Method, device and equipment for protecting ac-dc distribution network from faults and storage medium

Abstract

The application discloses a kind of AC-DC distribution network fault protection method, device, equipment and storage medium, the method includes the real-time current of protection measuring point, the protection measuring point is located on the line to be measured, extract the high-frequency current component of the switching frequency corresponding to the real-time current, and according to the ratio of the high-frequency current component and the current total value of the real-time current, determine whether to start the protection action for the protection measuring point, the current total value is the size of the current flowing through the protection measuring point.The embodiment of the application judges whether the line is faulty by the ratio of the high-frequency current component of the protection measuring point and the current total value, uses the characteristic that the ratio monotonically attenuates with the fault distance, can find the fault position in time and make the line to be measured produce protection action, realizes single-ended protection, without opposite side data, action speed is fast, has good transition resistance capacity.

Description

Technical Field

[0001] This invention relates to the field of power distribution network fault detection technology, and in particular to a method, apparatus, equipment and storage medium for AC / DC power distribution network fault protection. Background Technology

[0002] In recent years, with the development of clean energy, the proportion of DC power sources such as photovoltaics and energy storage, as well as DC loads, in power systems has been continuously increasing, and the scale of AC / DC hybrid power grids has been expanding. Power-Electronic Transformers (PETs) can connect AC / DC power sources and DC loads, flexibly control power, and reduce size and cost, making them an important component of AC / DC distribution networks. When any line in the distribution network fails, due to the wide distribution of power sources, both the PET and the converter inject current into the fault point. The fault current rises rapidly and has a large amplitude. Power electronic devices cannot withstand the fault current for a long time, so it is necessary to select and disconnect the faulty circuit in a very short time.

[0003] Currently, protection methods for AC / DC distribution networks primarily target Voltage Source Converter (VSC) and Modular Multilevel Converter (MMC) type networks, and can be categorized into longitudinal protection and single-ended quantity protection. Longitudinal protection relies on communication measurements and requires high synchronization. Single-ended quantity protection mainly employs the differential undervoltage protection method. Related research indicates that differential undervoltage protection has insufficient sensitivity and weak tolerance to transition resistance. Therefore, a fast and reliable fault protection method suitable for AC / DC distribution networks is urgently needed. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a method, apparatus, device and storage medium for fault protection of AC / DC distribution networks, in order to solve the technical problem of weak tolerance to transition resistance in single-ended quantity protection schemes of AC / DC distribution networks.

[0005] The technical solution proposed in this invention is as follows:

[0006] The first aspect of this invention provides a fault protection method for AC / DC distribution networks, comprising: acquiring the real-time current of a protection measuring point located on the line under test; extracting the high-frequency current component of the switching frequency corresponding to the real-time current; and determining whether to initiate a protection action for the protection measuring point based on the ratio of the high-frequency current component to the total current value of the real-time current, wherein the total current value is the magnitude of the current flowing through the protection measuring point.

[0007] Optionally, determining whether to activate the protection action for the protection measuring point based on the ratio of the high-frequency current component to the total value of the real-time current includes: comparing the ratio with a first setting value; if the ratio is greater than the first setting value, then activating the protection action corresponding to the protection measuring point; if the ratio is less than the first setting value, then not activating the protection action.

[0008] Optionally, determining whether to activate the protection action for the protection measuring point based on the ratio of the high-frequency current component to the total value of the real-time current includes: comparing the ratio with a first setting value and the relationship between the ratio and a second setting value, wherein the second setting value is less than the first setting value; if the ratio is greater than the first setting value, then activating the protection action corresponding to the protection measuring point; if the ratio is less than the first setting value but greater than the second setting value, then performing a re-detection after a preset delay time; if the ratio is less than the second setting value, then not activating the protection action.

[0009] Optionally, the step of re-detecting after a preset delay time includes: after the preset delay time, comparing the ratio with the second setting value; if the ratio is greater than the second setting value, then activating the protection action corresponding to the protection measuring point; if the ratio is less than the second setting value, then not activating the protection action.

[0010] Optionally, the magnitude of the first setting value is:

[0011] ρ set I =K I rel ρ I

[0012] in, The first set value, ρ is the first reliability coefficient. I The minimum value of the ratio of the high-frequency current component to the total current value when a metallic fault occurs in the circuit under test;

[0013] The value of the second setting is:

[0014] ρ set II =K II rel ρ II

[0015] in, The first set value, ρ is the second reliability coefficient. IIThe minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit and the next-level circuit of the tested circuit.

[0016] Optionally, the minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit is: the ratio of the high-frequency current component to the total current when a metallic short circuit occurs at the end of the tested circuit; the minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit and the next-level circuit of the tested circuit is: the ratio of the high-frequency current component to the total current when a metallic short circuit occurs at the end of the next-level circuit of the tested circuit to the total current when a metallic short circuit occurs at the end of the tested circuit.

[0017] Optionally, before extracting the high-frequency current component of the switching frequency corresponding to the real-time current, the method further includes: determining whether the protection start-up conditions are met based on the real-time current; if the real-time current meets the protection start-up conditions, then extracting the high-frequency current component of the switching frequency corresponding to the real-time current; if the real-time current does not meet the protection start-up conditions, then no action is taken.

[0018] Optionally, determining whether the protection start condition is met based on the real-time current includes: continuously acquiring the real-time current at intervals and calculating the sum of the sudden changes of a number of consecutive real-time currents; if the sum of the sudden changes is detected to be greater than the current protection threshold, then the real-time current meets the protection start condition, wherein the sudden change is the difference between the currently detected real-time current and the previously detected real-time current.

[0019] Optionally, the AC / DC distribution network is an AC / DC distribution network that includes power electronic transformers.

[0020] A second aspect of the present invention provides an AC / DC distribution network fault protection device, comprising:

[0021] The acquisition module is used to acquire the real-time current of the protection measuring point, which is located on the line under test; the extraction module is used to extract the high-frequency current component of the switching frequency corresponding to the real-time current; and the protection module is used to determine whether to activate the protection action for the protection measuring point based on the ratio of the high-frequency current component to the total current value of the real-time current.

[0022] Optionally, the protection module includes: a first comparison submodule, used to compare the ratio and the first setting value; and a first action submodule, used to activate the protection action corresponding to the protection measurement point when the ratio is greater than the first setting value, and not activate the protection action when the ratio is less than the first setting value.

[0023] Optionally, the protection module includes: a second comparison submodule, used to compare the ratio and the first setting value, as well as the relationship between the ratio and the second setting value, wherein the second setting value is less than the first setting value; and a second action submodule, used to activate the protection action corresponding to the protection measurement point when the ratio is greater than the first setting value, to perform a re-detection after a preset delay time when the ratio is less than the first setting value and greater than the second setting value, and to not activate the protection action when the ratio is less than the second setting value.

[0024] Optionally, the second action submodule includes: a third comparison submodule, used to compare the ratio and the second setting value after a preset delay time; and a third action submodule, used to activate the protection action corresponding to the protection measuring point when the ratio is greater than the second setting value, and not activate the protection action when the ratio is less than the second setting value.

[0025] Optionally, the AC / DC distribution network fault protection device further includes: a start-up judgment module, used to determine whether the protection start-up conditions are met based on the real-time current; if the real-time current meets the protection start-up conditions, the high-frequency current component of the switching frequency corresponding to the real-time current is extracted; if the real-time current does not meet the protection start-up conditions, no action is taken.

[0026] Optionally, the start-up judgment module includes: a judgment submodule, used to continuously acquire the real-time current at intervals and calculate the sum of the sudden changes of several consecutive real-time currents; if the sum of the sudden changes is detected to be greater than the current protection threshold, then the real-time current meets the protection start-up condition, wherein the sudden change is the difference between the currently detected real-time current and the previously detected real-time current.

[0027] A third aspect of the present invention provides an electronic device, including: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the AC / DC distribution network fault protection method as described in any of the first aspects of the present invention.

[0028] A fourth aspect of the present invention provides a computer-readable storage medium storing computer instructions for causing the computer to perform the AC / DC distribution network fault protection method as described in any of the first aspects of the present invention.

[0029] As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages:

[0030] This invention provides a method, apparatus, device, and storage medium for fault protection in AC / DC distribution networks. It acquires the real-time current at a protection measuring point located on the line under test, extracts the high-frequency current component corresponding to the switching frequency of the real-time current, and determines whether to initiate protection action for the protection measuring point based on the ratio of the high-frequency current component to the total current value of the real-time current. The total current value is the magnitude of the current flowing through the protection measuring point. This invention determines whether a line fault has occurred by using the ratio of the high-frequency current component at the protection measuring point to the total current value. Utilizing the characteristic that this ratio monotonically decreases with fault distance, it can promptly detect the fault location and trigger protection action on the line under test, achieving single-end quantity protection, requiring no data from the opposite side, with fast action speed and good resistance tolerance. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart of the AC / DC distribution network fault protection method in an embodiment of the present invention;

[0033] Figure 2 This is a flowchart of another AC / DC distribution network fault protection method in an embodiment of the present invention;

[0034] Figure 3 This is a topology diagram of the AC / DC distribution network in an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram illustrating the protection criteria when a metallic bipolar short circuit occurs at different locations on the main line l in an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram illustrating the protection criteria when a bipolar short circuit occurs at different locations on the main line l via a 5Ω transition resistor, as shown in this embodiment of the invention.

[0037] Figure 6 This is a schematic diagram of the protection criteria when a metallic bipolar short circuit occurs at different locations on branch line l1 in an embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram illustrating the protection criteria when a bipolar short circuit occurs at different locations on branch line l1 via a 5Ω transition resistor, as shown in this embodiment of the invention.

[0039] Figure 8 This is a block diagram of the AC / DC distribution network fault protection device in an embodiment of the present invention;

[0040] Figure 9 This is a schematic diagram of the structure of the electronic device in an embodiment of the present invention;

[0041] Figure 10 This is a schematic diagram of the structure of a computer-readable storage medium in an embodiment of the present invention. Detailed Implementation

[0042] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] This invention provides a fault protection method for AC / DC distribution networks, such as... Figure 1 As shown, the fault protection methods for AC / DC distribution networks include:

[0044] Step S100: Obtain the real-time current of the protection measuring point, which is located on the line under test. For example, Figure 3 This diagram illustrates an exemplary AC / DC distribution network topology, including a power electronic transformer (PET) with a high-frequency isolation stage. The PET contains an input rectifier and a dual active bridge converter (DAB), providing medium-voltage AC and low-voltage DC ports. AC power is connected to the PET via the transformer. After input-stage rectification and voltage level transformation by the DAB, it is converted to 750V low-voltage DC, which is then connected to the low-voltage DC bus (i.e., branch lines) via the main line. Distributed energy sources such as photovoltaic (PV) and battery energy storage systems (BESS) are connected to the low-voltage DC bus via the DAB. The tested lines include the main line and three branch lines. The main line has protection test points 1 and 2 at both ends, and each branch line has protection test points 3, 4, 5, 6, and 7 at both ends. Real-time current is continuously monitored and acquired at each protection test point, and this real-time current is used as the basis for fault diagnosis.

[0045] Step S200: Extract the high-frequency current component corresponding to the switching frequency of the real-time current. Specifically, the switching frequency is the switching frequency of the corresponding electronic switching device on the circuit under test, for example... Figure 3The switching frequency corresponding to the real-time current detected by the protection measuring points on the main line is the switching frequency of the insulated-gate bipolar transistor (IGBT) in the dual active bridge converter (DAB) of the power electronic transformer (PET). The switching frequency corresponding to the real-time current detected by the protection measuring points on the branch lines is the switching frequency of the IGBT in the DC / DC converter of their respective branch lines. After obtaining the real-time current of each protection measuring point, the high-frequency component of the fault current is extracted using discrete Fourier transform. The frequency of the high-frequency component of the fault current is the corresponding switching frequency.

[0046] Step S300: Determine whether to activate the protection action for the protected measuring point based on the ratio of the high-frequency current component to the total real-time current. The total current is the magnitude of the current flowing through the protected measuring point. Based on dispersion theory, the attenuation of high-frequency energy along the line is greater than that of the total current. Therefore, the ratio of the high-frequency current component to the total current decreases monotonically with the fault distance. This single-ended protection criterion can be used to determine the fault location. For example, if the ratio is greater than a set threshold, it indicates that the fault location is close to the protected measuring point, thus activating the protection action of the protected measuring point. The protection action is generated by the DC circuit breaker or load switch on the tested line. The DC circuit breaker or load switch can control the on / off of the current on the corresponding tested line. Therefore, the activation of the protection action can be selected by controlling the DC circuit breaker or load switch. The ratio of the high-frequency current component to the total current does not change much when a metallic short circuit or a transition resistance short circuit occurs on the line. Therefore, it has good resistance to transition resistance. Moreover, only data from a single protected measuring point is needed to obtain the judgment result, without requiring data from other measuring points or the opposite side of the protection equipment, resulting in fast action speed.

[0047] This invention provides a fault protection method for AC / DC distribution networks. By acquiring the real-time current at a protection measuring point located on the tested line, the high-frequency current component corresponding to the switching frequency of the real-time current is extracted. The method determines whether to initiate protection action for the protection measuring point based on the ratio of the high-frequency current component to the total real-time current. The total current is the magnitude of the current flowing through the protection measuring point. This invention determines whether a line fault has occurred by using the ratio of the high-frequency current component at the protection measuring point to the total current. Utilizing the characteristic that this ratio monotonically decreases with fault distance, the fault location can be detected promptly, triggering protection action on the tested line. This achieves single-ended protection, requires no data from the opposite side, has fast action speed, and exhibits good resistance tolerance to transition resistance.

[0048] In one embodiment, determining whether to initiate a protection action for the protected measuring point based on the ratio of the high-frequency current component to the total real-time current includes:

[0049] Step S310: Compare the magnitude of the ratio and the first setpoint.

[0050] Step S311: If the ratio is greater than the first setting value, then activate the protection action corresponding to the protection measuring point.

[0051] Step S312: If the ratio is less than the first setting value, the protection action will not be initiated.

[0052] Specifically, the first setting value is the protection activation threshold for a protection segment on the tested line. This segment protection can quickly disconnect the current in the tested circuit when a short-circuit fault occurs. At least one protection testing point is set on each tested line with a protection segment, for example... Figure 3 In this embodiment of the invention, only one protection segment is configured for protection measurement points 2, 3, 5, and 6. Steps S310-S311 are the protection control logic when only one protection segment is configured.

[0053] Specifically, the magnitude of the first setpoint is:

[0054] ρ set I =K I rel ρ I

[0055] in, This is the first setpoint value. ρ is the first reliability coefficient. I This refers to the minimum ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested line. Specifically, due to the attenuation characteristics of high-frequency energy along the line, the minimum value generally occurs at the end of the protected line. Therefore, the minimum ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested line is: the ratio of the high-frequency current component to the total current when a metallic short circuit occurs at the end of the tested line.

[0056] In one embodiment, determining whether to initiate a protection action for the protected measuring point based on the ratio of the high-frequency current component to the total real-time current includes:

[0057] Step S320: Compare the ratio and the first setpoint, as well as the relationship between the ratio and the second setpoint, where the second setpoint is less than the first setpoint.

[0058] Step S321: If the ratio is greater than the first setting value, then activate the protection action corresponding to the protection measuring point.

[0059] Step S322: If the ratio is less than the first set value and greater than the second set value, then perform a second test after a preset delay time.

[0060] Step S323: If the ratio is less than the second setting value, the protection action will not be initiated.

[0061] Specifically, the first setting value is the protection activation threshold for setting a single-stage protection on the tested line, and the second setting value is the protection activation threshold for setting a double-stage protection on the tested line. Single-stage protection can quickly disconnect the current in the tested circuit when a short-circuit fault occurs, while double-stage protection can disconnect the current in the tested circuit when the current remains abnormal. Specifically, if the tested line is a main line or a branch line with distributed energy sources such as photovoltaics or energy storage, then two protection testing points are configured on the tested line. One protection testing point is configured with only single-stage protection, while the other protection testing point is configured with both single-stage and double-stage protection. For example... Figure 3 In this embodiment of the invention, steps S320-S323 are the protection control logic when both first-stage and second-stage protection are configured.

[0062] In one embodiment, performing a second detection after a preset delay time includes:

[0063] Step S3221: After a preset delay time, compare the ratio and the relationship between the second setpoint value.

[0064] Step S3222: If the ratio is greater than the second setting value, then activate the protection action corresponding to the protection measuring point.

[0065] Step S32223: If the ratio is less than the second setting value, the protection action will not be initiated.

[0066] Specifically, the preset delay time can be understood as the waiting time for the protection devices at other protection points to operate. The preset delay time can be set to 13ms, 15ms, etc. If other protection points trigger a first-stage protection within the preset time, the current will be immediately disconnected. When the protection point configured for second-stage protection detects again, the ratio is less than the second setting value, so the protection action is not initiated. However, if other detection points do not trigger a first-stage protection, the abnormal current will continue. At this time, the protection device corresponding to the protection point whose ratio exceeds the second setting value set for second-stage protection will initiate the protection action to prevent the current from continuing to be abnormal. This embodiment of the invention can determine whether to disconnect the current on the tested line based on the second setting value after the preset delay time, thereby improving the reliability of protection.

[0067] This invention, through setting a protection logic based on a first setting value at the protection measurement point, can quickly disconnect the current on the tested line where the fault occurs. If the protection action on other lines cannot be generated in time, it can also re-determine whether to disconnect the current on the tested line based on a second setting value after a preset delay time, thereby improving the reliability of protection.

[0068] In one embodiment, the magnitude of the first setpoint is:

[0069] ρ set I =K I rel ρ I

[0070] in, This is the first setpoint value. ρ is the first reliability coefficient. I This is the minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the circuit under test.

[0071] The magnitude of the second setting value is:

[0072] ρ set II =K II rel ρ II

[0073] in, This is the first setpoint value. ρ is the second reliability coefficient. II It is the minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit and the next level circuit of the tested circuit.

[0074] In one embodiment, the minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit is the ratio of the high-frequency current component to the total current when a metallic short circuit occurs at the end of the tested circuit. Therefore, the minimum value ρ in the first setting is... I The calculation formula is:

[0075]

[0076] In the formula, i(k) is the total current measured when a metallic short circuit occurs at the end of the tested circuit. d I (k) represents the high-frequency current component of the metallic short-circuit protection at the end of the line under test.

[0077] The minimum ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit and its next-level circuit is: the ratio of the high-frequency current component when a metallic short circuit occurs at the end of the next-level circuit to the total current when a metallic short circuit occurs at the end of the tested circuit.

[0078] Therefore, the minimum value ρ in the second tuning value II The calculation formula is:

[0079]

[0080] In the formula, i(k) is the total current measured when a metallic short circuit occurs at the end of the tested line. d II (k) represents the high-frequency current component when a metallic short circuit occurs at the end of the next-level line.

[0081] Based on the line-of-sight attenuation characteristics of high-frequency energy, the embodiments of the present invention can reasonably and quickly determine the first setting value and the second setting value.

[0082] In one embodiment, before extracting the high-frequency current component of the switching frequency corresponding to the real-time current, the method further includes: determining whether the protection start-up conditions are met based on the real-time current; if the real-time current meets the protection start-up conditions, then extracting the high-frequency current component of the switching frequency corresponding to the real-time current; if the real-time current does not meet the protection start-up conditions, then no action is taken. By setting protection start-up conditions, the high-frequency current component of the switching frequency corresponding to the real-time current is extracted and subsequent fault judgment is performed only when the protection start-up conditions are met, avoiding frequent extraction and calculation and reducing resource waste.

[0083] In one embodiment, determining whether the protection start-up conditions are met based on the real-time current includes:

[0084] The system continuously acquires real-time current at intervals and calculates the sum of a series of sudden changes in real-time current. If the sum of the sudden changes is greater than the current protection threshold, the real-time current meets the protection start-up condition. Here, the sudden change is the difference between the currently detected real-time current and the previously detected real-time current.

[0085] Specifically, the formula for determining whether the sum of the sudden changes is greater than the current protection threshold is:

[0086]

[0087] In the formula: ΔI(j) is the sudden change, K is the current reliability coefficient, and I N The rated current of the tested line is N, and the number of sampling points is N, which is the number of consecutive real-time current abrupt changes. For example, when N is 3, the protection activation condition is met when the sum of three consecutive real-time current abrupt changes exceeds the current protection threshold. This embodiment of the invention uses the abrupt changes from multiple sampling points as the basis for judgment, which is reasonable and has high accuracy.

[0088] In one embodiment, the AC / DC distribution network is an AC / DC distribution network that includes power electronic transformers.

[0089] The following is combined Figure 3 The topology diagram illustrates the working process of this embodiment of the invention. The AC / DC distribution network includes a high-frequency isolation stage power electronic transformer (PET). The power electronic transformer (PET) includes an input stage rectifier and a dual active bridge converter (DAB), providing a medium-voltage AC port and a low-voltage DC port.

[0090] In specific simulations, such as Figure 2 As shown, data from 1ms before and after the fault are selected. The ratio of the high-frequency current component to the total real-time current is calculated. If the ratio is greater than the first setting value, the protection stage 1 criterion is met, and the protection quickly trips to disconnect the faulty line. If the ratio is less than the first setting value but greater than the second setting value, only the second-stage protection criterion is met. After a delay of Δt = 13ms, the protection is re-evaluated. If the overcurrent still exists, the protection trips to disconnect the fault; otherwise, the protection returns to normal.

[0091] Taking a metallic short-circuit fault occurring at the midpoint of main line l as an example, the protection operation is explained, and the simulation results are as follows: Figure 4 As shown. When the fault occurs at the midpoint of line l, the power electronic transformer (PET) and the energy storage converter (DC / DC) inject high-frequency current into the grid. When protection measuring points 1 and 2 detect a sudden change in current that meets the activation criteria, the fault discrimination is initiated. At this time, the fault is located within a certain range. The ratio of the high-frequency current component calculated by protection measuring points 1 and 2 to the total real-time current is greater than the first setting value. Protection measuring points 1 and 2 act quickly to isolate the fault. The sudden changes in current at protection measuring points 3, 5, and 6 do not meet the activation criteria, so the protection does not act. Although protection measuring points 4 and 7 can also activate the protection, the ratio of the calculated high-frequency current component to the total real-time current only meets the second-stage protection requirement, i.e., less than the first setting value and greater than the second setting value. Moreover, the fault has already been quickly cleared by protection measuring points 1 and 2. Therefore, after a delay of Δt, the protection resets.

[0092] If the main line l is short-circuited through a 5Ω transition resistor, the simulation results are as follows: Figure 5 As shown, the high-frequency energy ratio does not change much with the metallic short circuit, and one section still has a protection range of more than 50%, indicating that the protection has good resistance to transition resistance.

[0093] like Figure 6 As shown, a ratio criterion is used because the branch line is the final stage line, so one protection stage can protect the entire length of the tested line. The following example, a fault at the midpoint of branch line l1, illustrates the protection operation. When the fault occurs at the midpoint of the downstream feeder of the bus, the power electronic transformer (PET) and the energy storage converter (DC / DC) inject high-frequency current into the grid. Protection measuring points 3 and 4 detect a current surge that meets the activation criterion, and the protection is activated. At this time, the fault is located within a certain range, and the ratio calculated by the measuring points is greater than the first setting value. Protection measuring points 3 and 4 quickly activate, isolating the fault. Protection measuring points 5 and 6 do not meet the current surge activation criterion, and the protection does not activate. Although protection measuring points 1 and 7 can also activate the protection, the ratio of the calculated high-frequency current component to the total real-time current only meets the second-stage protection requirement, i.e., less than the first setting value and greater than the second setting value. Furthermore, the fault has already been quickly cleared by protections 3 and 4, so after a delay of Δt, the protection resets.

[0094] If branch line l1 is short-circuited through a 5Ω transition resistor, the simulation results are as follows: Figure 7 As shown, the high-frequency energy ratio does not change much with the metallic short circuit at this time, and the protection range of a branch line section is still more than 90%, indicating that the protection of the high-frequency ratio criterion has good resistance to transition resistance.

[0095] This invention also provides an AC / DC distribution network fault protection device, such as... Figure 8 As shown, the AC / DC distribution network fault protection device includes:

[0096] The acquisition module 801 is used to acquire the real-time current of the protection measuring point, which is located on the line under test. Specific details can be understood by referring to the relevant descriptions and effects in the above method embodiments, and will not be repeated here.

[0097] The extraction module 802 is used to extract the high-frequency current component corresponding to the switching frequency of the real-time current; specific details can be understood by referring to the relevant descriptions and effects in the above method embodiments, and will not be repeated here.

[0098] The protection module 803 is used to determine whether to activate the protection action for the protected measuring point based on the ratio of the high-frequency current component to the total real-time current. Specific details can be understood by referring to the relevant descriptions and effects in the above method embodiments, and will not be repeated here.

[0099] Optionally, the protection module 803 includes:

[0100] The first comparison submodule is used to compare the size relationship between the ratio and the first setpoint value.

[0101] The first action submodule is used to activate the protection action corresponding to the protection measurement point when the ratio is greater than the first setting value, and not activate the protection action when the ratio is less than the first setting value.

[0102] Optionally, the protection module 803 includes:

[0103] The second comparison submodule is used to compare the ratio and the first setpoint, as well as the relationship between the ratio and the second setpoint, wherein the second setpoint is less than the first setpoint.

[0104] The second action submodule is used to activate the protection action corresponding to the protection measurement point when the ratio is greater than the first setting value. When the ratio is less than the first setting value but greater than the second setting value, it will be re-detected after a preset delay time. When the ratio is less than the second setting value, the protection action will not be activated.

[0105] Optionally, the second action submodule includes:

[0106] The third comparison submodule is used to compare the ratio and the second setpoint value after a preset delay time.

[0107] The third action submodule is used to activate the protection action corresponding to the protection measurement point when the ratio is greater than the second setting value, and not to activate the protection action when the ratio is less than the second setting value.

[0108] Optionally, AC / DC distribution network fault protection devices may also include:

[0109] The start-up judgment module is used to determine whether the protection start-up conditions are met based on the real-time current. If the real-time current meets the protection start-up conditions, the high-frequency current component of the switching frequency corresponding to the real-time current is extracted. If the real-time current does not meet the protection start-up conditions, no action is taken.

[0110] Optionally, the startup judgment module includes:

[0111] The determination submodule is used to continuously acquire real-time current at intervals and calculate the sum of the sudden changes of several consecutive real-time currents. If the sum of the sudden changes is greater than the current protection threshold, the real-time current meets the protection start condition. The sudden change is the difference between the currently detected real-time current and the previously detected real-time current.

[0112] This invention provides an AC / DC distribution network fault protection device. It acquires the real-time current at a protection measuring point located on the tested line, extracts the high-frequency current component corresponding to the switching frequency of the real-time current, and determines whether to initiate protection action for the measuring point based on the ratio of the high-frequency current component to the total real-time current. The total current is the magnitude of the current flowing through the measuring point. This invention determines whether a line fault has occurred by using the ratio of the high-frequency current component at the protection measuring point to the total current. This ratio monotonically decreases with fault distance, enabling timely fault location detection and triggering protection action on the tested line. It achieves single-ended protection, requires no data from the opposite side, has fast action speed, and good resistance to transition resistance.

[0113] This invention also provides an electronic device, such as... Figure 9As shown, the system includes a memory 501 and a processor 502, which are interconnected. The memory 501 stores computer instructions, and the processor 502 executes these computer instructions to perform the AC / DC power distribution network fault protection method described in the above embodiments of the present invention. The processor 502 and the memory 501 can be connected via a bus or other means. The processor 502 can be a central processing unit (CPU). The processor 502 can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations thereof. The memory 501, as a non-transitory computer storage medium, can be used to store non-transitory software programs, non-transitory executable programs, and modules, such as the corresponding program instructions / modules in the embodiments of the present invention. The processor 502 executes various functional applications and data processing by running non-transitory software programs, instructions, and modules stored in the memory 501, thereby implementing the AC / DC distribution network fault protection method in the above method embodiments. The memory 501 may include a program storage area and a data storage area. The program storage area may store the application program required for operating the device and at least one function; the data storage area may store data created by the processor 502, etc. Furthermore, the memory 501 may include a high-speed random access memory 501, and may also include non-transitory memory 501, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 501 may optionally include remotely located memories 501 relative to the processor 502, which can be connected to the processor 502 via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof. One or more modules are stored in the memory 501, and when executed by the processor 502, perform the AC / DC distribution network fault protection method as described in the above method embodiments. The specific details of the aforementioned electronic device can be understood by referring to the relevant descriptions and effects in the above method embodiments, and will not be repeated here.

[0114] This invention also provides a computer-readable storage medium, such as... Figure 10As shown, a computer program 13 is stored on the storage medium. When executed by a processor, this program implements the steps of the AC / DC distribution network fault protection method described in the above embodiments. The storage medium also stores audio and video stream data, feature frame data, interactive request signaling, encrypted data, and preset data sizes. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium can also include combinations of the above types of memory. Those skilled in the art will understand that all or part of the processes in the methods described in the above embodiments can be implemented by a computer program instructing related hardware. The computer program 13 can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium can also include a combination of the above types of memory.

[0115] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fault protection method for AC / DC distribution networks, characterized in that, include: The real-time current of the protection measuring point is obtained, and the protection measuring point is located on the line under test; Extract the high-frequency current component corresponding to the switching frequency of the real-time current. Whether to initiate a protection action for the protection measuring point is determined based on the ratio of the high-frequency current component to the total value of the real-time current, where the total current is the magnitude of the current flowing through the protection measuring point. The step of determining whether to initiate protection action for the protected measuring point based on the ratio of the high-frequency current component to the total real-time current includes: The ratio and the first set value are compared respectively, as well as the relationship between the ratio and the second set value, wherein the second set value is less than the first set value; If the ratio is greater than the first setting value, then the protection action corresponding to the protection measuring point is activated; If the ratio is less than the first set value and greater than the second set value, then a second detection is performed after a preset delay time. If the ratio is less than the second setting value, the protection action will not be initiated; The magnitude of the first setpoint is: in, The first set value, The first reliability coefficient, The minimum value of the ratio of the high-frequency current component to the total current value when a metallic fault occurs in the circuit under test; The value of the second setting is: in, This is the second setpoint. The second reliability coefficient, The minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit and the next-level circuit of the tested circuit. The minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit is: the ratio of the high-frequency current component to the total current when a metallic short circuit occurs at the end of the tested circuit. The minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit and its next-level circuit is: the ratio of the high-frequency current component when a metallic short circuit occurs at the end of the next-level circuit to the total current when a metallic short circuit occurs at the end of the tested circuit.

2. The AC / DC distribution network fault protection method according to claim 1, characterized in that, The step of determining whether to initiate protection action for the protected measuring point based on the ratio of the high-frequency current component to the total real-time current includes: Compare the magnitude of the ratio with the first setpoint; If the ratio is greater than the first setting value, then the protection action corresponding to the protection measuring point is activated; If the ratio is less than the first setting value, the protection action will not be initiated.

3. The AC / DC distribution network fault protection method according to claim 1, characterized in that, The step of re-detecting after a preset delay time includes: After a preset delay time, the relationship between the ratio and the second set value is compared. If the ratio is greater than the second setting value, then the protection action corresponding to the protection measuring point is activated; If the ratio is less than the second setting value, the protection action will not be initiated.

4. The AC / DC distribution network fault protection method according to claim 1, characterized in that, Before extracting the high-frequency current component of the switching frequency corresponding to the real-time current, the method further includes: determining whether the protection start-up conditions are met based on the real-time current; if the real-time current meets the protection start-up conditions, then extracting the high-frequency current component of the switching frequency corresponding to the real-time current; if the real-time current does not meet the protection start-up conditions, then no action is taken.

5. The AC / DC distribution network fault protection method according to claim 4, characterized in that, Determining whether the protection start-up conditions are met based on the real-time current includes: The real-time current is continuously acquired at intervals and the sum of the abrupt changes of several consecutive real-time currents is calculated. If the sum of the abrupt changes is greater than the current protection threshold, then the real-time current meets the protection start condition. The abrupt change is the difference between the currently detected real-time current and the previously detected real-time current.

6. The AC / DC distribution network fault protection method according to claim 1, characterized in that, The AC / DC distribution network is an AC / DC distribution network that includes power electronic transformers.

7. A fault protection device for AC / DC distribution networks, characterized in that, include: The acquisition module is used to acquire the real-time current of the protection measuring point, which is located on the line under test. An extraction module is used to extract the high-frequency current component corresponding to the switching frequency of the real-time current. The protection module is used to determine whether to activate the protection action for the protection measurement point based on the ratio of the high-frequency current component to the total value of the real-time current. The protection module includes: The second comparison submodule is used to compare the ratio and the first setpoint value, as well as the relationship between the ratio and the second setpoint value, wherein the second setpoint value is less than the first setpoint value. The second action submodule is used to activate the protection action corresponding to the protection measuring point when the ratio is greater than the first setting value; when the ratio is less than the first setting value but greater than the second setting value, it will perform a second detection after a preset delay time; when the ratio is less than the second setting value, it will not activate the protection action. The magnitude of the first setpoint is: in, The first set value, The first reliability coefficient, The minimum value of the ratio of the high-frequency current component to the total current value when a metallic fault occurs in the circuit under test; The value of the second setting is: in, This is the second setpoint. The second reliability coefficient, The minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit and the next-level circuit of the tested circuit. The minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit is: the ratio of the high-frequency current component to the total current when a metallic short circuit occurs at the end of the tested circuit. The minimum value of the ratio of the high-frequency current component to the total current when a metallic fault occurs in the tested circuit and its next-level circuit is: the ratio of the high-frequency current component when a metallic short circuit occurs at the end of the next-level circuit to the total current when a metallic short circuit occurs at the end of the tested circuit.

8. The AC / DC distribution network fault protection device according to claim 7, characterized in that, The protection module includes: The first comparison submodule is used to compare the size relationship between the ratio and the first set value; The first action submodule is used to activate the protection action corresponding to the protection measuring point when the ratio is greater than the first setting value, and not activate the protection action when the ratio is less than the first setting value.

9. The AC / DC distribution network fault protection device according to claim 7, characterized in that, The second action submodule includes: The third comparison submodule is used to compare the ratio and the second set value after a preset delay time. The third action submodule is used to activate the protection action corresponding to the protection measurement point when the ratio is greater than the second setting value, and not activate the protection action when the ratio is less than the second setting value.

10. The AC / DC distribution network fault protection device according to claim 7, characterized in that, AC / DC distribution network fault protection devices also include: The start-up judgment module is used to determine whether the protection start-up conditions are met based on the real-time current. If the real-time current meets the protection start-up conditions, the high-frequency current component of the switching frequency corresponding to the real-time current is extracted. If the real-time current does not meet the protection start-up conditions, no action is taken.

11. The AC / DC distribution network fault protection device according to claim 10, characterized in that, The startup determination module includes: The determination submodule is used to continuously acquire the real-time current at intervals and calculate the sum of the sudden changes of several consecutive real-time currents. If the sum of the sudden changes is greater than the current protection threshold, the real-time current meets the protection start condition. The sudden change is the difference between the currently detected real-time current and the previously detected real-time current.

12. An electronic device, characterized in that, include: The system includes a memory and a processor, which are communicatively connected to each other. The memory stores computer instructions, and the processor executes the computer instructions to perform the AC / DC power distribution network fault protection method as described in any one of claims 1 to 6.

13. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to perform the AC / DC distribution network fault protection method as described in any one of claims 1 to 6.

Images