Life line differentiation planning method for improving toughness of urban power grid

Abstract

The invention discloses a lifeline differentiation planning method for improving the toughness of an urban power grid, and belongs to the technical field of power grid planning methods. A lifeline differentiation planning method for improving toughness of an urban power grid comprises the following steps: constructing a local power grid limit viability quantitative index, and quantifying power supply guarantee levels of loads of different importance levels in an extreme fault scene; based on an improved commodity flow model, multi-path power supply topology constraints suitable for loads of different importance degrees are established, and the requirement of lifeline loads for power supply path redundancy is guaranteed; and establishing an urban power grid lifeline differentiation planning model, and realizing optimal construction of a multi-level local power grid through local power grid boundary division, resource allocation and level constraint. By adopting the lifeline differentiation planning method for improving the toughness of the urban power grid, the problem that the grade load differentiation guarantee cannot be well realized under the limited resource condition by the existing method can be solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power grid planning method, and particularly relates to a life line differentiated planning method for improving the resilience of urban power grid. BACKGROUND

[0002] With the continuous growth of urban load, the urban power grid gradually presents the characteristics of high density and complexity. In order to control the short-circuit current level while ensuring power supply reliability, the power grid is usually divided into several independent operation zones in actual operation. Each zone takes a 500kV substation as a power receiving hub, supplies power downward through a 220kV main channel, and builds a network structure with a 220kV ring network as the backbone in the zone. The zonal power grid often has a certain scale of local power supply, and realizes flexible inter-supply through multiple voltage levels and a large number of interconnection lines, so that it has the potential to operate in island mode when the upper power supply channel is damaged. To realize the ultimate survival in island mode, it is necessary to have a certain local resource basis, and to differentially reinforce the key channels in view of the possible multi-point faults, so as to build a strong local power grid that can guarantee important loads.

[0003] In recent years, power grid resilience planning has gradually expanded from large power grids and low-voltage distribution networks to urban zonal power grids, and the research methods have gradually developed from single heuristic methods to multi-stage stochastic optimization, hierarchical robust optimization and flexible adaptive methods, paying more attention to the unity of power grid operation feasibility and economy under various extreme scenarios. In terms of resilience improvement measures, it is no longer limited to the single enhancement of lines or power sources, but emphasizes the collaborative optimization of lines, substations, power sources and flexible resources (such as energy storage and controllable loads) to ensure the dynamic recovery and continuous power supply capability of the network. When dealing with different extreme event threats, the new resilience planning framework generally introduces scenario set coverage or probability modeling to improve the universality and robustness of the scheme.

[0004] Currently, multi-path power supply for important loads has been included in the core framework of power grid resilience planning: general important users should have the ability to be supplied by two independent power sources, and one of them should be a life line channel; special important users should have at least three independent power sources and form two or more life line channels. However, the existing planning methods still have deficiencies in the integration of differentiated protection for different levels of loads, and it is difficult to fully meet the actual needs of urban power grid resilience improvement, so there is an urgent need for a differentiated life line planning method for urban power grid that can balance the differentiated protection of different levels and resilience optimization. SUMMARY

[0005] The purpose of the present application is to provide a life line differentiated planning method for improving the resilience of urban power grid, which solves the problem that the existing method cannot well realize the differentiated protection of different levels of loads under limited resource conditions.

[0006] To achieve the above objectives, this invention provides a lifeline differentiation planning method for improving the resilience of urban power grids, comprising the following steps: S1. Construct quantitative indicators for the extreme survivability of local power grids to quantify the power supply guarantee level of loads of different importance levels under extreme fault scenarios; S2. Based on the improved commodity flow model, establish multi-path power supply topology constraints applicable to loads of different importance levels to ensure the redundancy requirements of power supply paths for lifeline loads; S3. Establish a differentiated planning model for urban power grid lifelines, and achieve optimal construction of multi-level local power grids through local power grid boundary division, resource allocation and hierarchical constraints.

[0007] Preferably, in S1, the quantitative index of the local power grid's extreme survivability is the extreme survivability index. The extreme survivability index comprehensively considers the load supply and demand status, the load importance weight, and the reinforcement ratio of supply guarantee channels. for: ; In the formula, Indicates important load cl Is it powered by the power supply? The guarantee is 1 if it is not guaranteed, and 0 otherwise. Indicates important load cl Importance weight; Indicates important load cl Power supply The proportion of guaranteed channels has been strengthened.

[0008] Preferably, in S2, the multi-power supply topology constraint is: ; ; ; ; ; ; ; In the formula, All are node indexes; Index for critical loads; For route indexing; For power index; Indicates all upstream power supplies s / Upstream substation b The set of power supply paths for critical loads; Indicates the upstream power supply s / Upstream substationb gather; Represents a set of important users; Indicates user j The set of power supply path quantity requirements; Represents the set of all lines; Represents the set of power grid nodes; Represents a set of critical loads; Indicates the line The risk factor; Indicates available upstream power supply s / Upstream substation b Ensure critical loads cl Power supply path com Does it pass through the line? The value is 1 if the condition is met, otherwise it is 0. Represents a node j Does it need to come from the power supply path? com Power supply, binary variable; Represents a node j The total demand for the number of power supply paths; Indicates the line Whether to create a new binary variable; Indicates the line Is an upgrade needed? Indicates available upstream power supply s / Upstream substation b Through the power supply path com Supplying electricity to key user nodes; It is a very large positive real number.

[0009] Preferably, in S3, the objective function of the differentiated planning model for urban power grid lifelines is to maximize the critical load's ultimate survivability and the guaranteed power supply margin. The objective function is: ; In the formula, Indicates important load Is it powered by the power supply? Assure; For important loads Importance coefficient; Indicates power supply Ensure critical loads The proportion of pathway reinforcement; Indicates power supply The guaranteed power; For important loads The load capacity; Index for critical load nodes.

[0010] Preferably, in the S3, the planning cost constraint of the urban power grid lifeline differentiated planning model is: ; ; In the formula, represents the total cost required for planning; represents the upper limit of the planning budget cost; , , respectively represent the new construction cost of the line, the backup power supply, and the transformer substation; , , respectively represent the upgrading cost of the line, the backup power supply, and the transformer substation; , , are binary variables, respectively indicating whether the line, the backup power supply, and the transformer substation are newly added; , , are binary variables, respectively indicating whether the line, the backup power supply, and the transformer substation are upgraded.

[0011] Preferably, in the S3, the local power grid limit survival demand constraint of the urban power grid lifeline differentiated planning model includes commodity flow constraints, voltage matching constraints, power balance constraints, and power supply capacity constraints. The commodity flow constraint is: ; ; In the formula, is whether the power supply supplies power to the node ; is a known variable, indicating the virtual demand of a non-root node; is a continuous variable, indicating the virtual power flow size of the line in the local power grid centered on the power supply ; is a continuous variable, indicating the virtual power flow size of the line in the local power grid centered on the power supply ; is a binary variable, indicating whether the line i,j is in an upgraded state; The voltage matching constraint is: ; ; In the formula, is a node set, is a load The voltage level at which it is located, power supply The voltage level at which it is located, It is a line The voltage level at which it is located; The power balance constraint is: ; In the formula, , These represent the loads supplied by power source S. l The flow , (i,j) The active power of the line, Indicates load l active power, This indicates that power source S supplies power to the load. l The active power; The power supply capacity constraint is: ; In the formula, Let be the active power of power source s.

[0012] Preferably, in S3, the expression for the local power grid's extreme survival requirement constraint is: ; ; ; ; ; ; ; ; ; ; ; ; ; ; In the formula, Indicates load l The voltage level to which it belongs; This is a binary variable representing the power supply. s Has it been added / upgraded? For power supply s Maximum active power; For power supplys To load l The length of the power supply; Indicates the length of the line; A binary variable representing the load. l Power supply s When powered, the line (i,j) Is it electrified? Indicates if the line (i,j) If the line is in an upgrade state, the weight of the line length is 1; otherwise, it is 0. Indicates load l At the level c The number of backup power supplies; A collection of substations to be built; , , These represent the sets of top-priority users, first-priority users, and second-priority users, respectively.

[0013] Preferably, in S3, the logical expression of the planning variables and the budget constraint expression of the differentiated planning model for urban power grid lifelines are as follows: ; ; ; ; ; ;

[0014] In the formula, , , These represent the sets of lines, power sources, and substations to be newly constructed; , , These represent sets of lines, power sources, and substations that do not require new construction. , , These represent the sets of upgraded lines, power sources, and substations, respectively. This is a binary variable representing a substation. b Has it been upgraded? For substation b With nodes i The status of the lines between them For nodes i With substation b The status of the lines between them.

[0015] Preferably, in S3, the local power grid dynamic response capability requirement constraint of the differentiated planning model for urban power grid lifelines is: ; ; ; ; ; In the formula, , These are the ROCOF after the disturbance and the safety limit, respectively. This is the frequency reference value; It is the change in frequency; For local power grid The power deficit; For local power grid The load shedding power; For local power grid The equivalent inertia; , They represent synchronous generator units. Inverter interface power supply The inertial constant; , They represent synchronous generator units. Inverter interface power supply Does it belong to a local power grid? ; Synchronizer i PFR power; Inverter interface power supply n FFR power; Indicates the maximum allowable frequency deviation of the system; , These represent the complete response time of the inverter interface power supply and the synchronous generator, respectively. For local power grid m The total fast frequency response power that the inverter interface power supply can provide; For local power grid m The total primary frequency regulation power that a medium-synchronous generator unit can provide; This refers to the active power deficit that occurs after grid disturbances. This is a binary variable representing the inverter interface power supply. The operational status; This is a binary variable representing a synchronous generator unit. The operational status.

[0016] Preferably, in step S3, the urban power grid lifeline differentiated planning model is solved using the commercial solver GUROBI to obtain a resilience planning method.

[0017] The advantages and positive effects of the lifeline differentiation planning method for improving urban power grid resilience described in this invention are as follows: This invention fully integrates multiple factors such as important load classification and lifeline differentiation construction, which enhances the self-recovery capability of local power grids while ensuring power grid resilience; it also takes into account the strategy of strengthening power redundancy paths and resource sharing among important nodes, so that important loads can still be continuously powered in the event of a sudden event or large-scale power failure, effectively mitigating the impact of power outages on social functions and economic systems, and achieving differentiated protection of load levels.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] (i,j) This is a flowchart of the resilience planning method of the present invention; Figure 1 This is a diagram of the urban zonal power grid topology according to an embodiment of the present invention; Figure 2 This is a diagram showing the planning strategy results of an embodiment of the present invention. Detailed Implementation

[0020] In this application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any inconsistency, the meaning set forth in this specification or derived from the content described herein shall prevail. Furthermore, the terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit the scope of this application.

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figure 3 As shown, a differentiated planning method for improving the resilience of urban power grids includes the following steps: S1. Construct quantitative indicators for the extreme survivability of local power grids to quantify the power supply guarantee level of loads of different importance levels under extreme fault scenarios.

[0023] In extreme events, local urban power grids often need to independently bear the responsibility of supplying power to critical loads. Accurately characterizing their extreme survivability is crucial for resilience planning and optimization. This invention proposes an extreme survivability index to quantify the continuous power supply level of the power grid to loads of varying importance under extreme conditions. This index not only considers whether the load receives power support but also comprehensively incorporates the reinforcement of power supply paths to reflect the improved load supply effect of multiple power supply routes and lifeline construction.

[0024] The index was proposed based on the following considerations: First, the power supply status of critical loads is a direct reflection of extreme survivability. In islanded or severely damaged power grid environments, if a load completely loses power, its function is also lost. Therefore, it is necessary to consider whether the load is guaranteed when calculating the indicators.

[0025] Secondly, different loads have varying degrees of importance to urban operations. For example, communication hubs, hospitals, and rail transit are considered extremely important loads, while general commercial or industrial loads are considered secondary. Therefore, a unified indicator needs to differentiate between different loads through importance weighting to ensure that the ultimate survivability capability truly reflects the overall system's support level for the city's lifeline infrastructure.

[0026] The continuous power supply to a load depends not only on the number of power sources connected, but also on the reliability of their power supply paths. Ordinary paths are more vulnerable to extreme events, while reinforced lifelines have a stronger ability to withstand risks. Therefore, the reinforcement ratio of power supply channels needs to be included as an explicit factor in the indicator calculation to quantify the contribution of lifeline construction to the protection effect.

[0027] Based on the above considerations, this invention unifies the modeling of three factors: load supply status, load importance weight, and the proportion of enhanced supply channels, thus forming the extreme survivability index. Extreme Survivability Index for: ; In the formula, Indicates important load cl Is it powered by the power supply? The guarantee is 1 if it is not guaranteed, and 0 otherwise. Indicates important load cl Importance weight; Indicates important load cl Power supply The increased proportion of guaranteed channels reflects the weighted role of lifeline construction in supply reliability.

[0028] First, by introducing the load's guaranteed status and importance weights, the index can simultaneously characterize "whether the load is powered" and "how important the load is." Second, by introducing the channel reinforcement ratio, it integrates multiple power supply paths and lifeline construction into a unified quantitative framework for the first time, accurately reflecting the differences in power supply to loads of different importance under multiple power supply paths. Therefore, the extreme survivability index can not only measure the overall resilience of a local power grid under extreme conditions but also identify the differences in power supply to different loads under multiple power supply conditions, supporting targeted planning and optimization.

[0029] This indicator can serve as both an optimization objective for planning models, guiding investment allocation under limited resource conditions to maximize overall survivability, and a constraint, ensuring that critical loads of varying importance meet policy requirements for multi-path power supply and lifeline protection in any optimization scheme. In this way, this invention establishes a calculable and optimizable evaluation indicator, enabling the policy requirement of "load tiering protection" to be transformed into an operational quantitative model.

[0030] S2. Based on the improved commodity flow model, establish multi-path power supply topology constraints applicable to loads of different importance levels, so as to achieve quantitative characterization of power supply reliability for loads of different importance levels and ensure the redundancy requirements of power supply paths for lifeline loads.

[0031] The multi-power supply topology constraints are: ; ; ; ; ; ; ; In the formula, All are node indexes; Index for critical loads; For route indexing; For power index; Indicates all upstream power supplies s / Upstream substation b The set of power supply paths for critical loads; Indicates the upstream power supply s / Upstream substation b gather; Represents a set of important users; Indicates user j The set of power supply path quantity requirements; Represents the set of all lines; Represents the set of power grid nodes; Represents a set of critical loads; Indicates the line The risk coefficient (the more unreliable the line, the larger the coefficient; the coefficient is a positive number ≥ 1). Indicates available upstream power supply s / Upstream substation b Ensure critical loads cl Power supply path Figure 1 Does it pass through the line? The value is 1 if the condition is met, otherwise it is 0. Represents a node j Does it need to come from the power supply path? com Power supply, binary variable; Represents a node j The total demand for the number of power supply paths; Indicates the line Whether to create a new binary variable; Indicates the line Is an upgrade needed? Indicates available upstream power supply s / Upstream substation b Through the power supply path com Supplying electricity to key user nodes; It is a very large positive real number (usually set to the number of nodes).

[0032] The above constraints adopt improved commodity flow constraints, which ensure the multiple power supply needs of different important users, and at the same time plan the corresponding optimal power supply path for important users.

[0033] S3. Establish a differentiated planning model for urban power grid lifelines, and achieve optimal construction of multi-level local power grids through local power grid boundary division, resource allocation and hierarchical constraints.

[0034] In defining the boundaries of local power grids, it is essential to ensure that all critical loads are covered by a local power grid to guarantee continuous power supply under extreme operating conditions. The boundary delineation process should comprehensively consider the tiered needs of loads of varying importance, corresponding the power supply level to the load's criticality. Extremely critical loads should be supplied by at least three independent power sources, forming at least two lifeline channels, with priority given to the nearest network level with suitable construction conditions. First-level critical loads should be supplied by at least two independent power sources, including one lifeline channel, with the backup power source either from the nearest or next-upper network level. Second-level critical loads must be guaranteed by at least one level of local power grid to maintain basic survivability under islanded operation conditions. The overall delineation approach follows the principle that the closer the power source is to the load, the better the protection effect, thereby achieving reasonable coverage of robust local power grids within the regional power grid.

[0035] In terms of resource allocation, considerations need to be given to both the source and grid sides. On the source side, the local power grid should possess steady-state support capabilities to meet extreme survival conditions and the necessary dynamic response capabilities to maintain power supply balance during disturbances. On the grid side, a backbone network capable of efficiently connecting power sources and loads should be formed, and differentiated reinforcement should be implemented for key transmission channels to improve their safety and reliability under extreme events. Simultaneously, power sources with closer supply paths should be prioritized to shorten power supply distances, reduce the impact of channel damage on load power supply stability, and thus enhance the resilience of the local power grid.

[0036] Regarding hierarchical constraints, it is necessary to consider the differences in capacity and support capabilities of power sources at different voltage levels, and to clearly define the matching boundaries between power sources and loads. Specifically, critical loads cannot be supplied through lines with voltage levels lower than their access voltage level, and power sources cannot provide support to lower-level loads through lines with voltage levels higher than their access voltage level. This constraint mechanism avoids ineffective and redundant resource allocation in the planning process, forming a hierarchical, multi-path, and operable power supply guarantee system.

[0037] The specific planning optimization decision-making model is as follows: 1) Objective function The ultimate survivability of critical loads depends on the power source and transmission path available to power them under extreme conditions. Therefore, the primary objectives are to maximize ultimate survivability and ensure power margin. The objective function is: ; In the formula, Indicates important load Is it powered by the power supply? Assure; For important loads Importance coefficient; Indicates power supply Ensure critical loads The proportion of pathway reinforcement; Indicates power supply The guaranteed power; For important loads The load capacity; Index for critical load nodes.

[0038] 2) Planning cost constraints The planning cost constraint for the differentiated planning model of urban power grid lifelines is: ; ; In the formula, This represents the total cost required for the planning; Indicates the upper limit of the planned budget cost; , , These represent the new construction costs for power lines, backup power supplies, and substations, respectively. , , These represent the upgrade costs for power lines, backup power supplies, and substations, respectively. , , All are binary variables, representing whether a line, backup power supply, or substation has been added; , , All are binary variables, representing whether the line, guaranteed power supply, and substation have been upgraded.

[0039] The above formula comprehensively considers the new construction / upgrade costs of lines, power sources, and substations, and imposes a budget ceiling.

[0040] 3) Local power grid extreme survival requirement constraints The local grid extreme survival requirement constraints of the differentiated planning model for urban power grid lifelines include commodity flow constraints, voltage matching constraints, power balance constraints, and power supply capacity constraints.

[0041] Product flow constraints ensure network connectivity. Product flow constraints are as follows: ; ; In the formula, For power supply To the node powered by; Given a variable, representing the virtual requirement of the non-root node (usually set to 1); It is a continuous variable, representing the power source. Lines in the central local power grid The size of the virtual current flowing through; Indicates power supply Lines in the central local power grid The size of the virtual current flowing through; A binary variable representing a line. com Is it currently undergoing an upgrade?

[0042] Voltage matching constraints ensure that a low-voltage power source cannot supply power to a high-voltage load. The voltage matching constraint is as follows: ; ; In the formula, It is a set of nodes. It is a load The voltage level at which it is located, power supply The voltage level at which it is located, It is a line The voltage level at which it is located.

[0043] The power balance constraint is: ; In the formula, , They represent the power supply. s Supply load l The flow , (i,j) The active power of the line, Indicates load l active power, Indicates power supply s Supply load l The active power.

[0044] The power supply capacity constraint is: ; In the formula, For power supply s The active power.

[0045] The comprehensive expression for the local power grid's extreme survival requirement constraint is: ; ; ; ; ; ; ; ; ; ; ; ; ; ; In the formula, Indicates load l The voltage level to which it belongs; This is a binary variable representing the power supply. s Has it been added / upgraded? For power supply s Maximum active power; For power supply s To load l The length of the power supply; Indicates the length of the line; A binary variable representing the load. l Power supply s When powered, the line (i,j) Is it electrified? Indicates if the line (i,j) If the line is in an upgrade state, the weight of the line length is 1; otherwise, it is 0. Indicates load l At the level c The number of backup power supplies; A collection of substations to be built; , , These represent the sets of top-priority users, first-priority users, and second-priority users, respectively.

[0046] 4) Planning variable logic and budget constraints The expression for the local grid extreme survival requirement constraint in the differentiated planning model for urban power grid lifelines is as follows: ; ; ; ; ; ;

[0047] In the formula, , , These represent the sets of lines, power sources, and substations to be newly constructed; , , "Don't" refers to a collection of lines, power sources, and substations that do not require new construction. , , These represent the sets of upgraded lines, power sources, and substations, respectively. This is a binary variable representing a substation. b Has it been upgraded? For substation b With nodes i The status of the lines between them For nodes i With substation b The status of the lines between them.

[0048] 5) Constraints on the dynamic response capability of local power grids The local power grid dynamic response capability requirement constraint of the differentiated planning model for urban power grid lifelines is as follows: ; ; ; ; ; In the formula, , These are the ROCOF after the disturbance and the safety limit, respectively. This is the frequency reference value; It is the change in frequency; For local power grid The power deficit; For local power grid The load shedding power; For local power grid The equivalent inertia; , They represent synchronous generator units. Inverter interface power supply The inertial constant; , They represent synchronous generator units. Inverter interface power supply Does it belong to a local power grid? ; Synchronizer i PFR power; Inverter interface power supply n FFR power; Indicates the maximum allowable frequency deviation of the system; , These represent the complete response time of the inverter interface power supply and the synchronous generator, respectively. For local power grid m The total fast frequency response power that the inverter interface power supply can provide; For local power grid m The total primary frequency regulation power that a medium-synchronous generator unit can provide; This refers to the active power deficit that occurs after grid disturbances. This is a binary variable representing the inverter interface power supply. The operational status; This is a binary variable representing a synchronous generator unit. The operational status.

[0049] Example (i,j) This is a city-district power grid topology diagram according to an embodiment of the present invention, which is used to perform the method described in the present invention. Figure 2 The city's regional power grid is being planned.

[0050] The method described in this invention is used to solve the example, and the planning strategy is obtained as follows: Figure 2 As shown, this forms three 10kV local power grids, one 35kV local power grid, one 110kV local power grid, and one 220kV local power grid.

[0051] from Figure 3 Figure 3As can be seen, the super-grade load located at node 7 achieves a dual support mechanism for both its own and the next higher level local power grid by connecting to the 110kV voltage level. Its power redundancy configuration consists of the 110kV power supply at node 39 and the 220kV power supply at node 38, respectively providing protection for the same and higher levels, effectively improving the system's power supply stability and anti-interference capability. Furthermore, this load also receives three independent power supply paths from the upstream substations at nodes 1, 2, and 4, two of which are reinforced "lifeline" power supply paths. In contrast, the 10kV primary load at node 27 exhibits redundancy protection across up to three levels of local power grid in the planned topology. This is primarily due to its relatively small electrical impedance distance (i.e., close electrical neighborhood) with the secondary loads at nodes 28 and 20. Under the current planning rules, nodes 28 and 20, as important load nodes, each need their own backup power supply; since they partially overlap with the path to node 27, the system's structural optimization tends to create shared redundant paths with high line utilization. Therefore, the three loads share a common "lifeline." Conversely, the secondary critical load located at node 46, due to its relatively peripheral electrical position in the power supply network and its greater electrical distance from other critical loads, is better suited to a self-contained local network structure within the constraints of the overall network construction budget, ensuring its basic power reliability requirements. This area forms a self-consistent power supply unit with a certain degree of "local resilience."

[0052] Therefore, the lifeline differentiation planning method for improving urban power grid resilience described in this invention can solve the problem that existing methods cannot effectively achieve differentiated load protection under limited resource conditions.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A lifeline differentiated planning method for improving the resilience of urban power grids, characterized in that, Includes the following steps: S1. Construct quantitative indicators for the extreme survivability of local power grids to quantify the power supply guarantee level of loads of different importance levels under extreme fault scenarios; S2. Based on the improved commodity flow model, establish multi-path power supply topology constraints applicable to loads of different importance levels to ensure the redundancy requirements of power supply paths for lifeline loads; S3. Establish a differentiated planning model for urban power grid lifelines, and achieve optimal construction of multi-level local power grids through local power grid boundary division, resource allocation and hierarchical constraints.

2. The lifeline differentiated planning method for improving urban power grid resilience according to claim 1, characterized in that, In S1, the quantitative index of the local power grid's extreme survivability is the extreme survivability index. The extreme survivability index comprehensively considers the load supply and demand status, the load importance weight, and the reinforcement ratio of supply guarantee channels. for: ； In the formula, Indicates important load cl Is it powered by the power supply? The guarantee is 1 if it is not guaranteed, and 0 otherwise. Indicates important load cl Importance weight; Indicates important load cl Power supply The proportion of guaranteed channels has been strengthened.

3. The lifeline differentiated planning method for improving urban power grid resilience according to claim 2, characterized in that, In S2, the multi-power supply topology constraint is: ； ； ； ； ； ； ； In the formula, All are node indexes; Index for critical loads; For route indexing; For power index; Indicates all upstream power supplies s / Upstream substation b The set of power supply paths for critical loads; Indicates the upstream power supply s / Upstream substation b gather; Represents a set of important users; Indicates user j The set of power supply path quantity requirements; Represents the set of all lines; Represents the set of power grid nodes; Represents a set of critical loads; Indicates the line The risk factor; Indicates available upstream power supply s / Upstream substation b Ensure critical loads cl Power supply path com Does it pass through the line? The value is 1 if the condition is met, otherwise it is 0. Represents a node j Does it need to come from the power supply path? com Power supply, binary variable; Represents a node j The total demand for the number of power supply paths; Indicates the line Whether to create a new binary variable; Indicates the line Is an upgrade needed? Indicates available upstream power supply s / Upstream substation b Through the power supply path com Supplying electricity to key user nodes; It is a positive real number.

4. The lifeline differentiated planning method for improving urban power grid resilience according to claim 3, characterized in that, In S3, the objective function of the differentiated planning model for urban power grid lifelines is to maximize the critical load's ultimate survivability and the guaranteed power supply margin. The objective function is: ； In the formula, Indicates important load Is it powered by the power supply? Assure; For important loads Importance coefficient; Indicates power supply Ensure critical loads The proportion of pathway reinforcement; Indicates power supply The guaranteed power; For important loads The load capacity; Index for critical load nodes.

5. The lifeline differentiated planning method for improving urban power grid resilience according to claim 4, characterized in that, In S3, the planning cost constraint of the differentiated planning model for urban power grid lifelines is: ； ； In the formula, This represents the total cost required for the planning; Indicates the upper limit of the planned budget cost; , , These represent the new construction costs for power lines, backup power supplies, and substations, respectively. , , These represent the upgrade costs for power lines, backup power supplies, and substations, respectively. , , All are binary variables, representing whether a line, backup power supply, or substation has been added; , , All are binary variables, representing whether the line, guaranteed power supply, and substation have been upgraded.

6. The lifeline differentiated planning method for improving urban power grid resilience according to claim 5, characterized in that: In S3, the local grid extreme survival requirement constraints of the differentiated planning model for urban power grid lifelines include commodity flow constraints, voltage matching constraints, power balance constraints, and power supply capacity constraints. The commodity flow constraints are: ； ； In the formula, For power supply To the node powered by; Given variables, representing the virtual requirements of non-root nodes; It is a continuous variable, representing the power source. Lines in the central local power grid The size of the virtual current flowing through; Indicates power supply Lines in the central local power grid The size of the virtual current flowing through; A binary variable representing a line ( i,j Is it currently undergoing an upgrade? The voltage matching constraint is: ； ； In the formula, It is a set of nodes. It is a load The voltage level at which it is located, power supply The voltage level at which it is located, It is a line The voltage level at which it is located; The power balance constraint is: ； In the formula, , They represent the power supply. s Supply load l The flow , (i,j) The active power of the line, Indicates load l active power, Indicates power supply s Supply load l The active power; The power supply capacity constraint is: ； In the formula, For power supply s The active power.

7. The lifeline differentiated planning method for improving urban power grid resilience according to claim 6, characterized in that, In S3, the expression for the local power grid's extreme survival requirement constraint is: ； ； ； ； ； ； ； ； ； ； ； ； ； ； In the formula, Indicates load l The voltage level to which it belongs; This is a binary variable representing the power supply. s Has it been added / upgraded? For power supply s Maximum active power; For power supply s To load l The length of the power supply; Indicates the length of the line; A binary variable representing the load. l Power supply s When powered, the line (i,j) Is it electrified? Indicates if the line (i,j) If the line is in an upgrade state, the weight of the line length is 1; otherwise, it is 0. Indicates load l At the level c The number of backup power supplies; A collection of substations to be built; , , These represent the sets of top-priority users, first-priority users, and second-priority users, respectively.

8. The lifeline differentiated planning method for improving urban power grid resilience according to claim 7, characterized in that, In S3, the logical expressions for the planning variables and budget constraints of the differentiated planning model for urban power grid lifelines are as follows: ； ； ； ； ； ； In the formula, , , These represent the sets of lines, power sources, and substations to be newly constructed; , , These represent sets of lines, power sources, and substations that do not require new construction. , , These represent the sets of upgraded lines, power sources, and substations, respectively. This is a binary variable representing a substation. b Has it been upgraded? For substation b With nodes i The status of the lines between them For nodes i With substation b The status of the lines between them.

9. A lifeline differentiated planning method for improving urban power grid resilience according to claim 8, characterized in that, In S3, the local power grid dynamic response capability requirement constraint of the urban power grid lifeline differentiated planning model is as follows: ； ； ； ； ； In the formula, , These are the ROCOF after the disturbance and the safety limit, respectively. This is the frequency reference value; It is the change in frequency; For local power grid The power deficit; For local power grid The load shedding power; For local power grid The equivalent inertia; , They represent synchronous generator units. Inverter interface power supply The inertial constant; , They represent synchronous generator units. Inverter interface power supply Does it belong to a local power grid? ; Synchronizer i PFR power; Inverter interface power supply n FFR power; Indicates the maximum allowable frequency deviation of the system; , These represent the complete response time of the inverter interface power supply and the synchronous generator, respectively. The sum of the fast frequency response power that the inverter interface power supply in the local power grid m can provide; For local power grid m The total primary frequency regulation power that a medium-synchronous generator unit can provide; This refers to the active power deficit that occurs after grid disturbances. This is a binary variable representing the inverter interface power supply. The operational status; This is a binary variable representing a synchronous generator unit. The operational status.

10. The lifeline differentiated planning method for improving urban power grid resilience according to claim 9, characterized in that: In S3, the commercial solver GUROBI is used to solve the differentiated planning model of urban power grid lifelines, resulting in a resilience planning method.

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