Urban power grid resilience enhancement planning methods and devices considering extreme survivability

Abstract

This invention provides a method for urban power grid resilience enhancement planning that considers extreme survivability. The method includes: obtaining a demand analysis of the dynamic response capability of the urban power grid system under extreme survivability; establishing a system extreme survivability demand model considering power source composition and dynamic capabilities based on the demand analysis; establishing a multi-level local power grid resilience planning optimization decision model based on the system extreme survivability demand model; solving the multi-level local power grid resilience planning optimization decision model to obtain an urban power grid resilience enhancement planning scheme. This invention balances the dynamic and steady-state demands of the local power grid, providing a method for urban power grid resilience enhancement planning that considers extreme survivability dynamic capabilities, thereby improving the frequency security assurance capability of the power system transitioning to local power grid operation after a major fault, and ensuring the economic operational benefits of the planning measures.

Description

Technical Field

[0001] This invention relates to the field of urban power grid planning technology, and in particular to a planning method for improving the resilience of urban power grids that takes into account extreme survivability. Background Technology

[0002] Urban power grids are typically load centers with high load density. To limit system short-circuit currents and other factors, urban power grids generally operate in zones. A zone refers to a network structure centered on one or more 500kV substations, driving the segmented operation of 220kV regional loads. In other words, the 220kV power grids in different zones operate in a de-loop configuration. A zoned power grid is generally a receiving-end grid, receiving power from the 500kV grid and transmitting it through the main 220kV transmission channels. Within a zone, a 220kV ring network structure is formed as the main framework, and each zone has a certain capacity of generating units, with some mutual power supply capability between zones. Due to the high load density, a zone typically contains multiple voltage levels, with generating resources connected to each voltage level.

[0003] High-voltage distribution networks have numerous interconnecting lines between substations at the same level, and each substation is connected to the 220kV transmission network power source via multiple power supply paths, resulting in a flexible network topology. Therefore, when critical upstream power receiving channels are disconnected, various power sources within a zone can be coordinated to support islanded grid operation, achieving extreme survivability. However, achieving extreme survivability requires a solid material foundation; the power supply composition and dynamic response capabilities of the local grid must meet certain requirements. Furthermore, considering the potential for multi-point failures due to extreme events, differentiated reinforcement is needed for critical power transmission or interconnecting paths to enhance the extreme survivability of robust local grids at various system levels, ensuring uninterrupted power supply to critical loads.

[0004] Currently, existing power grid resilience planning methods primarily target large power grids or medium- and low-voltage distribution networks. These methods include heuristic approaches, stochastic optimization, and robust optimization. Regarding the resilience enhancement planning measures considered, existing methods mainly involve upgrading or adding one or two of the following: lines, substations, and power sources. All resilience enhancement measures should be optimized together. Furthermore, a specific power grid may face multiple extreme event threats; therefore, the proposed resilience enhancement planning strategy should have a certain degree of universality, capable of improving the power grid's ability to cope with various extreme events.

[0005] The shortcomings of existing power grid resilience planning methods include: insufficient consideration of the dynamic survivability of the power grid under extreme events, i.e., the ability of the power grid to quickly resume normal operation after being subjected to shocks. In addition, existing power grid resilience planning methods also fail to fully consider the redundancy of multiple voltage levels. Redundancy of multiple voltage levels is beneficial for achieving resource and structural complementarity at different voltage levels, thereby enhancing the overall anti-interference and adaptability of the power grid. Summary of the Invention

[0006] This invention provides a planning method for improving the resilience of urban power grids by taking into account extreme survivability, so as to effectively improve the stability and risk resistance of the overall urban power grid.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] According to one aspect of the present invention, a method for planning urban power grid resilience enhancement considering extreme survivability is provided, comprising:

[0009] Demand analysis for dynamic response capabilities of urban power grid systems in order to achieve extreme survival;

[0010] Based on the aforementioned requirements analysis, a system extreme survival requirement model considering power supply configuration and dynamic capabilities is established.

[0011] Based on the system's extreme survival requirement model, a multi-level local power grid resilience planning optimization decision model is established. The multi-level local power grid resilience planning optimization decision model is solved to obtain a planning scheme for improving urban power grid resilience.

[0012] Preferably, the requirement analysis for obtaining extreme survival capabilities of the urban power grid system includes:

[0013] The system frequency is represented by the inertial center frequency. The system frequency change rate at the moment of disturbance is obtained based on the system equivalent inertial time constant, the rotor kinetic energy of the unit at rated speed, the rated capacity of the unit, and the system power deficit. Based on the supporting role of the power source at different time scales of system frequency dynamics, the inertial support capability, the response capability at the hundred-millisecond level, and the response capability at the second level of various resources are used to describe the dynamic frequency support capability of resources. A robust local power grid system frequency dynamic capability response requirement constraint suitable for planning and decision-making is established.

[0014] Preferably, the requirement analysis for obtaining extreme survival capabilities of the urban power grid system includes:

[0015] The inertial center frequency is used to represent the system frequency, as shown in Equation 1 below:

[0016]

[0017] In the formula, f COI Here, i is the system inertial center frequency, and H is typically the unit node. gi Let f be the inertial time constant of unit i. i Let f be the frequency of node i. COI f;

[0018] Set the system frequency change rate at the instant of the disturbance as follows:

[0019]

[0020] In the formula, Hs is the equivalent inertial time constant of the system; W i S is the rotor kinetic energy of unit i at its rated speed; i ΔP is the rated capacity of unit i; loss This is due to a power deficit in the system.

[0021] Based on the supporting role of power sources at different time scales of system frequency dynamics, the dynamic frequency support capability of resources is described by the inertia support capability, the response capability at the hundred-millisecond level, and the response capability at the second level. A dynamic frequency capability response requirement constraint suitable for planning and decision-making is established for a robust local power grid system. It is defined as the dynamic response capability of various power sources within the local power grid being able to ensure the survival of the internal 20% load limit under a sudden 50% power deficit in the system. The dynamic process needs to maintain the frequency change rate and the minimum frequency point at 1Hz / s and 49Hz, respectively.

[0022] Preferably, the step of establishing a system extreme survivability requirement model considering power supply configuration and dynamic capabilities based on the requirements analysis includes:

[0023] Based on the response time of different resources during a single mishap, resource response capabilities are divided into millisecond-level response and second-level response. The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) Frequency minimum point.

[0024] The system's extreme survival requirement model is composed of the ROCOF constraint, total inertia representation, and minimum frequency point constraint.

[0025] Preferably, the step of establishing a system extreme survivability requirement model considering power supply configuration and dynamic capabilities based on the requirements analysis includes:

[0026] Based on the response time of different resources in a single operation, resource response capabilities are divided into hundreds of milliseconds-level response and seconds-level response. The frequency dynamic changes of power supplies with both seconds-level and hundreds of millisecond-level responses are described by a first-order oscillation equation, namely:

[0027]

[0028] In the formula: Δf(t) is the frequency deviation; H is the equivalent inertial time constant of the system; D is the damping coefficient; P R，l (t)=∑ i P i (t)+∑ n F n (t) represents the system's resource response power; P C (t) represents the system scheduling and control response power; ΔP eThe disturbance power of the system;

[0029] The power system frequency security indicators considered during the planning process include: 1) ROCOF; 2) frequency minimum point;

[0030] The ROCOF constraints are as follows:

[0031]

[0032] The total inertia of the system is expressed as

[0033]

[0034] In the formula: H is the total inertia of the system, i.e., the equivalent inertial time constant of the system; H i Let be the inertial constant of synchronous machine i; H represents the capacity of unit i; n Let n be the inertial constant of the inverter interface power supply. Let n be the rated power of the inverter interface power supply; the minimum frequency constraint is as follows:

[0035] Integrating both sides of equation (5) yields:

[0036]

[0037] In the formula: H is the equivalent inertial time constant of the system; Δf(t) is the frequency deviation at time t; t E The complete response time is in the hundreds of milliseconds range; ΔP L This is the load shedding amount; ΔP e The disturbance power of the system;

[0038] By performing an equation transformation on equation (8) and converting the per-unit value to a named value, the frequency deviation at time t is obtained as follows:

[0039]

[0040] By setting the derivative of the frequency deviation to 0, the time for the frequency to reach its minimum point can be obtained from equation (5):

[0041]

[0042] Substituting equation (10) into equation (9), and transforming the frequency expression, we obtain the constraint for the lowest frequency point as follows:

[0043]

[0044] The system's extreme survival requirement model is composed of formulas (6), (7), and (11).

[0045] Preferably, the step of establishing a multi-level local power grid resilience planning optimization decision model based on the system's extreme survivability demand model, and solving the multi-level local power grid resilience planning optimization decision model to obtain a city power grid resilience improvement planning scheme includes:

[0046] The principles for setting up resource deployment within the local power grid are as follows: From the source side, consider the steady-state and dynamic support capabilities of the internal power sources required for the local power grid's extreme survival; From the grid side, consider the differentiated reinforcement of the backbone grid connecting multiple source-load pairs, and in principle, ensure that the distance between the power source and the load is as close as possible.

[0047] The objective function of the multi-level local power grid resilience planning optimization decision model is set, with the primary objective being to maximize the number of backup power sources for the load and the secondary objective being the power supply distance. Constraints on the objective function include planning cost, local power grid single-product flow, multi-level backup for critical loads, planning principle, planning variable logic and budget, and local power grid dynamic response capability requirements.

[0048] Based on the objective function and various constraints, a mixed-integer nonlinear multi-level local power grid resilience planning optimization decision model is established. A linearization method is used to transform the mixed-integer nonlinear multi-level local power grid resilience planning optimization decision model into a mixed-integer linear multi-level local power grid resilience planning optimization decision model. The solver is used to solve the mixed-integer linear multi-level local power grid resilience planning optimization decision model. The urban power grid resilience enhancement planning scheme includes the capacity, location, type, inertia constant, and active power regulation coefficient of new power sources at each voltage level, the status information of line upgrades / reinforcement, and the node distribution of each island.

[0049] Preferably, the objective function of the multi-level local power grid resilience planning optimization decision model is set as follows: the primary objective is to maximize the number of backup power sources for the load; the secondary objective is the power supply distance; and the objective function is subject to constraints including planning cost, local power grid single-product flow, multi-level backup for important loads, planning principle, planning variable logic and budget constraints, and local power grid dynamic response capability requirements.

[0050] The objective function of the multi-level local power grid resilience planning optimization decision model is set as follows:

[0051] The primary objective is to maximize the number of backup power sources for the load, and the secondary objective is the power supply distance.

[0052] max Rp L L+P γ (12)

[0053]

[0054] In the formula, R represents the weighted sum of the number of power sources to be guaranteed, that is, the number of power sources for which the load is guaranteed; p L P represents the weighting coefficient, indicating the degree of importance the final planning scheme places on the power supply path; γ Penalty term for single commodity flow constraints of all local power grids; Indicates whether load i is in the local power grid centered on power source s, and is a 0-1 variable; m is the local power grid index; i is the index of all load nodes; l is the index of important load nodes; L represents the total length of the power supply path; This is a binary variable indicating whether the critical load l is protected by the power supply s; Indicates the length of the power supply path that the critical load l is protected by the power source s; w l Indicates the importance level of the load node;

[0055] The planning cost constraint for the objective function is set as follows:

[0056]

[0057]

[0058] In the formula, C represents the total cost required for planning; Indicates the upper limit of the planned budget cost; This indicates the cost of constructing new power lines, backup power supplies, and substations. This indicates the upgrade costs for power lines, backup power supplies, and substations. All are binary variables, indicating whether this type of resource has been added; All are binary variables, indicating whether the resource should be upgraded;

[0059] The local power grid single-commodity flow constraint of the objective function is set as follows:

[0060]

[0061] in It is a continuous variable, representing the virtual power flow magnitude through line (i,j) in a local power grid centered on power source s, D i Let M be a known variable representing the virtual demand of non-root nodes, where M is a very large positive real number, and B is a variable representing the virtual demand of non-root nodes. bus It is a set of nodes, c i It is the level where load i is located, c s The level where power supply s is located, c i,j It is the level where line (i,j) is located;

[0062] Equations (18) and (19) are commodity flow constraints to ensure the connectivity of the graph. Equations (20) and (21) are constraints to meet the supply guarantee principle and ensure that low-voltage power sources cannot supply power to high-voltage loads.

[0063] The critical load multi-level safeguard constraints for the objective function are set as follows:

[0064]

[0065]

[0066] In the formula, l is the load index, s is the power supply index, and i / j / k is the node index; p represents the active power flowing through the line supplied by power source s to load l; l This represents the active power of load l; This represents the active power supplied by power source s to load l; a ij This is a binary variable representing whether line (i,j) is in an upgrade state, i.e., whether line (i,j) has been upgraded / created; c l c s c ij Indicates the voltage level to which the component belongs; δ s This is a binary variable indicating whether power supply s has been added / upgraded; L i,j Indicates the length of the line; This is a binary variable representing whether line (i,j) is energized when load l is powered by power source s; i,j This indicates that if line (i,j) is in an upgrade state, the weight of its length is 1; otherwise, it is 0. ij Used to characterize the importance of line (i,j) in the system's extreme survival;

[0067] The planning principle constraints for the objective function are set as follows:

[0068]

[0069] In the formula, This indicates the number of backup power sources for load l at level c; These represent the sets of top-level important users, first-level important users, and second-level important users, respectively; c is the hierarchical index.

[0070] The planning variables and budget constraints of the objective function are set as follows:

[0071]

[0072]

[0073] In the formula, εC δ C , These represent the sets of lines, power sources, and substations to be newly constructed; ε0, δ, These represent sets of lines, power sources, and substations that do not require new construction; ε up 、Sδ up , These represent the sets of upgraded lines, power sources, and substations, respectively; β b This is a binary variable indicating whether substation b has been upgraded;

[0074] The local power grid dynamic response capability requirement constraint of the objective function is set as follows:

[0075]

[0076] In the formula, f RoCoF , ROCOF and safety limits after disturbance; f0 is the frequency reference value; ΔP e,m For the power deficit of local power grid m; ΔP L,m Let H be the load shedding power of local power grid m; H be the equivalent inertia of local power grid m; H i H n These represent the inertial constants of the synchronous generator unit G and the inverter interface power supply E, respectively. These indicate whether synchronous generator unit i and inverter interface power supply n belong to the local power grid m, respectively. The PFR power of synchronous machine i; The FFR power of the inverter interface power supply n; Δf max Indicates the maximum allowable frequency deviation of the system; t E t G These represent the complete response time of the inverter interface power supply and the synchronous generator, respectively.

[0077] According to another aspect of the present invention, a planning device for improving the resilience of urban power grids considering extreme survivability is provided, comprising:

[0078] The requirements analysis acquisition module is used to acquire the requirements analysis of the dynamic response capability of the urban power grid system under extreme survival conditions.

[0079] The system extreme survival requirement model establishment module is used to establish a system extreme survival requirement model that considers power supply configuration and dynamic capabilities based on the requirement analysis.

[0080] The urban power grid resilience enhancement planning scheme acquisition module is used to establish a multi-level local power grid resilience planning optimization decision model based on the system extreme survival demand model, solve the multi-level local power grid resilience planning optimization decision model, and obtain the urban power grid resilience enhancement planning scheme.

[0081] Preferably, the demand analysis acquisition module is used to represent the system frequency using the inertial center frequency, and to obtain the system frequency change rate at the moment of disturbance based on the system equivalent inertial time constant, the rotor kinetic energy of the unit at rated speed, the rated capacity of the unit, and the system power deficit. Based on the supporting role of the power supply at different time scales of system frequency dynamics, the module uses the inertial support capability, millisecond-level response capability, and second-level response capability of various resources to describe the dynamic frequency support capability of resources, and establishes a robust local power grid system frequency dynamic capability response demand constraint suitable for planning decisions.

[0082] Preferably, the system extreme survival requirement model establishment module is used to divide the resource response capability into millisecond-level response and second-level response based on the response time of different resources in a single mishap. The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) frequency minimum point.

[0083] The system's extreme survival requirement model is composed of the ROCOF constraint, total inertia representation, and minimum frequency point constraint.

[0084] Preferably, the urban power grid resilience enhancement planning scheme acquisition module is used to set the following principles for the deployment of resources within the local power grid: from the source side, consider the steady-state and dynamic support capabilities of the internal power sources required for the extreme survival of the local power grid; from the grid side, consider the differentiated reinforcement of the backbone network connecting multiple source-load pairs, and in principle, ensure that the distance between the power source and the load is as close as possible.

[0085] The objective function of the multi-level local power grid resilience planning optimization decision model is set, with the primary objective being to maximize the number of backup power sources for the load and the secondary objective being the power supply distance. Constraints on the objective function include planning cost, local power grid single-product flow, multi-level backup for critical loads, planning principle, planning variable logic and budget, and local power grid dynamic response capability requirements.

[0086] Based on the objective function and various constraints, a mixed-integer nonlinear multi-level local power grid resilience planning optimization decision model is established. A linearization method is used to transform the mixed-integer nonlinear multi-level local power grid resilience planning optimization decision model into a mixed-integer linear multi-level local power grid resilience planning optimization decision model. The solver is used to solve the mixed-integer linear multi-level local power grid resilience planning optimization decision model. The urban power grid resilience enhancement planning scheme includes the capacity, location, type, inertia constant, and active power regulation coefficient of new power sources at each voltage level, the status information of line upgrades / reinforcement, and the node distribution of each island.

[0087] As can be seen from the technical solutions provided by the embodiments of the present invention above, the present invention takes into account both the dynamic and steady-state needs of the local power grid and provides a method for urban power grid resilience enhancement planning that considers extreme survival dynamic capabilities. This method aims to improve the frequency security guarantee capability of the power system after it suffers a major fault and switches to local power grid operation, while ensuring the economic benefits of the planning measures.

[0088] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0089] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0090] Figure 1 This is a flowchart illustrating a planning method for improving the resilience of urban power grids that considers extreme survivability dynamics, as provided in an embodiment of the present invention.

[0091] Figure 2 This is a schematic diagram illustrating the timing relationship between inertia support, primary frequency modulation, and fast frequency response in the system frequency response process according to an embodiment of the present invention.

[0092] Figure 3 This is a schematic diagram of a multi-resource frequency response process provided in an embodiment of the present invention.

[0093] Figure 4 This is a schematic diagram of a computational example model based on a regional power grid in a city in China, provided as an embodiment of the present invention.

[0094] Figure 5 A schematic diagram of a local power grid planning strategy considering extreme survivability is provided in an embodiment of the present invention;

[0095] Figure 6 This is a structural diagram of a planning device for improving the resilience of urban power grids, which takes into account the dynamic capabilities of extreme survival, provided in an embodiment of the present invention. Detailed Implementation

[0096] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0097] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0098] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0099] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0100] Given that urban power grids, including those in various districts, are all receiving-end grids, and voltage issues are primarily resolved locally, significant active power deficits and dynamic frequency problems typically occur during extreme survival scenarios. Therefore, when designing robust local power grids, it is necessary to consider the system's dynamic frequency response capability. This means considering the frequency support provided by all generation resources within the local grid, including inverter interface power supplies and synchronous machine power supplies, to ensure that the dynamic frequency response capability of the surviving local grid system meets the frequency stability requirements under active power surges, thus ensuring extreme survival.

[0101] When extreme events cause the disconnection of the upstream power receiving channel of a local power grid, the local power grid unplannedly switches to islanded operation. The local power grid must independently cope with active power surges and maintain frequency variations within a safe range. Under unplanned islanding extreme survival conditions, after an active power disturbance occurs, the extreme frequency values ​​and maximum rate of frequency change of the local robust power grid must be within the system's tolerable range. Power system frequency dynamics are closely related to active power balance. System frequency response dynamics can be divided into four stages: inertial response, primary frequency regulation, secondary frequency regulation, and tertiary frequency regulation. The dynamic capabilities of interest in this invention include inertial response and frequency dynamics within the primary frequency regulation timescale.

[0102] Example 1

[0103] A flowchart illustrating a planning method for improving the resilience of urban power grids that considers extreme survivability dynamics, as provided in this embodiment of the invention, is shown below. Figure 1 As shown, the processing steps are as follows:

[0104] Step S1: Obtain an analysis of the system's dynamic response capabilities required for extreme survival.

[0105] Step S2: Based on the above requirements analysis, establish a system extreme survival requirement model that considers power supply configuration and dynamic capabilities.

[0106] Step S3: Based on the above system extreme survival requirement model, propose a multi-level self-balancing local power grid partitioning and defense resource deployment optimization decision scheme.

[0107] Step S4: Construct a case study based on the actual power grid of a city in my country and verify the effectiveness of the planning strategy.

[0108] Specifically, step S1 includes: the frequency dynamics of each node in the power grid after the disturbance have spatiotemporal distribution characteristics; the frequency value not only changes with time, but the frequency change process of each node also differs. Therefore, this invention uses the inertial center frequency to represent the system frequency, as shown in Equation 1 below. This method has been widely adopted by relevant scholars in the study of dynamic analysis of system frequency response.

[0109]

[0110] In the formula, f COI Here, i is the system inertial center frequency, and H is typically the unit node. gi Let f be the inertial time constant of unit i (unit types include steam turbine units and inverter interface power supplies that can provide inertial support). i Let f be the frequency of node i. For simplicity, let f be the frequency of node i. COI Let f be the value.

[0111] At the instant of power grid disturbance (t) 0+ At the moment the unit's inertial response begins, the system rate of change of frequency (ROCOF) reaches its maximum. At the instant of the fault, the governor and emergency control measures do not respond due to delay, and the unit's mechanical power and emergency control resource power remain unchanged. Therefore, the frequency drop during this phase is only limited by the inertial response of units within the grid. The system frequency change rate at the moment of the disturbance is:

[0112]

[0113] In the formula, Hs is the equivalent inertial time constant of the system; W i S is the rotor kinetic energy of unit i at its rated speed; iΔP is the rated capacity of unit i; loss This represents a system power deficit. If the rate of frequency change exceeds the threshold value of the unit's protection device, it will cause a unit tripping accident. The stronger the system's inertia support capability, the lower the rate of frequency change under the same disturbance. According to the UK National Grid technical report and literature, in a power system with a nominal frequency of 50Hz, the ROCOF value ranges from 0.1Hz / s to 1.0Hz / s.

[0114] Due to the significant active power deficit caused by the fault, the frequency will drop dramatically, often reaching its lowest point within seconds. Subsequently, under the action of primary frequency regulation and emergency frequency control measures, the transient frequency gradually recovers to a stable state. Throughout this process, different types of power sources respond to frequency changes at different time scales, suppressing rapid frequency shifts. Synchronous machines provide inertia support and primary frequency regulation support, while inverter interface power supplies can provide a fast frequency response through converter control. Figure 2 This diagram illustrates the timing relationship between inertia support, primary frequency regulation, and fast frequency response in the system frequency response process, as proposed in an embodiment of the present invention. Inertia support provides an instantaneous response, while the primary frequency regulation of the synchronous machine has a delay, with a response time of 2–30 seconds, whereas the inverter interface power supply can respond within hundreds of milliseconds.

[0115] Based on the above analysis, this invention describes the dynamic frequency support capability of resources by using inertia support capability, millisecond-level response capability, and second-level response capability, according to the supporting role of power sources at different time scales of system frequency dynamics. The millisecond-level and second-level response capabilities include frequency response speed, response power, and response energy. Based on these indicators, the dynamic response capability of resources is measured, and its relationship with the local power grid system's frequency dynamic response capability is further analyzed, mainly focusing on the frequency minimum point and the initial rate of frequency change, facilitating consideration in the planning model.

[0116] Based on the above analysis, this invention establishes a frequency dynamic capability response requirement constraint for robust local power grid systems suitable for planning and decision-making. This constraint is defined as ensuring the dynamic response capability of various power sources within the local power grid can guarantee the survival of 20% of the internal load under a sudden 50% power deficit. During the dynamic process, the frequency change rate and the lowest frequency point must meet 1Hz / s and 49Hz, respectively. Considering that urban power grids are receiving-end grids, with external power reception generally not exceeding 50%, a 50% power deficit is selected. For different regional power grids, this can be adjusted based on external power reception conditions. Simultaneously, considering that the proportion of important loads generally does not exceed 15% of the total load, a 20% limit survival load is set.

[0117] Specifically, step S2 includes: analyzing the process of synchronous machine and inverter interface power supply participating in the frequency response of local power grid system, and then establishing frequency security constraints for local power grid system suitable for planning.

[0118] Figure 3 This is a schematic diagram of a multi-resource frequency response process provided in an embodiment of the present invention. Figure 3 As shown, based on the response time of different resources in a single operation, resource response capabilities are divided into millisecond-level response and second-level response. It is assumed that the unit response increases linearly with time, and that at time t... E and t G After full response, the full response time is between t E and t G The inverter interface power supply between them is t E A conservative estimate, and assuming time t. E The unit's frequency regulation output was then no longer increased to ensure the feasibility of the result, namely:

[0119]

[0120] In the formula: P i (t) represents the active power response capacity with a second-level response; F n (t) represents the fast frequency response capacity with a response time in the hundreds of milliseconds range. The power of power supply i is measured in seconds; The power of the power supply n with a response time in the hundreds of milliseconds; t G The complete response time is in the order of seconds; t E The complete response time is in the hundreds of milliseconds range; The response ramp rate of power supply i is in the second range. The response ramp rate of power supply n with a response time in the hundreds of milliseconds range.

[0121] The frequency dynamics of power supplies with response times in seconds and hundreds of milliseconds can be described by a first-order oscillation equation, namely:

[0122]

[0123] In the formula: Δf(t) is the frequency deviation; H is the equivalent inertial time constant of the system; D is the damping coefficient; P R，i (t)=∑ i P i (t)+∑ n F n (t) represents the system's resource response power; P C (t) represents the system scheduling control (emergency frequency control scheduling decision) response power; ΔPe This represents the system's disturbance power.

[0124] The power system frequency security indicators considered during the planning process include: 1) ROCOF (Return on Flow of Power); and 2) Minimum Frequency. By co-optimizing the deployment of different types of power sources, the system can be ensured to maintain frequency stability under extreme conditions.

[0125] The ROCOF constraints are as follows:

[0126]

[0127] The total inertia of the system can be expressed as

[0128]

[0129] In the formula: H is the total inertia of the system, i.e., the equivalent inertial time constant of the system; H i Let be the inertial constant of synchronous machine i; H represents the capacity of unit i; n Let n be the inertial constant of the inverter interface power supply. Let n be the rated power of the inverter interface power supply. The minimum frequency constraint is as follows:

[0130] The load damping effect on frequency change is relatively small during transients, so the load damping effect is ignored to simplify the calculation. Integrating both sides of equation (5) yields:

[0131]

[0132] In the formula: H is the equivalent inertial time constant of the system; Δf(t) is the frequency deviation at time t; t E The complete response time is in the hundreds of milliseconds range; ΔP L This is the load shedding amount; ΔP e This represents the system's disturbance power.

[0133] By performing an equation transformation on equation (8) and converting the per-unit value to a named value (taking the reference frequency f0 as 50Hz), the frequency deviation at time t can be obtained as follows:

[0134]

[0135] By setting the derivative of the frequency deviation to 0, the time for the frequency to reach its minimum point can be obtained from equation (5):

[0136]

[0137] Substituting equation (10) into equation (9), and then transforming the frequency expression, we obtain the constraint for the lowest frequency point as follows:

[0138]

[0139] The system's extreme survival requirement model in this step consists of formulas (6), (7), and (11). In the following step S3 modeling process, the system's extreme survival requirement model is expressed as formulas (39)-(43).

[0140] Specifically, step S3 above includes the following principles for local power grid planning:

[0141] First, the local robust grid of a regional power grid needs to cover all important loads. Second, in principle, the number of protection levels for an important load is positively correlated with its importance. Finally, based on the principle that the closer the protection level is to the important load, the better the effect, the local power grid boundary is delineated. Specifically, for extremely important users, the power supply should be nearby, and the protection level should at least include the nearest network level with construction conditions; for first-level important users, the power supply should be the nearest network level with construction conditions or the next higher level; and for second-level important loads, the power supply should have at least one layer of local power grid protection.

[0142] Resilience planning includes the delineation of local power grid boundaries and the deployment of defense resources. The principles for both aspects are as follows:

[0143] The principles for resource deployment within a local power grid are as follows:

[0144] From the source side, it is necessary to consider the internal power supply steady-state support capability and dynamic support capability required for the extreme survival of the local power grid; from the grid side, it is necessary to consider the differentiated reinforcement of the backbone grid connecting multiple source-load pairs, and in principle, it is necessary to ensure that the distance between the power supply and the load is as close as possible.

[0145] The above planning principles can be formulated by power grid planners based on the actual needs of the power grid. Furthermore, important loads may be connected to different voltage levels. Considering the differences in power supply capacity and capability at different levels, the following principles are established: important loads cannot be guaranteed by lower-level power sources, meaning the load cannot be guaranteed through lines at the next lower voltage level, and the power source cannot be guaranteed through lines at the next higher voltage level.

[0146] The objective function of the multi-level local power grid resilience planning optimization decision model is as follows:

[0147] (I) Objective Function

[0148] The ultimate survivability of critical loads depends on the number of power sources and transmission channels available to supply them under extreme conditions, i.e., the number of power sources that can guarantee their power supply. Therefore, the primary objective is to maximize the number of backup power sources for the load, considering the load's importance as a weight. Furthermore, the closer the backup power source is to the load electrically, the higher the power supply reliability under extreme events; therefore, power supply distance is considered a secondary objective.

[0149] max Rp L L+P γ (12)

[0150]

[0151] In the formula, R represents the weighted sum of the number of power sources to be guaranteed, that is, the number of power sources for which the load is guaranteed; p L P represents the weighting coefficient, indicating the degree of importance the final planning scheme places on the power supply path; γ Penalty term for single commodity flow constraints of all local power grids; Indicates whether load i is in the local power grid centered on power source s, and is a 0-1 variable; m is the local power grid index; i is the index of all load nodes; l is the index of important load nodes; L represents the total length of the power supply path; This is a binary variable indicating whether the critical load l is protected by the power supply s; Indicates the length of the power supply path that the critical load l is protected by the power source s; w l This indicates the level of importance of the load node.

[0152] (II) Planning Cost Constraints

[0153]

[0154] In the formula, C represents the total cost required for planning; Indicates the upper limit of the planned budget cost; This indicates the cost of constructing new power lines, backup power supplies, and substations. This indicates the upgrade costs for power lines, backup power supplies, and substations. All are binary variables, indicating whether this type of resource has been added; Both are binary variables, indicating whether the resource should be upgraded.

[0155] The above formula comprehensively considers the new construction / upgrade costs of lines, power sources, and substations, and imposes a budget ceiling.

[0156] (III) Single-item flow constraints in local power grids

[0157]

[0158] in It is a continuous variable, representing the virtual power flow magnitude through line (i,j) in a local power grid centered on power source s, D i Let M be a known variable, representing the virtual requirement of non-root nodes (generally set to 1), M be a very large positive real number (generally set to the number of nodes), and B be a variable representing the virtual requirement of non-root nodes. bus It is a set of nodes, c i It is the level where load i is located, cs The level where power supply s is located, c i,j It is the level where line (i,j) is located.

[0159] Equations (18) and (19) are commodity flow constraints to ensure the connectivity of the graph. Equations (20) and (21) are constraints to meet the supply guarantee principle and ensure that low-voltage power sources cannot supply power to high-voltage loads.

[0160] (iv) Multi-level protection constraints for critical loads

[0161]

[0162]

[0163] In the formula, l is the load index, s is the power supply index, and i / j / k is the node index; p represents the active power flowing through the line supplied by power source s to load l; l This represents the active power of load l; This represents the active power supplied by power source s to load l; a ij This is a binary variable representing whether line (i,j) is in an upgrade state, i.e., whether line (i,j) has been upgraded / created; c l c s c ij Indicates the voltage level to which the component belongs; δ s This is a binary variable indicating whether power supply s has been added / upgraded; L i,j Indicates the length of the line; This is a binary variable representing whether line (i,j) is energized when load l is powered by power source s; i,j This indicates that if line (i,j) is in an upgrade state, the weight of its length is 1; otherwise, it is 0. ij Used to characterize the importance of line (i,j) in the system's extreme survival.

[0164] (V) Planning Principles and Constraints

[0165]

[0166] In the formula, This indicates the number of backup power sources for load l at level c; These represent the sets of top-level important users, first-level important users, and second-level important users, respectively; c is the hierarchical index.

[0167] (vi) Programming Variable Logic and Budget Constraints

[0168]

[0169]

[0170] In the formula, ε C S C , These represent the sets of lines, power sources, and substations to be newly constructed; ε0, S0, These represent sets of lines, power sources, and substations that do not require new construction; ε up S up , These represent the sets of upgraded lines, power sources, and substations, respectively; β b This is a binary variable indicating whether substation b has been upgraded.

[0171] (vii) Constraints on the dynamic response capability requirements of local power grids

[0172]

[0173] In the formula, f RoCoF , ROCOF and safety limits after disturbance; f0 is the frequency reference value; ΔP e,m For the power deficit of local power grid m; ΔP L,m Let H be the load shedding power of local power grid m; H be the equivalent inertia of local power grid m; H i H n These represent the inertial constants of the synchronous generator unit G and the inverter interface power supply E, respectively. These indicate whether synchronous generator unit i and inverter interface power supply n belong to the local power grid m, respectively. The PFR power of synchronous machine i; The FFR power of the inverter interface power supply n; Δf max Indicates the maximum allowable frequency deviation of the system; t E t G These represent the complete response time of the inverter interface power supply and the synchronous generator, respectively.

[0174] A mixed-integer nonlinear multi-level local power grid resilience planning and optimization decision-making model was established. Linearization methods such as McCormick relaxation were used to transform this mixed-integer nonlinear multi-level local power grid resilience planning and optimization decision-making model into a mixed-integer linear multi-level local power grid resilience planning and optimization decision-making model. The mature solver Gurobi was then used to solve the mixed-integer linear multi-level local power grid resilience planning and optimization decision-making model. The solution results include the capacity, location, type, inertia constant, and active power regulation coefficient of new power sources at each voltage level, the status information of line upgrades / reinforcement, and the node distribution of each island.

[0175] Specifically, step S4 above includes: Figure 4As shown, the model constructed in this invention, based on a regional power grid in a Chinese city, covers four voltage levels: 220kV, 110 / 35kV, 10kV, and 380V, demonstrating the detailed distribution of multi-level power equipment and load nodes. A 220kV power plant is connected to this regional power grid; this plant is a black-start unit and does not require upgrades. In addition, there are 6 220kV substations and 17 110 / 35kV substations within the region. For ease of analysis, only 79 10kV substations, including representative important loads, are shown. The system contains important loads of different levels, including 2 super-level loads, 5 first-level loads, and 7 second-level loads, all connected to 10kV substations to ensure the reliability and stability of power supply. The urban regional power grid has rich interconnections between voltage levels. Under normal operating conditions, each substation maintains electrical connection with only one upstream substation; the remaining lines are normally open interconnections. Therefore, the planning process also only considers the scenario where each substation maintains electrical connection with only one upstream substation. Assuming that all lines and substations can be upgraded, and considering urban space constraints, this project plans 18 new power supply locations to be connected, including synchronous generators and energy storage.

[0176] The proposed method is used to solve the above problem, and the planning strategy is obtained as follows: Figure 5 As shown, this forms six 10kV local power grids, three 110 / 35kV local power grids, and one 220kV local power grid.

[0177] In the simulation test, the protection level requirements of different load levels in the local power grid were analyzed in depth. The results are analyzed as follows:

[0178] The critical load (located at position 69 in the diagram) is protected by up to three levels of local grid protection: local protection, higher-level protection, and the highest-level protection. This three-tiered protection is necessary because critical loads are of extremely high importance, and their power supply must be highly reliable. As a critical node, a power outage to a critical load could lead to serious economic and social consequences. Therefore, triple protection measures are employed in the design to minimize the risk of power outages and ensure a continuous and stable power supply.

[0179] Primary loads (such as the load at position 53 in the diagram) are protected by a maximum of two levels of local grid protection: upper-level protection and the highest-level protection. Under current planning rules, these loads require at least one level of protection (the current level or the next higher level). Considering the crucial role of primary loads, two levels of protection are provided for them whenever possible. Therefore, this primary load receives dual-level protection from both the upper and highest levels. However, the primary load at position 49 in the diagram only receives one level of protection: the highest-level protection. This is because this load is very close to the 220kV power source, the 220kV power source is relatively reliable, and under the dual constraints of dynamic and static local grid conditions, budget limitations, and topology constraints, only a single level of protection is provided for this primary load.

[0180] Secondary loads (such as the load located at position 85 in the diagram) are protected by at least one level of local power grid protection, i.e., local protection. This is because these secondary loads are electrically distant from other important loads and are of the lowest importance; given the limited budget, prioritizing their need for at least one level of protection is sufficient. For these loads, a single level of protection is enough to form a robust, self-contained local power grid, capable of rapidly restoring power supply in the event of a local fault, ensuring power stability. Due to budget and space constraints, this strategy achieves optimal resource allocation while guaranteeing basic power supply needs.

[0181] Example 2

[0182] The present invention provides a structure for a planning device for improving the resilience of urban power grids that considers extreme survivability dynamics, as shown in the embodiment of the invention. Figure 6 As shown, it includes the following modules:

[0183] The requirement analysis acquisition module 61 is used to acquire the requirement analysis of the dynamic response capability of the urban power grid system under extreme survival conditions.

[0184] System extreme survival requirement model establishment module 62 is used to establish a system extreme survival requirement model considering power supply configuration and dynamic capabilities based on the requirement analysis.

[0185] The urban power grid resilience enhancement planning scheme acquisition module 63 is used to establish a multi-level local power grid resilience planning optimization decision model based on the system extreme survival demand model, solve the multi-level local power grid resilience planning optimization decision model, and obtain the urban power grid resilience enhancement planning scheme.

[0186] Specifically, the demand analysis acquisition module 61 is used to represent the system frequency using the inertial center frequency, and to obtain the system frequency change rate at the moment of disturbance based on the system equivalent inertial time constant, the rotor kinetic energy of the unit at rated speed, the rated capacity of the unit, and the system power deficit. Based on the supporting role of the power supply at different time scales of system frequency dynamics, the inertial support capability, millisecond-level response capability, and second-level response capability of various resources are used to describe the dynamic frequency support capability of resources, and to establish a robust local power grid system frequency dynamic capability response demand constraint suitable for planning decisions.

[0187] Specifically, the system extreme survival requirement model establishment module 62 is used to divide the resource response capability into millisecond-level response and second-level response based on the response time of different resources in a single mishap. The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) frequency minimum point.

[0188] The system's extreme survival requirement model is composed of the ROCOF constraint, total inertia representation, and minimum frequency point constraint.

[0189] Specifically, the urban power grid resilience enhancement planning scheme acquisition module 63 is used to set the following principles for the deployment of resources within the local power grid: from the source side, consider the steady-state and dynamic support capabilities of the internal power sources required for the extreme survival of the local power grid; from the grid side, consider the differentiated reinforcement of the backbone network connecting multiple source-load pairs, and in principle, ensure that the distance between the power source and the load is as close as possible.

[0190] The objective function of the multi-level local power grid resilience planning optimization decision model is set, with the primary objective being to maximize the number of backup power sources for the load and the secondary objective being the power supply distance. Constraints on the objective function include planning cost, local power grid single-product flow, multi-level backup for critical loads, planning principle, planning variable logic and budget, and local power grid dynamic response capability requirements.

[0191] Based on the objective function and various constraints, a mixed-integer nonlinear multi-level local power grid resilience planning optimization decision model is established. A linearization method is used to transform the mixed-integer nonlinear multi-level local power grid resilience planning optimization decision model into a mixed-integer linear multi-level local power grid resilience planning optimization decision model. The solver is used to solve the mixed-integer linear multi-level local power grid resilience planning optimization decision model. The urban power grid resilience enhancement planning scheme includes the capacity, location, type, inertia constant, and active power regulation coefficient of new power sources at each voltage level, the status information of line upgrades / reinforcement, and the node distribution of each island.

[0192] The specific process of planning urban power grid resilience enhancement considering extreme survivability dynamic capabilities using the apparatus of this invention is similar to the aforementioned method embodiments, and will not be repeated here.

[0193] In summary, the urban power grid resilience enhancement planning method of this invention, which considers extreme survivability dynamics, flexibly applies multi-level protection strategies based on factors such as load importance and electrical distance to ensure the power supply reliability of loads at all levels. This ensures that the urban power grid can smoothly switch local grid operation without frequency exceeding limits in the event of extreme faults, reducing economic losses and social impacts caused by power outages, improving the overall stability and resilience of the power grid, and ensuring the efficient operation of the power system.

[0194] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0195] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the present invention.

[0196] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0197] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for urban power grid resilience enhancement planning considering extreme survivability, characterized in that, include: Demand analysis for dynamic response capabilities of urban power grid systems in order to achieve extreme survival; Based on the aforementioned requirements analysis, a system extreme survival requirement model considering power supply configuration and dynamic capabilities is established. Based on the system's extreme survival requirement model, a multi-level local power grid resilience planning optimization decision model is established. The multi-level local power grid resilience planning optimization decision model is solved to obtain a planning scheme for improving urban power grid resilience. The aforementioned demand analysis for obtaining extreme survival requirements of urban power grid system dynamic response capabilities includes: The system frequency is represented by the inertial center frequency. The system frequency change rate at the moment of disturbance is obtained based on the system equivalent inertial time constant, the rotor kinetic energy of the unit at rated speed, the rated capacity of the unit and the system power deficit. Based on the supporting role of the power source at different time scales of system frequency dynamics, the inertial support capability, the response capability at the hundred-millisecond level and the response capability at the second level of various resources are used to describe the dynamic frequency support capability of resources. A robust local power grid system frequency dynamic capability response requirement constraint suitable for planning and decision-making is established. The aforementioned requirement analysis, which establishes a system extreme survivability requirement model considering power supply configuration and dynamic capabilities, includes: Based on the response time of primary frequency regulation for different resources, the resource response capability is divided into millisecond-level response and second-level response. The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) frequency minimum point; The system's extreme survival requirement model is composed of the system's ROCOF constraints, total inertia representation, and minimum frequency point constraints. The aforementioned requirement analysis, which establishes a system extreme survivability requirement model considering power supply configuration and dynamic capabilities, includes: Based on the response time of different resources during primary frequency regulation, resource response capabilities are divided into millisecond-level response and second-level response. The frequency dynamic change process of power supplies with second-level and millisecond-level responses is described by a first-order oscillation equation, namely: where: is the frequency deviation; is the system equivalent inertial time constant; is the damping coefficient; represents the resource response power of the system; is the system dispatch control response power; is the system disturbance power; The ROCOF constraints are as follows: The total inertia of the system is expressed as In the formula: This is the total inertia of the system, i.e., the equivalent inertial time constant of the system; Synchronous unit node i The inertial constant; For the unit i The capacity; Inverter interface power supply n The inertial constant; Inverter interface power supply n Rated power; The minimum frequency point constraint is as follows: Integrating both sides of equation (5) yields: In the formula: is t the frequency deviation at the moment; ; ; is the full response time of the response in the order of 100 milliseconds; is the amount of load shedding; The equation transformation is made to formula (8), and the unit value is converted into the named value, to obtain t The frequency deviation of the time is: By setting the derivative of the frequency deviation to 0, the time for the frequency to reach its lowest point can be obtained from equation (5): Substituting equation (10) into equation (9), and transforming the frequency expression, we obtain the constraint on the lowest frequency point as follows: The system's extreme survival requirement model is composed of formulas (6), (7), and (11); The process of establishing a multi-level local power grid resilience planning optimization decision model based on the system's extreme survival requirement model, solving the multi-level local power grid resilience planning optimization decision model, and obtaining a city power grid resilience improvement planning scheme includes: The principles for setting up resource deployment within the local power grid are as follows: From the source side, consider the steady-state and dynamic support capabilities of the internal power sources required for the local power grid's extreme survival; From the grid side, consider differentiated reinforcement of the backbone grid connecting multiple source-load pairs, and ensure that the distance between the power source and the load is as close as possible. The objective function of the multi-level local power grid resilience planning optimization decision model is set, the main target is set as maximizing the number of power supply guaranteeing the load, the secondary target is set as minimizing the power supply distance, the planning cost constraint, the single commodity flow constraint of the local power grid, the multi-level guarantee constraint of important load, the planning principle constraint, the planning variable logic and budget constraint, and the dynamic response capability demand constraint of the local power grid of the objective function are set Based on the objective function and various constraint conditions, the mixed integer nonlinear multi-level local power grid resilience planning optimization decision model is established, the mixed integer nonlinear multi-level local power grid resilience planning optimization decision model is changed into a mixed integer linear multi-level local power grid resilience planning optimization decision model by using a linearization method, and the mixed integer linear multi-level local power grid resilience planning optimization decision model is solved by using a solver, the urban power grid resilience improvement planning scheme includes the capacity, position, type, inertia constant and active power regulation coefficient of the added power supply of each voltage level, the state information of line upgrading / strengthening, and the node distribution of each island; The objective function of the multi-level local power grid resilience planning optimization decision model is set, the main target is set as maximizing the number of power supply guaranteeing the load, the secondary target is set as minimizing the power supply distance, the planning cost constraint, the single commodity flow constraint of the local power grid, the multi-level guarantee constraint of important load, the planning principle constraint, the planning variable logic and budget constraint, and the dynamic response capability demand constraint of the objective function are set The objective function of the multi-level local power grid resilience planning optimization decision model is set as follows: The main target is set as maximizing the number of power supply guaranteeing the load, and the secondary target is set as minimizing the power supply distance; In the formula, R represents the weighted total of the number of power sources that are guaranteed, that is, the number of power sources that are guaranteed for the load. The weighting coefficient represents the degree of importance the final planning scheme places on the power supply path; Penalty term for single commodity flow constraints of all local power grids; Indicates load Is it in the power supply? In the local power grid centered on the variable, it is a 0-1 variable; For local power grid indexing; Index all load nodes; This is an index for critical load nodes; L represents the total length of the power supply path. A binary variable representing a critical load. Is it powered by a power source? guaranteed; Indicates important load Power supply The length of the guaranteed power supply path; Indicates the importance level of the load node; The planning cost constraint of the objective function is set as: In the formula, represents the total cost required for planning; represents the upper limit of the budget cost of planning; represents the new construction cost of lines, backup power supply, and substations; represents the upgrade cost of lines, backup power supply, and substations; , , are binary variables, representing whether the resource is newly added; , , are binary variables, representing whether the resource is upgraded; The single commodity flow constraint of the objective function is set as: wherein is a continuous variable representing the magnitude of the virtual flow flowing through the line centered at the power supply , is a known variable representing the virtual demand of the non-root node, is a positive real number with a very large value, is a set of nodes, is the level where the load is located, is the level where the power supply is located, is the level where the line is located; Formula (18) and (19) are commodity flow constraints, which ensure the connectivity of the graph, formula (20) and formula (21) are constraints for meeting the power supply guarantee principle and realizing that the low-voltage level power supply cannot supply power to the high-voltage level load; The multi-level guarantee constraint of important load of the objective function is set as: wherein, l is a load index, s is a power supply index, i / j / k is a node index; , represents the active power flowing through the line supplied by the power supply s to the load l ; represents the active power of the load l ; represents the active power supplied by the power supply s to the load l ; is a binary variable indicating whether the line (i,j) is in an upgrade state / newly built, i.e. whether the line (i,j) has been upgraded / newly built; , represents the voltage class to which the element belongs; is a binary variable indicating whether the power supply s has been newly added / upgraded; represents the length of the line; is a binary variable indicating whether the line l is live if the line s is supplied by the power supply (i , ; j) is not live; represents a weight of the length of the line if the line (i,j) is in an upgrade state, and is 0 otherwise; The planning principle constraint of the objective function is set as: In the formula, represents the load l In the hierarchy c The number of guaranteed power supply under the hierarchy; respectively represent the set of special important users, the set of first-level important users, and the set of second-level important users; c is the hierarchy index; The planning variable logic and budget constraint of the objective function is set as: In the formula, , respectively represent the line, power supply, substation set to be newly built; , respectively represent the line, power supply, substation set without the need to be newly built; , respectively represent the line, power supply, substation set that has been upgraded; is a binary variable, indicating whether the substation b is upgraded; The dynamic response capability demand constraint of the local power grid of the objective function is set as: wherein, is the disturbed ROCOF and the safety limit; is the frequency reference value; is the power deficit of the local grid ; is the load shedding power of the local grid ; is the equivalent inertia of the local grid ; , represent the inertia constant of the synchronous generator and the inverter-interfaced power source , respectively; , represent whether the synchronous generator node and the inverter-interfaced power source belong to the local grid , respectively; is the PFR power of the synchronous generator node i ; is the FFR power of the inverter-interfaced power source n ; represents the maximum frequency deviation allowed by the system; , represent the full response time of the inverter-interfaced power source and the synchronous generator, respectively.

2. The method of claim 1, wherein, The demand analysis of the dynamic response capability of the urban power grid system to the extreme survival is obtained, including: The inertia center frequency is used to represent the system frequency, as shown in the following formula 1: In the formula, f COI The system's inertial center frequency, i For unit nodes, H gi For unit nodes i The inertial time constant, f i For nodes i The frequency, denoted f COI for f ; The system frequency change rate at the disturbance moment is set as: wherein is the system equivalent inertia time constant; W i is the rated capacity of the unit i rotor kinetic energy at rated speed; S i is the rated capacity of the unit i Δ P loss is the system power deficit; According to the support of the power supply in different time scales of the system frequency dynamics, the inertia support capacity, the millisecond-level response capacity and the second-level response capacity of various resources are used to describe the dynamic frequency support capacity of the resources, a strong local power grid system frequency dynamic capacity response demand constraint suitable for planning decision is established, which is defined as the dynamic response capacity of the internal power supply of the local power grid can meet the guarantee of the internal 20% load limit survival under the system sudden 50% power shortage, and the frequency change rate and the frequency minimum point in the dynamic process need to meet 1 Hz / s and 49 Hz respectively.

3. A device for urban power grid resilience enhancement planning considering extreme survivability, characterized in that, The device comprises: a demand analysis acquisition module for acquiring the demand analysis of the limit survival on the dynamic response capacity of the urban power grid system; a system limit survival demand model establishment module for establishing a system limit survival demand model considering the power supply composition and dynamic capacity according to the demand analysis; an urban power grid resilience improvement planning scheme acquisition module for establishing a multi-level local power grid resilience planning optimization decision model based on the system limit survival demand model, solving the multi-level local power grid resilience planning optimization decision model, and acquiring an urban power grid resilience improvement planning scheme; the demand analysis acquisition module is used to represent the system frequency by the inertia center frequency, acquire the system frequency change rate at the disturbance moment according to the system equivalent inertia time constant, the rotor kinetic energy of the unit at the rated speed, the rated capacity of the unit and the system power shortage, and describe the dynamic frequency support capacity of the resources by the inertia support capacity, the millisecond-level response capacity and the second-level response capacity of various resources according to the support of the power supply in different time scales of the system frequency dynamics, and establish a strong local power grid system frequency dynamic capacity response demand constraint suitable for planning decision; the system limit survival demand model establishment module is used to divide the resource response capacity into millisecond-level response and second-level response according to the response time of the primary frequency modulation of different resources, and consider the power system frequency safety indicators in the planning process, including: 1) ROCOF; 2) frequency minimum point; the system limit survival demand model is composed of the ROCOF constraint, the total inertia representation and the frequency minimum point constraint of the system; the urban power grid resilience improvement planning scheme acquisition module is used to set the internal resource deployment principles of the local power grid as follows: from the source side, the internal power supply steady-state support capacity and dynamic support capacity required for the limit survival of the local power grid are considered; from the network side, the main network architecture of the differentiated reinforcement connection of multiple source-load pairs is considered, and it is necessary to ensure that the power supply and the load distance are as close as possible; the objective function of the multi-level local power grid resilience planning optimization decision model is set, the main target is set to maximize the number of power supply guaranteeing the load, the secondary target is set to minimize the power supply distance, and the planning cost constraint, the local power grid single commodity flow constraint, the important load multi-level guarantee constraint, the planning principle constraint, the planning variable logic and budget constraint and the local power grid dynamic response capacity demand constraint of the objective function are set: A mixed integer nonlinear multi-level local power grid resilience planning optimization decision model is established based on the target function and various constraint conditions, a linearization method is used to change the mixed integer nonlinear multi-level local power grid resilience planning optimization decision model into a mixed integer linear multi-level local power grid resilience planning optimization decision model, and a solver is used to solve the mixed integer linear multi-level local power grid resilience planning optimization decision model, wherein the urban power grid resilience improvement planning scheme includes the capacity, position, type, inertia constant and active power regulation coefficient of the newly added power source of each voltage level, the state information of line upgrading / strengthening, and the node distribution of each island.

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