A planning method for low-voltage area flexible interconnection devices considering reliability improvement

Abstract

The present invention discloses a method for planning low-voltage area flexible interconnection devices that takes reliability improvement into consideration, belonging to the technical field of distribution network planning. The method comprises dividing the N-1 fault set of the distribution network based on the virtual power flow method, solving the reliability index after flexible interconnection access with the user as the minimum transfer unit, and planning the installation location and capacity of the low-voltage area flexible interconnection device through the hierarchical sequence method. The present invention takes into account the classification of power outage types in the area and can intuitively analyze the low-voltage flexible interconnection transfer process. At the same time, the proposed method for site selection and capacity planning of low-voltage area flexible interconnection devices can effectively improve the reliability of the distribution network, which has important practical significance for the transformation and construction of the flexible interconnection of the distribution network.

Description

Technical Field

[0001] The present invention belongs to the technical field of distribution network planning, and in particular relates to a method for planning low-voltage area flexible interconnection devices taking reliability improvement into consideration. Background Art

[0002] As a crucial component of the power system, the distribution network directly serves end users, and its operational status directly impacts their electricity experience. In recent years, the rapid development of distributed generation (such as solar and wind power) has brought new opportunities and challenges to the distribution network. While the integration of distributed generation (DGs) can improve energy efficiency and reduce carbon emissions, it also has complex impacts on voltage control, power flow distribution, and power supply reliability within the distribution network. Furthermore, with the influx of new loads such as electric vehicles and energy storage devices, the load characteristics and operational status of the distribution network have become increasingly complex and dynamic. However, traditional distribution networks have inherent flaws, such as a relatively fixed network structure, low power supply reliability, and limited DG access capabilities, making them unable to meet the high reliability requirements of modern power systems. Low-voltage flexible interconnection devices (LVFIDs) offer flexibility in terms of number and location, and their regulatory role is closely related to the location and load characteristics of the connected substations. Therefore, rationally planning the LVFID access plan is crucial for improving distribution network reliability.

[0003] At present, the main methods for distribution network reliability assessment are divided into two categories: analytical methods and simulation methods. The analytical method mainly obtains reliability indicators by calculating explicit expressions based on existing line reliability data, such as failure rates. The analytical method has high solution accuracy, but the existing reliability analytical calculation methods do not involve the access of flexible interconnection devices. The simulation method mainly uses random simulation to conduct a large number of repeated experiments to approximate various reliability indicators of the distribution network, such as Monte Carlo simulation method and Bayesian network time series simulation method. The simulation method has a faster evaluation speed, but the accuracy of the solution depends on the convergence accuracy. In particular, when there are local factors that need to be considered in the distribution network, such as flexible interconnection devices in low-voltage substations, the results of the simulation method are more random and cannot stably reflect the reliability indicators of some substations. Summary of the Invention

[0004] The problem solved by the present invention is to address the shortcomings of existing reliability assessment methods and propose a low-voltage substation flexible interconnection device planning method that takes reliability improvement into consideration, so as to solve the current problem that it is difficult to accurately evaluate the role of low-voltage flexible interconnection devices in improving the reliability of distribution networks. It can more reasonably evaluate system reliability when installing low-voltage substation flexible interconnection devices and provide a reference for the planning and construction of low-voltage substation flexible interconnection devices.

[0005] The objective of the present invention is achieved through the following technical solutions: A method for planning a low-voltage area flexible interconnection device considering reliability improvement, comprising:

[0006] Generate a variable matrix representing the installation locations and port capacities of the flexible interconnection devices and constraints for flexible interconnection device planning, and obtain a set of planning schemes for the flexible interconnection devices; wherein the constraints for 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 substation node, and calculate the power outage index of the low-voltage substation when the flexible interconnection device is not connected;

[0008] For each flexible interconnection device planning scheme, the distribution network line N-1 fault set is divided into a repair power failure set, a switching power failure set, and a seamless fault set according to the power failure type of the users in the substation area;

[0009] For each flexible interconnection device planning scheme, calculate the power loss index correction value of the two end substations and the power loss index after power transfer;

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

[0011] For each flexible interconnection device planning scheme, calculate the reliability index of the entire distribution network, assuming fault load transfer is performed with the user as the smallest unit;

[0012] Taking the minimization of power loss cost as the objective function, the installation location and capacity of the low-voltage area flexible interconnection device are solved, and a planning method for low-voltage area flexible interconnection devices considering reliability improvement is completed.

[0013] Furthermore, the fault sets are divided based on:

[0014] When a single line in the distribution network experiences an N-1 fault, different substations will experience different types of power outages due to the influence of the distribution network topology and switch locations. A repair power outage refers to a substation recovering power after the fault is repaired, a switching power outage refers to a substation recovering power after the disconnector switches, and a seamless power outage refers to a substation not affected by the fault.

[0015] The power failure repair set is:

[0016]

[0017] Where, represents the set of lines that allow node s to withstand the power outage, is the virtual power flow variable of line ij for node s;

[0018] The switching power failure fault set is:

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

[0020] Where, represents the set of lines that make node s 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 failure sets are:

[0022]

[0023] Where, Represents the set of lines that do not affect node s when a failure occurs.

[0024] Furthermore, the power outage index correction values of the substations at both ends of the low-voltage flexible interconnection device are calculated, including:

[0025] For the case where one end of the interconnected substation loses power after repair and the other end loses power after switching, the power outage time of the substation that loses power after repair is reduced. The correction value of the power outage time without changing the number of power outages is:

[0026] .

[0027] Where, is the failure rate of line ij, and They represent the average repair time and switching time required for line ij to fail, Represents a collection of flexible interconnected areas;

[0028] For the case where one end of the interconnected substation is repaired and the other end is seamless, the power outage time and frequency of the repaired substation are reduced by the correction values of the power outage time and frequency respectively:

[0029]

[0030]

[0031] For the case where one end of the interconnected substation loses power while the other end is seamless, the power outage time and frequency of the substation where the switching fails are reduced by the correction values of the power outage time and frequency respectively:

[0032]

[0033]

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

[0035]

[0036] Where, 、 、 and They represent the annual average number of power outages repaired, the time it takes to repair power outages, the number of power outages switched, and the time it takes to switch power outages in area p after it is connected to the flexible interconnection device. 、 、 and They represent the annual average number of repair power outages, repair power outage time, switching power outages, and switching power outage time of the substation p when it is not connected to the flexible interconnection device.

[0037] Furthermore, the number of users corresponding to each type of power outage after the power supply is transferred is calculated, including:

[0038] When the power outage type at both ends is repair-switching:

[0039]

[0040] Where, and They represent the number of users in area p who suffer power outage due to repair and switching when line ij fails, represents the total number of users in area p, represents the number of users in area p whose power outage type changes due to the FID transfer between areas p and q;

[0041] When the power outage type at both ends is repair-seamless:

[0042]

[0043] Where, represents the number of users in area p who are not affected by power outage when line ij fails;

[0044] When the power failure type at both ends is switching-seamless:

[0045] .

[0046] Furthermore, the distribution network reliability index is calculated, including:

[0047]

[0048]

[0049]

[0050]

[0051] Where: 、 、 and Represents the average power outage frequency, average power outage duration, average power supply availability and expected power shortage value respectively represents the total number of users in station area s, and They represent the number of users in area p who suffer power outage due to repair and switching when line ij fails, Represents the total load in the area corresponding to node s.

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

[0053]

[0054] Where: Represents the low-voltage flexible interconnection variable of the substations corresponding to nodes i and j. It is 1 if there is an interconnection device, and 0 otherwise. Represents the maximum number of installations;

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

[0056]

[0057] Where: represents the port capacity of the flexible interconnection device between the stations p and q, Represents the maximum port capacity;

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

[0059]

[0060]

[0061] Where: represents the load power in area p transferred to area q, Represents the distribution transformer capacity of substation q under fault conditions.

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

[0063] The objective function is:

[0064]

[0065] Where: represents the objective function, and They represent the annual average loss cost of electricity and the annual average loss cost of the number of power outages respectively;

[0066] in:

[0067]

[0068]

[0069] Where: Represents the average loss coefficient per unit loss of electricity, Represents the average loss coefficient per unit power outage number.

[0070] Furthermore, it also includes:

[0071] Taking the installation cost of the flexible interconnection device as the objective function, the obtained results are optimized twice to obtain the optimal installation location and capacity of the flexible interconnection device, including:

[0072]

[0073] Where, represents the objective function of the second optimization, and They 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 respectively;

[0074] in:

[0075]

[0076]

[0077] Where: 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.

[0078] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and runnable on the processor. When the processor executes the computer program, it implements the above-mentioned method for planning a low-voltage substation flexible interconnection device that takes into account reliability improvement.

[0079] The present invention also provides a storage medium containing computer-executable instructions, which, when executed by a computer processor, can implement the above-mentioned method for planning low-voltage area flexible interconnection devices that takes into account 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 outages in low-voltage flexible interconnected substations based on virtual power flow is proposed, addressing the lack of N-1 fault analysis methods for distribution networks with low-voltage flexible interconnected devices. Second, with users as the minimum transfer unit, a distribution network reliability index and its explicit calculation method are proposed for the first time under low-voltage flexible interconnected conditions. This addresses the limitation of traditional Monte Carlo simulation methods, which rely on convergence accuracy and cannot specifically analyze the power transfer process within a substation. Finally, a planning model for low-voltage flexible interconnected device access schemes is established, using reliability cost and flexible interconnected device cost as objective functions. This effectively addresses the inadequate planning indicators and limited planning methods for existing low-voltage flexible interconnected device planning. This method can more comprehensively evaluate the impact of low-voltage flexible interconnected devices on improving distribution network reliability and has important practical significance for the transformation and construction of flexible interconnected distribution networks.

[0082] Furthermore, based on the results of virtual power flow calculation, a method for dividing the N-1 fault set for the substation is given, and the impact of line faults on the substation is divided into three categories: repair power loss, switching power loss and seamless power loss, which facilitates the accurate calculation of the power loss index of the distribution network substation under the condition of a specific line N-1 fault.

[0083] Furthermore, based on the divided N-1 fault set, the power loss index of users in each substation is calculated when the flexible interconnection device is connected, which facilitates the evaluation of the flexible interconnection device's ability to transfer power to the load under specific faults.

[0084] Furthermore, based on the reliability cost and the installation cost of the flexible interconnection device, the installation location and capacity of the low-voltage substation flexible interconnection device 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 flexible interconnection device installation plan.

[0085] To sum up, the present invention takes into account the user-level load transfer between substations with different power outage types under fault conditions, and can accurately measure the fault transfer function of low-voltage flexible interconnection devices. At the same time, the proposed method for site selection and sizing planning of low-voltage substation flexible interconnection devices effectively improves the accuracy of low-voltage substation flexible interconnection planning and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0087] Figure 1 A flowchart of a method for planning low-voltage area flexible interconnection devices that takes reliability improvement into consideration, provided by an embodiment of the present invention;

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

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

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

[0091] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0092] In the description of the present invention, it is to be understood that the terms “include” and “comprise” 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 collections thereof.

[0093] It should be understood that although the terms "first," "second," and "third" may be used to describe preset ranges in embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are merely used to distinguish one preset range from another. For example, without departing from the scope of 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 present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

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

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

[0097] The installation quantity constraint is:

[0098] (1)

[0099] Where: Represents the low-voltage flexible interconnection connection variable of the substations corresponding to nodes i and j. It is 1 if there is an interconnection device, otherwise it is 0; n is the number of nodes. Represents the maximum number of installations.

[0100] Installation capacity constraints:

[0101] (2)

[0102] Where: represents the port capacity of the flexible interconnection device between the stations p and q, Indicates the maximum port capacity.

[0103] The transfer power constraint is:

[0104] (3)

[0105] (4)

[0106] Where: represents the load power in area p transferred to area q, represents the number of users in area p whose power outage type changes due to the FID transfer between areas p and q. represents the total number of users in station area s, represents the total load of the area p, represents the port capacity of the flexible interconnection device between the stations p and q, represents the distribution transformer capacity of the substation q under fault conditions, Represents a collection of flexible interconnected areas.

[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 substation node, and calculate the power outage index of the low-voltage substation when the flexible interconnection device is not connected;

[0108] Solving the virtual power flow is to solve the following optimization problem:

[0109] (5)

[0110] Where, is the virtual power flow variable of line ij for node s, is the virtual power flow variable of line ji for node s, Represents a collection of lines.

[0111] The constraints are as follows:

[0112] (6)

[0113] (7)

[0114] (8)

[0115] (9)

[0116] Where, 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 into node i by the substation for node s; represents the virtual load demand of node i for node s; represents the set of nodes directly connected to the upstream substation of the feeder, Represents a collection of nodes.

[0117] In the distribution network, the power outage indicators of the low-voltage area without flexible interconnection devices are calculated, including:

[0118] Number of power outages repaired in the substation It is obtained by the following formula:

[0119] (10)

[0120] Where, represents the annual average number of power outage repairs for node s, is the failure rate of line ij.

[0121] Number of power failures during area switching for:

[0122] (11)

[0123] Where, represents the annual average number of switching power outages at node s; represents the average annual number of operations of the upstream circuit breaker of node s, Represents the average annual number of power outages repaired at node s.

[0124] (12)

[0125] Where, Represents the average annual operation times of the upstream circuit breaker of line ij.

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

[0127] Where, 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] Time for power outage repair in the substation for:

[0129] (14)

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

[0131] Power-off time of area s switching for:

[0132] (15)

[0133] Where, represents the average annual total switching time of the disconnector of the feeder where the substation s is located, It represents the average annual total switching time of the disconnectors of the feeder in the substation s when it is undergoing power outage repair.

[0134] in:

[0135] (16)

[0136] Where, Represents the average annual total switching time of the disconnectors of the feeder where line ij is located.

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

[0138] (18)

[0139] Where, Represents the average switching time required when line rs fails.

[0140] S3. For each flexible interconnection device planning scheme, based on the virtual power flow obtained in step S2, the distribution network line N-1 fault set is divided into a repair power failure set, a switching power failure set, and a seamless fault set according to the power failure type of the user in the substation area;

[0141] When a single line in the distribution network experiences an N-1 fault, different substations experience different types of power outages due to factors such as the distribution network topology and switch locations. A repair power outage refers to a substation recovering power after the fault is repaired, a switching power outage refers to a substation recovering power after the disconnector switches, and a seamless power outage refers to a substation unaffected by the fault.

[0142] The power failure repair set is:

[0143] (19)

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

[0145] The switching power failure fault set is:

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

[0147] Where, represents the set of lines that allow node s to withstand the 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 failure sets are:

[0149] (twenty one)

[0150] Where, Represents the set of lines that do not affect node s when a failure occurs.

[0151] S4. For each flexible interconnection device planning scheme, calculate the power loss index correction value and the power loss index after power transfer at both ends of the substation;

[0152] In the case of a power outage at one end of the interconnected substation area due to repair and power outage at the other end, the power outage time of the substation where the power outage was repaired will be reduced, but the number of power outages will not be changed. The correction value of the power outage time is:

[0153] (twenty two)

[0154] Where, is the failure rate of line ij, and They represent the average repair time and switching time required for line ij to fail; It represents the change in power outage time due to power transfer when the substation p experiences a power outage caused by repair and the interconnected substation experiences a power outage caused by switching. Represents a collection of flexible interconnected areas, represents the set of lines that make the area p withstand the power outage, Represents the set of lines that cause the substation q to withstand switching power outage.

[0155] For the case where one end of the interconnected substation is repaired and the other end is seamless, the power outage time and number of times the power outage area is repaired are reduced. The correction values of power outage time and number are:

[0156] (twenty three)

[0157] (twenty four)

[0158] It represents the change in power outage time due to power transfer when the substation p is repaired and the interconnected substations are not affected by the fault; It represents the change in the number of power outages due to power transfer when the substation p is repaired and the interconnected substations are not affected by the fault; Represents the set of lines that will not cause power outage in area q under fault conditions.

[0159] For the case where one end of the interconnected substation loses power during switching and the other end is seamless, the power outage time and number of the substations with power outages during switching are reduced. The correction values for the power outage time and number are:

[0160] (25)

[0161] (26)

[0162] and They represent the changes in power outage time and number of power outages due to power transfer when the substation p suffers power outage due to switching and the interconnected substations are not affected by the fault;

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

[0164] (27)

[0165] Where, 、 、 and They represent the annual average number of power outages repaired, the time it takes to repair power outages, the number of power outages switched, and the time it takes to switch power outages in area p after it is connected to the flexible interconnection device. 、 、 and They represent the annual average number of repair power outages, repair power outage time, switching power outages, and switching power outage time of the substation p when it is not connected to the flexible interconnection device.

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

[0167] When the power outage type at both ends is repair-switching:

[0168] (28)

[0169] Where, and They represent the number of users in area p who suffer power outage due to repair and switching when line ij fails, represents the total number of users in area p, It represents the number of users in substation p whose power outage type changes due to the FID transfer between substations p and q.

[0170] When the power outage type at both ends is repair-seamless:

[0171] (29)

[0172] Where, represents the number of users in area p who are not affected by power outage when line ij fails;

[0173] When the power failure type at both ends is switching-seamless:

[0174] (30)

[0175] S6. For each flexible interconnection device planning scheme, calculate the reliability index of the entire distribution network, assuming fault load transfer is performed with the user as the smallest unit;

[0176] The reliability indicators of various distribution networks are as follows:

[0177] (31)

[0178] (32)

[0179] (33)

[0180] (34)

[0181] Where: 、 、 and They represent the average power outage frequency, average power outage duration, average power supply availability and expected value of power shortage respectively. represents the total number of users in station area s, and They represent the number of users in area p who suffer power outage due to repair and switching when line ij fails, Represents the total load in the area corresponding to node s.

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

[0183] Taking the minimization of power loss cost as the objective function, the optimal installation location and capacity of the flexible interconnection device are solved. The objective function is:

[0184] (35)

[0185] Where: represents the objective function, and They represent the average annual loss cost of electricity and the average annual loss cost of power outages, respectively.

[0186] in:

[0187] (36)

[0188] (37)

[0189] Where: Represents the average loss coefficient per unit loss of electricity, Represents the average loss coefficient per unit power outage number.

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

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

[0192] The objective function of quadratic optimization is:

[0193] (38)

[0194] Where, represents the objective function of the second optimization, and They 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 respectively.

[0195] in:

[0196] (39)

[0197] (40)

[0198] Where: 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.

[0199] Example 1:

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

[0201] The maximum number of flexible interconnect devices installed was set to 6, with a maximum installed capacity of 0.6 MV•A. After two optimizations, the minimum reliability cost was 176,080 RMB, and the minimum flexible interconnect device installation cost was 723,650 RMB. The specific costs before and after planning are shown in Table 1:

[0202] Table 1 Costs before and after planning

[0203] The reliability indicators before and after planning are shown in Table 2:

[0204] Table 2 Reliability indicators before and after planning

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

[0206] Table 3 FID installation scheme

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

[0208] In summary, the present invention takes into account the user-level load transfer between substations with different power outage types under fault conditions, and proposes a site selection and sizing planning method for flexible interconnection devices in low-voltage substations that takes reliability into consideration. This can help evaluate the effect of flexible interconnection transformation of distribution networks on improving reliability and formulate the optimal installation plan for flexible interconnection devices.

[0209] Corresponding to the aforementioned embodiment of a low-voltage substation flexible interconnection planning method taking into account the power supply capacity of the distribution network, the present invention also provides an electronic device comprising one or more processors for implementing a low-voltage substation flexible interconnection planning method taking into account the power supply capacity of the distribution network in the above embodiment.

[0210] The device embodiments can be implemented through software, hardware, or a combination of software and hardware. Taking software implementation as an example, as a device in a logical sense, it is formed by the processor of any device with data processing capabilities in which it is located reading the corresponding computer program instructions in the non-volatile memory into the memory and running them. From the hardware level, it mainly includes a processor, memory, network interface, and non-volatile memory. In addition, any device with data processing capabilities in which the device in the embodiment is located may also include other hardware according to the actual function of the device with data processing capabilities, which will not be described in detail.

[0211] The implementation process of the functions and effects of each unit in the above-mentioned device is specifically described in the implementation process of the corresponding steps in the above-mentioned method, and will not be repeated here.

[0212] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to the partial description of the method embodiments. The device embodiments described above are merely illustrative, wherein 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 distributed across multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present invention. A person of ordinary skill in the art can understand and implement the present invention without inventive work.

[0213] An embodiment of the present invention also provides a computer-readable storage medium having a program stored thereon. When the program is executed by a processor, a low-voltage substation flexible interconnection planning method considering the power supply capacity of the distribution network in the above embodiment is implemented.

[0214] The computer-readable storage medium may be an internal storage unit of any device with data processing capabilities described in any of the aforementioned embodiments, such as a hard disk or 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. Furthermore, 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 data that has been output or is to be output.

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

Claims

1. A method for planning low-voltage area flexible interconnection devices considering reliability improvement, characterized in that: include: Generate a variable matrix representing the installation locations and port capacities of the flexible interconnection devices and constraints for flexible interconnection device planning, and obtain a set of planning schemes for the flexible interconnection devices; wherein the constraints for flexible interconnection device planning include installation quantity constraints, installation capacity constraints, and transfer power constraints; Solve the virtual power flow model of the distribution network, obtain the virtual power flow of each line in the distribution network for the low-voltage substation node, and calculate the power outage index of the low-voltage substation without access to the flexible interconnection device; including: For the case where one end of the interconnected substation loses power after repair and the other end loses power after switching, the power outage time of the substation that loses power after repair is reduced. The correction value of the power outage time without changing the number of power outages is: Where λ ij is the failure rate of line ij, and They represent the average repair time and switching time required for line ij to fail, FID Represents a collection of flexible interconnected areas; For the case where one end of the interconnected substation is repaired and the other end is seamless, the power outage time and frequency of the repaired substation are reduced by the correction values of the power outage time and frequency respectively: For the case where one end of the interconnected substation loses power while the other end is seamless, the power outage time and frequency of the substation where the switching fails are reduced by the correction values of the power outage time and frequency respectively: Calculate the power outage indicators after power transfer, including: Where, and They represent the annual average number of power outages repaired, the time it takes to repair power outages, the number of power outages switched, and the time it takes to switch power outages in area p after it is connected to the flexible interconnection device. and They represent the annual average number of repair power outages, repair power outage time, switching power outages, and switching power outage time of the substation p when it is not connected to the flexible interconnection device; For each flexible interconnection device planning scheme, the distribution network line N-1 fault set is divided into a repair power failure set, a switching power failure set, and a seamless fault set according to the power failure type of the users in the substation area; For each flexible interconnection device planning scheme, calculate the power loss index correction value of the two end substations and the power loss index after power transfer; For each flexible interconnection device planning scheme, calculate the number of users corresponding to each type of power outage after power transfer; For each flexible interconnection device planning scheme, calculate the reliability index of the entire distribution network, assuming fault load transfer is performed with the user as the smallest unit; including: Where: I SAIFI , I SAIDI , I ASAI and I EENS They represent the average power outage frequency, average power outage duration, average power supply availability and expected power shortage value NC respectively. s represents the total number of users in station area s, and They represent the number of users in area p who suffer power outage due to repair and switching when line ij fails, L s Represents the total load in the area corresponding to node s; Taking the minimization of power loss cost as the objective function, the installation location and capacity of the low-voltage area flexible interconnection device are solved, and a planning method for low-voltage area flexible interconnection devices considering reliability improvement is completed.

2. The method according to claim 1, characterized in that Fault sets are divided based on: When a single line in the distribution network experiences an N-1 fault, different substations will experience different types of power outages due to the influence of the distribution network topology and switch locations. A repair power outage refers to a substation recovering power after the fault is repaired, a switching power outage refers to a substation recovering power after the disconnector switches, and a seamless power outage refers to a substation not affected by the fault. The power failure repair set is: Where, represents the set of lines that allow node s to withstand the power outage, f ij,s is the virtual power flow variable of line ij for node s; The switching power failure fault set is: Where, represents the set of lines that make node s suffer from switching power outage, Ψ S represents the set of nodes directly connected to the upstream substation of the feeder, Ψ i' represents the set of nodes directly connected to node i'; The seamless failure sets are: Where, Represents the set of lines that do not affect node s when a failure occurs.

3. The method according to claim 1, characterized in that Calculate the number of users corresponding to each type of power outage after power transfer, including: When the power outage type at both ends is repair-switching: Where, and They represent the number of users in area p who suffer power outage due to repair and switching when line ij fails, NC p represents the total number of users in area p, represents the number of users in area p whose power outage type changes due to the FID transfer between areas p and q; When the power outage type at both ends is repair-seamless: Where, represents the number of users in area p who are not affected by power outage when line ij fails; When the power failure type at both ends is switching-seamless:

4. The method according to claim 1, wherein The installation quantity constraint is expressed as follows: Where: v ij Represents the low-voltage flexible interconnection variable of the substations corresponding to nodes i and j. It is 1 if there is an interconnection device, and 0 otherwise. Represents the maximum number of installations; The installation capacity constraint is expressed as follows: Where: represents the port capacity of the flexible interconnection device between the stations p and q, The transfer power constraint representing the maximum port capacity is expressed as follows: Where: represents the load power in area p transferred to area q, Represents the distribution transformer capacity of substation q under fault conditions.

5. The method according to claim 1, wherein Taking the minimization of power loss cost as the objective function, the installation location and capacity of the low-voltage flexible interconnection device in the substation are solved, including: The objective function is: My F1=C E +C F Where: F1 represents the objective function, C E and C F They represent the annual average loss cost of electricity and the annual average loss cost of the number of power outages respectively; in: C E =c e I EENS Where: c e Represents the average loss coefficient per unit loss, c f Represents the average loss coefficient per unit power outage number.

6. The method according to claim 1, characterized in that Also includes: Taking the installation cost of the flexible interconnection device as the objective function, the obtained results are optimized twice to obtain the final optimal installation location and capacity of the flexible interconnection device. include: Where F2 represents the objective function of the second optimization, and They 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 respectively; in: Where: c c 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, c r Represents the annual operation and maintenance cost of the flexible interconnection device per unit capacity.

7. An electronic 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 computer program, it implements a low-voltage substation flexible interconnection device planning method considering reliability improvement as described in any one of claims 1-6.

8. A storage medium containing computer-executable instructions, characterized in that: When executed by a computer processor, the computer executable instructions implement a method for planning low-voltage substation flexible interconnection devices that takes reliability improvement into consideration as described in any one of claims 1 to 6.

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