Risk assessment method and system for loop-closing reverse load operation based on analytic hierarchy process

Abstract

The present invention belongs to the field of risk analysis in power systems and provides a loop closing and load reversal operation risk assessment method and system based on a hierarchical analysis method. The method comprises obtaining a live loop closing and load reversal scheme of a distribution network, a grid topology structure and equipment parameters of an area where live loop closing and load reversal of the distribution network is required, determining the causal relationship between relevant factors affecting the risk of the loop closing and load reversal operation, and constructing a hierarchical analysis structure model; based on the hierarchical analysis structure model, performing pairwise comparisons on factors in each intermediate level to establish multiple hierarchical judgment matrices; calculating matrix characteristic roots according to the hierarchical judgment matrices to obtain weights of the importance of factors corresponding to the hierarchical judgment matrices to factors in the previous level; performing a consistency check on all hierarchical judgment matrices; and ranking all loop closing schemes according to the comprehensive weights of the hierarchical judgment matrices to obtain risk levels of different loop closing schemes. This improves the accuracy of risk assessment of loop closing operation schemes.

Description

Technical Field

[0001] The present invention belongs to the technical field of risk analysis in power systems, and in particular relates to a loop-closing load reversal operation risk assessment method and system based on a hierarchical analysis method. Background Art

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

[0003] During normal operation, the 10kV distribution network is often in an open-loop operation state. When a 10kV feeder needs to be repaired, the traditional power outage-to-power operation will inevitably cause a short power outage, which is no longer able to meet people's requirements for power supply reliability. The closing-loop load reversal operation ensures continuous power supply and reduces the scope of power outage by first closing the tie switch and then opening the feeder outgoing line switch. This not only enhances the power supply reliability of the distribution network, but also ensures the power supply flexibility of the distribution network, while improving the operating economy of the distribution network.

[0004] Transmission backbone networks (such as 500kV and 220kV) all use a ring transmission method, while distribution networks and busbars at voltage levels of 110kV and below all use a closed-loop design and open-loop operation. If a 10kV busbar or its feeders need to be repaired or decommissioned, the interconnecting switch should be closed to achieve the purpose of transferring feeder loads without power outages and ensure power supply continuity. The above method of closing the interconnecting switch is called a ring closing operation. The ring closing operation of a 10kV power grid should assess the risks of the specific ring closing operation plan, and then comprehensively evaluate the size of the ring closing operation safety risk and determine the level of the ring closing operation safety risk.

[0005] While achieving uninterrupted power transfer, the loop-closing operation also transitions the 10kV distribution network from open-loop operation to closed-loop operation. Because a voltage difference (including voltage amplitude and phase angle differences) exists on both sides of the loop-closing point before the loop-closing operation, and the feeder loads and line impedance parameters on both sides may be unevenly distributed, loop-closing currents and loop-closing surge currents are generated in the loop-closing branch (the branch where the loop-closing tie switch is located) and distributed to other branches in the loop-closing network. Excessive loop-closing steady-state currents can cause line overloads, while excessive loop-closing surge currents can cause line current protection to malfunction, both of which are the main causes of loop-closing operation failures. Therefore, to prevent loop-closing operations from causing line overloads or protective tripping, a risk assessment of the loop-closing operation is required before closing the loop.

[0006] Existing closed-loop operation risk assessments are mostly based on the experience and judgment of operation and maintenance personnel. They are unable to quantitatively assess the risks of closed-loop operation plans, and there is no risk level assessment method. Summary of the Invention

[0007] In order to solve the above problems, the present invention proposes a method and system for risk assessment of loop-closing and load-reversing operations based on the hierarchical analysis method. The present invention constructs a hierarchical analysis structure matrix that includes the causal relationship between relevant factors affecting the risk of loop-closing and load-reversing operations. The risk levels of different loop-closing schemes are evaluated by calculating the influence weights of multiple influencing factors. The risk level with the largest weight is the lowest, and so on. This provides operation and maintenance personnel with a scientific basis for risk judgment of different loop-closing and load-reversing schemes, thereby improving the accuracy of risk assessment.

[0008] According to some embodiments, a first solution of the present invention provides a loop-closing load reversal operation risk assessment method based on the analytic hierarchy process, which adopts the following technical solutions:

[0009] The risk assessment method for loop-closing reverse load operation based on the analytic hierarchy process includes:

[0010] Obtain the live closing and load reversal scheme for the distribution network, the grid topology and equipment parameters for the area where live closing and load reversal are required, determine the causal relationship between the relevant factors affecting the risk of closing and load reversal operations, and construct a hierarchical analysis structure model;

[0011] Based on the hierarchical analysis structure model, the factors in each middle layer are compared pairwise and multiple middle-level judgment matrices are established;

[0012] Calculate the matrix characteristic root according to the intermediate level judgment matrix to obtain the weight of the importance of the factors corresponding to the intermediate level judgment matrix to the factors in the upper level;

[0013] Perform consistency checks on all intermediate-level judgment matrices;

[0014] According to the comprehensive weight of the intermediate-level judgment matrix, all the loop closure schemes are ranked to obtain the risk levels of different loop closure schemes.

[0015] Furthermore, the equipment parameters include the operating mode, load size, transformer gear and reactive compensation input status on both sides of the closing point during the planned closing operation time period, the operating parameters of the overhead lines, cables, transformers, mutual inductors, switchgear, and reactive compensation equipment of the systems on both sides of the closing point, as well as the load type area to which the closing operation location belongs and the power supply status on different dates.

[0016] Furthermore, the causal relationship between the relevant factors affecting the risk of loop-closing reverse load operation is determined, and a hierarchical analysis structure model is constructed, including:

[0017] Analyze the characteristics of each grid topology and determine the factors that affect the risk of loop-closing reverse load operation;

[0018] Determine the sub-factors that affect each factor and the causal relationship between them, and establish a hierarchical analysis structure model;

[0019] Among them, relevant factors include grid operation factors, load distribution, operation area division and social factors. The social factors include three situations of power supply on weekdays, holidays and important schedules. Each situation corresponds to different grid operation safety, stability and power quality requirements.

[0020] Furthermore, the hierarchical analysis structure model is composed of a target layer, an intermediate layer and a closing scheme layer from top to bottom; wherein the top layer is the target layer, the bottom layer is the closing scheme layer, and the intermediate layer includes multiple criterion layers;

[0021] The target layer is used to provide a risk assessment level for loop closing operations, and the criterion layer is used to rank various indicators that affect loop closing operation risks and classify them according to actual conditions. The loop closing scheme layer includes typical live loop closing and load reversal schemes for distribution networks.

[0022] Among them, the various indicators that affect the risk of loop closure operations are: grid operation indicators, load conditions, operation areas, and social factors;

[0023] The indicators that affect the operation of the power grid are divided into the voltage difference on both sides of the closing point, the closing current, and the phase angle difference on both sides of the closing point; the factors of the load situation are divided into general load, civil and important industrial load, medical, government power supply load and important large user load; the operating area is divided into four types of areas ABCD according to the load distribution standard. The division standard is based on the actual economic development of different regions and the objective differences in medium and low voltage distribution networks. The benchmark values ​​of energy efficiency evaluation indicators are selected according to the four categories of areas A, B, C, and D; social factors mainly consider the three situations of power supply on weekdays, holidays and important schedules, and each situation corresponds to different power grid operation safety, stability and power quality requirements.

[0024] Furthermore, the calculation of the comprehensive weight includes:

[0025] Use the maximum eigenvalue λ of the comparison matrix of the second layer elements max The corresponding eigenvector is used as the weight vector ω of the second layer element (2) ;

[0026] Similarly, we get the weight vector of the third layer to each element of the second layer Then the weight vector matrix of the third layer is Therefore, the combined weight vector of the third layer for the target layer is ω (3) =W (3) ·ω (2) ;

[0027] By analogy, if we push it to the hth layer, the final comprehensive weight is:

[0028] ω (h) =W (h) W (h-1) W (h-2) …W (3) ·ω (2)

[0029] Among them, W (j) It is the weight vector matrix composed of the weight vectors of the j-1 layer for the j-1 layer. The calculated comprehensive weight is used as the quantitative basis for the risk assessment of the decision-making loop operation plan, and the larger the weight, the higher the risk.

[0030] Furthermore, the weight of the importance of the factors corresponding to each intermediate level judgment matrix to the factors in the previous level is modified by using the method of computational quantitative analysis, including:

[0031] Considering the different closing currents in different closing schemes, the weights of the closing impulse current and the closing steady-state circulating current in each intermediate layer judgment matrix on the closing current in power grid operation are modified;

[0032] By using the feeder current before the loop is closed and the impact circulating current of the additional ring network during the loop closing, the expression of the full current of the loop closing impact current after the loop is closed is determined and solved to obtain the loop closing impact current;

[0033] The closed-loop steady-state current after closing is determined by using the difference in effective voltage values ​​and voltage phase angle between the two sides of the open-loop connection before closing.

[0034] The closing point closing impulse current and the closing steady-state circulating current are normalized to per unit using the rated current value of the transformer;

[0035] The influence weights of the closing point closing impact current and the closing steady-state circulating current on the current factors are obtained.

[0036] Furthermore, the full current expression of the closed-loop impact circulating current is:

[0037]

[0038] From this formula, we can get the closing point closing impact current, that is, the maximum value of i when closing the loop. max ;δ represents the phase angle difference of the voltage across the switch when the loop is closed; I c is the effective value of the steady-state circulating current, φ is the impedance angle of the closed-loop equivalent model; T = L / R is the decay time constant of the non-periodic component, ω=2πf;

[0039] The closed-loop steady-state circulation is expressed as:

[0040]

[0041] Where U is the effective value of the voltage vector difference across the closing switch when the loop is closed, the effective value difference of the voltage across the tie switch before closing is △U, and |Z| represents the modulus of the loop impedance.

[0042] According to some embodiments, a second solution of the present invention provides a loop-closing load reversal operation risk assessment system based on the analytic hierarchy process, which adopts the following technical solutions:

[0043] The loop-closing load reversal operation risk assessment system based on the analytic hierarchy process includes:

[0044] A hierarchical analysis structure model construction module is configured to obtain a live loop closing and load reversal plan for the distribution network, the grid topology and equipment parameters of the area where live loop closing and load reversal are required, determine the causal relationship between relevant factors affecting the risk of loop closing and load reversal operations, and construct a hierarchical analysis structure model;

[0045] The hierarchical judgment matrix calculation module is configured to compare the factors in each intermediate level with each other based on the hierarchical analysis structure model to establish multiple hierarchical judgment matrices;

[0046] A matrix characteristic root calculation module is configured to calculate the matrix characteristic root according to the hierarchical judgment matrix to obtain the weight of the importance of the factors corresponding to the hierarchical judgment matrix to the factors in the previous layer;

[0047] A consistency check module is configured to perform consistency checks on all hierarchical judgment matrices;

[0048] The risk level assessment module is configured to sort all the loop closure schemes according to the comprehensive weight of the hierarchical judgment matrix to obtain the risk levels of different loop closure schemes.

[0049] According to some embodiments, a third aspect of the present invention provides a computer-readable storage medium.

[0050] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the loop-closing load reversal operation risk assessment method based on the hierarchical analysis method as described in the first aspect above.

[0051] According to some embodiments, a fourth aspect of the present invention provides a computer device.

[0052] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the method for risk assessment of loop-closing load reversal operation based on the hierarchical analysis method as described in the first aspect above are implemented.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The present invention describes a risk assessment method for live loop closing and load reversal operations in distribution networks. This method can effectively avoid the problems of being too subjective and taking into account only a single factor in the existing direct empirical judgment method used in risk assessment of live loop closing and load reversal operations in distribution networks. The assessment process not only focuses on the effects of voltage, current, and phase angle on the operation of the power grid before and after closing, but also considers the highly coupled relationship between factors such as the uneven distribution of power grid loads between regions under different distribution network topologies and social factors of load characteristics. It is a multi-factor coupling analysis method.

[0055] The present invention comprehensively considers the influence of the coupling between the distribution network topology, load distribution, regional load characteristics and social factors on the live loop closing and load reversal operation of the distribution network, and refines the weights of the risk factors affecting the loop closing and load reversal operation according to the mutual importance of different factors, constructs a hierarchical analysis structure matrix containing the causal relationship between the relevant factors affecting the risk of loop closing and load reversal operation, and evaluates the risk level of different loop closing schemes by calculating the influence weights of multiple influencing factors. The risk level with the largest weight is the highest, and so on. The present invention considers the coupling of multiple factors. Compared with the traditional empirical judgment method, the evaluation process is scientific and reasonable, thereby providing operation and maintenance personnel with a scientific basis for risk judgment of different loop closing and load reversal schemes. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0057] Figure 1 This is a flow chart of a loop-closing load reversal operation risk assessment method based on the analytic hierarchy process according to an embodiment of the present invention;

[0058] Figure 2 Schematic diagram of a ring closing scheme with different closing points according to an embodiment of the present invention;

[0059] Figure 3 is a structural diagram of the hierarchical analysis structure model according to an embodiment of the present invention;

[0060] Figure 4 It is the equivalent model for closed-loop impact circulation calculation described in the embodiment of the present invention;

[0061] Figure 5 2 is a voltage vector relationship diagram according to an embodiment of the present invention. DETAILED DESCRIPTION

[0062] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0063] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0064] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0065] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0066] Example 1

[0067] like Figure 1 As shown, this embodiment provides a method for risk assessment of closed-loop load reversal operations based on the hierarchical analysis method. This embodiment uses the method applied to a server as an example. It can be understood that the method can also be applied to a terminal, and can also be applied to a system including a terminal, a server, and a server, and implemented through the interaction between the terminal and the server. The server can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network servers, cloud communications, middleware services, domain name services, security services CDN, and big data and artificial intelligence platforms. The terminal can be a smart phone, tablet computer, laptop computer, desktop computer, smart speaker, smart watch, etc., but is not limited to this. The terminal and the server can be directly or indirectly connected by wired or wireless communication, and this application does not limit this. In this embodiment, the method includes the following steps:

[0068] Obtain the live closing and load reversal scheme for the distribution network, the grid topology and equipment parameters for the area where live closing and load reversal are required, determine the causal relationship between the relevant factors affecting the risk of closing and load reversal operations, and construct a hierarchical analysis structure model;

[0069] Based on the hierarchical analysis structure model, the factors in each middle layer are compared pairwise and multiple middle-level judgment matrices are established;

[0070] Calculate the matrix characteristic root according to the intermediate level judgment matrix to obtain the weight of the importance of the factors corresponding to the intermediate level judgment matrix to the factors in the upper level;

[0071] Perform consistency checks on all intermediate-level judgment matrices;

[0072] According to the comprehensive weight of the intermediate-level judgment matrix, all the loop closure schemes are ranked to obtain the risk levels of different loop closure schemes.

[0073] In a specific embodiment, the method includes:

[0074] 1. Classification of loop closure solutions

[0075] The closing operation can be classified into the following categories according to the differences in the upper power supply, main transformer and distribution line. The classification of the closing operation mode is as follows: Figure 2 shown.

[0076] (1) Busbar type ring closing. Figure 2 In this example, the tie switch K1 is directly connected to the 10kV busbar. This type of closing operation is called busbar closing. Busbar closing control is generally smooth and is frequently performed in actual operation.

[0077] (2) Feeder type loop. Figure 2 In the circuit breaker, the closing operation is performed at the tie switches K2, K3, and K4. This type of closing operation can be collectively referred to as feeder closing operation.

[0078] However, due to the differences in their respective upstream power sources, even though they are all closed loop operations between 10kV feeders, feeder-type closed loop operations can still be divided into three different types:

[0079] 1) Closing feeders within the same zone and substation, such as the closing at tie switch K2, involves feeders on both sides of the closing point belonging to the same substation B and within the same 220kV zone. Because the feeder loads are symmetrical and the line parameters are similar, this type of closing control is relatively simple and safe. This type of closing operation is both the simplest and safest.

[0080] 2) This type of closing applies to feeder loops between different 10kV busbars within the same substation and substation. For example, tie breaker K5 participates in this type of closing. Because the transformers are of the same or similar type, differing only in their transformation ratios and feeder load distribution, these differences are relatively small in real-world power grids. Furthermore, the bus tie breaker ensures safety in closing the loop during a fault, making this type of closing relatively safe.

[0081] 3) For the closing of feeders between different substations in the same zone, such as the closing at the tie switch K3, the feeders on both sides of the closing point belong to the same 220kV zone but belong to different substations A and B respectively. The transformer short-circuit impedance, transformer ratio and feeder impedance on both sides of the tie switch will affect the voltage difference on both sides of the tie switch.

[0082] 4) Closing feeders between different zones and substations, such as the one at tie switch K4, involves feeders on both sides of the closing point not only not being in the same 220kV zone but also belonging to different substations, B and C. This type of closing operation is relatively complex and carries significant risks. The voltage difference across the tie switch is also affected by differences in the main transformer capacity of the main substation and the operating mode of the upstream power grid. The high-voltage side network and load are also significantly different, resulting in significant circulating currents in the closed network.

[0083] 2. Problems

[0084] While achieving uninterrupted power transfer, the loop-closing operation also transitions the 10kV distribution network from open-loop operation to closed-loop operation. Because a voltage difference (including voltage amplitude and phase angle differences) exists on both sides of the loop-closing point before the loop-closing operation, and the feeder loads and line impedance parameters on both sides may be unevenly distributed, loop-closing currents and loop-closing surge currents are generated in the loop-closing branch (the branch where the loop-closing tie switch is located) and distributed to other branches in the loop-closing network. Excessive loop-closing steady-state currents can cause line overloads, while excessive loop-closing surge currents can cause line current protection to malfunction, both of which are the main causes of loop-closing operation failures. Therefore, to prevent loop-closing operations from causing line overloads or protective tripping, a risk assessment of the loop-closing operation is required before closing the loop.

[0085] 3. Risk Assessment Methods

[0086] This embodiment provides a method for assessing the risk of loop-closing reverse load operations based on the hierarchical analysis method. By establishing a hierarchical analysis structure model, the risk level under different loop-closing operation schemes is determined. The established hierarchical analysis structure model includes, from top to bottom, a target layer, a criterion layer, and a scheme layer.

[0087] The target layer is used to give the risk assessment level of the closed-loop operation.

[0088] The criterion layer is used to rank and classify various indicators affecting loop closing operational risk based on actual conditions. The indicators affecting loop closing operational risk are: grid operation indicators, load conditions, operating area, and social factors. Among them, the indicators affecting grid operation are further divided into the voltage difference across the loop closing point, the loop current, and the phase angle difference across the loop closing point. The loop current is further divided into the loop inrush current and the loop steady-state circulating current. Factors affecting load conditions are further divided into general loads, civil and important industrial loads, medical, government and other power supply loads, and important large-scale user loads. The operating area is divided into four types of regions based on load distribution standards: A, B, C, and D. This classification standard is implemented in accordance with the "Guidelines for Energy Efficiency Assessment of Medium and Low Voltage Distribution Networks" (GBT31367-2015). Based on the actual economic development conditions and objective differences in medium and low voltage distribution networks in different regions of China, the benchmark values ​​for energy efficiency assessment indicators are selected according to the four categories of regions: A, B, C, and D. Developed urban networks (Class A areas) refer to urban networks in economically developed and densely populated areas with a load density greater than 10MW per square kilometer. Urban power grids (Class B areas) refer to built-up or planned urban areas. Exurban areas (or areas converted from counties to districts) only include district government seats, economic development zones, and industrial parks. Load densities range from 5 to 10 MW per square kilometer. Urban and rural central areas (Class C areas) refer to urban areas within counties (county-level cities, banners) and relatively concentrated industrial and populated townships and towns. Load densities range from 1 to 5 MW per square kilometer. Rural power grids (Class D areas) refer to areas primarily centered on agriculture, with load densities less than 1 MW per square kilometer. Social factors primarily consider three scenarios: ensuring power supply on weekdays, holidays, and important dates. Each scenario corresponds to different requirements for grid operation safety, stability, and power quality.

[0089] The scheme layer is a typical distribution network live loop closing and load reversal loop closing scheme.

[0090] 3.1 Specific steps

[0091] Step 1: Establish a hierarchical analysis structure model to obtain the grid topology and related equipment parameters of the area where the distribution network needs to be energized and closed, including the operation mode, load size, transformer gear and reactive compensation input on both sides of the closing point. The above parameters should be the actual status of the planned closing operation time period. At the same time, the overhead lines, cables, transformers, mutual inductors, switchgear, reactive compensation and other equipment on both sides of the closing point should use measured parameters. If there is no source of measured parameters, refer to the measured data or typical parameters of the same model equipment, and judge the load type area and social factors related to the closing operation point according to regulations. Analyze the characteristics of each topology, sort out the relevant factors that affect the risk of closing and reverse load operation, including grid operation factors, load distribution, operation area division and social factors, determine the sub-factors affecting each factor and the causal relationship between them, and establish a multi-level ladder structure model;

[0092] Step 2: Construct a weighted discriminant matrix. Based on the multi-level ladder structure model established in step 1, compare the elements at the same intermediate level with each other. According to a total of 9 gradient-decreasing weights from absolutely important to equally important, give the importance discriminant matrix of the previous level and establish a judgment matrix. Similarly, perform the above operation for each level.

[0093] Step 3: Calculate the matrix characteristic root based on the judgment matrix determined in step 2, which is the weight of the importance of the elements of this layer represented by the matrix to the elements of the previous layer;

[0094] Step 4: Verify the consistency of the sorting by calculation;

[0095] Step 5: Sort all the closing schemes from large to small according to the comprehensive weight, so as to give the risk level of different closing schemes. The risk level with the largest weight is the smallest, and so on, thereby providing operation and maintenance personnel with a scientific basis for risk judgment of different closing and load reversal schemes.

[0096] 3.2 Modeling process

[0097] 3.2.1 Establishing a hierarchical model

[0098] like Figure 3 As shown in the figure, the various factors affecting the risk of loop-closing reverse load operation are decomposed into several levels from top to bottom according to different attributes. The top layer is the target layer, the last layer is the loop-closing plan layer, and the middle part is the criterion layer. The various factors in the same layer are subordinate to the factors in the upper layer or have an impact on the factors in the upper layer, and at the same time dominate the factors in the lower layer or are affected by the factors in the lower layer.

[0099] 3.2.2 Constructing a pairwise comparison matrix

[0100] A priority matrix is ​​established between the elements of the hierarchy through comparison and a series of judgments on the elements of the same layer.

[0101] (1) Estimate the importance of each factor. In this model, the target layer to the solution layer are divided into A, B, C, D, and E layers from top to bottom. Taking the B layer as an example, assume that this layer has n elements Bb1...Bbn. Compare them two by two. According to the scale in Table 1 below, use one of the numbers 1 to 9 to represent the relative importance of Bbi to the target A, thereby forming a comparison matrix UB. Similarly, the comparison matrices UC, UD, and UE are formed respectively, that is, the comparison matrices of the criterion layer to the target layer and the solution layer to the criterion layer are formed.

[0102] Table 1 Scale and its meaning

[0103] scale meaning 1 Indicates that two factors are equally important. 3 Indicates that one factor is slightly more important than the other factor. 4 Indicates that one factor is significantly more important than the other when comparing two factors. 7 Indicates that one factor is more important than the other. 9 Indicates that one factor is extremely more important than the other. 2,4,6,8 The median of the two adjacent judgments above

[0104] Among them, the scale of the two elements i to j and the scale of j to i are reciprocals of each other.

[0105] (2) Find the maximum characteristic root λ of the above price ratio matrix max , that is, Uω=λ max ω, where ω is the weight vector of n elements.

[0106] (3) Consistency test: To ensure the consistency of the judgment matrix, reduce λ max and ω deviation, the matrix consistency test is required, because the maximum characteristic root λ of the n-order positive reciprocal matrix max ≥n, when λ max =n, it is a consistent matrix.

[0107] Define consistency indicators:

[0108]

[0109] And define the consistency ratio: Among them, RI takes values ​​according to the following table:

[0110] Table 2 RI value reference table

[0111] Order 3 4 5 6 7 8 9 10 11 12 13 14 15 RI 0.52 0.89 1.12 1.26 1.36 1.41 1.46 1.49 1.52 1.54 1.56 1.58 1.59

[0112] When CR < 0.1, the consistency of the matrix is ​​considered acceptable; when CR ≥ 0.1, the comparison matrix should be appropriately modified and then the consistency test should be performed again until it passes the consistency test.

[0113] (4) Calculate the combined weight vector

[0114] Use the maximum eigenvalue λ of the comparison matrix of the second layer elements max The corresponding eigenvector is used as the weight vector ω of the second layer element (2) , the same method is used to obtain the weight vector of the third layer for each element of the second layer Then the weight vector matrix of the third layer is Therefore, the combined weight vector of the third layer for the target layer is ω (3) =W (3) ·ω (2) , and so on. If we push it to the hth layer, the final combined weight vector is:

[0115] ω (h) =W (h) W (h-1) W (h-2) …W (3) ·ω (2) (2)

[0116] Among them, W (j)This is the weight vector matrix composed of the weight vectors of the jth layer for the j-1th layer. The size of the calculated combined weight vector can be used as a quantitative basis for risk assessment of the decision-making loop solution, and the larger the weight, the higher the risk.

[0117] (5) Weight correction

[0118] For the criterion layer grid operation elements that affect the risk of the closing point, since they are affected by voltage, current, and phase angle, and the current is affected by the closing impact current and the closing steady-state circulating current, but the values ​​of the closing impact current and the closing steady-state circulating current are inconsistent under different closing schemes, their effects on the current elements are also inconsistent. Under different closing schemes, the impact of the steady-state circulating current and the closing impact current on the grid operation needs to be determined after calculation and quantification; the impact of voltage and phase angle on the grid operation during closing operation can be quantified based on on-site measurement values, and the three elements of load, operation area, and social factors can be determined after the scheme is determined, without the need to correct the calculation weights. Therefore, in order to avoid the judgment of the importance comparison between different elements being too subjective, this paper uses the method of calculation and quantitative analysis to correct the weights of the relevant criterion layers. The specific correction method is as follows:

[0119] When performing the loop closing operation, the impact of the instantaneous impact current generated by the loop closing must be considered. Excessive loop closing impact current may not only cause the current quick-break protection to operate, resulting in unnecessary power outages, but may also cause accidents such as switch explosions. The impact current at the feeder head end at the moment of loop closing is also the superposition of the feeder current before the loop closing and the impact circulating current of the additional ring network during the loop closing. Figure 4 The model shown derives the expression for the full current at the closing point.

[0120] During the closing process, fault conditions and abnormal conditions are not considered. In other words, under normal circumstances, the system operates in a three-phase symmetrical manner, so the analysis of one of the three conditions can be simplified. Ignoring the line susceptance in the distribution network, using the Thevenin theorem, looking from the closing port to the network, the closing transient impulse circulation model is as follows: Figure 4 In the figure above, R+jX represents the equivalent impedance after the loop is closed, U is the effective value of the voltage vector difference across the closed-loop switch when the loop is closed, and δ represents the voltage phase angle difference across the switch when the loop is closed.

[0121] After closing the ring, Figure 4 The circuit shown has the following differential equation:

[0122]

[0123] The solution of this differential equation is the total current of the closed-loop impulse current, which consists of two parts. The first part is the special solution of this equation, which represents the periodic component i of the impulse current. c , which is the closed-loop steady-state circulation, the second part is called the free component or the non-periodic component, denoted by iap It can be solved as:

[0124]

[0125] Where, is the effective value of the steady-state circulating current, is the impedance angle of the closed-loop equivalent model. The solution is:

[0126] i ap =Cexp(-t / T) (5)

[0127] Where T = L / R is the decay time constant of the non-periodic component, ω=2πf。

[0128] The full current expression of the closed-loop impulse current can be obtained by sorting:

[0129]

[0130] The closing point closing impact current can be obtained from this formula, that is, the maximum value of i when the loop is closed. max .

[0131] After closing the loop, both the steady-state current and the surge current at the feeder head end are related to the steady-state circulating current of the closed loop. The voltage vector diagram of the two ends of the tie switch before closing the loop is as follows: Figure 5 As shown, Figure 5 Where δ is the phase angle difference of the voltage across the tie switch before closing the loop, U a 、U b , are the line voltage vector values ​​on both sides of the tie switch before closing the loop, then according to the cosine theorem:

[0132]

[0133] Since we are concerned about the effect of the effective value difference of the voltage on both sides of the tie switch on the closing operation, let the effective value difference of the voltage on both sides of the tie switch before closing be △U, so we have:

[0134]

[0135] In the distribution network, the allowable voltage deviation range is ±7%, taking the rated voltage as 10V. The value range of is between 9.3kV and 10.7kV, so the value range of △U is between 0kV and 1.4kV. Since the most serious situation needs to be considered when closing the loop, Taking the value 10.7kV and substituting it into formula (8) we can get the maximum voltage difference that may occur at this time, as shown in formula (9):

[0136]

[0137] In the closed loop operation, the closed loop steady-state circulating current can be approximately expressed as follows:

[0138]

[0139] The rated current i of the transformer r The closing point closing impact current and the closing steady-state circulating current are normalized to per unit, that is:

[0140]

[0141]

[0142] The influence weights of the closing point closing impact current and the closing steady-state circulating current on the current factor are defined as follows:

[0143]

[0144]

[0145] 4. Calculation example

[0146] by Figure 3 The hierarchy shown is Figure 2 The risk assessment of the three closing points K1, K3, and K5 is carried out, and the element weights of different layers are obtained as follows:

[0147] Table 3 Weights of elements at different layers

[0148]

[0149]

[0150] The combined weights of the two possible solutions are as follows:

[0151] Table 4 Ranking weights of factors in the scenario layer for decision-making objectives

[0152]

[0153] It can be seen that the risk of closing the loop at different points is: K3>K5>K1.

[0154] Example 2

[0155] This embodiment provides a loop-closing load reversal operation risk assessment system based on the analytic hierarchy process, including:

[0156] A hierarchical analysis structure model construction module is configured to obtain a live loop closing and load reversal plan for the distribution network, the grid topology and equipment parameters of the area where live loop closing and load reversal are required, determine the causal relationship between relevant factors affecting the risk of loop closing and load reversal operations, and construct a hierarchical analysis structure model;

[0157] The hierarchical judgment matrix calculation module is configured to compare the factors in each intermediate level with each other based on the hierarchical analysis structure model to establish multiple hierarchical judgment matrices;

[0158] A matrix characteristic root calculation module is configured to calculate the matrix characteristic root according to the hierarchical judgment matrix to obtain the weight of the importance of the factors corresponding to the hierarchical judgment matrix to the factors in the previous layer;

[0159] A consistency check module is configured to perform consistency checks on all hierarchical judgment matrices;

[0160] The risk level assessment module is configured to sort all the loop closure schemes according to the comprehensive weight of the hierarchical judgment matrix to obtain the risk levels of different loop closure schemes.

[0161] The examples and application scenarios implemented by the above modules and corresponding steps are the same, but are not limited to the contents disclosed in the above embodiment 1. It should be noted that the above modules as part of the system can be executed in a computer system such as a set of computer executable instructions.

[0162] The descriptions of the various embodiments in the above embodiments have different focuses. For parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0163] The proposed system can be implemented in other ways. For example, the system embodiment described above is merely illustrative. For example, the above module division is only a logical function division. In actual implementation, other division methods may be used. For example, multiple modules can be combined or integrated into another system, or some features can be ignored or not implemented.

[0164] Example 3

[0165] This embodiment provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the steps of the loop-closing load reversal operation risk assessment method based on the hierarchical analysis method as described in the first embodiment above are implemented.

[0166] Example 4

[0167] This embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the method for risk assessment of closed-loop load reversal operation based on the hierarchical analysis method as described in the first embodiment above are implemented.

[0168] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of hardware embodiments, software embodiments, or embodiments combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage and optical storage, etc.) containing computer-usable program code.

[0169] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0170] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0171] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0172] Those skilled in the art will appreciate that all or part of the processes in the above-described method embodiments can be implemented by instructing related hardware through a computer program. The program can be stored in a computer-readable storage medium, and when executed, the program can include the processes in the above-described method embodiments. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

[0173] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A risk assessment method for loop closing and reverse load operation based on the analytic hierarchy process is characterized by: include: Obtain the live closing and load reversal scheme for the distribution network, the grid topology and equipment parameters for the area where live closing and load reversal are required, determine the causal relationship between the relevant factors affecting the risk of closing and load reversal operations, and construct a hierarchical analysis structure model; The equipment parameters include the operating mode, load size, transformer gear and reactive power compensation input status on both sides of the loop closing point during the planned loop closing operation period, the operating parameters of the overhead lines, cables, transformers, mutual inductors, switchgear and reactive power compensation equipment on both sides of the loop closing point, as well as the load type area to which the loop closing operation location belongs and the power supply status on different dates; Based on the hierarchical analysis structure model, the factors in each middle layer are compared pairwise and multiple middle-level judgment matrices are established; Relevant factors include grid operation factors, load distribution, operation area division, and social factors. The social factors include three situations: power supply guarantee on weekdays, holidays, and important schedules. Each situation corresponds to different grid operation safety and stability and power quality requirements; Calculate the matrix characteristic root according to the intermediate level judgment matrix to obtain the weight of the importance of the factors corresponding to the intermediate level judgment matrix to the factors in the upper level; The method of computational quantitative analysis is used to modify the weight of the importance of the factors corresponding to each intermediate level judgment matrix to the factors in the previous level, including: Considering the different closing currents in different closing schemes, the weights of the closing impulse current and the closing steady-state circulating current in each intermediate layer judgment matrix on the closing current in power grid operation are modified; By using the feeder current before the loop is closed and the impact circulating current of the additional ring network during the loop closing, the expression of the full current of the loop closing impact current after the loop is closed is determined and solved to obtain the loop closing impact current; The closed-loop steady-state current after closing is determined by using the difference in effective voltage values ​​and voltage phase angle between the two sides of the open-loop connection before closing. The closing point closing impulse current and the closing steady-state circulating current are normalized to per unit using the rated current value of the transformer; Obtain the weights of the influence of the closing point closing impact current and the closing steady-state circulating current on the current factor; The full current expression of the closed-loop impulse current is: From this formula, we can get the closing point closing impact current, that is, when closing the loop The maximum value ; δ Indicates the phase angle difference of the voltage across the switch when the loop is closed; is the effective value of the steady-state circulating current, is the impedance angle of the closed-loop equivalent model; T=L / R is the attenuation time constant of the non-periodic component, , ; The closed-loop steady-state circulation is expressed as: Where U is the effective value of the voltage vector difference across the closing switch when the loop is closed, the effective value difference of the voltage across the tie switch before closing is △U, and |Z| represents the modulus of the loop impedance. Perform consistency checks on all intermediate-level judgment matrices; According to the comprehensive weight of the intermediate-level judgment matrix, all the loop closure plans are ranked to obtain the risk levels of different loop closure plans; The indicators that affect the operation of the power grid are divided into the voltage difference on both sides of the closing point, the closing current, and the phase angle difference on both sides of the closing point; the factors of the load situation are divided into general load, civil and important industrial load, medical, government power supply load and important large user load; the operating area is divided into four types of areas ABCD according to the load distribution standard. The division standard is based on the actual economic development situation of different regions and the objective differences in medium and low voltage distribution networks. The benchmark values ​​of energy efficiency evaluation indicators are selected according to the four categories of areas A, B, C and D.

2. The loop closing load reversal operation risk assessment method based on the analytic hierarchy process according to claim 1 is characterized in that: Determine the causal relationship between the relevant factors that affect the risk of loop-closing reverse load operation and construct a hierarchical analysis structure model, including: Analyze the characteristics of each grid topology and determine the factors that affect the risk of loop-closing reverse load operation; Determine the sub-factors that affect each factor and the causal relationship between them, and establish a hierarchical analysis structure model; Among them, relevant factors include grid operation factors, load distribution, operation area division and social factors. The social factors include three situations of power supply on weekdays, holidays and important schedules. Each situation corresponds to different grid operation safety, stability and power quality requirements.

3. The loop closing load reversal operation risk assessment method based on the analytic hierarchy process according to claim 1 is characterized in that: The hierarchical analysis structure model is composed of the target layer, the middle layer and the loop-closing solution layer from top to bottom. The top layer is the target layer, the bottom layer is the loop-closing solution layer, and the middle layer includes multiple criterion layers. The target layer is used to provide a risk assessment level for the loop closing operation, and the criterion layer is used to rank the various indicators that affect the loop closing operation risk and divide them according to actual conditions; the loop closing scheme layer includes a typical live loop closing and load reversal loop closing scheme for the distribution network.

4. The loop closing load reversal operation risk assessment method based on the analytic hierarchy process according to claim 1 is characterized in that: The calculation of the comprehensive weight includes: Use the maximum eigenvalue of the comparison matrix of the second layer elements The corresponding eigenvector is used as the weight vector of the second layer element ; Similarly, we get the weight vector of the third layer to each element of the second layer , then the weight vector matrix of the third layer is , therefore, the combined weight vector of the third layer for the target layer is ; By analogy, if we push it to the hth layer, the final comprehensive weight is: in, It is the weight vector matrix composed of the weight vectors of the j-1 layer for the j-1 layer. The calculated comprehensive weight is used as the quantitative basis for the risk assessment of the decision-making loop operation plan, and the larger the weight, the higher the risk.

5. The loop closing and reverse load operation risk assessment system based on the analytic hierarchy process is characterized by: include: A hierarchical analysis structure model construction module is configured to obtain a live loop closing and load reversal plan for the distribution network, the grid topology and equipment parameters of the area where live loop closing and load reversal are required, determine the causal relationship between relevant factors affecting the risk of loop closing and load reversal operations, and construct a hierarchical analysis structure model; The equipment parameters include the operation mode, load size, transformer gear and reactive compensation input on both sides of the closing point during the planned closing operation period, overhead lines, cables, transformers on both sides of the closing point, The operating parameters of transformers, transformers, switchgear, reactive compensation equipment, and the location of the closed loop operation Power supply guarantee status by load type, region and date; The hierarchical judgment matrix calculation module is configured to compare the factors in each intermediate level with each other based on the hierarchical analysis structure model to establish multiple hierarchical judgment matrices; Relevant factors include grid operation factors, load distribution, operating area division, and social factors. The social factors include three scenarios: power supply during weekdays, holidays, and important schedules. Each scenario corresponds to different grid operation safety, stability, and power quality requirements. A matrix characteristic root calculation module is configured to calculate the matrix characteristic root according to the hierarchical judgment matrix to obtain the weight of the importance of the factors corresponding to the hierarchical judgment matrix to the factors in the previous layer; The method of computational quantitative analysis is used to modify the weight of the importance of the factors corresponding to each intermediate level judgment matrix to the factors in the previous level, including: Considering the different closing currents in different closing schemes, the weights of the closing impulse current and the closing steady-state circulating current in each intermediate layer judgment matrix on the closing current in power grid operation are modified; By using the feeder current before the loop is closed and the impact circulating current of the additional ring network during the loop closing, the expression of the full current of the loop closing impact current after the loop is closed is determined and solved to obtain the loop closing impact current; The closed-loop steady-state current after closing is determined by using the difference in effective voltage values ​​and voltage phase angle between the two sides of the open-loop connection before closing. The closing point closing impulse current and the closing steady-state circulating current are normalized to per unit using the rated current value of the transformer; Obtain the weights of the influence of the closing point closing impact current and the closing steady-state circulating current on the current factor; The full current expression of the closed-loop impulse current is: From this formula, we can get the closing point closing impact current, that is, when closing the loop The maximum value ;δ represents the phase angle difference of the voltage across the switch when the loop is closed; is the effective value of the steady-state circulating current, is the impedance angle of the closed-loop equivalent model; T=L / R is the attenuation time constant of the non-periodic component, , ; The closed-loop steady-state circulation is expressed as: Where U is the effective value of the voltage vector difference across the closing switch when the loop is closed, the effective value difference of the voltage across the tie switch before closing is △U, and |Z| represents the modulus of the loop impedance. A consistency check module is configured to perform consistency checks on all hierarchical judgment matrices; The risk level assessment module is configured to sort all the loop closure solutions according to the comprehensive weight of the hierarchical judgment matrix and obtain the risk level of different loop closure solutions; The indicators that affect the operation of the power grid are divided into the voltage difference on both sides of the closing point, the closing current, and the phase angle difference on both sides of the closing point; the factors of the load situation are divided into general load, civil and important industrial load, medical, government power supply load and important large user load; the operating area is divided into four types of areas ABCD according to the load distribution standard. The division standard is based on the actual economic development situation of different regions and the objective differences in medium and low voltage distribution networks. The benchmark values ​​of energy efficiency evaluation indicators are selected according to the four categories of areas A, B, C and D.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the loop-closing load reversal operation risk assessment method based on the hierarchical analysis method as described in any one of claims 1 to 4 are implemented.

7. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps of the loop-closing load reversal operation risk assessment method based on the hierarchical analysis method are implemented as described in any one of claims 1 to 4.

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