Power distribution network security domain evaluation method and system considering double-end tie-in backup

Abstract

The application belongs to the technical field of safe operation analysis of power distribution system, and particularly discloses a power distribution network safety domain evaluation method and system considering double-end tie-in backup, which comprises the following steps: constructing a power distribution network model containing distributed power supply and energy storage system under double-end tie-in, performing linear extrapolation on the safety boundary distance searched by the first two rays to predict the safety boundary distance of the current ray; constructing an adaptive reduced search interval; if the safety check is passed, performing standard dichotomy search in the adaptive reduced search interval to finally locate the safety domain boundary point in the direction of the current ray; calculating the discrete curvature of each safety domain boundary point and the chord-length-curvature error between two adjacent boundary points to determine whether local encryption is triggered; and performing safety domain boundary search on the encrypted curve again to obtain the final power distribution network safety domain. The application can maintain search robustness when boundary prediction fails through endpoint safety check and full-interval back-off mechanism.

Description

Technical Field

[0001] This invention relates to the field of power distribution system safety operation analysis technology, and in particular to a method and system for evaluating the safety domain of a power distribution network that takes into account dual-end interconnection backup. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] The large-scale integration of distributed power sources and energy storage systems with a high proportion of distributed generation has transformed traditional distribution networks into active networks, making power flow distribution and post-fault recovery methods more complex. The distribution system security region (DSSR), as the boundary of the maximum load space that the system can withstand while meeting all safety constraints such as voltage and thermal stability, has become an important tool for the scientific planning and flexible scheduling of distribution networks.

[0004] In the assessment of the security domain, it is necessary to verify the reconfiguration carrying capacity of the power grid under source-storage coordination in the N-1 fault scenario set. However, existing methods for characterizing the security domain boundary of distribution networks mostly employ equal-angle ray scanning and full-range binary search. These methods do not fully utilize the continuity between the distances of adjacent ray boundaries, resulting in a large amount of redundant power flow calculations in scenarios where the computational workload of N-1 reconfiguration verification is large. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a method and system for evaluating the security domain of a distribution network that takes into account dual-terminal interconnection backup. Based on the initial screening of the security domain boundary using neighborhood prediction, combined with curvature-adaptive ray densification scanning, the method achieves accurate characterization of the security domain of the distribution network under dual-terminal interconnection backup.

[0006] In some implementations, the following technical solutions are adopted: A method for assessing the security domain of a distribution network that takes into account dual-end interconnection backup includes: A distribution network model with distributed power sources and energy storage systems under dual-terminal interconnection is constructed, and the power grid operation safety judgment criteria are defined, and an N-1 dynamic fault set is constructed. Define a load scanning direction vector. In the two-dimensional feeder load space, perform a ray scan starting from the origin. Use the safety boundary distances found by the first two rays to perform linear extrapolation to predict the safety boundary distance of the current ray. Construct an adaptively reduced search interval based on the safety boundary distance. Safety verification is performed on the load scan points within the adaptively reduced search interval. If the verification passes, a standard binary search is performed within the adaptively reduced search interval to finally locate the safety domain boundary point in the current ray direction. Calculate the discrete curvature of each security domain boundary point and the chord length-curvature error between two adjacent boundary points to determine whether local encryption is triggered; re-search the security domain boundaries on the encryption curve to obtain the final distribution network security domain.

[0007] As a further option, it also includes: Energy storage is considered as a short-term power support resource during N-1 fault reconfiguration. The actual available discharge power is calculated and incorporated into the node power equation to participate in power flow calculation, thereby expanding the branch capacity margin and node voltage margin. Repeat the aforementioned distribution network security domain assessment method to obtain the N-1 security domain boundary point set of the distribution network under source-storage synergy.

[0008] As a further solution, the N-1 dynamic fault set includes main transformer branch faults and feeder faults; according to the fault type, the corresponding set of reconfiguration actions is invoked, and the actions include closing normally open tie switches and opening preset normally closed sectionalizing switches.

[0009] As a further solution, a load scan direction vector is defined as follows: ; in, The angle of the scanning ray; Along the scanning ray, the load operating point is specifically as follows: ; in, The distance of the ray represents the load level along that direction.

[0010] As a further approach, the safe boundary distance of the current ray is predicted by linear extrapolation using the safe boundary distances found from the first two rays, specifically: ; in, , Let represent the known boundary distances of the preceding and two preceding rays of the m-th ray, respectively. , , Let represent the angles of the m-th ray and the ray preceding it, and the ray two rays preceding it.

[0011] As a further solution, an adaptively reduced search interval is constructed based on the aforementioned safety boundary distance, specifically as follows: Calculate the adaptive neighborhood width of the current ray. : ; An adaptively reduced search interval is constructed based on the aforementioned safety boundary distance and adaptive neighborhood width: ; in, For safety reasons, Minimum neighborhood width, This indicates the upper limit of the search radius.

[0012] As a further measure, a safety check is performed on the load scan points within the adaptively reduced search interval, specifically including: Power flow calculations are performed on the topology at the load scan point to obtain the equivalent injected power of the nodes; Within the operating point of the scan, check whether the capacity constraints of the feeder and main transformer are met. After the capacity constraint is passed, solve the complete set of AC power flow equations to determine whether the voltage of all nodes in the network is within the allowable range. After the above security checks pass, security checks are performed on the endpoints of the adaptively reduced search interval. If the checks fail, the system falls back to the global search interval and performs a standard binary search.

[0013] As a further solution, local encryption is triggered when the following conditions are met: If the discrete curvature of a boundary point in the safety domain exceeds a set threshold, the chord length-curvature error between adjacent boundary points exceeds a preset error tolerance, or the concavity / convexity sign is flipped, a new scanning ray is inserted between the two adjacent boundary points.

[0014] In other embodiments, the following technical solutions are adopted: A distribution network security domain assessment system that takes into account dual-end interconnection backup includes: The safety configuration module is used to construct a distribution network model with distributed power sources and energy storage systems under dual-terminal interconnection, define the safety judgment criteria for grid operation, and construct an N-1 dynamic fault set. The interval coarse scan module is used to define the load scanning direction vector. In the two-dimensional feeder load space, a ray scan is performed starting from the coordinate origin. The safe boundary distance of the current ray is predicted by linear extrapolation using the safe boundary distances found by the first two rays. An adaptive shrinking search interval is constructed based on the safe boundary distance. The safety verification module is used to verify the safety of the load scan points within the adaptive shrinking search interval. If the verification passes, a standard binary search is performed within the adaptive shrinking search interval to finally locate the safety domain boundary point in the current ray direction. The curve encryption module is used to calculate the discrete curvature of each security domain boundary point and the chord length-curvature error between two adjacent boundary points, and to determine whether local encryption is triggered; the encryption curve is re-searched for security domain boundaries to obtain the final distribution network security domain.

[0015] In other embodiments, the following technical solutions are adopted: A terminal device includes a processor and a memory, the processor being used to implement instructions; the memory being used to store multiple instructions, the instructions being adapted to be loaded and executed by the processor to perform the above-described distribution network security domain assessment method considering dual-end interconnection backup.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention leverages the continuity of distances between adjacent ray boundaries to reduce the traditional global search interval to a local neighborhood around the predicted boundary distance on most rays, thereby reducing the number of repeated binary searches and safety checks. Through endpoint safety checks and a full-range backoff mechanism, search robustness can be maintained even when boundary prediction fails.

[0017] This invention utilizes discrete curvature, chord length-curvature error, and concavity / convexity sign reversal to identify complex boundary regions, enabling the rays to be automatically densified in regions with high curvature, concavity, or large boundary errors, thereby maintaining a low sampling density in regions with gentle boundaries and avoiding redundant calculations caused by global uniform densification.

[0018] In its implementation, this invention achieves a two-dimensional characterization of the safety domain of a double-ended interconnected feeder under the dual constraints of grid voltage and feeder capacity, which can provide support for the planning, operation and scheduling of double-ended interconnected distribution networks containing distributed power sources and energy storage.

[0019] Other features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] Figure 1 This is a flowchart of the distribution network security domain assessment method considering dual-end interconnection backup in an embodiment of the present invention; Figure 2 This is a schematic diagram of the initial screening scanning process of the security domain boundary based on neighborhood prediction in an embodiment of the present invention; Figure 3 This is a schematic diagram of the curvature adaptive ray encryption scanning process in an embodiment of the present invention; Figure 4 This is a schematic diagram of the dual-end interconnection topology of the distribution network dual-end interconnection backup and distributed source-storage access in an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the security domain characterization results of adaptive ray scanning under dual-end communication in an embodiment of the present invention. Detailed Implementation

[0021] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Example 1 In one or more embodiments, a distribution network security domain assessment method considering dual-end interconnection backup is disclosed, combined with Figure 1 Specifically, it includes the following processes: S101: Construct a distribution network model with distributed power sources and energy storage systems under dual-terminal interconnection, define the power grid operation safety judgment criteria, and construct an N-1 dynamic fault set; This embodiment uses Figure 4 The diagram illustrates a distribution network containing double-ended interconnecting feeders, distributed generation (DG), and energy storage, and characterizes the reconfiguration security domain under a preset N-1 fault scenario set. As an example, the system includes three feeders F1, F2, and F3, where F2 is the intermediate interconnecting feeder. A first normally open interconnecting switch connects F1 and F2, and a second normally open interconnecting switch connects F2 and F3. A normally closed sectionalizing switch is located in the middle of F2. F1 and F3 are connected to distributed generation (DG) and energy storage (ESS), respectively. DG and ESS are located at the interconnecting ends or key nodes of the feeders to provide power support during fault transfer.

[0024] Establish a distribution network model that includes equivalent main grid power sources, main transformer branches, main transformer low-voltage side bus tie switches, feeders F1, F2, F3, normally open tie switches between feeders, normally closed sectionalizing switches, distributed generation (DG), and energy storage system (ESS).

[0025] Set up the distribution network operation point Composed of the apparent power of each feeder node: (1) , , These represent the apparent power, active power, and reactive power of node i, respectively.

[0026] Operating point under normal operating conditions of all components The following constraints must be satisfied simultaneously: (2) Among them, the node voltage amplitude is branch road Apparent power The corresponding capacity limits are as follows: , , .

[0027] remember This represents the N-0 safety judgment constraint, where all constraints are satisfied. ,otherwise .

[0028] Define the N-1 safety criterion: for the fault set Failure of any single component There exists a set of interconnection switch closing schemes. This ensures that after fault removal and network reconstruction, all non-faulty nodes satisfy the same constraint as equation (2). That is: (3) in, Let be an indicator function. This represents N-1 safety discrimination constraints, where all constraints are satisfied. ,otherwise .

[0029] In this embodiment, the N-1 security domain of the distribution network is defined as follows: (4) in, This is the state space.

[0030] Fault set composition: (5) in, This is a fault set for normally closed main branch circuits.

[0031] This embodiment integrates multiple constraints (voltage constraint, capacity constraint, N-1 reconfiguration feasibility) into a single discriminant function. This provides a consistent and calculable evaluation standard for the safety verification of all subsequent load points, avoiding the uncertainty of manual item-by-item verification.

[0032] In this embodiment, an N-1 dynamic fault set is constructed. The fault set includes faults in the main transformer branch and faults in the feeder. Based on the fault type, the corresponding set of reconfiguration actions is invoked, including closing normally open tie switches and opening preset normally closed sectionalizing switches.

[0033] Specifically, based on the two-way interconnection topology of the distribution network, the fault set is divided into the following three categories: (1) Main transformer branch fault: When the main transformer fails, the load of the faulty main transformer is transferred to the adjacent main transformer by closing the low-voltage side bus tie switch of the main transformer. (2) Normal feeder fault: When a feeder fault occurs, the load of the faulty feeder is transferred to the adjacent feeder by closing the normally open interconnection switch between feeders; (3) Sectional fault of the connecting feeder with sectional switch: For the intermediate connecting feeder F2, when a fault occurs at its root or upper section, open the normally closed sectional switch in the middle of F2, and at the same time close the first and second normally open connecting switches at both ends of F2, so that the load of the upper section of F2 is transferred to F1 and the load of the lower section of F2 is transferred to F3, so as to realize the simultaneous transfer of power at both ends.

[0034] This embodiment addresses the unique structure of double-ended interconnected topologies by classifying fault scenarios and pre-setting corresponding reconfiguration actions for each type of fault, thus avoiding the computational overhead of real-time reconfiguration solution calculation after a fault occurs. In particular, it employs specialized modeling for interconnected feeders containing sectionalizing switches to accurately capture the backup capacity of simultaneous power transfer at both ends, enabling the fault set to more comprehensively reflect the actual operating characteristics of the double-ended interconnected distribution network.

[0035] S102: Define the load scanning direction vector. In the two-dimensional feeder load space, perform ray scanning starting from the origin of the coordinate system. Use the safety boundary distances found by the first two rays to perform linear extrapolation to predict the safety boundary distance of the current ray. Construct an adaptively reduced search interval based on the safety boundary distance.

[0036] In this embodiment, combined with Figure 2 Distribution network safety domain (DSSR) in two-dimensional feeder load space The region in question is a bounded closed region. To characterize the boundary of the safety region in a two-dimensional plane, the load scan direction vectors of feeders F1 and F5 are defined. .

[0037] (6) Along this ray, the load operating point can be represented as : (7) All load conditions constitute a state space in a two-dimensional plane. For a given angle Due to the increased load, the safety margin decreases, and a critical value exists. Make the running point satisfy: (8) in, For angle Boundary distance in the direction.

[0038] The desired security domain is one that satisfies the N-1 criterion for distribution networks. That is, the set of operating points within the N-1 safety domain of the distribution network.

[0039] The security domain boundary is the set of all boundary points: (9) The boundary of the safe region is a continuous curve, therefore the boundary distance function It has Lipschitz continuity and satisfies: (10) in, It is the Lipschitz constant, which depends on the maximum rate of change of the boundary. Indicates the angle of the m-th ray Boundary distance in the direction, This represents the boundary distance along the direction of the (m-1)th ray.

[0040] Although the initial screening involves discrete angle scanning, the boundary distance between adjacent rays is continuous to a certain extent, and the result of the previous ray can be used as a reference initial value for the next ray.

[0041] The first ray at the angle A blind search is performed, and the first boundary point is obtained by approximation using the full interval bisection method. . use The shrinking interval is constructed, and its adaptive neighborhood width is calculated as follows: (11) in, For safety, a conservative estimate is used to ensure that the true boundary is covered. To minimize the neighborhood width, preventing the interval from approaching 0 when the boundary distance is small; It represents the angular difference between two adjacent rays.

[0042] According to the adaptive neighborhood width calculation, the farther away from the origin and the larger the angle step size, the greater the possible offset of the boundary. At the same time, the addition term ensures that the search interval will not be too narrow.

[0043] At this point, the reduced interval is: (12) in, To reduce the left endpoint of the search interval, To reduce the right endpoint of the search interval, Let be the adaptive neighborhood half-width of the m-th ray.

[0044] The first two rays were used to search for the safe boundary distance. and From the third ray onwards, according to , The distance to the next predicted boundary can be obtained by linear extrapolation using the local trend of the boundary. : (13) Its essence is to exist Perform a first-order Taylor expansion: (14) (15) Since the estimates obtained by linear extrapolation are highly accurate, the neighborhood width can be appropriately reduced. (16) The search range at this point is: (17) This embodiment transforms the high-dimensional distribution network security domain assessment problem into a boundary search problem in a two-dimensional load space. By using ray parameterization, the boundary search is decomposed into several independent one-dimensional bipartite problems, which significantly reduces the problem-solving complexity.

[0045] Using the security region boundary distance function The Lipschitz continuity, through linear extrapolation, extends the search interval from the global [0, Reducing the number of binary search iterations to the local neighborhood near the predicted value can significantly reduce the number of power flow calculation calls and improve overall computational efficiency on most rays.

[0046] S103: Perform a safety check on the load scan points within the adaptive shrinking search interval. If the check passes, perform a standard binary search within the adaptive shrinking search interval to finally locate the safety domain boundary point in the current ray direction.

[0047] Specifically, before performing power flow calculations on a candidate load point, power flow calculations are performed on the topology at the scanned working points. Nodes The formula for calculating the equivalent injected power is shown in equation (18).

[0048] (18) in, , The equivalent injected power represents the total power requirement of the i-th node. , Represents basic electrical load. , Represents the output of distributed power sources. , This represents the output of the energy storage system.

[0049] Then determine whether the main transformer and feeder are overloaded; that is, within the scanned operating point, check whether the capacity constraints of the feeder and main transformer are met.

[0050] For the main transformer, the apparent power it bears The estimate is: (19) in, and These represent the active power and reactive power of the k-th feeder on the transformer, respectively.

[0051] After the capacity constraints are met, solve the complete set of AC power flow equations: (20) in, This represents the active power imbalance at node i. Represents the reactive power imbalance at node i. The voltage amplitude at node i, The voltage amplitude at node j, , The real and imaginary parts of the element in the i-th row and j-th column of the nodal admittance matrix are respectively. This represents the voltage phase angle difference between nodes i and j.

[0052] If and only if the above nonlinear equations converge, and the voltages of all network nodes satisfy... Apparent power of all branches When, satisfy ;otherwise, .

[0053] It should be noted that load scan points are all scannable operating points in two-dimensional space; operating points are the current operating conditions of the loads carried by each feeder and the output of distributed power sources and energy storage at the current time segment; nodes are nodes in the topology and also nodes in power flow calculations. At each operating point, power flow calculations are performed on the topology to obtain the power status of each node in the topology.

[0054] This embodiment uniformly converts the impact of various power sources and loads in the distribution network into equivalent injected power at nodes, providing standardized input for subsequent power flow calculations. This avoids the modeling complexity caused by handling various resources separately in the power flow equations, while also enabling the power contributions of DG and ESS to naturally participate in safety verification.

[0055] Capacity constraints serve as a rapid pre-screening step in safety verification, filtering out obviously unsafe operating points in advance with extremely low computational cost. This avoids performing AC power flow calculations on these points, which have a much higher computational cost than capacity verification, thereby reducing the overall number of power flow calculation calls and further improving algorithm efficiency.

[0056] After the above security checks pass, the adaptive shrinking interval is... Endpoint security verification; the validity of the reduced interval is contingent upon the left endpoint. At safety, right end point The premise is not valid if the forecast is inaccurate. In this case, a rollback is performed according to the rollback criteria. That is: (twenty one) This backoff mechanism ensures the robustness of the algorithm. Even if the neighborhood propagation prediction is wrong, the worst case will only degenerate into the traditional full-interval binary search, without producing erroneous results.

[0057] If adaptively shrinking interval If the endpoint verification is successful, then a valid binary search is performed within the reduced search interval. Determine the valid search interval. Then, perform a standard binary search. If in If the system can withstand all single failures, then update the lower bound of the binary search method. Otherwise, update the upper limit. Until the interval difference meets the tolerance. Output the boundary distance of the final boundary running point. This represents the midpoint exploration distance during the binary search process.

[0058] This embodiment ensures the robustness of the algorithm when neighborhood prediction fails through an endpoint verification mechanism that requires only two additional security checks. Regardless of abrupt boundary changes, severe prediction deviations, or other anomalies, the worst-case scenario only degenerates into a traditional full-interval binary search, without producing erroneous boundary distance results, thus ensuring the correctness and reliability of the algorithm in any scenario.

[0059] S104: Calculate the discrete curvature of each security domain boundary point and the chord length-curvature error between two adjacent boundary points to determine whether local encryption is triggered; re-search the security domain boundaries of the encryption curve to obtain the final distribution network security domain.

[0060] In this embodiment, combined with Figure 3 Coarse scanning yields ordered boundary points. back, This represents the total number of boundary points obtained from the coarse scan. For each boundary point... Discrete curvature is calculated based on the circumcircle method; the specific process is as follows: Define adjacent vectors : (twenty two) Adjacent vectors can be represented in scalar form as: (twenty three) Concavity and convexity are represented by their scalar notation: (twenty four) The discrete Menger curvature is calculated to obtain: (25) in, Let j be the coordinates of the boundary point. For the (j-1)th boundary point, For the (j+1)th boundary point, , They are respectively The x and y components, , They are respectively represented as The x and y components.

[0061] A higher curvature indicates more severe boundary bending, requiring a higher sampling density.

[0062] The upper bound of the chord length-curvature error between adjacent boundary points is calculated as follows: Two adjacent boundary points The length of the chord is: (26) The upper bound of the error is calculated based on the chord length-curvature relationship between the two points: (27) in, The larger value of the curvature at both ends .

[0063] Encryption is triggered when the following conditions are met for adjacent boundary points: (28) The above formula indicates that when the discrete curvature of the boundary points of the safety region exceeds a set threshold... Or the chord length-curvature error between adjacent boundary points exceeds the preset error tolerance. In other words, when capturing areas with severe boundary curvature, near inflection points, or where excessively long chords lead to excessive linear approximation errors, a new scanning ray is inserted between two adjacent boundary points.

[0064] Alternatively, if the concavity / convexity sign is flipped, it is determined that there may be a concavity / convexity switch or a boundary concavity / entrance in the interval, and a new scanning ray is inserted between two adjacent boundary points.

[0065] In the area marked as encrypted Insert new rays in the center Specifically: (29) The boundary distance search for the new ray uses the mean of the known results on both sides as the prediction center. : (30) (31) To prevent infinite recursive encryption, a lower limit rule for angle resolution is set: (32) Repeat steps S102 to S103 to obtain new boundary points, and re-evaluate whether to continue encryption until the angle interval meets the lower limit rule.

[0066] This embodiment employs a curvature-driven adaptive encryption mechanism to comprehensively evaluate boundary characterization quality from three dimensions: curvature magnitude, approximation error, and concavity / convexity variation. This achieves an intelligent sampling strategy of "encryption on demand": automatically increasing sampling density in areas with severe boundary curvature, inflection points, or local depressions to ensure no boundary details are missed; and maintaining sparse sampling in areas with gentle boundaries to avoid redundant computation. Compared to globally uniform encryption, this method significantly reduces the total number of rays and power flow calculations while maintaining the same characterization accuracy.

[0067] As a further implementation, the ESS is considered as a short-term power support resource during N-1 fault reconfiguration, taking into account rated power, state of charge (SOC), and energy storage capacity. Discharge efficiency and duration of support Constraints, calculate the actual usable discharge power : (33) To avoid the State of Charge (SOC) falling below the lower limit, the actual usable discharge power is: (34) From the perspective of apparent power constraints, the branch capacity constraint is: (35) in, The current state of charge of the energy storage system, The lower limit of the permissible state of charge, For the power factor of the energy storage system, , , , These represent the apparent power, active power, reactive power, and rated capacity limit flowing through the l-th branch, respectively.

[0068] After joining ESS: (36) The capacity margin is: (37) (38) If the ESS injection direction is opposite to the original load flow direction, then: (39) That is, the capacity margin increases. (40) in, This refers to the apparent power flowing through the l-th branch after the ESS is connected. , These represent the changes in active power and reactive power of the l-th branch caused by the connection of the ESS, respectively. , These represent the capacity margin of the l-th branch without an ESS and the capacity margin of the l-th branch after an ESS is connected, respectively.

[0069] ESS reduces the equivalent load and branch power flow at the connection point and along the path, increasing branch capacity margin. At the same time, ESS injects active and reactive power at the connection point, reduces voltage drop in the transfer path, and improves the voltage margin at the end, thereby expanding the load area that meets voltage constraints.

[0070] Repeat the aforementioned security domain boundary point scanning process to obtain the N-1 security domain boundary point set of the distribution network under source-storage coordination.

[0071] To verify the distribution network security domain assessment method proposed in this embodiment, which considers source-storage coordination and dual-terminal interconnection backup, a distribution network containing dual-terminal interconnection feeders, distributed power sources, and energy storage is used as the object. The reconfiguration security domain under a preset N-1 fault scenario set is characterized. Combined with... Figure 4 The system includes three feeders F1, F2, and F3, with F2 serving as the intermediate interconnecting feeder. A first normally open interconnecting switch connects F1 and F2, and a second normally open interconnecting switch connects F2 and F3. A normally closed sectionalizing switch is located in the middle of F2. F1 and F3 are connected to distributed power sources and energy storage, respectively. In this embodiment, for any point in the two-dimensional load space, the system sequentially performs a ground-state power flow verification and a reconstruction verification under a preset N-1 fault scenario. If the network constraints such as power flow convergence, node voltage constraints, and branch capacity constraints are satisfied under both the ground-state and all preset fault scenarios, the point is determined to be a safe point; otherwise, it is determined to be an unsafe point.

[0072] The preset N-1 fault scenarios include main transformer faults and feeder faults. In the event of a main transformer fault, the power supply is transferred using the low-voltage side bus tie switch of the main transformer; in the event of a feeder fault, the power supply is transferred using the normally open tie switch between feeders; for a fault in the upper section of F7 equipped with a sectionalizing switch, the normally closed sectionalizing switch in the middle of F7 is opened, and the feeder tie switches on both sides are closed at the same time.

[0073] Figure 5 A schematic diagram of the safe region characterization results under adaptive ray scanning with two-end connections is presented. It can be seen that the safe region boundary is not simply formed by uniform rays, but exhibits significant density differences across different angle intervals. In regions with gentle boundaries, only a small number of initial scan rays are retained. However, in regions with large curvature changes, boundary inflections, or local contractions, the algorithm can automatically insert new scan rays based on discrete curvature, concavity / convexity indices, and chord-curvature error, thereby achieving local densification of complex boundary regions. Simultaneously, the neighborhood prediction interval reduction bisection method utilizes the continuity of the distance between adjacent ray boundaries to limit the search range of subsequent rays to the vicinity of the prediction boundary. It only reverts to a full interval search when the endpoint safety judgment fails, avoiding the redundant search caused by traditional equal-interval full-interval bisection.

[0074] Example 2 In one or more embodiments, a distribution network security domain assessment system considering dual-end interconnection backup is disclosed, specifically including: The safety configuration module is used to construct a distribution network model with distributed power sources and energy storage systems under dual-terminal interconnection, define the safety judgment criteria for grid operation, and construct an N-1 dynamic fault set. The interval coarse scan module is used to define the load scanning direction vector. In the two-dimensional feeder load space, a ray scan is performed starting from the coordinate origin. The safe boundary distance of the current ray is predicted by linear extrapolation using the safe boundary distances found by the first two rays. An adaptive shrinking search interval is constructed based on the safe boundary distance. The safety verification module is used to verify the safety of the load scan points within the adaptive shrinking search interval. If the verification passes, a standard binary search is performed within the adaptive shrinking search interval to finally locate the safety domain boundary point in the current ray direction. The curve encryption module is used to calculate the discrete curvature of each security domain boundary point and the chord length-curvature error between two adjacent boundary points, and to determine whether local encryption is triggered; the encryption curve is re-searched for security domain boundaries to obtain the final distribution network security domain.

[0075] It should be noted that the specific implementation methods of the above modules are exactly the same as those in Example 1, and will not be described in detail again.

[0076] Example 3 In one or more embodiments, a terminal device is disclosed, comprising a processor and a memory, wherein the processor is used to implement instructions; and the memory is used to store multiple instructions adapted to be loaded by the processor and executed by the processor to perform the distribution network security domain assessment method considering dual-end interconnection backup as described in Embodiment 1.

[0077] It should be understood that in this embodiment, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.

[0078] Memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory may also include non-volatile random access memory. For example, memory may also store information about the device type.

[0079] In the implementation process, each step of the above method can be completed by the integrated logic circuits in the processor hardware or by software instructions.

[0080] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for assessing the security domain of a distribution network considering dual-end interconnection backup, characterized in that, include: A distribution network model with distributed power sources and energy storage systems under dual-terminal interconnection is constructed, and the power grid operation safety judgment criteria are defined, and an N-1 dynamic fault set is constructed. Define a load scanning direction vector. In the two-dimensional feeder load space, perform a ray scan starting from the origin. Use the safety boundary distances found by the first two rays to perform linear extrapolation to predict the safety boundary distance of the current ray. Construct an adaptively reduced search interval based on the safety boundary distance. Safety verification is performed on the load scan points within the adaptively reduced search interval. If the verification passes, a standard binary search is performed within the adaptively reduced search interval to finally locate the safety domain boundary point in the current ray direction. Calculate the discrete curvature of each security domain boundary point and the chord length-curvature error between two adjacent boundary points to determine whether local encryption is triggered. The security domain boundary search is performed again on the encryption curve to obtain the final distribution network security domain.

2. The distribution network security domain assessment method considering dual-end interconnection backup as described in claim 1, characterized in that, Also includes: Energy storage is considered as a short-term power support resource during N-1 fault reconfiguration. The actual available discharge power is calculated and incorporated into the node power equation to participate in power flow calculation, thereby expanding the branch capacity margin and node voltage margin. Repeat the distribution network security domain assessment method in claim 1 to obtain the N-1 security domain boundary point set of the distribution network under source-storage synergy.

3. The distribution network security domain assessment method considering dual-end interconnection backup as described in claim 1, characterized in that, The N-1 dynamic fault set includes main transformer branch faults and feeder faults; the corresponding set of reconfiguration actions is called according to the fault type, and the actions include closing the normally open tie switch and opening the preset normally closed sectionalizing switch.

4. The distribution network security domain assessment method considering dual-end interconnection backup as described in claim 1, characterized in that, Define the load scan direction vector as follows: ； in, The angle of the scanning ray; Along the scanning ray, the load operating point is specifically as follows: ； in, The distance of the ray represents the load level along that direction.

5. The distribution network security domain assessment method considering dual-end interconnection backup as described in claim 1, characterized in that, By using the safety boundary distances found from the first two rays to perform linear extrapolation, the safety boundary distance of the current ray is predicted as follows: ； in, , Let represent the known boundary distances of the preceding and two preceding rays of the m-th ray, respectively. , , Let represent the angles of the m-th ray and the ray preceding it, and the ray two rays preceding it.

6. The distribution network security domain assessment method considering dual-end interconnection backup as described in claim 5, characterized in that, The adaptively reduced search interval is constructed based on the aforementioned safety boundary distance, specifically as follows: Calculate the adaptive neighborhood width of the current ray. : ； An adaptively reduced search interval is constructed based on the aforementioned safety boundary distance and adaptive neighborhood width: ； in, For safety reasons, Minimum neighborhood width, This indicates the upper limit of the search radius.

7. The distribution network security domain assessment method considering dual-end interconnection backup as described in claim 1, characterized in that, The safety of the load scan points within the adaptively reduced search interval is verified, specifically including: Power flow calculations are performed on the topology at the load scan point to obtain the equivalent injected power of the nodes; Within the operating point of the scan, check whether the capacity constraints of the feeder and main transformer are met. After the capacity constraint is passed, solve the complete set of AC power flow equations to determine whether the voltage of all nodes in the network is within the allowable range. After the above security checks pass, security checks are performed on the endpoints of the adaptively reduced search interval. If the checks fail, the system falls back to the global search interval and performs a standard binary search.

8. The distribution network security domain assessment method considering dual-end interconnection backup as described in claim 1, characterized in that, Determine whether to trigger local encryption when the following conditions are met: If the discrete curvature of a boundary point in the safety domain exceeds a set threshold, the chord length-curvature error between adjacent boundary points exceeds a preset error tolerance, or the concavity / convexity sign is flipped, a new scanning ray is inserted between the two adjacent boundary points.

9. A distribution network security domain assessment system considering dual-end interconnection backup, characterized in that, include: The safety configuration module is used to construct a distribution network model with distributed power sources and energy storage systems under dual-terminal interconnection, define the safety judgment criteria for grid operation, and construct an N-1 dynamic fault set. The interval coarse scan module is used to define the load scanning direction vector. In the two-dimensional feeder load space, a ray scan is performed starting from the coordinate origin. The safe boundary distance of the current ray is predicted by linear extrapolation using the safe boundary distances found by the first two rays. An adaptive shrinking search interval is constructed based on the safe boundary distance. The safety verification module is used to verify the safety of the load scan points within the adaptive shrinking search interval. If the verification passes, a standard binary search is performed within the adaptive shrinking search interval to finally locate the safety domain boundary point in the current ray direction. The curve encryption module is used to calculate the discrete curvature of each security domain boundary point and the chord length-curvature error between two adjacent boundary points, and to determine whether local encryption is triggered. The security domain boundary search is performed again on the encryption curve to obtain the final distribution network security domain.

10. A terminal device comprising a processor and a memory, the processor for implementing instructions; the memory for storing multiple instructions, characterized in that, The instructions are adapted to be loaded by a processor and executed as described in any one of claims 1-8, for evaluating the security domain of a distribution network taking into account dual-terminal interconnection backup.

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