A novel power distribution network high-resistance ground fault feature spectrum construction method and system

Abstract

The application belongs to the field of power distribution network fault analysis, and provides a novel power distribution network high-resistance grounding fault feature map construction method and system. A novel power distribution network model containing photovoltaic, hybrid energy storage and V2G units is established, a high-resistance grounding fault point is equivalent to a series connection of a pre-fault phase voltage and a system ground equivalent impedance and a high-resistance fault channel, a fault phase current is calculated, and a rainstorm and damp type high-resistance grounding fault scenario is determined. Various resource operating conditions are sequentially set, and control variables of each resource operating condition are configured. The novel power distribution network model is simulated and run, and data is collected. Feature data collected from four operating conditions are arranged into a feature matrix in a unified feature order, and each feature dimension is normalized. A high-resistance grounding fault feature heat map is generated according to the normalized feature matrix, and a feature radar chart corresponding to the operating condition is generated, forming a high-resistance grounding fault feature map. The application can provide a mapping basis for fault identification, protection configuration and operation analysis.

Description

Technical Field

[0001] This invention belongs to the field of power distribution network fault analysis, specifically involving a novel method and system for constructing a feature map of high-resistivity grounding faults in power distribution networks. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] As distributed photovoltaic, energy storage devices, and electric vehicle charging facilities with vehicle-to-grid (V2G) interaction capabilities are continuously connected to the power distribution network, the sources of current, the support methods of node voltage, and the distribution process of local power during faults have changed, making fault analysis methods that rely on single current or voltage thresholds less applicable.

[0004] Overhead power distribution lines span large geographical areas and operate in complex environments, making them susceptible to continuous rainfall. Heavy rain can cause moisture to accumulate on the surfaces of insulators, at the connection points of conductor hardware, and on crossarms. The combined effect of water film and contaminant layers reduces the equivalent surface resistance of the insulation and increases leakage current. When local insulation is not completely broken down and only an incomplete conductive path is formed between the phase conductor and ground, the fault manifests as a high-resistance grounding fault. This type of fault has a large grounding path resistance, significantly limiting the fault current. The node voltage typically does not experience a deep drop, and it is characterized by weak current and voltage disturbances, as well as persistent imbalance.

[0005] Compared to metallic single-phase grounding faults, high-resistivity grounding faults exhibit smaller voltage drops and zero-sequence current amplitudes, making them difficult to identify reliably and promptly using traditional overcurrent protection or undervoltage criteria. Although the instantaneous current is small, the high-resistivity path continuously consumes active power, potentially generating thermal effects and exacerbating insulation carbonization, ultimately leading to a permanent grounding fault. The risk of high-resistivity grounding faults depends not only on the magnitude of the fault current but also on their concealed, persistent, and progressive characteristics.

[0006] Existing distribution network fault analyses typically focus on single or a few electrical quantities, such as node voltage, zero-sequence current, or negative-sequence current, while failing to adequately consider the dynamic response of resource power generated after the aggregation and access of multiple resources, including photovoltaics, energy storage, and V2G. Furthermore, different characteristic quantities have different dimensions and orders of magnitude, making direct comparison on a unified scale difficult. Observing only a single time-domain curve makes it difficult to simultaneously distinguish between the intrinsic characteristics of the fault and the extended characteristics caused by resource operation modes, and also hinders the formation of reusable fault characteristic data. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a novel method and system for constructing a fault feature map of a distribution network with high resistance grounding. Under unified fault conditions, this invention organizes multiple resource operating conditions, collects node electrical quantities and resource power quantities, extracts multidimensional feature quantities with clear physical meanings and normalizes them, and then constructs a fault feature map combining heat maps and radar maps. This solves the problems of insignificant voltage drop and small zero-sequence current amplitude in high resistance grounding faults under rain and damp conditions, as well as the increased fault response dimensions and difficulty in fully representing a single feature after the access of photovoltaic, energy storage and charging resources.

[0008] According to some embodiments, the present invention adopts the following technical solution: A novel method for constructing a characteristic map of high-resistivity grounding faults in a power distribution network includes the following steps: A novel distribution network model incorporating photovoltaic, hybrid energy storage, and V2G units is established. The novel distribution network model includes multiple nodes, with some nodes connected to photovoltaic units, some nodes connected to energy storage units, and some nodes connected to V2G units. The high-resistance grounding fault point is equivalent to the phase voltage before the fault being connected in series with the high-resistance fault path through the system's equivalent impedance to ground. The fault phase current is calculated to determine the fault scenario of high-resistance grounding caused by rainstorm and moisture. Under the same topology, fault location, fault phase and fault time period, four resource operation conditions are set in sequence: no resource access, photovoltaic and hybrid energy storage access, photovoltaic, hybrid energy storage and V2G unit charging, photovoltaic, hybrid energy storage and V2G unit discharging, and control variables for each resource operation condition are configured. Based on the set resource operating conditions and configured control variables, the new power distribution network model is simulated and run, and node parameter and resource parameter data are collected. The feature data collected from the four working conditions were combined into a feature matrix according to a unified feature order, and each feature dimension was normalized. A heat map of high-resistance grounding fault features is generated based on the normalized feature matrix, and a feature radar map of the corresponding operating condition is generated to form a high-resistance grounding fault feature map.

[0009] As an alternative implementation method, the process of establishing a new distribution network model containing photovoltaic, hybrid energy storage and V2G units includes: based on the distribution system, connecting photovoltaic, hybrid energy storage and V2G units to multiple main nodes and branch nodes, and setting up three-phase voltage, current and operation quantity measurement modules at each node.

[0010] As a further defined implementation, the main trunk of the new distribution network model includes multiple nodes, some of which have branches. One node is connected to the upstream power source or substation. The neutral point of the main power source is grounded through a small resistor to provide a zero-sequence current path for single-phase grounding and high-resistance grounding faults. The resource side is connected to the distribution network through a three-phase double-winding transformer. The rated line voltage of the main power source and the rated line voltage of the low-voltage side of the transformer are set. The connection group adopts the Dyn11 connection method with high-voltage side delta and low-voltage side star and a neutral point.

[0011] As an alternative implementation method, the process of connecting some nodes to photovoltaic units, some nodes to energy storage units, and some nodes to V2G units includes: at least one node connecting to two photovoltaic units, and each of the other photovoltaic nodes connecting to one unit; the hybrid energy storage unit adopts a hybrid structure of batteries and supercapacitors, and realizes energy exchange through a bidirectional DC / DC converter, a common DC bus, and a three-phase PWM grid-connected converter; the V2G unit realizes the switching between charging and discharging modes through a bidirectional power conversion interface, and each node is equipped with a measurement module.

[0012] As an alternative implementation, the high-resistance grounding fault point is equivalent to the phase voltage before the fault being connected in series with the high-resistance fault channel through the system's equivalent impedance to ground. The process of calculating the fault phase current includes: setting each phase to ground fault, limiting the fault current by configuring a grounding resistance greater than the set value, so that the fault manifests as weak grounding, weak current and weak voltage drop. A high-resistance grounding fault point is equivalent to the phase voltage before the fault being connected in series with the high-resistance fault path through the system's equivalent impedance to ground. The fault phase current is calculated, and then the active power consumed in the high-resistance fault path is calculated.

[0013] As an alternative implementation method, the process of determining the fault scenario of high-resistance grounding due to rainstorm moisture includes: corresponding the fault to the insulation moisture process under continuous rainfall: continuous rainfall causes the insulation surface to become damp, the surface resistance decreases, and leakage current accumulates; when an incomplete conductive path with a large resistance is formed at a local location, a high-resistance grounding fault occurs at the corresponding node.

[0014] As an optional implementation method, the process of sequentially setting four resource operation conditions includes: no resource access, photovoltaic and hybrid energy storage access, photovoltaic, hybrid energy storage and V2G unit charging, and photovoltaic, hybrid energy storage and V2G unit discharging. The four resource operation conditions adopt the same network topology, fault location, fault phase, fault activation and deactivation time, and measurement configuration, and control the resource access status only through tp, tb, tvoff and kv.

[0015] As an alternative implementation method, the simulation operation of the new power distribution network model is carried out according to the set resource operating conditions and configured control variables. The process of collecting node parameter and resource parameter data includes: running the pre-built simulation script, sequentially executing the basic parameter setting, operating condition definition, measurement variable declaration, cyclic simulation, result extraction, plotting and result saving procedures, clearing the basic working area variables left over from the previous operating condition before each operating condition starts, writing the control variables of the current operating condition into the basic working area and then calling the model to run, and storing each node quantity and resource quantity into the corresponding result structure.

[0016] As an alternative implementation method, the simulation operation of the new distribution network model is carried out based on the set resource operating conditions and configured control variables. The process of collecting node parameters and resource parameter data includes: focusing on monitoring the fault point node and downstream nodes. Node quantities include three-phase voltage, current and the effective values, zero-sequence quantities and negative-sequence quantities obtained from them; resource quantities include the voltage, current, active power, reactive power of photovoltaic, energy storage and V2G and the state of charge of energy storage. The node voltage drop depth is calculated according to the difference between the voltage before the fault and the lowest voltage during the fault. The zero-sequence sensitivity coefficient is used to characterize the weak zero-sequence disturbance of the high-resistance grounding fault relative to the normal operating conditions. The negative-sequence disturbance index is used to characterize the cumulative degree of the negative-sequence component deviating from the normal state within the fault duration interval. By comparing the deviation of the resource active power during the fault period from the average power before the fault, the power changes of photovoltaic, energy storage and V2G are extracted.

[0017] As an alternative implementation, the process of generating a high-resistance grounding fault feature heatmap based on the normalized feature matrix and generating a feature radar map of the corresponding operating conditions to form a high-resistance grounding fault feature map includes: generating a high-resistance grounding fault feature heatmap based on the normalized feature matrix, and generating feature radar maps of four resource operating conditions with each feature as the coordinate axis; using the heatmap to compare the relative strength of individual features under different operating conditions, and using the radar map to compare the overall contour of each operating condition in the multi-dimensional feature space, thereby forming a high-resistance grounding fault feature map.

[0018] A novel system for constructing characteristic maps of high-resistivity grounding faults in power distribution networks includes: The new distribution network model construction module is configured to establish a new distribution network model containing photovoltaic, hybrid energy storage and V2G units. The new distribution network model includes multiple nodes, some of which are connected to photovoltaic units, some of which are connected to energy storage units and some of which are connected to V2G units. The rainstorm scenario setting module is configured to treat the high-resistance grounding fault point as equivalent to the phase voltage before the fault being connected in series with the high-resistance fault channel through the system's equivalent impedance to ground, calculate the fault phase current, and determine the fault scenario of rainstorm-induced high-resistance grounding. The resource operation condition setting module is configured to set four resource operation conditions in sequence under the same topology, fault location, fault phase and fault time period: no resource access, photovoltaic and hybrid energy storage access, photovoltaic, hybrid energy storage and V2G unit charging, and photovoltaic, hybrid energy storage and V2G unit discharging. The control variables for each resource operation condition are configured. The simulation operation module is configured to perform simulation operation of the new power distribution network model based on the set resource operating conditions and configured control variables, and to collect node parameter and resource parameter data. The normalization processing module is configured to form a feature matrix from the feature data collected under the four working conditions according to a uniform feature order, and to perform normalization processing on each feature dimension. The fault feature map generation module is configured to generate a high-resistance grounding fault feature heat map based on the normalized feature matrix, and generate a feature radar map of the corresponding operating condition, thus forming a high-resistance grounding fault feature map.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: Under the unified conditions of distribution network topology, fault location, fault time period and measurement quantity, this invention performs batch simulation or data acquisition on different operating conditions under different resource combinations, and jointly extracts voltage drop, minimum voltage, zero-sequence current, negative-sequence current and changes in photovoltaic, energy storage and V2G power. It also forms a multi-dimensional high-resistivity grounding fault feature map through normalized heat map and radar map, providing a map-based basis for fault identification, protection configuration and operation analysis.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is a diagram of an IEEE 33-node distribution network topology under a novel resource access implementation, according to one embodiment. Figure 2 A modeling diagram of a high-resistance grounding fault at node 8 in one embodiment; Figure 3 This is a diagram illustrating the physical process of a rainstorm-induced high-resistivity grounding fault according to one embodiment. Figure 4 This is a curve showing the effective value variation of the phase voltage of node 33 under four operating conditions in one embodiment; Figure 5 This is a curve showing the effective value variation of the phase voltage of node 18 under four operating conditions in one embodiment; Figure 6 This is a zero-sequence current curve of node 33 under four operating conditions in one embodiment; Figure 7 This is a negative sequence current curve of node 33 under four operating conditions in one embodiment; Figure 8 This is a photovoltaic active power response curve in one embodiment; Figure 9 This is an example of an energy storage active power response curve; Figure 10 This is a V2G active power response curve in one embodiment; Figure 11 This is a thermal diagram illustrating the characteristics of a high-resistance grounding fault in one embodiment. Figure 12 This is a radar image showing the characteristics of a high-resistance grounding fault in one embodiment. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0027] Example 1 A novel method for constructing a characteristic map of high-resistivity grounding faults in a distribution network containing photovoltaic, energy storage, and charging resources under heavy rain conditions, specifically including the following steps: A novel distribution network model incorporating photovoltaic, hybrid energy storage, and V2G units is established. The novel distribution network model includes multiple nodes, with some nodes connected to photovoltaic units, some nodes connected to energy storage units, and some nodes connected to V2G units. The high-resistance grounding fault point is equivalent to the phase voltage before the fault being connected in series with the high-resistance fault path through the system's equivalent impedance to ground. The fault phase current is calculated to determine the fault scenario of high-resistance grounding caused by rainstorm and moisture. Under the same topology, fault location, fault phase and fault time period, four resource operation conditions are set in sequence: no resource access, photovoltaic and hybrid energy storage access, photovoltaic, hybrid energy storage and V2G unit charging, photovoltaic, hybrid energy storage and V2G unit discharging, and control variables for each resource operation condition are configured. Based on the set resource operating conditions and configured control variables, the new power distribution network model is simulated and run, and node parameter and resource parameter data are collected. The feature data collected from the four working conditions were combined into a feature matrix according to a unified feature order, and each feature dimension was normalized. A heat map of high-resistance grounding fault features is generated based on the normalized feature matrix, and a feature radar map of the corresponding operating condition is generated to form a high-resistance grounding fault feature map.

[0028] In this embodiment, a novel distribution network model incorporating photovoltaic (PV), hybrid energy storage, and V2G units is established. Based on the IEEE 33-node distribution system, the model integrates PV, energy storage, and V2G units at multiple trunk and branch nodes, and sets up three-phase voltage, current, and operational quantity measurement modules at each node. The topology diagram is shown below. Figure 1 As shown.

[0029] The main distribution network system in the model consists of nodes 1 to 18, with branches extending from nodes 2, 3, and 6. Node 1 connects to the upstream power source or substation. The rated line voltage of the main power source is 12.66 kV, and the frequency is 50 Hz. The neutral point of the main power source is grounded through a small resistor, providing a zero-sequence current path for single-phase grounding and high-resistance grounding faults. The resource side is connected to the 12.66 kV distribution network through a three-phase double-winding transformer. The rated line voltage on the low-voltage side of the transformer is 0.380 kV, and the connection group adopts a Dyn11 connection method with a delta connection on the high-voltage side, a star connection on the low-voltage side, and a neutral point.

[0030] Photovoltaic (PV) units are connected to nodes 8, 18, 20, 25, 28, 30, and 33, with node 8 connected to two PV units and the other nodes each connected to one PV unit. Energy storage units are connected to nodes 18, 22, 25, and 33. V2G units are connected to nodes 8, 20, 23, and 28. Each PV unit includes a PV array, a boost converter, a DC bus, a three-phase inverter, a filter grid-connected interface, and a control system. The energy storage unit uses a battery-supercapacitor hybrid structure, achieving energy exchange through a bidirectional DC / DC converter, a common DC bus, and a three-phase PWM grid-connected converter. The V2G unit switches between charging and discharging modes via a bidirectional power conversion interface. Measurement modules are installed at each node.

[0031] In this embodiment, when determining the fault scenario of high-resistance grounding due to rainstorm dampness, a phase-to-ground fault is set at node 8 as follows: Figure 2As shown. The fault module is initially in the off state, with phase A and ground selected. The fault connection and disconnection times are 0.05 s and 0.10 s, respectively. The on-resistance Ron is set to 0.001 Ω, the grounding resistance Rg is set to 1000 Ω, and the buffer resistance Rs is set to 1×10⁻⁶ Ω. 6 Ω, and the buffer capacitor Cs is set to infinity. By limiting the fault current with a large grounding resistance, the fault manifests as weak grounding, weak current, and weak voltage drop.

[0032] A high-resistance grounding fault can be equivalently represented as the phase voltage before the fault being connected in series with the high-resistance fault path through the system's equivalent impedance to ground, and the fault phase current is:

[0033] In the formula, I HIF For high-resistance ground fault current, U ph Z is the phase voltage before the fault. eq R is the equivalent impedance to ground from the system to the fault point. f,h Here is the resistance of the high-resistance ground fault path. The active power consumed in the high-resistance fault path is:

[0034] In the formula, P f This represents the active power consumed in the high-resistivity fault path. Equation (2) is used to illustrate that even if the amplitude of the high-resistivity ground fault current is small, the persistent high-resistivity path may still generate a thermal effect.

[0035] like Figure 3 As shown, in this embodiment, the fault is corresponding to the insulation damping process under continuous rainfall: continuous rainfall causes the insulation surface to become damp, the surface resistance decreases, and leakage current accumulates; when a partially conductive channel with a large resistance is formed at a local location, a phase A high-resistance grounding fault occurs at node 8. The high-resistance grounding fault current and the fault channel power are characterized according to equations (1) and (2), respectively.

[0036] (3) Set four resource operating conditions Under the same topology, fault location, fault phase, and fault time period, four resource operation conditions are set in sequence: no resource access, optical-storage access, optical-storage and V2G charging, and optical-storage and V2G discharging.

[0037] To ensure the comparability of fault results under different resource combinations, the four operating conditions adopted the same network topology, fault location, fault phase, fault activation and deactivation time, and measurement configuration, and controlled resource access status only through tp, tb, tvoff, and kv. The four operating conditions and control variables are shown in Table 1.

[0038] Table 1 Resource operating conditions and control variables

[0039] In this embodiment, the model is run and data is collected: The simulation script executes the basic parameter settings, working condition definitions, measurement variable declarations, cyclic simulation, result extraction, plotting, and result saving procedures sequentially. Before each working condition begins, the basic working area variables left over from the previous working condition are cleared, the control variables of the current working condition are written into the basic working area, the model is called to run, and the node quantities and resource quantities are stored in the corresponding result structures.

[0040] The key monitoring points are node 8, the fault location, and its downstream nodes 18, 20, 25, 28, and 33. Node parameters include three-phase voltage and current, and their derived RMS, zero-sequence, and negative-sequence values; resource parameters include the voltage, current, active power, reactive power, and state of charge of photovoltaic, energy storage, and V2G systems. Node 33, located at the far end of the system, is used to characterize the comprehensive impact of a fault at node 8 propagating along the line to the network's end; node 18 is used to assist in comparing the response at the backbone's end.

[0041] The node voltage sag depth is determined by the difference between the pre-fault voltage and the lowest voltage during the fault:

[0042] In the formula, U pre U is the steady-state voltage before the fault. min This is the lowest voltage during the fault duration period.

[0043] To characterize the weak zero-sequence disturbance of a high-resistivity grounding fault relative to normal operating conditions, a zero-sequence sensitivity coefficient is used:

[0044] In the formula, I 0,fault I represents the zero-sequence current amplitude during the fault. 0,pre The zero-sequence background value before the fault is ε, which is a small amount set to prevent the denominator from being zero.

[0045] To characterize the cumulative degree of deviation of negative-sequence components from the normal state within the fault duration interval, a negative-sequence perturbation index is used:

[0046] In the formula, t f and t c These represent the fault initiation and termination times, respectively, where I2(t) is the negative sequence current during the fault period, and I... 2,pre The background value is the negative sequence value before the fault.

[0047] The effective value of phase voltage at node 33 is read and converted to per-unit value according to the phase voltage base value. The steady-state average voltage Upre is calculated during the time period before the fault. The minimum voltage Umin is obtained during the fault duration period, and the voltage drop depth is obtained according to equation (3). Next, the zero-sequence current and negative-sequence current at node 33 are read, and the peak values ​​are extracted respectively during the fault period. The zero-sequence weak disturbance and the negative-sequence cumulative disturbance can be characterized by equations (4) and (5) respectively. Finally, the changes in photovoltaic, energy storage and V2G power are extracted by comparing the deviation of the active power of resources during the fault period from the average power before the fault.

[0048] (5) Normalize the data.

[0049] The feature data of the four working conditions are combined into a feature matrix according to a unified feature order. Each feature dimension is normalized to eliminate the differences in dimensions and orders of magnitude between different feature quantities.

[0050] For the j-th feature quantity of the i-th working condition, normalization is performed in the following manner:

[0051] In the formula, x ij Let x represent the original value of the i-th working condition on the j-th feature. * ij This represents the normalized eigenvalues.

[0052] (6) Construct feature maps.

[0053] A heat map of high-resistance grounding fault features is generated based on the normalized feature matrix, and feature radar maps of four operating conditions are generated using seven features as coordinate axes. The heat map is used to compare the relative strength of individual features under different operating conditions, and the radar map is used to compare the overall outline of each operating condition in the multi-dimensional feature space, thereby forming a high-resistance grounding fault feature map.

[0054] Example 2 This embodiment takes the distribution network under the new resource aggregation of IEEE 33 nodes as the object, sets up a high-resistivity grounding fault caused by rainstorm and moisture in the MATLAB / Simulink environment, performs batch simulation according to four resource operation conditions, extracts key feature quantities and constructs heat map and radar map.

[0055] Specifically, the following steps are included: Step S01: Establish a high-resistivity fault model for distribution networks under the new resource aggregation model.

[0056] like Figure 1As shown, the main branch of the new distribution network consists of nodes 1 to 18, with branches extending from nodes 2, 3, and 6. Photovoltaic power is connected to nodes 8, 18, 20, 25, 28, 30, and 33, with two photovoltaic units connected to node 8 and one unit to each of the other nodes. Energy storage is connected to nodes 18, 22, 25, and 33. V2G is connected to nodes 8, 20, 23, and 28. The fault point is located at node 8, connected in 0.05 s and disconnected in 0.10 s. The conduction resistance is 0.001 Ω, the grounding resistance is 1000 Ω, and the buffer resistance is 1×10⁻⁶. 6 Ω, the buffer capacitance is infinite.

[0057] Step S02: Set four resource operating conditions, run the model cyclically and collect data.

[0058] According to the four resource operation conditions cycle operation model described in Table 1 and the corresponding operation data are collected, with node 33 as the end representative node, the pre-fault voltage, minimum voltage, voltage drop depth, zero-sequence current peak value, negative-sequence current peak value, photovoltaic power change, energy storage power change and V2G power change are extracted from the data of each operation condition.

[0059] The seven spectral features are organized in the following order: voltage drop depth, minimum voltage, zero-sequence current peak value, negative-sequence current peak value, photovoltaic power change, energy storage power change, and V2G power change. The statistical results of the original features for the four operating conditions are shown in Table 2.

[0060] Table 2 Statistical Table of Key Characteristic Quantities of High-Resistance Grounding Faults

[0061] Table 2 shows that when a high-resistivity ground fault occurs, the voltage drop depth at node 33 is only 0.007–0.018 pu, and the minimum voltage remains at 0.961–0.999 pu; the peak value of the zero-sequence current is approximately 0.023–0.024, indicating that although the fault activates the zero-sequence network, the high-resistivity path limits the grounding current. Under the three operating conditions including resources, the peak value of the negative-sequence current is 5.721–5.903, indicating that when both voltage and zero-sequence quantities are weak, the negative-sequence component can still be used to characterize three-phase imbalance. The changes in photovoltaic, energy storage, and V2G power vary depending on the resource access method, which can supplement the representation of the dynamic coupling response between the source, grid, and load.

[0062] Step S03: Form a key feature quantity map.

[0063] The above features are visualized into a map, such as... Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 As shown.

[0064] (1) Node voltage response results Figure 4 The effective phase voltage changes of node 33 under four operating conditions are presented. The four curves rise during the startup phase and gradually enter a steady state. During the 0.05–0.10 s high-resistivity ground fault duration, the curves generally remain at a relatively high voltage level, with only small amplitude shifts and no deep voltage drop as is seen with metallic ground faults. Under the no-resource-access condition, the pre-fault voltage is 0.995 pu, the lowest voltage is 0.988 pu, and the voltage drop depth is only 0.007 pu. Under the photovoltaic-storage-access condition, the pre-fault voltage increases to 1.014 pu, the lowest voltage is 0.999 pu, and the voltage drop depth is 0.015 pu.

[0065] Under both photovoltaic-storage and V2G charging and discharging conditions, the pre-fault voltages at node 33 were 0.978 pu and 0.979 pu, respectively, with a minimum voltage of 0.961 pu in both cases, and a voltage drop depth of approximately 0.018 pu in both cases. The similar node voltage characteristics under both V2G operating modes indicate that in this embodiment, with a 1000 Ω high-resistance channel, the V2G charging and discharging state changes the pre-fault operating point, but does not cause the high-resistance grounding fault to evolve into a significant low-voltage fault. The voltage drop depth under all four conditions did not exceed 0.018 pu, verifying the concealed nature of the high-resistance grounding fault, characterized by "weak voltage disturbance and an apparent normal operating state."

[0066] Figure 5 The voltage curves at node 18 and node 33 show a consistent trend: no significant collapse occurred during the fault period, and the main differences between different resource conditions were in the steady-state voltage level and slight dynamic offset. The combined results of nodes 18 and 33 indicate that relying solely on a low-voltage criterion is insufficient to reliably identify this type of fault; further integration with sequence components and resource power response is necessary.

[0067] (2) Results of zero-sequence and negative-sequence current response Figure 6 The zero-sequence current response at node 33 is presented. After a fault is initiated at 0.05 s, the zero-sequence current in all four operating conditions rises from near zero to approximately 0.023–0.024, and then falls back after the fault is cleared at 0.10 s. The peak zero-sequence current for the no-resource-access and PLG-storage-access conditions is 0.024, while that for the PLG-storage and V2G charging / discharging conditions is approximately 0.023. The small difference in peak values ​​across the conditions indicates that although the zero-sequence network is activated by the high-resistance grounding channel, the 1000 Ω grounding resistance significantly limits the fault current, and the new resource access method does not change the overall weak zero-sequence current characteristic.

[0068] Figure 7The negative sequence current is more sensitive to resource access. The peak negative sequence current in the case without resource access is only 0.247; after photovoltaic and energy storage are connected, the peak increases to 5.903; after adding V2G charging or discharging, the peak values ​​are 5.721 and 5.723, respectively. All three resource-accessed conditions show significant peak values ​​in the initial stage of the fault, followed by oscillating decay, while the peak values ​​of the two V2G modes are similar. This result indicates that even without significant voltage drop and large zero-sequence current, a high-resistivity ground fault can still disrupt the three-phase balance. In this embodiment, the negative sequence component is better able to distinguish between resource-free and resource-accessed conditions than the zero-sequence component, and can serve as an important identification dimension for high-resistivity ground fault maps.

[0069] (3) Power response results of photovoltaic, energy storage and V2G Figure 8 The photovoltaic (PV) active power response is presented. Under the condition of no resource access, the PV power change obtained by the program is 0.496, which can be regarded as the background quantity under the unconnected condition. The PV power changes under the conditions of PV-storage access, PV-storage and V2G charging, and PV-storage and V2G discharging are 995.306, 1401.972, and 1344.331, respectively. The PV power changes in the two conditions including V2G are greater than those in the condition of PV-storage access only, with the charging condition being slightly higher than the discharging condition. This indicates that the operating status of V2G affects the PV grid-connected response through local power balance.

[0070] Figure 9 The active power response of energy storage is presented. The change in energy storage power is 0.245 under the condition of no resource access; it increases to 30168.056 after photovoltaic-energy storage access; and reaches 39009.989 and 38993.588 after adding V2G charging and discharging, respectively. The changes in energy storage power under both V2G-included conditions are higher than those under the condition of photovoltaic-energy storage access only, and the difference between charging and discharging conditions is small. This indicates that energy storage still plays a local power buffering role under low-impedance grounding disturbances and is affected by the source-load state changes caused by V2G operation.

[0071] Figure 10 Comparing V2G charging and discharging conditions, the V2G power change is 1870.966 during charging and 280.494 during discharging, with the former being approximately 6.67 times the latter. This difference indicates that when V2G acts as a charging load, its absorbed power is more sensitive to node voltage and local power flow disturbances; when acting as a discharging power source, its power output is relatively stable. This difference is difficult to discern by observing only node voltage, but incorporating the V2G power change into the graph provides a more intuitive representation of the impact of charging and discharging modes on fault response.

[0072] Step S04: Form a normalized feature matrix and construct a high-resistance grounding fault feature map.

[0073] The seven spectral features of the four operating conditions in Table 2 are normalized column by column according to Equation (6), so that the maximum absolute value of the same feature corresponds to the normalized value 1, and the other operating conditions are mapped according to the relative proportion. The normalization process is used to eliminate the order of magnitude difference between the voltage per unit quantity, sequence current and power change, so that the seven features can be compared in the same spectrum.

[0074] Generate data using four resource conditions as rows and seven normalized features as columns, as shown below. Figure 11 The heatmap shown uses color depth to reflect the relative intensity of various characteristics under different operating conditions. The minimum voltage and zero-sequence current peak values ​​remain at relatively high and similar normalized levels across all four operating conditions, reflecting their limited ability to distinguish resource-dependent operating conditions. The negative-sequence current peak value is significantly lower under resource-free conditions but approaches high values ​​under the three resource-inclusive conditions, highlighting the differences in unbalanced response caused by resource integration. The changes in photovoltaic and energy storage power are significantly enhanced under resource-inclusive conditions, while the changes in V2G power are most prominent under charging conditions. Therefore, the heatmap simultaneously preserves both the common characteristics of high-resistance grounding faults and the differences between various resource-dependent operating conditions.

[0075] Using seven normalized features as coordinate axes, the four operating conditions are connected to form the following: Figure 12 The radar chart shows that the no-resource-connected operating condition shows a significant contraction in both negative-sequence current and photovoltaic power variation dimensions; the photovoltaic-storage connected operating condition shows the most prominent contraction in the negative-sequence dimension; the two operating conditions with V2G show a more expansive performance in the voltage drop and photovoltaic power variation dimensions, with similar overall outlines but still some local differences. The radar chart presents the overall shape of each operating condition in the five-dimensional feature space and can serve as a supplement to the individual comparison results of the heatmap.

[0076] The results from both the heatmap and radar charts indicate that high-resistivity grounding faults cannot be diagnosed solely based on voltage dips or zero-sequence current amplitudes. Minimum voltage and zero-sequence current demonstrate that the fault still possesses grounding characteristics, while negative-sequence current reveals the degree of three-phase imbalance. Changes in photovoltaic, energy storage, and V2G power output characterize the dynamic response on the resource side. Combining these multi-dimensional characteristics allows for a more complete profile of high-resistivity grounding faults under weak voltage and weak zero-sequence conditions.

[0077] Example 3 A novel system for constructing characteristic maps of high-resistivity grounding faults in power distribution networks includes: The new distribution network model construction module is configured to establish a new distribution network model containing photovoltaic, hybrid energy storage and V2G units. The new distribution network model includes multiple nodes, some of which are connected to photovoltaic units, some of which are connected to energy storage units and some of which are connected to V2G units. The rainstorm scenario setting module is configured to treat the high-resistance grounding fault point as equivalent to the phase voltage before the fault being connected in series with the high-resistance fault channel through the system's equivalent impedance to ground, calculate the fault phase current, and determine the fault scenario of rainstorm-induced high-resistance grounding. The resource operation condition setting module is configured to set four resource operation conditions in sequence under the same topology, fault location, fault phase and fault time period: no resource access, photovoltaic and hybrid energy storage access, photovoltaic, hybrid energy storage and V2G unit charging, and photovoltaic, hybrid energy storage and V2G unit discharging. The control variables for each resource operation condition are configured. The simulation operation module is configured to perform simulation operation of the new power distribution network model based on the set resource operating conditions and configured control variables, and to collect node parameter and resource parameter data. The normalization processing module is configured to form a feature matrix from the feature data collected under the four working conditions according to a uniform feature order, and to perform normalization processing on each feature dimension. The fault feature map generation module is configured to generate a high-resistance grounding fault feature heat map based on the normalized feature matrix, and generate a feature radar map of the corresponding operating condition, thus forming a high-resistance grounding fault feature map.

[0078] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of one or more computer-usable storage media (including, but not limited to, disk storage, etc.) containing computer-usable program code. CD - ROM It takes the form of a computer program product implemented on (such as optical memory, etc.).

[0079] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0080] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0081] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A novel method for constructing a characteristic map of high-resistivity grounding faults in distribution networks, characterized in that, Includes the following steps: A novel distribution network model incorporating photovoltaic, hybrid energy storage, and V2G units is established. The novel distribution network model includes multiple nodes, with some nodes connected to photovoltaic units, some nodes connected to energy storage units, and some nodes connected to V2G units. The high-resistance grounding fault point is equivalent to the phase voltage before the fault being connected in series with the high-resistance fault path through the system's equivalent impedance to ground. The fault phase current is calculated to determine the fault scenario of high-resistance grounding caused by rainstorm and moisture. Under the same topology, fault location, fault phase and fault time period, four resource operation conditions are set in sequence: no resource access, photovoltaic and hybrid energy storage access, photovoltaic, hybrid energy storage and V2G unit charging, photovoltaic, hybrid energy storage and V2G unit discharging, and control variables for each resource operation condition are configured. Based on the set resource operating conditions and configured control variables, the new power distribution network model is simulated and run, and node parameter and resource parameter data are collected. The feature data collected from the four working conditions were combined into a feature matrix according to a unified feature order, and each feature dimension was normalized. A heat map of high-resistance grounding fault features is generated based on the normalized feature matrix, and a feature radar map of the corresponding operating condition is generated to form a high-resistance grounding fault feature map.

2. The novel method for constructing a characteristic map of high-resistivity grounding faults in a distribution network as described in claim 1, characterized in that, The process of establishing a new distribution network model that includes photovoltaic, hybrid energy storage and V2G units includes: based on the distribution system, connecting photovoltaic, hybrid energy storage and V2G units to multiple main nodes and branch nodes, and setting up three-phase voltage, current and operation quantity measurement modules at each node; The main trunk of the new distribution network model includes multiple nodes, with some nodes branching out to other nodes. One node connects to the upstream power source or substation. The neutral point of the main power source is grounded through a small resistor, providing a zero-sequence current path for single-phase grounding and high-resistance grounding faults. The resource side is connected to the distribution network through a three-phase double-winding transformer. The rated line voltage of the main power source and the rated line voltage of the low-voltage side of the transformer are set. The connection group adopts the Dyn11 connection method with high-voltage side delta and low-voltage side star, and the neutral point is led out.

3. The novel method for constructing a characteristic map of high-resistivity grounding faults in a distribution network as described in claim 1, characterized in that, The process of connecting some nodes to photovoltaic units, some nodes to energy storage units, and some nodes to V2G units includes: at least one node connecting to two photovoltaic units, and each of the other photovoltaic nodes connecting to one unit; the hybrid energy storage unit adopts a hybrid structure of batteries and supercapacitors, and realizes energy exchange through a bidirectional DC / DC converter, a common DC bus, and a three-phase PWM grid-connected converter; the V2G unit realizes the switching between charging and discharging modes through a bidirectional power conversion interface, and each node is equipped with a measurement module.

4. The novel method for constructing a characteristic map of high-resistivity grounding faults in a distribution network as described in claim 1, characterized in that, The process of equating a high-resistance grounding fault point with the phase voltage before the fault is connected in series with the high-resistance fault path through the system's equivalent impedance to ground, and calculating the fault phase current includes: setting each phase to ground fault, limiting the fault current by configuring a grounding resistance greater than the set value, so that the fault manifests as weak grounding, weak current and weak voltage drop. A high-resistance grounding fault point is equivalent to the phase voltage before the fault being connected in series with the high-resistance fault path through the system's equivalent impedance to ground. The fault phase current is calculated, and then the active power consumed in the high-resistance fault path is calculated.

5. The novel method for constructing a characteristic map of high-resistivity grounding faults in a distribution network as described in claim 1, characterized in that, The process of determining the fault scenario of high-resistance grounding due to rainstorm moisture includes: classifying the fault as the insulation moisture process under continuous rainfall: continuous rainfall causes the insulation surface to become damp, the surface resistance decreases, and leakage current accumulates; when an incomplete conductive path with a large resistance is formed at a local location, a high-resistance grounding fault occurs at the corresponding node.

6. The novel method for constructing a characteristic map of high-resistivity grounding faults in a distribution network as described in claim 1, characterized in that, The process of sequentially setting four resource operation conditions includes: no resource access, photovoltaic and hybrid energy storage access, photovoltaic, hybrid energy storage and V2G unit charging, and photovoltaic, hybrid energy storage and V2G unit discharging. The four resource operation conditions adopt the same network topology, fault location, fault phase, fault activation and deactivation time, and measurement configuration, and the resource access status is controlled only by tp, tb, tvoff and kv.

7. The novel method for constructing a characteristic map of high-resistivity grounding faults in a distribution network as described in claim 1, characterized in that, Based on the set resource operating conditions and configured control variables, the simulation operation of the new power distribution network model is carried out. The process of collecting node parameter and resource parameter data includes: running the pre-built simulation script, sequentially executing the basic parameter setting, operating condition definition, measurement variable declaration, cyclic simulation, result extraction, plotting and result saving procedures. Before each operating condition starts, the basic working area variables left over from the previous operating condition are cleared, the control variables of the current operating condition are written into the basic working area, the model is called to run, and the node quantities and resource quantities are stored in the corresponding result structure.

8. The novel method for constructing a characteristic map of high-resistivity grounding faults in a distribution network as described in claim 1, characterized in that, Based on the set resource operating conditions and configured control variables, the simulation operation of the new distribution network model is carried out. The process of collecting node parameters and resource parameter data includes: focusing on monitoring the fault point node and downstream nodes. Node quantities include three-phase voltage, current and the effective values, zero-sequence quantities and negative-sequence quantities obtained from them; resource quantities include the voltage, current, active power, reactive power of photovoltaic, energy storage and V2G and the state of charge of energy storage. The node voltage drop depth is calculated according to the difference between the voltage before the fault and the lowest voltage during the fault. The zero-sequence sensitivity coefficient is used to characterize the weak zero-sequence disturbance of high-resistance grounding fault relative to normal operating conditions. The negative-sequence disturbance index is used to characterize the cumulative degree of negative-sequence component deviation from the normal state within the fault duration interval. By comparing the deviation of resource active power during the fault period from the average power before the fault, the power changes of photovoltaic, energy storage and V2G are extracted.

9. The novel method for constructing a characteristic map of high-resistivity grounding faults in a distribution network as described in claim 1, characterized in that, The process of generating a high-resistance grounding fault feature heatmap based on the normalized feature matrix and generating a feature radar map of the corresponding operating conditions to form a high-resistance grounding fault feature spectrum includes: generating a high-resistance grounding fault feature heatmap based on the normalized feature matrix, and generating feature radar maps of four resource operating conditions with each feature as the coordinate axis; using the heatmap to compare the relative strength of individual features under different operating conditions, and using the radar map to compare the overall contour of each operating condition in the multi-dimensional feature space, thereby forming a high-resistance grounding fault feature spectrum.

10. A novel system for constructing characteristic maps of high-resistivity grounding faults in power distribution networks, characterized in that... include: The new distribution network model construction module is configured to establish a new distribution network model containing photovoltaic, hybrid energy storage and V2G units. The new distribution network model includes multiple nodes, some of which are connected to photovoltaic units, some of which are connected to energy storage units and some of which are connected to V2G units. The rainstorm scenario setting module is configured to treat the high-resistance grounding fault point as equivalent to the phase voltage before the fault being connected in series with the high-resistance fault channel through the system's equivalent impedance to ground, calculate the fault phase current, and determine the fault scenario of rainstorm-induced high-resistance grounding. The resource operation condition setting module is configured to set four resource operation conditions in sequence under the same topology, fault location, fault phase and fault time period: no resource access, photovoltaic and hybrid energy storage access, photovoltaic, hybrid energy storage and V2G unit charging, and photovoltaic, hybrid energy storage and V2G unit discharging. The control variables for each resource operation condition are configured. The simulation operation module is configured to perform simulation operation of the new power distribution network model based on the set resource operating conditions and configured control variables, and to collect node parameter and resource parameter data. The normalization processing module is configured to form a feature matrix from the feature data collected under the four working conditions according to a uniform feature order, and to perform normalization processing on each feature dimension. The fault feature map generation module is configured to generate a high-resistance grounding fault feature heat map based on the normalized feature matrix, and generate a feature radar map of the corresponding operating condition, thus forming a high-resistance grounding fault feature map.

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