Multi-infeed power system double-layer power flow calculation method, system, device and medium

Abstract

The present application belongs to the technical field of power system analysis, and discloses a multi-power transmission and distribution power system double-layer power flow calculation method, system, device and medium, to solve the poor convergence, low efficiency and non-uniform phase angle of the existing distributed power flow calculation in the multi-TSO multi-DSO scene. The present application divides the TSO area and the DSO area, sets a virtual boundary bus and determines the master and slave TSO to unify the phase angle; in the upper layer iteration, the TSO and the DSO exchange node voltage and power, and the first or non-converged is iterated for a limited number of times; based on the equivalent method, the external network is equivalent to injection and admittance, and the power flow is solved independently combined with the DSO; when not converged, the multiple historical iteration results are corrected and continued to iterate. The present application protects the data privacy while ensuring the convergence and accuracy, and improves the efficiency.

Description

Technical Field

[0001] This invention belongs to the field of power system analysis technology, specifically relating to a two-layer power flow calculation method, system, equipment, and medium for multi-transmission and distribution power systems. Background Technology

[0002] With the continuous expansion of power system scale and the existence of management and data barriers between different power grid operators, traditional centralized power flow calculation methods face the dual challenges of excessive communication burden and difficulty in guaranteeing data privacy in practical applications. Distributed power flow calculation, because it can effectively avoid the above problems, has become a research hotspot in the field of power system analysis.

[0003] Existing distributed power flow (DPFL) calculation methods primarily focus on two scenarios: one is DPFL coordination among multiple transmission system operators (TSOs), and the other is DPFL between a single TSO and its multiple distribution system operators (DSOs). However, existing technologies are insufficient for DPFL in integrated transmission and distribution systems that simultaneously involve multiple TSOs and DSOs. As the electrical coupling between transmission and distribution networks deepens, the power interaction and voltage support relationships between them become increasingly close, making DPFL in multi-TSO / multi-DSO scenarios even more valuable for practical applications.

[0004] Existing distributed power flow algorithms for multi-regional power systems suffer from the following shortcomings when applied to multi-TSO and multi-DSO systems: First, due to the significant differences between the boundary coupling characteristics between transmission and distribution regions and those between traditional transmission network regions, existing algorithms exhibit poor convergence performance and are prone to boundary variable oscillations or even divergence in strongly coupled scenarios, making it difficult to meet the needs of practical engineering applications. Second, in the two-layer iterative framework, the lower-layer distribution network power flow calculation requires a high degree of refinement and is computationally time-consuming. If precise convergence of the lower layer is required in every iteration of the upper layer, the overall computational efficiency will be severely reduced. Third, existing methods lack a unified and effective coordination mechanism for handling boundary nodes, making it difficult to ensure the consistency of the voltage phase angle reference benchmark across the entire system, thus affecting the accuracy of the calculation results.

[0005] In summary, existing technologies have significant shortcomings in terms of convergence, computational efficiency, and phase angle benchmark consistency when processing distributed power flow calculations in multi-TSO and multi-DSO integrated transmission and distribution systems, and still need to be improved. Summary of the Invention

[0006] Based on the aforementioned shortcomings and deficiencies in the existing technology, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the existing technology. In other words, one of the objectives of this invention is to provide a two-layer power flow calculation method, system, device, and medium for multi-transmission and distribution power systems that meet one or more of the aforementioned requirements, so as to improve the convergence and computational efficiency of distributed power flow calculation in multi-TSO and multi-DSO integrated transmission and distribution systems.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a two-layer power flow calculation method for a multi-transmission and distribution power system, wherein the multi-transmission and distribution power system includes multiple transmission system operators (TSOs) and multiple distribution system operators (DSOs), and the method includes the following steps: S1. Divide the multi-transmission and distribution power system into multiple transmission areas managed by TSO and multiple distribution areas managed by DSO, and connect each TSO area to at least one DSO area. S2. Set up virtual boundary buses at the boundary of tie lines between different TSO regions, determine the master TSO and slave TSO to unify the voltage phase angle reference of the whole system, set the type of each virtual boundary bus according to the master-slave relationship, establish the local node admittance matrix of each region, initialize the bus state variables, and set the upper-level convergence tolerance and lower-level convergence tolerance. S3. Repeat the upper-level iteration until the voltage changes of all virtual boundary buses are less than the upper-level convergence tolerance. The upper-level iteration includes: S31. Each TSO region performs its own power flow calculation for the transmission network. During the execution, the current TSO region and its subordinate DSO regions alternately exchange the root node voltage and the root node equivalent power until the change in root node voltage and power is less than the lower-level convergence tolerance. If this upper-level iteration is the first execution, or the boundary voltage change in the previous upper-level iteration is not less than the upper-level convergence tolerance, the alternation exchange is only performed for a finite number of approximate iterations; otherwise, it is executed until full convergence. S32. After completing the lower-level convergence in step S31, each TSO region uses the equivalent method to convert the external network into equivalent power injection and equivalent admittance at the virtual boundary bus. Combined with the equivalent power injection of the subordinate DSO obtained in the lower-level iteration in S31, the power flow of the transmission network in this region is solved independently. Among them, the external network of the main TSO region is its adjacent slave TSO region, and the external network of the slave TSO region is the main TSO region or the adjacent slave TSO region that has been determined for reference. S33. Determine whether the voltage change of all virtual boundary buses is less than the upper-level convergence tolerance. If so, terminate the iteration; otherwise, after correcting the voltage amplitude of the virtual boundary buses using the results of the most recent historical iterations, return to step S31 to continue the next upper-level iteration.

[0008] In a second aspect, the present invention provides a two-layer power flow calculation system for a multi-transmission and distribution power system, for implementing the two-layer power flow calculation method as described in the first aspect.

[0009] Thirdly, the present invention provides an electronic device, the electronic device including a memory, a processor and a computer program, wherein when the computer program is executed by the processor, it implements the two-layer power flow calculation method as described in the first aspect.

[0010] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the two-layer power flow calculation method as described in the first aspect.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention sets up virtual boundary buses at the tie line boundaries between different TSO regions and determines the master TSO and slave TSO to unify the voltage phase angle reference of the entire system. The type of each virtual boundary bus is set according to the master-slave relationship, so that the voltage phase angle of all TSO regions can be traced back to the system balance node in the master TSO. This avoids the power flow calculation error caused by the inconsistency of phase angle reference in different regions and ensures the accuracy of the power flow calculation results of the entire system.

[0012] 2. In the upper-level iteration process, this invention uses multiple historical iteration results to perform iterative variable correction on the voltage amplitude of the virtual boundary bus, which effectively suppresses the oscillation of boundary variables in multi-region strongly coupled scenarios, solves the problem of easy divergence in existing technologies in multi-TSO and multi-DSO systems, and significantly improves the convergence performance and numerical stability of the algorithm.

[0013] 3. In the lower-level iteration, the present invention adopts the approximate lower-level solution technique. In the early stage of the upper-level iteration, only a limited number of lower-level iterations are performed to obtain an approximate solution. The lower-level iteration is performed until complete convergence in the later stage of the upper-level iteration, thus avoiding the computational overhead caused by repeatedly performing a large number of detailed power flow calculations of the distribution network in the early stage of the upper-level iteration.

[0014] 4. This invention adopts a two-layer distributed computing architecture. Each TSO region only exchanges virtual boundary bus voltage and power information. Each DSO only returns the active power, reactive power and necessary control mode information of the root node to its TSO. It does not involve any internal network topology, line parameters, load distribution and detailed data of distributed power sources, which fully protects the data privacy of each operator and overcomes the shortcomings of centralized power flow computing that is difficult to apply in practice due to data barriers.

[0015] 5. The distributed power flow calculation results of this invention can achieve the same accuracy as centralized power flow calculation after convergence. While ensuring the calculation accuracy, it solves the practical problem that centralized power flow calculation cannot be implemented in scenarios with multiple operating entities, and has practical engineering application value.

[0016] Further or more detailed beneficial effects will be described in conjunction with specific embodiments in the detailed implementation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the two-layer power flow calculation method described in Embodiment 1 of the present invention.

[0019] Figure 2 This is a schematic diagram of the partitioned structure of the multi-transmission and distribution power system described in Embodiment 1 of the present invention.

[0020] Figure 3 This is a schematic diagram illustrating the decoupling and coordination calculation between a single TSO region and its multiple subordinate DSO regions in the lower-level iteration described in Embodiment 1 of the present invention.

[0021] Figure 4 This is an equivalent schematic diagram of the decoupling of each TSO region based on the Ward equivalent method as described in Embodiment 1 of the present invention.

[0022] Figure 5 This is a structural diagram of the electronic device described in Embodiment 3 of the present invention.

[0023] Figure 6 This is a comparison curve of the convergence process of the three convergence algorithms, DPF, BLDPF-II and BLDPF-III, described in Embodiment 5 of the present invention.

[0024] Icon labels: 500. Electronic equipment; 501. Processor; 502. Communication bus; 503. User interface; 504. Network interface; 505. Memory. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0026] In the following description, several embodiments of the present invention are provided. Different embodiments can be substituted or combined. Therefore, the present invention can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present invention should also be considered to include embodiments containing one or more other possible combinations of A, B, C, and D, even if such embodiments are not explicitly described in the following text.

[0027] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of the invention. Various processes or components may be appropriately omitted, substituted, or added to the various examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

[0028] To facilitate a better understanding of the embodiments of the present invention, its application scenarios will be explained before providing a detailed explanation of the specific implementation methods.

[0029] The two-layer power flow calculation method described in the embodiments of this specification is applied to the distributed power flow calculation scenario of multiple transmission and distribution power systems. In these scenarios, the application of the two-layer power flow calculation method aims to solve the power flow distribution of multiple transmission and distribution power systems by combining the coordination iteration between upper-layer transmission system operators and the coordination iteration between lower-layer transmission system operators and distribution system operators in a two-layer architecture, under the premise of exchanging only boundary information without exposing the internal data of each operator.

[0030] The following is a brief explanation of the multiple transmission and distribution power systems, transmission system operators (TSOs), distribution system operators (DSOs), TSO regions, DSO regions, virtual boundary buses, local node admittance matrices, upper-level convergence tolerance, lower-level convergence tolerance, upper-level iteration, and equivalent methods involved in the various embodiments of this specification: A multi-transmission and distribution power system is a power system composed of multiple transmission networks and multiple distribution networks. The transmission networks and distribution networks are connected through root nodes, and different transmission networks are connected through tie lines. The transmission networks are managed by the transmission system operator, and the distribution networks are managed by the distribution system operator.

[0031] Transmission System Operators (TSOs) are the entities responsible for managing high-voltage transmission networks. They are responsible for the operation, maintenance, and development of the transmission system and, when necessary, interconnection with other systems. Each TSO manages a transmission area.

[0032] Distribution System Operator (DSO) is the entity responsible for managing the medium- and low-voltage distribution network. It is responsible for the operation, maintenance, and development of the distribution system, and for interconnecting with other systems when necessary. Each DSO manages one distribution area.

[0033] A TSO area refers to the coverage area of ​​a transmission network operated and managed by a single TSO, including transmission buses, transmission lines, transformers and other transmission equipment, as well as root node buses connected to the various DSOs under that TSO and tie line boundary buses connected to other TSO areas.

[0034] A DSO area refers to the coverage area of ​​a distribution network operated and managed by a DSO, including distribution buses, distribution lines, distribution transformers, loads, and distributed generation equipment, and is connected to the transmission bus of its respective TSO area through a root node.

[0035] Virtual boundary bus: A virtual node set at the boundary of the tie line between different TSO regions to achieve decoupling and coordination between different TSO regions. Each virtual boundary bus belongs to a TSO region and is connected to the virtual boundary buses of adjacent TSO regions through the equivalent impedance of the tie line. The coordinator maintains the virtual boundary bus number, its TSO, adjacent TSOs, boundary bus voltage magnitude, phase angle, boundary power injection, and iteration status information.

[0036] Local node admittance matrix: Each TSO region or DSO region establishes a node admittance matrix based on the network topology and line parameters within its jurisdiction, describing the voltage-current relationship between buses within that region. Within a TSO region, the local node admittance matrix is ​​divided into blocks according to internal buses and virtual boundary buses, including a virtual boundary bus self-admittance sub-matrix, an internal bus self-admittance sub-matrix, and a mutual admittance sub-matrix between the virtual boundary bus and internal buses.

[0037] The upper-level convergence tolerance is a preset threshold used to determine whether the upper-level multi-TSO distributed power flow iteration has converged. It is defined as the maximum voltage change of all virtual boundary buses between two adjacent upper-level iterations. When this maximum value is less than the upper-level convergence tolerance, the upper-level iteration is considered to have converged. The upper-level convergence tolerance is used to control the accuracy of the power flow calculation for the entire system, and its value can be set according to the engineering accuracy requirements.

[0038] The lower-level convergence tolerance is a preset threshold used to determine whether the distributed power flow iteration of a single TSO and multiple DSOs has converged. It is defined as the normalized maximum value of the voltage and power changes of each DSO root node between two adjacent lower-level iterations. When this maximum value is less than the lower-level convergence tolerance, the lower-level iteration is considered to have converged. The lower-level convergence tolerance is used to control the accuracy of the local power flow calculation between each TSO and its subordinate DSOs, and its value can be set according to the engineering accuracy requirements.

[0039] Upper-level iteration refers to the distributed power flow coordination iterative process carried out between each TSO region. In upper-level iteration, each TSO region solves the power flow of its own transmission network and exchanges voltage and power information only through virtual boundary buses until the boundary voltage of the entire system meets the convergence condition.

[0040] Equivalent method: In distributed power flow calculation, the impact of external networks (all other transmission areas outside the current TSO area) on the virtual boundary bus of the current area is equivalent to the equivalent power injection and equivalent admittance at the boundary bus. Using this method, each TSO area can account for the influence of neighboring areas when calculating its own power flow, without needing to obtain the internal network topology and parameter data of neighboring areas.

[0041] Example 1: like Figure 1 As shown, this embodiment provides a two-layer power flow calculation method for a multi-transmission and distribution power system, wherein the multi-transmission and distribution power system includes multiple transmission system operators (TSOs) and multiple distribution system operators (DSOs). The method includes the following steps: Step S1, System Partitioning and Initialization: The multi-transmission and distribution power system is divided into multiple transmission areas managed by TSOs and multiple distribution areas managed by DSOs, with each TSO area connected to at least one DSO area. For example... Figure 2 As shown, the entire multi-transmission and distribution power system consists of multiple transmission networks (TN) and multiple distribution networks (DN). Each transmission network is managed by a Transmission Station (TSO), and each distribution network is managed by a Distribution Station Station (DSO). Different TSOs are connected through transmission tie lines, and TSOs and DSOs are connected through the root nodes of the distribution network.

[0042] Virtual boundary buses are set up at the tie-line boundaries between different TSO regions, and a coordinator is set up to maintain information such as the virtual boundary bus number, its associated TSO, adjacent TSOs, boundary bus voltage magnitude, phase angle, boundary power injection, and iterative status. The TSO containing the unique slack node for the entire system is defined as the master TSO, and the remaining TSOs are defined as slave TSOs. The master TSO provides a system-wide voltage phase angle reference; slave TSOs determine their local slack nodes step by step based on their connection relationships with the master TSO or a slave TSO with a predetermined reference.

[0043] The type of each virtual boundary bus shall be set according to the following rules: The virtual boundary bus of the main TSO region is set to be updated by power flow calculation with voltage magnitude and phase angle, and active power and reactive power as known quantities. For a slave TSO region directly connected to the main TSO region, one virtual boundary bus connected to the main TSO region can be selected as the local balancing node of the slave TSO region. The remaining virtual boundary buses in the slave TSO region are set to the type where the voltage amplitude is given, the active power is given, and the reactive power is determined by power flow calculation. For a slave TSO region that is not directly connected to the main TSO region, an adjacent slave TSO region with a determined local balancing node is selected as a reference region, and a virtual boundary bus between the slave TSO region and the reference region is selected as the local balancing node of the slave TSO region. The remaining virtual boundary buses of the slave TSO region are set to the type where the voltage amplitude is given, the active power is given, and the reactive power is determined by power flow calculation.

[0044] With the above settings, the voltage phase angle of all TSO regions can be traced back to the system balance node in the main TSO, thereby avoiding power flow calculation errors caused by inconsistent phase angle references in different regions.

[0045] Establish the local node admittance matrix for each region. For the th Each TSO region has its local admittance matrix divided into blocks according to the internal busbar and the virtual boundary busbar: (1), In equation (1), This represents the vector of injected current into the virtual boundary bus. This represents the vector of the busbar injected into the region. Represents the virtual boundary bus voltage vector; This represents the bus voltage vector within the region; , , , These represent the submatrices obtained by dividing the nodal admittance matrix according to the boundary bus and the internal bus, respectively.

[0046] Initialize the bus state variables. Initialization is performed using a flat start method, meaning that the bus voltage amplitude (excluding the slack bus) is initialized to a unit value of 1.0 pu, and the phase angle is initialized to 0; the PV bus voltage amplitude is initialized to its given voltage value; the active and reactive power of the PQ bus are given according to the initial load and generation plan. The initial equivalent power injection of the root node in each DSO area is obtained from the initial power flow calculation of the distribution network, or taken as the estimated net load value of the corresponding distribution network for that DSO area.

[0047] Set the upper-level convergence tolerance and lower-level convergence tolerance Preferably, in this embodiment and All The maximum number of upper-level iterations and the maximum number of lower-level iterations are set according to the system size.

[0048] Step S2, Upper-layer multi-TSO distributed power flow iterative calculation: Repeat the upper-level iteration until the voltage changes of all virtual boundary buses are less than the upper-level convergence tolerance. The upper-level iteration includes S31 to S33: In each upper-level iteration, each TSO region performs its own transmission network power flow calculation. Before performing the power flow calculation for its own region, the lower-level TSO-DSO distributed power flow iteration calculation is performed first.

[0049] Step S31: Lower-level single TSO multi-DSO distributed power flow iterative calculation: like Figure 3 As shown, in the lower-level iteration, decoupling and coordination calculations are performed between a single TSO region and its multiple subordinate DSO regions. The current TSO region and its subordinate DSO regions alternately exchange the root node voltage and root node equivalent power until the change in root node voltage and power is less than the lower-level convergence tolerance. .

[0050] Specifically, the TSO sends the currently estimated TSO-DSO junction voltage to each of its subordinate DSOs. The information sent by the TSO includes at least the root node voltage magnitude and phase angle.

[0051] Each Distributed Power Controller (DSO) uses the received root node voltage as the boundary condition for power flow calculation in the distribution network. The root node is considered as the slack node or external power source node in the power flow calculation, and the internal power flow calculation of the distribution network is performed. Power flow calculation can employ the Newton-Raphson method, forward-backward substitution method, or other power flow algorithms suitable for distribution networks. For distribution networks containing distributed generation (DG), DG can be connected to the power flow equations according to a control mode with given active power and voltage amplitude (PV control), a control mode with given active power and reactive power (PQ control), or a droop control model. When a DG operates under a control mode with given active power and voltage amplitude, if its reactive power reaches a set upper or lower limit, the DG is converted to a control mode with given active power and reactive power for processing.

[0052] After each DSO completes the power flow calculation of the distribution network, it calculates the equivalent power injection at its root node: (2), In equation (2), Indicates the first During the next lower-level iteration, the first Complex power injection at the root node of each DSO; Indicates active power injection; Indicates reactive power injection; It represents the imaginary unit.

[0053] Each DSO injects the equivalent power of its root node into its corresponding TSO. The transmitted information includes only the active and reactive power of the root node and necessary control mode information, excluding the internal network topology, line parameters, load distribution, and detailed data on distributed generation sources within the DSO, thus achieving data privacy protection for the distribution network.

[0054] When incorporating the equivalent power injection of each DSO root node into the power flow equations of the regional transmission network on the TSO side, a unified power injection notation is adopted: injection from the network bus is positive, and load consumption is negative. If a DSO exhibits net load at its root node (i.e., absorbs power from the transmission network), then this power is treated as a negative injection (or positive load) at the TSO root node according to the above convention; if a DSO feeds power back to the transmission network, then it is treated as a positive injection. If the engineering software uses the opposite notation, then a unified sign conversion is performed during the interaction between the TSO and DSO.

[0055] After receiving the root node power injections reported by all subordinate DSOs, the TSO uses them as known power injections or equivalent loads at the root node of the transmission network, recalculates the power flow in the TSO's transmission area, and obtains the updated root node voltage.

[0056] Determine if the lower-level TSO-DSO distributed power flow has converged. Define the lower-level residual as: (3), In equation (3), Indicates the first The maximum boundary residual of the next lower iteration; This represents the set of DSOs under the current TSO; Indicates the first During the next lower-level iteration, the first The voltage of the root node of the DSO; Indicates the first During the next lower-level iteration, the first Power injection into the root node of each DSO; This represents the system power reference value.

[0057] If the following conditions are met: (4), Then it is determined that the lower-level power flow calculation between the TSO and its subordinate DSOs has converged.

[0058] Specifically, if this upper-level iteration is the first execution, or the boundary voltage change in the previous upper-level iteration is not less than the upper-level convergence tolerance. If the alternation is performed, then only a finite number of approximate iterations are performed; otherwise, it is performed until complete convergence. That is, only a fixed number of iterations are performed in the early stages of the upper-level iterations. The approximate lower-level solution is obtained by alternating iterations, and then the obtained root node power is directly injected for upper-level calculation; in the later stage of upper-level iteration, it is iterated according to equation (3) until complete convergence.

[0059] The fixed number of times The selection is based on the sensitivity of the power injection at the root node of the distribution network to changes in the root node voltage. The following indicators can be used to estimate the sensitivity of the root node voltage to changes in the root node voltage. Sensitivity of each DSO: (5), In equation (5), Indicates the first Approximate sensitivity of the power of the DSO root node to the root node voltage; and These represent the root node power injection in two adjacent lower-level iterations, respectively; and These represent the root node voltages in two adjacent lower-level iterations, respectively. To prevent small positive numbers with a denominator of zero.

[0060] when A smaller value indicates that the distribution network is not sensitive to voltage disturbances at the transmission network boundary, and a smaller value can be used. ,For example ;when A larger value indicates strong coupling between the distribution network and the transmission network, and the value should be increased appropriately. ,For example or In general engineering applications, A value of 1 to 3 can be used to achieve a balance between convergence and computational efficiency.

[0061] The judgment condition for the approximate lower-level solution is: (6), In equation (6), Indicates the first The virtual boundary bus voltage vector after the next upper-level iteration; Indicates the first The virtual boundary bus voltage vector after the next upper-level iteration; This indicates the upper-level convergence tolerance; It represents the infinite norm.

[0062] When the above equation is not satisfied, it indicates that the current upper-level transmission network boundary voltage has not yet approached the final solution. In this case, the lower-level TSO-DSO power flow will only execute a fixed number of times. The alternating iterations are used to obtain an approximate solution for the lower layer. When the above equation is satisfied, it indicates that the upper layer boundary voltage is close to the final solution. At this time, the lower layer TSO-DSO power flow is iterated according to equation (3) until it is fully converged.

[0063] Step S32: Solve the power flow of the transmission network in each TSO region based on the equivalent method: After completing the lower-level convergence in step S31, each TSO region uses the equivalent method to convert the external network into equivalent power injection and equivalent admittance at the virtual boundary bus. Combined with the equivalent power injection of the subordinate DSO obtained in the lower-level iteration in S31, the power flow of the transmission network in this region is solved independently.

[0064] like Figure 4 As shown, each TSO region calculates the equivalent impact of the external network on its virtual boundary bus based on the Ward equivalent method. The external network of the main TSO region is its adjacent slave TSO regions, and the external network of the slave TSO regions is the main TSO region or a neighboring slave TSO region with a determined reference. The main TSO receives the current boundary bus voltage information reported by the coordinator or neighboring slave TSOs, calculates the equivalent power injection and equivalent admittance of the external network on the main TSO region, and incorporates the equivalent power injection of all DSO root nodes into the main TSO power flow equations. Each slave TSO receives boundary information from the main TSO, coordinator, or neighboring slave TSOs, calculates the equivalent quantities of the external network, and, in conjunction with the power injection of its own subordinate DSO root nodes, calculates the power flow of its local transmission network using the Newton-Raphson method. The information exchanged between adjacent TSO regions is the virtual boundary bus voltage and power information.

[0065] Taking the equivalent power injection from the external network of the TSO as an example, the equivalent power injection from the external region to the boundary bus can be expressed as: (7), In equation (7), This represents the power injection vector from the external network of the TSO to the virtual boundary bus; This represents a diagonal matrix composed of virtual boundary bus voltage vectors; This represents the mutual admittance matrix between the virtual boundary bus and the bus inside the TSO; This represents the self-admittance sub-matrix corresponding to the internal busbar of the TSO; This represents the power injection vector from the internal bus of the TSO; This represents the voltage vector from the internal bus of the TSO; the division in the formula represents the element-by-element division of the vector.

[0066] The equivalent admittance matrix formed by the external network on the virtual boundary bus is: (8), In equation (8), This represents the equivalent admittance matrix from the external network of the TSO to the boundary bus. This represents the self-admittance matrix between virtual boundary buses; This represents the mutual admittance matrix between the internal busbars of the TSO and the virtual boundary busbars. The corresponding matrix can be obtained in the same way for external networks of the main TSO or other external networks of the slave TSO. and .

[0067] For the The power flow equations for each busbar are as follows: (9), (10) In equations (9) and (10), and They represent the first Calculated values ​​of active and reactive power for each busbar; and They represent the first The and the first Voltage amplitude of each busbar; Indicates the first The first busbar and the first Voltage phase angle difference between each busbar; and These represent the nth node admittance matrix. m,n Electrical conductivity and susceptance of elements; This indicates the number of buses participating in power flow calculation in the current TSO local network.

[0068] In the Newton-Raphson iteration, the power imbalance is constructed as follows: (11), And solve the corrected equation: (12) In equations (11) and (12), Represents the power imbalance vector; and Indicates the given active and reactive power; and This represents the active and reactive power calculated from the power flow equations. Represents the Jacobian matrix; This indicates the voltage phase angle correction amount; This indicates the voltage amplitude correction amount.

[0069] After each TSO completes the power flow calculation for its region, it sends the updated boundary bus information to the coordinator and its neighboring TSOs.

[0070] Step S33, Convergence Judgment and Iteration Variable Correction: Determine whether the voltage changes of all virtual boundary buses are less than the upper-level convergence tolerance. , define the first The boundary voltage residual of the next higher iteration is: (13) In equation (13), Indicates the first The maximum residual of the boundary voltage in the next higher iteration; Indicates the first The vector composed of all virtual boundary bus voltages after the next upper-level iteration; The infinite norm represents the maximum absolute value of all elements in a vector.

[0071] If the following conditions are met: (14) If the upper-layer multi-TSO distributed power flow calculation is deemed to have converged, the iteration is terminated, and the power flow results for the entire system are output.

[0072] Otherwise, after correcting the voltage amplitude of the virtual boundary bus using the results of the most recent historical iterations, return to step S31 to continue the next upper-level iteration.

[0073] The specific method for iterative variable correction is as follows: like If the value is even, the following correction is applied to the magnitude of the virtual boundary bus voltage: (15) In equation (15), Indicates the first The virtual boundary bus voltage magnitude vector after the next upper-level iteration; Indicates the first The virtual boundary bus voltage magnitude vector after the next upper-level iteration; Indicates the first The virtual boundary bus voltage magnitude vector after the next upper-level iteration; both the sum of squares and division represent element-wise calculations. This correction formula is equivalent to estimating the fixed-point location using the results of the three most recent iterations, thereby suppressing boundary voltage oscillations and improving convergence stability.

[0074] In practical engineering implementation, to avoid numerical instability caused by an excessively small denominator, a numerical stability threshold can be set. When a certain boundary bus satisfies: (16) At this time, the boundary busbar is not corrected using equation (15), but is updated using relaxation: (17) In equation (17), Indicates the first The virtual boundary busbar in the first The voltage amplitude of the next iteration; This represents the threshold value to prevent the denominator from being too small. This represents the relaxation factor, with a preferred value range of 0.5 to 0.9. This processing can further improve the numerical robustness under strongly coupled boundary scenarios.

[0075] The corrected virtual boundary bus voltage magnitude is used as the input for the equal value method calculation in the next upper-level iteration.

[0076] This completes all the steps of the two-layer power flow calculation method for multi-transmission and distribution power systems described in this embodiment.

[0077] Example 2: This embodiment provides a two-layer power flow calculation system for a multi-transmission and distribution power system, used to implement the two-layer power flow calculation method as described in Embodiment 1.

[0078] Example 3: like Figure 5 As shown, this embodiment provides an electronic device, which may include: at least one processor, at least one network interface, a user interface, a memory, and at least one communication bus.

[0079] The communication bus can be used to enable communication between the various components mentioned above.

[0080] The user interface may include buttons, and optional user interfaces may also include standard wired interfaces and wireless interfaces.

[0081] The network interface may include, but is not limited to, Bluetooth modules, NFC modules, Wi-Fi modules, etc.

[0082] The processor may include one or more processing cores. It connects various parts of the electronic device via various interfaces and lines, executing instructions, programs, code sets, or instruction sets stored in memory, and accessing data stored in memory to perform various functions and process data. Optionally, the processor can be implemented using at least one hardware form of DSP, FPGA, or PLA. The processor may integrate one or more of the following: CPU, GPU, and modem. The CPU primarily handles the operating system, user interface, and applications; the GPU is responsible for rendering and drawing the content required for display; and the modem handles wireless communication. It is understood that the modem may also be implemented as a separate chip without being integrated into the processor.

[0083] The memory may include RAM or ROM. Optionally, the memory may include a non-transitory computer-readable medium. The memory can be used to store instructions, programs, code, code sets, or instruction sets. The memory may include a program storage area and a data storage area, wherein the program storage area may store instructions for implementing an operating system, instructions for at least one function (such as touch function, sound playback function, image playback function, etc.), instructions for implementing the above-described method embodiments, etc.; the data storage area may store data involved in the above-described method embodiments, etc. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor. The memory, as a computer storage medium, may include an operating system, a network communication module, a user interface module, and computing applications. The processor can be used to call the computing applications stored in the memory and execute the steps of the two-layer power flow calculation method mentioned in the foregoing embodiments.

[0084] Example 4: This embodiment provides a computer-readable storage medium storing instructions that, when executed on a computer or processor, cause the computer or processor to perform the above-described instructions. Figure 1 One or more steps in the illustrated embodiment. If the constituent modules of the above-described electronic device are implemented as software functional units and sold or used as independent products, they can be stored in the computer-readable storage medium.

[0085] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this specification are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in or transmitted through a computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., Digital Versatile Discs (DVDs)), or semiconductor media (e.g., Solid State Disks (SSDs)).

[0086] Those skilled in the art will understand that all or part of the processes in the method of Embodiment 1 described above can be implemented by a computer program instructing related hardware. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks. Unless otherwise specified, the technical features of this embodiment and the implementation scheme can be combined arbitrarily.

[0087] Example 5: To verify the effectiveness of the two-layer power flow calculation method for multi-transmission and distribution power systems described in this specification, this embodiment constructs multiple integrated transmission and distribution test cases based on the IEEE standard test system to simulate and verify the proposed method.

[0088] The test program in this embodiment runs on a 64-bit Windows operating system, with an Intel Core i7-7700K CPU (4.20GHz), 32GB of memory, and MATLAB as the software programming environment. Power flow calculations within each TSO and DSO region employ the traditional single-phase Newton-Raphson method, using a flat start as the initial condition. The power flow calculation convergence tolerance is set to... pu.

[0089] The transmission network in this embodiment adopts the IEEE 30-node system and is divided into three transmission areas, each managed by a separate Transmission Station (TSO). The distribution network uses a modified IEEE 69-node system as the standard distribution network template. In this template, three distributed generation (DG) sources are connected at nodes 8, 15, and 20. All three DGs employ a control mode with given active power and voltage amplitude (PV control), with an active power output set at 0.5 MW and a voltage setpoint of 1.0 pu.

[0090] To verify the applicability of the method described in this specification to systems of different scales, the following three test cases were constructed: Example A is a medium-sized system, with three distribution networks connected to busbars 8, 19 and 30 of the transmission system, respectively.

[0091] Example B is a larger-scale system, in which five distribution networks are connected to busbars 8, 17, 19, 29 and 30 of the transmission system, respectively.

[0092] Example C is a large-scale system in which six distribution networks are connected to busbars 6, 8, 17, 19, 29 and 30 of the transmission system, respectively.

[0093] To comprehensively evaluate the performance of the methods described in this specification, the following five methods are set up for comparison: First, the centralized power flow calculation method, CPF. This method uses the traditional centralized Newton-Raphson method to calculate the power flow of the entire multi-TSO and multi-DSO system, requiring complete data for the entire system. Although this method is difficult to implement in practical multi-operator systems, its calculation results can serve as an accuracy benchmark.

[0094] Second, the traditional multi-region distributed power flow (DPF) method. This method treats different transmission and distribution networks as independent regions at the same level and uses an alternating iterative approach to coordinate power flow.

[0095] Third, the BLDPF-I algorithm is without improvement. This method adopts the two-layer architecture of this invention, but does not introduce iterative variable correction techniques or approximate lower-layer solution techniques.

[0096] Fourth, a partial improvement to the two-layer algorithm BLDPF-II. This method adopts the two-layer architecture of this invention and introduces iterative variable correction technology, but does not use the approximate lower-layer solution technology.

[0097] Fifth, the fully improved two-layer algorithm BLDPF-III. This method adopts the two-layer architecture of this invention and simultaneously introduces iterative variable correction technology and approximate lower-layer solution technology, which is the method described in this specification.

[0098] Taking example A as an example, the power flow calculation accuracy of each algorithm at the critical boundary bus is compared. The critical boundary bus includes the TSO-TSO boundary bus and the TSO-DSO connection point. Table 1 shows the voltage magnitude and phase angle results for some boundary buses.

[0099] Table 1:

[0100] As shown in Table 1, when convergence is achieved, the voltage magnitude and phase angle results of DPF, BLDPF-II, and BLDPF-III at the critical boundary bus are consistent with those of the centralized power flow CPF, indicating that the two-layer distributed power flow algorithm described in this specification can achieve the accuracy of centralized power flow calculation after convergence. The divergence of BLDPF-I indicates that simply using a two-layer structure without introducing convergence improvement techniques is insufficient to guarantee stable convergence of a strongly coupled system with multiple TSOs and multiple DSOs.

[0101] Furthermore, examples A, B, and C were used to test the convergence and computational efficiency of different algorithms. Table 2 shows the computation time and number of iterations for each algorithm.

[0102] Table 2:

[0103] In Table 2, the data in parentheses represents the number of upper-level iterations / the total number of lower-level iterations. For the traditional single-layer DPF method, example A converges, but diverges in examples B and C, indicating that as the system scale increases and boundary coupling strengthens, treating the transmission and distribution networks as the same level for distributed power flow calculation is insufficient to guarantee convergence. BLDPF-I diverges in all three examples, indicating that the two-layer structure itself is insufficient to guarantee convergence, and boundary variable correction measures must be introduced.

[0104] BLDPF-II converged in all three examples, demonstrating that the iterative variable correction technique plays a crucial role in ensuring the overall convergence of the two-layer distributed power flow algorithm described in this specification. Compared to BLDPF-II, BLDPF-III further reduces computation time and the number of lower-level iterations in all three examples by introducing an approximate lower-level solution technique. Particularly in example A, the computation time of BLDPF-III decreased from 1.44s in BLDPF-II to 0.54s, a reduction of over 50%. This indicates that the approximate lower-level solution technique can significantly improve computational efficiency while maintaining final computational accuracy.

[0105] Regarding the setting of the approximate lower-level solution parameter t, the coupling between the transmission network and the distribution network is relatively weak in example A, therefore, we take... A better approximate lower-level solution can be obtained; in examples B and C, there are more distribution networks connected and the transmission and distribution coupling is stronger, therefore, we take... This is to improve the reliability of the lower-level approximate solution in the early stages of the upper-level iteration.

[0106] like Figure 6 As shown, taking Example A as an example, the curves of the boundary voltage residuals of three convergence algorithms—DPF, BLDPF-II, and BLDPF-III—as a function of the number of iterations are plotted. It can be observed that BLDPF-III, due to its approximate lower-level solution in the early stages of the upper-level iterations, exhibits some fluctuations in its residual curve initially. However, as the upper-level boundary voltage gradually approaches the final solution, the algorithm quickly enters a stable descent phase and ultimately converges with the least computation time. This demonstrates that the approximate lower-level solution technique can effectively improve the computational efficiency of two-layer distributed power flow by appropriately reducing the accuracy of the lower-level solution in the early stages and restoring the accurate solution in the later stages.

[0107] In summary, this embodiment verifies the effectiveness and superiority of the two-layer power flow calculation method for multi-transmission and distribution power systems described in this specification in multi-TSO and multi-DSO integrated transmission and distribution systems.

[0108] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0109] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0110] The foregoing description is merely an exemplary embodiment of the present invention and should not be construed as limiting the scope of the invention. Any equivalent changes and modifications made in accordance with the teachings of this invention are still within the scope of this invention. Those skilled in the art will readily conceive of embodiments of the invention upon considering the specification and practicing the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include knowledge or means in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of the invention are defined by the claims.

Claims

1. A two-layer power flow calculation method for a multi-transmission and distribution power system, characterized in that, The multi-transmission and distribution power system includes multiple transmission system operators (TSOs) and multiple distribution system operators (DSOs), and the method includes the following steps: S1. Divide the multi-transmission and distribution power system into multiple transmission areas managed by TSO and multiple distribution areas managed by DSO, and connect each TSO area to at least one DSO area. S2. Set up virtual boundary buses at the boundary of tie lines between different TSO regions, determine the master TSO and slave TSO to unify the voltage phase angle reference of the whole system, set the type of each virtual boundary bus according to the master-slave relationship, establish the local node admittance matrix of each region, initialize the bus state variables, and set the upper-level convergence tolerance and lower-level convergence tolerance. S3. Repeat the upper-level iteration until the voltage changes of all virtual boundary buses are less than the upper-level convergence tolerance. The upper-level iteration includes: S31. Each TSO region performs its own power flow calculation for the transmission network. During the execution, the current TSO region and its subordinate DSO regions alternately exchange the root node voltage and the root node equivalent power until the change in root node voltage and power is less than the lower-level convergence tolerance. If this upper-level iteration is the first execution, or the boundary voltage change in the previous upper-level iteration is not less than the upper-level convergence tolerance, the alternation exchange is only performed for a finite number of approximate iterations; otherwise, it is executed until full convergence. S32. After completing the lower-level convergence in step S31, each TSO region uses the equivalent method to convert the external network into equivalent power injection and equivalent admittance at the virtual boundary bus. Combined with the equivalent power injection of the subordinate DSO obtained in the lower-level iteration in S31, the power flow of the transmission network in this region is solved independently. Among them, the external network of the main TSO region is its adjacent slave TSO region, and the external network of the slave TSO region is the main TSO region or the adjacent slave TSO region that has been determined for reference. S33. Determine whether the voltage change of all virtual boundary buses is less than the upper-level convergence tolerance. If so, terminate the iteration; otherwise, after correcting the voltage amplitude of the virtual boundary buses using the results of the most recent historical iterations, return to step S31 to continue the next upper-level iteration.

2. The two-layer power flow calculation method according to claim 1, characterized in that, Step S33 involves correcting the magnitude of the virtual boundary bus voltage, specifically as follows: After an even number of iterations in the upper-level iteration, the location of the fixed point is estimated using the voltage amplitude results of the virtual boundary bus in the three most recent upper-level iterations, and this is used as the corrected voltage amplitude.

3. The two-layer power flow calculation method according to claim 2, characterized in that: When the second-order change of the voltage amplitude of a certain virtual boundary bus in three consecutive upper-level iterations is less than the preset numerical stability threshold, the voltage amplitude is updated using a relaxation factor. The relaxation factor ranges from 0.5 to 0.

9.

4. The two-layer power flow calculation method according to claim 1, characterized in that, The number of approximate iterations in step S31 is determined based on the sensitivity of the subordinate DSO region to changes in the root node voltage: The sensitivity index is determined by comparing the ratio of the change in root node power to the change in root node voltage in two adjacent lower-level iterations within the subordinate DSO region. When the sensitivity index is less than the preset sensitivity threshold, the number of times is taken as a smaller value; when the sensitivity index is greater than or equal to the preset sensitivity threshold, the number of times is taken as a larger value. The number of times ranges from 1 to 3.

5. The two-layer power flow calculation method according to claim 1, characterized in that, In step S2, the type of each virtual boundary bus is set according to the master-slave relationship, specifically as follows: The virtual boundary bus of the main TSO region is set to be updated by power flow calculation with voltage magnitude and phase angle, and active power and reactive power as known quantities. For a slave TSO region directly connected to the main TSO region, one virtual boundary bus connected to the main TSO region can be selected as the local balancing node of the slave TSO region. The remaining virtual boundary buses in the slave TSO region are set to the type where the voltage amplitude is given, the active power is given, and the reactive power is determined by power flow calculation. For a slave TSO region that is not directly connected to the main TSO region, an adjacent slave TSO region with a determined local balancing node is selected as a reference region, and a virtual boundary bus between the slave TSO region and the reference region is selected as the local balancing node of the slave TSO region. The remaining virtual boundary buses of the slave TSO region are set to the type where the voltage amplitude is given, the active power is given, and the reactive power is determined by power flow calculation.

6. The two-layer power flow calculation method according to claim 1, characterized in that, In step S2: The initial equivalent power injection of the root node of each DSO area is obtained by calculating the initial power flow of the distribution network, or is taken as the estimated net load of the distribution network corresponding to the DSO area. The bus status variables are initialized using a flat start method.

7. The two-layer power flow calculation method according to claim 1, characterized in that: In step S32, the information exchanged between adjacent TSO regions is the virtual boundary bus voltage and power information.

8. A two-layer power flow calculation system for a multi-transmission and distribution power system, characterized in that, Used to implement the two-layer power flow calculation method as described in any one of claims 1 to 7.

9. An electronic device, the electronic device comprising a memory, a processor, and a computer program, characterized in that, When the computer program is executed by the processor, it implements the two-layer power flow calculation method as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the two-layer power flow calculation method as described in any one of claims 1 to 7.

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