Efficient fault positioning method and device for double-H wiring high-voltage filter capacitor bank

Abstract

The invention discloses an efficient fault positioning method and device for a double-H wiring high-voltage filter capacitor bank, and belongs to the technical field of direct-current power transmission, and the method comprises the steps: collecting the waveform data of two cycles before and after the fault of the double-H wiring high-voltage filter capacitor bank; calculating a threshold value of breakdown of a capacitor element, and finding a moment corresponding to a sampling point of which the ratio of the unbalanced current to the total current is greater than the threshold value as a disturbance starting moment; performing first-layer wavelet decomposition on the branch current difference signals at different positions of the capacitor bank, and calculating an energy value according to a first-layer detail coefficient; obtaining an energy value threshold according to the average value and the standard deviation of the first-layer coefficient energy value sequence; according to the energy value and the energy value threshold value, the fault is determined to be located to the 1 / 3 area; and positioning the fault to a 1 / 6 area according to the sudden change direction of the pulse current difference value at the disturbance starting moment to obtain a bridge arm where the fault is located. According to the invention, the characteristic signal generated by the fault can be quickly captured, so that the fault bridge arm position can be quickly positioned.

Description

Technical Field

[0001] The present invention relates to the field of UHV DC transmission in power systems, and particularly to an efficient fault location method and device for a double-H connection high-voltage filter capacitor bank. Background Art

[0002] In actual engineering, the location and maintenance work for faults in the double-H connection high-voltage filter capacitor bank of a converter station mainly rely on manual operation. Technicians use a digital megger to detect the capacitance values of each arm capacitor bank one by one, and determine the specific arm position where the fault occurs by comparing the detected capacitance values, and then determine the faulty unit. This method requires technicians to use a digital megger to detect the capacitance values of each arm capacitor bank one by one, which is a time-consuming process. Especially when the number of capacitor banks is large, the detection work will become very cumbersome, resulting in low overall efficiency of fault location. In addition, due to the energy storage characteristics of capacitors, if the capacitors are not completely discharged before detection, there may be a release of residual charge during the detection process, posing a threat to the personal safety of inspection personnel.

[0003] In order to improve the maintenance efficiency and safety, existing methods propose to add current transformers at the high-voltage end of the double-H bridge, and determine the fault location by obtaining the quantitative relationship of the steady-state current before and after the fault. The principle of this method is based on the fact that the steady-state current will change before and after the fault, and the quantitative relationship of this change is used to infer the location of the fault. However, since this method requires adding current transformers at the high-voltage end of the double-H bridge, this not only involves the procurement cost of the current transformers themselves, but also includes the costs of installation, commissioning, and subsequent maintenance, which greatly increases the operation and maintenance costs of the entire system. In addition, due to the inherently dangerous high-voltage environment, adding equipment will further increase the complexity and uncertainty of the system, thus bringing certain safety risks. And the capacitor bank usually consists of multiple power capacitors, and the change in the steady-state current before and after the fault is small. In actual operation, factors such as the noise in the system and the measurement error of the current transformer itself are likely to interfere with this small change amount, resulting in inaccurate fault location.

[0004] Operating experience of power systems shows that identifiable pre-fault disturbance characteristics usually appear before a serious equipment fault occurs. When an electrical equipment is operating, its voltage and current waveform signals often generate transient disturbance phenomena with suddenness, periodicity, and reversibility. Compared with the steady-state signals that tend to be stable, have weak characteristics, and limited information after a fault, the transient disturbance signals have more prominent change characteristics and richer fault information, and have important research value in the field of fault diagnosis. Based on the current research status, this solution specifically proposes an efficient fault location method and device for a double-H connection high-voltage filter capacitor bank. Summary of the Invention

[0005] To solve the problem of rapid fault location of high-voltage filter capacitor banks with double H-bridge wiring, this solution proposes an efficient fault location method and device for high-voltage filter capacitor banks with double H wiring, which can quickly capture the characteristic signals generated by faults, thereby quickly locating the position of the faulty bridge arm, greatly shortening the time required for fault location, and significantly improving the efficiency of maintenance work.

[0006] To achieve the above invention purpose, the technical solution of the present invention is as follows: An efficient fault location method for high-voltage filter capacitor banks with double H wiring, comprising the following steps: Collect waveform data of two cycles before and after the fault of the high-voltage filter capacitor bank with double H wiring, and the waveform data includes the terminal voltage of the capacitor bank, the total current, two unbalanced currents, and the low-voltage terminal current; Calculate the threshold for breaking down one capacitor element according to the parameters of the capacitor bank, and find the corresponding moment of the sampling point where the ratio of the unbalanced current to the total current is greater than the threshold as the starting moment of the disturbance; Perform the first-layer wavelet decomposition on the branch current difference signals of the upper, middle, and lower parallel bridge arms of the capacitor bank respectively to obtain the corresponding first-layer detail coefficients, and then obtain the corresponding energy values according to the first-layer detail coefficients; Group the initial acquisition data of the three branch current difference signals, calculate the energy of the first-layer detail coefficients of each group of data respectively, and form their respective energy value sequences; then obtain their respective energy value thresholds according to the average value and standard deviation of the energy value sequences; Judge according to the magnitude relationship between the energy value and the energy value threshold to locate the fault to the 1 / 3 area; then locate the fault to the 1 / 6 area according to the mutation direction of the pulse current difference at the starting moment of the disturbance, and obtain the faulty bridge arm.

[0007] Preferably, the calculation formula for calculating the threshold for breaking down one capacitor element according to the parameters of the capacitor bank is as follows: ; In the formula, is the threshold for breaking down one capacitor element, is the number of series segments inside a single power capacitor unit, is the number of series-connected power capacitors in a single bridge arm.

[0008] Preferably, perform the first-layer wavelet decomposition on the branch current difference signals of the upper, middle, and lower parallel bridge arms of the capacitor bank respectively to obtain the corresponding first-layer detail coefficients, and the calculation formula is as follows: ; In the formula, represents the first-layer detail coefficient, n is the index of the detail coefficient, n =0, 1, 2, …,N / 2 - 1, where N is the total number of sampling points, is the branch current difference corresponding to a certain parallel bridge arm at the sampling point 2n, is the branch current difference corresponding to a certain parallel bridge arm at the sampling point 2n + 1.

[0009] Preferably, the respective corresponding energy values are obtained according to the first - layer detail coefficients, and the calculation formula is as follows: ; represents the energy value of the first - layer detail coefficients, represents the th detail coefficient after the decomposition of the branch current difference signal of a certain parallel bridge arm.

[0010] Preferably, the respective energy value thresholds are obtained according to the average value and standard deviation of the energy value sequence, and the calculation formula is as follows: ; In the formula, represents the energy value threshold, is the standard deviation of the energy value sequence, is the average value of the energy value sequence.

[0011] Preferably, the fault is located in the 1 / 3 region according to the magnitude relationship between the energy value and the energy value threshold, including: if the energy value of the first - layer detail coefficients of a certain parallel bridge arm is greater than its corresponding energy value threshold, and at the same time the energy values of the first - layer detail coefficients of the other two parallel bridge arms are less than or equal to the corresponding energy value thresholds, it is determined that the parallel bridge arm with the energy value greater than the corresponding energy value threshold has a fault.

[0012] Preferably, the fault is located in the 1 / 6 region according to the mutation direction of the pulse current difference at the starting moment of the perturbation, including: obtaining the average value of the current difference signal of the parallel bridge arm corresponding to the 1 / 3 region in the first two half - cycles before the moment; if at the moment point, the current difference is greater than the average value , then the bridge arm where the current mutation increases is the faulty bridge arm.

[0013] The present invention also proposes an efficient fault - location device for a double - H - connected high - voltage filter capacitor bank, which is characterized by including: A data acquisition module, configured to acquire the waveform data of the double - H - connected high - voltage filter capacitor bank in the first two half - cycles before and after the fault, and the waveform data includes the capacitor bank terminal voltage, total current, two unbalanced currents, and low - voltage terminal current; The first data processing module is configured to calculate the threshold for breaking down a capacitor element according to the capacitor bank parameters, and find the corresponding moment of the sampling point where the ratio of the unbalanced current to the total current is greater than the threshold as the starting moment of the disturbance; The second data processing module is configured to perform the first-layer wavelet decomposition on the branch current difference signals of the upper, middle, and lower parallel bridge arms of the capacitor bank respectively, obtain the corresponding first-layer detail coefficients respectively, and then calculate the energy values of the first-layer detail coefficients; The third data processing module is configured to group the initial acquisition data of the three branch current difference signals, calculate the energy of the first-layer detail coefficients of each group of data respectively, and form their respective energy value sequences; then calculate their respective energy value thresholds according to the average value and standard deviation of the energy value sequences; The judgment output module is configured to locate the fault to the 1 / 3 area according to the comparison between the energy value and the energy value threshold; then locate the fault to the 1 / 6 area according to the mutation direction of the pulse current difference at the starting moment of the disturbance, and obtain the faulty bridge arm.

[0014] Preferably, the judgment output module locates the fault to the 1 / 3 area according to the comparison between the energy value and the energy value threshold, which specifically includes: if the energy value of the first-layer detail coefficient of a certain parallel bridge arm is greater than its corresponding energy value threshold, and at the same time the energy values of the first-layer detail coefficients of the other two parallel bridge arms are both less than or equal to the corresponding energy value thresholds, it is determined that the parallel bridge arm with the energy value greater than the corresponding energy value threshold has a fault.

[0015] Preferably, the judgment output module locates the fault to the 1 / 6 area according to the mutation direction of the pulse current difference at the starting moment of the disturbance, including: obtaining the average value of the current difference signal of the parallel bridge arm corresponding to the 1 / 3 area in the two cycles before the moment ; if the current difference is greater than the average value at the moment point , the bridge arm where the current mutation increases is the faulty bridge arm.

[0016] In summary, the present invention has the following advantages: 1. This solution is based on the capture of transient disturbance signals and uses the pulse current generated during the fault for fault location. The pulse signal is relatively obvious, and there is no need to detect each bridge arm capacitor bank one by one. It can quickly capture the characteristic signals generated by the fault, thus quickly locating the position of the faulty bridge arm, greatly shortening the time required for fault location, and significantly improving the efficiency of the maintenance work.

[0017] 2. This solution adds current transformers at the low-voltage end to detect the pulse current, avoiding direct contact detection with the capacitors, reducing the safety risks brought by the release of the remaining charge of the capacitors, and providing a safer working environment for maintenance personnel.

[0018] 3. This solution adds a current transformer at the low-voltage end. The procurement, installation, and maintenance costs of the low-voltage end equipment are relatively low, which can effectively reduce the overall operation and maintenance costs of the system.

[0019] 4. The implementation of this solution can be operated at the low-voltage end. The low-voltage environment is relatively safe and stable. Adding a current transformer will not significantly increase the complexity and uncertainty of the system, reducing the potential safety hazards caused by the increase in equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the implementation flowchart of the present invention; Figure 2 is the wiring and internal structure schematic diagram of the double-H wiring high-voltage filtering capacitor bank. DETAILED DESCRIPTION OF THE INVENTION

[0021] To more clearly illustrate the present invention, the present invention will be further described below in conjunction with the preferred embodiments and the drawings. Those skilled in the art should understand that the specific content described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0022] Embodiment 1 The embodiment of the present invention provides an efficient fault location method for a double-H wiring high-voltage filtering capacitor bank. Assume that each arm of the double-H bridge is composed of N capacitor units connected in series. The capacitance value of the capacitor unit is C u , and there are m × n components in total inside the capacitor unit. First, m components are connected in parallel to form a parallel module, and then n parallel modules are connected in series, as shown in Figure 2 .

[0023] As shown in Figure 1 , the method specifically includes the following steps: Step 1: Collect the waveform data of two cycles before and after the fault of the double-H wiring high-voltage filtering capacitor bank, including: the terminal voltage u (t), the total current i (t), the unbalanced current i u0 of the upper H-bridge, the unbalanced current i d0 of the lower H-bridge, and the low-voltage end current i 5(t).

[0024] Combined with the attached Figure 2 , in actual engineering, the total voltage , the total current , and the unbalanced current of the upper H-bridge can be directly obtained and the unbalanced current of the lower H-bridge Waveform data. The low-voltage terminal current is measured by a current transformer added to the branch where C5 is located (the low-voltage terminal current can also be measured by adding a current transformer to the branch where C6 is located ).

[0025] Step 2: According to the parameters of the capacitor bank and calculate the threshold η for breaking down one capacitor element, and find i u0 (t) / i (t)>η or i d0 (t) / i (t)>η of the sampling points as the disturbance starting point, and the corresponding time t 0 is the disturbance starting moment.

[0026] Specifically, referring to Appendix Figure 2 This step is specifically carried out as follows: According to Kirchhoff's current law, the branch currents flowing through the C6, C4, C3, C2, and C1 bridge arms of the capacitor bank are respectively: , , , , .

[0027] Calculate the threshold η for breaking down one capacitor element according to the parameters of the capacitor bank: ;(1) In the formula, is the threshold for breaking down one capacitor element, is the number of series segments per unit inside a single power capacitor, is the number of series-connected power capacitors in a single bridge arm.

[0028] Finally, find or of the sampling points as the disturbance starting point, is the time (unit: ms), then the corresponding time is the disturbance starting moment.

[0029] Step 3: Use the Haar wavelet to perform the first-layer wavelet decomposition on the branch current difference signals of the upper, middle, and lower parallel bridge arms of the capacitor bank respectively, obtain the corresponding first-layer detail coefficients, and then calculate the corresponding energy values according to the first-layer detail coefficients.

[0030] The branch current difference signals of the upper, middle, and lower parallel bridge arms of the double H-bridge are respectively , and 。The discrete wavelet transform (DWT) is a discrete form of the wavelet transform and is applicable to the analysis of digital signals. In this embodiment, the Haar wavelet is used to process the current difference signal before and after 1 ms (i.e., ) of the disturbance starting moment 、 and to perform a one-scale (first layer) decomposition respectively, so as to obtain the detail coefficients (also known as high-frequency coefficients); where 、 、 、 、 and are the branch currents flowing through the bridge arms C1, C2, C3, C4, C5, and C6 respectively.

[0031] Taking as an example, let , where k is the sampling time point, k = 0, 1, 2, …, N − 1; N is the total number of sampling points within 2 ms.

[0032] Then the detail coefficient corresponding to the current difference signal can be calculated by the following formula (2): ; (2) where n is the index of the detail coefficient, n = 0, 1, 2, …, N / 2 − 1. is the branch current difference corresponding to the parallel bridge arms C1 and C2 at the sampling point 2n, is the branch current difference corresponding to the parallel bridge arms C1 and C2 at the sampling point 2n + 1.

[0033] The energy of the first-layer detail coefficient of the current difference signal is calculated according to the following formula (3): ; (3) Similarly, according to the above steps, the energies and of the first-layer detail coefficients of the current difference signals and can be calculated respectively.

[0034] Step 4: Group the initial data of the current difference signals at different positions (i.e., the data of two cycles before and after the fault), calculate the energy of the first-level detail coefficients for each group of data respectively, and form their respective energy value sequences; for each energy value sequence, calculate its average value and standard deviation respectively, so as to obtain the corresponding energy value threshold; based on the threshold judgment, locate the fault to the 1 / 3 area.

[0035] The specific operation process is as follows: First, divide the initial data of the current difference signals , and into 40 groups, and the total number of sampling points in each group is N , N where

[0036] is the total number of sampling points within 2 ms. Secondly, calculate the energy of the first-level detail coefficients for each group of data according to equations (2) and (3), and form the energy value sequence of the first-level detail coefficients. Taking as an example, its energy value sequence of the first-level detail coefficients is .

[0037] Then, calculate the mean value of the energy value sequence according to equation (4): ; (4) Calculate the standard deviation of the energy value sequence according to the following equation (5): ; (5) Then calculate the energy value threshold according to the following equation (6): ; (6) Similarly, the energy value thresholds and corresponding to and can be calculated respectively according to the above steps.

[0038] Based on the energy of the first-level detail coefficients of each current difference signal and their respective energy value thresholds, make the following judgments: If and then it is determined that there is a fault in arm C1 or C2; If and then it is determined that there is a fault in arm C3 or C4; If then it is determined that there is a fault in arm C5 or C6.

[0039] When a breakdown occurs in a capacitor element in the capacitor bank, the normal parallel elements and the capacitor banks of other bridge arms will quickly release charges to the fault point, forming a transient discharge current with high frequency, large amplitude and rapid attenuation. This transient process will exhibit significant pulse characteristics in the waveform of the current difference of the upper, middle and lower bridge arm branches of the double H-bridge. Then, the current differences of the upper, middle and lower bridge arm branches and will have a significant increase in the energy of the first-level detail coefficients. Calculate the relevant threshold according to the standard deviation of the energy of the first-level detail coefficients of the branch current difference before the fault. If a fault occurs in this bridge arm, the energy of the first-level detail coefficients of the corresponding branch current difference will exceed the threshold and thus be identified, and the fault will be located within a 1 / 3 range (that is, it is determined that the fault occurs in the upper, middle or lower bridge arm of the double H-bridge).

[0040] Step 5: Locate the fault to a 1 / 6 area according to the mutation direction of the pulse current difference at the starting moment of the disturbance, and obtain the faulty bridge arm.

[0041] Assume that it is determined according to Step 4 that there is a fault in bridge arm C1 or C2. The specific operation is as follows: First, calculate the current difference signal according to the following formula (7) at the average value of the first two cycles before the moment : ; (7) where N is the total number of sampling points within 2 ms.

[0042] Then, based on the value of the current difference signal at and the average value of the first two cycles before the moment at , make the following judgments: If , it is determined that there is a fault in bridge arm C1; If , it is determined that there is a fault in bridge arm C2.

[0043] Similarly, according to the above steps, the average values and corresponding to and can be calculated respectively, and the following judgments are made: If it is determined according to Step 4 that there is a fault in bridge arm C3 or C4, and , then it is determined that there is a fault in bridge arm C3, otherwise it is determined that there is a fault in bridge arm C4; If it is determined according to Step 4 that there is a fault in bridge arm C5 or C6, and , it is determined that there is a fault in bridge arm C5, otherwise it is determined that there is a fault in bridge arm C6.

[0044] According to Kirchhoff's Current Law (KCL), when a component breakdown fault occurs, the capacitor banks of other bridge arms in parallel with the faulty bridge arm branch will discharge to the breakdown component. Therefore, the pulse mutation direction of the waveform of the current difference of the upper, middle, and lower bridge arm branches of the double H-bridge depends on the position of the faulty bridge arm. Based on this, the fault location can be judged according to the positive or negative of the current difference of the bridge arm branch at the fault moment. To eliminate the influence of the initial current difference, the steady-state one-cycle average value of the current difference of the bridge arm branch before the fault is used as the positioning threshold, and the fault can be located within the 1 / 6 range.

[0045] Embodiment 2 Based on the same inventive concept, this embodiment provides an efficient fault location device for a double H-connected high-voltage filter capacitor bank, including a data acquisition module, a first data processing module, a second data processing module, a third data processing module, and a judgment output module.

[0046] The data acquisition module is configured to acquire waveform data of two cycles before and after the fault of the double H-connected high-voltage filter capacitor bank, and the waveform data includes the capacitor bank terminal voltage, the total current, two unbalanced currents, and the low-voltage terminal current; The first data processing module is configured to calculate the threshold for breaking down one capacitor element according to the capacitor bank parameters, and find the corresponding moment of the sampling point where the ratio of the unbalanced current to the total current is greater than this threshold as the starting moment of the disturbance; The second data processing module is configured to perform the first-layer wavelet decomposition on the branch current difference signals of the upper, middle, and lower parallel bridge arms of the capacitor bank respectively to obtain the corresponding first-layer detail coefficients, and then obtain the corresponding energy values according to the first-layer detail coefficients; The third data processing module is configured to group the initial acquisition data of the three branch current difference signals, calculate the energy of the first-layer detail coefficients of each group of data respectively, and form their respective energy value sequences; then calculate their respective energy value thresholds according to the average value and standard deviation of the energy value sequences; The judgment output module is configured to locate the fault to the 1 / 3 area according to the comparison between the energy value and the energy value threshold; and then locate the fault to the 1 / 6 area according to the pulse current difference mutation direction at the starting moment of the disturbance to obtain the faulty bridge arm.

[0047] Preferably, the first data processing module calculates the threshold for breaking down one capacitor element according to the capacitor bank parameters , and the calculation formula is as follows: ; In the formula , is the threshold for breaking down one capacitor element, is the number of series segments inside a single power capacitor unit. is the number of series-connected power capacitors in a single bridge arm.

[0048] Preferably, the second data processing module performs the first-layer wavelet decomposition on the branch current difference signals of the upper, middle, and lower parallel bridge arms of the capacitor bank to obtain the corresponding first-layer detail coefficients. The calculation formula is as follows: ; In the formula, represents the first-layer detail coefficient, is the index of the detail coefficient, n = 0, 1, 2, …, N N / 2−1, where N is the total number of sampling points, is the branch current difference corresponding to a certain parallel bridge arm at the sampling point 2n, is the branch current difference corresponding to a certain parallel bridge arm at the sampling point 2n + 1.

[0049] The second data processing module obtains the corresponding energy values according to the first-layer detail coefficients. The calculation formula is as follows: ; represents the energy value of the first-layer detail coefficient, represents the th detail coefficient after the decomposition of the branch current difference signal of a certain parallel bridge arm.

[0050] Preferably, the third data processing module calculates the respective energy value thresholds according to the average value and standard deviation of the energy value sequence. The calculation formula is as follows: ; In the formula, represents the energy value threshold, is the standard deviation of the energy value sequence, is the average value of the energy value sequence.

[0051] Further, the judgment output module locates the fault to the 1 / 3 region according to the judgment of the energy value and the energy value threshold, including: if the energy value of the first-layer detail coefficient of a certain parallel bridge arm is greater than its corresponding energy value threshold, and at the same time, the energy values of the first-layer detail coefficients of the other two parallel bridge arms are both less than or equal to the corresponding energy value thresholds, it is determined that the parallel bridge arm with the energy value greater than the corresponding energy value threshold has a fault.

[0052] Further, the judgment output module locates the fault to the 1 / 6 region according to the mutation direction of the pulse current difference at the starting moment of the disturbance, including: obtaining the average value of the current difference signal of the parallel bridge arm corresponding to the 1 / 3 region in the two weeks before the ; if the current difference is greater than the average value at the time point , then the arm where the current suddenly increases is the faulty arm.

[0053] The above are only the preferred embodiments of the present invention, and do not impose any formal limitations on the present invention. Any simple modifications and equivalent changes made to the above embodiments based on the technical essence of the present invention all fall within the protection scope of the present invention.

Claims

1. An efficient fault location method for a double-H connected high-voltage filter capacitor bank, characterized in that, It includes the following steps: Collect waveform data of two cycles before and after the failure of the double-H connected high-voltage filter capacitor bank. The waveform data includes the terminal voltage of the capacitor bank, the total current, two unbalanced currents, and the low-voltage terminal current; Calculate the threshold for breaking down one capacitor element according to the parameters of the capacitor bank, and find the corresponding moment of the sampling point where the ratio of the unbalanced current to the total current is greater than this threshold as the starting moment of the disturbance; Perform the first-layer wavelet decomposition on the branch current difference signals of the upper, middle, and lower parallel bridge arms of the capacitor bank respectively to obtain the corresponding first-layer detail coefficients, and then obtain the corresponding energy values according to the first-layer detail coefficients; Group the initial acquisition data of the three branch current difference signals, calculate the energy of the first-layer detail coefficients of each group of data respectively, and form their respective energy value sequences; then obtain their respective energy value thresholds according to the average value and standard deviation of the energy value sequences; Locate the fault to the 1 / 3 area according to the comparison between the energy value and the energy value threshold; then locate the fault to the 1 / 6 area according to the mutation direction of the pulse current difference at the starting moment of the disturbance to obtain the faulty bridge arm.

2. The high-efficiency fault location method for the double-H connection high-voltage filter capacitor bank according to claim 1, characterized in that, The calculation formula for calculating the threshold for breaking down one capacitor element according to the parameters of the capacitor bank is as follows: ； Wherein, is the threshold for breaking down a capacitor element, is the number of series segments within a single power capacitor unit, is the number of series-connected power capacitors within a single arm.

3. The high-efficiency fault location method for the double-H connection high-voltage filter capacitor bank according to claim 1, characterized in that, The formula for performing the first-layer wavelet decomposition on the branch current difference signals of the upper, middle, and lower parallel bridge arms of the capacitor bank respectively to obtain the corresponding first-layer detail coefficients is as follows: ； Wherein, represents the first layer of detail coefficients, n is the index of the detail coefficient, n = 0, 1, 2, …, N N / 2−1, where N is the total number of sampling points, is the branch current difference corresponding to a certain parallel bridge arm at the sampling point 2n, is the branch current difference corresponding to a certain parallel bridge arm at the sampling point 2n + 1.

4. The efficient fault location method for the double-H connection high-voltage filter capacitor bank according to claim 3, characterized in that, The formula for obtaining the corresponding energy value according to the first-layer detail coefficient is as follows: ； Represents the energy value of the first-level detail coefficients, indicating the th detail coefficient after the decomposition of the current difference signal of a certain parallel bridge arm branch.

5. The efficient fault location method for the double-H connection high-voltage filtering capacitor bank according to claim 4, wherein The formula for obtaining the respective energy value thresholds according to the average value and standard deviation of the energy value sequences is as follows: ； wherein, represents the energy value threshold, is the standard deviation of the energy value sequence, is the average value of the energy value sequence.

6. The high-efficiency fault location method for the double-H connection high-voltage filter capacitor bank according to claim 1, wherein Locating the fault to the 1 / 3 area according to the comparison between the energy value and the energy value threshold includes: if the energy value of the first-layer detail coefficient of a certain parallel bridge arm is greater than its corresponding energy value threshold, and the energy values of the first-layer detail coefficients of the other two parallel bridge arms are both less than or equal to the corresponding energy value thresholds, then it is determined that the parallel bridge arm with the energy value greater than the corresponding energy value threshold has a fault.

7. The high-efficiency fault location method for the double-H connection high-voltage filter capacitor bank according to claim 1, characterized in that Fault is located in the 1 / 6 area according to the mutation direction of the pulse current difference at the disturbance starting moment, including: obtaining the average value of the current difference signal of the corresponding parallel bridge arm in the 1 / 3 area in the first two cycles before the moment ; if at this current difference at the moment point is greater than the average value , then the bridge arm where the current mutation increases is the faulty bridge arm.

8. High-efficiency fault location device for double-H connection high-voltage filter capacitor bank, characterized in that, It includes: A data acquisition module configured to collect waveform data of two cycles before and after the failure of the double-H connected high-voltage filter capacitor bank. The waveform data includes the terminal voltage of the capacitor bank, the total current, two unbalanced currents, and the low-voltage terminal current; A first data processing module configured to calculate the threshold for breaking down one capacitor element according to the parameters of the capacitor bank, and find the corresponding moment of the sampling point where the ratio of the unbalanced current to the total current is greater than this threshold as the starting moment of the disturbance; A second data processing module configured to perform the first-layer wavelet decomposition on the branch current difference signals of the upper, middle, and lower parallel bridge arms of the capacitor bank respectively to obtain the corresponding first-layer detail coefficients, and then the energy value of the first-layer detail coefficients; A third data processing module configured to group the initial acquisition data of the three branch current difference signals, calculate the energy of the first-layer detail coefficients of each group of data respectively, and form their respective energy value sequences; then calculate their respective energy value thresholds according to the average value and standard deviation of the energy value sequences; The judgment output module is configured to determine the fault location in the 1 / 3 region according to the magnitude of the energy value and the energy value threshold; then, according to the mutation direction of the pulse current difference at the starting moment of the disturbance, the fault location is determined in the 1 / 6 region to obtain the faulty bridge arm.

9. The high-efficiency fault location device for the double-H connected high-voltage filter capacitor bank according to claim 8, wherein, The judgment output module determines the fault location in the 1 / 3 region according to the magnitude of the energy value and the energy value threshold, which specifically includes: if the energy value of the first-layer detail coefficient of a certain parallel bridge arm is greater than its corresponding energy value threshold, and at the same time the energy values of the first-layer detail coefficients of the other two parallel bridge arms are both less than or equal to the corresponding energy value thresholds, it is determined that the parallel bridge arm with the energy value greater than the corresponding energy value threshold has a fault.

10. The high-efficiency fault location device for the double-H connection high-voltage filter capacitor bank according to claim 8, characterized in that, The judgment output module locates the fault in the 1 / 6 area according to the mutation direction of the pulse current difference at the starting moment of the disturbance, including: obtaining the average value of the current difference signal of the corresponding parallel bridge arm in the 1 / 3 area in the first two half-cycles before the moment ; if at this current difference at the moment is greater than the average value , then the bridge arm where the current mutation increases is the faulty bridge arm.

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