Load flow calculation method and system based on power distribution network root node voltage sensitivity

Abstract

The invention discloses a power flow calculation method and system based on power distribution network root node voltage sensitivity, and the method comprises the steps: building a power flow calculation model through representing a transmission and distribution integrated power flow calculation problem as a voltage fixed point iteration problem; iteratively solving the voltage of the transformer substation in the load flow calculation model, and obtaining an iteration result and real-time operation data after each iteration is completed; calculating a power transmission network sensitivity matrix and a power distribution network root node sensitivity matrix by adopting a least square method according to the real-time operation data; according to the power transmission network sensitivity matrix and the power distribution network root node sensitivity matrix, determining the convergence of an iteration result; and when the iteration result converges, stopping iteration solution, and obtaining a transmission and distribution integrated power flow value according to the iteration result. By adopting the embodiment of the invention, the dependency on complete network topology and parameter information in the load flow calculation process can be eliminated, and the convergence of load flow calculation can be quickly and accurately judged, so that the convergence of transmission and distribution integrated load flow calculation is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system analysis, and in particular to a power flow calculation method and system based on root node voltage sensitivity of a distribution network. Background Art

[0002] In the integrated power transmission and distribution system, the transmission network and the distribution network are coupled through the substation node. The power flow calculation is the basis for checking whether the operation of the power system is reasonable, and plays an extremely important role in the design and adjustment of the power system.

[0003] Traditional power flow calculation methods mainly rely on the topological structure and line parameters of the power grid, but this information is often incomplete or unavailable in practical applications. This leads to inaccurate models, large calculation errors, and even failure to converge in power flow calculations.

[0004] In the prior art, a variety of improved methods have been proposed to improve the convergence of power flow calculations. For example, the master-slave splitting method updates the power flow solution through alternating iterations, but the convergence performance is insufficient in the case of complex distribution networks. Other methods, such as the ring distribution network equivalent method and the Thevenin theorem equivalent method, although they have improved the accuracy of calculations to a certain extent, still have calculation errors and limited scope of application, resulting in the reliability of the power system operation mode or the planned power supply plan being difficult to meet the requirements. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to improve the convergence of the integrated transmission and distribution power flow calculation. A method and system for the integrated transmission and distribution power flow calculation based on voltage sensitivity are provided, which can get rid of the dependence on the complete network topology and parameter information in the power flow calculation process, and can quickly and accurately judge the convergence of the power flow calculation, so as to further improve the convergence of the integrated transmission and distribution power flow calculation and improve the reliability and stability of the power system.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a power flow calculation method based on the voltage sensitivity of the root node of the distribution network, comprising:

[0007] The power flow calculation problem of integrated transmission and distribution is expressed as a voltage fixed point iteration problem, and a power flow calculation model with the iteration vector as the substation voltage is established.

[0008] The power flow calculation model is solved by an iterative solution method to obtain the substation voltage, and after each iterative solution is completed, iterative results and real-time operation data of the integrated transmission and distribution power grid system are obtained;

[0009] According to the real-time operation data obtained after the current iteration solution, the least square method is used to calculate the transmission network sensitivity matrix and the distribution network root node sensitivity matrix;

[0010] Determining the convergence of the iterative result obtained after the current iterative solution according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix;

[0011] When the iterative result obtained after the current iterative solution converges, the iterative solution of the power flow calculation model is stopped, and the integrated power flow value of transmission and distribution is obtained according to the iterative result obtained after stopping the iterative solution.

[0012] As an improvement of the above scheme, the integrated power flow calculation problem of transmission and distribution is expressed as a voltage fixed point iteration problem, and a power flow calculation model with the iteration vector being the substation voltage is established, including:

[0013] According to the substation voltage and the distribution network node voltage, the first power flow function of the distribution network is obtained;

[0014] According to the substation voltage, the distribution network node voltage and the power injection of the substation, the second power flow function of the substation is obtained;

[0015] According to the substation voltage and the power injection of the substation, the third power flow function of the transmission network is obtained;

[0016] According to the first power flow function, the second power flow function and the third power flow function, the integrated transmission and distribution power flow calculation problem is expressed as a voltage fixed point iteration problem, and a power flow calculation model with the iteration vector being the substation voltage is established.

[0017] As an improvement of the above solution, the real-time operation data includes real-time operation data of the distribution network and real-time operation data of the transmission network.

[0018] As an improvement of the above solution, the iterative solution method is used to solve the power flow calculation model to obtain the substation voltage, and after each iterative solution is completed, the iterative result and the real-time operation data of the integrated transmission and distribution power grid system are obtained, including:

[0019] The power flow calculation model is solved by an iterative solution method to obtain the substation voltage, and after each iterative solution is completed, an iterative result is obtained;

[0020] Obtain the injected active power, injected reactive power and node voltage of each node in the distribution network as real-time operation data of the distribution network;

[0021] Obtain active power, reactive power, voltage amplitude and phase angle of the substation as real-time operation data of the transmission network;

[0022] The real-time operation data of the integrated transmission and distribution power grid system is obtained based on the real-time operation data of the distribution network and the real-time operation data of the transmission network.

[0023] As an improvement of the above scheme, the

[0024] According to the real-time operation data obtained after the current iteration solution, the least square method is used to calculate the transmission network sensitivity matrix and the distribution network root node sensitivity matrix, including:

[0025] Calculating a transmission network sensitivity matrix according to the transmission network real-time operation data in the real-time operation data obtained after the current iteration solution;

[0026] According to the real-time operation data of the distribution network obtained after the current iteration solution, the power change and voltage change between different operation states of the distribution network are calculated by using the Monte Carlo method;

[0027] Establishing an overdetermined set of equations according to the power variation and the voltage variation;

[0028] The least square method is used to solve the overdetermined equations to obtain the root node sensitivity matrix of the distribution network.

[0029] As an improvement of the above scheme, the real-time operation data of the distribution network obtained after the current iteration is solved, and the power change and voltage change between different operation states of the distribution network are calculated using the Monte Carlo method, including:

[0030] Clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain a power distribution close to the current operation state and a first voltage distribution corresponding thereto;

[0031] According to the first voltage distribution, a Monte Carlo method is used to generate a small power change, and a second voltage distribution under an operating state corresponding to the small power change is calculated;

[0032] Obtaining a power change according to the power distribution near the current operating state;

[0033] A voltage variation is calculated according to the first voltage distribution and the second voltage distribution.

[0034] As an improvement of the above solution, clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain the power distribution close to the current operation state and the first voltage distribution corresponding thereto includes:

[0035] Selecting two distribution network real-time operation data with the largest distance as cluster centers;

[0036] Using the K-means clustering method, the real-time operation data obtained after the current iteration of the distribution network is clustered in at least two levels according to the cluster center, and the clustering measure is calculated according to the clustering result;

[0037] According to the clustering measure, a clustering error rate is obtained;

[0038] When the clustering error rate is greater than a preset threshold, reselecting two distribution network real-time operation data with the largest distance as clustering centers in the next level;

[0039] When the clustering error rate is not greater than a preset threshold, the number of cluster centers and the clustering results are obtained;

[0040] According to the number of cluster centers and the clustering result, a power distribution close to the current operating state and a first voltage distribution corresponding thereto are obtained.

[0041] As an improvement of the above scheme, the least square method is used to solve the overdetermined equations to obtain the root node sensitivity matrix of the distribution network, including:

[0042] Introducing a residual square sum function into the overdetermined system of equations to obtain a modified overdetermined system of equations;

[0043] The least square method is adopted to differentiate the unknown parameters in the modified overdetermined equations and solve for the maximum value, thereby obtaining the root node sensitivity matrix of the distribution network.

[0044] As an improvement of the above solution, the step of determining the convergence of the iterative result obtained after the current iterative solution according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix includes:

[0045] According to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix, a comprehensive sensitivity matrix spectral radius is obtained;

[0046] When the spectral radius of the integrated sensitivity matrix is ​​smaller than a preset spectral radius threshold, it is determined that the iteration result is converged; otherwise, it is determined that the iteration result is not converged.

[0047] As an improvement of the above scheme, when the iterative result obtained after the current iterative solution converges, the iterative solution of the power flow calculation model is stopped, and the integrated power flow value of transmission and distribution is obtained according to the iterative result obtained after stopping the iterative solution, including:

[0048] When the iterative result obtained after the current iterative solution converges, stopping the iterative solution of the power flow calculation model;

[0049] According to the iterative results obtained after stopping the iterative solution, the distribution network flow value, the substation flow value and the transmission network flow value are calculated;

[0050] According to the distribution network tidal current value, the substation tidal current value and the transmission network tidal current value, a transmission and distribution integrated tidal current value is obtained.

[0051] The embodiment of the present invention further provides a power flow calculation system based on the voltage sensitivity of the root node of the distribution network, comprising:

[0052] The model building module is used to express the integrated transmission and distribution power flow calculation problem as a voltage fixed point iteration problem and to establish a power flow calculation model with the iteration vector being the substation voltage;

[0053] A data acquisition module, used to solve the power flow calculation model by an iterative solution method to obtain the substation voltage, and obtain the iterative result and the real-time operation data of the integrated transmission and distribution power grid system after each iterative solution is completed;

[0054] A sensitivity matrix calculation module, used to calculate the transmission network sensitivity matrix and the distribution network root node sensitivity matrix using the least squares method according to the real-time operation data obtained after the current iteration solution;

[0055] A convergence determination module, used to determine the convergence of the iterative result obtained after the current iterative solution according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix;

[0056] The flow value calculation module is used to stop the iterative solution of the flow calculation model when the iterative result obtained after the current iterative solution converges, and obtain the integrated transmission and distribution flow value according to the iterative result obtained after stopping the iterative solution.

[0057] As an improvement of the above solution, the model building module includes:

[0058] A first power flow function acquisition unit, used for obtaining a first power flow function of the distribution network according to the substation voltage and the distribution network node voltage;

[0059] A second power flow function acquisition unit, used for obtaining a second power flow function of the substation according to the substation voltage, the distribution network node voltage and the power injection of the substation;

[0060] A third power flow function acquisition unit, used for obtaining a third power flow function of the transmission network according to the substation voltage and the power injection of the substation;

[0061] The model building unit is used to express the integrated transmission and distribution power flow calculation problem as a voltage fixed point iteration problem according to the first power flow function, the second power flow function and the third power flow function, and to establish a power flow calculation model in which the iteration vector is the substation voltage.

[0062] As an improvement of the above solution, the real-time operation data includes real-time operation data of the distribution network and real-time operation data of the transmission network.

[0063] As an improvement of the above solution, the data acquisition module includes:

[0064] An iterative result acquisition unit is used to solve the power flow calculation model by an iterative solution method to obtain the substation voltage, and obtain an iterative result after each iterative solution is completed;

[0065] A distribution network real-time operation data acquisition unit is used to acquire the injected active power, injected reactive power and node voltage of each node in the distribution network as the real-time operation data of the distribution network;

[0066] The transmission network real-time operation data acquisition unit is used to acquire the active power, reactive power, voltage amplitude and phase angle of the substation as the real-time operation data of the transmission network;

[0067] The real-time operation data acquisition unit is used to obtain the real-time operation data of the integrated transmission and distribution power grid system according to the real-time operation data of the distribution network and the real-time operation data of the transmission network.

[0068] As an improvement of the above solution, the sensitivity matrix calculation module includes:

[0069] A transmission network sensitivity matrix calculation unit, used to calculate a transmission network sensitivity matrix according to the transmission network real-time operation data in the real-time operation data obtained after the current iteration solution;

[0070] An electric parameter variation calculation unit, used to calculate the power variation and voltage variation between different operating states of the distribution network by using the Monte Carlo method according to the real-time operation data of the distribution network obtained after the current iteration solution;

[0071] An overdetermined equations establishment unit, used for establishing an overdetermined equations according to the power variation and the voltage variation;

[0072] The equation solving unit is used to solve the overdetermined equations by using the least square method to obtain the root node sensitivity matrix of the distribution network.

[0073] As an improvement of the above solution, the electric parameter variation calculation unit is specifically used for:

[0074] Clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain a power distribution close to the current operation state and a first voltage distribution corresponding thereto;

[0075] According to the first voltage distribution, a Monte Carlo method is used to generate a small power change, and a second voltage distribution under an operating state corresponding to the small power change is calculated;

[0076] Obtaining a power change according to the power distribution near the current operating state;

[0077] A voltage variation is calculated according to the first voltage distribution and the second voltage distribution.

[0078] As an improvement of the above solution, clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain the power distribution close to the current operation state and the first voltage distribution corresponding thereto includes:

[0079] Selecting two distribution network real-time operation data with the largest distance as cluster centers;

[0080] Using the K-means clustering method, the real-time operation data obtained after the current iteration of the distribution network is clustered in at least two levels according to the cluster center, and the clustering measure is calculated according to the clustering result;

[0081] According to the clustering measure, a clustering error rate is obtained;

[0082] When the clustering error rate is greater than a preset threshold, reselecting two distribution network real-time operation data with the largest distance as clustering centers in the next level;

[0083] When the clustering error rate is not greater than a preset threshold, the number of cluster centers and the clustering results are obtained;

[0084] According to the number of cluster centers and the clustering result, a power distribution close to the current operating state and a first voltage distribution corresponding thereto are obtained.

[0085] As an improvement of the above solution, the equation solving unit is specifically used for:

[0086] Introducing a residual square sum function into the overdetermined system of equations to obtain a modified overdetermined system of equations;

[0087] The least square method is adopted to differentiate the unknown parameters in the modified overdetermined equations and solve for the maximum value, thereby obtaining the root node sensitivity matrix of the distribution network.

[0088] As an improvement of the above solution, the convergence determination module includes:

[0089] A spectrum radius calculation unit, used for obtaining a comprehensive sensitivity matrix spectrum radius according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix;

[0090] The convergence determination unit is used to determine that the iteration result is converged when the spectral radius of the comprehensive sensitivity matrix is ​​less than a preset spectral radius threshold; otherwise, determine that the iteration result is not converged.

[0091] As an improvement of the above solution, the power flow value calculation module includes:

[0092] An iteration stopping unit, used for stopping the iterative solution of the power flow calculation model when the iterative result obtained after the current iterative solution converges;

[0093] A separate power flow value calculation unit, used to calculate the power flow value of the distribution network, the power flow value of the substation and the power flow value of the transmission network according to the iterative result obtained after stopping the iterative solution;

[0094] The integrated power flow value calculation unit is used to obtain the integrated power flow value of transmission and distribution according to the distribution network power flow value, the substation power flow value and the transmission network power flow value.

[0095] Compared with the prior art, the present invention discloses a power flow calculation method and system based on the voltage sensitivity of the root node of the distribution network. By expressing the integrated power flow calculation problem as a voltage fixed point iteration problem, a power flow calculation model with the iteration vector being the substation voltage is established; the power flow calculation model is solved by an iterative solution method to obtain the substation voltage, and the iteration result and the real-time operation data of the integrated power grid system are obtained after each iterative solution is completed; according to the real-time operation data obtained after the current iterative solution, the least squares method is used to calculate the transmission network sensitivity matrix and the distribution network root node sensitivity matrix; according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix, the convergence of the iterative result obtained after the current iterative solution is determined; when the iterative result obtained after the current iterative solution converges, the iterative solution of the power flow calculation model is stopped, and the integrated power flow value of the distribution is obtained according to the iterative result obtained after stopping the iterative solution. By adopting the embodiments of the present invention, it is possible to get rid of the dependence on the complete network topology and parameter information in the power flow calculation process, and to quickly and accurately determine the convergence of the power flow calculation, so as to further improve the convergence of the integrated transmission and distribution power flow calculation and improve the reliability and stability of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Figure 1 It is a schematic flow chart of the steps of a power flow calculation method based on the voltage sensitivity of a root node of a distribution network provided by an embodiment of the present invention;

[0097] Figure 2 It is a structural schematic diagram of a transmission and distribution integrated power grid system provided by an embodiment of the present invention;

[0098] Figure 3It is a schematic diagram of the calculation time of a power flow calculation and the result of the comprehensive sensitivity matrix spectrum radius changing with the load rate provided by an embodiment of the present invention;

[0099] Figure 4 It is a structural schematic diagram of a power flow calculation system based on the voltage sensitivity of the root node of the distribution network provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0100] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0101] In the description of the specification and claims, it is to be understood that the terms first, second, etc. in the specification and claims are only used for the purpose of describing the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated, nor necessarily describing the order or time sequence. The terms are interchangeable where appropriate. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0102] With the increasing penetration of new energy, especially distributed photovoltaic and wind power, the traditional power flow calculation method of transmission and distribution separation can no longer meet the needs of modern power grids. The power flow calculation of transmission and distribution integration needs to consider the coupling of transmission network and distribution network at the same time, which makes the convergence problem of calculation more complicated.

[0103] In the integrated transmission and distribution system, the interaction between the transmission network and the distribution network is coupled through the substation node. The traditional power flow calculation method mainly relies on the topological structure and line parameters of the power grid, but this information is often incomplete or unavailable in practical applications. This leads to inaccurate models, large calculation errors, and even non-convergence problems in the power flow calculation, which in turn makes it difficult to meet the reliability requirements of the power system obtained based on the power flow.

[0104] Based on the above considerations, the present invention provides a power flow calculation method based on the voltage sensitivity of the root node of the distribution network. Figure 1 In this embodiment, the power flow calculation method based on the voltage sensitivity of the root node of the distribution network is specifically performed through steps S1 to S5:

[0105] S1. The integrated transmission and distribution power flow calculation problem is expressed as a voltage fixed point iteration problem, and a power flow calculation model with the iteration vector as the substation voltage is established.

[0106] It should be noted that the fixed point iteration form has been widely used as a mathematical tool in the calculation of integrated power flow of transmission and distribution. In the embodiment of the present invention, the power flow calculation problem is expressed as a fixed point iteration problem in mathematics by means of the fixed point iteration form, and the convergence of the power flow calculation problem is analyzed by the fixed point theory, thereby solving the problem that the traditional method relies on complete network topology and parameter information.

[0107] It should also be noted that the power flow calculation model is applied to the power system with integrated transmission and distribution, see Figure 2 , Figure 2 It is a schematic diagram of the structure of a transmission and distribution integrated power grid system provided by an embodiment of the present invention. It can be understood that the power flow calculation model established under the condition of transmission and distribution integration needs to include the distribution network, substation and transmission network.

[0108] S2. The power flow calculation model is solved by an iterative solution method to obtain the substation voltage, and after each iterative solution is completed, iterative results and real-time operation data of the integrated transmission and distribution power grid system are obtained.

[0109] In the embodiment of the present invention, the only iteration variable of the power flow calculation model generated by the fixed point iteration principle, that is, the fixed point, is the substation voltage. Therefore, in each iteration process, only the substation voltage needs to be iteratively calculated, so that the iteration result gradually approaches the power flow solution.

[0110] S3. According to the real-time operation data obtained after the current iterative solution, the least square method is used to calculate the transmission network sensitivity matrix and the distribution network root node sensitivity matrix.

[0111] In the integrated power flow calculation of transmission and distribution, the power flow calculation can be decomposed into the interaction between the transmission network and the distribution network. In the embodiment of the present invention, the coupling part of the transmission network and the distribution network is specifically considered, and the convergence of the iterative results is further analyzed by calculating the transmission network sensitivity matrix and the distribution network root node sensitivity matrix.

[0112] S4. Determine the convergence of the iterative result obtained after the current iterative solution according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix.

[0113] By combining the transmission network sensitivity matrix and the distribution network root node sensitivity matrix, a comprehensive sensitivity matrix can be obtained to reflect the coupling between the transmission network and the distribution network.

[0114] In some embodiments, according to the fixed point iteration theory, when the spectral radius of the integrated sensitivity matrix is ​​less than 1, it is determined that the iteration result is converged.

[0115] In other embodiments, considering the computational complexity and precision in practical applications, the matrix norm is used to simplify the judgment condition. When the norm of the comprehensive sensitivity matrix is ​​less than 1, it is determined that the iterative result is also convergent.

[0116] S5. When the iterative result obtained after the current iterative solution converges, the iterative solution of the power flow calculation model is stopped, and the integrated power flow value of transmission and distribution is obtained according to the iterative result obtained after stopping the iterative solution.

[0117] When the power flow results converge, it means that the substation voltage obtained by iterating the power flow calculation model can meet the power flow requirements. The power grid can be further optimized and adjusted according to the iteration results, so that the power flows of the transmission network, substation and distribution network have good convergence performance.

[0118] In the above scheme, the power flow calculation of integrated transmission and distribution is modeled and analyzed through fixed point iteration, and convergence is further judged through sensitivity identification. It can get rid of the dependence on complete network topology and parameter information in the power flow calculation process, and can quickly and accurately judge the convergence of the power flow calculation, so as to further improve the convergence of the power flow calculation of integrated transmission and distribution.

[0119] As a preferred implementation, step S1, expressing the integrated transmission and distribution power flow calculation problem as a voltage fixed point iteration problem, and establishing a power flow calculation model with the iteration vector being the substation voltage, includes:

[0120] According to the substation voltage and the distribution network node voltage, the first power flow function of the distribution network is obtained;

[0121] According to the substation voltage, the distribution network node voltage and the power injection of the substation, the second power flow function of the substation is obtained;

[0122] According to the substation voltage and the power injection of the substation, the third power flow function of the transmission network is obtained;

[0123] According to the first power flow function, the second power flow function and the third power flow function, the integrated transmission and distribution power flow calculation problem is expressed as a voltage fixed point iteration problem, and a power flow calculation model with the iteration vector being the substation voltage is established.

[0124] For example, the first power flow function of the distribution network is G D (U B )=U D , the second power flow function of the substation is G B (U B ,U D )=S B , the third power flow function of the transmission network is G T (S B)=U B The power flow calculation model is Among them, U B is the substation voltage, U D is the node voltage of the distribution network, S B For power injection into substations, is the substation voltage at the kth iteration, is the substation voltage at the k+1th iteration.

[0125] It should be noted that the above-mentioned first power flow function, second power flow function, third power flow function and power flow calculation model all contain other parameters, which are related to the specific settings of the integrated transmission and distribution power system. Those skilled in the art will know how to establish functions and models. The embodiment of the present invention aims to provide a method for converting traditional power flow calculation methods through fixed point iteration, which does not need to rely on complete network topology and parameter information, thereby simplifying the modeling process.

[0126] Preferably, the real-time operation data includes real-time operation data of the distribution network and real-time operation data of the transmission network.

[0127] It should be noted that the real-time operation data may be node operation data collected or predicted in real time, or may be a hybrid drive of actual data and generated data to improve the robustness of the power flow calculation model.

[0128] Further, as a preferred implementation, step S2, using an iterative solution method to solve the power flow calculation model to obtain the substation voltage, and obtaining the iterative result and the real-time operation data of the integrated transmission and distribution power grid system after each iterative solution is completed, including:

[0129] The power flow calculation model is solved by an iterative solution method to obtain the substation voltage, and after each iterative solution is completed, an iterative result is obtained;

[0130] Obtain the injected active power, injected reactive power and node voltage of each node in the distribution network as real-time operation data of the distribution network;

[0131] Obtain active power, reactive power, voltage amplitude and phase angle of the substation as real-time operation data of the transmission network;

[0132] The real-time operation data of the integrated transmission and distribution power grid system is obtained based on the real-time operation data of the distribution network and the real-time operation data of the transmission network.

[0133] It should be noted that the iteration result includes the substation voltage and the power flow value of the integrated transmission and distribution power grid system obtained in the current iteration.

[0134] It should also be noted that in the embodiment of the present invention, when acquiring real-time operating data, active power and reactive power are acquired for the power data, and when the sensitivity matrix is ​​subsequently generated, an active sensitivity matrix and a reactive sensitivity matrix will also be generated.

[0135] As a preferred implementation, step S3, according to the real-time operation data obtained after the current iteration solution, the least squares method is used to calculate the transmission network sensitivity matrix and the distribution network root node sensitivity matrix, and steps S31 to S34 are performed:

[0136] S31. Calculate a transmission network sensitivity matrix according to the real-time operation data of the transmission network in the real-time operation data obtained after the current iterative solution.

[0137] Exemplarily, the transmission network sensitivity matrix S T for Among them, P B is the active power of the substation, Q B is the reactive power of the substation, V B is the substation voltage amplitude, i B is the substation voltage phase angle.

[0138] S32. According to the real-time operation data of the distribution network obtained after the current iterative solution, a Monte Carlo method is used to calculate the power change and voltage change between different operation states of the distribution network.

[0139] S33. Establish an overdetermined set of equations according to the power variation and the voltage variation.

[0140] S34. Solve the overdetermined equations using the least squares method to obtain a root node sensitivity matrix of the distribution network.

[0141] Further, preferably, step S32 includes:

[0142] Clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain a power distribution close to the current operation state and a first voltage distribution corresponding thereto;

[0143] A Monte Carlo method is used to generate a small power change, and a second voltage distribution under an operating state corresponding to the small power change is calculated;

[0144] Obtaining a power change according to the power distribution near the current operating state;

[0145] A voltage variation is calculated according to the first voltage distribution and the second voltage distribution.

[0146] In an embodiment of the present invention, the Monte Carlo method is used to generate small power changes of the MN group (M>>2k); wherein M is the number of groups of real-time operating data, N is the number of groups of power changes and voltage changes between different operating states obtained through step S32, and k is the number of nodes.

[0147] Exemplarily, for each voltage change node, M equations, i.e., an overdetermined set of equations, may be established according to the changes in power and voltage:

[0148]

[0149] Furthermore, clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain the power distribution close to the current operation state and the first voltage distribution corresponding thereto includes:

[0150] Selecting two distribution network real-time operation data with the largest distance as cluster centers;

[0151] Using the K-means clustering method, the real-time operation data obtained after the current iteration of the distribution network is clustered in at least two levels according to the cluster center, and the clustering measure is calculated according to the clustering result;

[0152] According to the clustering measure, a clustering error rate is obtained;

[0153] When the clustering error rate is greater than a preset threshold, reselecting two distribution network real-time operation data with the largest distance as clustering centers in the next level;

[0154] When the clustering error rate is not greater than a preset threshold, the number of cluster centers and the clustering results are obtained;

[0155] According to the number of cluster centers and the clustering result, a power distribution close to the current operating state and a first voltage distribution corresponding thereto are obtained.

[0156] In the embodiment of the present invention, in order to get rid of the dependence of the traditional clustering algorithm on the selected number of cluster centers K, an improved hierarchical K-means clustering algorithm based on the maximum distance method is adopted, and the cluster initial value is selected by the maximum distance method.

[0157] In some embodiments, there are M groups of real-time operation data acquired, and the original set of power distribution is P = [P1, P2, ..., P M ], the power distribution vector of any scenario is P i =[p i,1 ,p i,2 ,…,p i,T ], and set the initial number of clusters to K1.

[0158] Based on the maximum distance method, K1 initial cluster centers are selected. First, the two samples with the largest distance are selected as the initial cluster centers. Calculate the sample distance d, and select the sample with the largest distance product with other samples as the third cluster center in the remaining M-2 scenes; thus, K1 initial cluster centers are obtained.

[0159] Perform K-means clustering, assign all samples to the nearest cluster center, set the number of iterations l = 1, and calculate the l-th clustering measure function value J(l). The clustering measure function is Among them, M i is the number of scenes in the i-th class, is the jth data vector in the i-th class; C i is the cluster center of the ith class.

[0160] Then proceed to the next level of clustering: select the class with the largest radius among all clusters, and use r i =max‖P j -C i ‖, j = 1, 2, ..., M i Calculate the cluster radius, select the two samples with the largest distance in the cluster as the new cluster centers; re-perform K-means clustering based on the cluster centers, set l=l+1, and calculate the l+1th clustering measure function value J(l+1).

[0161] Define ε=(J(l)–J(l+1)) / J(l). If ε>ε0, return to continue iteration, where ε0 is a given threshold, which can be set according to the clustering measure function value change curve; otherwise, the algorithm ends, and the number of cluster centers and clustering results are output. In the clustering results, N groups of corresponding actual power data are obtained, and then the voltage distribution data under the power distribution scenario is obtained. According to the classified voltage distribution data, the power distribution close to the current operating state and the corresponding first voltage distribution are obtained.

[0162] Further, through Establish an overdetermined system of equations; among them, is the sensitivity vector of the node numbered i in the distribution network to the active power, is the sensitivity vector of the node numbered i in the distribution network to reactive power, is the comprehensive sensitivity vector of the node numbered i in the distribution network to reactive power, and is the unknown quantity in the overdetermined system of equations.

[0163] As a preferred implementation, step S34 includes:

[0164] Introducing a residual square sum function into the overdetermined system of equations to obtain a modified overdetermined system of equations;

[0165] The least square method is adopted to differentiate the unknown parameters in the modified overdetermined equations and solve for the maximum value, thereby obtaining the root node sensitivity matrix of the distribution network.

[0166] It should be noted that the overdetermined equations generally have no solution, so it is necessary to find a suitable To make the equation as valid as possible, in the embodiment of the present invention, the optimal solution of the overdetermined system of equations is further obtained by introducing the residual square sum function.

[0167] In some embodiments, by Introducing the residual sum of squares function in the overdetermined equations, for the unknown parameters Taking the differential and solving for the maximum value can get the optimal solution of least squares

[0168] As a preferred implementation, step S4, determining the convergence of the iterative result obtained after the current iterative solution according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix, includes:

[0169] According to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix, a comprehensive sensitivity matrix spectral radius is obtained;

[0170] When the spectral radius of the integrated sensitivity matrix is ​​smaller than a preset spectral radius threshold, it is determined that the iteration result is converged; otherwise, it is determined that the iteration result is not converged.

[0171] In a preferred embodiment of the present invention, the preset spectral radius threshold is 1, and the spectral radius is characterized by the norm of the comprehensive sensitivity matrix. When the norm of the comprehensive sensitivity matrix is ​​less than 1, it is considered that the spectral radius of the comprehensive sensitivity matrix is ​​less than 1, and the iterative result is determined to converge.

[0172] For example, the IEEE standard case 14 is used as the transmission network case, and the modified case 69 is used as the distribution network case. On the basis of the original distribution network case, distributed power sources with a capacity of 700kW are added to nodes 14 and 32 respectively, and the control mode is PV. The distribution network case is connected to node 14 of the transmission network. The scenario of changing the load rate of the distribution network from 0.7 to 2.3 is adopted to simulate the gradual divergence of the power flow calculation of the integrated transmission and distribution system under the condition of heavy load of the distribution network.

[0173] The convergence calculation method provided by the embodiment of the present invention is obtained based on the least square method, while the most traditional convergence calculation formula is calculated based on physical principles. The embodiment of the present invention will use two methods to analyze the convergence of power flow calculation.

[0174] The voltage sensitivity matrix obtained based on physical principles is:

[0175]

[0176] Where S is the voltage sensitivity matrix, J is the Jacobian matrix of power flow calculation, and the Jacobian matrix can be expressed as:

[0177]

[0178] Considering that the value of θ is very small in general, we can approximately consider cosθ=1, sinθ=0. Further simplification can yield:

[0179]

[0180] The voltage amplitude per unit value is around 1.0pu. By performing Gaussian elimination on the above equation, we can get an approximate expression for voltage sensitivity:

[0181] ΔU=S U-P ΔP+S U-Q ΔQ;

[0182]

[0183] Among them, S U-P is the active power-voltage sensitivity, S U-Q is the reactive power-voltage sensitivity, and the sensitivity of the voltage at the root node of the distribution network to the reactive power can be further obtained.

[0184] By combining the transmission network sensitivity matrix and the distribution network root node sensitivity matrix, the comprehensive sensitivity matrix can be obtained. According to the fixed point iteration theory, when the spectrum radius satisfies , it indicates that the iteration result converges.

[0185] See also Figure 3 , Figure 3 The red solid line in the figure is the comprehensive sensitivity matrix spectral radius calculated by physical principles, the red dotted line is the comprehensive sensitivity matrix spectral radius calculated by the least squares method provided in the embodiment of the present invention, and the blue line is the power flow calculation time used in the embodiment of the present invention. It can be seen that the values ​​calculated by the two methods are basically the same, and the proposed criterion based on the comprehensive sensitivity matrix spectral radius can also characterize the convergence of the integrated power flow of transmission and distribution. This shows that the power flow calculation method provided in the embodiment of the present invention has good accuracy.

[0186] It should also be noted that the traditional method of calculating the spectral radius of the comprehensive sensitivity matrix based on physical principles is an accurate expression of the node voltage sensitivity, but it requires multiple matrix inversion operations. For distribution networks with a large number of nodes and ill-conditioned matrices, there may be problems such as long calculation time and numerical instability.

[0187] Further, as a preferred implementation, step S5, when the iterative result obtained after the current iterative solution converges, stopping the iterative solution of the power flow calculation model, and obtaining the integrated power flow value of transmission and distribution according to the iterative result obtained after stopping the iterative solution, includes:

[0188] When the iterative result obtained after the current iterative solution converges, stopping the iterative solution of the power flow calculation model;

[0189] According to the iterative results obtained after stopping the iterative solution, the distribution network flow value, the substation flow value and the transmission network flow value are calculated;

[0190] According to the distribution network tidal current value, the substation tidal current value and the transmission network tidal current value, a transmission and distribution integrated tidal current value is obtained.

[0191] In some embodiments, after step S5, the safety index and power supply quality of the power system operation are calculated according to the integrated transmission and distribution flow value; and the power system is adjusted according to the safety index and the power supply quality. Specifically, when adjusting the power system, according to the transmission network flow value, the distribution network flow value and the substation flow value, the preset accuracy requirements are used as constraints to adjust the equipment parameters of the power system.

[0192] The power flow calculation method based on the voltage sensitivity of the root node of the distribution network provided by the embodiment of the present invention can get rid of the dependence on the complete network topology and parameter information in the power flow calculation process, and can quickly and accurately determine the convergence of the power flow calculation, so as to further improve the convergence of the integrated transmission and distribution power flow calculation and improve the reliability and stability of the power system.

[0193] See also Figure 4 The embodiment of the present invention provides a power flow calculation system based on the voltage sensitivity of the root node of the distribution network, including a model building module 11, a data acquisition module 12, a sensitivity matrix calculation module 13, a convergence determination module 14 and a power flow value calculation module 15, wherein:

[0194] A model building module 11 is used to express the integrated transmission and distribution power flow calculation problem as a voltage fixed point iteration problem, and to establish a power flow calculation model in which the iteration vector is the substation voltage;

[0195] A data acquisition module 12 is used to solve the power flow calculation model by an iterative solution method to obtain the substation voltage, and obtain the iterative result and the real-time operation data of the integrated transmission and distribution power grid system after each iterative solution is completed;

[0196] A sensitivity matrix calculation module 13 is used to calculate the transmission network sensitivity matrix and the distribution network root node sensitivity matrix using the least square method according to the real-time operation data obtained after the current iteration solution;

[0197] A convergence determination module 14 is used to determine the convergence of the iterative result obtained after the current iterative solution according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix;

[0198] The power flow value calculation module 15 is used to stop the iterative solution of the power flow calculation model when the iterative result obtained after the current iterative solution converges, and obtain the integrated power flow value of transmission and distribution according to the iterative result obtained after stopping the iterative solution.

[0199] As a preferred implementation, the model building module 11 includes:

[0200] A first power flow function acquisition unit, used for obtaining a first power flow function of the distribution network according to the substation voltage and the distribution network node voltage;

[0201] A second power flow function acquisition unit, used for obtaining a second power flow function of the substation according to the substation voltage, the distribution network node voltage and the power injection of the substation;

[0202] A third power flow function acquisition unit, used for obtaining a third power flow function of the transmission network according to the substation voltage and the power injection of the substation;

[0203] The model building unit is used to express the integrated transmission and distribution power flow calculation problem as a voltage fixed point iteration problem according to the first power flow function, the second power flow function and the third power flow function, and to establish a power flow calculation model in which the iteration vector is the substation voltage.

[0204] As a preferred implementation, the real-time operation data includes real-time operation data of the distribution network and real-time operation data of the transmission network.

[0205] Further, preferably, the data acquisition module 12 includes:

[0206] An iterative result acquisition unit is used to solve the power flow calculation model by an iterative solution method to obtain the substation voltage, and obtain an iterative result after each iterative solution is completed;

[0207] A distribution network real-time operation data acquisition unit is used to acquire the injected active power, injected reactive power and node voltage of each node in the distribution network as the real-time operation data of the distribution network;

[0208] The transmission network real-time operation data acquisition unit is used to acquire the active power, reactive power, voltage amplitude and phase angle of the substation as the real-time operation data of the transmission network;

[0209] The real-time operation data acquisition unit is used to obtain the real-time operation data of the integrated transmission and distribution power grid system according to the real-time operation data of the distribution network and the real-time operation data of the transmission network.

[0210] As a preferred implementation, the sensitivity matrix calculation module 13 includes:

[0211] A transmission network sensitivity matrix calculation unit, used to calculate a transmission network sensitivity matrix according to the transmission network real-time operation data in the real-time operation data obtained after the current iteration solution;

[0212] An electric parameter variation calculation unit, used to calculate the power variation and voltage variation between different operating states of the distribution network by using the Monte Carlo method according to the real-time operation data of the distribution network obtained after the current iteration solution;

[0213] An overdetermined equations establishment unit, used for establishing an overdetermined equations according to the power variation and the voltage variation;

[0214] The equation solving unit is used to solve the overdetermined equations by using the least square method to obtain the root node sensitivity matrix of the distribution network.

[0215] Further, preferably, the electrical parameter variation calculation unit is specifically used for:

[0216] Clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain a power distribution close to the current operation state and a first voltage distribution corresponding thereto;

[0217] According to the first voltage distribution, a Monte Carlo method is used to generate a small power change, and a second voltage distribution under an operating state corresponding to the small power change is calculated;

[0218] Obtaining a power change according to the power distribution near the current operating state;

[0219] A voltage variation is calculated according to the first voltage distribution and the second voltage distribution.

[0220] Furthermore, as a preferred embodiment, the

[0221] Clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain a power distribution close to the current operation state and a first voltage distribution corresponding thereto, including:

[0222] Selecting two distribution network real-time operation data with the largest distance as cluster centers;

[0223] Using the K-means clustering method, the real-time operation data obtained after the current iteration of the distribution network is clustered in at least two levels according to the cluster center, and the clustering measure is calculated according to the clustering result;

[0224] According to the clustering measure, a clustering error rate is obtained;

[0225] When the clustering error rate is greater than a preset threshold, reselecting two distribution network real-time operation data with the largest distance as clustering centers in the next level;

[0226] When the clustering error rate is not greater than a preset threshold, the number of cluster centers and the clustering results are obtained;

[0227] According to the number of cluster centers and the clustering result, a power distribution close to the current operating state and a first voltage distribution corresponding thereto are obtained.

[0228] As a preferred implementation, the equation solving unit is specifically used for:

[0229] Introducing a residual square sum function into the overdetermined system of equations to obtain a modified overdetermined system of equations;

[0230] The least square method is adopted to differentiate the unknown parameters in the modified overdetermined equations and solve for the maximum value, thereby obtaining the root node sensitivity matrix of the distribution network.

[0231] As a preferred implementation, the convergence determination module 14 includes:

[0232] A spectrum radius calculation unit, used for obtaining a comprehensive sensitivity matrix spectrum radius according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix;

[0233] The convergence determination unit is used to determine that the iteration result is converged when the spectral radius of the comprehensive sensitivity matrix is ​​less than a preset spectral radius threshold; otherwise, determine that the iteration result is not converged.

[0234] As a preferred implementation, the power flow value calculation module 15 includes:

[0235] An iteration stopping unit, used for stopping the iterative solution of the power flow calculation model when the iterative result obtained after the current iterative solution converges;

[0236] A separate power flow value calculation unit, used to calculate the power flow value of the distribution network, the power flow value of the substation and the power flow value of the transmission network according to the iterative result obtained after stopping the iterative solution;

[0237] The integrated power flow value calculation unit is used to obtain the integrated power flow value of transmission and distribution according to the distribution network power flow value, the substation power flow value and the transmission network power flow value.

[0238] A power flow calculation system based on the voltage sensitivity of the root node of the distribution network provided by the embodiment of the present invention can get rid of the dependence on the complete network topology and parameter information in the power flow calculation process, and can quickly and accurately determine the convergence of the power flow calculation, so as to further improve the convergence of the integrated transmission and distribution power flow calculation and improve the reliability and stability of the power system.

[0239] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0240] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A power flow calculation method based on root node voltage sensitivity of distribution network, characterized in that: include: The integrated power flow calculation problem of transmission and distribution is expressed as a voltage fixed point iteration problem, and a power flow calculation model with the iteration vector as the substation voltage is established. The power flow calculation model is solved by an iterative solution method to obtain the substation voltage, and after each iterative solution is completed, iterative results and real-time operation data of the integrated transmission and distribution power grid system are obtained; According to the real-time operation data obtained after the current iteration solution, the least square method is used to calculate the transmission network sensitivity matrix and the distribution network root node sensitivity matrix; Determining the convergence of the iterative result obtained after the current iterative solution according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix; When the iterative result obtained after the current iterative solution converges, the iterative solution of the power flow calculation model is stopped, and the integrated power flow value of transmission and distribution is obtained according to the iterative result obtained after stopping the iterative solution.

2. A power flow calculation method based on the voltage sensitivity of the root node of the distribution network as claimed in claim 1, characterized in that: The integrated transmission and distribution power flow calculation problem is expressed as a voltage fixed point iteration problem, and a power flow calculation model with the iteration vector being the substation voltage is established, including: According to the substation voltage and the distribution network node voltage, the first power flow function of the distribution network is obtained; According to the substation voltage, the distribution network node voltage and the power injection of the substation, the second power flow function of the substation is obtained; According to the substation voltage and the power injection of the substation, the third power flow function of the transmission network is obtained; According to the first power flow function, the second power flow function and the third power flow function, the integrated transmission and distribution power flow calculation problem is expressed as a voltage fixed point iteration problem, and a power flow calculation model with the iteration vector being the substation voltage is established.

3. A power flow calculation method based on root node voltage sensitivity of distribution network as claimed in claim 1, characterized in that: The real-time operation data includes the real-time operation data of the distribution network and the real-time operation data of the transmission network.

4. A power flow calculation method based on root node voltage sensitivity of distribution network as claimed in claim 3, characterized in that: The iterative solution method is used to solve the power flow calculation model to obtain the substation voltage, and after each iterative solution is completed, the iterative result and the real-time operation data of the integrated transmission and distribution power grid system are obtained, including: The power flow calculation model is solved by an iterative solution method to obtain the substation voltage, and after each iterative solution is completed, an iterative result is obtained; Obtain the injected active power, injected reactive power and node voltage of each node in the distribution network as real-time operation data of the distribution network; Obtain active power, reactive power, voltage amplitude and phase angle of the substation as real-time operation data of the transmission network; The real-time operation data of the integrated transmission and distribution power grid system is obtained based on the real-time operation data of the distribution network and the real-time operation data of the transmission network.

5. A power flow calculation method based on root node voltage sensitivity of distribution network as claimed in claim 3, characterized in that: The method of calculating the transmission network sensitivity matrix and the distribution network root node sensitivity matrix using the least squares method according to the real-time operation data obtained after the current iteration solution includes: Calculating a transmission network sensitivity matrix according to the transmission network real-time operation data in the real-time operation data obtained after the current iteration solution; According to the real-time operation data of the distribution network obtained after the current iteration solution, the power change and voltage change between different operation states of the distribution network are calculated by using the Monte Carlo method; Establishing an overdetermined set of equations according to the power variation and the voltage variation; The least square method is used to solve the overdetermined equations to obtain the root node sensitivity matrix of the distribution network.

6. A power flow calculation method based on root node voltage sensitivity of distribution network as claimed in claim 5, characterized in that: The method of calculating the power change and voltage change between different operating states of the distribution network using the Monte Carlo method according to the real-time operating data of the distribution network obtained after the current iteration solution includes: Clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain a power distribution close to the current operation state and a first voltage distribution corresponding thereto; According to the first voltage distribution, a Monte Carlo method is used to generate a small power change, and a second voltage distribution under an operating state corresponding to the small power change is calculated; Obtaining a power change according to the power distribution near the current operating state; A voltage variation is calculated according to the first voltage distribution and the second voltage distribution.

7. A power flow calculation method based on root node voltage sensitivity of distribution network as claimed in claim 6, characterized in that: The clustering of the real-time operation data of the power distribution network in the real-time operation data obtained after the current iteration solution to obtain the power distribution close to the current operation state and the first voltage distribution corresponding thereto includes: Selecting two distribution network real-time operation data with the largest distance as cluster centers; Using the K-means clustering method, the real-time operation data obtained after the current iteration of the distribution network is clustered in at least two levels according to the cluster center, and the clustering measure is calculated according to the clustering result; According to the clustering measure, a clustering error rate is obtained; When the clustering error rate is greater than a preset threshold, reselecting two distribution network real-time operation data with the largest distance as clustering centers in the next level; When the clustering error rate is not greater than a preset threshold, the number of cluster centers and the clustering results are obtained; According to the number of cluster centers and the clustering result, a power distribution close to the current operating state and a first voltage distribution corresponding thereto are obtained.

8. A power flow calculation method based on root node voltage sensitivity of distribution network as claimed in claim 5, characterized in that: The least square method is used to solve the overdetermined equations to obtain the root node sensitivity matrix of the distribution network, including: Introducing a residual square sum function into the overdetermined system of equations to obtain a modified overdetermined system of equations; The least square method is adopted to differentiate the unknown parameters in the modified overdetermined equations and solve for the maximum value, thereby obtaining the root node sensitivity matrix of the distribution network.

9. A power flow calculation method based on root node voltage sensitivity of distribution network as claimed in claim 1, characterized in that: The step of determining the convergence of the iterative result obtained after the current iterative solution according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix includes: According to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix, a comprehensive sensitivity matrix spectral radius is obtained; When the spectral radius of the integrated sensitivity matrix is ​​smaller than a preset spectral radius threshold, it is determined that the iteration result is converged; otherwise, it is determined that the iteration result is not converged.

10. A power flow calculation method based on root node voltage sensitivity of distribution network as claimed in claim 2, characterized in that: When the iterative result obtained after the current iterative solution converges, the iterative solution of the power flow calculation model is stopped, and the transmission and distribution integrated power flow value is obtained according to the iterative result obtained after the iterative solution is stopped, including: When the iterative result obtained after the current iterative solution converges, stopping the iterative solution of the power flow calculation model; According to the iterative results obtained after stopping the iterative solution, the distribution network flow value, the substation flow value and the transmission network flow value are calculated; According to the distribution network tidal current value, the substation tidal current value and the transmission network tidal current value, a transmission and distribution integrated tidal current value is obtained.

11. A power flow calculation system based on root node voltage sensitivity of distribution network, characterized in that: include: The model building module is used to express the integrated transmission and distribution power flow calculation problem as a voltage fixed point iteration problem and to establish a power flow calculation model with the iteration vector being the substation voltage; A data acquisition module, used to solve the power flow calculation model by an iterative solution method to obtain the substation voltage, and obtain the iterative result and the real-time operation data of the integrated transmission and distribution power grid system after each iterative solution is completed; A sensitivity matrix calculation module, used to calculate the transmission network sensitivity matrix and the distribution network root node sensitivity matrix using the least squares method according to the real-time operation data obtained after the current iteration solution; A convergence determination module, used to determine the convergence of the iterative result obtained after the current iterative solution according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix; The flow value calculation module is used to stop the iterative solution of the flow calculation model when the iterative result obtained after the current iterative solution converges, and obtain the integrated transmission and distribution flow value according to the iterative result obtained after stopping the iterative solution.

12. A power flow calculation system based on root node voltage sensitivity of distribution network as claimed in claim 11, characterized in that: The model building module comprises: A first power flow function acquisition unit, used for obtaining a first power flow function of the distribution network according to the substation voltage and the distribution network node voltage; A second power flow function acquisition unit, used for obtaining a second power flow function of the substation according to the substation voltage, the distribution network node voltage and the power injection of the substation; A third power flow function acquisition unit, used for obtaining a third power flow function of the transmission network according to the substation voltage and the power injection of the substation; The model building unit is used to express the integrated transmission and distribution power flow calculation problem as a voltage fixed point iteration problem according to the first power flow function, the second power flow function and the third power flow function, and to establish a power flow calculation model in which the iteration vector is the substation voltage.

13. A power flow calculation system based on root node voltage sensitivity of distribution network according to claim 11, characterized in that: The real-time operation data includes the real-time operation data of the distribution network and the real-time operation data of the transmission network.

14. A power flow calculation system based on root node voltage sensitivity of distribution network as claimed in claim 13, characterized in that: The data acquisition module comprises: An iterative result acquisition unit is used to solve the power flow calculation model by an iterative solution method to obtain the substation voltage, and obtain an iterative result after each iterative solution is completed; A distribution network real-time operation data acquisition unit is used to acquire the injected active power, injected reactive power and node voltage of each node in the distribution network as the real-time operation data of the distribution network; The transmission network real-time operation data acquisition unit is used to acquire the active power, reactive power, voltage amplitude and phase angle of the substation as the real-time operation data of the transmission network; The real-time operation data acquisition unit is used to obtain the real-time operation data of the integrated transmission and distribution power grid system according to the real-time operation data of the distribution network and the real-time operation data of the transmission network.

15. A power flow calculation system based on root node voltage sensitivity of distribution network as claimed in claim 13, characterized in that: The sensitivity matrix calculation module comprises: A transmission network sensitivity matrix calculation unit, used to calculate a transmission network sensitivity matrix according to the transmission network real-time operation data in the real-time operation data obtained after the current iteration solution; An electric parameter variation calculation unit, used to calculate the power variation and voltage variation between different operating states of the distribution network by using the Monte Carlo method according to the real-time operation data of the distribution network obtained after the current iteration solution; An overdetermined equations establishment unit, used for establishing an overdetermined equations according to the power variation and the voltage variation; The equation solving unit is used to solve the overdetermined equations by using the least square method to obtain the root node sensitivity matrix of the distribution network.

16. A power flow calculation system based on root node voltage sensitivity of distribution network as claimed in claim 15, characterized in that: The electric parameter variation calculation unit is specifically used for: Clustering the real-time operation data of the distribution network in the real-time operation data obtained after the current iteration solution to obtain a power distribution close to the current operation state and a first voltage distribution corresponding thereto; According to the first voltage distribution, a Monte Carlo method is used to generate a small power change, and a second voltage distribution under an operating state corresponding to the small power change is calculated; Obtaining a power change according to the power distribution near the current operating state; A voltage variation is calculated according to the first voltage distribution and the second voltage distribution.

17. A power flow calculation system based on root node voltage sensitivity of distribution network as claimed in claim 16, characterized in that: The clustering of the real-time operation data of the power distribution network in the real-time operation data obtained after the current iteration solution to obtain the power distribution close to the current operation state and the first voltage distribution corresponding thereto includes: Selecting two distribution network real-time operation data with the largest distance as cluster centers; Using the K-means clustering method, the real-time operation data obtained after the current iteration of the distribution network is clustered in at least two levels according to the cluster center, and the clustering measure is calculated according to the clustering result; According to the clustering measure, a clustering error rate is obtained; When the clustering error rate is greater than a preset threshold, reselecting two distribution network real-time operation data with the largest distance as clustering centers in the next level; When the clustering error rate is not greater than a preset threshold, the number of cluster centers and the clustering results are obtained; According to the number of cluster centers and the clustering result, a power distribution close to the current operating state and a first voltage distribution corresponding thereto are obtained.

18. A power flow calculation system based on root node voltage sensitivity of distribution network as claimed in claim 15, characterized in that: The equation solving unit is specifically used for: Introducing a residual square sum function into the overdetermined system of equations to obtain a modified overdetermined system of equations; The least square method is adopted to differentiate the unknown parameters in the modified overdetermined equations and solve for the maximum value, thereby obtaining the root node sensitivity matrix of the distribution network.

19. A power flow calculation system based on root node voltage sensitivity of distribution network according to claim 11, characterized in that: The convergence determination module comprises: A spectrum radius calculation unit, used for obtaining a comprehensive sensitivity matrix spectrum radius according to the transmission network sensitivity matrix and the distribution network root node sensitivity matrix; The convergence determination unit is used to determine that the iteration result is converged when the spectral radius of the comprehensive sensitivity matrix is ​​less than a preset spectral radius threshold; otherwise, determine that the iteration result is not converged.

20. A power flow calculation system based on root node voltage sensitivity of distribution network as claimed in claim 12, characterized in that: The power flow value calculation module includes: An iteration stopping unit, used for stopping the iterative solution of the power flow calculation model when the iterative result obtained after the current iterative solution converges; A separate power flow value calculation unit, used to calculate the power flow value of the distribution network, the power flow value of the substation and the power flow value of the transmission network according to the iterative result obtained after stopping the iterative solution; The integrated power flow value calculation unit is used to obtain the integrated power flow value of transmission and distribution according to the distribution network power flow value, the substation power flow value and the transmission network power flow value.

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