A method for configuring a segment device considering photovoltaic cutout ratio and overvoltage constraint in low-frequency load shedding

Abstract

This invention discloses a segment-domain device configuration method considering photovoltaic (PV) cut-off ratios and overvoltage constraints in low-frequency load shedding, belonging to the field of power system low-frequency load shedding control and distribution network optimization configuration. First, topology data, node source-load data, and operational scenario data for feeders with a high proportion of distributed PV access are constructed to form the input data required for segment-domain device configuration optimization. Second, a low-frequency load shedding model considering PV cut-off ratio constraints is established, constructing the constraint relationship between segment-domain device configuration and the load shedding and source retention objectives. Third, a low-frequency load shedding model considering voltage constraints is established, incorporating feeder power flow reconfiguration and node voltage changes after segment-domain shedding into the analysis. Finally, a collaborative optimization model for segment-domain device configuration considering both PV cut-off ratio constraints and voltage constraints is constructed, solving for and outputting the optimized segment-domain device configuration results. This invention can reduce the level of distributed PV-related cut-offs while meeting low-frequency load shedding requirements, and improve the voltage safety of feeder operation after shedding.

Description

Technical Field

[0001] This invention belongs to the field of low-frequency load shedding control of power systems and distribution network optimization configuration, specifically relating to a segment-domain device configuration method that considers photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding. Background Technology

[0002] As the penetration rate of distributed photovoltaic (PV) power in distribution networks continues to increase, the "source-load coexistence" characteristic in feeders is becoming increasingly prominent, posing new applicability challenges to traditional low-frequency load shedding methods in high-distribution PV scenarios. Existing low-frequency load shedding methods primarily aim to quickly restore active power balance after system disturbances, typically employing feeder-level or load block-level shedding in distribution networks to meet load shedding demands and suppress further system frequency decline. However, in high-distribution PV feeders, feeder-level load shedding often simultaneously shelds out distributed PV power along with the load, resulting in significant renewable energy losses and weakening the effectiveness of low-frequency load shedding.

[0003] To improve the granularity of low-frequency load shedding and reduce the cascading shedding of distributed photovoltaic (PV) power, it is necessary to rationally configure switching devices capable of segmented shedding in the feeder. This allows the load shedding action to shift from traditional coarse-grained shedding at the feeder level to fine-grained shedding at the segment level. These segmented shedding switching devices, installed at feeder nodes, are used to shed downstream load areas; hereinafter referred to as segment devices. By configuring segment devices at key locations on the feeder, the feeder can have the ability to shed downstream loads segment by segment, thereby meeting low-frequency load shedding requirements while preserving upstream distributed PV output as much as possible, thus improving the low-frequency load shedding effect.

[0004] After configuring the segment-level device, the low-frequency load shedding action changes from traditional feeder-level disconnection to segment-level disconnection. If the downstream load at the disconnection point is disconnected, but the distributed photovoltaic (PV) system upstream of the disconnection point continues to output power, the feeder power flow distribution will be reconfigured. The power flow in some branches may change from normal downstream transmission to weak downstream transmission or even reverse flow, thereby causing a rise in local node voltage. When the voltage of the upstream distributed PV node exceeds the allowable range, the inverter may trigger overvoltage protection, causing the PV system that was not directly disconnected to be passively disconnected from the grid. Therefore, during the configuration of the segment-level device, it is not enough to only consider reducing the direct disconnection of distributed PV; the overvoltage risk that may arise after segment-level disconnection must also be included in the configuration constraints to ensure the physical feasibility and voltage safety of the low-frequency load shedding scheme under post-disconnection operating conditions.

[0005] In existing technologies, low-frequency load shedding research mainly focuses on load shedding threshold tuning, adaptive control strategies, tiered load shedding schemes, and frequency response improvement under renewable energy access conditions. Some studies have begun to focus on refined load shedding and voltage stability issues in high-distributed power generation scenarios, but most work still optimizes load shedding strategies based on existing network structures, mainly addressing the questions of "how much to cut off" and "which loads to cut off," with few considering the addition and location of segment-domain devices as core decision-making objects. Furthermore, no reports have been found on segment-domain device configuration methods that consider photovoltaic cut-off ratios and overvoltage constraints in low-frequency load shedding.

[0006] Therefore, it is necessary to propose a segment-domain device configuration method that takes into account the photovoltaic cut-off ratio and overvoltage constraints for low-frequency load shedding, so as to reduce the level of distributed photovoltaic cut-off while meeting the low-frequency load shedding requirements, and improve the operational safety and engineering applicability of the load shedding scheme. Summary of the Invention

[0007] To address the problems existing in existing technologies, this invention proposes a segment-domain device configuration method that considers photovoltaic (PV) cut-off ratios and overvoltage constraints during low-frequency load shedding. This method addresses the source-load synchronous cut-off and post-cut-off overvoltage risks that exist for feeders with a high proportion of distributed PV (PV) grid connection during low-frequency load shedding. This invention constructs a scenario combining PV output and power deficit, establishes a segment-domain device configuration model that simultaneously considers PV cut-off ratio constraints and node overvoltage constraints, and employs a two-stage solution method to determine the minimum number of segment-domain devices and their optimal installation locations. This method can reduce the level of distributed PV simultaneous cut-off while meeting low-frequency load shedding requirements and improve the voltage safety of the feeder operation after cut-off.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A segment-domain device configuration method considering photovoltaic power cut-off ratio and overvoltage constraints in low-frequency load shedding, the segment-domain device configuration method includes the following steps: S1: Construct topology data, node source-load data, and operational scenario data for feeders with a high proportion of distributed photovoltaic (PV) access, forming the input data required for segment-domain device configuration optimization. Specifically: S1.1: Establish feeder topology and node source-load data. Based on the distribution feeder topology, node loads, distributed photovoltaic (PV) grid connection capacity, and line parameters, establish a node set. Feeder set Branch road set and scene collection .in, Indicates the node number. Indicates the feeder number. Indicates the scene number. For any node... Record its feeder, parent node, child node, and active load. The base value for distributed photovoltaic installed capacity or equivalent output is and node type identifier; for any branch The system records the first node, last node, resistance, and reactance parameters. The node type identifier distinguishes between feeder root nodes, ordinary load nodes, distributed photovoltaic access nodes, and important load nodes. Specifically, a feeder root node is the starting node connecting the feeder to the upstream power grid or distribution bus; a parent node is a node upstream of a node in the feeder topology and directly connected to it; a child node is a node downstream of a node in the feeder topology and directly connected to it; a last node is a node without downstream child nodes; and a feeder radial topology refers to a tree-like power supply structure that extends from the feeder root node along the parent-child node relationship to each last node.

[0009] S1.2: Calculate the downstream load aggregation and downstream photovoltaic aggregation of the node. For any node... Then the node Downstream load aggregation and downstream photovoltaic polymerization volume It is obtained through the following recursive method: (1) in, Represents a node The set of child nodes; Indicates at node The downstream load corresponding to the execution of a segment domain cut-off; Indicates at node When the segment domain is cut off, the downstream distributed photovoltaic capacity may be cut off along with it; To represent at the node The downstream load corresponding to the execution of a segment domain cut-off; To represent at the node When the execution segment is cut off, the downstream distributed photovoltaic capacity may be cut off along with it.

[0010] If node If it is an end node, then If it is empty, then: (2) S1.3: Extract the feeder path set. Based on the radial topology of the feeder, starting from each end node, backtrack along the parent node to the corresponding feeder root node, forming a path from the feeder root node to the end node. All feeder paths are then combined into a path set. For any path , Indicates the path number. Indicates the first A sequence of nodes from the root node to the end node of the feeder. The path set. This is used to establish mutual exclusion constraints for paths to avoid repeated cut-off operations on the same feeder path.

[0011] S1.4: Determine candidate installation locations and the set of prohibited nodes for the segment-domain device. Based on the feeder topology, node type identifiers, and engineering installation conditions, establish the set of prohibited nodes. Nodes that are not allowed to install segment domain devices will be added to the set of prohibited nodes. The forbidden nodes include the following types: (1) Feeder root node, i.e., the starting node where each feeder connects to the upper-level power grid; (2) Important load nodes and upstream path nodes, namely, nodes marked as important loads or critical loads in the node type identifier and the nodes that the node passes through when traversing back to the feeder root node along the direction of the parent node; (3) Nodes that do not meet the equipment installation conditions, i.e., nodes that are not suitable for configuring segment domain devices because the installation space, operation and maintenance conditions or communication control conditions of the switchgear do not meet the requirements; (4) Nodes with an excessively high proportion of downstream photovoltaic power, i.e., nodes where the proportion of downstream photovoltaic power aggregation to downstream load aggregation exceeds a preset threshold; (5) Nodes with insufficient downstream load, i.e., nodes whose downstream load aggregation is lower than the preset minimum load cut-off threshold.

[0012] Set of forbidden nodes The remaining nodes are considered as candidate installation locations for the segment domain device. This process avoids installing the segment domain device on nodes that lack removable value or do not meet engineering implementation conditions, and provides a set of candidate installation nodes for subsequent optimization models.

[0013] S1.5: Constructing a set of photovoltaic output and power deficit combination scenarios. To reflect the uncertainty of the operating status of highly distributed photovoltaic feeders, this invention constructs photovoltaic output scenarios and power deficit scenarios. For any scenario... Let the photovoltaic output coefficient be... Power deficit is .in, Representing a scene The ratio of distributed photovoltaic power output to its installed capacity or equivalent power base value. Representing a scene The system needs to handle the low-frequency load shedding power deficit. Combining different photovoltaic output levels and different power deficit levels creates a "photovoltaic output - power deficit" combined scenario. That is, we get the scene set S.

[0014] From S1.1 to S1.5, we obtain input data including feeder topology, node load, distributed photovoltaic capacity, branch parameters, downstream aggregation, path set, candidate installation location, forbidden node set, and combined scenario set, which provides a foundation for the subsequent establishment of a segment domain device configuration model that considers photovoltaic cut-off ratio constraints and overvoltage constraints.

[0015] S2: Establish a low-frequency load shedding model considering the photovoltaic cutoff ratio constraint, and construct the constraint relationship between the segment-domain device configuration and the load shedding and source retention objective. Specifically: S2.1: Define segment domain device installation variables, segment domain action variables, and physical resection variables. The node set obtained based on S1 is... Let the set of scenarios be S. For any node... Define segment domain device installation variables for: (3) For any scenario Define segment domain action variables for: (4) S2.2: Establish logical constraints between the installation state and the operation state. Since a cut-off operation is only allowed at the location of an installed segment domain device, for any node... and any scene ,have: (5) At the same time, the following logical linearization constraints are established: (6) in, Represents the node In the scene Whether the physical resection variable forms an actual segment domain resection action; when the node When a segmentation device is installed at a location and the device performs a cutting operation... ,otherwise .

[0016] Through the above constraints, it can be guaranteed that only when the node The segment domain device is installed and it is in the scene When the following action is performed, Only when the value is 1 can the actual resection status be correctly expressed.

[0017] S2.3: Establish feeder-level cutoff variables. For the feeder set... Any feeder and any scene Define feeder-level cutoff variables for: (7) The feeder-level cutoff variable is used to characterize traditional feeder-level cutoff actions, and together with the segment-domain cutoff action, constitutes a set of low-frequency load shedding actions. By simultaneously setting the feeder-level cutoff variable and the segment-domain cutoff variable, the two types of actions, feeder-level cutoff and segment-domain cutoff, are described in a unified manner.

[0018] S2.4: Establish mutual exclusion constraints for feeder paths. Since the research object is a radial feeder structure, for any path tracing back from the end node to the feeder root node, if a cut-off action has already occurred upstream, the downstream should not repeat the cut-off action; otherwise, it will lead to overlapping cut-off areas and duplicate load and photovoltaic calculations. Therefore, for any path in the feeder... and any scenario Establish path mutual exclusion constraints: (8) in Representing a path The number of the feeder to which it belongs. Representing a scene Next path The feeder-level cutoff variable of the feeder. This path mutual exclusion constraint ensures that the path from the feeder root node to any end node is cut off at most once, thus satisfying the topological logic of the radial feeder.

[0019] S2.5: Establish the expression for net load reduction in the scenario. For any scenario... Set up feeder The total load is Total photovoltaic power is ;node The downstream load polymerization rate is Downstream photovoltaic polymerization volume The photovoltaic power output coefficient is Then the scene The net load reduction is formed by the combined feeder-level and segment-level cutoffs. Represented as: (9) Feeder-level cutoff corresponds to the simultaneous disconnection of the load and photovoltaic power along the entire feeder. Segment-level cutoff corresponds to the simultaneous disconnection of the load and photovoltaic power in the downstream area of ​​the node. The net load reduction is the amount of load cutoff minus the photovoltaic power output of the synchronously cutoff.

[0020] S2.6: Establish the expression for photovoltaic cut-off amount under any scenario. For any scenario Distributed photovoltaic power cut-off volume formed by feeder-level cut-off and segment-level cut-off Represented as: (10) This formula is used to characterize the scene. The amount of distributed photovoltaic power generation cut-off caused by low-frequency load shedding.

[0021] S2.7: Establish net load reduction constraints. (Scenario description follows) The power deficit that the downstream system needs to bear is Let the upper limit of the allowed overcut ratio be... To ensure that low-frequency load shedding actions meet the system's load reduction requirements while avoiding a net load shedding amount significantly exceeding the actual demand, for any scenario... The following net load reduction constraint is established: (11) The constraints on the left side are used to ensure that the net load shedding is not less than the power deficit required by the system, and on the right side are used to limit the net load shedding to not exceed the allowable over-cut limit, thereby controlling the low-frequency load shedding action within the range that meets the load shedding requirements and does not over-cut.

[0022] S2.8: Establish constraints on the photovoltaic (PV) cutoff ratio. To achieve the goal of "load shedding and source retention," it is necessary to limit the proportion of distributed PV power cutoff during low-frequency load shedding. Let the upper limit of the allowed PV cutoff ratio be... For any scenario Establish the photovoltaic cut-off ratio constraint, as shown in formula (12): (12) To facilitate optimization, the vacuolation ratio constraint is further linearized as follows: (13) By constraining the photovoltaic cut-off ratio, it is possible to ensure that the proportion of distributed photovoltaic cut-off is controlled within a preset range while meeting the low-frequency load reduction requirements.

[0023] S2.9: Establish constraints on candidate installation locations and the number of installations. For the set of forbidden nodes... any node Establish the selection restriction constraint, as shown in formula (14): (14) To limit the overall configuration scale of segment domain devices, further constraints on the number of installations are established. Let the total number of segment domain devices installed in the system be... Then we have: (15) When optimizing the minimum installation size later, As an optimization target.

[0024] S2.10: From S2.1 to S2.9, a low-frequency load shedding model considering photovoltaic (PV) cut-off ratio constraints is formed. This low-frequency load shedding model is based on the feeder topology, with segment-level device installation variables, action variables, and physical cut-off variables as core decision variables. By uniformly describing feeder-level and segment-level cut-off actions, it constructs a low-frequency load shedding model that satisfies power deficit constraints, over-cutting constraints, path mutual exclusion constraints, and PV cut-off ratio constraints, thereby achieving segment-level device configuration and load shedding action modeling oriented towards the "load shedding and source retention" objective.

[0025] S3: Establish a low-frequency load shedding model considering voltage constraints, incorporating feeder power flow reconfiguration and node voltage changes after segment disconnection into the analysis. Specifically: S3.1: Analysis of the feeder power flow reconfiguration mechanism after segment disconnection. Since segment disconnection changes the retention status of loads and distributed photovoltaic systems in the feeder, in a given scenario... Below, the equivalent net load of each node in the feeder will change with the disconnection operation. For any node... Assume its load active power The base value for distributed photovoltaic installed capacity or equivalent output is Scene The photovoltaic output coefficient is Then, under the action of segment domain resection, the node Equivalent net active load Represented as: (16) in, For nodes In the scene The physical charged state variables under the node. When the node When power is maintained, When node When power is lost due to feeder level cutoff or section cutoff .

[0026] S3.2: Establish the correlation between the physical energized state of a node and its disconnection action. Since whether a node is energized depends on the disconnection state of its upstream feeder and the segment disconnection state along its path, a physical energized state variable needs to be established based on the feeder topology. The mapping relationship between the node and the cutoff variable. and any scenario If node The feeder is ,in Represents a node The node is the number of the feeder it belongs to. The physical charged state is affected by the feeder level cutoff variable. and from the feeder root node to the node The physical cut-off variables along the upstream path have a combined effect. This is influenced by the node's physical charged state variables. It can uniformly characterize the retention state of nodes after removal and be used for subsequent power flow and voltage constraint modeling.

[0027] S3.3: Establish the equivalent net reactive load expression for each node. For any node... Let its load reactive power be Then the scene Next node Equivalent net reactive load Represented as: (17) In this invention, when reactive load data at a node is missing, it can be determined based on the load power factor or the typical ratio of active to reactive power. Equivalent estimation is performed to form the equivalent net reactive load expression for the node.

[0028] S3.4: Establish branch power flow variables, including branch active power flow variables. and branch reactive power flow variables .

[0029] Let the set of feeder branches be For any branch and any scenario Define the active power flow variables of the branch. and branch reactive power flow variables , respectively used to represent scenes Lower branch road Active and reactive power flows are defined. The positive direction of branch power flow is defined as from the root node of the feeder to the end node of the feeder.

[0030] S3.5: Establish active power flow balance constraints for branch paths. For any branch path... and any scenario ,node The active power flow of the upstream branch should be equal to that of the node. The equivalent net active power load is the sum of the active power flow of its downstream branches. Therefore, the active power flow balance constraint of the branches is established, as shown in formula (18): (18) in, Represents a node The set of child nodes For nodes Child node number; For the scene Lower branch road The above is from the node Pointing to node The meritorious trend; For the scene Lower branch road The above is from the node Pointing to node The meritorious trend; Represents a node In the scene The equivalent net active power load is calculated. The active power flow balance constraint of this branch is used to characterize the distribution relationship of active power flow in the feeder after the segment is cut off.

[0031] S3.6: Establish reactive power flow balance constraints for branch paths. For any branch path... and any scenario ,node The reactive power flow of the upstream branch should be equal to that of the node. The equivalent net reactive load is the sum of the reactive power flow of its downstream branches. Therefore, the reactive power flow balance constraint of the branches is established, as shown in formula (19): (19) in, For the scene Lower branch road The above is from the node Pointing to node The unproductive current; For the scene Lower branch road The above is from the node Pointing to node The unproductive current; Represents a node In the scene The equivalent net reactive load is calculated. The reactive power flow balance constraint of this branch is used to characterize the distribution relationship of reactive power flow in the feeder after the segment is cut off.

[0032] S3.7: Establish node voltage variables. For any node and any scenario Define node voltage variables , used to represent nodes In the scene The square of the voltage amplitude or equivalent voltage quantity. For the feeder root node Its voltage is given by the upstream power grid and is denoted as: (20) in, Indicates the root node of the feeder In the scene The node voltage below; This is the rated voltage of the feeder root node.

[0033] S3.8: Establish node voltage recursion constraints. Assume the branch... The resistance and reactance are respectively and For any branch and any scenario Based on the linearized power flow model of the distribution network, the node voltage recursive constraint is established as shown in formula (21): (twenty one) in Represents a node In the scene The node voltage is determined by a recursive constraint. This node voltage constraint is used to characterize the voltage drop or voltage rise characteristics of the node voltage along the feeder direction as the branch power flow changes.

[0034] S3.9: Establish upper and lower limit constraints for node voltage. To ensure that the feeder operation meets voltage safety requirements after segment disconnection, for any node... and any scenario Establish upper and lower limit constraints for node voltages, as shown in formula (22): (twenty two) in, and Representing nodes respectively Permissible lower and upper voltage limits.

[0035] S3.10: Establish coupling constraints between the disconnection action and the power flow and voltage relationships. Since the load and distributed photovoltaic power of a node no longer participate in feeder power flow calculations after power loss, and the branch power flow and voltage recursion relationships related to the power loss area no longer have practical operational significance, it is necessary to include the node's physical energized state variables. It is coupled with the branch power flow and node voltage recursion relationship.

[0036] For any branch road and any scenario If downstream nodes Keep it charged, that is If the power flow constraints and voltage recursion relationships corresponding to that branch are in effect, then the power flow constraints and voltage recursion relationships for that branch will take effect normally; if the downstream node Power has been lost, that is If the active and reactive power flows of that branch are restricted to zero, the corresponding voltage recursion relationship is relaxed. Active and reactive power flows should be restricted to zero, and the corresponding voltage recursion relationship for that branch should be relaxed.

[0037] Therefore, the following coupling constraints are established between branch power flow and node energized state: (twenty three) in, and These are the large M constants for active power flow and reactive power flow, respectively. Through coupling constraints, when... At that time, the branch road The meritorious trend and the trend of no effort Limited to zero; when At that time, the power flow of the branch can vary within the allowable range.

[0038] Furthermore, to ensure that the voltage recursion relationship is effective when nodes are energized and does not constrain the model when nodes are de-energized, the following conditional voltage recursion constraint is established: (twenty four) in, This is the large M constant corresponding to the voltage recursion constraint. When When the above constraints degenerate into nodal voltage recursive equations; when At this point, the aforementioned constraints are relaxed, thereby avoiding the application of meaningless voltage recursion to the excised region.

[0039] S3.11: From S3.1 to S3.10, a low-frequency load shedding model considering voltage constraints is formed. This low-frequency load shedding model is based on the feeder power flow reconfiguration mechanism after segment-domain disconnection. Through node injection power relationships, branch power flow balance relationships, node voltage recursion relationships, and node voltage upper and lower limit constraints, it characterizes the voltage change characteristics of the feeder after segment-domain disconnection, thereby incorporating the risk of node voltage exceeding limits after disconnection into the low-frequency load shedding analysis. This provides a foundation for subsequently constructing a segment-domain device configuration model that simultaneously considers photovoltaic disconnection ratio constraints and voltage constraints.

[0040] S4: Based on the low-frequency load shedding model considering photovoltaic (PV) cutoff ratio constraints constructed in S2 and the low-frequency load shedding model considering voltage constraints constructed in S3, a segment-domain device configuration collaborative optimization model considering both PV cutoff ratio constraints and voltage constraints is constructed. Specifically: S4.1: Based on the low-frequency load shedding model considering photovoltaic cut-off ratio constraints established in S2, the node injection power relationship, branch power flow balance relationship, node voltage recursion relationship and node voltage upper and lower limit constraints established in S3 are introduced. Power deficit constraints, overcut constraints, feeder path mutual exclusion constraints, action logic constraints, photovoltaic cut-off ratio constraints and node voltage constraints are uniformly incorporated into the same optimization framework, thereby constructing a segment domain device configuration collaborative optimization model that simultaneously considers photovoltaic cut-off ratio constraints and voltage constraints.

[0041] S4.2: Establish the first-stage optimization objective. Since the configuration scale of the segment-domain devices directly determines the feeder modification cost, the first-stage optimization objective is to minimize the total number of segment-domain devices installed. Let the total number of segment-domain devices installed in the system be... The first-stage optimization objective is expressed as: (25) in, The variable for installing segment-domain devices is defined. Using the first-stage optimization objective function shown in formula (25), the minimum number of segment-domain devices installed can be obtained while satisfying all scenario constraints, denoted as... .

[0042] S4.3: In the first phase, for any scenario At the same time, the following operational constraints are established: (26) The first-stage optimization model's constraint set is formed by combining the action logic constraints (S2.2), path mutual exclusion constraints (S2.3), and forbidden node constraints (S2.9) established in S2, with the power flow constraints (S3.5, S3.6) and node voltage constraints (S3.9) established in S3. This constraint set ensures that the number of segment-domain devices installed under different scenarios meets the load reduction requirements, photovoltaic cut-off ratio requirements, and post-cut-off voltage safety requirements. The first-stage optimization model is formed by the first-stage optimization objective in S4.2 and the first-stage constraint set in S4.3. This first-stage optimization model is used to solve for the minimum number of segment-domain devices installed while satisfying all scenario constraints. .

[0043] S4.4: Calculate the minimum number of devices to be installed in the segment region. Then, establish the second-phase optimization objectives. The second phase involves the installation of a fixed-section domain device with a total number of [number missing]. Under these conditions, with the goal of minimizing the amount of distributed photovoltaic power generation cutoff, the installation location of the segmental devices is further optimized. Let the scenario set be... The second-stage optimization objective is then expressed as: (27) Or equivalently expressed as: (28) in, The total number of scenarios is represented by . The configuration scheme of the segment device with the minimum photovoltaic disconnection amount is obtained by using the second-stage optimization objective function shown in formula (27) or (28) under the condition of fixed number of switches.

[0044] S4.5: In the second phase, establish fixed installation quantity constraints: (29) The net load shedding constraint (S2.7), photovoltaic cut-off ratio constraint (S2.8), action logic constraint (S2.2), path mutual exclusion constraint (S2.3), power flow balance constraint (S3.5, S3.6), and node voltage constraint (S3.9) from the first stage are retained to ensure that the segment-domain device installation locations obtained in the second stage still meet the operational feasibility requirements in all scenarios. The second-stage optimization model is composed of the second-stage optimization objective in S4.4 and the aforementioned second-stage constraint set. The second-stage optimization model is used to fix the minimum installation quantity. Under the given conditions, find the installation location of the segment device with the minimum disconnection amount for distributed photovoltaic systems.

[0045] S4.6: For any feeder Considering the engineering upper limit on the number of segment devices that can be installed on different feeders, a constraint is established on the number of feeder installations. Let the feeder... The maximum number of segment domain devices allowed to be installed is Then we have: (30) in, Indicates feeder The set of nodes on the feeder. By constraining the number of feeders installed, the excessive concentration of segment-domain devices on a single feeder can be avoided, improving the engineering rationality of the configuration.

[0046] S4.7: For the set of forbidden nodes any node Keep the following constraints unchanged: (31) This constraint ensures that critical load nodes, feeder root nodes, and other nodes that do not meet the installation conditions are not selected as locations for section area device configuration, thereby ensuring that the section area device configuration scheme meets actual operating requirements.

[0047] S4.8: Combine the first-stage optimization objective and the second-stage optimization objective with the corresponding constraint set to form a two-stage segment-domain device configuration collaborative optimization model. In the two-stage segment-domain device configuration collaborative optimization model, the first stage is used to determine the minimum number of segment-domain devices to satisfy all scenario constraints, and the second stage is used to further optimize the configuration position of segment-domain devices under a fixed number of installations, thereby simultaneously taking into account the scale of the renovation, photovoltaic retention capacity, and post-cutoff operation safety.

[0048] S4.9: Through the two-stage segment-domain device configuration collaborative optimization model, the following objectives can be achieved: while meeting the low-frequency load reduction requirements, minimize the number of segment-domain devices installed; under the condition of a fixed number of installations, minimize the level of distributed photovoltaic interconnection disconnection; and at the same time, by introducing node voltage constraints, ensure that the feeder operation status after disconnection meets the voltage safety requirements.

[0049] S4.10: From S4.1 to S4.9, a segment-domain device configuration collaborative optimization model is formed that simultaneously considers photovoltaic (PV) cut-off ratio constraints and voltage constraints. This model uses segment-domain device installation variables, action variables, physical cut-off variables, power flow variables, and voltage variables as core decision variables. By uniformly coordinating load reduction requirements, PV retention targets, and voltage safety requirements, it establishes a segment-domain device optimization configuration framework for high-distribution PV feeders, providing a foundation for subsequent solution method design.

[0050] S5: A two-stage solution method is used to solve the segment-domain device configuration collaborative optimization model established in S4. The first stage uses a configuration scale solution method based on scenario iteration, and the second stage uses a configuration position optimization solution method based on logical Benders decomposition, outputting the optimized configuration results of the segment-domain devices. Specifically: S5.1: Construct the initial active scene set for the first phase. In the first phase, it is necessary to construct the initial active scene set across all scenes. The following solution is needed to determine the minimum number of segment-domain devices required to satisfy low-frequency load shedding requirements, photovoltaic cut-off ratio constraints, and voltage constraints. When there are many scenarios, directly establishing complete constraints for all scenarios simultaneously results in a large optimization model size. Therefore, a configuration-scale solution method based on scenario iteration is adopted, starting with the entire scenario set... Selecting some representative scenarios to form an initial set of active scenarios. .

[0051] The representative scenarios include scenarios with significant power deficits, scenarios with high distributed photovoltaic output, scenarios with low net loads, and typical medium-operational scenarios. These representative scenarios are then included in the initial active scenario set. This allows the initial solution process in the first stage to prioritize covering operating conditions with high load reduction requirements, high risk of photovoltaic disconnection, and high risk of voltage over-limit.

[0052] S5.2: Let the first... The set of active scenarios in the round of iteration is ,and Based on the current set of active scenarios , establish the first The current active scenario optimization problem is addressed. This optimization problem uses the first-stage optimization objective of S4.2 as the objective function, and only applies to... The first stage constraint set S4.3 is applied to the scenario in which the objective function can be expressed as: (32) in, This indicates the first phase of scenario iteration rounds. Indicates the first The number of segment-domain devices installed is obtained through round-by-round iteration. For nodes The variable is installed in the segment domain device. Solve the first... After optimizing the current active scenarios, the current installation solution is obtained. and corresponding installation quantity .in, Indicates the first The set of installation locations of segment domain devices obtained by round iteration.

[0053] S5.3: Perform a full-scenario verification of the current installation scheme. (The remaining text appears to be incomplete and possibly contains errors. A more accurate translation would require the full context.) The current installation solution that comes first Substitute all scene sets The system performs verification to determine whether it meets the constraints outlined in S4 regarding net load shedding limits, photovoltaic cut-off ratio, path exclusivity, forbidden node selection, branch power flow balance, node voltage recursion, and node voltage limits in each scenario. If the current installation scheme fails to meet these constraints in a particular scenario, that scenario is identified as a failure scenario. Let the first... The set of failure scenarios identified in the full-scenario verification is as follows .

[0054] S5.4: Update the set of active scenarios in the first phase. If the... The set of failure scenarios obtained by full-scenario verification If the set of failed scenarios is not empty, then the set of failed scenarios is added to the current set of active scenarios, and the set of active scenarios for the next round is obtained: (33) in, Indicates the first The set of failed scenarios identified during the global check is then returned to S5.2, based on the updated set of active scenarios. Re-establish and solve the optimization problem for the current active scenario.

[0055] S5.5: Repeat the iterative process of "solving the current active scene optimization problem - global scene verification - adding failed scenes" from S5.2 to S5.4 until the set of failed scenes is reached. Empty. At this point, the current installation plan... All scenario constraints have been met, the first phase of iteration terminates, and the minimum number of segment domain devices required to satisfy all scenario constraints is output. and its corresponding feasible initial installation scheme .

[0056] S5.6: In the second phase, the number of fixed segment domain devices installed is the minimum number of devices obtained in the first phase. Furthermore, a configuration location optimization solution method based on logical Benders decomposition is adopted to further optimize the installation location of segment-domain devices. The second stage aims to minimize the amount of distributed photovoltaic interconnection cut-off, searching for a better segment-domain device installation location scheme under the condition of a fixed number of installations.

[0057] S5.7: Let the scene set be... Then the objective function for the second stage is expressed as: (34) in, For the scene The amount of distributed photovoltaic power cut-off below, This represents the total number of scenes.

[0058] S5.8: In the second stage, the logical Benders decomposition method is used to solve the configuration location optimization problem. The logical Benders decomposition method is an existing decomposition solution approach; this invention applies it to the segment domain device configuration model, decomposing the second-stage problem into a main configuration location problem and scenario sub-problems. The main problem is used to determine the installation location variables of the segment domain device. and in a fixed number of installations Candidate installation schemes are generated under the given conditions; the scenario sub-problems are used to analyze the feasibility of load reduction actions, the amount of distributed photovoltaic power cut-off, and the satisfaction of node voltage constraints for each scenario under the given candidate installation schemes.

[0059] S5.9: The main problem in the second phase satisfies the following fixed installation quantity constraint: (35) It also satisfies the restrictions on prohibited nodes and the upper limit on the number of feeder installations to ensure that the candidate installation schemes meet the configuration range requirements.

[0060] S5.10: For any scenario Given the main problem installation scheme Under these conditions, corresponding scenario subproblems are established. These subproblems are used to solve the scenario. The system records feeder-level cutoff actions, segment-level cutoff actions, branch power flow status, and node voltage status, and outputs the installation scheme in the scenario. Photovoltaic cut-off amount and the degree of constraint on default, among which Indicates in the scene Installation plan The amount of photovoltaic power removed.

[0061] S5.11: To improve the stability of the second-stage solution process, slack variables are introduced into the scenario subproblems to measure insufficient load shearing, over-shearing exceeding limits, photovoltaic ratio exceeding limits, and node voltage exceeding limits. Let the scenario be... The overall relaxation amount is Then we have: (36) in, This indicates insufficient slack due to load reduction. Indicates the amount of over-shear relaxation. This indicates the proportion of default slack in the photovoltaic sector. and These represent the upper voltage limit and lower voltage limit relaxation amounts, respectively. , , , , All are non-negative slack variables. These non-negative slack variables are only used for the second-stage scenario verification and main problem feedback, and do not change the requirement that the final solution still needs to meet all scenario hard constraints.

[0062] S5.12: If the current installation scheme There are obvious defaults in certain scenarios, namely the overall slack in the corresponding scenarios. If the threshold is exceeded, the scenario is identified as a critical scenario and added to the second-stage main problem scenario set to correct the search direction of the main problem. The update relationship of the second-stage main problem scenario set is expressed as follows: (37) in, Indicates the second phase iteration round. Indicates the first The set of main problem scenarios in the round of iteration, Indicates the first A set of key scenarios identified in the analysis of wheel problems.

[0063] S5.13: If the current installation scheme meets the requirements under the verified scenario, then calculate the target value corresponding to the candidate installation scheme based on the distributed photovoltaic power cut-off amount output by the scenario sub-problem: (38) in, Installation plan The corresponding average photovoltaic power cut-off target value. This target value... Compare with the target value of the current best feasible solution. If If the result is better than the current optimal target value, then update the optimal feasible installation plan. and the corresponding optimal target value .

[0064] S5.14: After the second phase of iteration, output the current optimal feasible installation plan. And determine the final optimized configuration result of the segment domain device based on the installation plan. Definition For nodes The final segment domain device installation state variables. For any node If node This is the optimal and feasible installation solution. Then we have: Otherwise: .

[0065] This results in the final configuration scheme of the segment domain device that satisfies all scenario constraints.

[0066] S5.15: Optimal feasible installation scheme for segment-domain devices Below, output the low-frequency load shedding action results for each scenario. For any scenario... The results of low-frequency load shedding actions include at least feeder-level shedding actions, segment-level shedding actions, net load shedding for the scene, and distributed photovoltaic shedding. Among them, the scene... The best feasible installation solution The net load shedding and photovoltaic disconnection are expressed as follows: and .

[0067] S5.16: From S5.1 to S5.15, complete the two-stage solution of the collaborative optimization model and output the optimized configuration results of the segment domain device that satisfy the photovoltaic cut-off ratio constraint and voltage constraint.

[0068] The beneficial effects of this invention are as follows: (1) By configuring a segmented disconnection device at a key location of the feeder, the present invention transforms the traditional feeder-level low-frequency load shedding method into a segmented-level refined disconnection method, which can reduce the synchronous disconnection of load and distributed photovoltaic while meeting the low-frequency load shedding requirements, thereby reducing the level of distributed photovoltaic disconnection.

[0069] (2) The present invention introduces photovoltaic cut-off ratio constraints in the segment domain device configuration model and incorporates the distributed photovoltaic cut-off amount into the low-frequency load reduction modeling process, so that the obtained configuration scheme can not only meet the system power deficit requirements, but also constrain the distributed photovoltaic cut-off ratio, thereby improving the new energy retention capacity in high distributed photovoltaic feeder scenarios.

[0070] (3) The present invention further considers the power flow reconstruction of feeders and the change of node voltage after the segment domain is cut off. By establishing the node injection power relationship, the branch power flow balance relationship and the upper and lower limit constraints of node voltage, the risk of voltage exceeding the limit after the cut-off is incorporated into the segment domain device configuration process, which improves the physical feasibility and operational safety of the low-frequency load reduction scheme.

[0071] (4) The present invention constructs a segment domain device configuration collaborative optimization model that simultaneously considers power deficit, over-cut control, photovoltaic cut-off ratio, feeder topology logic and node voltage constraints. It can coordinate load reduction requirements, photovoltaic retention targets and voltage safety requirements under the same framework, and avoid the operational risks caused by configuring from the perspective of a single load reduction amount or a single photovoltaic retention. Attached Figure Description

[0072] Figure 1 Schematic diagram of traditional feeder-level load reduction and section-level load shedding and source retention load reduction; Figure 2 This is a diagram of the distribution network topology for an example. Figure 3 Here is a flowchart of the two-stage solution method; Figure 4 This is a flowchart of the method of the present invention. Detailed Implementation

[0073] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the invention.

[0074] A method for configuring segment-domain devices considering photovoltaic power cut-off ratio and overvoltage constraints in low-frequency load shedding includes the following steps: S1.1: Establish feeder topology and node source-load data. Based on the distribution feeder topology, node loads, distributed photovoltaic (PV) grid connection capacity, and line parameters, establish a node set. Feeder set Branch road set and scene collection .in, Indicates the node number. Indicates the feeder number. Indicates the scene number. For any node... Record its feeder, parent node, child node, and active load. The base value for distributed photovoltaic installed capacity or equivalent output is and node type identifier; for any branch The system records the first node, last node, resistance, and reactance parameters. The node type identifier distinguishes between feeder root nodes, ordinary load nodes, distributed photovoltaic access nodes, and important load nodes. Specifically, a feeder root node is the starting node connecting the feeder to the upstream power grid or distribution bus; a parent node is a node upstream of a node in the feeder topology and directly connected to it; a child node is a node downstream of a node in the feeder topology and directly connected to it; a last node is a node without downstream child nodes; and a feeder radial topology refers to a tree-like power supply structure that extends from the feeder root node along the parent-child node relationship to each last node.

[0075] S1.2: Calculate the downstream load aggregation and downstream photovoltaic aggregation of the node. For any node... Then the node Downstream load aggregation and downstream photovoltaic polymerization volume It is obtained through the following recursive method: (1) in, Represents a node The set of child nodes; Indicates at node The downstream load corresponding to the execution of a segment domain cut-off; Indicates at node When the segment domain is cut off, the downstream distributed photovoltaic capacity may be cut off along with it; To represent at the node The downstream load corresponding to the execution of a segment domain cut-off; To represent at the node When the execution segment is cut off, the downstream distributed photovoltaic capacity may be cut off along with it.

[0076] If node If it is an end node, then If it is empty, then: (2) S1.3: Extract the feeder path set. Based on the radial topology of the feeder, starting from each end node, backtrack along the parent node to the corresponding feeder root node, forming a path from the feeder root node to the end node. All feeder paths are then combined into a path set. For any path , Indicates the path number. Indicates the first A sequence of nodes from the root node to the end node of the feeder. The path set. This is used to establish mutual exclusion constraints for paths to avoid repeated cut-off operations on the same feeder path.

[0077] S1.4: Determine candidate installation locations and the set of prohibited nodes for the segment-domain device. Based on the feeder topology, node type identifiers, and engineering installation conditions, establish the set of prohibited nodes. Nodes that are not allowed to install segment domain devices will be added to the set of prohibited nodes. The forbidden nodes include the following types: (1) Feeder root node, i.e., the starting node where each feeder connects to the upper-level power grid; (2) Important load nodes and upstream path nodes, namely, nodes marked as important loads or critical loads in the node type identifier and the nodes that the node passes through when traversing back to the feeder root node along the direction of the parent node; (3) Nodes that do not meet the equipment installation conditions, i.e., nodes that are not suitable for configuring segment domain devices because the installation space, operation and maintenance conditions or communication control conditions of the switchgear do not meet the requirements; (4) Nodes with excessively high downstream photovoltaic capacity, i.e., nodes where the ratio of downstream photovoltaic aggregation to downstream load aggregation exceeds a preset threshold; the preset threshold is 0.35. (5) Nodes with excessively small downstream load, i.e., nodes whose downstream load aggregation is lower than the preset minimum cut-off load threshold, wherein the preset minimum cut-off load threshold is 50kW.

[0078] Set of forbidden nodes The remaining nodes are considered as candidate installation locations for the segment domain device. This process avoids installing the segment domain device on nodes that lack removable value or do not meet engineering implementation conditions, and provides a set of candidate installation nodes for subsequent optimization models.

[0079] S1.5: Constructing a set of photovoltaic output and power deficit combination scenarios. To reflect the uncertainty of the operating status of highly distributed photovoltaic feeders, this invention constructs photovoltaic output scenarios and power deficit scenarios. For any scenario... Let the photovoltaic output coefficient be... Power deficit is .in, Representing a scene The ratio of distributed photovoltaic power output to its installed capacity or equivalent power base value. Representing a scene The system needs to handle the low-frequency load shedding power deficit. Combining different photovoltaic output levels and different power deficit levels creates a "photovoltaic output - power deficit" combined scenario. That is, we get the scene set S.

[0080] S2: Establish a low-frequency load shedding model considering the photovoltaic power cut-off ratio constraint. Specifically: S2.1: For any node Define segment domain device installation variables When node When installing the segment domain device ;otherwise, ,Right now: (3) For any scenario Define segment domain action variables for: (4) S2.2: Establish logical constraints between the installation state and the operation state. Since a cut-off operation is only allowed at the location of an installed segment domain device, for any node... and any scene ,have: (5) At the same time, in order to make physical removal variables To accurately represent the combined effect of the installation state and the action state, the following logical linearization constraints are established: (6) Through the above constraints, it can be guaranteed that only when the node The segment domain device is installed and it is in the scene When the following action is performed, Only when the value is 1 can the actual resection status be correctly expressed.

[0081] S2.3: Establish feeder-level cutoff variables. For the feeder set... Any feeder and any scene Define feeder-level cutoff variables for: (7) S2.4: To avoid repeated cutting on the same path, for any path in the feeder... and any scenario Establish path mutual exclusion constraints: (8) in, Representing a scene Down and path This corresponds to the feeder-level cut-off action variable. This constraint ensures that the cut-off occurs at most once on the path from the feeder root node to any end node, thus satisfying the topological logic of the radial feeder.

[0082] S2.5: For any scenario Set up feeder The total load is Total photovoltaic power is ;node The downstream load polymerization rate is Downstream photovoltaic polymerization volume The photovoltaic power output coefficient is Then the scene The net load reduction is formed by the combined feeder-level and segment-level cutoffs. It can be represented as: (9) Among them, feeder-level cut-off corresponds to the simultaneous disconnection of the load and photovoltaic power of the entire feeder, while segment-level cut-off corresponds to the simultaneous disconnection of the load and photovoltaic power of the downstream area of ​​the node. The net load reduction is the amount of load cut-off minus the photovoltaic power output of the synchronously cut-off.

[0083] S2.6: For any scenario Distributed photovoltaic power cut-off volume formed by feeder-level cut-off and segment-level cut-off It can be represented as: (10) This formula is used to characterize the scene. The size of the distributed photovoltaic system interrupted by low-frequency load shedding.

[0084] S2.7: Establish net load reduction constraints. (Scenario description follows) The power deficit that the downstream system needs to bear is Let the upper limit of the allowed overcut ratio be... To ensure that low-frequency load shedding actions meet the system's load reduction requirements while avoiding a net load shedding amount significantly exceeding the actual demand, for any scenario... The following net load reduction constraint is established: (11) The constraints on the left side are used to ensure that the net load shedding is not less than the power deficit required by the system, and on the right side are used to limit the net load shedding to not exceed the allowable over-cut limit, thereby controlling the low-frequency load shedding action within the range that meets the load shedding requirements and does not over-cut.

[0085] S2.8: To achieve the goal of "load shedding and source retention," it is necessary to limit the proportion of distributed photovoltaic (PV) power cut-off during low-frequency load shedding. Let the upper limit of the allowed PV power cut-off proportion be... For any scenario The following photovoltaic cut-off ratio constraint is established: (12) In this invention, the amount of distributed photovoltaic power cut-off does not exceed 5% of the net load reduction of the scenario.

[0086] S2.9: Establish constraints on candidate installation locations and the number of installations. For the set of forbidden nodes... any node Establish the following no-selection constraints: (13) To limit the overall configuration scale of segment domain devices, installation quantity constraints can be further established. Let the total number of segment domain devices installed in the system be... Then we have: (14) When optimizing the minimum installation size later, As an optimization target; when optimizing the configuration location under the condition of fixed installation scale, then As a given parameter.

[0087] S3: Establish a low-frequency load shedding model considering voltage constraints, incorporating feeder power flow reconfiguration and node voltage changes after segment disconnection into the analysis. Specifically: S3.1: Based on the established photovoltaic load shedding ratio constraint model, a low-frequency load shedding model considering voltage constraints is further established. For any node... Assume its load active power The base value for distributed photovoltaic installed capacity or equivalent output is Scene The photovoltaic output coefficient is Then, under the action of segment domain resection, the node Equivalent net active load It can be represented as: (15) in, For nodes In the scene The physical charged state variables under the node. When the node When power is maintained, When node When power is lost due to feeder level cutoff or section cutoff .

[0088] S3.2: Establish the correlation between the physical charged state of a node and the disconnection action. For any node... and any scenario If node The feeder is Then the node The physical charged state is affected by the feeder level cutoff variable. The variables related to the removal of upstream path nodes also have an impact.

[0089] S3.3: For any node Let its load reactive power be Then the scene Next node Equivalent net reactive load It can be represented as: (16) S3.4: Let the set of feeder branches be... For any branch and any scenario Define the active power flow variables of the branch. and branch reactive power flow variables , respectively used to represent scenes Lower branch road The active and inactive currents.

[0090] S3.5: For any branch and any scenario ,node The active power flow of the upstream branch should be equal to that of the node. The equivalent net active power load is the sum of the active power flow of its downstream branches. Therefore, the following active power flow balance relationship is established: (17) in, Represents a node The set of child nodes.

[0091] S3.6: For any branch and any scenario ,node The reactive power flow of the upstream branch should be equal to that of the node. The equivalent net reactive load is the sum of the reactive power flow of its downstream branches. Therefore, the following reactive power flow balance relationship is established: (18) S3.7: For any node and any scenario Define node voltage variables , used to represent nodes In the scene The square of the voltage amplitude or equivalent voltage quantity. For the feeder root node Its voltage is given by the upstream power grid and can be denoted as: (19) in, Indicates the root node of the feeder In the scene The node voltage below; This is the rated voltage of the feeder root node.

[0092] S3.8: Set up branch roads The resistance and reactance are respectively and For any branch and any scenario The recursive relationship of node voltages is established based on the linearized power flow model of the distribution network as follows: (20) in Represents a node In the scene The node voltage below.

[0093] S3.9: For any node and any scenario Establish the following node voltage constraints: (twenty one) in, and Representing nodes respectively The permissible lower and upper voltage limits. In this invention, the node voltage upper and lower limits are set to 0.90 pu and 1.10 pu, respectively.

[0094] S3.10: Establish coupling constraints between the cut-off action and the power flow and voltage relationship.

[0095] For any branch road and any scenario If downstream nodes Keep it charged, that is If downstream nodes Power has been lost, that is .

[0096] Therefore, the following coupling constraints are established between branch power flow and node energized state: (twenty two) in, and These are the large M constants for active power flow and reactive power flow, respectively. Through the above constraints, when... At that time, the branch road The meritorious trend and the trend of no effort Limited to zero; when At that time, the power flow of the branch can vary within the allowable range.

[0097] Furthermore, to ensure that the voltage recursion relationship is effective when nodes are energized and does not constrain the model when nodes are de-energized, the following conditional voltage recursion constraint is established: (twenty three) in, This is the large M constant corresponding to the voltage recursion constraint. When When the above constraints degenerate into nodal voltage recursive equations; when At this point, the aforementioned constraints are relaxed, thereby avoiding the application of meaningless voltage recursion to the excised region.

[0098] S4: Construct a segment-domain device configuration collaborative optimization model that simultaneously considers photovoltaic cut-off ratio constraints and voltage constraints. Specifically: S4.1: Based on the low-frequency load shedding model considering photovoltaic cut-off ratio constraints established in S2, the node injection power relationship, branch power flow balance relationship, node voltage recursion relationship and node voltage upper and lower limit constraints established in S3 are introduced to construct a segment domain device configuration collaborative optimization model that simultaneously considers photovoltaic cut-off ratio constraints and voltage constraints.

[0099] S4.2: Establish the first-stage optimization objective. The first-stage optimization objective is to minimize the total number of segment-domain devices installed. Let the total number of segment-domain devices installed in the system be... The first-stage optimization objective is expressed as: (twenty four) in, The variable for installing segment-domain devices is defined. Using the first-stage optimization objective function shown in formula (24), the minimum number of segment-domain devices installed can be obtained while satisfying all scenario constraints, denoted as... .

[0100] S4.3: In the first phase, for any scenario At the same time, the following operational constraints are established: (25) The first-stage optimization model's constraint set is formed by combining the action logic constraints (S2.2), path mutual exclusion constraints (S2.3), and forbidden node constraints (S2.9) established in S2, with the power flow constraints (S3.5, S3.6) and node voltage constraints (S3.9) established in S3. This constraint set ensures that the number of segment-domain devices installed under different scenarios meets the load reduction requirements, photovoltaic cut-off ratio requirements, and post-cut-off voltage safety requirements. The first-stage optimization model is formed by the first-stage optimization objective in S4.2 and the first-stage constraint set in S4.3. This first-stage optimization model is used to solve for the minimum number of segment-domain devices installed while satisfying all scenario constraints. .

[0101] S4.4: Calculate the minimum number of devices to be installed in the segment region. Then, establish the second-phase optimization objectives. The second phase involves the installation of a fixed-section domain device with a total number of [number missing]. Under these conditions, with the goal of minimizing the amount of distributed photovoltaic power generation cutoff, the installation location of the segmental devices is further optimized. Let the scenario set be... The second-stage optimization objective is then expressed as: (26) Or equivalently expressed as: (27) in, The total number of scenarios is represented by . The segment device configuration scheme with the minimum photovoltaic disconnection amount is obtained by using the second-stage optimization objective function shown in formula (26) or (27) under the condition of fixed number of switches.

[0102] S4.5: In the second phase, establish fixed installation quantity constraints: (28) The net load shedding constraint (S2.7), photovoltaic cut-off ratio constraint (S2.8), action logic constraint (S2.2), path mutual exclusion constraint (S2.3), power flow balance constraint (S3.5, S3.6), and node voltage constraint (S3.9) from the first stage are retained to ensure that the segment-domain device installation locations obtained in the second stage still meet the operational feasibility requirements in all scenarios. The second-stage optimization model is composed of the second-stage optimization objective in S4.4 and the aforementioned second-stage constraint set. The second-stage optimization model is used to fix the minimum installation quantity. Under the given conditions, find the installation location of the segment device with the minimum disconnection amount for distributed photovoltaic systems.

[0103] S4.6: Establish constraints on the number of feeder installations. Assume the number of feeder lines... The maximum number of segment domain devices allowed to be installed is Then we have: (29) in, Indicates feeder The set of nodes on.

[0104] S4.7: For the set of forbidden nodes any node Keep the following constraints unchanged: (30) S4.8: Thus, a segment-domain device configuration collaborative optimization model is formed that simultaneously considers photovoltaic (PV) cut-off ratio constraints and voltage constraints. This model can coordinate low-frequency load shedding requirements, distributed PV retention targets, and post-cut-off voltage safety requirements within the same optimization framework, and provides a model foundation for the subsequent two-stage solution.

[0105] S5: A two-stage solution method is used to solve the segment-domain device configuration collaborative optimization model established in S4. The first stage uses a configuration scale solution method based on scenario iteration, and the second stage uses a configuration position optimization solution method based on logical Benders decomposition, outputting the optimized configuration results of the segment-domain devices. Specifically: S5.1: Construct the initial active scene set for the first phase. In the first phase, it is necessary to construct the initial active scene set across all scenes. The following solution is needed to determine the minimum number of segment-domain devices required to satisfy low-frequency load shedding requirements, photovoltaic cut-off ratio constraints, and voltage constraints. When there are many scenarios, directly establishing complete constraints for all scenarios simultaneously results in a large optimization model size. Therefore, a configuration-scale solution method based on scenario iteration is adopted, starting with the entire scenario set... Selecting some representative scenarios to form an initial set of active scenarios. .

[0106] The representative scenarios include scenarios with significant power deficits, scenarios with high distributed photovoltaic output, scenarios with low net loads, and typical medium-operational scenarios. These representative scenarios are then included in the initial active scenario set. This allows the initial solution process in the first stage to prioritize covering operating conditions with high load reduction requirements, high risk of photovoltaic disconnection, and high risk of voltage over-limit.

[0107] S5.2: Let the first... The set of active scenarios in the round of iteration is ,and Based on the current set of active scenarios , establish the first The current active scenario optimization problem is addressed. This optimization problem uses the first-stage optimization objective of S4.2 as the objective function, and only applies to... The first stage constraint set S4.3 is applied to the scenario in which the objective function can be expressed as: (31) in, This indicates the first phase of scenario iteration rounds. Indicates the first The number of segment-domain devices installed is obtained through round-by-round iteration. For nodes The variable is installed in the segment domain device. Solve the first... After optimizing the current active scenarios, the current installation solution is obtained. and corresponding installation quantity .in, Indicates the first The set of installation locations of segment domain devices obtained by round iteration.

[0108] S5.3: Perform a full-scenario verification of the current installation scheme. (The remaining text appears to be incomplete and possibly contains errors. A more accurate translation would require the full context.) The current installation solution that comes first Substitute all scene sets The system performs verification to determine whether it meets the constraints outlined in S4 regarding net load shedding limits, photovoltaic cut-off ratio, path exclusivity, forbidden node selection, branch power flow balance, node voltage recursion, and node voltage limits in each scenario. If the current installation scheme fails to meet these constraints in a particular scenario, that scenario is identified as a failure scenario. Let the first... The set of failure scenarios identified in the full-scenario verification is as follows .

[0109] S5.4: Update the set of active scenarios in the first phase. If the... The set of failure scenarios obtained by full-scenario verification If the set of failed scenarios is not empty, then the set of failed scenarios is added to the current set of active scenarios, and the set of active scenarios for the next round is obtained: (32) in, Indicates the first The set of failed scenarios identified during the global check is then returned to S5.2, based on the updated set of active scenarios. Re-establish and solve the optimization problem for the current active scenario.

[0110] S5.5: Repeat the iterative process of "solving the current active scene optimization problem - global scene verification - adding failed scenes" from S5.2 to S5.4 until the set of failed scenes is reached. Empty. At this point, the current installation plan... All scenario constraints have been met, the first phase of iteration terminates, and the minimum number of segment domain devices required to satisfy all scenario constraints is output. and its corresponding feasible initial installation scheme .

[0111] S5.6: In the second phase, the number of fixed segment domain devices installed is the minimum number of devices obtained in the first phase. The objective is to minimize the amount of distributed photovoltaic power generation that needs to be cut off.

[0112] S5.7: Let the scene set be... Then the objective function for the second stage can be expressed as: (33) in, For the scene The amount of distributed photovoltaic power cut-off below, This represents the total number of scenes.

[0113] S5.8: In the second stage, the logical Benders decomposition method is used to solve the configuration location optimization problem. The logical Benders decomposition method is an existing decomposition solution approach; this invention applies it to the segment domain device configuration model, decomposing the second-stage problem into a main configuration location problem and scenario sub-problems. The main problem is used to determine the installation location variables of the segment domain device. and in a fixed number of installations Candidate installation schemes are generated under the given conditions; the scenario sub-problems are used to analyze the feasibility of load reduction actions, the amount of distributed photovoltaic power cut-off, and the satisfaction of node voltage constraints for each scenario under the given candidate installation schemes.

[0114] S5.9: The main problem in the second phase satisfies the following fixed installation quantity constraint: (34) It also satisfies the restrictions on prohibited nodes and the upper limit on the number of feeder installations to ensure that the candidate installation schemes meet the configuration range requirements.

[0115] S5.10: For any scenario Given the main problem installation scheme Under these conditions, corresponding scenario sub-problems are established. These sub-problems are used to solve the scenario. The system records feeder-level cutoff actions, segment-level cutoff actions, branch power flow status, and node voltage status, and outputs the installation scheme in the scenario. Photovoltaic cut-off amount And to constrain the degree of breach of contract.

[0116] S5.11: Setting the Scene The overall relaxation amount is Then we have: (35) in, This indicates insufficient slack due to load reduction. Indicates the amount of over-shear relaxation. This indicates the proportion of default slack in the photovoltaic sector. and These represent the relaxation amounts above and below the voltage limit, respectively. , , , , All are non-negative slack variables.

[0117] S5.12: If the current installation scheme has obvious violations in certain scenarios, i.e., the overall slack amount for the corresponding scenario. If the threshold is exceeded, the scenario is identified as a critical scenario and added to the second-stage main problem scenario set to correct the search direction of the main problem. The update relationship of the second-stage main problem scenario set can be represented as: (36) in, Indicates the first The set of main problem scenarios in the round of iteration, Indicates the first A set of key scenarios identified in the analysis of wheel problems.

[0118] S5.13: If the current installation scheme meets the requirements under the verified scenario, then calculate the target value corresponding to the candidate installation scheme based on the distributed photovoltaic power cut-off amount output by the scenario sub-problem: (37) in, Installation plan The corresponding average photovoltaic power cut-off target value is then compared with the target value of the current optimal feasible solution. If... If the result is better than the current optimal target value, then update the optimal feasible installation plan. and the corresponding optimal target value .

[0119] S5.14: After the second phase of iteration, output the current optimal feasible installation plan. .definition For nodes The final segment domain device installation state variables. For any node If node Belongs to the optimal installation location set Then we have: Otherwise: S5.15: In the final configuration scheme of the segment domain device Below, the output shows the low-frequency load shedding action results for each scenario. Among them, the scenario... The best feasible installation solution The net load shedding and photovoltaic disconnection are expressed as follows: and .

[0120] To further illustrate the effectiveness of the method described in this invention, the invention will be described below with reference to the power distribution network topology diagram and optimization results of the embodiments.

[0121] This embodiment uses a distribution network model with high distributed photovoltaic penetration as the research object, and its topology is as follows: Figure 2 As shown, the system comprises 12 feeders in a multi-radial structure. Node types include feeder root nodes, ordinary load nodes, distributed photovoltaic (PV) access nodes, and critical load nodes. Each node's topology is described by its parent-child relationship, and branch parameters are determined by line length, resistance, and reactance. Based on topology data, node load data, and distributed PV data, the downstream load aggregation and downstream PV aggregation of each candidate node can be further calculated, providing a basis for optimizing the installation location of segment-level devices.

[0122] In this embodiment, different photovoltaic (PV) ratio scenarios are set up, and the optimal configuration of segment-domain devices is solved accordingly. In each scenario, the minimum number of segment-domain devices required to meet low-frequency load shedding requirements, PV cut-off ratio constraints, and node voltage constraints is first determined using the method of this invention. Then, under this minimum installation number, the optimal installation node location of the segment-domain devices is further determined. Finally, the average PV cut-off amount, average PV cut-off rate, and PV cut-off ratio when only feeder-level cut-off are used are statistically analyzed for each scenario. The optimization results are shown in Table 1.

[0123] Table 1. Segment device configuration results under different system photovoltaic proportions

[0124] As can be seen from the optimal installation node distribution, the method of this invention can automatically configure the segment-domain devices in positions critical to load reduction and photovoltaic retention based on the source-load distribution characteristics of different feeders. For example, in a medium photovoltaic penetration scenario, the optimization results configure the segment-domain devices at nodes F1-17, F2-15, F6-27, and F6-26; in a higher photovoltaic penetration scenario, this is further extended to relevant nodes on feeder F4. This demonstrates that the method of this invention has the ability to adaptively adjust the installation position according to different photovoltaic penetration levels and topological characteristics.

[0125] From the perspective of photovoltaic (PV) cutoff effectiveness, under the three PV proportion scenarios, the average PV cutoff rates obtained by the method of this invention are 0.27%, 0.81%, and 1.12%, respectively, all significantly lower than the 5% constraint upper limit, indicating that the PV cutoff ratio constraint established by this invention can be effectively met. In contrast, if only the feeder-level cutoff method is used, the PV cutoff ratios in the corresponding scenarios reach 10.78%, 37.44%, and 87.52%, respectively, significantly higher than the average PV cutoff rate under the method of this invention. This result also shows that, under the premise of ensuring low-frequency load shedding requirements, the method of this invention can better retain the distributed PV output in the feeder, achieving the goal of "load shedding and source retention".

[0126] Furthermore, this invention incorporates node voltage constraints during the optimization process. The method of this invention ensures that the segment-domain device configuration scheme, while meeting load reduction requirements and photovoltaic disconnection ratio constraints, still maintains voltage safety in the post-disconnection network operation state, thereby avoiding the problem of passive grid disconnection of distributed photovoltaic systems due to overvoltage.

[0127] In summary, combining Figure 2 As shown in the illustrated distribution network topology and the optimization results in Table 1, the segment-domain device configuration method proposed in this invention, which considers the photovoltaic cut-off ratio and voltage constraints, can effectively obtain the optimal configuration scheme of segment-domain devices that meets the low-frequency load shedding requirements in high distributed photovoltaic distribution network scenarios. Compared with the traditional feeder-level cut-off method, the method of this invention significantly reduces the level of distributed photovoltaic interconnection cut-off while taking into account the voltage safety after cut-off, and has good engineering application value.

[0128] The above embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for configuring segment-domain devices considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding, characterized in that, The segment domain device configuration method includes the following steps: S1: Construct topology data, node source-load data, and operational scenario data containing feeders with a high proportion of distributed photovoltaic access, forming the input data required for segment-domain device configuration optimization; specifically: S1.1: Establish feeder topology and node source load data; S1.2: Calculate the downstream load aggregation and downstream photovoltaic aggregation of the node; S1.3: Extract the feeder path set; based on the radial topology of the feeder, starting from each end node, backtrack along the direction of the parent node to the corresponding feeder root node, forming a path from the feeder root node to the end node; combine all feeder paths into a path set. ; S1.4: Determine the candidate installation locations and prohibited node set for segment domain devices; S1.5: Construct a set of scenarios combining photovoltaic output and power deficit; S2: Establish a low-frequency load shedding model considering photovoltaic power cut-off ratio constraints, and construct the constraint relationship between segment-domain device configuration and load shedding and power source retention objectives; specifically: S2.1: Define segment domain device installation variables, segment domain action variables, and physical removal variables; S2.2: Establish logical constraints between the installation state and the action state; S2.3: Establish feeder-level cutoff variables; S2.4: Establish mutual exclusion constraints for feeder paths; S2.5: Establish the expression for net load reduction in the scenario; S2.6: Establish the expression for the photovoltaic cut-off amount in the scenario; S2.7: Establish net load reduction constraints; S2.8: Establish photovoltaic cut-off ratio constraints; S2.9: Establish constraints on candidate installation locations and installation quantity; S2.10: From S2.1 to S2.9, a low-frequency load shedding model considering the photovoltaic cut-off ratio constraint is formed; S3: Establish a low-frequency load shedding model considering voltage constraints, incorporating feeder power flow reconfiguration and node voltage changes after segment disconnection into the analysis; specifically: S3.1: Analysis of the feeder power flow reconstruction mechanism after segment domain removal; S3.2: Establish the correlation between the physical charged state of the node and the resection action; S3.3: Establish the equivalent net reactive load expression for the node; S3.4: Establish branch power flow variables, including branch active power flow variables. and branch reactive power flow variables ; S3.5: Establish active power flow balance constraints for branch lines; S3.6: Establish reactive power flow balance constraints for branch paths; S3.7: Establish node voltage variables; S3.8: Establish node voltage recursive constraints; S3.9: Establish upper and lower limit constraints for node voltages; S3.10: Establish coupling constraints between the cut-off action and the power flow and voltage relationship; convert the node's physical charged state variables... Coupled with the branch power flow and node voltage recursion relationship; S3.11: From S3.1 to S3.10, a low-frequency load shedding model considering voltage constraints is formed; S4: Based on the low-frequency load shedding model considering photovoltaic (PV) cutoff ratio constraints built in S2 and the low-frequency load shedding model considering voltage constraints built in S3, a segment-domain device configuration collaborative optimization model considering both PV cutoff ratio constraints and voltage constraints is constructed; specifically: S4.1: Construct a segment-domain device configuration collaborative optimization model that simultaneously considers photovoltaic cut-off ratio constraints and voltage constraints; S4.2: Establish the first-stage optimization objectives; S4.3: In the first stage, construct the first stage optimization model and solve for the minimum number of segment domain devices to be installed. ; S4.4: Calculate the minimum number of devices to be installed in the segment region. Then, establish the second-stage optimization objectives; S4.5: In the second stage, construct the second stage optimization model to solve for the installation location of the segment device with the minimum disconnection amount of distributed photovoltaic power generation. S4.6: Establish constraints on the number of feeder installations; S4.7: For the set of forbidden nodes any node To ensure that critical load nodes, feeder root nodes, and other nodes that do not meet the installation conditions are not selected as the configuration locations for segment area devices; S4.8: Form a two-stage segment domain device configuration collaborative optimization model; S4.9: Achieve specific objectives by configuring a collaborative optimization model using a two-stage segment domain device; S4.10: From S4.1 to S4.9, a segment-domain device configuration collaborative optimization model is formed that simultaneously considers photovoltaic cut-off ratio constraints and voltage constraints; S5: A two-stage solution method is used to solve the segment domain device configuration collaborative optimization model established in S4. The first stage adopts a configuration scale solution method based on scenario iteration, and the second stage adopts a configuration position optimization solution method based on logical Benders decomposition, and outputs the optimized configuration results of segment domain devices.

2. The segmental device configuration method considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding according to claim 1, characterized in that, Specifically, S1 refers to: S1.1: Establish a node set based on the distribution feeder topology, node load, distributed photovoltaic access capacity, and line parameters. Feeder set Branch road set and scene collection ;in, Indicates the node number. Indicates the feeder number. Indicates the scene number; for any node Record its feeder, parent node, child node, and active load. The base value for distributed photovoltaic installed capacity or equivalent output is and node type identifier; for any branch The system records the first node, last node, resistance, and reactance parameters of each node. The node type identifier is used to distinguish between feeder root nodes, ordinary load nodes, distributed photovoltaic access nodes, and important load nodes. Among them, the feeder root node refers to the starting node where the feeder connects to the upper-level power grid or distribution bus; the parent node refers to the node located upstream of the node in the feeder topology and directly connected to it; the child node refers to the node located downstream of the node in the feeder topology and directly connected to it; the last node refers to the node that has no downstream child nodes; the feeder radial topology structure refers to a tree-like power supply structure that starts from the feeder root node and extends step by step along the parent-child node relationship to each last node. S1.2: For any node Then the node Downstream load aggregation and downstream photovoltaic polymerization volume It is obtained through the following recursive method: （1） in, Represents a node The set of child nodes; Indicates at node The downstream load corresponding to the execution of a segment domain cut-off; Indicates at node When the segment domain is cut off, the downstream distributed photovoltaic capacity may be cut off along with it; To represent at the node The downstream load corresponding to the execution of a segment domain cut-off; To represent at the node When the segment domain is cut off, the downstream distributed photovoltaic capacity may be cut off along with it; If node If it is an end node, then If it is empty, then: （2） S1.3: For any path , Indicates the path number. Indicates the first A sequence of nodes from the root node to the end node of a feeder; a set of paths. Used for subsequently establishing path mutual exclusion constraints; S1.4: Establish a set of prohibited nodes based on the feeder topology, node type identifiers, and engineering installation conditions. Nodes that are not allowed to install segment domain devices will be added to the set of prohibited nodes. In the middle; the set of forbidden nodes. The remaining nodes are used as candidate installation locations for the segment domain device, resulting in a set of candidate installation nodes; S1.5: Construct photovoltaic output scenarios and power deficit scenarios; for any scenario Let the photovoltaic output coefficient be... Power deficit is ;in, Representing a scene The ratio of distributed photovoltaic power output to its installed capacity or equivalent power base value. Representing a scene The system needs to bear the low-frequency load shedding power deficit; different photovoltaic output levels and different power deficit levels are combined to form a "photovoltaic output - power deficit" combined scenario. That is, we get the scene set S.

3. A segmental device configuration method considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding according to claim 2, characterized in that, In S1.4, the nodes to be banned include the following types: (1) Feeder root node; (2) Important load nodes and upstream path nodes, namely, nodes marked as important loads or critical loads in the node type identifier and the nodes that the node passes through when traversing back to the feeder root node along the direction of the parent node; (3) Nodes that do not meet the equipment installation requirements; (4) Nodes with excessively high downstream photovoltaic capacity, i.e., nodes where the ratio of downstream photovoltaic aggregation to downstream load aggregation exceeds a preset threshold; the preset threshold is 0.

35. (5) Nodes with excessively low downstream load, i.e., nodes whose downstream load aggregation is lower than the preset minimum load cut-off threshold; the preset minimum load cut-off threshold is 50kW.

4. A segmental device configuration method considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding according to claim 3, characterized in that, Specifically, S2 is: S2.1: The set of nodes obtained based on S1 is Let the set of scenarios be S; for any node Define segment domain device installation variables for: （3） For any scenario Define segment domain action variables for: （4） S2.2: For any node and any scene ,have: （5） At the same time, the following logical linearization constraints are established: （6） in, Represents the node In the scene Whether the physical resection variable forms an actual segment domain resection action; when the node When a segmentation device is installed at a location and the device performs a cutting operation... ,otherwise ; S2.3: For the feeder set Any feeder and any scene Define feeder-level cutoff variables for: （7） The feeder-level cutoff variable is used to characterize the traditional feeder-level cutoff action, and together with the segment-domain cutoff action, it constitutes the set of low-frequency load shedding actions. By setting both the feeder-level cutoff variable and the segment-domain cutoff variable at the same time, the two types of actions, feeder-level cutoff and segment-domain cutoff, are described in a unified manner. S2.4: For any path in the feeder and any scenario Establish path mutual exclusion constraints: （8） in Representing a path The number of the feeder to which it belongs. Representing a scene Next path The feeder-level cutoff variable of the corresponding feeder; S2.5: For any scenario Set up feeder The total load is Total photovoltaic power is ;node The downstream load polymerization rate is Downstream photovoltaic polymerization volume The photovoltaic power output coefficient is Then the scene The net load reduction is formed by the combined feeder-level and segment-level cutoffs. Represented as: （9） Feeder-level cut-off corresponds to the simultaneous disconnection of the load and photovoltaic power of the entire feeder; segment-level cut-off corresponds to the simultaneous disconnection of the load and photovoltaic power of the downstream area of ​​the node; the net load reduction is the amount of load cut-off minus the photovoltaic power output of the synchronously cut-off. S2.6: For any scenario Distributed photovoltaic power cut-off volume formed by feeder-level cut-off and segment-level cut-off Represented as: （10） This formula is used to characterize the scene. The amount of distributed photovoltaic power generation disconnected due to low-frequency load shedding; S2.7: Setting the Scene The power deficit that the downstream system needs to bear is Let the upper limit of the allowed overcut ratio be... To ensure that low-frequency load shedding actions meet the system's load reduction requirements while avoiding a net load shedding amount significantly exceeding the actual demand, for any scenario... The following net load reduction constraint is established: （11） S2.8: Limit the proportion of distributed photovoltaic (PV) power cut-off during low-frequency load shedding; set the upper limit of the allowed PV power cut-off proportion as follows: For any scenario Establish the photovoltaic cut-off ratio constraint, as shown in formula (12): （12） The cleft resection ratio constraint is further linearized as follows: （13） By constraining the photovoltaic cut-off ratio, it is ensured that the proportion of distributed photovoltaic cut-off is controlled within a preset range while meeting the low-frequency load reduction requirements. S2.9: For the set of forbidden nodes any node Establish the selection restriction constraint, as shown in formula (14): （14） To limit the overall configuration scale of segment domain devices, an installation quantity constraint is established; let the total number of segment domain devices installed in the system be... Then we have: （15） When optimizing the minimum installation size later, As an optimization target; S2.10: The low-frequency load shedding model is based on the feeder topology and uses the segment-domain device installation variables, action variables, and physical cut-off variables as core decision variables. By uniformly describing the feeder-level cut-off and segment-domain cut-off actions, it constructs a low-frequency load shedding model that satisfies power deficit constraints, overcut constraints, path mutual exclusion constraints, and photovoltaic cut-off ratio constraints, thereby realizing segment-domain device configuration and load shedding action modeling oriented towards the goal of "load shedding and source retention".

5. A segmental device configuration method considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding according to claim 4, characterized in that, Specifically, S3 is: S3.1: Because the segment disconnection action will change the retention status of the load and distributed photovoltaic in the feeder, therefore in a given scenario Below, the equivalent net load of each node in the feeder will change with the disconnection operation; for any node Assume its load active power The base value for distributed photovoltaic installed capacity or equivalent output is Scene The photovoltaic output coefficient is Then, under the action of segment domain resection, the node Equivalent net active load Represented as: （16） in, For nodes In the scene The physical charged state variables under the node; when the node When power is maintained, When node When power is lost due to feeder level cutoff or section cutoff ; S3.2: Establish physical charged state variables based on feeder topology. The mapping relationship between the node and the cutoff variable; for any node and any scenario If node The feeder is ,in Represents a node The node is the number of the feeder it belongs to. The physical charged state is affected by the feeder level cutoff variable. and from the feeder root node to the node Physical cut-off variables along the upstream path have a combined effect; through the node's physical charged state variables. This provides a unified representation of the retained state of nodes after removal and is used for subsequent power flow and voltage constraint modeling. S3.3: For any node Let its load reactive power be Then the scene Next node Equivalent net reactive load Represented as: （17） When reactive load data for a node is missing, it can be determined based on the load power factor or the typical ratio of active to reactive power. Perform equivalent estimation to form the equivalent net reactive load expression for each node; S3.4: Let the set of feeder branches be... For any branch and any scenario Define the active power flow variables of the branch. and branch reactive power flow variables , respectively used to represent scenes Lower branch road Active and reactive power flows are defined; the positive direction of branch power flow is defined as from the root node of the feeder to the end node of the feeder. S3.5: For any branch and any scenario ,node The active power flow of the upstream branch should be equal to that of the node. The equivalent net active power load is the sum of the active power flow of its downstream branches. Therefore, the active power flow balance constraint of the branches is established, as shown in formula (18): （18） in, Represents a node The set of child nodes For nodes Child node number; For the scene Lower branch road The above is from the node Pointing to node The meritorious trend; For the scene Lower branch road The above is from the node Pointing to node The meritorious trend; Represents a node In the scene The equivalent net active load under the following conditions; S3.6: For any branch and any scenario ,node The reactive power flow of the upstream branch should be equal to that of the node. The equivalent net reactive load is summed with the reactive power flow of its downstream branches to establish branch reactive power flow balance constraints: （19） in, For the scene Lower branch road The above is from the node Pointing to node The unproductive current; For the scene Lower branch road The above is from the node Pointing to node The unproductive current; Represents a node In the scene The equivalent net reactive power load under the following conditions; S3.7: For any node and any scenario Define node voltage variables , used to represent nodes In the scene The square of the voltage amplitude or equivalent voltage quantity; for the feeder root node Its voltage is given by the upstream power grid and is denoted as: （20） in, Indicates the root node of the feeder In the scene The node voltage below; The rated voltage of the feeder root node; S3.8: Set up branch roads The resistance and reactance are respectively and For any branch and any scenario Based on the linearized power flow model of the distribution network, the node voltage recursive constraint is established as shown in formula (21): （21） in Represents a node In the scene The node voltage below; S3.9: To ensure that the feeder operation meets voltage safety requirements after segment disconnection, for any node... and any scenario Establish upper and lower limit constraints for node voltages, as shown in formula (22): （22） in, and Representing nodes respectively Permissible lower and upper voltage limits; S3.10: For any branch and any scenario If downstream nodes Keep it charged, that is If the power flow constraints and voltage recursion relationships corresponding to that branch are in effect, then the power flow constraints and voltage recursion relationships for that branch will take effect normally; if the downstream node Power has been lost, that is If the active and reactive power flows of the branch are restricted to zero, the corresponding voltage recursion relationship is relaxed; the active and reactive power flows should be restricted to zero, and the corresponding voltage recursion relationship of the branch should be relaxed. Establish the following coupling constraints between branch power flow and node energized states: （23） in, and The large M constants represent the active power flow and reactive power flow, respectively; through coupling constraints, when At that time, the branch road The meritorious trend and the trend of no effort Limited to zero; when At that time, the power flow in the branch can vary within the allowable range; To ensure that the voltage recursion relationship is effective when nodes are energized and does not constrain the model when nodes are de-energized, the following conditional voltage recursion constraint is established: （24） in, For the large M constant corresponding to the voltage recursion constraint; when When the above constraints degenerate into nodal voltage recursive equations; when At this time, the constraint is relaxed to avoid applying a meaningless voltage recursion to the removed area; S3.11: The low-frequency load shedding model is based on the feeder power flow reconstruction mechanism after segment disconnection. It characterizes the voltage change characteristics of the feeder after segment disconnection by using the node injected power relationship, branch power flow balance relationship, node voltage recursion relationship, and node voltage upper and lower limit constraints. This incorporates the risk of node voltage exceeding the limit after disconnection into the low-frequency load shedding analysis, providing a foundation for the subsequent construction of a segment device configuration model that simultaneously considers photovoltaic disconnection ratio constraints and voltage constraints.

6. A segmental device configuration method considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding according to claim 5, characterized in that, Specifically, S4 is: S4.1: Based on the low-frequency load shedding model in S2 that considers the photovoltaic cut-off ratio constraint, the node injection power relationship, branch power flow balance relationship, node voltage recursion relationship and node voltage upper and lower limit constraints in S3 are introduced. The power deficit constraint, overcut constraint, feeder path mutual exclusion constraint, action logic constraint, photovoltaic cut-off ratio constraint and node voltage constraint are unified into the same optimization framework to construct a segment domain device configuration collaborative optimization model that considers both photovoltaic cut-off ratio constraint and voltage constraint. S4.2: Minimize the total number of segment-domain devices installed as the first-stage optimization objective; Assume the total number of segment domain devices installed in the system is The first-stage optimization objective is expressed as: （25） in, The variable for installing segment-domain devices is defined; using the first-stage optimization objective function shown in formula (25), the minimum number of segment-domain devices installed can be obtained under the premise of satisfying all scenario constraints, denoted as... ; S4.3: Establish the following operational constraints: （26） The first-stage optimization model's constraint set is formed by combining the action logic constraints, path mutual exclusion constraints, and forbidden node constraints established in S2, with the power flow constraints and node voltage constraints established in S3. The first-stage optimization model is composed of the first-stage optimization objective in S4.2 and the first-stage constraint set in S4.

3. This first-stage optimization model is used to solve for the minimum number of segment-domain devices to be installed while satisfying all scenario constraints. ; S4.4: Total number of devices installed in the fixed segment area during the second phase Under the condition of minimizing the amount of distributed photovoltaic power generation cutoff, the installation location of the segmental device is further optimized; let the scenario set be... The second-stage optimization objective is then expressed as: （27） Or equivalently expressed as: （28） in, The total number of scenarios is represented by the second-stage optimization objective function shown in formula (27) or (28), under the condition of a fixed number of switches, the configuration scheme of the segment device with the minimum photovoltaic disconnection amount is obtained. S4.5: In the second phase, establish fixed installation quantity constraints: （29） The net load shedding constraints, photovoltaic cut-off ratio constraints, action logic constraints, path mutual exclusion constraints, power flow balance constraints, and node voltage constraints from the first stage are retained to ensure that the segment-domain device installation locations obtained in the second stage still meet the operational feasibility requirements in all scenarios. The second-stage optimization model is composed of the second-stage optimization objective in S4.4 and the aforementioned second-stage constraint set. The second-stage optimization model is used to fix the minimum installation quantity. Under the given conditions, find the installation location of the segmental device with the minimum disconnection amount of distributed photovoltaic power generation; S4.6: For any feeder Considering that there is an engineering upper limit to the number of segment devices that can be installed on different feeders, a constraint is established on the number of feeder installations; assuming the feeder... The maximum number of segment domain devices allowed to be installed is Then we have: （30） in, Indicates feeder The set of nodes on the feeder; by constraining the number of feeder installations, it is possible to avoid excessive concentration of segment-domain devices on a single feeder, thereby improving the engineering rationality of the configuration results; S4.7: For the set of forbidden nodes any node Keep the following constraints unchanged: （31） Ensure that critical load nodes, feeder root nodes, and other nodes that do not meet the installation conditions are not selected as the configuration locations for section area devices, thereby ensuring that the section area device configuration scheme meets the actual operating requirements; S4.8: Combine the first-stage optimization objective and the second-stage optimization objective with the corresponding constraint set to form a two-stage segment domain device configuration collaborative optimization model; S4.9: Through a two-stage segment-domain device configuration collaborative optimization model, the following objectives are achieved: reduce the number of segment-domain devices installed while meeting the low-frequency load reduction requirements; reduce the level of distributed photovoltaic interconnection disconnection under the condition of a fixed number of installations; and at the same time, ensure that the feeder operation status after disconnection meets the voltage safety requirements by introducing node voltage constraints.

7. A segmental device configuration method considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding according to claim 6, characterized in that, In S4.8, the two-stage segment domain device configuration collaborative optimization model is used to determine the minimum number of segment domain devices to meet all scenario constraints in the first stage, and to further optimize the configuration position of segment domain devices under a fixed number of installations, so as to simultaneously take into account the scale of the transformation, photovoltaic retention capacity and post-cut-off operation safety.

8. A segmental device configuration method considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding according to claim 7, characterized in that, The segment-domain device configuration collaborative optimization model takes the segment-domain device installation variables, action variables, physical disconnection variables, power flow and voltage variables as core decision variables. By unifying and coordinating load reduction requirements, photovoltaic retention targets and voltage safety requirements, it establishes a segment-domain device optimization configuration framework for high-distribution photovoltaic feeders.

9. A segmental device configuration method considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding according to claim 8, characterized in that, Specifically, S5 is: S5.1: Construct the initial active scene set for the first phase; in the first phase, it is necessary to complete the entire scene set. The following solution is needed to determine the minimum number of segment-domain devices required to satisfy low-frequency load shedding requirements, photovoltaic cut-off ratio constraints, and voltage constraints. ; When there are many scenarios, directly establishing complete constraints for all scenarios simultaneously results in a large optimization model size. Therefore, a configuration-scale solution method based on scenario iteration is adopted, starting with the entire scenario set. Selecting some representative scenarios to form an initial set of active scenarios. ; S5.2: Let the first... The set of active scenarios in the round of iteration is ,and Based on the current set of active scenarios , establish the first Optimization issues for currently active scenarios; The optimization problem uses the first-stage optimization objective of S4.2 as the objective function, and only applies to... The scenario in question is subject to the first-stage constraint set of S4.3, and its objective function is expressed as: （32） in, This indicates the first phase of scenario iteration rounds. Indicates the first The number of segment-domain devices installed is obtained through round-by-round iteration. For nodes Variables installed in the segment domain device; Solve the first After optimizing the current active scenarios, the current installation solution is obtained. and corresponding installation quantity ;in, Indicates the first The set of installation locations of segment-domain devices obtained from round iteration; S5.3: Perform full-scenario verification of the current installation scheme; [The remaining text appears to be incomplete and requires further context.] The current installation solution that comes first Substitute all scene sets The system performs verification to determine whether it meets the constraints described in S4 regarding net load reduction limits, photovoltaic cut-off ratio, path mutual exclusion, forbidden node, branch power flow balance, node voltage recursion, and node voltage limits in each scenario. If the current installation scheme fails to meet the above constraints in a certain scenario, then that scenario is identified as a failure scenario. Let the first... The set of failure scenarios identified in the full-scenario verification is as follows ; S5.4: Update the set of active scenarios in the first phase; if the... The set of failure scenarios obtained by full-scenario verification If the set of failed scenarios is not empty, then the set of failed scenarios is added to the current set of active scenarios, and the set of active scenarios for the next round is obtained: （33） in, Indicates the first The set of failed scenarios identified in the global check is then returned to S5.2, based on the updated set of active scenarios. Re-establish and solve the optimization problem for the current active scenario; S5.5: Repeat the iterative process of S5.2 to S5.4 until the set of failure scenarios is reached. Empty; at this point, the current installation scheme... All scenario constraints have been met, the first phase of iteration terminates, and the minimum number of segment domain devices required to satisfy all scenario constraints is output. and its corresponding feasible initial installation scheme ; S5.6: In the second phase, the number of fixed segment domain devices installed is the minimum number of devices obtained in the first phase. Furthermore, a configuration location optimization solution method based on logical Benders decomposition is adopted to optimize the installation location of the segment domain device; S5.7: Let the scene set be... Then the objective function for the second stage is expressed as: （34） in, For the scene The amount of distributed photovoltaic power cut-off below, Total number of scenes; S5.8: In the second stage, the logical Benders decomposition method is used to solve the configuration location optimization problem; S5.9: The main problem in the second phase satisfies the following fixed installation quantity constraint: （35） It also satisfies the restrictions on prohibited nodes and the upper limit on the number of feeder installations, ensuring that the candidate installation schemes meet the configuration range requirements; S5.10: For any scenario Given the main problem installation scheme Under the given conditions, corresponding scenario subproblems are established; whereby the subproblems are used to solve the scenario. The system records feeder-level cutoff actions, segment-level cutoff actions, branch power flow status, and node voltage status, and outputs the installation scheme in the scenario. Photovoltaic cut-off amount and the degree of constraint on default, among which Indicates in the scene Installation plan The amount of photovoltaic power removed; S5.11: Introduce slack variables in the scenario subproblem, let the scenario... The overall relaxation amount is Then we have: （36） in, This indicates insufficient slack due to load reduction. Indicates the amount of over-shear relaxation. This indicates the proportion of default slack in the photovoltaic sector. and These represent the upper voltage limit and lower voltage limit relaxation amounts, respectively. , , , , All are non-negative slack variables; S5.12: If the current installation scheme There are obvious defaults in certain scenarios, namely the overall slack in the corresponding scenarios. If the threshold is exceeded, the scene is identified as a critical scene and added to the second-stage main problem scene set to correct the search direction of the main problem; the update relationship of the second-stage main problem scene set is expressed as follows: （37） in, Indicates the second phase iteration round. Indicates the first The set of main problem scenarios in the round of iteration, Indicates the first A set of key scenarios identified in the analysis of wheel problems; S5.13: If the current installation scheme meets the requirements under the verified scenario, then calculate the target value corresponding to the candidate installation scheme based on the distributed photovoltaic power cut-off amount output by the scenario sub-problem: （38） in, Installation plan The corresponding average photovoltaic power cut-off target value; this target value Compare with the target value of the current best feasible solution; if If the result is better than the current optimal target value, then update the optimal feasible installation plan. and the corresponding optimal target value ; S5.14: After the second phase of iteration, output the current optimal feasible installation plan. And determine the final optimized configuration result of the segment domain device based on the installation plan; define For nodes The final segment domain device installation state variables; for any node If node This is the optimal and feasible installation solution. Then we have: Otherwise: ; This results in the final configuration scheme of the segment domain device that satisfies all scenario constraints; S5.15: Optimal feasible installation scheme for segment-domain devices Below, output the low-frequency load shedding action results for each scenario; for any scenario The results of low-frequency load shedding actions include at least feeder-level cutoff actions, segment-level cutoff actions, net load shedding for the scene, and distributed photovoltaic cutoff; among which, the scene The best feasible installation solution The net load shedding and photovoltaic disconnection are expressed as follows: and ; S5.16: From S5.1 to S5.15, complete the two-stage solution of the collaborative optimization model and output the optimized configuration results of the segment domain device that satisfy the photovoltaic cut-off ratio constraint and voltage constraint.

10. A segmental device configuration method considering photovoltaic cut-off ratio and overvoltage constraints in low-frequency load shedding according to claim 9, characterized in that, In S5: In S5.1, representative scenarios include scenarios with large power deficits, scenarios with high distributed photovoltaic output, scenarios with low net loads, and typical operating scenarios. In S5.6, the second stage aims to minimize the amount of distributed photovoltaic disconnection, and searches for a better installation location scheme for the segmental device under the condition of a fixed number of installations. In S5.8, the logical Benders decomposition method is as follows: the second-stage problem is decomposed into the main problem of configuration location and the sub-problem of scene; The main problem is used to determine the installation location variable of the segment domain device. and in a fixed number of installations Candidate installation schemes are generated under the given conditions; the scenario sub-problems are used to analyze the feasibility of load reduction actions, the amount of distributed photovoltaic power cut-off, and the satisfaction of node voltage constraints for each scenario under the given candidate installation schemes.

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