Low-voltage distribution area fault detection method and system based on wide-area response of active distribution network

Abstract

This invention relates to the field of distribution network fault detection technology, and is a method and system for detecting low-voltage distribution area faults based on the wide-area response of an active distribution network. The system includes a data acquisition and processing unit, which acquires signal data from the active distribution network lines and preprocesses the signal data. The acquired signal data includes voltage and current signals at the grid connection points of each distributed power source on the active distribution network lines, as well as current signals at the outgoing lines of the low-voltage distribution area. A voltage limit judgment unit determines whether more than 50% of the distributed power source grid connection points on the active distribution network lines have exceeded the voltage limit. This invention senses low-voltage distribution area faults through the wide-area response of an active distribution network containing distributed power sources, and constructs fault detection criteria through wide-area response parameters and their spatiotemporal distribution characteristics, achieving effective low-voltage distribution area fault detection and location, and improving the efficiency of fault detection.

Description

Technical Field

[0001] This invention relates to the field of power distribution network fault detection technology, and in particular to a method and system for detecting low-voltage distribution area faults based on the wide-area response of active power distribution networks. Background Technology

[0002] As the energy transition deepens, distribution networks are gradually evolving from traditional passive, radial networks into active distribution networks with highly integrated distributed renewable energy. This fundamental change, while improving energy efficiency, also brings unprecedented challenges and benefits to the safe and stable operation of distribution networks, especially in fault detection and protection.

[0003] Low-voltage distribution areas (i.e., the network below the transformer supplying power to end users) represent the "last mile" of the distribution network, and fault detection in these areas has long faced challenges. When a fault occurs in a low-voltage distribution area, the short-circuit current may be very small by the time it reaches the upstream main line, insufficient to trigger the current protection at the line's inception. Furthermore, common faults in low-voltage distribution areas, such as conductor contact with trees or the ground, exhibit high transition resistance characteristics. The protection systems configured on the low-voltage side of these distribution areas are relatively simple, making it difficult to detect minor faults and faults with high transition resistance, posing safety hazards and potentially escalating into more serious faults. This creates a protection dead zone—a fault has occurred within the low-voltage distribution area, but upstream or local protection systems cannot effectively detect and isolate it.

[0004] Active distribution networks supply power to numerous low-voltage distribution areas, and also host many distributed power sources along these lines. Faults in low-voltage distribution areas often fail to trigger the line current protection devices. Furthermore, the fault detection devices installed in low-voltage distribution areas are relatively weak; during a fault, especially when the transition resistance of the fault is high, these devices will be unable to effectively detect the fault. Simultaneously, low-voltage distribution area faults will cause fault responses from a wide range of distributed power sources along the active distribution network lines.

[0005] Traditional fault diagnosis approaches rely on "on-site detection," utilizing only local information while neglecting wide-area, interconnected response information. With the development of smart grids, advanced sensors such as synchronous phasor measurement units are increasingly deployed in distribution networks, especially at distributed generation grid connection points, enabling the acquisition of massive amounts of high-precision synchronous spatiotemporal data. However, how to extract "information" from this abundant data for accurate low-voltage fault diagnosis and achieve low-voltage distribution area fault detection has not been thoroughly researched. Summary of the Invention

[0006] This invention provides a method and system for detecting low-voltage distribution area faults based on the wide-area response of active distribution networks, which overcomes the shortcomings of the prior art and can effectively solve the problem of low detection efficiency of existing low-voltage distribution area fault detection methods that use local detection methods.

[0007] To address the aforementioned problems, one of the technical solutions of this invention provides a low-voltage distribution area fault detection method based on the wide-area response of an active distribution network, comprising:

[0008] The signal data on the active power distribution network line is collected and preprocessed. The collected signal data includes voltage and current signals at the grid connection points of each distributed power source on the active power distribution network line, as well as current signals at the outgoing lines of the low-voltage distribution area.

[0009] Determine whether more than 50% of the distributed power sources on the active distribution network line have voltage drop values ​​exceeding the limit at their grid connection points, and whether the current protection devices on the active distribution network line have not activated.

[0010] Therefore, it is determined that there is a low-voltage distribution area fault in the active distribution network.

[0011] Based on the low-voltage distribution area fault, calculate the proportion of voltage drop on each line, and determine the line with the highest proportion of voltage drop as the line where the low-voltage distribution area fault is located.

[0012] For the line where the fault is located in the low-voltage distribution area, the theoretical fault distance is determined based on the line's wide-area response parameters and their spatiotemporal distribution characteristics; among which, the line's wide-area response parameters include power jump rate, power fluctuation amplitude, voltage drop rate, and fault location parameters.

[0013] Based on the theoretical fault distance and the effective value of the current signal at the outgoing line of each low-voltage distribution area, the fault judgment index of each low-voltage distribution area is calculated; the distribution area with the largest fault judgment index is determined to be the faulty distribution area.

[0014] The above-mentioned collection of signal data from active power distribution network lines, and the preprocessing of the signal data, include:

[0015] The signal data is acquired by a synchronous phasor measurement device deployed at the grid connection point of the distributed power source and the outgoing line of the low-voltage distribution area, with a sampling frequency of not less than 4000 Hz;

[0016] The signal data is preprocessed, including: after each sampling, the instantaneous power value is calculated using the voltage signal sample value and current signal sample value of the latest power frequency cycle at the grid connection point of the distributed power source, and the effective voltage value is calculated using the voltage signal sample value of the latest power frequency cycle at the grid connection point of the distributed power source; therefore, a new instantaneous power value and effective voltage value are obtained after each sampling.

[0017] The above determination of whether more than 50% of the distributed power generation points on the active distribution network have voltage sag values ​​exceeding the limit includes:

[0018] For any distributed power source grid connection point, if the effective voltage value of the grid connection point satisfies the following formula, it is determined that the voltage drop value of the distributed power source grid connection point exceeds the limit; and the moment when the grid connection point first satisfies the following formula is recorded as the voltage drop moment. ,

[0019] In the formula, t For the current moment, j The index in the accumulation operation. The time interval between two samples; m The total number of samples within one power frequency cycle; They are respectively t The effective values ​​of phase A, phase B, and phase C voltages obtained at each moment; They are respectively The effective values ​​of phase A, phase B, and phase C voltages obtained at each moment; This is an operation to find the minimum value of the data within the parentheses; The rated voltage at the grid connection point, This is the voltage threshold coefficient.

[0020] The above-mentioned method, for the line where a fault occurs in a low-voltage distribution area, determines the theoretical fault distance based on the line's wide-area response parameters and their spatiotemporal distribution characteristics. These line wide-area response parameters include power jump rate, power fluctuation amplitude, voltage sag rate, and fault location parameters, including:

[0021] For the distributed power supply grid connection point on the line where the low-voltage distribution area fault occurs, the power jump rate is calculated using the following formula. D P :

[0022] ,

[0023] In the formula, For the instantaneous power of distributed power generation at the grid connection point Time's up The maximum value between time points; For the instantaneous power of distributed power generation at the grid connection point Time's up The minimum value between time points; The voltage drop times recorded in the aforementioned steps; This refers to the rated power of the distributed power source.

[0024] Using the Fourier transform algorithm Time's up The instantaneous power data of the distributed power source grid connection point between different times is processed to determine the dominant frequency of the data and calculate the amplitude at this dominant frequency. Z P The power fluctuation amplitude is calculated using the following formula. FP :

[0025] ,

[0026] Voltage sag rate D U The calculation equation is as follows:

[0027] ,

[0028] In the formula, These are the distributed power generation grid connection points. The effective values ​​of phase A, phase B, and phase C voltages obtained at each moment;

[0029] Fault location parameters W The calculation equation is as follows:

[0030] ,

[0031] In the formula, These are the conversion factors for power jump rate, power fluctuation amplitude, and voltage drop rate, respectively.

[0032] The least squares method is used to fit the polynomial and solve for the parameters of the constant term, the first term, and the second term.

[0033] ,

[0034] In the formula, x This refers to the electrical distance data between each distributed power supply grid connection point on the line where a low-voltage distribution fault occurs and the beginning of the line. y For fault location parameter data of each distributed power supply grid connection point on the line where the fault occurs in the low-voltage distribution area; These are the constant term parameters, linear term parameters, and quadratic term parameters, respectively.

[0035] The fitted curve is a parabola. The value of the independent variable corresponding to the highest point of the parabola is the theoretical fault distance. Based on the relationship between the highest point of the parabolic function and the parameters of the first and second terms, the theoretical fault distance is calculated using the following formula:

[0036] ,

[0037] In the formula, L G Theoretical fault distance;

[0038] in The calculation method is as follows:

[0039] ,

[0040] In the formula, For matrix Transpose of; for The inverse matrix;

[0041] matrix The value can be:

[0042] ,

[0043] In the formula, W 1. W 2. W 3、…、 W v These are the 1st, 2nd, 3rd, ..., on the line where the low-voltage distribution area fault is located. v Fault location parameters obtained from the grid connection points of distributed power sources; v The total number of distributed power supply grid connection points on the line where the low-voltage distribution area fault occurs;

[0044] matrix The value can be:

[0045] ,

[0046] In the formula, L 1. L 2. L 3、…、 L v These are the 1st, 2nd, 3rd, ..., on the line where the low-voltage distribution area fault is located. v Electrical distance between the grid connection point of a distributed power source and the beginning of the line.

[0047] Based on the theoretical fault distance and the effective value of the current signal at the outgoing line of each low-voltage distribution area, the fault judgment indicators for each low-voltage distribution area are calculated, including:

[0048] The calculation equations for the fault determination indicators are as follows:

[0049] ,

[0050] In the formula, S k The fault occurred on the line in the low-voltage distribution area. k Fault determination indicators for each low-voltage distribution area. Q k The fault occurred on the line in the low-voltage distribution area. k Electrical distance between each low-voltage distribution area and the beginning of the line; I k The fault occurred on the line in the low-voltage distribution area. k The effective value of the current signal at the outgoing line of each low-voltage distribution area; k For serial numbers; IN This refers to the rated current of the distribution transformer in the substation area. These are the first and second converted contribution coefficients, respectively.

[0051] The second technical solution of this invention is achieved through the following method: a low-voltage distribution area fault detection system based on the wide-area response of an active distribution network, wherein the system uses a low-voltage distribution area fault detection method based on the wide-area response of an active distribution network, comprising:

[0052] The data acquisition and processing unit acquires signal data from the active power distribution network lines and preprocesses the signal data. The acquired signal data includes voltage and current signals at the grid connection points of each distributed power source on the active power distribution network lines, as well as current signals at the outgoing lines of the low-voltage distribution area.

[0053] The voltage over-limit judgment unit determines whether more than 50% of the distributed power supply grid connection points on the active distribution network line have voltage drop values ​​exceeding the limit, and whether the current protection device on the active distribution network line has not been activated.

[0054] The response unit responds, and if so, it is determined that there is a low-voltage distribution area fault in the active distribution network;

[0055] The fault line determination unit calculates the voltage drop ratio of each line based on the low-voltage distribution area fault, and determines the line with the highest voltage drop ratio as the line where the low-voltage distribution area fault is located.

[0056] The fault distance calculation unit determines the theoretical fault distance for the line where the fault is located in the low-voltage distribution area based on the line's wide-area response parameters and their spatiotemporal distribution characteristics. Among them, the line's wide-area response parameters include power jump rate, power fluctuation amplitude, voltage drop rate, and fault location parameters.

[0057] The fault area determination unit calculates the fault judgment index for each low-voltage distribution area based on the theoretical fault distance and the effective value of the current signal at the outgoing line of each low-voltage distribution area; the distribution area with the largest fault judgment index is determined to be the faulty distribution area.

[0058] The aforementioned data acquisition and processing unit includes:

[0059] The data acquisition module acquires the signal data through a synchronous phasor measurement device deployed at the grid connection point of the distributed power supply and the outgoing line of the low-voltage distribution area, with a sampling frequency of not less than 4000 Hz;

[0060] The data processing module preprocesses the signal data, including: after each sampling, calculating the instantaneous power value using the voltage signal sampling value and current signal sampling value of the latest power frequency cycle at the grid connection point of the distributed power source, and calculating the effective voltage value using the voltage signal sampling value of the latest power frequency cycle at the grid connection point of the distributed power source; therefore, a new instantaneous power value and effective voltage value are obtained after each sampling.

[0061] This invention uses the wide-area response of an active distribution network containing distributed power sources to sense low-voltage distribution area faults. By constructing fault detection criteria through wide-area response parameters and their spatiotemporal distribution characteristics, it achieves effective low-voltage distribution area fault detection and location, thereby improving the efficiency of fault detection. Attached Figure Description

[0062] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0063] Figure 1 This is a flowchart of the method in Embodiment 1 of the present invention.

[0064] Figure 2 This is a block diagram of the device structure in Embodiment 2 of the present invention.

[0065] Figure 3 This is a structural block diagram of the data acquisition and processing unit in Embodiment 2 of the present invention.

[0066] Figure 4 This is a topology diagram of line 1 in embodiment 3 of the present invention.

[0067] Figure 5 This is a fault location parameter diagram of each distributed power source grid connection point on line 1 in Embodiment 3 of the present invention.

[0068] Figure 6 This is a fault determination index diagram for each low-voltage distribution area on line 1 in Embodiment 3 of the present invention. Detailed Implementation

[0069] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0070] Example 1: As Figure 1 As shown in the figure, this invention discloses a low-voltage distribution area fault detection method based on the wide-area response of an active distribution network, comprising:

[0071] Step S101: Collect signal data from the active power distribution network line and preprocess the signal data; wherein, the collected signal data includes voltage signals and current signals at the grid connection points of each distributed power source on the active power distribution network line, as well as current signals at the outgoing lines of the low-voltage distribution area.

[0072] Step S102: Determine whether there are more than 50% of the distributed power sources connected to the grid on the active distribution network line whose voltage drop value exceeds the limit, and whether the current protection device on the active distribution network line has not been activated.

[0073] Step S103, if the response is as follows, it is determined that there is a low-voltage distribution area fault in the active distribution network;

[0074] Step S104: Based on the low-voltage distribution area fault, calculate the voltage drop ratio of each line, and determine the line with the highest voltage drop ratio as the line where the low-voltage distribution area fault is located.

[0075] Step S105: For the line where the fault is located in the low-voltage distribution area, determine the theoretical fault distance based on the line's wide-area response parameters and their spatiotemporal distribution characteristics; wherein, the line's wide-area response parameters include power jump rate, power fluctuation amplitude, voltage drop rate, and fault location parameters.

[0076] Step S106: Based on the theoretical fault distance and the effective value of the current signal at the outgoing line of each low-voltage distribution area, calculate the fault judgment index for each low-voltage distribution area; the distribution area with the largest fault judgment index is determined to be the faulty distribution area.

[0077] In step S101 above, signal data from the active distribution network lines is collected, and the signal data is preprocessed, including:

[0078] The signal data is acquired by a synchronous phasor measurement device deployed at the grid connection point of the distributed power source and the outgoing line of the low-voltage distribution area, with a sampling frequency of not less than 4000 Hz;

[0079] The signal data is preprocessed, including: after each sampling, the instantaneous power value is calculated using the voltage signal sample value and current signal sample value of the latest power frequency cycle at the grid connection point of the distributed power source, and the effective voltage value is calculated using the voltage signal sample value of the latest power frequency cycle at the grid connection point of the distributed power source; therefore, a new instantaneous power value and effective voltage value are obtained after each sampling.

[0080] In step S102 above, determining whether more than 50% of the distributed power generation grid connection points on the active distribution network line have voltage drop values ​​exceeding the limit includes:

[0081] For any distributed power source grid connection point, if the effective voltage value of the grid connection point satisfies the following formula, it is determined that the voltage drop value of the distributed power source grid connection point exceeds the limit; and the moment when the grid connection point first satisfies the following formula is recorded as the voltage drop moment. ,

[0082] In the formula, t For the current moment, j The index in the accumulation operation. The time interval between two samples; m The total number of samples within one power frequency cycle; They are respectively t The effective values ​​of phase A, phase B, and phase C voltages obtained at each moment; They are respectively The effective values ​​of phase A, phase B, and phase C voltages obtained at each moment; This is an operation to find the minimum value of the data within the parentheses; The rated voltage at the grid connection point, This is the voltage threshold coefficient.

[0083] In step S105 above, for the line where the low-voltage distribution area fault is located, the theoretical fault distance is determined based on the line's wide-area response parameters and their spatiotemporal distribution characteristics; wherein, the line's wide-area response parameters include power jump rate, power fluctuation amplitude, voltage drop rate, and fault location parameters; including:

[0084] For the distributed power supply grid connection point on the line where the low-voltage distribution area fault occurs, the power jump rate is calculated using the following formula. D P :

[0085] ,

[0086] In the formula, For the instantaneous power of distributed power generation at the grid connection point Time's up The maximum value between time points; For the instantaneous power of distributed power generation at the grid connection point Time's up The minimum value between time points; The voltage drop times recorded in the aforementioned steps; This refers to the rated power of the distributed power source.

[0087] Using the Fourier transform algorithm Time's up The instantaneous power data of the distributed power source grid connection point between different times is processed to determine the dominant frequency of the data and calculate the amplitude at this dominant frequency. Z P The power fluctuation amplitude is calculated using the following formula. F P :

[0088] ,

[0089] Voltage sag rate D U The calculation equation is as follows:

[0090] ,

[0091] In the formula, These are the distributed power generation grid connection points. The effective values ​​of phase A, phase B, and phase C voltages obtained at each moment;

[0092] Fault location parameters W The calculation equation is as follows:

[0093] ,

[0094] In the formula, These are the conversion factors for power jump rate, power fluctuation amplitude, and voltage drop rate, respectively.

[0095] The least squares method is used to fit the polynomial and solve for the parameters of the constant term, the first term, and the second term.

[0096] ,

[0097] In the formula, x This refers to the electrical distance data between each distributed power supply grid connection point on the line where a low-voltage distribution fault occurs and the beginning of the line. y For fault location parameter data of each distributed power supply grid connection point on the line where the fault occurs in the low-voltage distribution area; These are the constant term parameters, linear term parameters, and quadratic term parameters, respectively.

[0098] The fitted curve is a parabola. The value of the independent variable corresponding to the highest point of the parabola is the theoretical fault distance. Based on the relationship between the highest point of the parabolic function and the parameters of the first and second terms, the theoretical fault distance is calculated using the following formula:

[0099] ,

[0100] In the formula, L G Theoretical fault distance;

[0101] in The calculation method is as follows:

[0102] ,

[0103] In the formula, For matrix Transpose of; for The inverse matrix;

[0104] matrix The value can be:

[0105] ,

[0106] In the formula,W 1. W 2. W 3、…、 W v These are the 1st, 2nd, 3rd, ..., on the line where the low-voltage distribution area fault is located. v Fault location parameters obtained from the grid connection points of distributed power sources; v The total number of distributed power supply grid connection points on the line where the low-voltage distribution area fault occurs;

[0107] matrix The value can be:

[0108] ,

[0109] In the formula, L 1. L 2. L 3、…、 L v These are the 1st, 2nd, 3rd, ..., on the line where the low-voltage distribution area fault is located. v Electrical distance between the grid connection point of a distributed power source and the beginning of the line.

[0110] In step S106 above, based on the theoretical fault distance and the effective value of the current signal at the outgoing line of each low-voltage distribution area, the fault judgment index for each low-voltage distribution area is calculated, including:

[0111] The calculation equations for the fault determination indicators are as follows:

[0112] ,

[0113] In the formula, S k The fault occurred on the line in the low-voltage distribution area. k Fault determination indicators for each low-voltage distribution area. Q k The fault occurred on the line in the low-voltage distribution area. k Electrical distance between each low-voltage distribution area and the beginning of the line; I k The fault occurred on the line in the low-voltage distribution area. k The effective value of the current signal at the outgoing line of each low-voltage distribution area; k For serial numbers; I N This refers to the rated current of the distribution transformer in the substation area. These are the first and second converted contribution coefficients, respectively.

[0114] When a fault occurs in a low-voltage distribution area, the voltage disturbance caused by the fault will propagate upstream (active distribution network lines), thereby triggering a synchronous "wide-area response" with spatial distribution characteristics from numerous distributed power sources on the line. The technical solution of this invention can indirectly and accurately locate low-voltage distribution area faults that are difficult to detect by traditional protection devices by collecting and analyzing the signal data of these distributed power sources.

[0115] Compared with traditional methods, the method of the present invention has the following advantages:

[0116] High sensitivity and strong resistance to transition resistance: Traditional relay protection and fault detection in low-voltage distribution areas rely on the characteristic of a significant increase in current, which may fail for high transition resistance faults (such as conductor-to-tree discharge or poor contact). The method of this invention is based on sensitive parameters such as voltage dips and power fluctuations. Even if the fault current increases but does not exceed the fault detection threshold, it can effectively capture fault characteristics through the wide-area response of upstream distributed power sources, thus improving the ability to detect high-resistance faults.

[0117] Wide-area collaboration avoids "blind spots": Traditional relay protection and fault detection devices operate independently, and fault detection devices within low-voltage distribution areas may be incomplete or have limited performance. This invention utilizes a large number of distributed power sources on the line as natural fault sensors, forming a wide-area monitoring network. This eliminates "blind spots" caused by the failure or insufficient sensitivity of individual monitoring points, achieving collaborative diagnosis.

[0118] Dual verification: This invention employs a dual criterion mechanism; firstly, it determines the existence of a fault and the faulty line by the synchronicity of voltage drops, and then determines the precise fault point and faulty distribution area by multi-parameter fusion and spatiotemporal distribution characteristics; this cross-verification effectively avoids malfunctions caused by normal operations such as load switching and distributed power supply start-up and shutdown, and its reliability is far higher than that of a single signal criterion; in addition, the method of this invention can not only determine "whether there is a fault", but also combine the theoretical fault distance and the effective value of the current at the low-voltage distribution area's outgoing line to pinpoint the specific faulty distribution area.

[0119] Easy to implement: The method of this invention uses PMU (Synchronous Phasor Measurement Unit) data widely deployed at the grid connection point of distributed power sources to transform the response of distributed power sources on the distribution network line into a detector for detecting faults in low-voltage distribution areas. It eliminates the need to install high-performance fault recording or detection devices in each of the large and widely distributed low-voltage distribution areas, thus achieving monitoring of faults in low-voltage distribution areas at a lower cost and has good engineering application value.

[0120] In summary, the low-voltage distribution area fault detection method based on the wide-area response of an active distribution network disclosed in this invention senses low-voltage distribution area faults through the wide-area response of an active distribution network containing distributed power sources, and constructs fault detection criteria through wide-area response parameters and their spatiotemporal distribution characteristics, thereby achieving effective low-voltage distribution area fault detection and location, and improving the efficiency of fault detection.

[0121] Example 2: Figure 2 As shown, this embodiment of the invention discloses a low-voltage distribution area fault detection system based on the wide-area response of an active distribution network. The system uses a low-voltage distribution area fault detection method based on the wide-area response of an active distribution network, including:

[0122] The data acquisition and processing unit acquires signal data from the active power distribution network lines and preprocesses the signal data. The acquired signal data includes voltage and current signals at the grid connection points of each distributed power source on the active power distribution network lines, as well as current signals at the outgoing lines of the low-voltage distribution area.

[0123] The voltage over-limit judgment unit determines whether more than 50% of the distributed power supply grid connection points on the active distribution network line have voltage drop values ​​exceeding the limit, and whether the current protection device on the active distribution network line has not been activated.

[0124] The response unit responds, and if so, it is determined that there is a low-voltage distribution area fault in the active distribution network;

[0125] The fault line determination unit calculates the voltage drop ratio of each line based on the low-voltage distribution area fault, and determines the line with the highest voltage drop ratio as the line where the low-voltage distribution area fault is located.

[0126] The fault distance calculation unit determines the theoretical fault distance for the line where the fault is located in the low-voltage distribution area based on the line's wide-area response parameters and their spatiotemporal distribution characteristics. Among them, the line's wide-area response parameters include power jump rate, power fluctuation amplitude, voltage drop rate, and fault location parameters.

[0127] The fault area determination unit calculates the fault judgment index for each low-voltage distribution area based on the theoretical fault distance and the effective value of the current signal at the outgoing line of each low-voltage distribution area; the distribution area with the largest fault judgment index is determined to be the faulty distribution area.

[0128] like Figure 3 As shown, the above data acquisition and processing unit includes:

[0129] The data acquisition module acquires the signal data through a synchronous phasor measurement device deployed at the grid connection point of the distributed power supply and the outgoing line of the low-voltage distribution area, with a sampling frequency of not less than 4000 Hz;

[0130] The data processing module preprocesses the signal data, including: after each sampling, calculating the instantaneous power value using the voltage signal sampling value and current signal sampling value of the latest power frequency cycle at the grid connection point of the distributed power source, and calculating the effective voltage value using the voltage signal sampling value of the latest power frequency cycle at the grid connection point of the distributed power source; therefore, a new instantaneous power value and effective voltage value are obtained after each sampling.

[0131] As can be seen from the above, the working principle of this invention is divided into four logical levels, specifically including:

[0132] 1. Wide-area data perception and preprocessing: Real-time signal acquisition and rapid calculation of instantaneous power and voltage RMS values ​​provide a dynamic data foundation for subsequent analysis; this constitutes the "sensory system" of the entire method.

[0133] 2. Fault Existence and Preliminary Location: The method of this invention monitors whether the effective voltage value of each distributed power source grid connection point experiences an "over-limit" drop, and determines whether these drops are synchronous within a very short time window (i.e., originating from the same disturbance source); then, it constructs criteria to determine the existence of the fault; and through "voltage drop" and "the main protection of the line has not acted", it determines that the fault point is located in a certain low-voltage distribution area downstream, rather than the main line itself; by calculating the "proportion of voltage drops" of each line, the fault range can be initially locked onto the line with the highest proportion.

[0134] 3. Fault Distance Calculation Based on Multi-Parameter Fusion and Spatiotemporal Characteristics: For the line where the fault is located, this method does not rely on a single signal, but comprehensively extracts multiple "wide-area response parameters" for each distributed power source point: power jump rate reflects the severity of the power change at the moment of the fault; power fluctuation amplitude reflects the intensity of power oscillation caused by the fault; voltage drop rate directly reflects the severity of the voltage impact. The above three parameters are fused by weighting to form a comprehensive "fault location parameter (W)". This parameter can more comprehensively characterize the intensity of the fault impact on each observation point, and then spatiotemporal distribution fitting is performed. The impact intensity of the fault point shows a regular distribution in space. By performing a quadratic polynomial fitting on the fault location parameter of each distributed power source point and its electrical distance to the beginning of the line, a parabola is obtained. The electrical distance corresponding to the vertex of the parabola is the theoretical fault distance, because the vertex represents the location most severely affected, that is, the location closest to the actual fault point.

[0135] 4. Final fault location determination based on transformer current information: After obtaining the theoretical fault distance, the effective current value at the outgoing line of each low-voltage transformer on the line is used for calculation (because the current of the faulty transformer itself is usually significantly abnormal); a comprehensive index is constructed - the fault determination index, which considers both "the degree of proximity between the theoretical fault distance and the electrical distance of the transformer" and "the degree of abnormality of the current in the transformer". The transformer with the largest fault determination index is finally determined as the faulty transformer.

[0136] Example 3: This embodiment of the invention discloses an active distribution network comprising four lines, each with several distributed power sources and transformer substations. The topology of line 1 is as follows: Figure 4 As shown, the line contains 4 distributed power sources and 3 transformer substations. The distances of the 4 distributed power sources from the beginning of the line are 1 km, 4 km, 6 km, and 9 km, respectively; the distances of the 3 transformer substations from the beginning of the line are 2.5 km, 7 km, and 10 km, respectively. The low-voltage transformer substation fault occurred at transformer substation 2 of line 1.

[0137] Step 1: Data Acquisition and Preprocessing;

[0138] Signal acquisition devices are installed at each distributed power source grid connection point and low-voltage distribution area outgoing line on the active distribution network line to collect voltage and current signals at the grid connection point and current signals at the low-voltage distribution area outgoing line. Specifically, the acquisition of the signals is achieved by synchronous phasor measurement units deployed at the distributed power source grid connection point and low-voltage distribution area outgoing line, with a sampling frequency of not less than 4000 Hz.

[0139] The signal data is preprocessed, including: after each sampling, the instantaneous power value is calculated using the voltage signal sample value and current signal sample value at the grid connection point of the distributed power source, and the effective voltage value is calculated using the voltage signal sample value of the most recent power frequency cycle at the grid connection point of the distributed power source; therefore, a new instantaneous power value and effective voltage value are obtained after each sampling.

[0140] Step 2: Based on the voltage drop exceeding the limit at the grid connection point of the distributed power source and its synchronization, determine whether there is a low-voltage distribution area fault in the distribution network; then, based on the proportion of voltage drop at the grid connection point on each line, determine the line where the low-voltage distribution area fault is located.

[0141] For any distributed power source grid connection point, determine whether the voltage drop value of the distributed power source grid connection point exceeds the limit; and record the time of voltage drop.

[0142] Because there exist lines where over 50% of distributed power generation grid connection points exceed voltage sag limits, and the time difference between their voltage sags is less than [a certain value]. However, the current protection device of the line did not activate; therefore, it was determined that there was a low-voltage distribution area fault in the distribution network; and then, the line with the highest proportion of voltage drop was identified as the line where the low-voltage distribution area fault was located.

[0143] Step 3: For the line where the low-voltage distribution area fault is located, determine the theoretical fault distance based on the line's wide-area response parameters and their spatiotemporal distribution characteristics; the line's wide-area response parameters include power jump rate, power fluctuation amplitude, voltage drop rate, and fault location parameters;

[0144] For the distributed power supply grid connection points on the lines where the low-voltage distribution area fault occurs, calculate the power jump rate sequentially. D P Power fluctuation amplitude F P Voltage sag rate D U ; and then obtain the fault location parameters. W The fault location parameters of each distributed power source grid connection point on line 1 are displayed in Figure 5 In, such as Figure 5 The star symbol in the image is shown.

[0145] Using the electrical distance data from the grid connection points of each distributed power source on the line where the low-voltage distribution area fault occurs to the beginning of the line as independent variables, and the fault location parameter data of each distributed power source on the line where the low-voltage distribution area fault occurs as dependent variables, a polynomial fitting was performed; specifically, the least squares method was used for fitting, and the fitting results are as follows. Figure 5 As shown by the dashed line in the image;

[0146] Furthermore, the constant term, linear term, and quadratic term parameters of the fitted function were found to be 0.3265, 0.1930, and -0.0134, respectively; the theoretical fault distance was then calculated to be 7.2015 km.

[0147] Step 4: Based on the theoretical fault distance and the effective value of the current signal at the outgoing line of each low-voltage distribution area, calculate the fault judgment index for each low-voltage distribution area on Line 1, as follows: Figure 6 The bar chart shown indicates that area 2 was identified as the area where the fault occurred.

[0148] Example 3 demonstrates the effectiveness of the technical solution of the present invention.

[0149] Example 4: This embodiment of the invention discloses a storage medium storing a computer program that can be read by a computer. The computer program is configured to execute a low-voltage distribution area fault detection method based on the wide-area response of an active distribution network when it runs.

[0150] The aforementioned storage media may include, but are not limited to, USB flash drives, read-only memory, portable hard drives, magnetic disks, optical disks, and other media capable of storing computer programs.

[0151] Example 5: This embodiment of the invention discloses a terminal, including a processor, a memory, a communication interface, and one or more programs. The one or more programs are stored in the memory and configured to be executed by the processor. The programs include instructions for performing steps in the low-voltage distribution area fault detection method based on the wide-area response of active distribution networks.

[0152] Example 6: This embodiment of the invention discloses an electronic device, including a processor and a memory. The memory stores a computer program, which is loaded and executed by the processor to implement a low-voltage distribution area fault detection method based on the wide-area response of an active distribution network.

[0153] The aforementioned electronic device also includes transmission devices and input / output devices, wherein both the transmission devices and the input / output devices are connected to the processor.

[0154] The processor described above can be a central processing unit (CPU), a general-purpose processor, a digital signal processor (DSP), an ASIC, an FPGA, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. It can also be a combination that implements computational functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc. The memory can include, but is not limited to, various media capable of storing computer programs, such as USB flash drives, read-only memory, portable hard drives, magnetic disks, or optical disks.

[0155] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0156] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0157] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0158] This application also provides a computer program product, which includes a non-transitory computer-readable storage medium storing a computer program operable to cause a computer to perform some or all of the steps of any of the methods described in the above method embodiments. The computer program product may be a software installation package, and the computer may include an electronic device.

Claims

1. A low-voltage transformer area fault detection method based on active power distribution network wide-area response, characterized in that, The method comprises the following steps: Collecting signal data on the active power distribution network line and pre-processing the signal data; wherein the collected signal data comprises voltage signals and current signals at each distributed power source grid-connected point on the active power distribution network line, and current signals at low-voltage transformer area outlets; Determining whether the voltage drop values of more than 50% of the distributed power source grid-connected points on the active power distribution network line are out of limits, and whether the current protection device on the active power distribution network line has not acted; In response to yes, it is determined that the active power distribution network has a low-voltage transformer area fault; On the basis of the low-voltage transformer area fault, the voltage drop quantity proportion of each line is calculated, and the line with the highest voltage drop quantity proportion is determined as the line on which the low-voltage transformer area fault occurs; For the line on which the low-voltage transformer area fault occurs, a theoretical fault distance is determined according to line wide-area response parameters and their space-time distribution characteristics; wherein the line wide-area response parameters comprise power jump rate, power fluctuation amplitude, voltage drop rate, and fault positioning parameters; According to the theoretical fault distance, in combination with the current signal effective values at the outlets of each low-voltage transformer area, fault determination indexes of each low-voltage transformer area are calculated; and the low-voltage transformer area with the largest fault determination index is determined as the transformer area in which the fault occurs.

2. The method for low voltage feeder fault detection based on active power distribution network wide area response according to claim 1, characterized in that, The collecting of the signal data on the active power distribution network line and the pre-processing of the signal data comprise: The signal data are collected by synchronous phasor measurement devices deployed at the distributed power source grid-connected points and the outlets of the low-voltage transformer areas, and the sampling frequency is not less than 4000 Hz; The pre-processing of the signal data comprises: after each sampling, an instantaneous power value is calculated by using the voltage signal sampling value and the current signal sampling value of the latest one power frequency cycle at the distributed power source grid-connected point, and a voltage effective value is calculated by using the voltage signal sampling value of the latest one power frequency cycle at the distributed power source grid-connected point; therefore, new instantaneous power values and voltage effective values are calculated after each sampling.

3. The method for low voltage feeder fault detection based on active power distribution network wide area response according to claim 1, characterized in that, The determination of whether the voltage drop values of more than 50% of the distributed power source grid-connected points on the active power distribution network line are out of limits comprises: For any distributed power source grid-connected point, if the voltage effective value of the grid-connected point satisfies the following formula, it is determined that the voltage drop value of the distributed power source grid-connected point is out of limits; and the time when the grid-connected point first satisfies the following formula is recorded as the voltage drop time; ， In the formula, t is the current time, j is the serial number in the cumulative operation, is the time interval between two samplings; m is the total number of samplings in one power frequency cycle; are respectively t the effective values of A-phase, B-phase and C-phase voltages obtained at the time t; are respectively the effective values of A-phase, B-phase and C-phase voltages obtained at the time t; is the operation for obtaining the minimum value of the data in the parentheses; is the rated voltage of the grid-connected point, is the voltage threshold coefficient.

4. The method for low voltage feeder fault detection based on active power distribution network wide area response according to claim 1, characterized in that, For the line on which the low-voltage transformer area fault occurs, a theoretical fault distance is determined according to line wide-area response parameters and their space-time distribution characteristics; wherein the line wide-area response parameters comprise power jump rate, power fluctuation amplitude, voltage drop rate, and fault positioning parameters; which comprises: For the low-voltage area fault line on the distributed power grid point, the power jump rate is calculated by the following formula D P : ， wherein, is the maximum value of the instantaneous power at the point of interconnection of the distributed power source between the time instant and the time instant ; is the minimum value of the instantaneous power at the point of interconnection of the distributed power source between the time instant and the time instant ; is the time instant of voltage sag recorded in the preceding step; is the rated power of the distributed power source; The Fourier transform algorithm is used to process the data of the power fluctuation amplitude of the distributed power grid-connected point between the time points The main frequency of the data is determined and the amplitude at the main frequency is calculated Z P The power fluctuation amplitude is calculated by the following formula F P :​ ， Voltage dip rate D U The calculation equation is as follows: ， In the formula, are the effective values of the A-phase, B-phase, and C-phase voltages at the grid-connected point of the distributed power source, respectively. are the effective values of the A-phase, B-phase, and C-phase voltages at the grid-connected point of the distributed power source, respectively. Fault location parameter W The calculation equation of the fault location parameter is as follows: ， In the formula, respectively, power jump rate, power fluctuation amplitude, voltage drop rate conversion coefficient; A least square method is used for polynomial fitting to solve constant term parameters, first-order term parameters, and second-order term parameters; ， In the formula, x The electrical distance data of each distributed power grid-connected point on the line from the line head for low-voltage transformer area fault; y The fault positioning parameter data of each distributed power grid-connected point on the line for low-voltage transformer area fault; The constant term parameter, the first term parameter, and the second term parameter, respectively; The fitted curve is a parabola, and the independent variable value corresponding to the highest point of the parabola is the theoretical fault distance; according to the relationship between the highest point of the parabola and the first-order term parameters and the second-order term parameters, the theoretical fault distance is calculated by using the following formula: ， In the formula, L G is the theoretical fault distance; wherein The calculation is as follows: ， wherein is the transpose of the matrix ; is the inverse matrix of ; matrix has a value of: ， In the formula, W 1. W 2. W 3、…、 W v These are the 1st, 2nd, 3rd, ..., on the line where the low-voltage distribution area fault is located. v Fault location parameters obtained from the grid connection points of distributed power sources; v The total number of distributed power supply grid connection points on the line where the low-voltage distribution area fault occurs; matrix has a value of: ， In the formula, L 1. L 2. L 3、…、 L v These are the 1st, 2nd, 3rd, ..., on the line where the low-voltage distribution area fault is located. v Electrical distance between the grid connection point of a distributed power source and the beginning of the line.

5. The method for low voltage feeder fault detection based on active power distribution grid wide area response according to claim 1, characterized in that, According to the theoretical fault distance, in combination with the current signal effective values at the outlets of each low-voltage transformer area, fault determination indexes of each low-voltage transformer area are calculated; and the low-voltage transformer area with the largest fault determination index is determined as the transformer area in which the fault occurs. The calculation equation of the fault determination index is as follows: ， In the formula, S k The fault occurred on the line in the low-voltage distribution area. k Fault determination indicators for each low-voltage distribution area. Q k The fault occurred on the line in the low-voltage distribution area. k Electrical distance between each low-voltage distribution area and the beginning of the line; I k The fault occurred on the line in the low-voltage distribution area. k The effective value of the current signal at the outgoing line of each low-voltage distribution area; k For serial numbers; I N This refers to the rated current of the distribution transformer in the substation area. These are the first and second converted contribution coefficients, respectively.

6. A low-voltage distribution area fault detection system based on active power distribution network wide-area response, the system using the low-voltage distribution area fault detection method based on active power distribution network wide-area response according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: The data acquisition and processing unit acquires signal data on the active power distribution network line and pre-processes the signal data; wherein the acquired signal data includes voltage signals and current signals at each distributed power source grid-connected point on the active power distribution network line, and current signals at low-voltage transformer area outgoing line points; The voltage out-of-limit judgment unit judges whether the voltage drop values of more than 50% of the distributed power source grid-connected points on the active power distribution network line are out of limit, and whether the current protection device on the active power distribution network line has not acted; The response unit responds to yes, and determines that the active power distribution network has a low-voltage transformer area fault; The fault line determination unit, on the basis of the low-voltage transformer area fault, calculates the voltage drop quantity proportion of each line, and determines the line on which the low-voltage transformer area fault occurs as the line with the highest voltage drop quantity proportion; The fault distance calculation unit, for the line on which the low-voltage transformer area fault occurs, determines the theoretical fault distance according to the line-wide response parameters and their space-time distribution characteristics; wherein the line-wide response parameters include power jump rate, power fluctuation amplitude, voltage drop rate, and fault positioning parameters; The fault transformer area determination unit, according to the theoretical fault distance, combines the current signal effective values at the outgoing line points of each low-voltage transformer area, calculates the fault determination index of each low-voltage transformer area, and determines the transformer area in which the fault occurs as the transformer area with the largest fault determination index.

7. The low voltage transformer area fault detection system based on active power distribution network wide area response according to claim 6, characterized in that, The data acquisition and processing unit comprises: The data acquisition module acquires the signal data through the synchronous phasor measurement device deployed at the distributed power source grid-connected point and the low-voltage transformer area outgoing line point, and the sampling frequency is not less than 4000 Hz; The data processing module pre-processes the signal data, including: after each sampling, the instantaneous power value is calculated through the latest one power frequency cycle voltage signal sampling value and current signal sampling value at the distributed power source grid-connected point, and the voltage effective value is calculated through the latest one power frequency cycle voltage signal sampling value at the distributed power source grid-connected point; therefore, new instantaneous power value and voltage effective value are obtained after each sampling.

Images