Urban power grid toughness improvement planning method and device considering extreme survivability

Abstract

The invention provides an urban power grid toughness improvement planning method considering limit survivability. The method comprises the following steps: obtaining demand analysis of limit survival on dynamic response capability of an urban power grid system; according to the demand analysis, establishing a system limit survival demand model considering power supply composition and dynamic capability; and establishing a multi-level local power grid toughness planning optimization decision model based on the system limit survival demand model, and solving the multi-level local power grid toughness planning optimization decision model to obtain an urban power grid toughness improvement planning scheme. According to the toughness improvement planning considering the dynamic demand and the steady demand of the local power grid, the urban power grid toughness improvement planning method considering the limit survival dynamic capability is provided, so that the frequency safety guarantee capability of converting the power system into local power grid operation after the power system suffers from a large fault is improved, and the economic operation benefit of planning measures is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of urban power grid planning, and in particular to a method for planning urban power grid resilience enhancement taking into account extreme survivability. Background Art

[0002] Urban power grids are generally load centers with high load density. In order to limit system short-circuit current and other reasons, urban power grids are generally operated in sections. Sections refer to a network structure that uses one or more 500kV substations as the center to drive the segmented operation of 220kV regional loads, that is, the 220kV power grids in different sections are decoupled. Sectioned power grids are generally receiving-end power grids that receive electricity from 500kV power grids and transmit electricity through the 220kV main transmission channels. A structure with 220kV ring network as the main grid is formed within the section, and there are generator sets of a certain capacity within the section, and the intervals have a certain mutual supply capacity; due to the high load density, the area usually contains multiple voltage levels, and power generation resources are connected to different voltage levels.

[0003] A large number of interconnection lines are built between the substations of the same level in the high-voltage distribution network. Each substation is connected to the power supply point of the 220kV transmission network through multiple power supply paths, and the grid topology is flexible. Therefore, when the upper important power receiving channel is disconnected, various power sources within the partition can be coordinated to support the operation of the grid island and achieve extreme survival. However, to achieve extreme survival, it is necessary to first have a material basis, that is, the power supply composition and dynamic response capabilities of the extreme survival local power grid must meet certain requirements. At the same time, considering that extreme events may cause multiple point failures, key power transmission pathways or interconnection pathways need to be differentiated for reinforcement, in order to enhance the extreme survival capabilities of the strong local power grids at all levels of the system and ensure uninterrupted power supply to important loads.

[0004] At present, the grid resilience planning methods in the existing technology are mainly carried out for large power grids or medium and low voltage distribution networks. They include heuristic methods, stochastic optimization and robust optimization. From the perspective of the resilience improvement planning measures considered, the main measures considered in the existing methods include upgrading or adding one or two of the lines, substations, and power sources. Various measures to improve resilience should be optimized together. Moreover, a specific power grid may face multiple extreme event threats. The proposed resilience improvement planning strategy should have a certain degree of universality and be able to enhance the power grid's ability to cope with various extreme events.

[0005] The shortcomings of the existing grid resilience planning methods include: not fully considering the dynamic survivability of the grid under extreme events, that is, the ability of the grid to quickly resume normal operation after being impacted. In addition, the existing grid resilience planning methods also fail to fully consider the redundancy of multiple voltage levels, which is conducive to the complementarity of resources and structures at different voltage levels to enhance the overall anti-interference and adaptability of the grid. Summary of the invention

[0006] The present invention provides a method for planning urban power grid resilience enhancement taking into account extreme survivability, so as to effectively enhance the stability and risk resistance of the overall urban power grid.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme.

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

[0009] Obtain the demand analysis of the dynamic response capability of the urban power grid system for extreme survival;

[0010] Based on the demand analysis, a system extreme survival demand model considering power supply composition and dynamic capability is established;

[0011] A multi-level local power grid resilience planning optimization decision model is established based on the system extreme survival demand model, and the multi-level local power grid resilience planning optimization decision model is solved to obtain a city power grid resilience improvement planning scheme.

[0012] Preferably, the demand analysis for obtaining extreme survival requirements for the dynamic response capability of the urban power grid system includes:

[0013] The inertia center frequency is used to represent the system frequency. The system frequency change rate at the moment of disturbance is obtained according to the system equivalent inertia time constant, the rotor kinetic energy of the unit at rated speed, the rated capacity of the unit and the system power shortage. According to the supporting role of the power supply at different time scales of the system frequency dynamics, the inertia support capacity, hundred-millisecond response capacity and second response capacity of various resources are used to describe the dynamic frequency support capacity of the resources, and a strong local power grid system frequency dynamic capacity response demand constraint suitable for planning and decision-making is established.

[0014] Preferably, the demand analysis for obtaining extreme survival requirements for the dynamic response capability of the urban power grid system includes:

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

[0016]

[0017] In the formula, f COI is the system inertia center frequency, i is usually the unit node, H gi is the inertia time constant of unit i, f i is the frequency of node i, denoted by f COI is f;

[0018] Set the system frequency change rate at the moment of disturbance to:

[0019]

[0020] Where Hs is the system equivalent inertia time constant; W i is the rotor kinetic energy of unit i at rated speed; S i is the rated capacity of unit i; ΔP loss is the system power shortage;

[0021] According to the supporting role of power sources at different time scales of system frequency dynamics, the inertia support capacity, hundred-millisecond response capacity and second-level response capacity of various types of resources are used to describe the dynamic frequency support capacity of resources, and a strong local power grid system frequency dynamic capacity response demand constraint suitable for planning and decision-making is established. It is defined as the dynamic response capacity of various types of power sources within the local power grid that can meet the system's sudden 50% power shortage to ensure the survival of the internal 20% load limit. The dynamic process needs to maintain the frequency change rate and the lowest frequency point to meet 1Hz / s and 49Hz respectively.

[0022] Preferably, the system extreme survival demand model considering power supply composition and dynamic capability is established according to the demand analysis, including:

[0023] According to the response time of different resources, the resource response capability is divided into hundred millisecond response and second response. The power system frequency security indicators considered in the planning process include: 1) ROCOF: 2) the lowest frequency point;

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

[0025] Preferably, the system extreme survival demand model considering power supply composition and dynamic capability is established according to the demand analysis, including:

[0026] According to the response time of different resources, the resource response capability is divided into 100 millisecond response and second response. The frequency dynamic change process of the power supply with second response and 100 millisecond response is described by the first-order swing equation, that is:

[0027]

[0028] Where: Δf(t) is the frequency deviation; H is the system equivalent inertia time constant; D is the damping coefficient; P R，l (t) = ∑ i P i (t)+∑ n F n (t), represents the resource response power of the system; P C (t) is the system dispatch control response power; ΔP eis the disturbance power of the system;

[0029] The power system frequency security indicators considered in 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] Where: H is the total inertia of the system, that is, the equivalent inertia time constant of the system; H i is the inertia constant of synchronous machine i; is the capacity of unit i; H n is the inertia constant of the inverter interface power supply n; is the rated power of the inverter interface power supply n; the frequency minimum point constraint is as follows:

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

[0036]

[0037] Where: H is the system equivalent inertia time constant; Δf(t) is the frequency deviation at time t; t E The full response time is 100 milliseconds; ΔP L is the load shedding amount; ΔP e is the disturbance power of the system;

[0038] Transform equation (8) and convert the per-unit value into a nominal value to obtain the frequency deviation at time t:

[0039]

[0040] By setting the derivative of the frequency deviation to 0, the time when the frequency reaches the lowest point is obtained from equation (5):

[0041]

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

[0043]

[0044] Formulas (6), (7) and (11) form the system extreme survival demand model.

[0045] Preferably, the multi-level local power grid resilience planning optimization decision model is established based on the system extreme survival demand model, and the multi-level local power grid resilience planning optimization decision model is solved to obtain the urban power grid resilience improvement planning scheme, including:

[0046] The principles for setting up the internal resource deployment of the local power grid are as follows: from the source side, the steady-state support capacity and dynamic support capacity of the internal power supply required for the extreme survival of the local power grid should be considered; from the grid side, differentiated reinforcement of the main grid connecting multiple source-load pairs should be considered, and in principle, the distance between the power supply and the load should be ensured to be as close as possible;

[0047] The objective function of the multi-level local power grid resilience planning optimization decision model is set, the main objective is set to maximize the number of guaranteed power sources for the load, the secondary objective is set to the power supply distance, and the planning cost constraint, local power grid single commodity flow constraint, important load multi-level guarantee constraint, planning principle constraint, planning variable logic and budget constraint and local power grid dynamic response capability demand constraint of the objective function are set:

[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, and 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 mixed integer linear multi-level local power grid resilience planning optimization decision model is solved by a solver. The urban power grid resilience improvement planning scheme includes the capacity, location, type, inertia constant and active power regulation coefficient of new power sources at each voltage level, status information of line upgrade / reinforcement, and node distribution of each island.

[0049] Preferably, the objective function of the multi-level local power grid resilience planning optimization decision model is set, the main objective is set to maximize the number of guaranteed power sources for the load, the secondary objective is set to 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 capability demand constraint of the objective function are set, including:

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

[0051] Set the primary goal to maximize the number of guaranteed power sources for the load, and set the secondary goal to 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 guaranteed power sources, that is, the number of power sources guaranteed for the load; p L is the weight coefficient, which indicates the importance of the final planning scheme to the power supply path; P γ is the penalty term for all local grid single commodity flow constraints; Indicates whether load i is in the local power grid centered on power source s, which 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; is a binary variable, indicating whether the important load l is guaranteed by the power source s; represents the length of the power supply path for the important load l guaranteed by the power source s; w l Indicates the importance level of the load node;

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

[0056]

[0057]

[0058] In the formula, C represents the total cost required for planning; represents the upper limit of the planning budget cost; Indicates the new construction cost of lines, guaranteed power sources and substations; Indicates the upgrade costs of lines, guaranteed power supplies, and substations; They are all binary variables, indicating whether the resource is newly added; They are all binary variables, indicating whether the resource is upgraded;

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

[0060]

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

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

[0063] The important load multi-level protection constraints of the objective function are set as follows:

[0064]

[0065]

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

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

[0068]

[0069] In the formula, It represents the number of guaranteed power sources for load l at level c; They represent the super important user set, the first level important user set, and the second level important user set respectively; c is the hierarchical index;

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

[0071]

[0072]

[0073] In the formula, εC ,δ C , Respectively represent the lines, power sources and substations to be built; ε 0 ,δ, They represent the sets of lines, power sources and substations that do not need to be newly built; ε up , Sδ up , Respectively represent the upgraded lines, power sources, and substations; β b is a binary variable, indicating whether substation b is upgraded;

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

[0075]

[0076] In the formula, f RoCoF , is the ROCOF and safety limit after disturbance; f 0 is the frequency reference value; ΔP e,m is the power shortage of local power grid m; ΔP L,m is the load shedding power of the local power grid m; H is the equivalent inertia of the local power grid m; H i , H n They represent the inertia constants of the synchronous unit G and the inverter interface power supply E respectively; They respectively indicate whether the synchronous unit i and the inverter interface power supply n belong to the local power grid m; is the PFR power of synchronous machine i; is the FFR power of the inverter interface power supply n; Δf max Indicates the maximum frequency deviation allowed by the system; t E ,t G Respectively represent the complete response time of the inverter interface power supply and the synchronous unit.

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

[0078] Demand analysis acquisition module, used to obtain demand analysis of extreme survival on the dynamic response capability of the urban power grid system;

[0079] A system extreme survival demand model establishment module is used to establish a system extreme survival demand model that takes into account power supply composition and dynamic capabilities based on the demand analysis;

[0080] The urban power grid resilience improvement 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 improvement planning scheme.

[0081] Preferably, the demand analysis acquisition module is used to use the inertia center frequency to represent the system frequency, obtain the system frequency change rate at the moment of disturbance 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 use the inertia support capacity, hundred-millisecond response capacity and second-level response capacity of various types of resources to describe the dynamic frequency support capacity of resources according to the supporting role of the power supply at different time scales of the system frequency dynamics, so as to establish a strong local power grid system frequency dynamic capacity response demand constraint suitable for planning decisions.

[0082] Preferably, the system extreme survival demand model establishment module is used to divide the resource response capability into hundreds of milliseconds response and seconds response according to the response time of different resources. The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) the lowest frequency point;

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

[0084] Preferably, the urban power grid resilience improvement planning scheme acquisition module is used to set the following principles for the internal resource deployment of the local power grid: from the source side, the steady-state support capacity and dynamic support capacity of the internal power supply required for the extreme survival of the local power grid are considered; from the grid side, differentiated reinforcement of the backbone grid connecting multiple source-load pairs is considered, and in principle, it is necessary to ensure that the distance between the power supply 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, the main objective is set to maximize the number of guaranteed power sources for the load, the secondary objective is set to the power supply distance, and the planning cost constraint, local power grid single commodity flow constraint, important load multi-level guarantee constraint, planning principle constraint, planning variable logic and budget constraint and local power grid dynamic response capability demand constraint of the objective function are set:

[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, and 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 mixed integer linear multi-level local power grid resilience planning optimization decision model is solved by a solver. The urban power grid resilience improvement planning scheme includes the capacity, location, type, inertia constant and active power regulation coefficient of new power sources at each voltage level, status information of line upgrade / reinforcement, and node distribution of each island.

[0087] It can be seen from the technical solutions provided by the above-mentioned embodiments of the present invention that the present invention takes into account the resilience improvement planning of both the dynamic demand and the steady-state demand of the local power grid, and provides a method for improving the resilience of urban power grids that takes into account the extreme survival dynamic capabilities, so as to improve the frequency safety guarantee capability of the power system when it is transferred to the local power grid operation after a major fault, and to ensure the economic operation benefits of the planning measures.

[0088] Additional aspects and advantages of the present invention will be given in part in the following description, which will become obvious from the following description, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0090] Figure 1 A flow chart of a method for planning for improving the resilience of an urban power grid taking into account extreme survivability dynamic capabilities is provided in accordance with an embodiment of the present invention.

[0091] Figure 2 A schematic diagram of the timing relationship among an inertial support, a primary frequency modulation and a fast frequency response in a system frequency response process proposed in an embodiment of the present invention;

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

[0093] Figure 4 A schematic diagram of a calculation model based on a regional power grid in a domestic city provided in an embodiment of the present invention.

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

[0095] Figure 6 A structural diagram of a device for planning urban power grid resilience enhancement taking into account extreme survivability dynamic capabilities provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0096] The 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 throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0097] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "one", "said", and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the 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 refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0098] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0099] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each embodiment does not constitute a limitation on the embodiments of the present invention.

[0100] Considering that the city power grid, including the power grids in each district, are the receiving-end power grids, and the voltage problem is mainly solved on-site, a large active power shortage will generally occur during extreme survival, and the dynamic frequency problem will be prominent. When designing a strong local power grid, it is necessary to consider the system's dynamic frequency response capability, that is, to consider all power generation resources in the local power grid, including the inverter interface power supply and the frequency support that can be provided by the synchronous machine power supply, to ensure that the dynamic frequency response capability of the surviving local power grid system meets the frequency stability under active power impact and ensure extreme survival.

[0101] When an extreme event causes the upper power receiving channel of the local power grid to be disconnected, the local power grid will unplannedly switch to island operation, and the local power grid needs to independently deal with active power impacts and keep frequency changes within a safe range. In the case of unplanned island survival limit, after an active power disturbance occurs, the frequency extremes and maximum frequency change rates of the local strong power grid need to be within the tolerable range of the system. The frequency dynamics of the power system are closely related to the balance of active power. The system frequency response dynamics can be divided into four stages: inertia response, primary frequency modulation, secondary frequency modulation, and tertiary frequency modulation. The dynamic capabilities of the present invention include inertia response and frequency dynamics within the primary frequency modulation time scale.

[0102] Example 1

[0103] A flowchart of a method for improving the resilience of an urban power grid considering the ultimate survivable dynamic capability provided by an embodiment of the present invention is as follows: Figure 1 As shown, the following processing steps are included:

[0104] Step S1: Obtain the demand analysis of extreme survival on the system's dynamic response capability.

[0105] Step S2: Based on the above demand analysis, a system extreme survival demand model is established that takes into account power supply composition and dynamic capabilities.

[0106] Step S3: Based on the above system extreme survival demand model, a multi-level self-balancing local power grid division and defense resource deployment optimization decision-making plan is proposed.

[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, the above step S1 includes: the frequency dynamics of each node of the power grid after the disturbance has a time-space distribution characteristic, and the frequency value not only changes with time, but also the frequency change process of each node is different. Therefore, the present invention uses the inertial center frequency to represent the system frequency, as shown in the following formula 1. This method has been widely adopted by relevant scholars in the study of system frequency response dynamic analysis.

[0109]

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

[0111] At the moment of grid disturbance (t 0+) is the moment when the unit inertia response begins, and the system frequency change rate (ROCOF) reaches the maximum. At the moment of fault, the governor and emergency control measures do not respond due to delays, and the unit mechanical power and emergency control resource power remain unchanged. Therefore, the frequency drop at this stage is only limited by the inertia response of the units in the network. The system frequency change rate at the moment of disturbance is:

[0112]

[0113] Where Hs is the system equivalent inertia time constant; W i is the rotor kinetic energy of unit i at rated speed; S i is the rated capacity of unit i; ΔP loss The power shortage of the system. If the frequency change rate exceeds the threshold value of the unit protection device, it will cause the unit to trip. The stronger the system inertia support capacity, the lower the frequency change rate under the same disturbance. According to the technical reports and literature of the National Grid of the United Kingdom, in the power system with a nominal frequency of 50Hz, the value range of ROCOF is 0.1Hz / s to 1.0Hz / s.

[0114] Due to the large active power shortage caused by the fault, the frequency will drop significantly, often reaching the lowest point within a time scale of seconds. After that, under the action of the primary frequency regulation and emergency frequency control measures of the power grid, the transient frequency gradually returns to a stable state. Throughout the process, different types of power sources respond to frequency changes at different time scales to suppress rapid frequency changes. Synchronous machines can provide inertia support and primary frequency regulation support, and the inverter interface power supply can provide fast frequency response through the control of the converter. Figure 2 A schematic diagram of the timing relationship between inertia support, primary frequency modulation and fast frequency response in the system frequency response process proposed in an embodiment of the present invention. Inertia support is an instant response, the primary frequency modulation of the synchronous machine has a delay, and the response time is 2 to 30 seconds, while the inverter interface power supply can respond within hundreds of milliseconds.

[0115] Based on the above analysis, the present invention uses the inertia support capacity, 100-millisecond response capacity and second-level response capacity of various types of resources to describe the dynamic frequency support capacity of resources according to the supporting role of power sources at different time scales of system frequency dynamics. Among them, the 100-millisecond response capacity and second-level response capacity include frequency response speed, response power and response energy. The dynamic response capacity of resources is measured based on the above indicators, and its relationship with the dynamic frequency response capacity of the local power grid system is further analyzed and expressed, mainly the lowest frequency point and the initial frequency change rate, which is convenient for consideration in the planning model.

[0116] According to the above analysis, the present invention establishes a strong local power grid system frequency dynamic capability response demand constraint suitable for planning and decision-making, which is defined as the dynamic response capability of various power sources within the local power grid to meet the system's sudden 50% power shortage to ensure the internal 20% load limit survival, and the dynamic process needs to maintain the frequency change rate and the lowest frequency point to meet 1Hz / s and 49Hz respectively. Among them, considering that the urban power grid is the receiving end power grid, the external power supply ratio generally does not exceed 50%, and the 50% power shortage is selected. For different sub-district power grids, it can be set in combination with the external power supply situation; at the same time, 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, the above step S2 includes: This step analyzes the process of the synchronous machine and the inverter interface power supply participating in the frequency response of the local power grid system, and then establishes the frequency security constraints of the local power grid system suitable for planning.

[0118] Figure 3 A schematic diagram of a multi-resource frequency response process provided by an embodiment of the present invention. Figure 3 As shown in Figure 2, according to the response time of different resources, the resource response capacity is divided into millisecond response and second response. Assume that the unit response increases linearly with time, and at time t E and t G After the full response, the full response time is between t E and t G The inverter interface power supply between E Conservative estimate, and assuming that time t E After that, the frequency modulation output of the unit will not increase any more to ensure the feasible result, that is:

[0119]

[0120] Where: P i (t) is the active power response capacity of the second level response; F n (t) is the fast frequency response capacity of 100 milliseconds response is the power of power source i that responds in seconds; is the power of the power source n that responds in 100 milliseconds; t G is the full response time in seconds; t E The full response time is in the hundreds of milliseconds. is the response ramp rate of the power supply i in seconds, is the response ramp rate of the power supply n in the hundreds of milliseconds.

[0121] The frequency dynamic change process of the power supply with a second-level response and the power supply with a hundred-millisecond-level response can be described by the first-order swing equation, that is:

[0122]

[0123] Where: Δf(t) is the frequency deviation; H is the system equivalent inertia time constant; D is the damping coefficient; P R，i (t)=∑ i P i (t)+∑ n F n (t), represents the resource response power of the system; P C (t) is the system dispatch control (emergency frequency control dispatch decision) response power; ΔP e is the disturbance power of the system.

[0124] The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) minimum frequency point. Different types of power sources can be deployed through collaborative optimization to ensure that the system has the ability 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] Where: H is the total inertia of the system, that is, the equivalent inertia time constant of the system; H i is the inertia constant of synchronous machine i; is the capacity of unit i; H n is the inertia constant of the inverter interface power supply n; is the rated power of the inverter interface power supply n. The frequency minimum point constraint is as follows:

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

[0131]

[0132] Where: H is the system equivalent inertia time constant; Δf(t) is the frequency deviation at time t; t E The full response time is 100 milliseconds; ΔP L is the load shedding amount; ΔP e is the disturbance power of the system.

[0133] Transform equation (8) and convert the per-unit value into a nominal value (taking the reference frequency f 0 is 50Hz), the frequency deviation at time t is:

[0134]

[0135] By setting the derivative of the frequency deviation to 0, the time when the frequency reaches the lowest point can be obtained from equation (5):

[0136]

[0137] Substitute equation (10) into equation (9), and then transform the frequency expression to obtain the frequency minimum point constraint:

[0138]

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

[0140] Specifically, the above step S3 includes: the local power grid planning principles are as follows:

[0141] First, the local strong power grid of the zoned power grid needs to cover all important loads; second, in principle, the number of protection levels of a certain 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 divided. Specifically, the power supply of super-important users is nearby, and the protection level at least includes the nearest network level with construction conditions; the power supply of first-level important users has the nearest network level or the upper level with construction conditions; the power supply of second-level important loads has at least one local power grid protection.

[0142] Resilience planning includes the demarcation of local grid boundaries and the deployment of defense resources. The principles of the two aspects are as follows:

[0143] The principles for deploying resources within a local power grid are as follows:

[0144] From the source side, it is necessary to consider the steady-state support capacity and dynamic support capacity of the internal power supply required for the extreme survival of the local power grid; from the grid side, it is necessary to consider 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 grid planners in combination with the actual needs of the grid. In addition, important loads may be connected to different voltage levels. Considering the differences in power supply capacity and capabilities at different levels, the following principles are determined: important loads cannot be guaranteed by the lower-level power supply, that is, the load cannot be guaranteed through the line of the next voltage level, and the power supply cannot be guaranteed through the line of the previous voltage level.

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

[0147] 1. Objective function

[0148] The extreme survivability of important loads depends on the power sources and power transmission channels that can supply them in extreme scenarios, that is, the number of power sources that guarantee their power supply. Therefore, the main goal is to maximize the number of guaranteed power sources for the load, considering the importance of the load as a weight. In addition, the closer the electrical distance between the guaranteed power source and the load, the higher the power supply reliability in extreme events. Therefore, the power supply distance is taken as a secondary goal.

[0149] max Rp L L+P γ (12)

[0150]

[0151] In the formula, R represents the weighted sum of the number of guaranteed power sources, that is, the number of power sources guaranteed for the load; p L is the weight coefficient, which indicates the importance of the final planning scheme to the power supply path; P γ is the penalty term for all local grid single commodity flow constraints; Indicates whether load i is in the local power grid centered on power source s, which 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; is a binary variable, indicating whether the important load l is guaranteed by the power source s; represents the length of the power supply path for the important load l guaranteed by the power source s; w l Indicates the importance level of the load node.

[0152] 2. Planning cost constraints

[0153]

[0154] In the formula, C represents the total cost required for planning; represents the upper limit of the planning budget cost; Indicates the new construction cost of lines, guaranteed power sources and substations; Indicates the upgrade costs of lines, guaranteed power supplies, and substations; They are all binary variables, indicating whether the resource is newly added; Both are binary variables, indicating whether the resource is upgraded.

[0155] The above formula comprehensively considers the new construction / upgrade costs of lines, power sources and substations, and constrains the budget upper limit.

[0156] (III) Constraints on single commodity flow in local power grids

[0157]

[0158] in It is a continuous variable, which indicates the virtual power flow through line (i, j) in the local power grid centered on power source s. i is a known variable, representing the virtual demand of non-root nodes (usually set to 1), M is a large positive real number (usually set to the number of nodes), B bus is a set of nodes, c i is the level of load i, c s The level where the power source s is located, c i,j is the level where the line (i,j) is located.

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

[0160] (IV) Multi-level protection constraints for important loads

[0161]

[0162]

[0163] In the formula, l is the load index, s is the power index, and i / j / k is the node index; represents the active power flowing through the line supplied by the power source s to the load l; p l represents the active power of load l; Indicates the active power supplied by power source s to load l; a ij is a binary variable, indicating whether line (i, j) is in an upgraded state, that is, whether line (i, j) has been upgraded / built; c l 、c s 、c ij Indicates the voltage level to which the component belongs; s is a binary variable, indicating whether the power supply s is added / upgraded; L i,j Indicates the length of the line; is a binary variable, indicating whether line (i, j) is energized when load l is powered by power source s; i,j Indicates that if line (i, j) is in the upgraded state, the weight of the line length is 1, otherwise it is 0; n 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, It represents the number of guaranteed power sources for load l at level c; They represent the super important user set, the first level important user set, and the second level important user set respectively; c is the hierarchical index.

[0167] (VI) Planning variable logic and budget constraints

[0168]

[0169]

[0170] In the formula, ε C , S C , Respectively represent the lines, power sources and substations to be built; ε 0 , S 0 , They represent the sets of lines, power sources and substations that do not need to be newly built; ε up , S up , Respectively represent the upgraded lines, power sources, and substations; β b It is a binary variable, indicating whether substation b is upgraded.

[0171] (VII) Local power grid dynamic response capability demand constraints

[0172]

[0173] In the formula, f RoCoF , is the ROCOF and safety limit after disturbance; f 0 is the frequency reference value; ΔP e,m is the power shortage of local power grid m; ΔP L,m is the load shedding power of the local power grid m; H is the equivalent inertia of the local power grid m; H i , H n They represent the inertia constants of the synchronous unit G and the inverter interface power supply E respectively; They respectively indicate whether the synchronous unit i and the inverter interface power supply n belong to the local power grid m; is the PFR power of synchronous machine i; is the FFR power of the inverter interface power supply n; Δf max Indicates the maximum frequency deviation allowed by the system; t E ,t G Respectively represent the complete response time of the inverter interface power supply and the synchronous unit.

[0174] A mixed integer nonlinear multi-level local power grid resilience planning optimization decision model was established, and the mixed integer nonlinear multi-level local power grid resilience planning optimization decision model was transformed into a mixed integer linear multi-level local power grid resilience planning optimization decision model using linearization methods such as McCormick relaxation. The mixed integer linear multi-level local power grid resilience planning optimization decision model was then solved using the mature solver Gurobi. The solution results include the capacity, location, type, inertia constant and active power regulation coefficient of the newly added power sources at each voltage level, the status information of line upgrade / reinforcement, and the node distribution of each island.

[0175] Specifically, the above step S4 includes: Figure 4 As shown, the example model of the power grid calculation based on a certain city in China constructed by the present invention covers four voltage levels of 220kV, 110 / 35kV, 10kV and 380V, showing the detailed distribution of multi-level power equipment and load nodes. A 220kV power plant is connected to the sub-district power grid, which is a black start unit and does not need to be upgraded. In addition, there are 6 220kV substations and 17 110 / 35kV substations in the sub-district. At the same time, for the convenience of analysis, only 10kV substations containing representative important loads are displayed, totaling 79. The system contains important loads of different levels, including 2 special loads, 5 first-level loads and 7 second-level loads, all of which are connected to 10kV substations to ensure the reliability and stability of power supply. There are rich connections between the voltages at various levels within the urban sub-district power grid. Under normal operation, each substation maintains electrical contact with only one upper-level substation, and the remaining lines are all normally open contact lines. Therefore, in the planning process, only the situation where each substation maintains electrical contact with only one upper-level substation is also considered. Assuming that all lines and substations can be upgraded, and taking into account urban space constraints, this project has planned 18 new power supply locations to be connected, including synchronous machines and energy storage.

[0176] The above problem is solved using the proposed method, and the planning strategy is obtained as follows: Figure 5 As shown, six 10kV local grids, three 110 / 35kV local grids and one 220kV local grid are formed.

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

[0178] The super load (the load at 69 in the figure) is protected by up to three levels of local power grid protection, namely, protection at the local level, protection at the upper level, and protection at the highest level. This three-level protection is because the super load is extremely important and its power supply must be highly reliable. As a key node, the power supply interruption of the super load may cause serious economic and social impacts. Therefore, triple protection measures are adopted in the design to minimize the risk of power outages and ensure continuous and stable power supply.

[0179] The primary load (such as the load at 53 in the figure) is protected by at most two levels of local power grid protection, namely the upper level protection and the highest level protection. Under the current planning rules, these loads require at least the protection of this level or the upper level protection, and considering that the primary load also plays a vital role, two levels of protection are arranged for the primary load as much as possible. Therefore, the primary load is protected by both the upper and the highest levels, but the primary load at 49 in the figure has only one level of protection, which is the highest level protection. This is because the load is very close to the 220kV power supply in terms of electrical distance, the stability of the 220kV power supply is also relatively reliable, and under the dual constraints of the local power grid dynamics and statics, budget constraints and topology constraints, only a single level of protection is given to the primary load.

[0180] The secondary load (such as the load at 85 in the figure) is protected by at least one level of local power grid, that is, the protection of this level. This is because the electrical distance between the secondary load and other important loads is far, and the importance is the least. Under the limited budget, it is sufficient to give priority to meeting its one-level protection needs. For these loads, a single-level protection can form a self-contained strong local power grid, which can quickly restore power supply and ensure power supply stability when a local fault occurs. Due to budget and space constraints, this strategy not only guarantees basic power supply needs, but also achieves the goal of optimizing resource allocation.

[0181] Example 2

[0182] The structure of a planning device for improving the resilience of an urban power grid considering the extreme survivability dynamic capability provided by an embodiment of the present invention is as follows: Figure 6 As shown, it includes the following modules:

[0183] Demand analysis acquisition module 61, used to obtain demand analysis of extreme survival on the dynamic response capability of the urban power grid system;

[0184] A system extreme survival demand model building module 62 is used to build a system extreme survival demand model that takes into account power supply composition and dynamic capability according to the demand analysis;

[0185] The urban power grid resilience improvement 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 improvement planning scheme.

[0186] Specifically, the demand analysis acquisition module 61 is used to use the inertia center frequency to represent the system frequency, and obtain the system frequency change rate at the moment of disturbance 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. According to the supporting role of the power supply at different time scales of the system frequency dynamics, the inertia support capacity, hundred-millisecond response capacity and second-level response capacity of various types of resources are used to describe the dynamic frequency support capacity of the resources, and a strong local power grid system frequency dynamic capacity response demand constraint suitable for planning decisions is established.

[0187] Specifically, the system extreme survival demand model building module 62 is used to divide the resource response capability into a hundred millisecond response and a second response according to the response time of different resources. The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) the lowest frequency point;

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

[0189] Specifically, the urban power grid resilience improvement planning scheme acquisition module 63 is used to set the following principles for the internal resource deployment of the local power grid: from the source side, the steady-state support capacity and dynamic support capacity of the internal power source required for the extreme survival of the local power grid are considered; from the grid side, differentiated reinforcement of the backbone grid connecting multiple source-load pairs is considered, and in principle, it is necessary to 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, the main objective is set to maximize the number of guaranteed power sources for the load, the secondary objective is set to the power supply distance, and the planning cost constraint, local power grid single commodity flow constraint, important load multi-level guarantee constraint, planning principle constraint, planning variable logic and budget constraint and local power grid dynamic response capability demand constraint of the objective function are set:

[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, and 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 mixed integer linear multi-level local power grid resilience planning optimization decision model is solved by a solver. The urban power grid resilience improvement planning scheme includes the capacity, location, type, inertia constant and active power regulation coefficient of new power sources at each voltage level, status information of line upgrade / reinforcement, and node distribution of each island.

[0192] The specific process of using the device of the embodiment of the present invention to carry out urban power grid resilience improvement planning taking into account the extreme survivability dynamic capacity is similar to the aforementioned method embodiment and will not be repeated here.

[0193] In summary, the urban power grid resilience improvement planning method considering the extreme survival dynamic capability of the present invention flexibly applies multi-level protection strategies according to factors such as the importance of the load and the electrical distance to ensure the power supply reliability of each level of load. It is ensured that when an extreme fault occurs, the urban power grid can smoothly switch to the local power grid operation and the frequency does not exceed the limit, reducing the economic losses and social impact caused by power outages, improving the stability and risk resistance of the overall power grid, and ensuring the efficient operation of the power system.

[0194] Those skilled in the art can understand that the accompanying drawings are only schematic diagrams of an embodiment, and the modules or processes in the accompanying drawings are not necessarily required to implement the present invention.

[0195] It can be known from the description of the above implementation methods that those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which can be stored in a storage medium such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention or certain parts of the embodiments.

[0196] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The device and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0197] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for improving the resilience of urban power grids considering extreme survivability, characterized in that: include: Obtain the demand analysis of the dynamic response capability of the urban power grid system for extreme survival; Based on the demand analysis, a system extreme survival demand model considering power supply composition and dynamic capability is established; A multi-level local power grid resilience planning optimization decision model is established based on the system extreme survival demand model, and the multi-level local power grid resilience planning optimization decision model is solved to obtain a city power grid resilience improvement planning scheme.

2. The method according to claim 1, characterized in that The demand analysis for obtaining extreme survival on the dynamic response capability of the urban power grid system includes: The inertia center frequency is used to represent the system frequency. The system frequency change rate at the moment of disturbance is obtained according to the system equivalent inertia time constant, the rotor kinetic energy of the unit at rated speed, the rated capacity of the unit and the system power shortage. According to the supporting role of the power supply at different time scales of the system frequency dynamics, the inertia support capacity, hundred-millisecond response capacity and second response capacity of various resources are used to describe the dynamic frequency support capacity of the resources, and a strong local power grid system frequency dynamic capacity response demand constraint suitable for planning and decision-making is established.

3. The method according to claim 2, characterized in that The demand analysis for obtaining extreme survival on the dynamic response capability of the urban power grid system includes: The inertial center frequency is used to represent the system frequency, as shown in the following equation 1: In the formula, f COI is the system inertia center frequency, i is usually the unit node, H gi is the inertia time constant of unit i, f i is the frequency of node i, denoted by f COI is f; Set the system frequency change rate at the moment of disturbance to: Where Hs is the system equivalent inertia time constant; W i is the rotor kinetic energy of unit i at rated speed; S i is the rated capacity of unit i; ΔP loss is the system power shortage; According to the supporting role of power sources at different time scales of system frequency dynamics, the inertia support capacity, hundred-millisecond response capacity and second-level response capacity of various types of resources are used to describe the dynamic frequency support capacity of resources, and a strong local power grid system frequency dynamic capacity response demand constraint suitable for planning and decision-making is established. It is defined as the dynamic response capacity of various types of power sources within the local power grid that can meet the system's sudden 50% power shortage to ensure the survival of the internal 20% load limit. The dynamic process needs to maintain the frequency change rate and the lowest frequency point to meet 1Hz / s and 49Hz respectively.

4. The method according to claim 2 or 3, characterized in that: According to the demand analysis, a system extreme survival demand model considering power supply composition and dynamic capability is established, including: According to the response time of different resources, the resource response capability is divided into 100 millisecond response and second response. The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) the lowest frequency point; The system's extreme survival demand model is composed according to the system's ROCOF, total inertia representation and frequency minimum point constraint.

5. The method according to claim 4, characterized in that According to the demand analysis, a system extreme survival demand model considering power supply composition and dynamic capability is established, including: According to the response time of different resources, the resource response capability is divided into 100 millisecond response and second response. The frequency dynamic change process of the power supply with second response and 100 millisecond response is described by the first-order swing equation, that is: Where: Δf(t) is the frequency deviation; H is the system equivalent inertia time constant; D is the damping coefficient; P R,i (t) = ∑ i P i (t)+∑ n F n (t), represents the resource response power of the system; P C (t) is the system dispatch control response power; ΔP e is the disturbance power of the system; The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) frequency minimum point; The ROCOF constraints are as follows: The total inertia of the system is expressed as Where: H is the total inertia of the system, that is, the equivalent inertia time constant of the system; H i is the inertia constant of synchronous machine i; is the capacity of unit i; H n is the inertia constant of the inverter interface power supply n; is the rated power of the inverter interface power supply n; the frequency minimum point constraint is as follows: Integrating both ends of equation (5) yields: Where: H is the system equivalent inertia time constant; Δf(t) is the frequency deviation at time t; t E The full response time is 100 milliseconds; ΔP L is the load shedding amount; ΔP e is the disturbance power of the system; Transform equation (8) and convert the per-unit value into a nominal value to obtain the frequency deviation at time t: By setting the derivative of the frequency deviation to 0, the time when the frequency reaches the lowest point is obtained from equation (5): Substituting equation (10) into equation (9), transforming the frequency expression, we obtain the frequency minimum point constraint as: Formulas (6), (7) and (11) form the system extreme survival demand model.

6. The method according to claim 5, characterized in that The multi-level local power grid resilience planning optimization decision model is established based on the system extreme survival demand model, and the multi-level local power grid resilience planning optimization decision model is solved to obtain the urban power grid resilience improvement planning scheme, including: The principles for setting up the internal resource deployment of the local power grid are as follows: from the source side, the steady-state support capacity and dynamic support capacity of the internal power supply required for the extreme survival of the local power grid should be considered; from the grid side, differentiated reinforcement of the main grid connecting multiple source-load pairs should be considered, and in principle, the distance between the power supply and the load should be ensured to be as close as possible; The objective function of the multi-level local power grid resilience planning optimization decision model is set, the main objective is set to maximize the number of guaranteed power sources for the load, the secondary objective is set to the power supply distance, and the planning cost constraint, local power grid single commodity flow constraint, important load multi-level guarantee constraint, planning principle constraint, planning variable logic and budget constraint and local power grid dynamic response capability demand constraint of the objective function are set: Based on the objective function and various constraints, a mixed integer nonlinear multi-level local power grid resilience planning optimization decision model is established, and 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 mixed integer linear multi-level local power grid resilience planning optimization decision model is solved by a solver. The urban power grid resilience improvement planning scheme includes the capacity, location, type, inertia constant and active power regulation coefficient of new power sources at each voltage level, status information of line upgrade / reinforcement, and node distribution of each island.

7. The method according to claim 6, characterized in that The objective function of the multi-level local power grid resilience planning optimization decision model is set, the main objective is set to maximize the number of guaranteed power sources for the load, the secondary objective is set to 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 capability demand constraint of the objective function are set, including: The objective function of the multi-level local power grid resilience planning optimization decision model is set as follows: Set the primary goal to maximize the number of guaranteed power sources for the load, and set the secondary goal to the power supply distance; max R-p L L+P γ (12) In the formula, R represents the weighted sum of the number of guaranteed power sources, that is, the number of power sources guaranteed for the load; p L is the weight coefficient, which indicates the importance of the final planning scheme to the power supply path; P γ is the penalty term for all local grid single commodity flow constraints; Indicates whether load i is in the local power grid centered on power source s, which 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; is a binary variable, indicating whether the important load l is guaranteed by the power source s; represents the length of the power supply path for the important load l guaranteed by the power source s; w l Indicates the importance level of the load node; The planning cost constraint of the objective function is set as: In the formula, C represents the total cost required for planning; represents the upper limit of the planning budget cost; Indicates the new construction cost of lines, guaranteed power sources and substations; Indicates the upgrade costs of lines, guaranteed power supplies, and substations; They are all binary variables, indicating whether the resource is newly added; They are all binary variables, indicating whether the resource is upgraded; The local grid single commodity flow constraint of the objective function is set as: in It is a continuous variable, which indicates the virtual power flow through line (i, j) in the local power grid centered on power source s. i is a known variable, representing the virtual demand of non-root nodes, M is a large positive real number, B bus is a set of nodes, c i is the level of load i, c s The level where the power source s is located, c i,j is the level where the line (i, j) is located; Formulas (18) and (19) are commodity flow constraints to ensure the connectivity of the graph. Formulas (20) and (21) are to meet the supply guarantee principle and realize the constraint that low-voltage power sources cannot supply power to high-voltage loads. The important load multi-level protection constraints of the objective function are set as follows: In the formula, l is the load index, s is the power index, and i / j / k is the node index; represents the active power flowing through the line supplied by the power source s to the load l; p l represents the active power of load l; Indicates the active power supplied by power source s to load l; a ij is a binary variable, indicating whether line (i, j) is in an upgraded state, that is, whether line (i, j) has been upgraded / built; c l 、c s 、c ij Indicates the voltage level to which the component belongs; s is a binary variable, indicating whether the power supply s is added / upgraded; L i,j Indicates the length of the line; is a binary variable, indicating whether line (i, j) is energized when load l is powered by power source s; i,j Indicates that if line (i, j) is in the upgraded state, the weight of the line length is 1, otherwise it is 0; n ij Used to characterize the importance of line (i, j) in system extreme survival; The planning principle constraints of the objective function are set as follows: In the formula, It represents the number of guaranteed power sources for load l at level c; They represent the super important user set, the first level important user set, and the second level important user set respectively; c is the hierarchical index; The planning variable logic and budget constraints of the objective function are set as follows: In the formula, ε C , δ C , Respectively represent the lines, power sources, and substations to be built; ε0, δ, They represent the sets of lines, power sources and substations that do not need to be newly built; ε up , Sδ up , Respectively represent the upgraded lines, power sources, and substations; β b is a binary variable, indicating whether substation b is upgraded; The local power grid dynamic response capability requirement constraint of the objective function is set as: In the formula, f RoCoF , is the ROCOF and safety limit after disturbance; f0 is the frequency reference value; ΔP e,m is the power shortage of local power grid m; ΔP L,m is the load shedding power of the local power grid m; H is the equivalent inertia of the local power grid m; H i , H n They represent the inertia constants of the synchronous unit G and the inverter interface power supply E respectively; They respectively indicate whether the synchronous unit i and the inverter interface power supply n belong to the local power grid m; is the PFR power of synchronous machine i; is the FFR power of the inverter interface power supply n; Δf max Indicates the maximum frequency deviation allowed by the system; t E ,t G Respectively represent the complete response time of the inverter interface power supply and the synchronous unit.

8. A planning device for improving the resilience of urban power grids taking into account extreme survivability, characterized in that: include: Demand analysis acquisition module, used to obtain demand analysis of extreme survival on the dynamic response capability of the urban power grid system; A system extreme survival demand model establishment module is used to establish a system extreme survival demand model that takes into account power supply composition and dynamic capabilities based on the demand analysis; The urban power grid resilience improvement 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 improvement planning scheme.

9. The device according to claim 8, characterized in that The demand analysis acquisition module is used to use the inertia center frequency to represent the system frequency, and obtain the system frequency change rate at the moment of disturbance based on 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. According to the supporting role of the power supply at different time scales of the system frequency dynamics, the inertia support capacity, the hundred-millisecond response capacity and the second-level response capacity of various resources are used to describe the resource dynamic frequency support capacity, and a strong local power grid system frequency dynamic capacity response demand constraint suitable for planning decisions is established.

10. The device according to claim 9, characterized in that The system extreme survival demand model establishment module is used to divide the resource response capability into hundreds of milliseconds response and seconds response according to the response time of different resources. The power system frequency security indicators considered in the planning process include: 1) ROCOF; 2) the lowest frequency point; The system's extreme survival demand model is composed according to the system's ROCOF, total inertia representation and frequency minimum point constraint.

11. The device according to claim 10, characterized in that The urban power grid resilience improvement planning scheme acquisition module is used to set the following principles for the internal resource deployment of the local power grid: from the source side, the steady-state support capacity and dynamic support capacity of the internal power source required for the extreme survival of the local power grid are considered; from the grid side, differentiated reinforcement of the backbone grid connecting multiple source-load pairs is considered, and in principle, it is necessary to 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 objective is set to maximize the number of guaranteed power sources for the load, the secondary objective is set to the power supply distance, and the planning cost constraint, local power grid single commodity flow constraint, important load multi-level guarantee constraint, planning principle constraint, planning variable logic and budget constraint and local power grid dynamic response capability demand constraint of the objective function are set: Based on the objective function and various constraints, a mixed integer nonlinear multi-level local power grid resilience planning optimization decision model is established, and 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 mixed integer linear multi-level local power grid resilience planning optimization decision model is solved by a solver. The urban power grid resilience improvement planning scheme includes the capacity, location, type, inertia constant and active power regulation coefficient of new power sources at each voltage level, status information of line upgrade / reinforcement, and node distribution of each island.

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