Low-voltage transformer area flexible interconnection device planning method considering reliability improvement

Abstract

The invention discloses a low-voltage transformer area flexible interconnection device planning method considering reliability improvement, and belongs to the technical field of power distribution network planning, and the method comprises the steps: dividing a power distribution network N-1 fault set based on a virtual power flow method, solving a reliability index after flexible interconnection access by taking a user as a minimum transfer unit, and obtaining a power distribution network N-1 fault set; and planning the installation position and capacity of the flexible interconnection device in the low-voltage transformer area through a hierarchical sequence method. According to the low-voltage transformer area flexible interconnection device locating and sizing planning method, power loss type division of the transformer area is considered, the low-voltage flexible interconnection transfer process can be visually analyzed, meanwhile, the reliability of a power distribution network can be effectively improved through the proposed low-voltage transformer area flexible interconnection device locating and sizing planning method, and the method has important practical significance on flexible interconnection transformation construction of the power distribution network.

Description

Technical Field

[0001] The invention belongs to the technical field of distribution network planning, and particularly relates to a planning method for a flexible interconnection device in a low-voltage substation area considering reliability improvement. Background Art

[0002] As an important part of the power system, the distribution network directly faces end-users, and its operating state directly affects the power consumption experience of users. In recent years, the rapid development of distributed generation (such as solar energy, wind energy, etc.) has brought new opportunities and challenges to the distribution network. Although the access of distributed power sources can improve energy utilization efficiency and reduce carbon emissions, it also has complex effects on voltage control, power flow distribution, and power supply reliability of the distribution network. In addition, with the large-scale access of new loads such as electric vehicles and energy storage devices, the load characteristics and operating state of the distribution network have become more complex and changeable. However, the traditional distribution network has some inherent defects, such as relatively fixed network structure, low power supply reliability, limited access capacity of distributed power sources, etc., and it is difficult to meet the requirements of modern power systems for high reliability. The installation quantity and installation location of low-voltage flexible interconnection devices are relatively flexible, and their adjustment effects are closely related to the location and load characteristics of the connected substation areas. Therefore, reasonably planning the access scheme of low-voltage flexible interconnection devices is of great significance for improving the power supply reliability of the distribution network.

[0003] At present, the main methods for evaluating the reliability of distribution networks are divided into two categories: analytical methods and simulation methods. Analytical methods mainly obtain reliability indicators by calculating explicit expressions based on existing line reliability data, such as failure rates. The solving accuracy of analytical methods is high, but the existing reliability analytical calculation methods do not involve the access situation of flexible interconnection devices. Simulation methods mainly obtain various reliability indicators of the distribution network approximately through random simulation and a large number of repeated tests, such as the Monte Carlo simulation method, the Bayesian network time series simulation method, etc. The evaluation speed of simulation methods is relatively fast, but the accuracy of the solving results depends on the convergence accuracy. Especially for local factors that need to be considered in the distribution network, such as low-voltage substation area flexible interconnection devices, the results obtained by simulation methods have large randomness and cannot stably reflect the reliability indicators of some substation areas. Summary of the Invention

[0004] Aiming at the deficiencies of existing reliability evaluation methods, the invention proposes a planning method for a flexible interconnection device in a low-voltage substation area considering reliability improvement, which is used to solve the problem that it is difficult to accurately evaluate the role of low-voltage flexible interconnection devices in improving the reliability of the distribution network, can more reasonably evaluate the system reliability in the case of installing low-voltage substation area flexible interconnection devices, and provides a reference for the planning and construction of low-voltage substation area flexible interconnection devices.

[0005] The object of the present invention is achieved by the following technical solutions: A method for planning a flexible interconnection device in a low-voltage distribution area considering reliability improvement, including:

[0006] Generate a variable matrix representing the installation locations and port capacities of the flexible interconnection devices and the constraint conditions for the flexible interconnection device planning, and obtain the set of planning solutions for the flexible interconnection devices; among them, the constraint conditions for the flexible interconnection device planning include installation quantity constraints, installation capacity constraints, and transfer power constraints;

[0007] Solve the virtual power flow model of the distribution network to obtain the virtual power flow of each line in the distribution network for the low-voltage distribution area nodes, and calculate the power loss index of the low-voltage distribution area without connecting the flexible interconnection device;

[0008] For each planning solution of the flexible interconnection device, divide the distribution network line N-1 fault set into a repair power loss fault set, a switching power loss fault set, and a seamless fault set according to the power loss types of the area users;

[0009] For each planning solution of the flexible interconnection device, calculate the power loss index correction values of the two ends of the distribution area and the power loss index after transfer;

[0010] For each planning solution of the flexible interconnection device, calculate the number of users corresponding to each power loss type after transfer;

[0011] For each planning solution of the flexible interconnection device, calculate the reliability index of the entire distribution network under the condition of transferring the fault load with the user as the minimum unit;

[0012] Taking the minimum power loss cost as the objective function, solve the installation locations and capacities of the flexible interconnection devices in the low-voltage distribution area, and complete the method for planning the flexible interconnection devices in the low-voltage distribution area considering reliability improvement.

[0013] Furthermore, the basis for dividing the fault set is specifically:

[0014] When a single line in the distribution network has an N-1 fault, due to the influence of the distribution network topology and switch positions, different distribution areas will suffer different types of power losses; among them, repair power loss means that the distribution area resumes power supply after the fault is repaired, switching power loss means that the distribution area resumes power supply after the disconnector completes the switching, and seamless means that the distribution area is not affected by the fault;

[0015] The repair power loss fault set is:

[0016]

[0017] Wherein, represents the set of lines that cause node s to suffer repair power loss, is the virtual power flow variable of line ij for node s;

[0018] The switching power outage fault set is:

[0019] Ψ s S = { ( i , j ) | [ 1 − ( f i j , s + f j i , s ) ] ∑ i ' ∈ Ψ S ∑ j ' ∈ Ψ i ′ f i ′ j ′ , s f i ′ j ′ , i = 1 }

[0020] Wherein, represents the set of lines that cause node s to suffer from switching power outage, represents the set of nodes directly connected to the upstream substation of the feeder, represents the set of nodes directly connected to node i';

[0021] The seamless fault set is:

[0022]

[0023] Wherein, represents the set of lines that do not affect node s during a fault.

[0024] Furthermore, calculate the corrected values of the power outage indicators at both ends of the low-voltage flexible interconnection device, including:

[0025] For the case where one end of the interconnected substations restores power outage and the other end switches power outage, the power outage time of the restored substation decreases, and the corrected value of the power outage time without changing the number of power outages is:

[0026] .

[0027] Wherein, is the failure rate of line ij, and respectively represent the average repair time and switching time required for line ij to fail, represents the set of interconnected substations;

[0028] For the case where one end of the interconnected substations restores power outage and the other end is seamless, the power outage time and the number of power outages of the restored substation both decrease, and the corrected values of the power outage time and the number of power outages are respectively:

[0029]

[0030]

[0031] For the case where one end of the interconnected substations switches power outage and the other end is seamless, the power outage time and the number of power outages of the switched substation both decrease, and the corrected values of the power outage time and the number of power outages are respectively:

[0032]

[0033]

[0034] Calculate the power outage indicators after power transfer, including:

[0035]

[0036] In the formula, 、 、 and respectively represent the annual average number of restored power outages, the restored power outage time, the number of switched power outages, and the switched power outage time of the distribution area p after connecting the flexible interconnection device. 、 、 and respectively represent the annual average number of restored power outages, the restored power outage time, the number of switched power outages, and the switched power outage time of the distribution area p when the flexible interconnection device is not connected.

[0037] Furthermore, calculate the number of users corresponding to each type of power outage after power transfer, including:

[0038] When the power outage types of the two end distribution areas are restoration - switching:

[0039]

[0040] In the formula, and respectively represent the number of users in the distribution area p who bear the restored power outages and switched power outages in the case of a fault in the line ij. represents the total number of users in the distribution area p. represents the number of users in the distribution area p whose power outage type changes due to the power transfer effect of the FID interconnected between the distribution areas p and q.

[0041] When the power outage types of the two end distribution areas are restoration - seamless:

[0042]

[0043] In the formula, represents the number of users in the distribution area p who are not affected by the power outage in the case of a fault in the line ij.

[0044] When the power outage types of the two end distribution areas are switching - seamless:

[0045] .

[0046] Furthermore, calculate the reliability indexes of the distribution network, including:

[0047]

[0048]

[0049]

[0050]

[0051] In the formula: , , and respectively represent the system average power outage frequency, the system average power outage duration, the average power supply availability, and the expected value of the power supply shortage represents the total number of users in the distribution area s, and respectively represent the number of users in the distribution area p who bear the power outage during repair and the power outage during switching in the case of a fault in the line ij, represents the total load in the distribution area corresponding to the node s.

[0052] Furthermore, the installation quantity constraint is expressed as follows:

[0053]

[0054] In the formula: represents the low-voltage flexible interconnection liaison variable corresponding to the nodes i and j. If there is an interconnection device, it is 1; otherwise, it is 0 represents the maximum installation quantity;

[0055] The installation capacity constraint is expressed as follows:

[0056]

[0057] In the formula: represents the port capacity of the flexible interconnection device for the interconnection between the distribution areas p and q, represents the maximum port capacity;

[0058] The power transfer constraint is expressed as follows:

[0059]

[0060]

[0061] In the formula: represents the load power transferred from the distribution area p to the distribution area q, represents the transformer capacity of the distribution area q in the case of a fault.

[0062] Furthermore, with the minimum power outage loss cost as the objective function, the installation location and capacity of the low-voltage distribution area flexible interconnection device are solved, including:

[0063] The objective function is:

[0064]

[0065] In the formula: represents the objective function, and respectively represent the annual average loss cost of power loss and the annual average loss cost of power outage times;

[0066] Among them:

[0067]

[0068]

[0069] In the formula: represents the average loss coefficient per unit of power loss, represents the average loss coefficient per unit of power outage times.

[0070] Furthermore, it also includes:

[0071] Taking the installation cost of the flexible interconnection device as the objective function, perform secondary optimization on the obtained results, and solve to obtain the optimal installation location and capacity of the final flexible interconnection device, including:

[0072]

[0073] In the formula, represents the objective function of the second optimization, and respectively represent the annual average conversion value of the investment cost of the flexible interconnection device and the annual operation and maintenance cost of the flexible interconnection device;

[0074] Among them:

[0075]

[0076]

[0077] In the formula: represents the construction cost per unit capacity of the flexible interconnection device, d represents the discount rate, y represents the service life of the flexible interconnection device, represents the annual operation and maintenance cost per unit capacity of the flexible interconnection device.

[0078] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, it implements the above-mentioned method for planning a flexible interconnection device in a low-voltage power distribution area considering reliability improvement.

[0079] The present invention also provides a storage medium containing computer-executable instructions. When the computer-executable instructions are executed by a computer processor, they implement the above-mentioned method for planning a flexible interconnection device in a low-voltage power distribution area considering reliability improvement.

[0080] Compared with the prior art, the present invention has at least the following beneficial effects:

[0081] First, a method for classifying power outage types in low-voltage flexible interconnected substations based on virtual power flow is proposed, filling the gap in the N-1 fault analysis method for distribution networks in the case of low-voltage flexible interconnection device access; second, taking users as the minimum transfer unit, for the first time, reliability indicators and explicit calculation methods for distribution networks in the case of low-voltage flexible interconnection access are proposed, making up for the deficiency that the traditional Monte Carlo simulation method depends on convergence accuracy and cannot specifically analyze the transfer process of substations; finally, a planning model for the access scheme of low-voltage flexible interconnection devices is established with reliability cost and flexible interconnection device cost as the objective function, effectively making up for the deficiencies of existing low-voltage flexible interconnection device planning indicators and limited planning methods. This method can more comprehensively evaluate the impact of low-voltage flexible interconnection devices on the improvement of distribution network reliability, and has important practical significance for the flexible interconnection transformation and construction of distribution networks.

[0082] Furthermore, according to the virtual power flow calculation results, a method for dividing the N-1 fault set for the substation area is given, and the fault impact of the line on the substation area is divided into three categories: repair power outage, switching power outage, and seamless, which is convenient for accurately calculating the power outage indicators of distribution network substations in the case of specific line N-1 faults.

[0083] Furthermore, based on the divided N-1 fault set, the power outage indicators of users in each substation area in the case of flexible interconnection device access are calculated, which is convenient for evaluating the load transfer ability of flexible interconnection devices under specific faults.

[0084] Furthermore, based on the reliability cost and the installation cost of flexible interconnection devices, the installation location and capacity of low-voltage substation area flexible interconnection devices are planned. Under the premise of optimal distribution network reliability, the most economical installation location and capacity can be obtained, helping technicians to form a reasonable installation plan for flexible interconnection devices.

[0085] In summary, the present invention considers the load transfer at the user level between different power outage type substations under faults, can accurately measure the fault transfer effect of low-voltage flexible interconnection devices, and at the same time, the proposed method for site selection and capacity determination of low-voltage substation area flexible interconnection devices effectively improves the accuracy of low-voltage substation area flexible interconnection planning, and has good application prospects. Description of the Drawings

[0086] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0087] Figure 1 It is a flowchart of a method for planning low-voltage substation area flexible interconnection devices considering reliability improvement provided by an embodiment of the present invention;

[0088] Figure 2 This is the distribution network structure diagram constructed based on the IEEE-RBTS-BUS6-F4 example in the embodiment of the present invention;

[0089] Figure 3 This is the comparison chart of the average annual power outage times of each substation node before and after planning in the embodiment of the present invention;

[0090] Figure 4 This is the comparison chart of the average annual power outage time of each substation node before and after planning in the embodiment of the present invention. Detailed implementation manners

[0091] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0092] In the description of the present invention, it should be understood that the terms "including" and "comprising" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0093] It should be understood that although the terms first, second, third, etc. may be used in the embodiments of the present invention to describe preset ranges, etc., these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0094] It should also be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0095] The present invention divides the line N-1 fault set according to the types of power outages in the substation area. By analyzing the transfer mode of the flexible interconnection device in the low-voltage substation area, a planning method for the flexible interconnection device in the low-voltage substation area considering reliability improvement is proposed, which helps to evaluate the reliability benefits of the flexible interconnection transformation of the distribution network and formulate the optimal installation plan for the flexible interconnection device. See Figure 1 This method includes the following steps:

[0096] S1. Generate a variable matrix representing the installation locations and port capacities of flexible interconnection devices and the constraint conditions for the flexible interconnection device planning, and obtain a set of possible flexible interconnection device planning schemes; among them, the constraint conditions for the flexible interconnection device planning include installation quantity constraints, installation capacity constraints, and power transfer constraints;

[0097] The installation quantity constraint is:

[0098] (1)

[0099] In the formula: represents the low-voltage flexible interconnection liaison variable corresponding to nodes i and j in the corresponding distribution areas. If there is an interconnection device, it is 1; otherwise, it is 0; n is the number of nodes. represents the maximum installation quantity.

[0100] The installation capacity constraint:

[0101] (2)

[0102] In the formula: represents the port capacity of the flexible interconnection device for the interconnection between distribution areas p and q, represents the maximum port capacity.

[0103] The power transfer constraint is:

[0104] (3)

[0105] (4)

[0106] In the formula: represents the load power transferred from distribution area p to distribution area q, represents the number of users whose power outage type changes due to the power transfer effect of the FID for the interconnection between distribution areas p and q, represents the total number of users in distribution area s, represents the total load of distribution area p, represents the port capacity of the flexible interconnection device for the interconnection between distribution areas p and q, represents the transformer capacity of distribution area q under fault conditions, represents the set of distribution areas for flexible interconnection.

[0107] S2. Solve the virtual power flow model of the distribution network to obtain the virtual power flow of each line in the distribution network for the low-voltage distribution area nodes, and calculate the power outage index of the low-voltage distribution area without flexible interconnection devices;

[0108] Solving the virtual power flow means solving the following optimization problem:

[0109] (5)

[0110] In the formula, is the virtual power flow variable of line ij with respect to node s, is the virtual power flow variable of line ji with respect to node s, represents the set of lines.

[0111] The constraint conditions are as follows:

[0112] (6)

[0113] (7)

[0114] (8)

[0115] (9)

[0116] In the formula, represents the set of nodes directly connected to node i; represents the set of nodes directly connected to node j; represents the virtual power flow variable injected by the substation into node i with respect to node s; represents the virtual load demand of node i with respect to node s; represents the set of nodes directly connected to the upstream substation of the feeder, represents the set of nodes.

[0117] In the distribution network, calculating the power outage index of the low-voltage area without connecting flexible interconnection devices includes:

[0118] The number of power outages for restoration of the area is obtained from the following formula:

[0119] (10)

[0120] In the formula, represents the annual average number of power outages for restoration of node s, is the failure rate of line ij.

[0121] The number of power outages for switching of the area is:

[0122] (11)

[0123] In the formula, represents the annual average number of power outages for switching of node s; represents the annual average number of operations of the upstream circuit breaker of node s, represents the annual average number of power outages for restoration of node s. Among them:

[0124] (12)

[0125] In the formula, represents the average annual operation times of the circuit breaker upstream of line ij.

[0126] N i j B = ∑ s ∈ Ψ N [ ( ∑ r ∈ Ψ s f r s , s λ r s ) f i j , s ] ; ∀ i ∈ Ψ S , ∀ j ∈ Ψ i (13)

[0127] In the formula, represents the set of nodes directly connected to the upstream substation of the feeder, represents the set of nodes directly connected to node i, represents the set of nodes directly connected to node s, is the virtual power flow variable of line rs for node s, is the failure rate of line ij.

[0128] The power outage restoration time of substation area s is:

[0129] (14)

[0130] In the formula, represents the average repair time required for line ij to fail;

[0131] The power outage switching time of substation area s is:

[0132] (15)

[0133] In the formula, represents the average annual total switching time of the disconnecting switch of the feeder where substation area s is located, represents the average annual total switching time of the disconnecting switch of the feeder where substation area s is located when it bears the power outage restoration.

[0134] Among them:

[0135] (16)

[0136] In the formula, represents the average annual total switching time of the disconnecting switch of the feeder where line ij is located.

[0137] D i j B , S = ∑ s ∈ Ψ N [ ( ∑ r ∈ Ψ s f r s , s λ r s t r s S ) f i j , s ] ; ∀ i ∈ Ψ S , ∀ j ∈ Ψ i (17)

[0138] (18)

[0139] In the formula, represents the average switching time required for line rs to fail.

[0140] S3. For the planning scheme of each flexible interconnection device, according to the virtual power flow obtained in step S2, divide the distribution network line N-1 fault set into a restoration power outage fault set, a switching power outage fault set, and a seamless fault set according to the power outage types of users in the substation area;

[0141] When a single line in the distribution network has an N-1 fault, due to the influence of the distribution network topology and switch positions, different substations will experience different types of power outages. Among them, restoration power outage means that the substation area resumes power supply after the fault is repaired, switching power outage means that the substation area resumes power supply after the disconnector completes the switching, and seamless means that the substation area is not affected by the fault.

[0142] The restoration power outage fault set is:

[0143] (19)

[0144] Where, represents the set of lines that cause node s to experience restoration power outage, is the virtual power flow variable of line ij for node s.

[0145] The switching power outage fault set is:

[0146] Ψ s S = { ( i , j ) | [ 1 − ( f i j , s + f j i , s ) ] ∑ i ' ∈ Ψ S ∑ j ' ∈ Ψ i ′ f i ′ j ′ , s f i ′ j ′ , i = 1 } (20)

[0147] Where, represents the set of lines that cause node s to experience restoration power outage, represents the set of nodes directly connected to the upstream substation of the feeder, represents the set of nodes directly connected to node i'.

[0148] The seamless fault set is:

[0149] (21)

[0150] Where, represents the set of lines that do not affect node s during the fault.

[0151] S4. For the planning scheme of each flexible interconnection device, calculate the corrected power outage index of the two end substations and the power outage index after power transfer;

[0152] For the case where one end of the interconnected substation experiences restoration power outage and the other end experiences switching power outage, the power outage time of the restoration power outage substation area is reduced, and the number of power outages remains unchanged. The corrected value of the power outage time is:

[0153] (22)

[0154] Where, is the failure rate of line ij, and respectively represent the average repair time and switching time required for a fault to occur in line ij; represents the change in the power outage time due to the power transfer effect when the repair power outage is borne by substation area p and the switching power outage is borne by the interconnected substation area; represents the set of substation areas with flexible interconnection, represents the set of lines that cause the repair power outage of substation area p, represents the set of lines that cause the switching power outage of substation area q.

[0155] For the case where one end of the interconnected substation area has a repair power outage and the other end is seamless, both the power outage time and the number of power outages of the substation area with the repair power outage are reduced. The correction values of the power outage time and the number of power outages are respectively:

[0156] (23)

[0157] (24)

[0158] represents the change in the power outage time due to the power transfer effect when the repair power outage is borne by substation area p and the interconnected substation area is not affected by the fault; represents the change in the number of power outages due to the power transfer effect when the repair power outage is borne by substation area p and the interconnected substation area is not affected by the fault; represents the set of lines that do not cause a power outage in substation area q under fault conditions.

[0159] For the case where one end of the interconnected substation area has a switching power outage and the other end is seamless, both the power outage time and the number of power outages of the substation area with the switching power outage are reduced. The correction values of the power outage time and the number of power outages are respectively:

[0160] (25)

[0161] (26)

[0162] and respectively represent the change in the power outage time and the number of power outages due to the power transfer effect when the switching power outage is borne by substation area p and the interconnected substation area is not affected by the fault;

[0163] The power outage indicators after power transfer are as follows:

[0164] (27)

[0165] In the formula, 、 、 and respectively represent the annual average number of repair power outages, repair power outage time, switching power outage number, and switching power outage time of substation area p after connecting the flexible interconnection device, 、 , and respectively represent the annual average number of power restoration outages, power restoration outage time, number of switching outages, and switching outage time of the distribution substation p before connecting the flexible interconnection device.

[0166] S5. For the planning scheme of each flexible interconnection device, calculate the number of users corresponding to each type of power outage after power transfer.

[0167] When the power outage types at both ends of the distribution substation are restoration - switching:

[0168] (28)

[0169] In the formula, and respectively represent the number of users in the distribution substation p who suffer from restoration outages and switching outages under the condition of line ij failure, represents the total number of users in the distribution substation p, represents the number of users in the distribution substation p whose power outage type changes due to the power transfer effect of the FID interconnected between the distribution substations p and q.

[0170] When the power outage types at both ends of the distribution substation are restoration - seamless:

[0171] (29)

[0172] In the formula, represents the number of users in the distribution substation p who are not affected by the power outage under the condition of line ij failure;

[0173] When the power outage types at both ends of the distribution substation are switching - seamless:

[0174] (30)

[0175] S6. For the planning scheme of each flexible interconnection device, calculate the reliability index of the entire distribution network under the condition of transferring the faulty load with the user as the smallest unit.

[0176] The reliability indices of each distribution network are as follows:

[0177] (31)

[0178] (32)

[0179] (33)

[0180] (34)

[0181] In the formula: , , and They represent the system average power outage frequency, the system average power outage duration, the average power supply availability, and the expected value of the unsupplied electricity quantity respectively. represents the total number of users in the distribution area s, and represent the number of users suffering from repair power outages and switching power outages in the distribution area p under the condition of line ij failure respectively, represents the total load in the distribution area corresponding to the node s.

[0182] S7. Based on the set of possible flexible interconnection device planning schemes, with the minimum cost of power outage losses as the objective function, solve the installation location and capacity of the flexible interconnection devices in the low-voltage distribution area, and complete the planning method of flexible interconnection devices in the low-voltage distribution area considering reliability improvement.

[0183] With the minimum cost of power outage losses as the objective function, solve the optimal installation location and capacity of the flexible interconnection devices. The objective function is:

[0184] (35)

[0185] In the formula: represents the objective function, and represent the annual power outage loss cost and the annual power outage frequency loss cost respectively.

[0186] Among them:

[0187] (36)

[0188] (37)

[0189] In the formula: represents the average loss coefficient per unit of power outage quantity, represents the average loss coefficient per unit of power outage frequency.

[0190] In a more preferred embodiment, it further includes taking the minimum installation cost of the flexible interconnection devices as the objective function, and using the hierarchical sequence method to perform secondary optimization on the results obtained in the previous step to obtain the final installation location and capacity configuration scheme. The specific steps are as follows:

[0191] Taking the minimum installation cost of the flexible interconnection devices as the objective function, solve the optimal installation location and capacity of the flexible interconnection devices.

[0192] The objective function of the secondary optimization is:

[0193] (38)

[0194] In the formula, represents the objective function of the second optimization, and respectively represent the average annual conversion value of the investment cost of the flexible interconnection device and the annual operation and maintenance cost of the flexible interconnection device.

[0195] Where:

[0196] (39)

[0197] (40)

[0198] In the formula: represents the construction cost of the flexible interconnection device per unit capacity, d represents the discount rate, y represents the service life of the flexible interconnection device, represents the annual operation and maintenance cost of the flexible interconnection device per unit capacity.

[0199] Example 1:

[0200] As Figure 2 shown, the planning method in the present invention is illustrated by using a distribution network constructed based on the IEEE-RBTS-BUS6-F4 example.

[0201] Set the maximum installation quantity of the flexible interconnection device to 6, and the maximum installation capacity to 0.6 MV•A. After two optimization solutions, the lowest reliability cost is 17,608 yuan, and the lowest installation cost of the flexible interconnection device is 72,365 yuan. Before and after planning, the specific costs are shown in Table 1:

[0202] Table 1 Costs before and after planning

[0203] Before and after planning, the reliability indexes are shown in Table 2:

[0204] Table 2 Reliability indexes before and after planning

[0205] The optimal access location and capacity of the FID are shown in Table 3:

[0206] Table 3 FID installation scheme

[0207] Before and after planning, the average annual power outage times and power outage durations of each substation node are respectively as Figure 3 and Figure 4 shown.

[0208] To sum up, the present invention considers the user-level load transfer between different power outage type substations under faults, and proposes a reliability-based siting and sizing planning method for flexible interconnection devices in low-voltage substations, which can help evaluate the effect of flexible interconnection transformation of the distribution network on reliability improvement and formulate the optimal installation scheme of flexible interconnection devices.

[0209] Corresponding to the embodiment of the above-mentioned method for flexible interconnection planning of low-voltage distribution areas considering the power supply capacity of the distribution network, the present invention also provides an electronic device, including one or more processors for implementing the method for flexible interconnection planning of low-voltage distribution areas considering the power supply capacity of the distribution network in the above embodiment.

[0210] The device embodiment can be implemented by software, or by hardware or a combination of software and hardware. Taking software implementation as an example, as a logically meaningful device, it is formed by the processor of any device with data processing capabilities reading the corresponding computer program instructions in the non-volatile memory into the memory for operation. In terms of hardware, it mainly includes a processor, a memory, a network interface, and a non-volatile memory. In addition, any device with data processing capabilities where the device in the embodiment is located usually includes other hardware according to the actual functions of the device with data processing capabilities, which will not be elaborated here.

[0211] For the implementation processes of the functions and roles of each unit in the above device, please refer to the implementation processes of the corresponding steps in the above method for details, which will not be elaborated here.

[0212] For the device embodiment, since it basically corresponds to the method embodiment, the relevant parts can refer to the partial description of the method embodiment. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of the present invention. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0213] The embodiment of the present invention also provides a computer-readable storage medium, on which a program is stored. When the program is executed by a processor, it implements the method for flexible interconnection planning of low-voltage distribution areas considering the power supply capacity of the distribution network in the above embodiment.

[0214] The computer-readable storage medium may be an internal storage unit of any device with data processing capabilities described in any of the foregoing embodiments, such as a hard disk or a memory. The computer-readable storage medium may also be any device with data processing capabilities, such as a plug-in hard disk, a Smart Media Card (SMC), an SD card, a Flash Card, etc. equipped on the device. Further, the computer-readable storage medium may also include both an internal storage unit of any device with data processing capabilities and an external storage device. The computer-readable storage medium is used to store the computer program and other programs and data required by any device with data processing capabilities, and may also be used to temporarily store the data that has been output or will be output.

[0215] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A planning method for a flexible interconnection device in a low-voltage power distribution area considering reliability improvement, characterized in that, Including: Generate a variable matrix representing the installation location and port capacity of the flexible interconnection device and the constraint conditions for the flexible interconnection device planning, and obtain the set of flexible interconnection device planning solutions; among them, the constraint conditions for the flexible interconnection device planning include installation quantity constraint, installation capacity constraint, and transfer power constraint; Solve the virtual power flow model of the distribution network to obtain the virtual power flow of each line in the distribution network for the low-voltage substation nodes, and calculate the power loss index of the low-voltage substation area without connecting the flexible interconnection device; For each flexible interconnection device planning solution, divide the N-1 fault set of the distribution network lines into a repair power loss fault set, a switching power loss fault set, and a seamless fault set according to the power loss type of the substation area users; For each flexible interconnection device planning solution, calculate the power loss index correction value of the two ends of the substation area and the power loss index after transfer; For each flexible interconnection device planning solution, calculate the number of users corresponding to each power loss type after transfer; For each flexible interconnection device planning solution, calculate the reliability index of the entire distribution network in the case of transferring the fault load with the user as the smallest unit; Taking the minimum power loss cost as the objective function, solve the installation location and capacity of the flexible interconnection device in the low-voltage substation area, and complete the planning method of the flexible interconnection device in the low-voltage substation area considering the improvement of reliability; 2. The method according to claim 1, wherein The basis for the division of the fault set is specifically: When a single line in the distribution network has an N-1 fault, different substations will suffer different types of power loss due to the influence of the distribution network topology and switch positions; among them, repair power loss means that the substation area resumes power supply after the fault is repaired, switching power loss means that the substation area resumes power supply after the disconnector is switched, and seamless means that the substation area is not affected by the fault; The repair power loss fault set is: In the formula, represents the set of lines for which node s bears the restoration of power outage, is the virtual power flow variable of line ij with respect to node s; The switching power loss fault set is: wherein, represents the set of lines that cause node s to experience a switching power outage, represents the set of nodes directly connected to the upstream substation of the feeder, represents the set of nodes directly connected to node i'; The seamless fault set is: In the formula, represents the set of lines that do not affect node s during a fault.

3. The method according to claim 1, wherein Calculate the power loss index correction value at both ends of the low-voltage flexible interconnection device, including: For the case where one end of the interconnected substation area has repair power loss and the other end has switching power loss, the power loss time of the repair power loss substation area is reduced, and the correction value of the power loss time without changing the power loss times is: . Wherein, is the failure rate of line ij, and respectively represent the average repair time and switching time required for line ij to fail, represents the set of flexible interconnected distribution areas; For the case where one end of the interconnected substation area has repair power loss and the other end is seamless, both the power loss time and the number of times of the repair power loss substation area are reduced, and the correction values of the power loss time and the number of times are respectively: For the case where one end of the interconnected substation area has switching power loss and the other end is seamless, both the power loss time and the number of times of the switching power loss substation area are reduced, and the correction values of the power loss time and the number of times are respectively: Calculate the power loss index after transfer, including: Wherein, , , and respectively represent the annual average number of power restoration outages, power restoration outage time, number of switching outages, and switching outage time of the distribution substation p after connecting the flexible interconnection device, , , and respectively represent the annual average number of power restoration outages, power restoration outage time, number of switching outages, and switching outage time of the distribution substation p before connecting the flexible interconnection device.

4. The method according to claim 1, wherein Calculate the number of users corresponding to each power loss type after transfer, including: When the power loss types at both ends of the substation area are repair-switching: In the formula, and respectively represent the number of users in substation area p who bear the power loss during repair and switching under the fault condition of line ij. represents the total number of users in substation area p. represents the number of users in substation area p whose power loss type changes due to the FID power transfer effect of the interconnection between substation areas p and q. When the power loss types at both ends of the substation area are repair-seamless: Wherein, represents the number of users not affected by power outage when the line ij fails in the transformer area p; When the power loss types at both ends of the substation area are switching-seamless: 。 5. The method according to claim 1, wherein Calculate the reliability index of the distribution network, including: In the formula: , , and represent the system average power outage frequency, the system average power outage duration, the average power supply availability, and the expected value of the power supply shortage respectively. represents the total number of users in substation area s. and represent the number of users in substation area p who suffer from power outage during repair and power outage during switching respectively under the fault of line ij. represents the total load in the substation area corresponding to node s.

6. The method according to claim 1, wherein The installation quantity constraint is expressed as follows: Where: represents the low-voltage flexible interconnection variable corresponding to the substations of nodes i and j, with the interconnection device being 1 and otherwise 0 represents the maximum installation quantity; The installation capacity constraint is expressed as follows: Wherein: represents the port capacity of the flexible interconnection device for the interconnection between substations p and q, represents the maximum port capacity The transfer power constraint is expressed as follows: Where: represents the load power transferred from distribution transformer area p to distribution transformer area q, represents the distribution transformer capacity of distribution transformer area q under fault conditions.

7. The method according to claim 1, characterized in that Taking the minimum power loss cost as the objective function, solve the installation location and capacity of the flexible interconnection device in the low-voltage substation area, including: The objective function is: In the formula: represents the objective function, and represent the annual average power loss cost and the annual average power outage times loss cost respectively; Wherein: In the formula: represents the average loss coefficient of unit power loss, represents the average loss coefficient of unit power loss times.

8. The method according to claim 1, wherein Also including: Taking the installation cost of the flexible interconnection device as the objective function, perform secondary optimization on the obtained results, and solve to obtain the optimal installation location and capacity of the final flexible interconnection device; Including: In the formula, represents the objective function of the second optimization, and respectively represent the average annual converted value of the investment cost of the flexible interconnection device and the annual operation and maintenance cost of the flexible interconnection device; Wherein: In the formula: represents the construction cost of the flexible interconnection device per unit capacity, d represents the discount rate, and y represents the service life of the flexible interconnection device, represents the annual operation and maintenance cost of the flexible interconnection device per unit capacity.

9. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements a planning method for a flexible interconnection device in a low-voltage substation area considering reliability improvement as described in any one of claims 1-8.

10. A storage medium containing computer-executable instructions, characterized in that, When the computer-executable instructions are executed by a computer processor, they implement a planning method for a flexible interconnection device in a low-voltage substation area considering reliability improvement as described in any one of claims 1-8.

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