Active power distribution network negative sequence protection method based on 5G edge calculation

Abstract

The invention relates to an active power distribution network negative sequence protection method based on 5G edge calculation. The invention discloses an active power distribution network negative sequence protection method based on 5G edge calculation, and the method comprises the steps: S10, an end layer detects the abrupt change of a negative sequence voltage, transmits a protection starting message to an edge layer, and then transmits a data uploading signal to all intelligent terminals of the end layer through the edge layer; the end layer collects a negative sequence characteristic component and sends the negative sequence characteristic component to the edge layer; s20, after the side layer receives the protection starting message, downloading an incidence matrix T of the topological structure of the active power distribution network from the cloud layer, and generating row vectors V and D from the received data of the negative sequence characteristic component to judge a fault branch; and S30, the edge layer issues an action signal according to a judgment result of the step S20, and the end layer trips off the circuit breaker after receiving the action signal to remove a fault. The active power distribution network negative sequence protection method based on 5G edge calculation is suitable for protection of asymmetric faults of an active power distribution network.

Description

Technical Field

[0001] The present invention belongs to the field of relay protection, and specifically relates to a negative-sequence protection method for an active distribution network based on 5G edge computing. Background Art

[0002] Under the dual carbon goals, the penetration rate of distributed power sources continues to increase, and power electronic equipment has been widely used. As the main carrier for local consumption of distributed power sources, the distribution network has gradually developed from a passive radiation network with unidirectional power flow to an active distribution network with "double high" characteristics and bidirectional power and fault current flow. At present, the distribution network mainly uses a three-stage current protection method to cut off faults, but the large-scale access of distributed power sources has an effect of increasing or draining the fault current of the active distribution network. Therefore, the threshold setting of the traditional three-stage current protection based on the step-by-step increase of the current threshold is difficult, and the time between each level of protection is also difficult to coordinate.

[0003] In recent years, domestic and foreign scholars have conducted extensive explorations on active distribution network relay protection methods from multiple aspects such as fault characteristics, protection principles, and communication methods, using new technologies such as 5G, edge computing, and blockchain, targeting different protection configurations and fault conditions. At present, the research on active distribution network relay protection methods mainly focuses on the following three directions: improved adaptive current protection schemes, longitudinal differential protection schemes based on different fault characteristics, and regional protection schemes. However, these technical solutions still have these problems: inaccuracy of traditional three-stage current protection, data synchronization of longitudinal differential protection, and time delay jitter. Therefore, there is an urgent need for a protection method suitable for asymmetric faults in active distribution networks.

[0004] In view of this, the present invention proposes a new negative-sequence protection method for active distribution networks based on 5G edge computing, which is a protection method for asymmetric faults in active distribution networks and is applied to relay protection of active distribution networks. Summary of the invention

[0005] The first invention object of the present invention is to provide an active distribution network negative sequence protection method based on 5G edge computing, which can accurately determine the fault branch and operate reliably in an asymmetric fault scenario.

[0006] In order to achieve the above purpose, the technical solution adopted is:

[0007] A method for negative sequence protection of an active distribution network based on 5G edge computing comprises the following steps:

[0008] S10: After the end layer detects a sudden change in negative sequence voltage and sends a protection start message to the edge layer, the edge layer sends a data upload signal to all intelligent terminals of the end layer. Meanwhile, the end layer collects negative sequence characteristic components and sends them to the edge layer.

[0009] S20: After receiving the protection start message, the edge layer downloads the active distribution network topology structure association matrix T from the cloud layer, and generates row vectors V and D from the received data of the negative sequence characteristic component to determine the fault branch;

[0010] S30: the edge layer sends an action signal according to the judgment result of step S20, and the end layer trips the circuit breaker after receiving the action signal to eliminate the fault.

[0011] Furthermore, the active distribution network negative sequence protection method further includes step S40: determining whether the fault is removed, and if so, ending the process; otherwise, returning to step S20 until the fault is removed.

[0012] Furthermore, in the step S10, after a sudden change in negative sequence voltage is detected, the criterion for sending a protection start message to the edge layer is: Where: u i(2) is the instantaneous value of the negative sequence voltage at node i, t is the time, and ρ is 0.1 kV / s.

[0013] Furthermore, in step S20, the network with i nodes and j branches forms an active distribution network topology structure association matrix T with i rows and j columns.

[0014] Furthermore, in step S20, the row vectors V and D are expressed as V = [v i ]、D=[d j ]; where: v i represents the negative sequence voltage at node i, d j Indicates the direction of negative sequence power in branch j.

[0015] Furthermore, in the step S20, the method for determining the faulty branch is as follows: the negative sequence voltage of each node is collected, and the node corresponding to the largest negative voltage sequence is the node FN; according to the active distribution network topology association matrix T, the downstream branch row vector L and the number of branches n associated with the node FN are obtained; and the faulty branch is determined according to the upstream and downstream relationship between the faulty branch and the node FN.

[0016] Furthermore, in the method of determining the faulty branch in step S20, if it is upstream, it is the branch corresponding to the first non-zero element in the FNth row of the active distribution network topology structure association matrix T; if it is downstream, the branch with a negative negative sequence power direction is the faulty branch.

[0017] The second invention object of the present invention is to provide an active distribution network negative sequence protection system based on 5G edge computing. The protection system utilizes 5G communication and edge computing to build a cloud-edge-end three-layer protection communication architecture to ensure the safe and reliable operation of the active distribution network.

[0018] In order to achieve the above purpose, the technical solution adopted is:

[0019] An active distribution network negative sequence protection system based on 5G edge computing, comprising:

[0020] End layer: When a sudden change in negative sequence voltage is detected, the detected negative sequence fault characteristic quantity is used to send a fault signal to the edge layer using 5G communication technology; the action signal sent by the edge layer is executed to quickly remove the fault;

[0021] Edge layer: after receiving the fault signal from the end layer, it sends a data upload signal to the end layer, and downloads the active distribution network topology structure association matrix from the cloud layer; after receiving the negative sequence fault characteristic quantity from the end layer, it determines the fault location and sends an action signal to the end layer;

[0022] The cloud layer stores the topological structure information of the active power distribution network and various information sensed when a fault occurs.

[0023] The third invention object of the present invention is to provide an edge computing terminal that can implement the above-mentioned active distribution network negative sequence protection method.

[0024] In order to achieve the above purpose, the technical solution adopted is:

[0025] An edge computing terminal includes a processor and a memory, wherein the memory stores computer executable instructions that can be executed by the processor, and the processor executes the edge computing terminal executable instructions to implement the above-mentioned active distribution network negative sequence protection method.

[0026] A fourth inventive object of the present invention is to provide a computer-readable storage medium that can implement the above-mentioned active distribution network negative sequence protection method.

[0027] In order to achieve the above purpose, the technical solution adopted is:

[0028] A readable storage medium of an edge computing terminal, wherein the readable storage medium stores readable storage medium executable instructions, and when the readable storage medium executable instructions are called and executed by a processor, the readable storage medium executable instructions prompt the processor to implement the above-mentioned active distribution network negative sequence protection method.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] As the penetration rate of distributed power sources in active distribution networks gradually increases, new technical requirements are put forward for relay protection methods. For this reason, based on new technologies such as 5G edge computing, a negative sequence protection method for active distribution networks based on 5G edge computing is proposed in the present invention. It is a negative sequence protection method suitable for asymmetric faults in active distribution networks. It has the following advantages:

[0031] 1. When an asymmetric fault occurs in an active distribution network, a negative sequence characteristic component will be generated. Based on the characteristics of the negative sequence voltage and the direction of the negative sequence power, the technical solution of the present invention can accurately determine the fault branch and operate reliably in an asymmetric fault scenario.

[0032] 2. The technical solution of the present invention utilizes 5G communication and edge computing to construct a cloud-edge-end three-layer protection communication architecture. The end layer is the producer of the data of the entire negative-sequence protection architecture and the executor of the action signal, and transmits the collected data to the edge layer; the edge layer is the data consumer and action signal sender of the entire negative-sequence protection method, which processes and judges the end layer data, transmits the action signal back to the end layer and uploads the data to the cloud layer for storage; the cloud layer is the data storage layer, which mainly stores the topological structure information of the active distribution network and various information perceived when a fault occurs, to ensure the safe and reliable operation of the active distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of a simple active distribution network topology;

[0034] Figure 2 It is the negative sequence network when an asymmetric fault occurs in branch L-2;

[0035] Figure 3 It is a negative sequence network schematic diagram;

[0036] Figure 4 It is the negative sequence voltage distribution diagram;

[0037] Figure 5 Secure communication architecture for cloud-edge-end;

[0038] Figure 6 Implementation process for negative sequence protection of active distribution network based on 5G edge computing. DETAILED DESCRIPTION

[0039] In order to further illustrate the present invention's method for negative-sequence protection of an active distribution network based on 5G edge computing and achieve the intended purpose of the invention, the following is a detailed description of the specific implementation method, structure, features and efficacy of the method for negative-sequence protection of an active distribution network based on 5G edge computing proposed in accordance with the present invention in combination with the preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0040] The following will further introduce in detail a method for negative sequence protection of an active distribution network based on 5G edge computing in conjunction with a specific embodiment of the present invention:

[0041] With the increasing penetration of distributed generation (DG) and the large-scale application of power electronic equipment, the traditional three-stage current protection method currently used in active distribution networks faces problems such as difficulty in setting and coordination. Based on this, the technical solution of the present invention is proposed for the protection of asymmetric faults in active distribution networks. The technical solution of the present invention is:

[0042] A method for negative sequence protection of an active distribution network based on 5G edge computing comprises the following steps:

[0043] S10: After the end layer detects a sudden change in negative sequence voltage and sends a protection start message to the edge layer, the edge layer sends a data upload signal to all intelligent terminals of the end layer. Meanwhile, the end layer collects negative sequence characteristic components and sends them to the edge layer.

[0044] S20: After receiving the protection start message, the edge layer downloads the active distribution network topology structure association matrix T from the cloud layer, and generates row vectors V and D from the received data of the negative sequence characteristic component to determine the fault branch;

[0045] S30: the edge layer sends an action signal according to the judgment result of step S20, and the end layer trips the circuit breaker after receiving the action signal to eliminate the fault.

[0046] Preferably, the active distribution network negative sequence protection method further includes step S40: determining whether the fault is removed, and if so, ending the process; otherwise, returning to step S20 until the fault is removed.

[0047] Preferably, in step S10, after a sudden change in negative sequence voltage is detected, the criterion for sending a protection start message to the edge layer is: Where: u i(2) is the instantaneous value of the negative sequence voltage at node i, t is the time, and ρ is 0.1 kV / s.

[0048] Preferably, in step S20, the network having i nodes and j branches forms an active distribution network topology structure association matrix T with i rows and j columns.

[0049] Preferably, in step S20, the row vectors V and D are expressed as V=[v i ]、D=[d j ]; where: v i represents the negative sequence voltage at node i, d j Indicates the direction of negative sequence power in branch j.

[0050] Preferably, in the step S20, the method for determining the faulty branch is as follows: the negative sequence voltage of each node is collected, and the node corresponding to the largest negative voltage sequence is the node FN; according to the active distribution network topology association matrix T, the downstream branch row vector L and the number of branches n associated with the node FN are obtained; and the faulty branch is determined according to the upstream and downstream relationship between the faulty branch and the node FN.

[0051] Further preferably, in the method of determining the faulty branch in step S20, if it is upstream, it is the branch corresponding to the first non-zero element in the FNth row of the active distribution network topology structure association matrix T; if it is downstream, the branch with a negative negative sequence power direction is the faulty branch.

[0052] An active distribution network negative sequence protection system based on 5G edge computing, comprising:

[0053] End layer: When a sudden change in negative sequence voltage is detected, the detected negative sequence fault characteristic quantity is used to send a fault signal to the edge layer using 5G communication technology; the action signal sent by the edge layer is executed to quickly remove the fault;

[0054] Edge layer: after receiving the fault signal from the end layer, it sends a data upload signal to the end layer, and downloads the active distribution network topology structure association matrix from the cloud layer; after receiving the negative sequence fault characteristic quantity from the end layer, it determines the fault location and sends an action signal to the end layer;

[0055] The cloud layer stores the topological structure information of the active power distribution network and various information sensed when a fault occurs.

[0056] An edge computing terminal includes a processor and a memory, wherein the memory stores computer executable instructions that can be executed by the processor, and the processor executes the edge computing terminal executable instructions to implement the above-mentioned active distribution network negative sequence protection method.

[0057] A readable storage medium of an edge computing terminal, wherein the readable storage medium stores readable storage medium executable instructions, and when the readable storage medium executable instructions are called and executed by a processor, the readable storage medium executable instructions prompt the processor to implement the above-mentioned active distribution network negative sequence protection method.

[0058] The embodiment of the present invention first analyzes the negative-sequence fault characteristics of the negative-sequence voltage and negative-sequence power direction of the active distribution network during an asymmetric fault, and proposes the technical solution of the present invention, which is a new protection method based on the negative-sequence characteristic component. The present invention uses the characteristic that the negative-sequence voltage gradually decreases with the increase of the distance from the fault point to locate one of the end nodes of the fault branch, and combines the improved directional association matrix of the active distribution network to extract the negative-sequence power direction of the downstream associated branch, thereby accurately determining the faulty branch. Secondly, a cloud-edge-end three-layer protection communication architecture is constructed, and the required data is transmitted to the edge layer through 5G communication technology, and all computing tasks are completed at the edge layer, thereby reducing the protection action delay. The embodiments of the present invention are:

[0059] Example 1.

[0060] 1. Analysis of negative sequence fault characteristics of active distribution network

[0061] Distributed power sources can be divided into two types: motor type distributed generator (MTDG) and inverter type distributed generator (IIDG). The electromagnetic transient characteristics of the rotating motor type distributed generator are basically the same as those of the traditional generator, and can be equivalent to a voltage source and an impedance in series. Inverter type distributed power sources need to be connected to the grid through an inverter, and the inverter generally adopts a positive and negative sequence decoupling control strategy when an asymmetric fault occurs in the system to suppress the output of the negative sequence component, which has nonlinear characteristics. Therefore, the inverter type distributed power source can be equivalent to a current source I controlled by the positive sequence voltage at the grid connection point. dg , which can be equivalent to a constant impedance in the negative sequence network of the active distribution network. Figure 1 This is a schematic diagram of a simple active distribution network topology. When an asymmetric fault occurs in branch L-2, the negative sequence network is as follows: Figure 2 shown.

[0062] Figure 2 The fault location parameter α represents the location of the fault point f, and its value range is α∈[0,1]; Z L(x) is the negative sequence equivalent impedance of branch L-2; Z (2) It is the sum of the negative-sequence equivalent impedances of all branches and loads downstream of node 2.

[0063] (1) Negative sequence voltage distribution during asymmetric faults in active distribution networks

[0064] Figure 2 In the negative sequence network shown in the figure, when a metallic asymmetric fault occurs, the transition resistance Z f(2) It can be ignored and is not considered in this embodiment. The negative sequence voltage U 1(2) , U 2(2) It can be expressed as:

[0065]

[0066] Will Figure 2 The simplified negative sequence network is gradually restored, such as Figure 3 shown. Figure 3 Middle Z L2(2) , Z L3(2) is the negative sequence equivalent impedance of branches L-2 and L-3, Z eq1(2) is the sum of the negative sequence equivalent impedance of the branch containing distributed power sources downstream of node 2 and the negative sequence equivalent impedance of the load, Z eq2(2) , Z eq3(2) It is the negative sequence equivalent impedance of the load downstream of node 3 and node 4.

[0067] According to equations (1) and (2), the relationship between the negative sequence voltages of each node can be simply expressed. The negative sequence voltage of node 3 is:

[0068]

[0069] In formula (4), the denominator is always greater than the numerator, so the negative sequence voltage U at node 3 is 3(2) Less than the negative sequence voltage U at node 2 2(2) The negative sequence voltage of node 4 is shown in equation (5), so the negative sequence voltage of node 4 is U 4(2) Less than the negative sequence voltage U at node 3 3(2) .

[0070]

[0071] According to the negative sequence network after gradual restoration, the negative sequence voltages of the remaining nodes are listed one by one, as shown in equations (1), (2), (3), and (5). It can be found that the negative sequence voltage at the fault point f is the largest, and the farther the node is from the fault point, the smaller the negative sequence voltage. Therefore, the negative sequence voltage distribution of a simple asymmetric fault in the active distribution network is as follows: Figure 4 As shown, when a two-phase short circuit occurs, the negative sequence voltage at the fault point f is the highest.

[0072] (2) Negative sequence power direction during asymmetric faults in active distribution networks

[0073] The negative sequence network itself does not reflect the neutral point grounding situation, so the criterion based on the negative sequence characteristic quantity itself is not affected by the neutral point grounding method. In this embodiment, it is stipulated that the positive direction of the negative sequence current is from the node to the branch. Figure 3 It can be seen that when an asymmetric fault occurs in the active distribution network, the direction of the negative sequence current flows from the fault point f to the ground and finally returns to the fault point. Its direction mainly shows two characteristics:

[0074] 1) For installation near the system power supply E s For the directional element on the right side (such as the right side of node 1), the negative sequence power directions of the upstream branch of the fault point and the branch where the fault is located are both "-", and the negative sequence power directions of the downstream branch are both "+".

[0075] 2) For installation far away from the system power supply E s For the directional element on the left side (such as the left side of node 2), the negative sequence power direction of the upstream branch of the fault point is "+", and the negative sequence power direction of the downstream branch and the branch where the fault is located is "-".

[0076] According to the characteristics of the negative sequence power direction, only one side of the branch needs to be installed with the negative sequence power direction element, which reduces the economic expenditure of the active distribution network transformation. This paper stipulates that the negative sequence power direction element is installed near the system power supply E s side.

[0077] 2. Negative sequence protection method

[0078] (1) Calculation principle for starting judgment setting

[0079] Ideally, there is no negative sequence voltage when the active distribution network is operating normally. However, when an asymmetric fault occurs, the negative sequence voltage of the fault branch will suddenly increase. Therefore, the starting criterion is:

[0080]

[0081] Where: u i(2) is the instantaneous value of the negative sequence voltage at node i. When the intelligent terminal detects that the differential of the instantaneous negative sequence voltage over time exceeds ρ, it is considered that an asymmetric fault has occurred. Considering factors such as the transition resistance during a fault, ρ is taken as 0.1 kV / s, which can be adjusted according to the sensitivity requirements and the ability to resist transition resistance.

[0082] (2) Direction correlation matrix

[0083] Figure 1 The connection relationship between the nodes and branches of the simple active distribution network shown can be described by the node-branch association matrix T. For a network with i nodes (i independent nodes) and j branches, an i-row and j-column association matrix T can be formed, whose element t ijIt represents the relationship between node i and branch j. The values ​​of the elements in the association matrix are shown in Table 1.

[0084] Table 1 Values ​​of elements in the association matrix

[0085]

[0086] When node i is associated with branch j, if node i is the head node of branch j, that is, branch j is the downstream branch of node i, t ij Take "-1" if node i is the end node of branch j, that is, branch j is the upstream branch of node i, t ij Take "1"; when node i and branch j are not associated, take "0". Figure 1 The correlation matrix T of the active distribution network shown is shown in formula (6).

[0087]

[0088] When an asymmetric fault occurs in the active distribution network, the negative sequence voltage of each node and the negative sequence power direction of each branch are collected by the smart terminal (STU) at the end layer, and the negative sequence voltage row vector V and negative sequence power direction row vector D are sequentially generated at the edge layer as shown in equations (7) and (8). i represents the negative sequence voltage at node i, d j Indicates the direction of the negative sequence power of branch j. When the negative sequence power direction is positive, d j =1, otherwise d j = 0. This embodiment stipulates that the node flow to the branch is the positive direction of negative sequence power.

[0089] V=[v i ] (7)

[0090] D=[d j ] (8)

[0091] (3) Negative sequence protection principle

[0092] According to the above analysis of "Negative sequence voltage distribution during asymmetric fault in active distribution network", the negative sequence voltage generated when an asymmetric fault occurs in the branch decreases as the distance to the fault point increases. Therefore, when the negative sequence voltage of each node is collected, it is assumed that v FN The maximum value is the corresponding node FN, which must be one of the end nodes of the fault branch FL. According to the association matrix T, the downstream branch row vector L and the number of branches n associated with node FN can be obtained. The elements in L are the branch numbers corresponding to all non-zero elements in the FNth row of the association matrix T. When FN is the end node of a branch of the system, L is an empty vector. The negative sequence power direction of the downstream associated branch of node FN is extracted from D and expressed as a row vector d. The corresponding relationship between L and d is shown in Table (2).

[0093] Table 2 Correspondence between L and d

[0094]

[0095] The element d in the row vector d n By performing a logical “AND” operation, as shown in formula (10), the relationship between the node FN and the faulty branch can be determined according to the difference in the operation result d0.

[0096] d0=d1∧d2∧…d n (10)

[0097] According to the number of downstream associated branches n, it can be divided into two cases: Figure 1 Take this as an example to illustrate.

[0098] 1) When n is 0, L is an empty vector. At this time, node FN is the end node of a branch, and row vector d is an empty vector, so d0 is empty. At this time, the fault branch FL is the branch corresponding to the only non-zero element in the FNth row of T.

[0099]

[0100] For example, when the negative sequence voltage of node 4 is the largest, it can be determined that branch L-3 must be a fault branch.

[0101] 2) When n is greater than or equal to 1, the value of d0 can be obtained from formula (10), which is divided into "0" and "1".

[0102] If the negative sequence power directions of the downstream branches of node FN are all positive, the value of d0 is "1". At this time, the faulty branch is the upstream branch of node FN, and the branch corresponding to the first non-zero element in the FNth row of the association matrix T is the faulty branch.

[0103] If one of the negative-sequence power directions of the downstream branches of the node FN is negative, the value of d0 is "0". At this time, the branch with negative negative-sequence power direction is the fault branch.

[0104] For example, when the negative sequence voltage of node 2 is the largest, if the negative sequence power directions of the downstream branches L-2 and L-4 are both "1", branch L-1 can be judged as the fault branch; if the negative sequence power direction of the downstream branches L-2 or L-4 is "-1", branch L-2 or L-4 can be judged as the fault branch.

[0105] In summary, the upstream and downstream relationship between the fault branch and the node FN can be determined according to formula (10). If it is upstream, it is the branch corresponding to the first non-zero element of the FNth row of the association matrix T; if it is downstream, the branch with negative negative sequence power direction is the fault branch. According to the corresponding relationship between L and d in the table, the fault branch can be determined.

[0106] 3. Cloud-edge-device protection communication architecture based on 5G communication

[0107] The protection architecture of the negative sequence protection method proposed in this embodiment based on 5G edge computing (Mobile Edge Computing, MEC) is as follows: Figure 5 As shown, it is divided into three layers: cloud, edge, and end, thereby proposing an active distribution network negative sequence protection system based on 5G edge computing of the present invention, specifically:

[0108] (1) Communication architecture

[0109] The end layer is the producer of the data of the entire negative sequence protection architecture and the executor of the action signal, and is the "limbs" of the negative sequence protection architecture proposed in this embodiment. The main tasks of the end layer include three: 1) When the end layer detects a sudden change in negative sequence voltage, it sends a fault signal to the edge layer; 2) The negative sequence fault feature detected by the smart terminal is sent to the edge layer using 5G communication technology to provide data support for the edge layer; 3) Execute the action signal sent by the edge layer to quickly remove the fault and ensure the safe and reliable operation of the active distribution network.

[0110] The edge layer is the data consumer and action signal sender of the entire negative sequence protection method, and is the "brain" of the protection proposed in this embodiment. After receiving the fault signal sent by the end layer, the edge layer immediately sends a data upload signal to the end layer, and downloads the active distribution network topology structure association matrix from the cloud layer. After receiving the negative sequence fault feature quantity of the end layer, according to the above-mentioned negative sequence protection principle, the fault location is quickly determined, and an action signal is sent to the end layer.

[0111] The cloud layer is a data storage layer, which mainly stores the topological structure information of the active distribution network and various information sensed when a fault occurs, including: the topological structure association matrix of the active distribution network, the position and status of circuit breakers and load switches, etc. The fault information of the active distribution network, such as the negative sequence voltage of each node and the negative sequence power direction of each branch, will also be uploaded to the cloud in a timely manner when a fault occurs.

[0112] (2) Negative sequence protection action realization

[0113] Figure 6 This is the implementation process of the active distribution network negative sequence protection based on 5G edge computing. The specific implementation process is as follows:

[0114] 1) The smart terminal detects a sudden change in negative sequence voltage and sends a protection start message to the edge layer. After receiving the start message, the edge layer sends a data upload signal to all smart terminals in the end layer. At the same time, the end layer collects negative sequence characteristic components and sends them to the edge layer.

[0115] 2) After receiving the protection start message, the edge layer downloads the active distribution network topology structure association matrix T from the cloud layer.

[0116] 3) The edge layer generates row vectors V and D from the received data of negative sequence characteristic components, and determines the faulty branch according to the above protection principle.

[0117] 4) The edge layer sends an action signal based on the judgment result. After receiving the signal, the end layer trips the circuit breaker and the fault is removed.

[0118] Example 2.

[0119] An active distribution network negative sequence protection system based on 5G edge computing, comprising:

[0120] End layer: When the end layer detects a sudden change in negative sequence voltage, it sends a fault signal to the edge layer. The negative sequence fault feature detected by the smart terminal is sent to the edge layer using 5G communication technology to provide data support for the edge layer. The action signal sent by the edge layer is executed to quickly cut off the fault and ensure the safe and reliable operation of the active distribution network.

[0121] Edge layer: After receiving the fault signal from the end layer, it sends a data upload signal to the end layer, and downloads the active distribution network topology structure association matrix from the cloud layer; after receiving the negative sequence fault characteristic quantity of the end layer, according to the above negative sequence protection principle, after determining the fault location, it sends an action signal to the end layer.

[0122] Cloud layer: mainly stores the topological structure information of the active distribution network and various information sensed when a fault occurs, including: the topological structure association matrix of the active distribution network, the position and status of circuit breakers and load switches, etc. The fault information of the active distribution network, such as the negative sequence voltage of each node and the negative sequence power direction of each branch, will also be uploaded to the cloud in a timely manner.

[0123] Example 3.

[0124] A negative sequence protection method for an active distribution network based on 5G edge computing adopts the protection system of Example 2, and the specific operation steps are as follows:

[0125] S10: After the end layer detects a sudden change in negative sequence voltage, it sends a protection start message to the edge layer. After receiving the start message, the edge layer sends a data upload signal to all intelligent terminals in the end layer. At the same time, the end layer collects negative sequence characteristic components and sends them to the edge layer.

[0126] Among them, after detecting a sudden change in negative sequence voltage, the criterion for sending a protection start message to the edge layer is: Where: u i(2) is the instantaneous value of the negative sequence voltage at node i. When the intelligent terminal detects that the differential of the instantaneous negative sequence voltage over time exceeds ρ, it is considered that an asymmetric fault has occurred. Considering factors such as the transition resistance during a fault, ρ is taken as 0.1 kV / s, which can be adjusted according to the sensitivity requirements and the ability to resist transition resistance.

[0127] S20: After receiving the protection start message, the edge layer downloads the active distribution network topology structure association matrix T from the cloud layer, and generates row vectors V and D from the received negative sequence characteristic component data to determine the fault branch.

[0128] The active distribution network topology structure association matrix T is the same as that described in Embodiment 1, which is an active distribution network topology structure association matrix T having i rows and j columns formed by a network with i nodes and j branches.

[0129] When an asymmetric fault occurs in the active distribution network, the negative sequence voltage of each node and the negative sequence power direction of each branch are collected by the end layer smart terminal (Smart Terminal Unit, STU), and the negative sequence voltage row vector V and negative sequence power direction row vector D are sequentially generated at the edge layer as shown in equations (7) and (8). i represents the negative sequence voltage at node i, d j Indicates the direction of the negative sequence power of branch j. When the negative sequence power direction is positive, d j =1, otherwise d j =0. This embodiment stipulates that the node flow to the branch is the positive direction of negative sequence power. The row vectors V and D are expressed as V = [vi], D = [d j ]; where: v i represents the negative sequence voltage at node i, d j Indicates the direction of negative sequence power in branch j.

[0130] The method for determining the faulty branch is the same as that in Example 1, which is: the negative sequence voltage of each node is collected, the node corresponding to the largest negative voltage sequence is node FN, and the downstream branch row vector L and the number of branches n associated with node FN are obtained according to the active distribution network topology structure association matrix T, and the faulty branch is determined according to the upstream and downstream relationship between the faulty branch and node FN. If it is upstream, it is the branch corresponding to the first non-zero element of the FNth row of the active distribution network topology structure association matrix T; if it is downstream, the branch with a negative negative sequence power direction is the faulty branch.

[0131] S30: the edge layer sends an action signal according to the judgment result of step S20, and the end layer trips the circuit breaker after receiving the action signal to eliminate the fault.

[0132] S40: Determine whether the fault is eliminated. If so, end the process; otherwise, return to step S20 until the fault is eliminated.

[0133] Example 4.

[0134] An edge computing terminal includes a processor and a memory, the memory stores edge computing terminal executable instructions that can be executed by the processor, and the processor executes the edge computing terminal executable instructions to implement the active distribution network negative sequence protection method of Example 2.

[0135] Example 5.

[0136] A readable storage medium of an edge computing terminal, wherein the readable storage medium stores readable storage medium executable instructions, and when the readable storage medium executable instructions are called and executed by a processor, the readable storage medium executable instructions prompt the processor to implement the active distribution network negative sequence protection method of Example 2.

[0137] The above is only a preferred embodiment of the embodiment of the present invention, and does not impose any form of limitation on the embodiment of the present invention. Any simple modification, equivalent changes and modifications made to the above embodiment based on the technical essence of the embodiment of the present invention are still within the scope of the technical solution of the embodiment of the present invention.

Claims

1. A negative sequence protection method for active distribution network based on 5G edge computing, characterized in that: The following steps are involved: S10: After the end layer detects a sudden change in negative sequence voltage and sends a protection start message to the edge layer, the edge layer sends a data upload signal to all intelligent terminals of the end layer. Meanwhile, the end layer collects negative sequence characteristic components and sends them to the edge layer. S20: After receiving the protection start message, the edge layer downloads the active distribution network topology structure association matrix T from the cloud layer, and generates row vectors V and D from the received data of the negative sequence characteristic component to determine the fault branch; S30: the edge layer sends an action signal according to the judgment result of step S20, and the end layer trips the circuit breaker after receiving the action signal to eliminate the fault.

2. The method for negative sequence protection of active distribution network according to claim 1, characterized in that: The active distribution network negative sequence protection method further includes step S40: determining whether the fault is removed, and if so, ending the process; otherwise, returning to step S20 until the fault is removed.

3. The method for negative sequence protection of active distribution network according to claim 1, characterized in that: In the step S10, after a sudden change in negative sequence voltage is detected, the criterion for sending a protection start message to the edge layer is: Where: u i(2) is the instantaneous value of the negative sequence voltage at node i, t is the time, and ρ is 0.1 kV / s.

4. The method for negative sequence protection of active distribution network according to claim 1, characterized in that: In the step S20, the network with i nodes and j branches forms an active distribution network topology structure association matrix T with i rows and j columns.

5. The method for negative sequence protection of active distribution network according to claim 1, characterized in that: In step S20, the row vectors V and D are expressed as V = [v i ]、D=[d j ]; where: v i represents the negative sequence voltage at node i, d j Indicates the direction of negative sequence power in branch j.

6. The method for negative sequence protection of active distribution network according to claim 1, characterized in that: In the step S20, the method for determining the faulty branch is as follows: the negative sequence voltage of each node is collected, the node corresponding to the largest negative voltage sequence is the node FN, and according to the active distribution network topology association matrix T, the downstream branch row vector L and the branch number n associated with the node FN are obtained, and the faulty branch is determined according to the upstream and downstream relationship between the faulty branch and the node FN.

7. The method for negative sequence protection of active distribution network according to claim 6, characterized in that: In the method of determining the faulty branch in step S20, if it is upstream, it is the branch corresponding to the first non-zero element in the FNth row of the active distribution network topology structure association matrix T; if it is downstream, the branch with a negative negative sequence power direction is the faulty branch.

8. An active distribution network negative sequence protection system based on 5G edge computing, characterized in that: include: End layer: When a sudden change in negative sequence voltage is detected, the detected negative sequence fault characteristic quantity is used to send a fault signal to the edge layer using 5G communication technology; the action signal sent by the edge layer is executed to quickly remove the fault; Edge layer: after receiving the fault signal from the end layer, it sends a data upload signal to the end layer, and downloads the active distribution network topology structure association matrix from the cloud layer; after receiving the negative sequence fault characteristic quantity from the end layer, it determines the fault location and sends an action signal to the end layer; The cloud layer stores the topological structure information of the active power distribution network and various information sensed when a fault occurs.

9. An edge computing terminal, characterized in that: It includes a processor and a memory, the memory stores edge computing terminal executable instructions that can be executed by the processor, and the processor executes the edge computing terminal executable instructions to implement the active distribution network negative sequence protection method described in any one of claims 1-7.

10. A readable storage medium of an edge computing terminal, characterized in that: The readable storage medium stores readable storage medium executable instructions. When the readable storage medium executable instructions are called and executed by the processor, the readable storage medium executable instructions prompt the processor to implement the active distribution network negative sequence protection method described in any one of claims 1-7.

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