebraic sum of any node is zero according to the kirchhoff first law. That is to say the load at any node is equal to the sum of the branch flows into and out of that node, expressed in matrix form.
AQ＝L (a18)
In the formula: a is a node branch incidence matrix of the natural gas network; q is the natural gas flow of each pipeline; and L is the flow rate of each node.
The pressure drop along any one closed loop is zero from kirchhoff's second law. The start and end points of a closed loop are the same point, so the pressure drop along the entire loop is zero, which can be represented by a matrix:
BΔΠ＝0 (a19)
in the formula: b is a natural gas network loop incidence matrix; and delta pi is a pressure drop vector of each pipeline, and elements of the pressure drop vector can be obtained from the pressure difference of the starting point and the ending point of the pipeline.
Transposing the incidence matrix A, and multiplying the transposed matrix A by the column vector of the relative pressure of the nodes, namely, the column vector is equal to the pressure drop of each pipeline, namely:
ΔΠ＝ATΠ (a20)
the relationship between the pipe section flow and the pressure drop in the gas pipe network calculation formula is as follows:
ΔΠ＝CQ2 (a21)
in the formula: Δ Π is the pressure drop across the pipe section; c is a characteristic parameter of the gas transmission pipeline; q is the pipeline flow; are all arranged in a matrix form;
if C' is CQ, then:
ΔΠ＝C′Q (a22)
let G be 1/C', then:
Q＝GΔΠ (a23)
the linear equation for the unknown quantity Π can be found as:
AGATΠ＝L (a24)
let Y equal to AGATThe above formula can be written as:
YΠ＝L (a25)
the relation between the pressure drop of the pipeline and the flow can be linearized, Y is called an iterative matrix, G is called an admittance matrix, and the above formula is an iterative mathematical model of a finite element node method.
According to the zoning condition, two load flow solving methods are combined for calculation, namely a Newton method is adopted to calculate the radial block load flow of the electric power system, the thermodynamic system and the natural gas system, and the annular block load flow of the natural gas system is calculated according to a finite element method. The calculation sequence of the load flow of each block of the natural gas system is as follows, firstly, the load flow of each connecting node is calculated according to the equivalent block of the connecting node established in the step 2; and sequentially calculating the load flow of each block according to the natural gas flowing direction. And an appropriate solving method is selected according to the block topology type, so that the advantage complementation of the algorithm can be realized, and the problems of nonlinearity and non-convexity of the flow of the natural gas system with a large-scale network structure and a complex structure are effectively solved.
In the step 6, according to the power flow calculation result of each block, if a block with a power flow which can not be converged still exists, the block is subjected to secondary partition, if a plurality of compressors with consistent outlet pressure exist, an equal-pressure point is constructed to realize equivalent topology reconstruction, the equivalent-pressure point is divided into a plurality of blocks only containing a single type of topology, and the step 5 is repeated to calculate the power flow of the newly added block. As shown in fig. 2, if the nodes j and m are equipped with compressors with consistent outlet pressures, i and j can be regarded as equal-pressure nodes, and the reconstructed topology is as shown in model B, where o is the equal-pressure node of i and j. It should be noted that when the equal-pressure node is constructed to realize the equivalent topology reconstruction partition, the calculation sequence of the block changes, the load flow of each block is not calculated according to the natural gas flow direction sequence, but the calculation sequence is determined according to the known load of the block. Taking the model B in FIG. 2 as an example, the air pressure of the node o is known, the node o is a virtual balance node of the block o-k-n, the air loads of the node k and the node n are known, the load flow of the block can be calculated according to a finite element node method, and the ok and on flow of the pipeline can be obtained; the virtual balance node of the block i-j-l-m is an upper node of the block i-j-l-m, the known quantity is calculated through the step 4, the natural gas outflow flow of the node j and the node m is originally unknown, the flow of the pipeline ok and the sum of the on flow and the gas loads of the node j and the node m are the natural gas outflow flow of the node j and the node m by solving the block o-k-n, and the block flow can be calculated according to a Newton method. And summarizing the calculation results to obtain the Mode A power flow distribution in the figure 2.
In the step 7, after the load flow calculation of each block is converged, the topology is restored according to the original topology structure, and the calculation results are summarized to obtain the load flow distribution of the whole network, wherein the flow chart of the whole calculation is shown in fig. 3.
The invention carries out the example test by the comprehensive energy system containing electricity, gas and heat, the structure diagram of the system is shown in figure 4, and the system has 48 power nodes, 32 natural gas nodes, 29 natural gas pipelines, 5 heat supply network nodes and 4 heat supply network pipelines. The coupling of the three subsystems is realized by an electric boiler and a gas boiler. 4 gas compressors are installed in a natural gas system, the outlet pressure of the compressors is known, and the gas source point and the outlet pressure of the compressors are both 5 bar. The partitioning method proposed herein is used to split the natural gas subsystem, as shown in fig. 5, each partition contains only a single type of topology and is independent of each other. According to the partitioning result, the connection nodes between the blocks are determined, and the equivalent topology of the connection nodes is formed by aggregating the associated blocks, so as to form the independent blocks of the connection nodes, as shown in fig. 6. Preferably, the load flow of each connection node is calculated according to the independent blocks of the connection nodes, and the upper node of each block is set as a virtual balance node, for example, the virtual balance node of the blocks 2 and 3 is G1, and the virtual balance node of the block 5 is G15. And calculating the reconstruction topology of the connection nodes and the power flow in each block according to the sequence of natural gas flowing through the blocks.
Because the annular natural gas flow has high non-convexity, when the calculation finds that the energy flow can not be solved if the block 6 is taken as an independent block, the annular pipeline is in a single connection state, the iteration matrix sparsity is high during the calculation, and the Newton method and the finite element node method can not be converged, so that the topological scale and the complexity are reduced by further carrying out partition processing on the annular pipeline. The annular block 6 is internally provided with two compressor branches with equal outlet pressure, the outlet nodes of the compressors are set as equal air pressure points, the large annular block 6 is split and reconstructed into the radial block 6, the annular block 7 is reconstructed, and as shown in fig. 7, the equivalent topology of the original block is calculated again. Wherein the pressures of G30 and G31 are known and consistent, the equal air pressure points are used as virtual balance nodes of the block 7, and the block 7 calculates the power flow according to a finite element node method; the virtual balancing node of the block 6 is G17, the air pressure of the node is known after the calculation of the block 5, the flow rates of G31 and G30 are known, and the power flow is calculated according to the Newton method by the block 6. Combining the conventional Newton-Raphson method and the finite element node method, the calculation results of the natural gas system node gas pressure are shown in the table 1, and the calculation results of the flow of each pipeline are shown in the table 2.
TABLE 1 gas pressure gauge for each node of natural gas system
TABLE 2 Natural gas system each pipeline flow meter
The traditional power flow calculation method cannot obtain the multi-energy power flow convergence solution of the embodiment, and the method provided by the invention obtains the convergence solution after 15 times of maximum iteration times. In the calculation process, the original block 6 is not converged during the primary partition calculation, but the calculation convergence of other blocks is not influenced, after the block 6 is subjected to secondary partition, the block 6 is split and reconstructed into blocks 6 and 7, and the load flow convergence solution can be obtained through calculation again. By arranging the virtual balance nodes, the blocks are mutually independent, the influence on the global convergence due to the unconvergence of individual blocks can be effectively reduced, and the abnormal blocks can be quickly positioned and processed in a targeted manner. The calculation result does not have node air pressure out-of-limit and conforms to the energy conservation principle and kirchhoff theorem. The result shows that the method provided by the invention can efficiently and accurately obtain the steady state flow of the comprehensive energy system with a large-scale network structure. Therefore, compared with the traditional Newton-Raphson method, the method has the advantage of remarkable convergence, and therefore has important significance.
Claims (4)
1. A comprehensive energy system load flow calculation method based on subareas is characterized by comprising the following steps:
(1) the natural gas system of the hybrid topology is divided into a plurality of blocks only containing radiation type topology and ring type topology based on the topology type, and each block only contains a single type topology structure;
(2) determining connection nodes among the blocks according to the partitioning result, and forming an independent equivalent block of the connection nodes by aggregating the associated blocks to form an equivalent topology of the connection nodes, so that the load flow of the connection nodes can be independently calculated;
(3) setting an upper node of each block as a virtual balance node by taking the natural gas flow direction as the forward direction according to the distribution positions of the connecting nodes and each block, wherein each block is independent during load flow calculation;
(4) establishing an electricity-gas-heat comprehensive energy system model, and establishing a steady-state power flow model based on an energy conservation principle and kirchhoff's law;
(5) establishing a Newton-Raphson method and finite element node method calculation model suitable for load flow calculation of the comprehensive energy system, calculating electric and thermal current and radiation type block load flow of the natural gas system according to the Newton method, and calculating the ring type block load flow of the natural gas system according to the finite element method;
(6) according to the load flow calculation result of each block, if a block with the load flow incapable of converging still exists, carrying out secondary partition on the block, if a plurality of compressors with consistent outlet pressure exist in the block, constructing an equal air pressure point to realize equivalent topology reconstruction, splitting the equal air pressure point into a plurality of blocks only containing single type topology, and repeating the step (5) to calculate the load flow of the newly added block;
(7) and after the load flow calculation of each block is converged, restoring the topology according to the original topological structure, and summarizing the calculation result to obtain the load flow distribution of the whole network.
2. The method for calculating the power flow of the integrated energy system based on the subareas as claimed in claim 1, wherein in the step (4), an electric-gas-heat integrated energy system model is established, and the establishment of the steady-state power flow model based on the energy conservation principle and kirchhoff's law is specifically as follows:
in the formula: x is the number ofeThe method comprises the following steps of (1) obtaining variable vectors of an electric power system, wherein the variable vectors comprise voltage amplitude, voltage phase, active power and reactive power; x is a radical of a fluorine atomgThe method comprises the steps of obtaining natural gas system variable vectors including node pressure and node injection flow; x is the number ofhThe variable vector of the thermodynamic system comprises node injection power, branch flow, heat supply temperature and heat return temperature.
3. The partition-based integrated energy system power flow calculation method according to claim 1, wherein in the step (5), the power flow of each block of the natural gas system is calculated in the following sequence: firstly, calculating the load flow of each connecting node according to the equivalent block of the connecting node established in the step (2); and sequentially calculating the load flow of each block according to the natural gas flowing direction.
4. The partition-based integrated energy system power flow calculation method according to claim 1, wherein in the step (5), newton-raphson method and finite element node method calculation models suitable for integrated energy system power flow calculation are established, wherein the newton-raphson method calculation models are:
F(x)＝Δf＝0 (2)
in the formula, Δ f is a deviation amount of each subsystem, such as active deviation and reactive deviation of an electric power system, node thermal power deviation of a thermodynamic system, pressure drop deviation of a heating network loop, heating temperature deviation and regenerative temperature deviation, and node flow deviation of a natural gas system;
in the formula, x represents the state quantity of each subsystem;
jacobian matrix J is represented as
The finite element node method is used for solving the natural gas system load flow of the ring topology, and is represented by a kirchhoff first law, the flow algebraic sum of any node is zero, the load of any node is equal to the sum of the flows flowing into and out of the branch of the node, and the sum is represented by a matrix form as follows:
AQ＝L (5)
in the formula: a is a node branch incidence matrix of the natural gas network; q is the natural gas flow of each pipeline; l is the flow rate of each node;
from kirchhoff's second law, the pressure drop along any one closed loop is zero, and the start and end points of one closed loop are the same point, so the pressure drop along the entire loop is zero, represented by a matrix:
BΔΠ＝0 (6)
in the formula: b is a natural gas network loop incidence matrix; delta pi is a pressure drop vector of each pipeline, and the element of the vector is obtained by the pressure difference of the starting point and the ending point of the pipeline;
transposing the incidence matrix A, and multiplying the transposed matrix A by the column vector of the relative pressure of the nodes, namely, the column vector is equal to the pressure drop of each pipeline, namely:
ΔΠ＝ATΠ (7)
the relationship between the pipe section flow and the pressure drop in the gas pipe network calculation formula is as follows:
ΔΠ＝CQ2 (8)
in the formula: Δ Π is the pressure drop across the pipe section; c is a characteristic parameter of the gas transmission pipeline; q is the pipeline flow; are all arranged in a matrix form,
if C' is CQ, then:
ΔΠ＝C′Q (9)
let G be 1/C', then:
Q＝GΔΠ (10)
the linear equation for the unknown quantity Π is obtained as:
AGATΠ＝L (11)
let Y equal to AGATThe above formula is written as:
YΠ＝L (12)
the relation between the pressure drop of the pipeline and the flow is linearized, Y is called an iterative matrix, G is called an admittance matrix, and the above formula is an iterative mathematical model of a finite element node method.
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