Novel active power distribution network adaptive pilot protection method and device

Abstract

The embodiment of the invention provides a novel active power distribution network adaptive pilot protection method and device, and the method comprises the steps: extracting a sampling current at a preset three-phase current sampling point in a first time window under the condition that the sudden change of any one phase of current in the three-phase current of each feeder line of a power grid is lower than a preset threshold value, inverting the sampling current on one side to obtain the Frechet distance of the inverted sampling current, and determining the waveform difference index of the three-phase current limiting; in a second time window, in response to the fact that the number of times that the waveform difference index is lower than a preset difference threshold value exceeds a preset value, it is judged that a fault exists in the area, and a tripping instruction is sent to the power grid; according to the invention, no extra voltage transformer or master station equipment is needed, the protection sensitivity and the anti-transition resistance capability are improved through the current data at the two ends and the Frechet distance, only one cycle of data needs to be transmitted, the communication burden is reduced, and the method has good engineering applicability, high anti-interference performance and robustness suitable for different fault types, positions and synchronization errors.

Description

Technical Field

[0001] The present application relates to the technical field of active distribution network relay protection, and in particular to a novel active distribution network adaptive longitudinal protection method and device. Background Art

[0002] In recent years, with the rapid development of renewable energy worldwide, distributed generation (DG) has been widely used due to its ease of development and grid connection. Traditional radial distribution networks with single-side power supply have gradually transformed into active distribution networks with multi-terminal power supply. At the same time, different types of DGs exhibit different fault characteristics. Influenced by the inverter control strategy, the fault current of inverter-interfaced distributed generation (IIDG) exhibits characteristics of limited current amplitude and controllable phase angle. Motor-type distributed generation (MTDG), on the other hand, can provide higher short-circuit currents, with a maximum value of approximately 6 to 10 times the rated current.

[0003] Considering these factors, traditional overcurrent protection suffers from problems such as difficult parameter setting, long action delays, and poor selectivity. Furthermore, if distributed generation (DG) systems are disconnected from the grid after a fault, changes in the distribution network topology can also adversely affect traditional protection methods. As the penetration rate of DGs in distribution networks continues to increase, traditional protection strategies are no longer sufficient, and there is an urgent need to introduce innovative, more sensitive, and reliable protection methods. To ensure the safe and stable operation of distribution networks, researchers have proposed a variety of improved protection measures, primarily including the following.

[0004] 1. Improved adaptive overcurrent protection based on traditional three-stage current protection, incorporating directional elements and intelligent electronic devices. However, the complex topology of active distribution networks and the high penetration of distributed generation (DGs) lead to difficulties in protection coordination and delay. Furthermore, existing improved protection schemes are not suitable for island operation and still require coordination with other protection methods.

[0005] 2. Artificial intelligence-based approaches utilize advanced signal processing algorithms for rapid fault identification and the ability to dynamically optimize protection strategies. However, their application relies on large amounts of high-quality training data, which is difficult and costly to obtain. Furthermore, the "black box" nature of AI algorithms makes it difficult to meet the interpretability and reliability requirements of power system protection.

[0006] 3. Active detection-based protection methods inject characteristic signals through power electronics and form protection criteria based on fault current differences. However, these signals can interfere with grid operation, necessitating a balance between protection effectiveness and system stability. Furthermore, this method places high demands on hardware real-time performance and computing power, increasing the complexity of engineering implementation.

[0007] 4. Differential protection based on two-terminal electrical quantities requires additional communication channels but offers higher reliability and faster response in multi-source networks. Current differential protection is also widely used, but it relies on synchronized data at both ends. While 5G communications can facilitate real-time data exchange, high operating costs limit its widespread adoption.

[0008] The existing literature "G. Chen, Y. Liu and Q. Yang, Impedance differential protection for active distribution network, IEEE Trans. Power Del., vol. 35, no. 1, pp. 25-36, Feb. 2020." proposes an impedance differential protection, but it requires an additional voltage transformer and does not consider the unmeasurable T-branch load.

[0009] The existing literature, "TSAghdam, HKKaregar and HHZeineldin, Variable tripping-time differential protection for microgrids considering DG stability," IEEE Trans. Smart Grid, vol. 10, no. 3, pp. 2407-2415, May 2019, proposes a differential protection scheme based on variable tripping time. However, this scheme relies on synchronized data at both ends. While 5G communications can facilitate real-time data exchange, high operating costs limit its widespread application.

[0010] In summary, existing distribution network protection methods have significant limitations under high distributed power generation penetration and complex fault scenarios, and existing protection may refuse to operate, malfunction or fail. Summary of the Invention

[0011] In response to the problems in the prior art, the present application provides a new active distribution network adaptive longitudinal protection method and device, which can improve the protection sensitivity and anti-transition resistance capability by only using the current data and Fréchet distance at both ends without the need for additional voltage transformers or master station equipment. At the same time, it only needs to transmit one cycle of data, reducing the communication burden. It has good engineering applicability, high anti-interference ability and robustness to different fault types, locations and synchronization errors.

[0012] In order to solve at least one of the above problems, the present application provides the following technical solutions:

[0013] According to a first aspect of the embodiments of the present application, the present application provides a novel active distribution network adaptive pilot protection method, comprising:

[0014] Collecting the three-phase currents of each feeder of the power grid, and extracting the sampled currents at the three-phase current sampling points within the first time window when the sudden change amount of any phase current among the three-phase currents is lower than a preset threshold value;

[0015] Inverting the sampling current at one end to obtain an inverted sampling current, and determining the Fréchet distance between the two-end phase current waveforms based on the inverted sampling current and the sampling current at the opposite end;

[0016] determining a waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio;

[0017] In the second time window, in response to the waveform difference index being lower than the preset difference threshold for more times than a preset value, it is determined that a fault exists in the area and a tripping command is sent to the power grid.

[0018] According to any embodiment of the present application, when the sudden change amount of any phase current in the three-phase current is lower than a preset threshold value, extracting the sampled current at a preset three-phase current sampling point within the first time window includes:

[0019] The mutation amount of any phase current in the three-phase current is determined by formula (1), and when the mutation amount is lower than the preset threshold value, the sampling current at the preset three-phase current sampling point in the first time window is extracted:

[0020] ||i(t)-i(tN)|-|i(tN)-i(t-2N)||>I set (1)

[0021] Among them, i(t) is the phase current sampling value of the t-th sampling point, N is the number of sampling points in one power frequency cycle, I set is the preset threshold value.

[0022] According to any embodiment of the present application, inverting the sampling current on one side to obtain the Fréchet distance of the inverted sampling current includes:

[0023] The sampling current on one side is inverted to obtain the inverted sampling current, and the Fréchet distance is determined by formula (2):

[0024]

[0025] Among them, i M is the sampling value of the phase current flowing through the M end of the line, i N is the sampling value of the phase current flowing through the N end of the line, F MN is the Fréchet distance.

[0026] According to any embodiment of the present application, determining the waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio includes:

[0027] The waveform difference index of the three-phase current limiting is determined by formula (3):

[0028] F K =log a F MN (3)

[0029] Where a is the critical minimum area ratio, F K is the waveform difference index of three-phase current limiting.

[0030] According to any embodiment of the present application, within the second time window, in response to the waveform difference index being lower than the preset difference threshold for more than a preset value, determining that a fault exists in the area and sending a trip command to the power grid includes:

[0031] In the second time window, the change state of the waveform difference index is determined by formula (4);

[0032] determining, based on the change state, the number of times the waveform difference index is lower than a preset difference threshold;

[0033] If the waveform difference index is lower than the preset difference threshold for more than a preset number of times, it is determined that there is a fault in the area and a trip command is sent to the power grid;

[0034]

[0035] Among them, φ is used to represent the three-phase current sampling point, F set is the preset difference threshold.

[0036] According to any embodiment of the present application, the first time window is 10 ms.

[0037] According to any embodiment of the present application, the preset difference threshold value ranges from 0.3 to 0.4.

[0038] According to a second aspect of the embodiments of the present application, the present application provides a novel active distribution network adaptive longitudinal protection device, comprising:

[0039] The current acquisition module is used to: collect the three-phase currents of each feeder of the power grid, and extract the sampled currents at the three-phase current sampling points within the first time window when the sudden change amount of any phase current among the three-phase currents is lower than a preset threshold value;

[0040] a distance determination module, configured to: invert the sampling current on one side to obtain an inverted sampling current, and determine the Fréchet distance between the two-phase current waveforms based on the inverted sampling current and the sampling current at the opposite end;

[0041] a difference determination module, configured to determine a waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio;

[0042] The fault determination module is configured to: within a second time window, in response to the waveform difference index being lower than a preset difference threshold for more times than a preset value, determine that a fault exists in the area and send a tripping instruction to the power grid.

[0043] According to any embodiment of the present application, when the amount of sudden change of any phase current in the three-phase current is lower than a preset threshold value, the distance determination module is used to extract the sampled current at the preset three-phase current sampling point within the first time window:

[0044] The mutation amount of any phase current in the three-phase current is determined by formula (1), and when the mutation amount is lower than the preset threshold value, the sampling current at the preset three-phase current sampling point in the first time window is extracted:

[0045] ||i(t)-i(tN)|-|i(tN)-i(t-2N)‖>I set (1)

[0046] Among them, i(t) is the phase current sampling value of the t-th sampling point, N is the number of sampling points in one power frequency cycle, I set is the preset threshold value.

[0047] According to any embodiment of the present application, when the distance determination module inverts the sampling current on one side to obtain the Fréchet distance of the inverted sampling current, it is configured to:

[0048] The sampling current on one side is inverted to obtain the inverted sampling current, and the Fréchet distance is determined by formula (2):

[0049]

[0050] Among them, i M is the sampling value of the phase current flowing through the M end of the line, i N is the sampling value of the phase current flowing through the N end of the line, F MN is the Fréchet distance.

[0051] According to any embodiment of the present application, the difference determination module is specifically configured to:

[0052] The waveform difference index of the three-phase current limiting is determined by formula (3):

[0053] F K =log a F MN (3)

[0054] Where a is the critical minimum area ratio, F K is the waveform difference index of three-phase current limiting.

[0055] According to any embodiment of the present application, the fault determination module is specifically configured to:

[0056] In the second time window, the change state of the waveform difference index is determined by formula (4);

[0057] determining, based on the change state, the number of times the waveform difference index is lower than a preset difference threshold;

[0058] If the waveform difference index is lower than the preset difference threshold for more than a preset number of times, it is determined that there is a fault in the area and a trip command is sent to the power grid;

[0059]

[0060] Among them, φ is used to represent the three-phase current sampling point, F set is the preset difference threshold.

[0061] According to any embodiment of the present application, the first time window is 10 ms.

[0062] According to any embodiment of the present application, the preset difference threshold value ranges from 0.3 to 0.4.

[0063] According to the third aspect of the embodiments of the present application, the present application provides an electronic device, including a memory, a processor, and a computer program stored in the memory and runnable on the processor, wherein when the processor executes the program, the steps of the novel active distribution network adaptive longitudinal protection method are implemented.

[0064] According to a fourth aspect of the embodiments of the present application, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the novel active distribution network adaptive longitudinal protection method.

[0065] According to a fifth aspect of the embodiments of the present application, the present application provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the novel active distribution network adaptive longitudinal protection method.

[0066] It can be seen from the above technical solution that the present application provides a novel active distribution network adaptive longitudinal protection method and device, which extracts the sampled current at the preset three-phase current sampling point in the first time window when the current mutation amount of any phase in the three-phase current of each feeder of the power grid is lower than the preset threshold value, and inverts the sampled current on one side to obtain the Fréchet distance of the inverted sampled current, and determines the waveform difference index of the three-phase current limiting; in the second time window, in response to the number of times the waveform difference index is lower than the preset difference threshold exceeding the preset value, it is determined that there is a fault in the area and a tripping command is sent to the power grid. The present application can improve the protection sensitivity and anti-transition resistance capability only through the current data and Fréchet distance at both ends without the need for additional voltage transformers or master station equipment. At the same time, only one cycle of data needs to be transmitted, reducing the communication burden, and has good engineering applicability, high anti-interference and robustness to different fault types, locations and synchronization errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0068] Figure 1 This is one of the flow charts of the novel active distribution network adaptive pilot protection method in the embodiment of the present application;

[0069] Figure 2 Schematic diagram of an active power distribution network according to an embodiment of the present invention;

[0070] Figure 3 The active distribution network positive sequence equivalent network including IIDG in an embodiment of the present invention;

[0071] Figure 4 A positive sequence network in which the system power supply and the IIDG act respectively according to an embodiment of the present invention;

[0072] Figure 5This is an amplitude-phase relationship diagram of the current differential protection according to an embodiment of the present invention;

[0073] Figure 6 A schematic diagram of the Fréchet distance according to an embodiment of the present invention;

[0074] Figure 7 Schematic diagram of waveform difference index changes according to an embodiment of the present invention;

[0075] Figure 8 The active power distribution network simulation model of the embodiment of the present invention;

[0076] Figure 9 This is a waveform diagram of the current at both ends of the protection when a short circuit fault occurs inside or outside the zone according to an embodiment of the present invention;

[0077] Figure 10 This is a graph showing the waveform difference index changes during an internal and external short-circuit fault according to an embodiment of the present invention;

[0078] Figure 11 A comparison diagram of various protection principles under different transition resistances according to an embodiment of the present invention;

[0079] Figure 12 This is a waveform diagram of the current at both ends of the protection when a short circuit fault occurs inside and outside the protection zone after adding noise according to an embodiment of the present invention;

[0080] Figure 13 This is a graph showing the waveform difference index changes when a short circuit fault occurs inside and outside the region after adding noise according to an embodiment of the present invention;

[0081] Figure 14 A comparison chart of waveform difference indices with and without noise according to an embodiment of the present invention;

[0082] Figure 15 This is a second flow chart of a novel active distribution network adaptive pilot protection method in an embodiment of the present application;

[0083] Figure 16 This is a structural diagram of a novel active distribution network adaptive longitudinal protection device in an embodiment of the present application;

[0084] Figure 17 Schematic diagram of the structure of the electronic device in the embodiment of the present application. DETAILED DESCRIPTION

[0085] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0086] The acquisition, storage, use, and processing of data in the technical solution of this application comply with relevant laws and regulations.

[0087] The present application provides a novel method and device for adaptive longitudinal protection of an active distribution network, which does not require additional voltage transformers or master station equipment. It improves the protection sensitivity and anti-transition resistance capability only through the current data and Fréchet distance at both ends. At the same time, it only needs to transmit data of one cycle, reducing the communication burden. It has good engineering applicability, high anti-interference performance and robustness to different fault types, locations and synchronization errors.

[0088] In order to improve the protection sensitivity and anti-transition resistance capability by only using the current data and Fréchet distance at both ends without the need for additional voltage transformers or master station equipment, and at the same time only need to transmit one cycle of data, reducing the communication burden, and having good engineering applicability, high anti-interference and robustness to different fault types, locations and synchronization errors, the present application provides an embodiment of a novel active distribution network adaptive longitudinal protection method, see Figure 1 The novel active distribution network adaptive longitudinal protection method specifically includes the following contents:

[0089] Step S101: collecting three-phase currents of each feeder of the power grid, and extracting sampled currents at three-phase current sampling points within a first time window when any phase current mutation amount among the three-phase currents is lower than a preset threshold value.

[0090] First, protection devices are deployed on each feeder in the power grid to collect three-phase current data (Phase A, Phase B, and Phase C) in real time. This current data, including current amplitude, phase, and trend, is used for subsequent analysis of the power grid status. Because active distribution networks may contain inverter-type distributed generation (IIDG) or motor-type distributed generation (MTDG), which have different fault characteristics, collecting three-phase current data is essential for accurate fault diagnosis.

[0091] Step S102: inverting the sampling current at one end to obtain an inverted sampling current, and determining the Fréchet distance between the two-end phase current waveforms based on the inverted sampling current and the sampling current at the opposite end.

[0092] When the current mutation rate (i.e., the degree to which the current value changes dramatically within a short period of time) of a particular phase is detected to be below a preset threshold, a short circuit fault is considered to have occurred, necessitating further analysis of the current changes in that phase and the other two phases. From the moment the fault occurs, the system extracts the current sampling points for that phase and its corresponding three-phase current within a fixed time window, generating time series data. Furthermore, to enhance the ability to distinguish fault regions, the current signal sampled on one side is inverted, and the Fréchet distance between this inverted sampling current and the current at the other end is calculated to quantify the shape difference of the current waveforms at both ends.

[0093] Step S103: determining the waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio.

[0094] The calculated Fréchet distance measures the difference in current waveforms between the two ends of a line after a fault occurs. However, in real power grids, due to measurement errors, noise, or synchronization errors, even during normal operation or out-of-zone faults, the current waveforms at both ends of the line may still differ slightly. To avoid misjudgments, the system presets a critical minimum area ratio, which is the minimum change in the current waveform between the two ends of the line under normal or out-of-zone fault conditions. This critical minimum area ratio is then used to convert the Fréchet distance into a waveform difference index, further amplifying the difference between in-zone and out-of-zone faults.

[0095] Step S104: within the second time window, in response to the waveform difference index being lower than the preset difference threshold for more times than a preset value, it is determined that a fault exists in the area and a tripping command is sent to the power grid.

[0096] To further improve the accuracy of fault detection, the system continuously monitors the waveform difference index within a sliding time window. If the waveform difference index falls below the preset difference threshold (i.e., the set fault judgment standard) more times than a preset value within this time window (for example, if the criterion is met three times in a row), it is determined that an internal fault has occurred on that phase, meaning that the fault is within the protected line. At this point, the system will issue a trip command to the power grid, disconnecting the faulty line to prevent further deterioration of the power grid system and ensure power supply security. If the preset value is not reached within the sliding window, the fault is considered to be outside the zone, and the protection system will not operate to avoid false tripping.

[0097] From the above description, it can be seen that the new active distribution network adaptive longitudinal protection method provided in the embodiment of the present application can improve the protection sensitivity and anti-transition resistance capability only through the current data and Fréchet distance at both ends without the need for additional voltage transformers or master station equipment. At the same time, it only needs to transmit one cycle of data, reducing the communication burden. It has good engineering applicability, high anti-interference ability and robustness to different fault types, locations and synchronization errors.

[0098] In one embodiment of the novel active power distribution network adaptive longitudinal protection method of the present application, when the sudden change amount of any phase current among the three-phase currents is lower than a preset threshold value, extracting the sampled current at a preset three-phase current sampling point within a first time window includes:

[0099] The mutation amount of any phase current in the three-phase current is determined by formula (1), and when the mutation amount is lower than the preset threshold value, the sampling current at the preset three-phase current sampling point in the first time window is extracted:

[0100] ||i(t)-i(tN)|-|i(tN)-i(t-2N)||>I set (1)

[0101] Among them, i(t) is the phase current sampling value of the t-th sampling point, N is the number of sampling points in one power frequency cycle, I set is the preset threshold value.

[0102] In one embodiment of the novel active power distribution network adaptive longitudinal protection method of the present application, the step of inverting the sampled current on one side to obtain the Fréchet distance of the inverted sampled current includes:

[0103] The sampling current on one side is inverted to obtain the inverted sampling current, and the Fréchet distance is determined by formula (2):

[0104]

[0105] Among them, when the system is operating normally or an external fault occurs on the feeder MN, the current flowing through the two ends of the feeder is a through current, ensuring that the traditional differential protection remains reliably inactive. However, when an asymmetric fault occurs within the zone, due to the influence of transition resistance and load impedance, some short-circuit current flows across the fault point to the non-fault section and forms a fault through current, affecting the magnitude and phase of the total current of the system. Figure 2 Take this as an example for analysis, is the electromotive force of the system's main power supply, is the electromotive force of IIDG, L L is the load connected to the end of the feeder; Z MN is the equivalent impedance of feeder MN; f1 is the fault point inside the feeder MN section, f2 and f3 are fault points outside the section; x is the ratio of the distance from the fault point f1 to the busbar M end to the total length of the section MN line.

[0106] The output current of IIDG is controlled by power electronic devices. It can be considered that IIDG still satisfies the superposition principle and is equivalent to a current source in the fault additional network. Figure 3 This is the positive sequence equivalent network diagram of the active distribution network containing IIDG. is the positive sequence current output by IIDG; Z M is the equivalent impedance on the system side; Z dg is the internal impedance of the distributed power source DG; Z F is the transition resistance; Z L is the load impedance.

[0107] According to the superposition principle, Figure 3 The system can be decomposed into Figure 4 The positive sequence network shown is acted upon by the system power supply and IIDG respectively. and Short-circuit current provided for system power supply and IIDG respectively; and The ride-through current provided for the system power supply and IIDG respectively.

[0108] The positive direction of current is defined as the direction from the busbar to the line, then:

[0109]

[0110] From the above formula, we can know that the positive sequence current at both ends is and The phase of the fault section is affected by the through current and The impact of and The amplitude and phase are determined by the system power supply, IIDG, load and transition resistance.

[0111] In order to further study the effect of transition resistance on the amplitude-phase relationship of current at both ends, a model is built in PSCAD as follows: Figure 2 The 10kV simple distribution network model shown in the figure has an ungrounded neutral point. In this model, the feeder MN is 3km long, with a positive sequence impedance of (0.17 + j0.34)Ω / km. The IIDG and load capacities on busbar N are 1MW and (5.4 + j2.6)MVA, respectively. When a two-phase ground fault occurs at the midpoint of feeder MN, the magnitude and phase relationship of the differential protection current is analyzed using phase a as an example. Figure 5 shown.

[0112] like Figure 5 As shown in Figure 2, under any operating condition and fault scenario, the amplitude-phase relationship of the short-circuit current on both sides of the protected feeder can be expressed as a point within the unit circle. Assuming that the current amplitude at the M end of the line MN is large, As the reference, the distance from the point to the origin is and The amplitude ratio ε of the point is, and the angle of the point in polar coordinates is and The phase difference θ MNAssuming that the traditional current differential protection braking coefficient K = 0.5, Figure 5 The medium grey area is the protective action area, and the white area is the protective braking area.

[0113] With the transition resistance Z F As the short-circuit current increases, the change in the amplitude-phase relationship of the short-circuit current at both ends is shown in red. ① A two-phase ground short-circuit fault occurs in the system and Z F When it is smaller, there is and The short-circuit current provided by the system power supply and DG is dominant. Figure 5 As shown by the green dot in the middle, due to the control strategy of the downstream IIDG, the output fault current phase angle is controlled. At this time, the short-circuit current at both ends of the fault section is The phase angle difference is about 107°. The amplitude is much greater than The traditional current differential protection can operate correctly. F The value increases to 100Ω, such as Figure 5 As shown by the yellow dot in the middle, and The situation where the through current is dominant. The large through current causes the positive sequence currents at both ends of the fault section to be approximately opposite in direction but equal in magnitude, resulting in obvious refusal of the traditional current differential protection.

[0114] Fréchet distance is a method for measuring the similarity of two trajectories in space, and has now been introduced into the similarity comparison of time domain current signals. Assume that at a certain time t0, in the time window T w There are two sets of sinusoidal AC signals, A and B. These signals can be viewed as two trajectories in space. If the sampling is synchronous and the signals are continuous, these trajectories can be viewed as two points moving along their own paths at the same speed w. Figure 6 Schematic diagram showing the Fréchet distance between signals A and B.

[0115]

[0116] Where: F represents the Fréchet distance, the amplitude of the signal is represented by M, the signal frequency is w, which is set to 50 Hz to match the typical AC power system, i M 、i N To protect the sinusoidal AC signal measured at both ends of MN, the initial phase angle of the signal is expressed as The distance d is calculated using the Euclidean method, that is, the straight-line distance between two points in the trajectory is measured, and inf is the infimum.

[0117] In an optional embodiment, the first time window is 10 ms.

[0118] F(i M ,i N ) contains only the cosine term and the constant term with a frequency of 2w. Therefore, when T w When it is less than 10ms, F(i M ,i N ) will produce periodic fluctuations as the time window slides; when T w When it is greater than or equal to 10ms, F(i M ,i N ) can obtain a stable convergent value, which is only related to the amplitude and phase characteristics of the waveform. Further, it can be organized as follows:

[0119]

[0120] Combined with the cosine theorem, F(i M ,i N ) is a phasor This provides a reliable physical basis for subsequent analysis of its change pattern and threshold setting.

[0121] like Figure 2 As shown, the sampling current flowing through the protection N is inverted to obtain i M and -i N , calculate its Fréchet distance and normalize it as follows:

[0122]

[0123] Combining the physical meaning of Fréchet distance, we can further simplify it and get:

[0124]

[0125] Under normal and out-of-zone fault conditions, the current flowing through both sides of the line is a through current, ε=1, cosθ MN =1, F MN Equal to 0. To explore the F MN With ε, θ MN According to the changes of , the derivatives are taken respectively, as shown in the formula:

[0126]

[0127] It can be seen that F MN monotonically decreases with ε and decreases with θ MN Monotonically increasing. At the same time, since the current on the IIDG side is located in the numerator of the amplitude difference ε formula, the greater the difference in current between the two ends, the smaller ε. Therefore, F MN The difference in amplitude and phase angle of the short-circuit current waveforms at both ends is comprehensively measured, and changes in a positive correlation with the amplitude and phase difference.

[0128] In one embodiment of the novel active distribution network adaptive pilot protection method of the present application, determining the waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio includes:

[0129] The waveform difference index of the three-phase current limiting is determined by formula (3):

[0130] F K =log a F MN (3)

[0131] Where a is the critical minimum area ratio, F K is the waveform difference index of three-phase current limiting.

[0132] When a non-metallic ground fault occurs in the line area, the short-circuit current on both sides increases with the increase of transition resistance. The amplitude and phase difference gradually becomes smaller, F MN Appears close to 0.

[0133] Therefore, taking the critical minimum area ratio a as the base, F MN As the independent variable, a logarithmic function is introduced to amplify the difference in current waveforms at both ends, and the waveform difference index F is defined. K :

[0134] F K =log a F MN

[0135] Where a is the critical minimum area ratio, and F is taken during normal operation and out-of-zone faults. MN Calculated value. Since a is at the base of the logarithmic function and should not be 0, the minimum value 1×10 -3 Instead. F MN When the actual calculation result is less than or equal to a, F is taken. MN =a, so that F K Set it to 1. Since a is a relative ratio value, there is no need to repeat the adjustment according to the actual operating conditions.

[0136] In one embodiment of the novel active distribution network adaptive pilot protection method of the present application, in response to the waveform difference index being lower than a preset difference threshold more times than a preset value within the second time window, determining that a fault exists in the area and sending a trip command to the power grid include:

[0137] In the second time window, the change state of the waveform difference index is determined by formula (4);

[0138] Determine the number of times the waveform difference index is lower than a preset difference threshold according to the change state,

[0139] If the waveform difference index is lower than the preset difference threshold for more than a preset number of times, it is determined that there is a fault in the area and a trip command is sent to the power grid;

[0140]

[0141] Among them, φ is used to represent the three-phase current sampling point, F set is the preset difference threshold.

[0142] Set a suitable starting threshold F set The structural protection criteria for judging internal and external faults are as follows:

[0143]

[0144] The subscript φ represents the three phases A, B, and C. In a three-phase system, a sliding time window is used to detect faults in each phase current. If the protection criteria are met for more than three consecutive times, the phase is considered to have an internal fault; otherwise, it is an external fault and the protection does not operate.

[0145] F set The value of fully considers the influence of synchronization error. The existence of synchronization error only affects the phase relationship of the current at both ends, making the phase difference θ MN The proposed protection is under-capacity protection, so when the fault occurs within the zone, F K The maximum value of F set .

[0146] Known ε to F K is positively correlated, θ MN F K is negatively correlated, so the transition resistance Z F =100Ω high transition resistance case (ε=0.832,θ MN =8°), considering the synchronization error, θ MN =0°, we can get F set =0.3459.

[0147] In an optional embodiment, the preset difference threshold value ranges from 0.3 to 0.4.

[0148] When there is a fault outside the zone, ideally ε=1 and the synchronization error angle is θ d , we can get:

[0149]

[0150] The existing technology proposes a data self-synchronization method based on reference phasors, which can adapt to a large number of T-connected branch access distribution network feeders. The maximum synchronization error is less than 0.3ms, which can be used as a backup synchronization method when the satellite signal is unstable. Considering a certain margin, this paper sets the maximum synchronization error of the data at both ends to 0.5ms, θ d Take 9° and we get F set About 0.35.

[0151] In summary, we can get Figure 7 is the waveform difference index F K With Fréchet distance F MN Change diagram, when the system is operating normally or an out-of-zone fault occurs, as shown by the green line segment in the figure. K The derivative value of the function is in F MN =0 and tends to infinity, that is, a slight increase in the difference in the amplitude and phase of the current at both ends can cause F K The sharp drop of , effectively improves the sensitivity of protection. Consider the transition resistance Z when the fault occurs in the zone F =100Ω limit, use the red point (ε max ≈0.9,θ MN ≈10°) indicates that F K It is still smaller than the set value and is located within the blue curve of the action section.

[0152] This application further discloses a verification case based on the above-mentioned novel active distribution network adaptive longitudinal protection method.

[0153] An active distribution network model was built using the electromagnetic transient simulation software PSCAD / EMTDC to simulate and verify the novel active distribution network adaptive pilot protection method proposed in this embodiment:

[0154] 1) Build a model

[0155] Simulate in PSCAD / EMTDC Figure 2 Build an active distribution network simulation model such as Figure 8 As shown. The system voltage level is 10kV, and the neutral point is directly grounded. DG1 is an IIDG with a capacity of 1MW; L1 and L2 are loads connected to the busbar with a capacity of 6MVA; the positive sequence impedance of the feeder is (0.17+j0.34)Ω / km, and feeder B1B 2、 The lengths of B2 and B3 are 3 km and 6 km respectively; the fault points are both located at the midpoint of the feeder section.

[0156] 2) Simulation analysis

[0157] a) Simulation results of internal and external faults:

[0158] This section mainly takes the feeder segment B1B2 between R1 and R2 as the research object, and sets different types of metallic short-circuit faults at the fault points f1 and f2, with a fault time of 2s. Figure 9 To protect the current at both ends during a three-phase short circuit fault. Figure 10 F is the corresponding waveform difference index when the fault occurs inside and outside the zone K .

[0159] Depend on Figure 10 As shown in (a), when a short circuit fault occurs at f1, the three-phase waveform difference index F K Rapidly decreases to below the setting threshold, and the proposed protection criterion accurately identifies it as an internal fault; Figure 10 From (b), we can see that when a short circuit fault occurs at f2, the three-phase waveform difference index F K When it is maintained at 1, the proposed protection principle identifies the fault as out-of-zone fault and can reliably not operate. The simulation results for the faults inside and outside the zone are shown in Table 1.

[0160] Table 1

[0161]

[0162]

[0163] Table 1 shows the calculated F in the 10ms time window after the fault occurs. K For the fault at point f2, F K Keeping it at 1, which is much higher than the threshold of 0.35, means no action. For the fault at point f1, the F K The values ​​of the phases with no faults are all below the threshold, while the value of the phases without faults remains at 1. The simulation results show that the proposed protection principle can effectively distinguish between internal and external faults and accurately identify the faulty phase. This verifies the reliability and sensitivity of the proposed protection method.

[0164] When an out-of-zone metallic fault occurs downstream of the protected line, the difference in capacitive current flowing on both sides of the protected line increases accordingly, leading to a larger difference in the current waveforms on both sides. However, the data in Table 1 shows that when a metallic fault occurs at point f2, the protection remains reliably inactive. This is due to the low voltage level of the 10kV distribution network, making the capacitive current negligible compared to the fault current.

[0165] For high resistance ground short circuit fault, the transition resistance Z F To verify the proposed method's tolerance to high transition resistances, single-phase and two-phase ground faults were simulated at the fault point f1, with different transition resistance values ​​set. The simulation results for different transition resistances during an intra-zone fault are shown in Table 2.

[0166] Table 2

[0167]

[0168] It can be seen from Table 2 that as the transition resistance Z F The increase of F K However, no matter what type of fault occurs and what the transition resistance is, the protection will not trip falsely for faults outside the zone and will not refuse to trip for faults inside the zone.

[0169] b) Protection against synchronization error performance test:

[0170] The protection's anti-synchronization error performance is tested using the fault scenario described in Section (a). After adding a synchronization error of 0.5 ms, the simulation results for both internal and external faults after considering the synchronization error are shown in Table 3.

[0171] Table 3

[0172]

[0173] Comparing the data in Table 3 and Table 1, it can be seen that when the fault occurs in the zone, the non-fault phase F K The calculated value is no longer close to 1, the fault phase F K The calculated value can still be guaranteed to be less than F set ; When the fault occurs outside the zone, the three-phase F K The calculated values ​​are all less than 1 and greater than F set Although the calculation accuracy has decreased, it can still ensure that the protection will not be activated.

[0174] c) Comparative analysis with existing protection principles:

[0175] When a two-phase ground short circuit fault is set at the fault point f2 with different transition resistances, the operating performance of the Euclidean distance algorithm, cosine method, and positive sequence component differential protection algorithm is as follows: Figure 11 As shown in the figure, the Euclidean distance coefficient is a positive indicator; protection is activated when its value is greater than the threshold; the cosine correlation coefficient is a negative indicator; protection is activated when its value is less than the threshold. The positive sequence component differential protection algorithm constant is set to 0.5, and protection is activated when the braking coefficient is greater than 0.5.

[0176] exist Figure 11 In the example, the results of (a), (b) and (d) are calculated based on the current of phase A. Figure 11 As shown in (a), (b) and (c), when a non-metallic ground fault occurs in the line, the amplitude and phase difference of the current at both ends become less obvious as the transition resistance increases. The traditional waveform similarity algorithm and the positive sequence component differential protection algorithm both show a significant decrease in sensitivity and have the risk of false operation. However, as Figure 11 As shown in (d), when a fault occurs, the current at both ends of the proposed protection method changes significantly, F K Rapidly drops and reaches the set threshold within 1 millisecond, with good speed. At the same time, after the fault is stable, FK A stable convergence value is achieved. Compared with other similarity algorithms, the proposed method has significant advantages in sensitivity, reliability, action speed and resistance to synchronization errors.

[0177] d) Protection anti-noise performance test:

[0178] There will be some noise in the measured current of the protection device due to electromagnetic interference. In order to study whether the proposed method is applicable when there is noise, a three-phase metallic short circuit is set at the fault points f1 and f2, and Gaussian white noise with a signal-to-noise ratio of 30dB is superimposed on each of them. The current at both ends is compared with F K Waveform Figure 12 、 Figure 13 shown.

[0179] Figure 14 F before and after noise superposition K Comparison chart, by Figure 14 It can be seen that the proposed algorithm is a protection criterion based on the difference in current waveforms at both ends. The presence of noise makes the current waveforms at both ends no longer completely overlap when there is an out-of-zone fault. However, due to F set Taking the synchronization error into consideration and taking a smaller value, under the condition of 30dB, the protection can still ensure correct non-action; and when the fault occurs within the zone, the difference in current waveform caused by the short-circuit fault itself is much greater than the impact of noise on the current waveform, F K The calculated value is independent of the noise level and remains close to the case where there is no noise.

[0180] The present invention focuses on the characteristics of inverter-type distributed power sources under weak fault conditions and the impact of system fault through-current on the performance of traditional longitudinal differential protection, and analyzes the amplitude and phase difference of the positive sequence current at both ends of the line after faults inside and outside the area. Based on this, a new adaptive longitudinal protection method for active distribution networks is proposed. The method first installs protection devices on each feeder of the node, collects three-phase currents in real time and determines whether a short-circuit fault occurs. Once a short-circuit fault occurs, the system will extract the three-phase current sampling data at both ends of the line within a 10ms time window, and invert the sampling current on one side, and then calculate its Fréchet distance and normalize it. Taking the critical minimum area ratio a as the base, F MN As the independent variable, a logarithmic function is introduced to amplify the difference in current waveforms at both ends, and then the waveform difference index F is defined. K. By fully considering factors such as synchronization error and setting a suitable starting threshold value, the action criterion of the longitudinal protection is constructed. When the criterion is met, it is determined that an in-zone fault has occurred and a tripping command is sent. The PSCAD simulation results show that under various fault conditions in the active distribution network, the protection method proposed in the present invention can reliably identify the fault section. Compared with traditional differential protection and waveform similarity algorithms, this protection method has the advantages of small data transmission volume, strong transition resistance resistance, and low noise influence, which significantly improves the sensitivity and speed of protection.

[0181] For further explanation of this scheme, see Figure 15 The present application also provides a specific application example of implementing a novel active distribution network adaptive pilot protection method using the novel active distribution network adaptive pilot protection device, which specifically includes the following contents:

[0182] S01: Start system initialization and enter the operation process of the protection algorithm, waiting for a grid fault or a sudden change signal to trigger the protection logic.

[0183] S02: Obtain current information on both sides of the protected line:

[0184] The system's protection devices collect three-phase current information in real time at both ends of the protected line (terminals M and N). This data is used to determine whether a short-circuit fault has occurred and serves as the basis for calculating waveform differences.

[0185] S03: Determine whether the sudden change protection is triggered. The system detects whether the sudden change of the three-phase current (i.e., the degree of sudden change of the current) exceeds the preset threshold value:

[0186] If the current mutation exceeds the threshold value (a drastic change occurs), a fault may have occurred and the process goes to S04 for detailed analysis;

[0187] If the current mutation amount does not exceed the threshold value, the grid state is considered normal, the protection does not operate, and returns to S02 to continue monitoring.

[0188] S04: Collect three-phase current data within 10ms after the sudden change occurs, and reverse the current on one side. When the sudden change protection is triggered:

[0189] Record the three-phase current sampling points at both ends of the protection line within a 10ms time window to ensure that the data covers the dynamic process before and after the fault.

[0190] The current sampling points on one side are inverted to calculate the difference in the current waveforms at both ends.

[0191] S05: Send fault information to the peer end and request peer end data:

[0192] The system's protection device sends a fault signal to the opposite protection device and requests 10ms three-phase current sampling data from the opposite end to ensure that the input data for the Fréchet distance calculation is complete.

[0193] S06: Determine whether the current information of the other end is received:

[0194] If the current information of the other end is received, then the process proceeds to S07 to calculate the Fréchet distance;

[0195] If no information is received from the other end, it may be a communication failure or system abnormality. The protection will not trip and return to S02 to continue monitoring.

[0196] S07: Calculate the Fréchet distance F between the two ends MN :

[0197] After receiving the data from the other end, the system calculates the Fréchet distance of the current waveforms at both ends:

[0198] The Fréchet distance is used to measure the difference between the current waveforms at both ends.

[0199] The larger the distance, the greater the difference in current waveforms at both ends, and an internal fault may have occurred.

[0200] S08: Calculate the waveform difference index F K :

[0201] After calculating the Fréchet distance F MN After that, the system further calculates the waveform difference index F K .

[0202] S09: Determine the waveform difference index F K Is it lower than the set threshold F? set :

[0203] If F K <F set , then enter S10 and determine it as an internal fault;

[0204] If F K ≥F set , then enter S11, determine it is an out-of-zone fault, and the protection does not operate.

[0205] S10: Determined as an internal fault, triggering a trip:

[0206] Because F K If the voltage is lower than the threshold, it means that the current waveforms at both ends have undergone significant changes in amplitude and phase. It is judged as an internal fault and the system sends a tripping command to cut off the fault line to prevent the fault from further expanding and ensure the stability of the power supply system.

[0207] S11: Determined to be an out-of-zone fault, protection does not operate:

[0208] Because F K If the value is not lower than the set threshold, it indicates that the fault may occur outside the protected line or the line is in normal operation.

[0209] The system does not trigger tripping, avoiding false operation and causing power outages in non-fault areas, thereby improving the reliability of the power supply system.

[0210] In order to improve the protection sensitivity and anti-transition resistance capability by only using the current data and Fréchet distance at both ends without the need for additional voltage transformers or master station equipment, and at the same time only need to transmit data of one cycle, thereby reducing the communication burden, and having good engineering applicability, high anti-interference and robustness to different fault types, locations and synchronization errors, the present application provides an embodiment of a new active distribution network adaptive longitudinal protection device for implementing all or part of the content of the new active distribution network adaptive longitudinal protection method, see Figure 16 The novel active distribution network adaptive longitudinal protection device specifically includes the following contents:

[0211] The current acquisition module 1101 is configured to: acquire the three-phase currents of each feeder of the power grid, and extract the sampled currents at the three-phase current sampling points within a first time window when the sudden change in any phase current among the three-phase currents is lower than a preset threshold value;

[0212] The distance determination module 1102 is configured to: invert the sampling current at one end to obtain an inverted sampling current, and determine the Fréchet distance between the two-end phase current waveforms based on the inverted sampling current and the sampling current at the opposite end;

[0213] The difference determination module 1103 is configured to determine a waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio;

[0214] The fault determination module 1104 is configured to: within a second time window, in response to the waveform difference index being lower than a preset difference threshold for more times than a preset value, determine that a fault exists in the area and send a tripping instruction to the power grid.

[0215] According to any embodiment of the present application, when the amount of sudden change of any phase current in the three-phase current is lower than a preset threshold value, the distance determination module is used to extract the sampled current at the preset three-phase current sampling point within the first time window:

[0216] The mutation amount of any phase current in the three-phase current is determined by formula (1), and when the mutation amount is lower than the preset threshold value, the sampling current at the preset three-phase current sampling point in the first time window is extracted:

[0217] ||i(t)-i(tN)|-|i(tN)-i(t-2N)||>I set (1)

[0218] Among them, i(t) is the phase current sampling value of the t-th sampling point, N is the number of sampling points in one power frequency cycle, I set is the preset threshold value.

[0219] According to any embodiment of the present application, when the distance determination module inverts the sampling current on one side to obtain the Fréchet distance of the inverted sampling current, it is configured to:

[0220] The sampling current on one side is inverted to obtain the inverted sampling current, and the Fréchet distance is determined by formula (2):

[0221]

[0222] Among them, i M is the sampling value of the phase current flowing through the M end of the line, i N is the sampling value of the phase current flowing through the N end of the line, F MN is the Fréchet distance.

[0223] According to any embodiment of the present application, the difference determination module is specifically configured to:

[0224] The waveform difference index of the three-phase current limiting is determined by formula (3):

[0225] F K =log a F MN (3)

[0226] Where a is the critical minimum area ratio, F K is the waveform difference index of three-phase current limiting.

[0227] According to any embodiment of the present application, the fault determination module is specifically configured to:

[0228] In the second time window, the change state of the waveform difference index is determined by formula (4);

[0229] determining, based on the change state, the number of times the waveform difference index is lower than a preset difference threshold;

[0230] If the waveform difference index is lower than the preset difference threshold for more than a preset number of times, it is determined that there is a fault in the area and a trip command is sent to the power grid;

[0231]

[0232] Among them, φ is used to represent the three-phase current sampling point, Fset is the preset difference threshold.

[0233] According to any embodiment of the present application, the first time window is 10 ms.

[0234] According to any embodiment of the present application, the preset difference threshold value ranges from 0.3 to 0.4.

[0235] From the above description, it can be seen that the new active distribution network adaptive longitudinal protection device provided in the embodiment of the present application can improve the protection sensitivity and anti-transition resistance capability only through the current data and Fréchet distance at both ends without the need for additional voltage transformers or master station equipment. At the same time, it only needs to transmit one cycle of data, reducing the communication burden. It has good engineering applicability, high anti-interference ability and robustness to different fault types, locations and synchronization errors.

[0236] From a hardware perspective, in order to improve protection sensitivity and transition resistance capability by using only current data and Fréchet distance at both ends without requiring additional voltage transformers or master station equipment, while only transmitting data for one cycle, reducing the communication burden, and having good engineering applicability, high anti-interference performance, and robustness to different fault types, locations, and synchronization errors, the present application provides an embodiment of an electronic device for implementing all or part of the content of the novel active distribution network adaptive longitudinal protection method. The electronic device specifically includes the following content:

[0237] A processor, a memory, a communications interface, and a bus; wherein the processor, memory, and communications interface communicate with each other via the bus; the communications interface is used to transmit information between the novel active distribution network adaptive pilot protection device and related devices such as core business systems, user terminals, and related databases; the logic controller can be a desktop computer, a tablet computer, a mobile terminal, etc., but this embodiment is not limited thereto. In this embodiment, the logic controller can be implemented with reference to the embodiments of the novel active distribution network adaptive pilot protection method and the embodiments of the novel active distribution network adaptive pilot protection device in the embodiments, the contents of which are incorporated herein and repeated parts are not repeated.

[0238] It is understandable that the user terminal may include a smart phone, a tablet electronic device, a network set-top box, a portable computer, a desktop computer, a personal digital assistant (PDA), a vehicle-mounted device, a smart wearable device, etc. Among them, the smart wearable device may include smart glasses, a smart watch, a smart bracelet, etc.

[0239] In practical applications, portions of the novel active distribution network adaptive longitudinal protection method can be executed on the electronic device side as described above, or all operations can be performed on the client device. The specific selection can be based on the processing capabilities of the client device and the limitations of the user's usage scenario. This application does not impose any restrictions on this. If all operations are performed on the client device, the client device may also include a processor.

[0240] The client device may include a communication module (i.e., a communication unit) that can establish a communication connection with a remote server to implement data transmission with the server. The server may include a server on the task scheduling center side, and in other implementation scenarios, may also include a server on an intermediate platform, such as a server on a third-party server platform that has a communication link with the task scheduling center server. The server may include a single computer device, a server cluster consisting of multiple servers, or a server structure of a distributed device.

[0241] Figure 17 Schematic block diagram of the system structure of the electronic device 9600 according to an embodiment of the present application. Figure 17 As shown, the electronic device 9600 may include a central processing unit 9100 and a memory 9140; the memory 9140 is coupled to the central processing unit 9100. It is worth noting that the Figure 17 is exemplary; other types of structures may also be used to supplement or replace this structure to implement telecommunication functions or other functions.

[0242] In one embodiment, the functions of the novel active distribution network adaptive pilot protection method can be integrated into the central processing unit 9100. The central processing unit 9100 can be configured to perform the following control:

[0243] Step S101: collecting three-phase currents of each feeder of the power grid, and extracting sampled currents at three-phase current sampling points within a first time window when a sudden change in any phase current among the three-phase currents is lower than a preset threshold value;

[0244] Step S102: inverting the sampling current at one end to obtain an inverted sampling current, and determining the Fréchet distance between the two-end phase current waveforms based on the inverted sampling current and the sampling current at the opposite end;

[0245] Step S103: determining the waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio;

[0246] Step S104: within the second time window, in response to the waveform difference index being lower than the preset difference threshold for more times than a preset value, it is determined that a fault exists in the area and a tripping command is sent to the power grid.

[0247] From the above description, it can be seen that the electronic device provided in the embodiment of the present application does not require additional voltage transformers or master station equipment. It only improves the protection sensitivity and anti-transition resistance capability through the current data and Fréchet distance at both ends. At the same time, it only needs to transmit one cycle of data, reducing the communication burden. It has good engineering applicability, high anti-interference ability and robustness to different fault types, locations and synchronization errors.

[0248] In another embodiment, the new active distribution network adaptive longitudinal protection device can be configured separately from the central processor 9100. For example, the new active distribution network adaptive longitudinal protection device can be configured as a chip connected to the central processor 9100, and the function of the new active distribution network adaptive longitudinal protection method can be realized through the control of the central processor.

[0249] like Figure 17 As shown, the electronic device 9600 may further include: a communication module 9110, an input unit 9120, an audio processor 9130, a display 9160, and a power supply 9170. It is worth noting that the electronic device 9600 does not necessarily have to include Figure 17 In addition, the electronic device 9600 may also include all components shown in Figure 17 For components not shown, reference may be made to the prior art.

[0250] like Figure 17 As shown, the central processing unit 9100 is sometimes also referred to as a controller or operation control, and may include a microprocessor or other processor device and / or logic device. The central processing unit 9100 receives input and controls the operation of various components of the electronic device 9600.

[0251] Memory 9140 can be, for example, one or more of a cache, flash memory, hard drive, removable media, volatile memory, non-volatile memory, or other suitable devices. It can store the aforementioned failure-related information and also store programs that execute the relevant information. The CPU 9100 can execute the programs stored in memory 9140 to implement information storage or processing.

[0252] The input unit 9120 provides input to the central processing unit 9100. The input unit 9120 may be, for example, a keypad or touch input device. The power supply 9170 is used to provide power to the electronic device 9600. The display 9160 is used to display objects such as images and text. The display may be, for example, an LCD display, but is not limited thereto.

[0253] The memory 9140 may be a solid-state memory, such as a read-only memory (ROM), a random access memory (RAM), or a SIM card. Alternatively, it may be a memory that retains information even when power is off, can be selectively erased, and is provided with more data. Examples of such memory are sometimes referred to as EPROMs. The memory 9140 may also be some other type of device. The memory 9140 includes a buffer memory 9141 (sometimes referred to as a buffer). The memory 9140 may include an application / function storage unit 9142 for storing application programs and function programs or processes for executing the operation of the electronic device 9600 by the central processing unit 9100.

[0254] The memory 9140 may also include a data storage unit 9143 for storing data, such as contacts, digital data, pictures, sounds, and / or any other data used by the electronic device. The driver storage unit 9144 of the memory 9140 may include various driver programs for communication functions of the electronic device and / or for executing other functions of the electronic device (such as messaging applications, address book applications, etc.).

[0255] The communication module 9110 is a transmitter / receiver that transmits and receives signals via the antenna 9111. The communication module (transmitter / receiver) 9110 is coupled to the central processor 9100 to provide input signals and receive output signals, which may be the same as the case of a conventional mobile communication terminal.

[0256] Based on different communication technologies, multiple communication modules 9110 can be provided in the same electronic device, such as a cellular network module, a Bluetooth module, and / or a wireless local area network module. The communication module (transmitter / receiver) 9110 is also coupled to a speaker 9131 and a microphone 9132 via an audio processor 9130 to provide audio output via the speaker 9131 and receive audio input from the microphone 9132, thereby implementing common telecommunication functions. The audio processor 9130 may include any suitable buffer, decoder, amplifier, etc. Furthermore, the audio processor 9130 is also coupled to the central processing unit 9100, enabling local recording via the microphone 9132 and playback of stored audio via the speaker 9131.

[0257] The embodiments of the present application also provide a computer-readable storage medium capable of implementing all steps of the novel active distribution network adaptive pilot protection method in the above-mentioned embodiments, where the execution subject is a server or a client. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the computer program implements all steps of the novel active distribution network adaptive pilot protection method in the above-mentioned embodiments, where the execution subject is a server or a client. For example, when the processor executes the computer program, the following steps are implemented:

[0258] Step S101: collecting three-phase currents of each feeder of the power grid, and extracting sampled currents at three-phase current sampling points within a first time window when a sudden change in any phase current among the three-phase currents is lower than a preset threshold value;

[0259] Step S102: inverting the sampling current at one end to obtain an inverted sampling current, and determining the Fréchet distance between the two-end phase current waveforms based on the inverted sampling current and the sampling current at the opposite end;

[0260] Step S103: determining the waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio;

[0261] Step S104: within the second time window, in response to the waveform difference index being lower than the preset difference threshold for more times than a preset value, it is determined that a fault exists in the area and a tripping command is sent to the power grid.

[0262] From the above description, it can be seen that the computer-readable storage medium provided in the embodiment of the present application does not require additional voltage transformers or master station equipment, and only improves the protection sensitivity and anti-transition resistance capability through the current data and Fréchet distance at both ends. At the same time, it only needs to transmit one cycle of data, reducing the communication burden. It has good engineering applicability, high anti-interference ability and robustness to different fault types, locations and synchronization errors.

[0263] The embodiments of the present application also provide a computer program product capable of implementing all steps of the novel active distribution network adaptive pilot protection method in the above-mentioned embodiments, where the execution subject is a server or a client. When the computer program / instructions are executed by a processor, the steps of the novel active distribution network adaptive pilot protection method are implemented. For example, the computer program / instructions implement the following steps:

[0264] Step S101: collecting three-phase currents of each feeder of the power grid, and extracting sampled currents at three-phase current sampling points within a first time window when a sudden change in any phase current among the three-phase currents is lower than a preset threshold value;

[0265] Step S102: inverting the sampling current at one end to obtain an inverted sampling current, and determining the Fréchet distance between the two-end phase current waveforms based on the inverted sampling current and the sampling current at the opposite end;

[0266] Step S103: determining the waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio;

[0267] Step S104: within the second time window, in response to the waveform difference index being lower than the preset difference threshold for more times than a preset value, it is determined that a fault exists in the area and a tripping command is sent to the power grid.

[0268] From the above description, it can be seen that the computer program product provided in the embodiment of the present application does not require additional voltage transformers or master station equipment, and only improves the protection sensitivity and anti-transition resistance capability through the current data and Fréchet distance at both ends. At the same time, it only needs to transmit one cycle of data, reducing the communication burden. It has good engineering applicability, high anti-interference ability and robustness to different fault types, locations and synchronization errors.

[0269] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, apparatus, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0270] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (apparatus), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as a combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0271] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0272] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0273] Specific embodiments are used in the present invention to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A novel active distribution network adaptive pilot protection method, characterized in that: The method comprises: Collecting the three-phase currents of each feeder of the power grid, and extracting the sampled currents at the three-phase current sampling points within the first time window when the sudden change amount of any phase current among the three-phase currents is lower than a preset threshold value; Inverting the sampling current at one end to obtain an inverted sampling current, and determining the Fréchet distance between the two-end phase current waveforms based on the inverted sampling current and the sampling current at the opposite end; determining a waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio; In the second time window, in response to the waveform difference index being lower than the preset difference threshold for more times than a preset value, it is determined that a fault exists in the area and a tripping command is sent to the power grid.

2. The novel active distribution network adaptive pilot protection method according to claim 1 is characterized in that: When the sudden change amount of any phase current in the three-phase current is lower than a preset threshold value, extracting the sampled current at a preset three-phase current sampling point within the first time window includes: The mutation amount of any phase current in the three-phase current is determined by formula (1), and when the mutation amount is lower than the preset threshold value, the sampling current at the preset three-phase current sampling point in the first time window is extracted: ||i(t)-i(t-N)|-|i(t-N)-i(t-2N)||>I set (1) Among them, i(t) is the phase current sampling value of the t-th sampling point, N is the number of sampling points in one power frequency cycle, I set is the preset threshold value.

3. The novel active distribution network adaptive pilot protection method according to claim 1 is characterized in that: The method of inverting the sampling current on one side to obtain the Fréchet distance of the inverted sampling current includes: The sampling current on one side is inverted to obtain the inverted sampling current, and the Fréchet distance is determined by formula (2): Among them, i M is the sampling value of the phase current flowing through the M end of the line, i N is the sampling value of the phase current flowing through the N end of the line, F MN is the Fréchet distance.

4. The novel active distribution network adaptive pilot protection method according to claim 1 is characterized in that: Determining the waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio includes: The waveform difference index of the three-phase current limiting is determined by formula (3): F K =log a F MN (3) Where a is the critical minimum area ratio, F K is the waveform difference index of three-phase current limiting.

5. The novel active distribution network adaptive pilot protection method according to claim 1 is characterized in that: In the second time window, in response to the waveform difference index being lower than the preset difference threshold for a number of times exceeding a preset value, determining that a fault exists in the area and sending a tripping instruction to the power grid include: In the second time window, the change state of the waveform difference index is determined by formula (4); determining, based on the change state, the number of times the waveform difference index is lower than a preset difference threshold; If the waveform difference index is lower than the preset difference threshold for more than a preset number of times, it is determined that there is a fault in the area and a trip command is sent to the power grid; Among them, φ is used to represent the three-phase current sampling point, F set is the preset difference threshold.

6. The novel active distribution network adaptive pilot protection method according to claim 1 is characterized in that: The first time window is 10 ms.

7. The novel active distribution network adaptive pilot protection method according to claim 1, characterized in that: The preset difference threshold value ranges from 0.3 to 0.

4.

8. A new type of active distribution network adaptive longitudinal protection device, characterized in that: The device comprises: The current acquisition module is used to: collect the three-phase currents of each feeder of the power grid, and extract the sampled currents at the three-phase current sampling points within the first time window when the sudden change amount of any phase current among the three-phase currents is lower than a preset threshold value; a distance determination module, configured to: invert the sampling current on one side to obtain an inverted sampling current, and determine the Fréchet distance between the two-phase current waveforms based on the inverted sampling current and the sampling current at the opposite end; a difference determination module, configured to determine a waveform difference index of the three-phase current limiting according to the Fréchet distance and a preset critical minimum area ratio; The fault determination module is configured to: within a second time window, in response to the waveform difference index being lower than a preset difference threshold for a number of times exceeding a preset value, determine that a fault exists in the area and send a tripping instruction to the power grid.

9. The novel active distribution network adaptive longitudinal protection device according to claim 8 is characterized in that: When the sudden change amount of any phase current in the three-phase current is lower than a preset threshold value, the distance determination module is used to extract the sampled current at the preset three-phase current sampling point in the first time window: The mutation amount of any phase current in the three-phase current is determined by formula (1), and when the mutation amount is lower than the preset threshold value, the sampling current at the preset three-phase current sampling point in the first time window is extracted: ||i(t)-i(t-N)|-|i(t-N)-i(t-2N)||>I set (1) Among them, i(t) is the phase current sampling value of the t-th sampling point, N is the number of sampling points in one power frequency cycle, I set is the preset threshold value.

10. The novel active distribution network adaptive longitudinal protection device according to claim 8, characterized in that: When the distance determination module inverts the sampling current on one side to obtain the Fréchet distance of the inverted sampling current, it is used to: The sampling current on one side is inverted to obtain the inverted sampling current, and the Fréchet distance is determined by formula (2): Among them, i M is the sampling value of the phase current flowing through the M end of the line, i N is the sampling value of the phase current flowing through the N end of the line, F MN is the Fréchet distance.

11. The novel active distribution network adaptive longitudinal protection device according to claim 8, characterized in that: The difference determination module is specifically used for: The waveform difference index of the three-phase current limiting is determined by formula (3): F K =log a F MN (3) Where a is the critical minimum area ratio, F K is the waveform difference index of three-phase current limiting.

12. The novel active distribution network adaptive longitudinal protection device according to claim 8, characterized in that: The fault determination module is specifically configured to: In the second time window, the change state of the waveform difference index is determined by formula (4); determining, based on the change state, the number of times the waveform difference index is lower than a preset difference threshold; If the waveform difference index is lower than the preset difference threshold for more than a preset number of times, it is determined that there is a fault in the area and a trip command is sent to the power grid; Among them, φ is used to represent the three-phase current sampling point, F set is the preset difference threshold.

13. The novel active distribution network adaptive longitudinal protection device according to claim 8, characterized in that: The first time window is 10 ms.

14. The novel active distribution network adaptive longitudinal protection device according to claim 8, characterized in that: The preset difference threshold value ranges from 0.3 to 0.

4.

15. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps of the novel active distribution network adaptive longitudinal protection method according to any one of claims 1 to 7 are implemented.

16. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the novel active distribution network adaptive longitudinal protection method according to any one of claims 1 to 7 are implemented.

17. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instruction is executed by a processor, the steps of the novel active distribution network adaptive longitudinal protection method according to any one of claims 1 to 7 are implemented.

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