Ground fault location method and system for distributed power supply based on edge computing

Abstract

A method and system for locating ground faults containing distributed power sources based on edge computing. When a ground fault occurs, the edge device obtains the fault quantity measurement of each node from the measurement terminal; the edge computing center obtains the network structure and network parameters of the distribution network containing distributed power sources to establish a fault equivalent circuit, thereby calculating the transient capacitor voltage and transient capacitor current at the ground fault point; the virtual quantity measurement of the virtual node is calculated using the transient capacitor voltage, transient capacitor current and grounding resistance at the fault point; virtual nodes are set on the branches to expand the distribution network; the state of the expanded distribution network is estimated using the fault quantity measurement of each node and the virtual quantity measurement of the virtual node to obtain the state estimation of each node; when the difference between the state estimation of the node and the weighted average residual value of the fault quantity measurement of the node is not greater than the design threshold, the node is determined to be a faulty node, thereby realizing the verification of the ground fault location of the distribution network containing distributed power sources.

Description

Technical Field

[0001] The present invention belongs to the technical field of a novel distributed grounding fault diagnosis and positioning method for a power distribution network, and specifically, relates to a distributed power supply grounding fault positioning method and system based on edge computing. Background Art

[0002] Active intelligent distribution network under the background of new power system is an important part of smart grid. Compared with traditional distribution network, new distribution network has a large number of power electronic equipment with different functions such as new energy power generation, energy storage, electric vehicles, etc., which makes the grid structure, operation mode and fault signal present new characteristics different from traditional distribution network. The electrical signals in new distribution network present many new characteristics, which aggravates the difficulty of fault feature detection, positioning, isolation and recovery control of new distribution network. The single-phase grounding fault identification and positioning technology of distribution network has poor adaptability in distribution network with complex and variable operating environment. Single-phase grounding fault has various causes, including a large number of grounding faults such as instantaneous high resistance, intermittent arc, weak transient signal, strong noise background, etc. The identification and positioning of single-phase grounding fault has always been a technical difficulty. When high resistance and arc grounding fault occur, the dead zone of zero-sequence protection is faced, resulting in multi-point grounding, phase-to-phase short circuit, cable and neutral point small resistance insulation breakdown and burning and other extended hazards. Therefore, the effective diagnosis and positioning of grounding fault is the key to improving the reliability and safety of power supply of new distribution network.

[0003] In the prior art, the FMS operation characteristics and control protection strategies are analyzed in the risk assessment of cascading failures in the flexible distribution system, and a mathematical model of the steady-state operation of the FMS is established; for the single-phase grounding fault of the feeder, the transient operation characteristics of the FMS after the fault are analyzed; based on the four uncertain factors that affect the cascading failure, modeling is performed separately to obtain the load and distributed power output model, equipment failure model, equipment failure time model and protection setting and measurement error model; according to the model, the probability of cascading failures and DG risk are determined by optimizing the flow calculation. The inverter power supply is modeled under the short circuit of the distribution network, and the factors affecting the short-circuit current output of the inverter power supply are classified; the influencing factors of several typical inverters and their short-circuit output currents are determined, and the short-circuit model under all control strategies is established, and the model parameters are fitted. None of the prior art involves the modeling of grounding faults involving distributed power sources, and as the scale and structure of the distribution network become more and more complex, the difficulty of fault location is also increasing. On the one hand, the algorithm running time increases, the fault location speed slows down, and it cannot meet the real-time requirements of distribution network fault location; on the other hand, the algorithms used for distribution network fault location are gradually increasing, but some algorithms have their own limitations. Under the conditions of different distribution network topologies and different fault types, the protection and location coordination mechanism changes have many problems in adaptability. Therefore, considering the actual working conditions of the distribution network, a fault isolation mechanism with adaptive correction characteristics is established to find or construct the most suitable fault location algorithm. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a method and system for locating grounding faults in a distributed power supply based on edge computing, which utilizes edge computing to verify the location of grounding faults in a distribution network containing distributed power supplies.

[0005] The present invention adopts the following technical solution.

[0006] The present invention proposes a method for locating ground faults containing distributed power sources based on edge computing. The distribution network containing distributed power sources includes nodes, Branch road and Measurement terminals, including:

[0007] When a ground fault occurs in the distribution network containing distributed generation, the edge device obtains the fault quantity measurement of each node from the measurement terminal;

[0008] The edge computing center obtains the network structure and network parameters of the distribution network containing distributed power sources to establish a fault equivalent circuit, and calculates the transient capacitor voltage and transient capacitor current at the ground fault point based on the fault equivalent circuit; and calculates the virtual quantity measurement of the virtual node using the transient capacitor voltage, transient capacitor current and ground resistance at the fault point;

[0009] The edge computing center is based on the network structure of the distribution network with distributed power sources. Virtual nodes are set up on the network to expand the distribution network. ; Using the fault quantity measurement of each node and the virtual quantity measurement of the virtual node, the state of the expanded distribution network is estimated to obtain the state estimation of each node; when the difference between the state estimation of the node and the weighted average residual value of the fault quantity measurement of the node is not greater than the design threshold, the node is determined to be a faulty node.

[0010] Preferably, the edge device obtains node 1, node 2, ..., node from the measurement terminal. The fault quantity measurement of each node includes: voltage, current, and power.

[0011] Preferably, establishing a fault equivalent circuit includes:

[0012] Equivalent the distribution network voltage to the power supply;

[0013] The distributed power source is equivalent to the first branch consisting of the internal resistance of the distributed power source and the switch in series, and the on-off of the switch in the first branch is used to fit the distributed power source to access and exit the distribution network;

[0014] The fault line is equivalent to a second branch consisting of two line section equivalent resistances connected in series, wherein the first line section equivalent resistance is the line equivalent resistance from the system side to the fault point, and the second line section equivalent resistance is the line equivalent resistance from the fault point to the load side.

[0015] Preferably, the transient capacitance voltage and transient capacitance current at the ground fault point calculated based on the fault equivalent circuit respectively satisfy the following relationship:

[0016]

[0017] In the formula, is the transient capacitor voltage, is the phase voltage before the fault occurs, is the first attenuation factor, is the resonant frequency, is the system angular frequency, is the system phase angle, where , , R is the line equivalent resistance, L is the equivalent inductance of the line, C The relative distributed capacitance of the circuit;

[0018] The transient capacitor current satisfies the following relationship:

[0019]

[0020] In the formula, is the transient capacitor current, , is the second attenuation factor, , is the equivalent resistance of the first line segment.

[0021] Preferably, each time the distribution network is expanded, the virtual node is only set on one branch, and the node admittance matrix after the distribution network expansion satisfies the following relationship:

[0022]

[0023] In the formula, is the node admittance matrix after the distribution network is expanded, For the Line The self-admittance of the column elements, For the Line The self-admittance of the column elements, , , is the number of nodes in the distribution network, and the virtual node is node.

[0024] Preferably, when the expanded distribution network performs state estimation, the system state vector and the measurement vector satisfy the following relationship:

[0025]

[0026] In the formula, , are the state vector and measurement vector after the expansion of the distribution network, , are the state vector and measurement vector before the expansion of the distribution network, Virtual nodes The real and imaginary parts of the virtual voltage; Virtual nodes The virtual active power and virtual reactive power of is the number of nodes in the distribution network.

[0027] Preferably, the edge computing center, based on the stored network structure of the distribution network containing distributed power sources, sets a virtual node on branch 1 to expand the distribution network, and uses the fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node to estimate the state of the expanded distribution network, and obtains the state estimation vector of each node under the first edge computing. ; Set up a virtual node on branch 2 to expand the distribution network, use the fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node to estimate the state of the expanded distribution network, and obtain the state estimation vector of each node under the second edge calculation ; Similarly, in the branch The virtual nodes are set up on the network to expand the distribution network. The fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node are used to estimate the state of the expanded distribution network. The state estimation vector of each node under the secondary edge computing ; On the branch road The virtual nodes are set up on the network to expand the distribution network. The fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node are used to estimate the state of the expanded distribution network. The state estimation vector of each node under the secondary edge computing . The edge computing center executes Sub-distribution network expansion and After the state estimation, a state estimation matrix is ​​obtained ;

[0028] The edge device obtains the fault measurement vector of each node from the measurement terminal ;

[0029] In the edge computing center, the vector in the state estimation matrix With vector The comparison includes: first extracting the branch where the distributed generation access node is located from the state estimation matrix The state estimation vector determined when setting up the virtual node With vector Compare and then extract other state estimation vectors from the state estimation matrix and vector Make a comparison.

[0030] Preferably, the weighted average residual value of the fault quantity measurement of the node is calculated according to the following relationship:

[0031]

[0032] In the formula, is the weighted average residual value of the node failure measurement, For Node Fault volume measurement, For Node The weight factor of the fault quantity measurement; For Node No. The sub-state estimator, is the number of nodes.

[0033] Preferably, the threshold value is set to be no greater than 0.1.

[0034] The present invention also proposes a ground fault location system containing distributed power sources based on edge computing, wherein the distribution network containing distributed power sources includes: nodes, Branch road and Measurement terminals, including:

[0035] Edge devices are used to obtain fault quantity measurements of each node from the measurement terminal when a ground fault occurs in the distribution network containing distributed power sources;

[0036] The edge computing center is used to obtain the network structure and network parameters of the distribution network containing distributed power sources to establish a fault equivalent circuit, and calculate the transient capacitor voltage and transient capacitor current at the ground fault point based on the fault equivalent circuit; use the transient capacitor voltage, transient capacitor current and ground resistance at the fault point to calculate the virtual quantity measurement of the virtual node; it is also used to calculate the network structure of the distribution network containing distributed power sources in the branch Virtual nodes are set up on the network to expand the distribution network. ; Using the fault quantity measurement of each node and the virtual quantity measurement of the virtual node, the state of the expanded distribution network is estimated to obtain the state estimation of each node; when the difference between the state estimation of the node and the weighted average residual value of the fault quantity measurement of the node is not greater than the design threshold, the node is determined to be a faulty node.

[0037] The beneficial effects of the present invention are that, compared with the prior art, the present invention at least includes that the present invention fully considers that DG access will shunt the fault current, so that the fault phase current is shunted to the non-fault phase, thereby reducing the current difference between the fault phase and the non-fault phase, and uses virtual nodes to expand the distribution network for state estimation, thereby distinguishing the fault node. The fault location algorithm proposed by this method can utilize the multi-source and complementary characteristics of the measurement data to obtain the unique fault location information in the distribution network topology, solve the fault location problem under limited measurement, and greatly reduce the fault search range. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of a method for locating a ground fault of a distributed power source based on edge computing proposed by the present invention;

[0039] Figure 2 is a fault feature model in an embodiment of the present invention;

[0040] Figure 3 is the fault equivalent circuit in the embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0042] The present invention proposes a method for locating ground faults containing distributed power sources based on edge computing. The distribution network containing distributed power sources includes nodes, Branch road and A measurement terminal, such as Figure 1 As shown, including:

[0043] Step 1: When a ground fault occurs in the distribution network containing distributed generation, the edge device obtains the fault quantity measurement of each node from the measurement terminal;

[0044] In the embodiment, the edge device obtains node 1, node 2, ..., node The fault quantity measurement of each node includes but is not limited to: voltage, current, and power.

[0045] Step 2: The edge computing center obtains the network structure and network parameters of the distribution network containing the distributed power source to establish a fault equivalent circuit, and calculates the transient capacitor voltage and transient capacitor current of the ground fault point based on the fault equivalent circuit; and calculates the virtual quantity measurement of the virtual node using the transient capacitor voltage, transient capacitor current and ground resistance of the fault point;

[0046] In the embodiment, a fault characteristic model of a distribution network including distributed power sources is established, such as Figure 2 There are N outgoing wires on the busbar, numbered 1, 2, ..., ,……, When the distribution network system is operating normally, the voltage of each phase , , The current is symmetrical, and the neutral point voltage to ground is zero. When a single-phase grounding fault occurs in the system, the fault point is located at the outgoing line. C phase at point F. Δ i 1AC , Δ i 1BC is the transient charging capacitor current of the two healthy phases A and B on outgoing line 1, Δ i 1CC is the fault discharge current of phase C on outgoing line 1, Δ i JAC , Δ i JBC For outlet The transient charging capacitor current of the two healthy phases A and B, Δ i JCC For outlet The fault discharge current on phase C, Δ i NAC , Δ i NBC For outlet The transient charging capacitor current of the two healthy phases A and B, Δ i NCC For outlet The fault discharge current on phase C, Δ i f is the ground fault current, Δ i JCC is the fault current component flowing into the neutral point on the system side through the fault phase, Δ i JCDC1 is the fault current component flowing into DG1 through the fault phase, Δ i JADC1 and Δ i JBDC1are the fault current components flowing into the neutral point of the system side through phases A and B of DG1, Δ i JCDC2 is the fault current component flowing into DG2 through the fault phase, Δ i JADC2 and Δ i JBDC2 are the fault current components flowing into the neutral point of the system side through the A and B phases of DG2; let Δ i JAC , Δ i JBC is positive, and the direction is from the busbar to the line, then Δ i JADC1 , Δ i JADC2 , Δ i JBDC1 , Δ i JBDC2 It is negative, and the direction is from the line to the busbar. The negative current reduces the amplitude of the positive current. T1 is a transformer.

[0047] In the embodiment, based on the fault characteristic model, the following is established: Figure 3 The fault equivalent circuit shown includes:

[0048] Equivalent distribution network voltage to power supply ;

[0049] Equivalent distributed power supply to the internal resistance of distributed power supply R DG A first branch is formed in series with the switch S, in which the on-off of the switch S is used to fit the distributed power source to access and exit the distribution network;

[0050] The fault line is equivalent to a second branch consisting of two line section equivalent resistances connected in series, wherein the first line section equivalent resistance is the line equivalent resistance from the system side to the fault point, and the second line section equivalent resistance is the line equivalent resistance from the fault point to the load side;

[0051] One end of the power supply is connected in series with the line equivalent inductance, the line relative distributed capacitance and the fault point grounding resistance, the other end of the power supply is connected in parallel with the first branch and the second branch, and the fault point grounding resistance is connected with the equivalent resistance of the first line segment and the equivalent resistance of the second line segment. The inter-line coupling current behind the fault point F is small, and its influence is not considered in the fault characteristic model.

[0052] After a single-phase grounding fault occurs, the voltage of the fault phase drops and the distributed capacitance discharges rapidly. Figure 3 The fault equivalent circuit shown is based on the capacitor voltage As a variable, a fault loop model is established to satisfy the following relationship:

[0053]

[0054] In the formula, is the capacitor voltage, R is the line equivalent resistance, L is the equivalent inductance of the line, C The relative distributed capacitance of the circuit;

[0055] Among them, the line equivalent resistance satisfies the following relationship:

[0056]

[0057] In the formula, is the equivalent resistance of the first line segment, is the equivalent resistance of the second line segment, is the internal resistance of the distributed power supply, is the grounding resistance at the fault point.

[0058] The initial conditions are given by the following relationship:

[0059]

[0060] In the formula, and are the initial values ​​of the transient capacitor voltage before and after the fault occurs, respectively. is the amplitude of the phase voltage before the fault occurs, is the system angular frequency, is the system phase angle;

[0061] The transient capacitor voltage satisfies the following relationship:

[0062]

[0063] In the formula, is the transient capacitor voltage, is the phase voltage before the fault occurs, is the first attenuation factor, is the resonant frequency, where , ;

[0064] The transient capacitor current satisfies the following relationship:

[0065]

[0066] In the formula, is the transient capacitor current, , is the second attenuation factor,

[0067] Figure 3 In the equivalent circuit shown, is the amplitude of the transient current before the fault point of the fault line, i 1(t) is the transient current before the fault point of the fault line; is the amplitude of the transient current passing through the distributed generation superimposed on the fault point of the fault line, i DG (t) is the transient current superimposed on the fault line and passing through the distributed generation. Assume that the current i 1(t) direction is positive, current i DG (t) is negative. When switch S is disconnected, DG exits, and the influence of line coupling current behind the fault point is not considered. Then the transient current before the fault point of the fault line is i 1(t)≈ i c (t), when switch S is closed, DG is turned on, i 1(t)= i c (t)−| i DG (t)|, i DG (t) is the distributed power supply loop current, which causes the transient current of the fault phase before the fault point to decrease and the transient current of the non-fault phase to increase. i DG (t) The current is shunted through the DG circuit, and the shunting amount is affected by the internal resistance of the DG power supply R DG , DG distance to fault point line impedance R L1 The influence of factors.

[0068] The connection of DG will divert the fault current, so that the current of the fault phase is diverted to the non-fault phase, thereby reducing the current difference between the fault phase and the non-fault phase.

[0069] Specifically, the transient capacitor voltage, the transient capacitor current and the grounding resistance of the fault point are used to calculate the virtual quantity measurement of the virtual node, including the virtual voltage, the virtual active power and the virtual reactive power.

[0070] Step 3: Edge computing center, based on the network structure of the distribution network with distributed power sources, Virtual nodes are set up on the network to expand the distribution network. ; Using the fault quantity measurement of each node and the virtual quantity measurement of the virtual node, the state of the expanded distribution network is estimated to obtain the state estimation of each node; when the difference between the weighted average residual value of the state estimation of the node and the fault quantity measurement of the node is not greater than the design threshold, the node is determined to be a faulty node.

[0071] Each time the distribution network is expanded, the virtual node is only set on one branch, and the node admittance matrix after the distribution network expansion satisfies the following relationship:

[0072]

[0073] In the formula, is the node admittance matrix after the distribution network is expanded, For the Line The self-admittance of the column elements, For the Line The self-admittance of the column elements, , , is the number of nodes in the distribution network, and the virtual node is node.

[0074] Specifically, for nodes, Branch road and For a distribution network with distributed power sources and a measurement terminal, since the single-phase fault location method is an a posteriori process, it is necessary to arrange the newly added virtual nodes on each branch in the network, that is, to expand the network topology, and then perform state estimation tests based on the network topology to identify the branch where the fault occurs, so as to traverse the faulty branch. Without loss of generality, the newly added virtual node number is defined as , the system state vector and measurement vector after the network topology is expanded satisfy the following relationship:

[0075]

[0076] In the formula, , are the state vector and measurement vector after the expansion of the distribution network, , are the state vector and measurement vector before the expansion of the distribution network, Virtual nodes The real and imaginary parts of the virtual voltage; Virtual nodes The virtual active power and virtual reactive power of is the number of nodes in the distribution network.

[0077] When the distribution network operates normally, the virtual node The virtual voltage, virtual active power and virtual reactive power of the virtual node are all 0, which is equivalent to the non-existence of this virtual node. When the distribution network is grounded, the virtual node is calculated. The virtual voltage, virtual active power and virtual reactive power of the

[0078] At present, the single-phase grounding fault detection and positioning technology of distribution networks with a high proportion of distributed generation (DG) connected to the grid faces the following problems: the fault characteristics of different types of DG such as photovoltaic and wind power are not the same, resulting in different levels of fault current contributed to the distribution network when the distribution network fails; DG output is easily affected by environmental factors, and its capacity connected to the distribution network affects the power flow characteristics of the distribution network after the fault. The existing distribution network fault positioning method is extremely susceptible to non-fault state disturbances, such as fluctuations in DG output, switching of DG or controllable loads, and other factors.

[0079] Research on the current distribution characteristics of distributed positioning sections and fault location algorithms: When single-phase grounding occurs, the distribution characteristics of zero-sequence grounding current in each power supply section of the grounding line and the normal line, especially the different power supply sections before and after the grounding line fault point, are studied. Based on this current distribution characteristic, an algorithm for grounding line judgment and fault section location for distributed line selection is proposed.

[0080] In order to facilitate the analysis of system faults, we first abstract the fault on a certain line as adding a virtual node to the branch based on the original distribution network topology. At the same time, we assume that the position of the virtual node can be set manually, and we can select the branch where it is located or the specific location of the branch.

[0081] When the system is running normally, the addition of the virtual node will change the network topology, but since its injection power is zero, it does not affect the final state estimation result. Of course, even if the arrangement of the virtual node is changed, the accuracy of the state estimation result will not be greatly affected; when a single-phase grounding fault occurs on a branch of the system, the virtual node injection power is equivalent to the fault load injection power. Only when the virtual node is arranged on the actual fault branch, the network operation state is close to the actual situation, so a more accurate state estimation result can be obtained. If the virtual node is arranged on the non-fault branch, due to the additional addition of a fault load, the system measurement parameter settings and network topology will be greatly different from the actual situation, and its state estimation result will inevitably produce a large deviation. The above judgment can effectively determine the actual location of the single-phase grounding fault line in the network. In addition, it is worth noting that in order to ensure the feasibility of locating the single-phase grounding fault, the duration of the fault on the line should not be shorter than the time required to run multiple linear state estimation programs.

[0082] The method proposed in the present invention improves the network model by setting virtual nodes in the distribution network to improve the accuracy and efficiency of fault location, including: by adding virtual nodes in places where there is no physical connection, the complex network topology can be simplified, which helps the algorithm to simulate the current and identify the fault location more accurately; directly analyzing the original complex network may lead to a high computational burden, and the introduction of virtual nodes can simplify the computational model, while maintaining sufficient accuracy. The amount of data required for processing is reduced, thereby speeding up the fault location process; when some measuring devices fail or data is lost, locating the fault based on virtual nodes can help build a more robust state estimation model to ensure that the fault location task can be effectively completed even in the case of incomplete information; in a distributed control system, the reasonable configuration of virtual nodes is conducive to optimizing the information exchange path, reducing latency and improving the response speed of the entire system, which is crucial for quickly and accurately detecting abnormal conditions in the power grid; advanced analysis tools built based on virtual nodes can provide operators with a more intuitive and detailed network view, and assist in formulating effective maintenance plans and emergency strategies by simulating system behaviors under different scenarios. In short, by properly using virtual node technology, not only can the speed and accuracy of distribution network fault location be improved, but also the reliability and stability of the entire power system can be enhanced.

[0083] In the embodiment, the edge computing center, based on the stored network structure of the distribution network containing distributed power sources, sets a virtual node on branch 1 to expand the distribution network, and uses the fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node to estimate the state of the expanded distribution network, and obtains the state estimation quantity vector of each node under the first edge computing ; Set up a virtual node on branch 2 to expand the distribution network, use the fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node to estimate the state of the expanded distribution network, and obtain the state estimation vector of each node under the second edge calculation ; Similarly, in the branch The virtual nodes are set up on the network to expand the distribution network. The fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node are used to estimate the state of the expanded distribution network. The state estimation vector of each node under the secondary edge computing ; On the branch road The virtual nodes are set up on the network to expand the distribution network. The fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node are used to estimate the state of the expanded distribution network. The state estimation vector of each node under the secondary edge computing . The edge computing center executes Sub-distribution network expansion and After the state estimation, a state estimation matrix is ​​obtained .

[0084] The edge device obtains the fault measurement vector of each node from the measurement terminal .

[0085] In the edge computing center, the vector in the state estimation matrix With vector For comparison,

[0086] Considering the analysis based on the fault characteristic model, it is found that DG access will shunt the fault current, so that the fault phase current is shunted to the non-fault phase, thereby reducing the current difference between the fault phase and the non-fault phase. Therefore, the branch where the distributed generation access node is located is preferentially extracted from the state estimation matrix. The state estimation vector determined when setting up the virtual node With vector Compare and then extract other state estimation vectors from the state estimation matrix and vector Make a comparison.

[0087] Specifically, the weighted average residual value of the node fault quantity measurement is calculated using the following relationship:

[0088]

[0089] In the formula, is the weighted average residual value of the node failure measurement, For Node Fault volume measurement, For Node The weight factor of the fault quantity measurement; For Node No. The sub-state estimator, is the number of nodes.

[0090] When performing state estimation, it is usually impossible to obtain the true state of the system. Even if the edge device obtains the fault measurement of each node from the measurement terminal, there may be problems such as insufficient accuracy. Therefore, the weighted average residual value of the node fault measurement is used. As , which improves the accuracy of fault node positioning, especially in the scenario where DG access will shunt the fault current, so that the fault phase current is shunted to the non-fault phase, thereby reducing the current difference between the fault phase and the non-fault phase. It can ensure the accuracy and reliability of fault positioning, and is therefore more suitable for locating grounding faults involving distributed power sources.

[0091] In the embodiment, when the difference between the state estimation of the node and the weighted average residual value of the fault quantity measurement of the node is not greater than the design threshold, the node is determined to be a faulty node, and the threshold value is set to be no greater than 0.1.

[0092] The fault node location method proposed in the present invention can intuitively obtain the real network topology under the fault condition after the fault node is determined, and when the state is estimated again according to the real network topology, the state estimation result is closest to the real situation.

[0093] The present invention aims at the distributed ground fault diagnosis, positioning and isolation technology of the lines under the new distribution network, and proposes a ground fault model containing distributed power sources based on edge computing. The research results of the invention will enrich the distributed ground fault diagnosis and positioning methods of the new distribution network, and combine the distributed edge computing ground fault diagnosis and positioning intelligent terminal embedded in the FTU to establish a demonstration project to achieve the effect of intelligent distributed fault rapid recovery of ground faults in distribution lines that adapt to the new power system. It is expected to achieve more accurate ground fault positioning and faster fault isolation and recovery. The results of the invention will overcome the impact of distributed power supply access, etc., and provide strong support for the self-healing technology of distribution network faults under the new power system.

[0094] At present, most methods mainly achieve fault location discrimination by defining different indicators, but their results are easily affected by measurement errors, and have high requirements on the distribution of measurement locations and measurement attributes, making it difficult to ensure the feasibility of measurement installation in actual networks. Therefore, a method is proposed to collect all possible measurement attribute data (voltage, current, power) and improve the fault location problem caused by uncertainty factors such as multi-attribute measurement information errors through state estimation. In this paper, the fault node location is considered as a newly added branch power injection, and the measurement attribute data that may be obtained by the decentralized intelligent terminal units is used as the quantity measurement. The voltage state quantity of the unknown node is solved by the weighted least squares state estimation method. All nodes are traversed in turn, with the goal of searching for the state estimation weighted residual mean closest to the true value, to obtain the fault location node information and determine the fault interval. This method defines the state estimation weighted residual mean detection sequence, and uses the weighted residual mean detection value of each node to discriminate the fault node. The fault location algorithm proposed by this method can utilize the multi-source and complementary characteristics of the measurement data to obtain the unique fault location information in the distribution network topology, solve the fault location problem under limited measurement, and greatly reduce the scope of fault search.

[0095] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0096] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above. More specific examples (a non-exhaustive list) of computer-readable storage media include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the above. The computer-readable storage medium used herein is not to be interpreted as a transient signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0097] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0098] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer, partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect through the Internet). In some embodiments, by using the state information of the computer-readable program instructions to personalize an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), the electronic circuit may execute the computer-readable program instructions, thereby implementing various aspects of the present disclosure.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for locating ground faults of distributed power sources based on edge computing. The distribution network containing distributed power sources includes nodes, Branch road and A measurement terminal, characterized in that: include: When a ground fault occurs in the distribution network containing distributed generation, the edge device obtains the fault quantity measurement of each node from the measurement terminal; The edge computing center obtains the network structure and network parameters of the distribution network containing distributed power sources to establish a fault equivalent circuit, and calculates the transient capacitor voltage and transient capacitor current at the ground fault point based on the fault equivalent circuit; uses the transient capacitor voltage, transient capacitor current and ground resistance at the fault point to calculate the virtual quantity measurement of the virtual node, including virtual voltage, virtual active power and virtual reactive power; The edge computing center is based on the network structure of the distribution network with distributed power sources. Virtual nodes are set up on the network to expand the distribution network. ; Using the fault quantity measurement of each node and the virtual quantity measurement of the virtual node, the state of the expanded distribution network is estimated to obtain the state estimation of each node; when the difference between the state estimation of the node and the weighted average residual value of the fault quantity measurement of the node is not greater than the design threshold, the node is determined to be a faulty node.

2. The method for locating ground faults of distributed power sources based on edge computing according to claim 1 is characterized in that: The edge device obtains node 1, node 2, ..., node from the measurement terminal The fault quantity measurement of each node includes: voltage, current, and power.

3. The method for locating ground faults of distributed power sources based on edge computing according to claim 1 is characterized in that: Establish a fault equivalent circuit, including: Equivalent the distribution network voltage to the power supply; The distributed power source is equivalent to the first branch consisting of the internal resistance of the distributed power source and the switch in series, and the on-off of the switch in the first branch is used to fit the distributed power source to access and exit the distribution network; The fault line is equivalent to a second branch consisting of two line section equivalent resistances connected in series, wherein the first line section equivalent resistance is the line equivalent resistance from the system side to the fault point, and the second line section equivalent resistance is the line equivalent resistance from the fault point to the load side.

4. The method for locating ground faults of distributed power sources based on edge computing according to claim 3 is characterized in that: The transient capacitance voltage and transient capacitance current at the ground fault point calculated based on the fault equivalent circuit satisfy the following relationships: ， In the formula, is the transient capacitor voltage, is the phase voltage before the fault occurs, is the first attenuation factor, is the resonant frequency, is the system angular frequency, is the system phase angle, where , , R is the line equivalent resistance, L is the equivalent inductance of the line, C The relative distributed capacitance of the circuit; The transient capacitor current satisfies the following relationship: ， In the formula, is the transient capacitor current, , is the second attenuation factor, , is the equivalent resistance of the first line segment.

5. The method for locating ground faults of distributed power sources based on edge computing according to claim 1 is characterized in that: Each time the distribution network is expanded, the virtual node is only set on one branch, and the node admittance matrix after the distribution network expansion satisfies the following relationship: ， In the formula, is the node admittance matrix after the distribution network is expanded, For the Line The self-admittance of the column elements, For the Line The self-admittance of the column elements, , , is the number of nodes in the distribution network, and the virtual node is node.

6. The method for locating ground faults of distributed power sources based on edge computing according to claim 1, characterized in that: When the expanded distribution network is estimated, the state vector and the measurement vector satisfy the following relationship: ， In the formula, , are the state vector and measurement vector after the expansion of the distribution network, , are the state vector and measurement vector before the expansion of the distribution network, Virtual nodes The real and imaginary parts of the virtual voltage; Virtual nodes The virtual active power and virtual reactive power of is the number of nodes in the distribution network.

7. The method for locating ground faults of distributed power sources based on edge computing according to claim 1, characterized in that: The edge computing center, based on the stored network structure of the distribution network containing distributed power sources, sets a virtual node on branch 1 to expand the distribution network, and uses the fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node to estimate the state of the expanded distribution network, and obtains the state estimation vector of each node under the first edge computing ; Set up a virtual node on branch 2 to expand the distribution network, use the fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node to estimate the state of the expanded distribution network, and obtain the state estimation vector of each node under the second edge calculation ; Similarly, in the branch The virtual nodes are set up on the network to expand the distribution network. The fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node are used to estimate the state of the expanded distribution network. The state estimation vector of each node under the secondary edge computing ; On the branch road The virtual nodes are set up on the network to expand the distribution network. The fault quantity measurement of each node transmitted by the edge device and the virtual quantity measurement of the virtual node are used to estimate the state of the expanded distribution network. The state estimation vector of each node under the secondary edge computing ; The edge computing center executes Sub-distribution network expansion and After the state estimation, a state estimation matrix is ​​obtained ; The edge device obtains the fault measurement vector of each node from the measurement terminal ; In the edge computing center, the vector in the state estimation matrix With vector The comparison includes: first extracting the branch where the distributed generation access node is located from the state estimation matrix The state estimation vector determined when setting up the virtual node With vector Compare and then extract other state estimation vectors from the state estimation matrix and vector Make a comparison.

8. The method for locating ground faults of distributed power sources based on edge computing according to claim 1, characterized in that: The weighted average residual value of the node fault measurement is calculated using the following relationship: ， In the formula, is the weighted average residual value of the node failure measurement, For Node Fault volume measurement, For Node The weight factor of the fault quantity measurement; For Node No. The sub-state estimator, is the number of nodes.

9. The method for locating ground faults of distributed power sources based on edge computing according to claim 1, characterized in that: The threshold value is set to be no greater than 0.

1.

10. A ground fault location system containing distributed power sources based on edge computing, the distribution network containing distributed power sources includes nodes, Branch road and A measurement terminal, characterized in that: include: The edge device is used to obtain the fault quantity measurement of each node from the measurement terminal when a ground fault occurs in the distribution network containing distributed power sources, including virtual voltage, virtual active power and virtual reactive power; The edge computing center is used to obtain the network structure and network parameters of the distribution network containing distributed power sources to establish a fault equivalent circuit, and calculate the transient capacitor voltage and transient capacitor current at the ground fault point based on the fault equivalent circuit; use the transient capacitor voltage, transient capacitor current and ground resistance at the fault point to calculate the virtual quantity measurement of the virtual node; it is also used to calculate the network structure of the distribution network containing distributed power sources in the branch circuit. Virtual nodes are set up on the network to expand the distribution network. ; The state of the expanded distribution network is estimated by using the fault quantity measurement of each node and the virtual quantity measurement of the virtual node to obtain the state estimation of each node; when the difference between the state estimation of the node and the weighted average residual value of the fault quantity measurement of the node is not greater than the designed threshold, the node is determined to be a faulty node.

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