A power transmission and distribution collaborative power flow calculation method and system

Abstract

The application discloses a kind of transmission and distribution collaborative power flow calculation method and system, the method includes: distribution network inside circulation step, first boundary voltage of boundary node is input to the double-port network model of distribution network, and repeatedly carry out forward-backward sweep operation, obtain boundary injection power;Transmission network inside circulation step, boundary injection power is input to the power flow mapping model in transmission network, obtain and record the first boundary voltage of boundary node updated;Iteration acceleration step, based on the first boundary voltage recorded, combined with steven acceleration algorithm, obtain second boundary voltage;And second boundary voltage is as first boundary voltage;Iteration stop step, repeatedly execute distribution network inside circulation step, transmission network inside circulation step and iteration acceleration step, until second boundary voltage meets first convergence condition, output the power flow calculation result of transmission network and distribution network.The application can effectively solve the convergence problem of existing power flow calculation model, and improve convergence speed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system, and particularly relates to a transmission and distribution collaborative power flow calculation method and system. BACKGROUND

[0002] In a power system with low penetration of distributed energy, a traditional transmission and distribution collaborative equivalent model is usually used to simplify power flow calculation to improve calculation efficiency. In this method, the distribution network is equivalent to a load when calculating the power flow of the transmission network, and the transmission network is equivalent to a power source when calculating the power flow of the distribution network. This equivalent processing method helps to reduce the size of the calculation model. However, as the number of distributed power sources connected to the distribution network increases, the response of the distributed power sources to the state of the transmission network becomes more complex, and the initiative of the distribution network is also continuously enhanced, which leads to new challenges in convergence and calculation efficiency of the traditional transmission and distribution collaborative equivalent model. Therefore, how to effectively establish a power flow calculation model of the transmission network and the distribution network has become a problem to be solved. SUMMARY

[0003] The purpose of the embodiments of the present application is to provide a transmission and distribution collaborative power flow calculation method and system, which respectively establishes a power flow calculation model for the transmission network and the distribution network, exchanges information at the boundary node, and combines the Stephenson acceleration algorithm to accelerate the iteration process, effectively solving the convergence problem of the existing power flow calculation model and improving the convergence speed.

[0004] The first aspect of the present application provides a transmission and distribution collaborative power flow calculation method, comprising:

[0005] A boundary voltage setting step: setting a first boundary voltage of a boundary node;

[0006] A distribution network internal circulation step: inputting the first boundary voltage into a two-port network model of the distribution network, and repeatedly performing a forward-backward substitution operation between the boundary node and the terminal node of the distribution network to obtain boundary injection power and voltage and current of each node in the distribution network; wherein the two-port network model is used to represent the voltage relationship and current relationship between any node and another node;

[0007] A transmission network internal circulation step: inputting the boundary injection power into a power flow mapping model of the transmission network to perform power flow calculation of the transmission network, and obtaining and recording an updated first boundary voltage of the boundary node;

[0008] An iteration acceleration step: based on the recorded first boundary voltage, combining the Stephenson acceleration algorithm to obtain a second boundary voltage; and taking the second boundary voltage as the first boundary voltage;

[0009] The iteration stopping step: repeatedly performing the power distribution network cycle step, the power transmission network cycle step and the iteration acceleration step until the second boundary voltage meets a first convergence condition, and outputting a power flow calculation result of the power transmission network and the power distribution network.

[0010] Optionally, the two-port network model is specifically as follows:

[0011]

[0012] wherein, V gabc is a three-phase-to-ground voltage of a node; I abc is a three-phase current passing through the node; n and m respectively represent a node n and a node m in the power distribution network; A, B, C and D are all generalized matrices of a transmission line between the node n and the node m, and are used to represent transmission characteristics of the transmission line.

[0013] Optionally, a calculation formula between the voltage and the current of each node in the power distribution network is as follows:

[0014]

[0015] wherein, I n is a current of the node n; S n is a complex power of the node n; V n is a voltage of the node n; and * represents taking a complex conjugate.

[0016] Optionally, the complex power of each node in the power distribution network is determined by measurement information.

[0017] Optionally, the repeatedly performing the forward-backward sweep operation between the boundary node and the terminal node of the power distribution network to obtain the boundary injection power and the voltage and the current of each node in the power distribution network comprises:

[0018] In the process of performing the power distribution network cycle step for the kth time, the i th forward-backward sweep operation is performed between the boundary node and the terminal node of the power distribution network by the two-port network model to obtain a corresponding third boundary voltage; wherein, k≥1; i≥1;

[0019] When the third boundary voltage meets a second convergence condition, the forward-backward sweep operation is stopped to obtain the boundary injection power and the voltage and the current of each node in the power distribution network.

[0020] Optionally, the power flow mapping model of the power transmission network is specifically as follows:

[0021] g T (S B )=U B ;

[0022] wherein S B is the boundary injection power; U B is the updated first boundary voltage of the boundary node; g T is a power flow function of the power grid, used to represent a power flow calculation process between a root node and the boundary node of the power grid.

[0023] Optionally, the inputting of the boundary injection power into the power flow mapping model of the power grid, the power flow calculation of the power grid, the obtaining and recording of the updated first boundary voltage of the boundary node, comprises:

[0024] In the process of the kth execution of the power grid inner loop step, when the power flow calculation of the power grid is completed and a single-phase voltage is provided for the boundary node, the updated first boundary voltage of the boundary node is calculated and recorded according to the following formula:

[0025]

[0026] wherein, is the updated first boundary voltage of the boundary node, including voltage components of phases a, b and c; and is the voltage amplitude and voltage phase corresponding to phase a in the first boundary voltage; and is the voltage amplitude and voltage phase corresponding to phase b in the first boundary voltage; and is the voltage amplitude and voltage phase corresponding to phase c in the first boundary voltage.

[0027] Optionally, the inputting of the boundary injection power into the power flow mapping model of the power grid, the power flow calculation of the power grid, the obtaining and recording of the updated first boundary voltage of the boundary node, further comprises:

[0028] In the process of the kth execution of the power grid inner loop step, when the boundary injection power is input into the power flow mapping model of the power grid and the power flow mapping model is a single-phase model, the input power of the power flow mapping model is calculated according to the following formula:

[0029]

[0030] wherein, is the single-phase apparent power input into the power flow mapping model, used to represent the single-phase apparent power injected into the power grid by the boundary node; is the single-phase active power input into the power flow mapping model; is the single-phase reactive power input into the power flow mapping model; and The active power corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network; and It is the reactive power corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network.

[0031] Optionally, the second boundary voltage is calculated by the following formula:

[0032]

[0033] in, is the second boundary voltage; is the first boundary voltage recorded for the dth time.

[0034] A second embodiment of the present invention provides a transmission and distribution coordinated power flow calculation system, including:

[0035] A boundary voltage setting module, used for setting a first boundary voltage of a boundary node;

[0036] a distribution network internal circulation module, configured to input the first boundary voltage into a two-port network model of the distribution network, and repeatedly perform forward and backward substitution operations between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; wherein the two-port network model is used to characterize the voltage relationship and current relationship between any node and another node;

[0037] a power transmission network internal circulation module, configured to input the boundary injection power into a power flow mapping model of the power transmission network, perform power flow calculation of the power transmission network, and obtain and record the updated first boundary voltage of the boundary node;

[0038] an iterative acceleration module, configured to obtain a second boundary voltage based on the recorded first boundary voltage in combination with a Stephenson algorithm; and use the second boundary voltage as the first boundary voltage;

[0039] An iteration stop module is used to repeatedly call the distribution network internal circulation module, the transmission network internal circulation module and the iteration acceleration module until the second boundary voltage meets the first convergence condition, and output the power flow calculation results of the transmission network and the distribution network.

[0040] An embodiment of the third aspect of the present invention provides a computer-readable storage medium, which includes a stored computer program; wherein, when the computer program is running, it controls the device where the computer-readable storage medium is located to execute the transmission and distribution coordinated power flow calculation method described in any embodiment of the first aspect above.

[0041] The fourth aspect embodiment of the present application provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the power transmission and distribution coordinated power flow calculation method of any one of the first aspect embodiments when executing the computer program.

[0042] Compared with the prior art, the embodiment of the present application provides a power transmission and distribution coordinated power flow calculation method and system, the method comprising: a boundary voltage setting step, setting a first boundary voltage of a boundary node; a distribution network internal circulation step, inputting the first boundary voltage into a two-port network model of a distribution network, and repeatedly performing a forward-backward sweep operation between the boundary node and a terminal node of the distribution network to obtain a boundary injection power and voltages and currents of each node in the distribution network; a power transmission network internal circulation step, inputting the boundary injection power into a power flow mapping model of a power transmission network, performing power flow calculation of the power transmission network, and obtaining and recording an updated first boundary voltage of the boundary node; an iteration acceleration step, based on the recorded first boundary voltage and combined with a Steffensen acceleration algorithm, obtaining a second boundary voltage; and taking the second boundary voltage as the first boundary voltage; an iteration stopping step, repeatedly performing the distribution network internal circulation step, the power transmission network internal circulation step, and the iteration acceleration step, until the second boundary voltage meets a first convergence condition, and outputting a power flow calculation result of the power transmission network and the distribution network. The present application effectively solves the convergence problem of the existing power flow calculation model and improves the convergence speed by respectively establishing a power flow calculation model for the power transmission network and the distribution network, interacting information at the boundary node, and accelerating the iteration process combined with the Steffensen acceleration algorithm. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a flowchart of an embodiment of the power transmission and distribution coordinated power flow calculation method provided by the present application;

[0044] Figure 2 is a schematic diagram of divergence phenomenon of the power transmission and distribution coordinated power flow calculation using the general form of fixed point iteration provided by the present application;

[0045] Figure 3 is a schematic diagram of the iteration curve of the power transmission and distribution coordinated power flow calculation using the Steffensen acceleration algorithm provided by the present application;

[0046] Figure 4 is a schematic diagram of the calculation result of the power transmission and distribution coordinated power flow calculation using the Steffensen acceleration algorithm provided by the present application;

[0047] Figure 5 is a schematic diagram of an embodiment of the line model in the distribution network provided by the present application;

[0048] Figure 6 is a schematic diagram of the structure of an embodiment of the power transmission and distribution coordinated power flow calculation system provided by the present application;

[0049] Figure 7 is a structural schematic diagram of one embodiment of an electronic device provided by the present application. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0051] Referring to Figure 1 is a flow schematic diagram of one embodiment of a transmission and distribution collaborative power flow calculation method provided by the present application.

[0052] The first aspect embodiment of the present application provides a transmission and distribution collaborative power flow calculation method, including steps S1 to S5, and the details are as follows:

[0053] The boundary voltage setting step S1: setting a first boundary voltage of a boundary node;

[0054] The distribution network internal circulation step S2: inputting the first boundary voltage into a two-port network model of a distribution network, and repeatedly performing a forward-backward sweep operation between the boundary node and a terminal node of the distribution network to obtain a boundary injection power and voltages and currents of each node in the distribution network; wherein the two-port network model is used to represent a voltage relationship and a current relationship between any node and another node;

[0055] The transmission network internal circulation step S3: inputting the boundary injection power into a power flow mapping model of a transmission network, performing power flow calculation of the transmission network, and obtaining and recording an updated first boundary voltage of the boundary node;

[0056] The iteration acceleration step S4: obtaining a second boundary voltage based on the recorded first boundary voltage and in combination with a Stephenson acceleration algorithm; and taking the second boundary voltage as the first boundary voltage;

[0057] The iteration stopping step S5: repeatedly performing the distribution network internal circulation step S2, the transmission network internal circulation step S3 and the iteration acceleration step S4, and outputting power flow calculation results of the transmission network and the distribution network when the second boundary voltage meets a first convergence condition.

[0058] It should be noted that the boundary node is a substation connecting the power transmission network and the power distribution network. The embodiment of the present application abstracts the power transmission and distribution collaborative power flow calculation problem into a fixed point iteration problem, establishes a power flow calculation model for the power transmission network and the power distribution network respectively, and performs information interaction at the boundary node, as follows:

[0059] (1) Power distribution network power flow calculation formula:

[0060] g D (U B )=U Dabc ;

[0061] Where g D represents the power flow function of the power distribution network, U B represents the first boundary voltage of the boundary node in the power transmission and distribution system, and U Dabc represents the three-phase voltage of each node in the power distribution network. The formula represents the three-phase power flow calculation process in the power distribution network, which is expressed in the form of a single mapping operator, that is, the first boundary voltage at the substation is given as the voltage source of the power distribution network, and the three-phase voltage U D of each node in the power distribution network is returned through the mapping g Dabc .

[0062] The power distribution network power flow calculation formula corresponds to the forward operation between the boundary node and the terminal node of the power distribution network in the power distribution network inner loop step S2, and the forward operation is realized through the two-port network model of the power distribution network.

[0063] (2) Boundary node power flow calculation formula:

[0064] g B (U B ,U Dabc )=S B ;

[0065] Where g B represents the power flow function of the substation, and S B represents the boundary injection power of the substation. The formula represents the power flow calculation process in the boundary node substation, which is expressed in the form of a single mapping operator. According to Kirchhoff's law, the boundary injection power is both the apparent power injected by the boundary node into the power distribution network and the apparent power injected by the power transmission network into the boundary area.

[0066] The boundary node power flow calculation formula corresponds to the back substitution operation between the boundary node and the terminal node of the power distribution network in the power distribution network inner loop step S2, and the back substitution operation is realized through the two-port network model of the power distribution network.

[0067] (3) Power transmission network power flow calculation formula, i.e. the power flow mapping model of the power transmission network, is as follows:

[0068] gT (S B )=U B ;

[0069] Among them, S B Inject power into the boundary; U B is the updated first boundary voltage of the boundary node; g T is the power flow function of the transmission network, which is used to characterize the power flow calculation process between the root node and the boundary node of the transmission network. The power flow calculation formula of the transmission network corresponds to the transmission network internal loop step S3.

[0070] The power flow calculation process for the transmission network can be performed by traversing the forward and reverse power flows between the root node and the boundary nodes of the transmission network. The forward and reverse traversal operations are performed using the active power balance equation and the reactive power balance equation between any two nodes, thereby obtaining the power flow distribution from the transmission network to the boundary nodes. Of course, the specific power flow calculation process for the transmission network can also be implemented using other implementations, which are not limited by the present invention.

[0071] It is worth noting that the subscript "D" in the formula or parameter of the present invention represents the distribution network, the subscript "B" represents the boundary node, the subscript "T" represents the transmission network, and the subscript "abc" represents the three-phase power flow component including a, b, and c. B and S B If there is no superscript, it indicates the first boundary voltage and boundary injection power in any mapping process; after the transmission network flow is calculated, the updated first boundary voltage is the boundary voltage fed back by the transmission network to the distribution network, which is provided to the distribution network for internal circulation. The first boundary voltage is the voltage source provided by the boundary node to the distribution network for internal circulation operation; the second boundary voltage = the first boundary voltage; the subsequent third boundary voltage is the intermediate state generated at the boundary node through the back substitution operation when executing the distribution network internal circulation step S2.

[0072] In addition, the embodiment of the present invention adopts the Steffensen acceleration algorithm, which not only solves the convergence problem of the existing power flow calculation model, but also improves the convergence speed, as follows:

[0073] Combining the distribution network flow calculation formula and the boundary node flow calculation formula, we can get

[0074]

[0075] Among them, the definition To enhance the distribution network power flow mapping, the three-phase power flow of the distribution network is calculated as the first boundary voltage U B Boundary injection power S to the boundary node Bsingle mapping. Mapping corresponding to the power distribution network in the loop step S2.

[0076] Further, the augmented power distribution network power flow mapping is combined with the power transmission network power flow mapping model into a composite mapping, i.e. the fixed point iteration form of the power transmission and distribution collaborative power flow calculation:

[0077]

[0078] The mapping Φ corresponds to the power distribution network in the loop step S2 and the power transmission network in the loop step S3.

[0079] The fixed point iteration form of the power transmission and distribution collaborative power flow calculation is exactly a fixed point problem, so it can be solved by fixed point iteration:

[0080] The formula corresponds to the iteration acceleration step S4 and the iteration stop step S5.

[0081] wherein k is the iteration number, i.e. the kth execution of the power distribution network in the loop step S2 and the power transmission network in the loop step S3; the first boundary voltage is denoted as The first boundary voltage after executing the power distribution network in the loop step S2 and the power transmission network in the loop step S3 k times is denoted as

[0082] In an optional embodiment, the second boundary voltage is calculated by the following formula:

[0083]

[0084] wherein, is the second boundary voltage; is the first boundary voltage recorded for the dth time.

[0085] It should be noted that according to the convergence theorem of fixed point iteration, the fixed point iteration form of the power transmission and distribution collaborative power flow calculation The convergence behavior in the iteration process can be analyzed by the eigenvalues of the Jacobi matrix of the composite mapping, i.e. for the iteration function Φ, if the spectral radius of its Jacobi matrix is less than 1, it is convergent, which can be expressed as:

[0086]

[0087] In the case of wide access of new energy, the sensitivity of the injection power of the root node of the power distribution network to the node voltage increases sharply, which can lead to the situation that the general form of the fixed point iteration does not meet the convergence condition.

[0088] The power transmission and distribution coordination system verification example provided by the embodiment of the application is an IEEE standard example case 14 and a distribution network example case 69_3p changed to three-phase, the distribution network example is connected to node 14 of the power transmission network example case 14 through a transformer branch, and meanwhile, three-phase power sources are added to nodes 6, 10, 32 and 59 in the distribution network example respectively, so as to simulate a scenario of high penetration of distributed power sources in the distribution network.

[0089] As shown in the figure, when the power transmission and distribution coordination system verification example adopts a general iteration form, the first boundary voltage of the boundary node changes with the number of iterations, the first boundary voltage of the power transmission and distribution coordination system diverges before 40 iterations, oscillates in a larger area within 100 iterations, and finally fails to converge. Figure 2

[0090] Based on this, the fixed point iteration problem in the embodiment of the application is solved by the Steffensen acceleration algorithm, and the convergence problem can be solved, and the specific process is as follows:

[0091] The Steffensen acceleration algorithm is a nonlinear acceleration method in the fixed point iteration method, and the expression is as follows:

[0092]

[0093] That is equivalent to:

[0094]

[0095] Wherein, is the second boundary voltage; is the first boundary voltage recorded for the dth time.

[0096] It has a fixed point x * = Φ(x * ), and Φ'(x * )≠1, so the iteration of the above formula converges at least second order, and the convergence proof is as follows:

[0097]

[0098] It can be seen that the iteration form converges under the given conditions, and the convergence speed can be proved as follows:

[0099]

[0100] Then, the derivative of the Steffensen acceleration at the fixed point can be calculated as follows:

[0101]

[0102] ​It can be proved that the fixed point acceleration method can approach the fixed point at a quadratic convergence rate, and in the transmission and distribution coordinated power flow calculation, it avoids the calculation divergence caused by the increase in the penetration rate of distributed energy in the distribution network. Figure 3 As shown in the figure, when the Steffensen acceleration algorithm is used in the verification example of the transmission and distribution coordinated system, the first boundary voltage of the boundary node changes with the number of iterations. The transmission and distribution coordinated power flow calculation reaches convergence after only 6 iterations. Figure 4 The three-phase voltage and phase angle of each node in the distribution network are displayed. For the convenience and intuitiveness of data display, the phase angle of phase B is +120° and the phase angle of phase C is -120°. It can be observed that the Steffensen acceleration algorithm ensures the accuracy of the transmission and distribution coordinated power flow calculation.

[0103] In an optional embodiment, the two-port network model is as follows:

[0104]

[0105] Among them, V gabc is the three-phase voltage of the node to ground; I abc is the three-phase current passing through the node; n and m represent node n and node m in the distribution network respectively; A, B, C and D are all generalized matrices of the transmission line between the node n and the node m, used to characterize the transmission characteristics of the transmission line.

[0106] It should be noted that the present invention provides the following specific embodiments to better illustrate the construction process of the two-port network model:

[0107] like Figure 5 FIG. 1 is a schematic diagram of an embodiment of a line model in a distribution network provided by the present invention. Figure 5 The line model in the paper adopts the accurate model of the three-phase line section of the three-phase overhead line and the underground line. In the modeling, a 3×3 matrix is ​​used to store the line impedance and admittance parameters, which are specifically expressed as:

[0108]

[0109] The r, x, and c matrices are the matrices of the line's resistance per unit length, reactance per unit length, and admittance per unit length, respectively. The subscripts a, b, and c represent the three phases of the overhead line, respectively. The self-impedance and self-admittance of each phase of the line, as well as the mutual impedance and mutual admittance between the phases, are stored here.

[0110] After defining the line model, different line types can be expressed by selecting different r, x and c matrices, and the corresponding inter-node branch parameters can be obtained by setting the line length, that is, the three-phase impedance matrix Z abc And the three-phase admittance matrix Y abcThe three-phase line model is regarded as a two-port network through the Kirchhoff's current law and the voltage law between nodes, and the two-port network model is obtained as follows:

[0111]

[0112] wherein V gabc is the three-phase voltage of the node relative to the ground, containing voltage components of a, b and c; I abc is the three-phase current passing through the node, containing current components of a, b and c; n and m respectively represent the node n and the node m in the power distribution network; A, B, C and D are all generalized matrices of the transmission line between the node n and the node m, used for representing the transmission characteristics of the transmission line. The two-port network model can deduce the voltage and the current from one node (the node m) to another node (the node n) of the power distribution line.

[0113] The specific expression form of the generalized matrices A, B, C and D should be determined when the embodiment of the present application is implemented, and the present application does not limit this; based on this, the following expression is only an example reference:

[0114]

[0115] B=Z abc ;

[0116]

[0117] wherein I is a 3*3 unit matrix.

[0118] It is worth mentioning that the two-port network model can realize the forward-backward substitution operation between the boundary node and the end node of the power distribution network.

[0119] In an optional embodiment, the calculation formula between the voltage and the current of each node in the power distribution network is as follows:

[0120]

[0121] wherein I n is the current of the node n; S n is the complex power of the node n; V n is the voltage of the node n; and * represents taking the complex conjugate.

[0122] Further, the complex power of each node in the power distribution network is determined by the measurement information.

[0123] It is worth mentioning that the loads in the power distribution network are all set as constant complex power loads, the forward-backward substitution method is used for calculation, and the current of each node of the nonlinear network is calculated by the following formula:

[0124]

[0125] where I n is the current at node n (typically for any single phase); S n is the complex power at node n (typically for the corresponding single phase); V n is the voltage at node n (typically for the corresponding single phase); * denotes taking the complex conjugate. It is noted that the three-phase-to-ground voltage V gabc at a node in the distribution network is equivalent to the three-phase voltage U Dabc at the node, V gabc where each phase of the voltage corresponds to a V n .

[0126] In the process of power flow calculation of the distribution network, the power generation equipment in the distribution network is in the form of three phases, and the three-phase-to-ground voltage of the power generation equipment is denoted as V Gabc , and the output three-phase active power and three-phase reactive power are P Gabc and Q Gabc .

[0127] The load in the distribution network is modeled in three phases, and the load is defined by the active power P dabc and the power factor , and the reactive power absorbed by the load is:

[0128]

[0129] The power parameters (the three-phase voltage V Gabc , the three-phase active power P Gabc and the three-phase reactive power Q Gabc of the power generation equipment, and the active power P dabc and the power factor of the load node) involved in the calculation of the complex power of each node in the above distribution network are import parameters, which are known variables and do not need to be obtained by forward calculation.

[0130] Therefore, when the forward calculation is performed from the boundary node to node 1 in the distribution network, the boundary current injected by the boundary node into the distribution network and the voltage and current of node 1 can be obtained by using the two-port network model and the calculation formula between the voltage and the current of node 1.

[0131] In an optional embodiment, the repeatedly performing forward calculation and backward substitution between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network comprises:

[0132] In the process of performing the power distribution network internal loop step for the kth time, a ith forward-backward sweep operation is performed between the boundary node and the terminal node of the power distribution network through the two-port network model to obtain a corresponding third boundary voltage; wherein k≥1; i≥1.

[0133] When the third boundary voltage satisfies a second convergence condition, the forward-backward sweep operation is stopped, and the boundary injection power and the voltage and current of each node in the power distribution network are obtained.

[0134] It should be noted that the power distribution network and the power transmission network in the embodiments of the present application are both converged in their respective internal iteration loops, and then exchange information at the boundary node. Therefore, the embodiments of the present application exchange the first boundary voltage (i.e., the voltage source provided by the boundary node to the power distribution network for internal loop operation), rather than the third boundary voltage (i.e., the intermediate state generated at the boundary node through the backward operation when performing the power distribution network internal loop step S2).

[0135] For the first time of performing the power distribution network internal loop step S2, the forward-backward sweep operation is repeatedly performed for each line according to the two-port network model, i.e., the forward calculation is performed from the boundary node, until a new voltage value is obtained at the terminal node, and then the backward calculation is started using the new voltage at the terminal node, so that a new power supply voltage calculation result is obtained. The forward and backward calculation processes are repeatedly performed until the difference between the calculated voltage of the boundary node and the specified voltage of the power transmission network transmitted to the boundary node is within the allowable error range, the forward-backward sweep operation is stopped, and the injection power of the boundary node at this time is output to the power flow mapping model of the power transmission network for the power transmission network internal loop operation S3.

[0136] In an optional embodiment, the second convergence condition is specifically as follows:

[0137]

[0138] wherein, is the third boundary voltage corresponding to the jth forward-backward sweep operation in the process of performing the power distribution network internal loop step for the ith time ε1 is a first preset convergence precision; V s is the specified voltage of the power transmission network initially transmitted to the boundary node.

[0139] It should be noted that in an actual power system, the three-phase imbalance phenomenon of the power distribution network is more obvious than that of the power transmission network. Therefore, when performing high-precision power transmission and distribution collaborative power flow calculation, the imbalance phenomenon of the power distribution network cannot be ignored. Based on this, the embodiments of the present application can model the power distribution network as a three-phase model, and can construct the power transmission and distribution system model in the following two ways:

[0140] (1) Full three-phase modeling: both the transmission grid and the distribution grid are modeled in three phases. The advantage of this method is that the calculation process is straightforward and simple. However, due to the large amount of calculation, it may lead to a long calculation time and fail to fully utilize the inherent characteristics of the transmission grid.

[0141] (2) Heterogeneous modeling: the transmission grid is modeled in single phase, while the distribution grid is modeled in three phases. Therefore, in the iterative calculation process, conversion is needed at the boundary nodes to coordinate the single-phase modeling of the transmission grid and the three-phase modeling of the distribution grid.

[0142] In an optional embodiment, the step of inputting the boundary injection power into the power flow mapping model of the transmission grid, performing power flow calculation of the transmission grid, obtaining and recording the updated first boundary voltage of the boundary node, comprises:

[0143] In the process of performing the transmission grid inner loop step for the kth time, when the power flow calculation of the transmission grid is completed and the single-phase voltage is provided for the boundary node, the updated first boundary voltage of the boundary node is calculated according to the following formula and recorded:

[0144]

[0145] wherein, is the updated first boundary voltage of the boundary node, including voltage components of three phases a, b and c; and is the voltage amplitude and voltage phase corresponding to phase a in the first boundary voltage; and is the voltage amplitude and voltage phase corresponding to phase b in the first boundary voltage; and is the voltage amplitude and voltage phase corresponding to phase c in the first boundary voltage.

[0146] It should be noted that in the heterogeneous modeling method, it is assumed that the three-phase voltage of the boundary node is symmetrical in each iteration step, i.e. after the single-phase power flow calculation of the transmission grid is completed, the single-phase voltage is decomposed into symmetrical three-phase voltage i.e. any voltage component corresponding to three phases a, b and c can be represented as the single-phase voltage provided by the transmission grid, such as and is the single-phase first boundary voltage amplitude and corresponding voltage phase of the boundary node transmitted by the transmission grid after the execution of the transmission grid inner loop step S3.

[0147] In an optional embodiment, the step of inputting the boundary injection power into the power flow mapping model of the transmission grid, performing power flow calculation of the transmission grid, obtaining and recording the updated first boundary voltage of the boundary node, further comprises:

[0148] In the process of performing the power grid inside loop step for the kth time, when the boundary injection power is input into the power flow mapping model of the power grid, and the power flow mapping model is a single-phase model, the input power of the power flow mapping model is calculated according to the following formula:

[0149]

[0150] Wherein, is the single-phase apparent power input into the power flow mapping model, used to represent the single-phase apparent power injected into the power grid by the boundary node; is the single-phase active power input into the power flow mapping model; is the single-phase reactive power input into the power flow mapping model; and is the active power corresponding to the a, b and c phases in the boundary injection power transmitted by the distribution grid; and is the reactive power corresponding to the a, b and c phases in the boundary injection power transmitted by the distribution grid.

[0151] It should be noted that in the heterogeneous modeling mode, the power flow calculation of the power grid needs the single-phase The three-phase injection power transmitted by the distribution grid to the boundary node can be obtained through the three-phase power flow calculation of the distribution grid (after the distribution grid inside loop step S2 is performed), that is, the three-phase injection active power of the distribution grid includes and The three-phase injection reactive power includes and At the boundary node, the input power of the power flow mapping model can be obtained by summing the three-phase injection power of the distribution grid.

[0152] Referring to Figure 6 is a structural schematic diagram of an embodiment of the power distribution collaborative power flow calculation system provided by the application.

[0153] The second aspect embodiment of the application provides a power distribution collaborative power flow calculation system for implementing the power distribution collaborative power flow calculation method described in the first aspect embodiment, and the system comprises:

[0154] The boundary voltage setting module 11 is configured to set the first boundary voltage of the boundary node.

[0155] a power distribution network internal loop module 12, configured to input the first boundary voltage into a two-port network model of a power distribution network, and repeatedly perform a forward-backward sweep operation between the boundary node and a terminal node of the power distribution network to obtain a boundary injection power and voltages and currents of each node in the power distribution network; wherein the two-port network model is used to represent a voltage relationship and a current relationship between any node and another node;

[0156] a power transmission network internal loop module 13, configured to input the boundary injection power into a power flow mapping model of a power transmission network, perform power flow calculation of the power transmission network, and obtain and record an updated first boundary voltage of the boundary node;

[0157] an iteration acceleration module 14, configured to obtain a second boundary voltage based on the recorded first boundary voltage and in combination with a Stephenson algorithm, and take the second boundary voltage as the first boundary voltage;

[0158] an iteration stopping module 15, configured to repeatedly call the power distribution network internal loop module, the power transmission network internal loop module and the iteration acceleration module until the second boundary voltage meets a first convergence condition, and output a power flow calculation result of the power transmission network and the power distribution network.

[0159] It should be noted that the power distribution and transmission collaborative power flow calculation system provided by the second aspect embodiment of the present application can realize all processes of the power distribution and transmission collaborative power flow calculation method described in the first aspect embodiment, and the functions and technical effects of each module in the system are the same as those of the power distribution and transmission collaborative power flow calculation method described in the first aspect embodiment, which will not be repeated here.

[0160] The third aspect embodiment of the present application provides a computer readable storage medium, which comprises a stored computer program; wherein the computer program controls a device where the computer readable storage medium is located to execute the power distribution and transmission collaborative power flow calculation method described in any one of the first aspect embodiments when running.

[0161] Referring to Figure 7 is a structural schematic diagram of one embodiment of an electronic device provided by the present application.

[0162] The fourth aspect embodiment of the present application provides an electronic device, which comprises a processor, a memory and a computer program stored in the memory and configured to be executed by the processor, and the processor realizes the power distribution and transmission collaborative power flow calculation method described in any one of the first aspect embodiments when executing the computer program.

[0163] Preferably, the computer program can be divided into one or more modules / units (such as computer program 1, computer program 2, …), which are stored in the memory 22 and executed by the processor 21 to complete the present application. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the computer program in the electronic device.

[0164] The processor 21 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processor 21 can also be any conventional processor. The processor 21 is the control center of the electronic device, and connects various parts of the electronic device through various interfaces and lines.

[0165] The memory 22 mainly includes a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application required by a function, etc., and the data storage area can store related data, etc. In addition, the memory 22 can be a high-speed random access memory, and can also be a non-volatile memory, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., or the memory 22 can also be other volatile solid-state storage devices.

[0166] It should be noted that the above electronic device can include, but is not limited to, a processor, a memory, and the like, and those skilled in the art can understand that Figure 7 The structure diagram shown is only an example of the structure of the above electronic device, and does not constitute a limitation on the structure of the above electronic device. The above electronic device can include more or fewer components than shown, or combine certain components, or different components.

[0167] The above is only the preferred embodiment of the present application, and it should be noted that those skilled in the art can make several improvements and modifications without departing from the technical principles of the present application, and these improvements and modifications should also be considered within the protection scope of the present application.

Claims

1. A method for calculating transmission and distribution coordinated power flow, characterized in that: include: Boundary voltage setting step: setting a first boundary voltage of a boundary node; A distribution network internal circulation step: inputting the first boundary voltage into a two-port network model of the distribution network, and repeatedly performing forward and backward substitution operations between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; wherein the two-port network model is used to characterize the voltage relationship and current relationship between any node and another node; The power transmission network internal circulation step includes: inputting the boundary injection power into a power flow mapping model of the power transmission network, performing power flow calculation of the power transmission network, and obtaining and recording the updated first boundary voltage of the boundary node; Iterative acceleration step: based on the recorded first boundary voltage, combined with the Stephenson acceleration algorithm, obtain a second boundary voltage; and use the second boundary voltage as the first boundary voltage; Iteration stopping step: repeatedly executing the distribution network internal circulation step, the transmission network internal circulation step and the iterative acceleration step until the second boundary voltage satisfies a first convergence condition, and outputting the power flow calculation results of the transmission network and the distribution network; The step of repeatedly performing forward and backward substitution operations between the boundary node and the end node of the distribution network to obtain boundary injection power and voltage and current of each node in the distribution network includes: During the kth execution of the distribution network inner loop step, performing an i-th forward-backward substitution operation between the boundary node and the terminal node of the distribution network through the two-port network model to obtain a corresponding third boundary voltage; wherein k≥1; i≥1; When the third boundary voltage satisfies a second convergence condition, stopping the forward-backward substitution operation and obtaining the boundary injection power and the voltage and current of each node in the distribution network; The second boundary voltage is calculated by the following formula: in, is the second boundary voltage; is the first boundary voltage recorded for the dth time.

2. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The two-port network model is as follows: Among them, V gabc is the three-phase voltage of the node to ground; I abc is the three-phase current passing through the node; n and m represent node n and node m in the distribution network respectively; A, B, C and D are all generalized matrices of the transmission line between the node n and the node m, used to characterize the transmission characteristics of the transmission line.

3. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The calculation formula between the voltage and current of each node in the distribution network is as follows: Among them, I n is the current at node n; S n is the complex power of node n; V n is the voltage at node n; * indicates taking the complex conjugate.

4. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The complex power of each node in the distribution network is determined by measurement information.

5. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The power flow mapping model of the transmission network is as follows: g T (S B )=U B ; Among them, S B Inject power into the boundary; U B is the updated first boundary voltage of the boundary node; g T is a power flow function of the transmission network, used to characterize the power flow calculation process between the root node and the boundary node of the transmission network.

6. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: Inputting the boundary injection power into a power flow mapping model of a transmission network, performing power flow calculation on the transmission network, and obtaining and recording the updated first boundary voltage of the boundary node include: During the kth execution of the transmission network internal circulation step, when the transmission network completes the power flow calculation and provides the single-phase voltage for the boundary node, the updated first boundary voltage of the boundary node is calculated according to the following formula and recorded: in, The updated first boundary voltage of the boundary node includes voltage components of three phases a, b and c; and are the voltage amplitude and voltage phase corresponding to phase a in the first boundary voltage; and are the voltage amplitude and voltage phase corresponding to phase b in the first boundary voltage; and are the voltage amplitude and voltage phase corresponding to phase c in the first boundary voltage.

7. The transmission and distribution coordinated power flow calculation method according to claim 6, characterized in that: The step of inputting the boundary injection power into a power flow mapping model of a transmission network, performing power flow calculation on the transmission network, and obtaining and recording the updated first boundary voltage of the boundary node further includes: During the k-th execution of the transmission network internal circulation step, when the boundary injection power is input into the power flow mapping model of the transmission network, and the power flow mapping model is a single-phase model, the input power of the power flow mapping model is calculated according to the following formula: in, The single-phase apparent power input into the power flow mapping model is used to represent the single-phase apparent power injected into the transmission network by the boundary node; The single-phase active power input to the power flow mapping model; is the single-phase reactive power input into the power flow mapping model; and The active power corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network; and It is the reactive power corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network.

8. A transmission and distribution coordinated power flow calculation system, characterized in that: The method for calculating transmission and distribution coordinated power flow according to any one of claims 1 to 7, wherein the system comprises: A boundary voltage setting module, used for setting a first boundary voltage of a boundary node; a distribution network internal circulation module, configured to input the first boundary voltage into a two-port network model of the distribution network, and repeatedly perform forward and backward substitution operations between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; wherein the two-port network model is used to characterize the voltage relationship and current relationship between any node and another node; a power transmission network internal circulation module, configured to input the boundary injection power into a power flow mapping model of the power transmission network, perform power flow calculation of the power transmission network, and obtain and record the updated first boundary voltage of the boundary node; an iterative acceleration module, configured to obtain a second boundary voltage based on the recorded first boundary voltage in combination with a Stephenson algorithm; and use the second boundary voltage as the first boundary voltage; An iteration stop module is used to repeatedly call the distribution network internal circulation module, the transmission network internal circulation module and the iteration acceleration module until the second boundary voltage meets the first convergence condition, and output the power flow calculation results of the transmission network and the distribution network.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium includes a stored computer program; wherein, when the computer program is run, it controls the device where the computer-readable storage medium is located to execute the transmission and distribution coordinated power flow calculation method according to any one of claims 1 to 7.

10. An electronic device, characterized in that: The system comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the transmission and distribution coordinated power flow calculation method according to any one of claims 1 to 7 when executing the computer program.

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