Distributed Fault Self-Healing Method and System for Active Distribution Network Based on Hierarchical Partitioning

Abstract

The present invention belongs to the technical field of active distribution network fault self-healing in the power system, and provides a distributed fault self-healing method and system for an active distribution network based on hierarchical partitioning. Among them, the method includes that when the active distribution network system is operating normally, the intelligent terminal device uses the local topology information configured by itself to perform hierarchical area division on the active distribution network system, and distributes and stores the hierarchical area information; when the operating state of the active distribution network system changes, the intelligent terminal device adaptively updates the stored hierarchical area information; when a fault occurs in a certain section of the feeder in the active distribution network system, the fault section is located and isolated based on the adaptive hierarchical area information and the differential protection principle; after the fault section is isolated, each relevant intelligent terminal device uses the stored network hierarchical area information to perform distributed power supply restoration.

Description

Technical Field

[0001] The invention belongs to the technical field of active distribution network fault self-healing in the power system, and particularly relates to a distributed fault self-healing method and system for an active distribution network based on hierarchical partitioning. Background Technique

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

[0003] With the access of distributed generators (DGs), the fault self-healing technology for accurate fault location, rapid isolation, and autonomous recovery plays a very important role in improving the overall performance of the distribution network. Compared with centralized control, distributed control relying on peer-to-peer communication between terminals reduces the risk of single-point dependence, greatly reduces the computing and communication burdens, has a flexible operation mode, and a faster response.

[0004] In the distributed feeder fault location and isolation of an active distribution network, the differential protection principle has strong adaptability to a two-terminal power network. However, affected by the control link, the fault characteristics of inverter-type DGs are mainly manifested in the amplitude limitation and phase angle mutation of the fault current, which makes the sensitivity of the differential protection with traditional ratio restraint characteristics affected by the load current and the fault characteristics of distributed power sources. Therefore, it is necessary to improve the differential protection criterion for an active distribution network with a large number of inverter-type DGs connected to improve the sensitivity of the protection.

[0005] Existing fully distributed fault recovery methods mainly achieve the recovery process through information interaction between terminals with completely equal status, which is simple, flexible, and has little communication pressure. However, the inventor found that existing recovery methods are mostly based on a pre-fixed topological structure, without considering the adaptability of the method when the operation mode changes, and the recovery query process requires relay-by-relay communication between terminals. When there are many line nodes or a distributed control communication method with a large delay, such as 5G, it will cause an increase in the recovery time. Summary of the Invention

[0006] To solve the technical problems existing in the above background technique, the present invention provides a distributed fault self-healing method and system for an active distribution network based on hierarchical partitioning, which hierarchically partitions the distribution network topology on the basis of fully exerting the flexibility of distributed control, so that the number of levels of information interaction during the recovery process is as small as possible, thereby shortening the recovery time.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a distributed fault self-healing method for an active distribution network based on hierarchical partitioning, which includes:

[0009] When the active distribution network system is operating normally, the intelligent terminal device uses the local topology information configured by itself to divide the active distribution network system into hierarchical regions, and distributes and stores the hierarchical region information;

[0010] When the operating state of the active distribution network system changes, the intelligent terminal device adaptively updates the stored hierarchical region information;

[0011] When a fault occurs in a certain section of the feeder in the active distribution network system, the fault section is located and isolated based on the adaptive hierarchical region information and the differential protection principle;

[0012] After the fault section is isolated, each relevant intelligent terminal device uses the network hierarchical region information stored by it to perform distributed power supply restoration.

[0013] As an implementation method, the intelligent terminal device is installed at each bus node in the active distribution network system.

[0014] As an implementation method, the criterion of the differential protection principle is: the operating current is greater than the product of the braking coefficient and the braking current, and the operating current is greater than the threshold value that does not cause misoperation under normal conditions.

[0015] As an implementation method, the braking current is the product of the minimum value of the current amplitudes on both sides of the line and the compensation coefficient and the proportionality coefficient.

[0016] As an implementation method, the operating current is the magnitude of the sum of the current phasors on both sides of the line.

[0017] As an implementation method, the fault location and isolation strategy is:

[0018] After the intelligent terminal device detects a disturbance, it calculates the current phasor flowing through each switch, and then sends it to the adjacent intelligent terminal device corresponding to the closed switch;

[0019] After receiving the current data, the receiving intelligent terminal device determines the corresponding own switch according to the sending intelligent terminal device number, and then judges the faults inside and outside the section, and disconnects the corresponding switch for the section with an internal fault.

[0020] As an implementation method, in the case where the intelligent terminal device at the tie node does not start, it performs fault judgment after receiving the adjacent current data and returns all 0 data.

[0021] As an implementation method, each relevant intelligent terminal device uses a combination of forward fault information transmission and reverse recovery query to perform fully distributed fault recovery.

[0022] As an implementation manner, after the isolation of the faulty section, the restoration process starts, including determining the end node of the faulty area. The end node forwards the fault information downstream. After receiving the fault information, the tie node starts the restoration query. After the restoration query ends, the tie switch is closed to restore the power supply of the power outage area.

[0023] The second aspect of the present invention provides a distributed fault self-healing system for an active distribution network based on hierarchical partitioning, which includes intelligent terminal devices installed at each bus node in the active distribution network system;

[0024] The intelligent terminal device is configured to:

[0025] When the active distribution network system is operating normally, use the locally configured topology information to perform hierarchical area division on the active distribution network system, and store the hierarchical area information distributively;

[0026] When the operating state of the active distribution network system changes, adaptively update the stored hierarchical area information;

[0027] When a fault occurs in a certain section of the feeder in the active distribution network system, locate and isolate the faulty section based on the adaptive hierarchical area information and the differential protection principle;

[0028] After the isolation of the faulty section, use the stored network hierarchical area information to perform distributed power supply restoration.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] (1) The distributed fault self-healing method for the active distribution network based on hierarchical partitioning of the present invention performs hierarchical partitioning on the network, so that the self-healing time does not increase linearly with the increase of the network scale. Using the improved current differential protection criterion, it has absolute selectivity, high sensitivity, and fast isolation speed.

[0031] (2) The distributed fault self-healing method for the active distribution network based on hierarchical partitioning of the present invention can be well applied to the active distribution network with multiple branches and multiple ties, further expanding the advantages of distributed control. Each STU only needs to configure its own and adjacent local information, and can adaptively obtain the network topology information with the change of the network operation mode, improving the flexibility and reliability of distributed fault self-healing.

[0032] (3) The distributed fault self-healing method for the active distribution network based on hierarchical partitioning of the present invention determines whether the distributed power source is in an island state through network topology identification. The discrimination method is simple and reliable; it can be applied to the terminal devices monitoring all inlets, and can also be applied to the terminal devices monitoring a single switch by setting a bus agent, with strong adaptability.

[0033] Advantages of additional aspects of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Brief Description of the Drawings

[0034] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not unduly limit the present invention.

[0035] Figure 1 It is a target system diagram of an active distribution network in an embodiment of the present invention;

[0036] Figure 2 It is a process diagram of information transfer in the topology query process on the S1 side of the power supply of the present invention;

[0037] Figure 3 It is an overall topology recognition result diagram obtained from the primary topology query process of the present invention;

[0038] Figure 4 It is the operating characteristics of the proposed protection criterion and the ratio restraint characteristic criterion in the amplitude-phase plane;

[0039] Figure 5 It is a system diagram of the information transfer order and the restored system in the first recovery process of an embodiment of the present invention;

[0040] Figure 6 It is an RTDs fault recording diagram in the first recovery process of an embodiment of the present invention;

[0041] Figure 7 It is a system diagram of the information transfer order and the restored system in the second recovery process of an embodiment of the present invention;

[0042] Figure 8 It is an RTDs fault recording diagram in the second recovery process of an embodiment of the present invention. Detailed Embodiment

[0043] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0044] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0045] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0046] Embodiment 1

[0047] This embodiment provides a distributed fault self-healing method for an active distribution network based on hierarchical partitioning, which includes:

[0048] Step 1: When the active distribution network system is operating normally, the intelligent terminal device uses the local topology information configured by itself to perform hierarchical area partitioning on the active distribution network system and stores the hierarchical area information distributively.

[0049] (1-1) Using the buses in the distribution network as the vertices of the graph, and the circuit breakers and transmission lines between the buses as the edges, use the STU to perform hierarchical area partitioning on the network topology and store it.

[0050] Define the nodes with degree 0 or 1 as boundary nodes, such as Figure 1 buses 1, 3, 6, 7 in ; define the nodes with degree greater than 2 as branch nodes, such as bus 2; define the nodes with degree equal to 2 as intermediate nodes, such as buses 4, 5. Define the nodes where the tie switches are located as tie nodes, such as buses 2, 7, and the power source side nodes as power source nodes, such as buses 1, 7. The power source nodes, tie nodes, branch nodes, and boundary nodes are uniformly defined as upper-layer nodes, and the remaining intermediate nodes are defined as lower-layer nodes. The lower-layer nodes connecting two upper-layer nodes belong to the same area.

[0051] (1-2) Each STU generates and stores dynamic information related to the network hierarchical structure and area information according to the configured local information, the designed recognition strategy, and the information processing rules.

[0052] (1-2-1) The local information configured by each STU includes identification information such as STU number, STU communication address, and controlled switch number, attribute information such as whether it is a power source side STU, power source side available capacity margin, whether DG is connected, and DG access switch, and adjacent information such as adjacent STU number, communication address, and corresponding own switch. The topological information configured by each STU is shown in Table 1.

[0053] Table 1 Topological Information Configured by Each STU

[0054]

[0055] (1-2-2) The designed recognition strategy and information processing rules are as follows.

[0056] Rule 1: The power-side STU judges the switch states corresponding to adjacent STUs, stores the closed-state switches and the corresponding STUs as downstream, divides the area numbers according to the number of STUs (represented by "STU number + area number", such as 11, 12), stores them as lower-level area information, and at the same time sends an "information query" instruction as the head node of the lower-level area to the downstream STU. Send a "node status query" instruction to the adjacent STU corresponding to the open-state switch. If the information "node normal and switch closed" is returned, it is judged as a "liaison node".

[0057] Rule 2: When the STU receives the "information query" instruction, it queries the switch states it controls. If all are in the closed state, it enters the 2.1 process; if there is an open switch, it enters the 2.2 process.

[0058] 2.1 Store the sending STU and the corresponding switch as upstream, and the rest as downstream, and query the number of adjacent STUs.

[0059] 2.1.1 If the number is 2, determine itself as an "intermediate node", store the lower-level node information. If DG is connected, send an "area DG information" instruction to the head STU, and continue to forward the "information query" instruction to the downstream STU after receiving the return confirmation information; otherwise, directly forward the "information query" instruction.

[0060] 2.1.2 If the number is 1, determine itself as a "boundary node", store the upper-level area information, and send a "lower-level node return" instruction to the head STU as the end node of the area.

[0061] 2.1.3 If the number is greater than 2, determine itself as a "branch node", store the upper-level area information, send a "lower-level node return" instruction to the head STU as the end node of the area. After receiving the confirmation information, divide the area numbers according to the number of downstream STUs, store them as lower-level area information, and send an "information query" instruction to the adjacent downstream STU as the head node of the lower-level area.

[0062] 2.2 Store the sending STU and the corresponding switch as upstream, and query the number of adjacent STUs

[0063] 2.2.1 If the number is 2, store the upper-level area information. ① If the open switch is an upstream switch: If its own state is normal, determine itself as a "liaison node" and mark the node as an out-of-domain node; if the node loses power, determine itself as a "boundary node". ② If the open switch is not an upstream switch: Send a "node status query" instruction to the STU corresponding to the open-switch side. If the information "node normal and switch closed" is returned, determine itself as a "liaison node" and mark the node as an in-domain node; if the information "node without voltage or switch open" is returned, determine itself as a "boundary node".

[0064] As the regional end node, it sends a "subordinate node return" instruction to the head-end STU.

[0065] 2.2.2 The quantity is greater than 2. ① If the disconnected switch is an upstream switch, store the information of the upper-level region, and then the processing is the same as 2.2.1-①. ② If the disconnected switch is not an upstream switch, send a "node status query" instruction to the STU corresponding to the side of the disconnected switch: ②-1 All return "the node is normal and the switch is closed", determine that itself is a "liaison node", record the node as an in-domain node, store the information of the upper-level region, as the regional end node, send a "subordinate node return" instruction to the head-end STU, after receiving the confirmation information, if there are still switches corresponding to other STUs closed, store the STU and the corresponding switch as downstream, and process according to 2.1.3 for the lower-level region; ②-2 All return "the node has no voltage or the switch is disconnected", if there are switches corresponding to other STUs closed, store the downstream information, according to the number of STUs corresponding to the closed switches, execute the judgment process of 2.1, if not, the processing is the same as 2.1.2; ②-3 Some return "the node has no voltage or the switch is disconnected", if there are no switches corresponding to other STUs closed and only one "the node is normal and the switch is closed" is returned, store the information of the upper-level region, determine that itself is a "liaison node", record the node as an in-domain node, as the regional end node, send a "subordinate node return" instruction to the head-end STU; otherwise, execute the processing of ②-1.

[0066] Rule 3: In a multi-liaison distribution network, a liaison node will receive "information query" instructions from multiple directions, record the order of receipt, the first received is recorded as the restoration direction 1, and increment sequentially. Therefore, there may be information in multiple directions such as (1), (2), (3), etc. in the dynamic information of the liaison node, and the storage of information in different directions is determined by the regional number.

[0067] Rule 4: Upon receiving the "regional DG information" instruction, store the information of the DG nodes in the corresponding lower-level region and return a "DG information confirmation" instruction.

[0068] Rule 5: Upon receiving the "node status query" instruction, check the node status and the switch status of the corresponding sending STU, and return a "node status return" instruction.

[0069] Rule 6: Upon receiving the "subordinate node return" instruction, store the information of the corresponding lower-level region and return a "superior node confirmation" instruction. Judge the nature of the region according to the node type in the information. If it is a boundary node and there are no energized DG nodes in both the boundary and the region, mark the region as a pure load region; if there are energized DG nodes, mark the region as a downstream DG region; if it is a liaison node, mark the region as a downstream liaison region, store the downstream liaison information, non-power nodes send a "liaison information transfer" instruction to the superior node, and power nodes send a "power node information" instruction; if it is other types of nodes, the region flag is to be determined.

[0070] Rule 7: When the area is marked as a pure load area or a downstream DG area, query other lower-level areas. If it is a liaison node or there is a downstream liaison area or a pending area, no operation is performed; otherwise, if all are pure load areas and there is no DG access at the node, send a "lower-level pure load" instruction to the upper-level node, otherwise send a "lower-level downstream DG" instruction to the upper-level node.

[0071] Rule 8: Upon receiving the "liaison information transfer" instruction, mark the corresponding area as a downstream liaison area, store the downstream liaison information. If it is not a power supply node, continue to send the "liaison information transfer" instruction to the upper-level node; the power supply node sends a "power supply node information" instruction to the liaison node.

[0072] Rule 9: Upon receiving the "lower-level pure load" instruction, determine whether there is a DG in the corresponding area. If there is, mark the area as a downstream DG area; otherwise, mark the area as a pure load area.

[0073] Rule 10: Upon receiving "lower-level downstream DG", mark the corresponding area as a downstream DG area.

[0074] Rule 11: Upon receiving the "power supply node information" instruction, store the power supply information in the corresponding direction and return a "power supply information confirmation" instruction.

[0075] In the above rules, the "information query" instruction includes the head-end STU number, communication address, lower-level area number, etc.; the "area DG information" instruction includes the DG node STU number, communication address, area number, etc.; the "DG information confirmation" instruction includes the area number, etc.; the "lower-level node return" instruction includes the end STU number, communication address, upper-level area number, node type, whether energized, whether it is a DG node, restoration direction, etc.; the "upper-level node confirmation" instruction includes the lower-level area number, etc.; the "liaison information transfer" instruction includes the liaison STU number, communication address, restoration direction, upper-level area number, etc.; the "lower-level pure load" instruction and the "lower-level downstream DG" instruction include the upper-level area number, etc.; the "power supply node information" instruction includes the power supply STU number, communication address, restoration direction, etc.; the "power supply information confirmation" instruction includes the liaison STU number, etc.; in addition, all instructions also include the sender STU number.

[0076] Taking Figure 1 the shown system as an example, the topology query process on the S1 side of the power supply is as Figure 2 shown, and the query processes on the other power supply sides are the same.

[0077] TCP / IP communication protocol is adopted between each STU, and long connections are maintained by sending heartbeat messages to ensure real-time performance. The overall topology recognition result obtained from one topology query process is as Figure 3as shown

[0078] (1 - 2 - 3) The dynamic information related to the network hierarchy and regional information includes node information such as node type, liaison node type, switch relative position and status, STU relative position, etc., upper - layer node information such as power source information, superior regional information, inferior regional information, downstream liaison information, and lower - layer node information. The dynamic information stored in each STU is shown in Table 2.

[0079] Step 2: When the operating state of the active distribution network system changes, the intelligent terminal device adaptively updates the stored hierarchical regional information.

[0080] When the STU is initially put into operation or the switch state of the circuit breaker is detected to change, the dynamic information is adaptively updated. The update strategy is set as follows: when the terminal detects a switch position change, it delays for 3 s and then continuously forwards the update instruction to adjacent STUs until the power source side. The power source side STU initiates a topology query again after a 5 - s delay and stores the new dynamic information.

[0081] Table 2 Dynamic information stored in each STU

[0082]

[0083]

[0084] Step 3: When a fault occurs in a certain section of the feeder in the active distribution network system, the fault section is located and isolated based on the adaptive hierarchical regional information and the differential protection principle.

[0085] When a fault occurs on the line, the STUs perform distributed fault location and isolation based on the differential protection principle.

[0086] (2 - 1) The differential protection principle is used to locate and isolate the fault section of the feeder. Among them, the differential protection principle of this embodiment is an improved phase - split differential protection principle. Its operating criterion is shown in the following formula.

[0087]

[0088] In the formula: I0 is the threshold value that does not malfunction under normal conditions, taking 0.1 times the rated current; K rel is the braking coefficient, taking 1. When the penetration rate of rotating - type DG is relatively high, the value can be reduced.

[0089] The operating current I act is shown as follows:

[0090]

[0091] In the formula: are the current phasors on both sides of the line respectively. I actOnly reflects the magnitude of the current flowing through the shunt to ground on the protected line, the braking current I res As shown in the following formula.

[0092]

[0093] In the formula: K c Is the compensation coefficient, considering the unbalanced current generated by the CT during external faults, K c Take 1.2; K p Is the proportionality coefficient. In order to improve the sensitivity of internal faults, it is taken as This formula uses the product of the smaller value of the current amplitudes on both sides and the ratio of the current amplitudes on both sides as the braking quantity, which is only related to the amplitude of the fault current. During internal faults, since the short-circuit current provided by distributed power sources is generally smaller than that on the system side, so I res Takes a smaller value and the protection sensitivity is higher; during external faults, the currents on both sides are through-fault currents, and it can still play a good braking role. Introducing K c Is to compensate for the unbalanced current during external faults. When the braking coefficients are all taken as 1, the protection criterion proposed by the method and the operating characteristics of the ratio braking characteristic criterion in the amplitude-phase plane are as Figure 4 Shown.

[0094] (2-2) The fault location and isolation strategy is as follows: After the STU detects a disturbance, it calculates the current phasors flowing through each switch, and then sends them to the adjacent STU corresponding to the closed switch. After receiving the current data, it determines the corresponding own switch according to the sender STU number, and then judges the internal and external faults of the section. For the section judged to be an internal fault, the corresponding switch is disconnected. For the case where the STU at the liaison node may not start, it is designed to judge the fault after receiving the adjacent current data and return all 0 data.

[0095] For the case where a STU monitors a circuit breaker, it is designed that after the STU detection starts, it first sends a start message to the proxy STU, so that the proxy can know whether each STU on the bus has started before receiving the current data. After the current data calculation is completed, it sends it to the proxy STU again. The strategies for judging internal and external faults of the section are the same, and there may be an additional transfer link of the proxy when disconnecting the corresponding switch.

[0096] (2-3) For the synchronization problem between STUs, the self-synchronization principle based on fault information is used, and the method combining mutation quantity and morphology is adopted to further improve the detection accuracy at the fault moment. The mutation quantity of phase current and phase voltage is used to start the detection method to preliminarily determine the fault moment. Further use the multi-resolution morphological gradient operation. According to the results of the three-level gradient output, determine the intermediate moment between its first maximum value and minimum value as the fault occurrence moment. The threshold of the mutation quantity algorithm is taken as 0.1 times the rated value, and the structural elements of the multi-resolution morphological gradient are all taken as g + = 100·{1}, 0}, g - = 100·{ 0}, 1}, where the underlined part is the origin of the structural element.

[0097] Assume Figure 1 In the illustrated embodiment, a fault occurs in line L3, and each detecting and starting STU executes a location and isolation strategy. Among them, STU2 sends the current of switch K2 to STU1, sends the current of switch K3 to STU3, and sends the current of switch K4 to STU4. After receiving the current of K7 sent by STU4, it is determined that the fault occurs between K4 and K7, and K4 is tripped. Similarly, STU4 controls the tripping of K7 after interactive judgment to isolate the line fault.

[0098] Step 4: After the fault section is isolated, each relevant intelligent terminal device uses the network hierarchical area information stored therein for distributed power supply restoration.

[0099] After the fault is isolated, each STU performs a fully distributed fault recovery in a manner combining forward fault information transfer and reverse recovery query based on the foregoing topology recognition and information storage. The entire fault recovery process is mainly divided into four stages: determining the end node of the fault area, the end node forwarding the fault information downstream, the tie node starting the recovery query after receiving the fault information, and closing the tie switch to restore the power supply of the power outage area after the recovery query ends.

[0100] (4-1) Considering the current situation of DG access in the actual distribution network, during the forward transfer of fault information, island detection is performed using the network topology information, and the DG in the island state is withdrawn.

[0101] First, after the fault is isolated, the fault information is forwarded from the STU where the fault section is located to the end node of the downstream fault area, that is, the upper-layer node closest to the fault section in the power outage area. After the end node of the fault area is determined, the fault information can be transmitted only from the upper-layer node to the lower layer until the tie node. Thus, the corresponding forward fault information transfer process is completed.

[0102] During this process, when a node receives the fault information, if there is DG access, it is judged to be in the island state; if there is also a DG node in the lower-region information of the upper-layer node, an island operation instruction is sent to it before transmitting the fault information. After receiving the instruction, the node is judged to be in the island state and returns the DG output before the fault.

[0103] (4-2) The reverse recovery query process takes into account the cooperation of radial constraint and power supply capacity constraint, and shortens the transmission level through node layering during the information transfer and query process to reduce the recovery time.

[0104] After receiving the fault information, the liaison node requests the available capacity margin from the healthy-side power supply STU, and then conducts a restoration query to the upper-level node of the power outage area. During this process, the query processes of each liaison node are carried out in parallel.

[0105] When the capacity margin is sufficient, restoration is carried out in units of the region and the upper-level node. The capacity to be restored in the region is represented by the difference between the switch flows corresponding to the STUs at both ends of the region and the sum of the pre-fault outputs of the DGs within the region. When there is a load branch at the upper-level node, the branch load is incorporated into the node load. When a certain node can be restored by multiple liaisons, the one with a larger capacity margin is selected for subsequent restoration, and the switch on the side with a smaller capacity margin is disconnected. When the margin is insufficient to restore the entire regional load, query is carried out step by step in units of the lower-level nodes until the margin is insufficient. At this time, the switch is disconnected and the nature of the remaining area to be restored is updated, and the restoration is carried out by other upper-level liaisons. Until the end node of the fault area is queried, the load to be restored between the downstream node of the fault section and the end node of the fault area is obtained in the first stage.

[0106] During the restoration process, information such as capacity, flow, and DG output is represented in active and reactive power, and the pre-fault values are used. The capacity margin consists of S max , P f , and Q f . Among them, S max is the smaller value between the feeder capacity and the available power supply capacity, and P f and Q f are the active and reactive loads of the outgoing line on the power supply side. Sufficient capacity margin means satisfying the following formula:

[0107]

[0108] In the formula: P r and Q r are the loads to be restored during the query process; C r represents the margin after restoring this load and is used to compare different restoration processes. The update of the capacity margin is the update of P f and Q f , as shown in the following formula.

[0109]

[0110] After the restoration query process ends, the end node of the fault area forwards the restoration completion information to the lower level until the liaison node.

[0111] Based on the existing distribution terminal as the hardware platform, an STU with the proposed distributed fault self-healing function is developed. For Figure 1For the system of the illustrated embodiment, RTDs simulation tests are carried out. One STU monitors one circuit breaker, and the numbers correspond one-to-one with the circuit breakers. The set bus agents STUs are STU1, STU2, STU6, STU7, STU9, STU12, and STU13 respectively, and the rest are subordinate STUs. The agents communicate with each other through 5G CPE in the 5G network, and the agent STU communicates with its subordinate STUs through a switch. Assume Figure 1 In the illustrated embodiment, an AB-phase short-circuit fault occurs at the midpoint of line L1, and the S on the S2 and S3 sides max are both 8 MVA. The information transfer order during the restoration process and the system after restoration are as Figure 5 shown, and the RTDs fault recording is as Figure 6 shown. The overall restoration process is roughly as follows:

[0112] After the fault occurs, each activated STU executes the location and isolation strategy. STU1 and 2 judge that the fault occurs between K1 and K2, and the protection trips after 45.4 ms and 41.7 ms respectively. After 30 ms of delay of the simulated circuit breaker by RTDs, the faulty line is removed.

[0113] After detecting the fault isolation, the downstream STU2 of the faulty section determines itself as the end node of the fault area and at the same time as the connection node, and starts the restoration query process, determining the restoration direction through switch K2; at the same time, there is a lower-level non-pure load area, and an island operation instruction is sent to the DG node STU9 in the area, and the capacity margin is queried from the power node STU12.

[0114] After receiving the island operation instruction, STU9 sends a tripping instruction to its subordinate STU11, returns the DG output to STU2, and STU11 trips at 116.3 ms after the fault. After receiving the query instruction, STU12 returns the capacity margin information to STU2.

[0115] After receiving the returned DG output, STU2 sends the fault information to the downstream STU13.

[0116] After receiving the fault information, STU13, which is both a connection node and a power node itself, starts the restoration query.

[0117] After STU2 receives the capacity margin information from STU12, it determines that the area 21 where K3 is located is a pure load area, and the area 22 where K4 is located is a downstream connection area, and waits for the restoration query process of STU13. After receiving the restoration query instruction from STU13, it determines that the capacity margin provided by STU13 can restore the load in area 22. After updating the capacity margin, it compares the magnitudes of the two margins and sends a tripping instruction to STU4 on the smaller side. At 134.9 ms after the fault, STU4 trips out. The remaining margin can restore the load in area 21 and bus 2, and the restoration query process ends. After detecting that K4 is disconnected, STU2 sends a closing instruction to STU5 and a restoration completion instruction to STU13. At 189.1 ms after the fault, STU5 closes, and at 193.7 ms, STU13 closes.

[0118] When it is detected that the switch changes its position, after a delay of 3 s, the subordinate STU sends to the proxy STU, and the proxy STU sends an update instruction to the adjacent proxy STU until the power supply side. The power supply side STU initiates a topology query again after a delay of 5 s, stores the new dynamic information, and re-identifies the new network topology. At this time, if a three-phase short circuit through a 1 Ω transition resistor occurs again at the midpoint of line L5, the self-healing process can still proceed correctly, and the information transfer order during the restoration process and the system after restoration are as Figure 7 shown, and the fault recording of RTDs is as Figure 8 shown. The specific process will not be elaborated here.

[0119] Embodiment 2

[0120] This embodiment provides a distributed fault self-healing system for an active distribution network based on hierarchical partitioning, which includes intelligent terminal devices installed at each bus node in the active distribution network system;

[0121] The intelligent terminal device is configured to:

[0122] When the active distribution network system is operating normally, use the local topology information configured by itself to perform hierarchical area partitioning on the active distribution network system and store the hierarchical area information distributively;

[0123] When the operating state of the active distribution network system changes, adaptively update the stored hierarchical area information;

[0124] When a fault occurs in a certain section of the feeder in the active distribution network system, locate and isolate the fault section based on the adaptive hierarchical area information and the differential protection principle;

[0125] After the fault section is isolated, use the stored network hierarchical area information to perform distributed power supply restoration.

[0126] In this embodiment, the criterion of the differential protection principle is that the operating current is greater than the product of the braking coefficient and the braking current, and the operating current is greater than the threshold value that does not cause misoperation under normal conditions.

[0127] The braking current is the product of the minimum value of the current amplitudes on both sides of the line and the compensation coefficient and the proportionality coefficient.

[0128] The operating current is the magnitude of the sum of the current phasors on both sides of the line.

[0129] Among them, the fault location and isolation strategy is as follows:

[0130] After the intelligent terminal device detects a disturbance, it calculates the current phasor flowing through each switch, and then sends it to the adjacent intelligent terminal device corresponding to the closed switch.

[0131] After receiving the current data, the receiving intelligent terminal device determines the corresponding own switch according to the sending intelligent terminal device number, and then judges the faults inside and outside the section, and disconnects the corresponding switch in the section where the internal fault is judged.

[0132] Specifically, in the case where the intelligent terminal device at the liaison node does not start, it makes a fault judgment after receiving the adjacent current data and returns all 0 data.

[0133] Among them, each relevant intelligent terminal device performs a completely distributed fault recovery by combining forward fault information transmission and reverse recovery query.

[0134] In the specific implementation process, the recovery process starts after the fault section is isolated, including determining the end node of the fault area, the end node forwarding the fault information downstream, the liaison node starting the recovery query after receiving the fault information, and closing the liaison switch to restore the power supply of the power-off area after the recovery query ends.

[0135] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A distributed fault self-healing method for active distribution networks based on hierarchical partitioning, characterized in that including: When the active distribution network system operates normally, the intelligent terminal device uses the local topology information configured by itself to perform hierarchical area division on the active distribution network system, and distributes and stores the hierarchical area information; When the operating state of the active distribution network system changes, the intelligent terminal device adaptively updates the stored hierarchical area information; When a fault occurs in a certain section of the feeder in the active distribution network system, the fault section is located and isolated based on the adaptive hierarchical area information and the differential protection principle; After the fault section is isolated, each relevant intelligent terminal device uses the network hierarchical area information stored by it to perform distributed power supply restoration; The criterion of the differential protection principle is that the operating current is greater than the product of the braking coefficient and the braking current, and the operating current is greater than the threshold value that does not cause misoperation under normal conditions; The braking current is the product of the minimum value of the current amplitudes on both sides of the line and the compensation coefficient and the proportionality coefficient.

2. The distributed fault self-healing method for active distribution network based on hierarchical partitioning as claimed in claim 1, wherein The intelligent terminal device is installed at each bus node in the active distribution network system.

3. The distributed fault self-healing method for active distribution network based on hierarchical partitioning as claimed in claim 1, wherein The operating current is the magnitude of the sum of the current phasors on both sides of the line.

4. The distributed fault self-healing method for active distribution network based on hierarchical partitioning as claimed in claim 1, wherein, The fault location and isolation strategy is: After the intelligent terminal device detects a disturbance, it calculates the current phasor flowing through each switch, and then sends it to the adjacent intelligent terminal device corresponding to the closed switch; After receiving the current data, the receiving intelligent terminal device determines the corresponding own switch according to the sender intelligent terminal device number, and then judges the faults inside and outside the section, and disconnects the corresponding switch in the section where the internal fault is judged.

5. The distributed fault self-healing method for active distribution network based on hierarchical partitioning as claimed in claim 1, wherein In the case where the intelligent terminal device at the tie node does not start, it makes a fault judgment after receiving the adjacent current data and returns all 0 data.

6. The distributed fault self-healing method for active distribution network based on hierarchical partitioning as claimed in claim 1, wherein Each relevant intelligent terminal device performs completely distributed fault restoration by combining forward fault information transfer and reverse restoration query.

7. The distributed fault self-healing method for active distribution network based on hierarchical partitioning as claimed in claim 1, wherein After the fault section is isolated, the restoration process starts, including determining the end node of the fault area, the end node forwarding the fault information downstream, the tie node starting the restoration query after receiving the fault information, and closing the tie switch to restore the power supply of the power outage area after the restoration query ends.

8. A distributed fault self-healing system for an active distribution network based on hierarchical partitioning, based on the distributed fault self-healing method for an active distribution network based on hierarchical partitioning according to any one of claims 1-7, characterized in that, including intelligent terminal devices installed at each bus node in the active distribution network system; The intelligent terminal device is configured to: When the active distribution network system operates normally, use the local topology information configured by itself to perform hierarchical area division on the active distribution network system, and distribute and store the hierarchical area information; When the operating state of the active distribution network system changes, adaptively update the stored hierarchical area information; When a fault occurs in a certain section of the feeder in the active distribution network system, locate and isolate the fault section based on the adaptive hierarchical area information and the differential protection principle; After the fault section is isolated, use the stored network hierarchical area information to perform distributed power supply restoration.

Images