Method and device for suppressing periodic pulsating electromagnetic interference of a converter transformer

Abstract

The embodiment of the application provides a converter transformer periodic pulsation electromagnetic interference suppression method and device, and relates to the technical field of transformer monitoring. The method first detects a current signal at a core or a clamp grounding wire of a converter transformer by using a through-type high-frequency current sensor or a through-type ultrahigh-frequency current sensor, and performs filtering and smoothing processing on the current signal, then extracts all pulsation signals in the current signal as classified pulse signals, next extracts all pulse signals in one power frequency cycle in which no discharge pulse exists in the classified pulse signals as reference pulse signals, respectively calculates distances between the classified pulse signals and the reference pulse signals by using a dynamic time warping algorithm and obtains an optimal distance matrix, and finally removes interference signals by setting a distance threshold. The method can realize converter transformer periodic pulsation electromagnetic interference suppression, provides important support for converter transformer state evaluation, and has good practical value.

Description

Technical Field

[0001] This invention relates to the field of transformer monitoring technology, and more specifically, to a method and apparatus for suppressing periodic pulsating electromagnetic interference in converter transformers. Background Technology

[0002] Ultra-high voltage (UHV) converter transformers are critical equipment in converter stations, connecting DC and AC signals. Their reliable operation directly impacts the safe and stable operation of the power grid. Online partial discharge monitoring (live-line detection) can effectively diagnose the internal insulation condition of converter transformers. Currently, UHV and high-frequency methods are the main methods for monitoring internal discharges in converter transformers. However, converter stations differ from conventional AC stations in that the periodic switching on and off of the thyristors in the converter station generates electromagnetic transients with rise times in the microsecond range. These periodic pulsating electromagnetic transients are the main source of electromagnetic disturbance in converter stations, severely affecting online partial discharge monitoring (live-line detection) of converter transformers. Therefore, researching methods to suppress periodic pulsating electromagnetic interference in converter transformers is of great significance.

[0003] Currently, researchers mainly analyze the frequency domain characteristics of periodic pulsating interference and employ filters or frequency domain interference cancellation methods to eliminate it. This approach often requires high-speed sampling to acquire the original waveform, followed by bandpass filtering or spectral transformation to eliminate interference. However, most existing online monitoring (charge detection) technologies do not acquire the original signal; they primarily acquire detected signals. If the similarity of the detected signals is directly used for judgment, signal alignment issues arise. Dynamic time warping algorithms can effectively solve this problem, but no related reports have been found. Summary of the Invention

[0004] The present invention aims to provide a method and apparatus for suppressing periodic pulsating electromagnetic interference in converter transformers, which can suppress periodic pulsating electromagnetic interference in converter transformers, provide important support for the condition assessment of converter transformers, and has great practical value.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a method for suppressing periodic pulsating electromagnetic interference in a converter transformer, the method comprising:

[0007] S1: Use a through-type high-frequency current sensor or a through-type ultra-high-frequency current sensor to collect the current signal X(t) at the grounding wire of the core or clamp of the converter transformer.

[0008] S2: Filter and smooth the acquired current signal X(t) to remove noise interference from the signal;

[0009] S3: Extract all pulse signals from the current signal X(t), with each pulse signal having a pulse length of L1, ultimately obtaining M pulse signals to be classified;

[0010] S4: Extract all pulse signals within one power frequency cycle of the current signal X(t) where there is no discharge pulse. The pulse length of each pulse signal is L2, and finally N reference pulse signals are obtained.

[0011] S5: Compare the M pulse signals to be classified with the N reference pulse signals respectively, and use the dynamic time warping algorithm to obtain the DTW distance, resulting in an M*N DTW distance matrix;

[0012] S6: Select the minimum value of each row in the M*N DTW distance matrix as the optimal path distance for the M pulse signals to be classified, and obtain the optimal distance matrix;

[0013] S7: Set the optimal distance threshold d thres The optimal path distance in the optimal distance matrix is ​​compared with d. thres Comparing them one by one, if the optimal distance d of the m-th pulse signal to be classified... m Less than d thres If the m-th pulse signal to be classified is considered to be pulsating electromagnetic interference, then all pulsating electromagnetic interferences are obtained by comparing them one by one.

[0014] S8: Remove all pulsating electromagnetic interference from the acquired current signal to obtain the denoised discharge signal.

[0015] In an optional implementation, S2 includes:

[0016] The acquired current signal X(t) is filtered by an SG filter to remove noise interference.

[0017] In an optional implementation, in S3, the m-th pulse signal to be classified is denoted as:

[0018] pulse(m) = (x1, ..., x i ,…,x L1 )

[0019] In the formula, x i Let be the signal amplitude at the i-th sampling point.

[0020] In an optional implementation, in S4, the nth reference pulse signal is denoted as:

[0021] pulse(n) = (x1, ..., x j ,…,x L2 )

[0022] In the formula, x j Let be the signal amplitude at the j-th sampling point.

[0023] In an optional implementation, in S5, the m-th pulse signal to be classified, pulse(m), is defined as (x1, ..., x...). i ,…,x L1 ) and the nth reference pulse signal pulse(n)=(x1,…,x j ,…,x L2 The DTW distance calculation method is as follows:

[0024]

[0025]

[0026] max(L1,L2)≤s≤L1+L2

[0027] In the formula, D(i,j) represents x i With y j The Euclidean distance, where S represents the path length.

[0028] In an optional implementation, in S6, the optimal distance matrix is ​​denoted as:

[0029] d(M)=(d1,d2,…,d M )

[0030] In the formula, d M This is the distance of the Mth optimal path.

[0031] In an optional implementation, in S7, the optimal distance threshold d thres Set to 2.

[0032] Secondly, the present invention provides a device for suppressing periodic pulsating electromagnetic interference in a converter transformer. The device is used to perform the method described in the foregoing embodiments, and the device includes:

[0033] A through-hole high-frequency current sensor is used to collect the current signal X(t) at the grounding wire of the core or clamp of a converter transformer.

[0034] The processor is used to filter and smooth the acquired current signal X(t) to remove noise interference; extract all pulse signals from the current signal X(t), with each pulse signal having a pulse length of L1, resulting in M ​​pulse signals to be classified; extract all pulse signals within one power frequency cycle of the current signal X(t) where there is no discharge pulse, with each pulse signal having a pulse length of L2, resulting in N reference pulse signals; compare the M pulse signals to be classified with the N reference pulse signals, and use the dynamic time warping algorithm to calculate the DTW distance, resulting in an M*N DTW distance matrix; select the minimum value of each row in the M*N DTW distance matrix as the optimal path distance for the M pulse signals to be classified, resulting in the optimal distance matrix; and set the optimal distance threshold d. thres The optimal path distance in the optimal distance matrix is ​​compared with d. thres Comparing them one by one, if the optimal distance d of the m-th pulse signal to be classified... m Less than d thres If the m-th pulse signal to be classified is considered to be pulsating electromagnetic interference, then all pulsating electromagnetic interferences are obtained by comparing them one by one; after removing all pulsating electromagnetic interferences from the collected current signal, the denoised discharge signal is obtained.

[0035] The beneficial effects of the method and apparatus for suppressing periodic pulsating electromagnetic interference in converter transformers provided in this invention include:

[0036] First, a through-hole high-frequency current sensor (HFCT) or a through-hole ultra-high-frequency current sensor (UHFCT) is used to detect the current signal at the grounding wire of the converter transformer core or clamps. The current signal is then filtered and smoothed. Next, all pulsating signals in the current signal are extracted as the pulse signals to be classified. Then, all pulse signals within one power frequency cycle of the pulse signals to be classified, where there are no discharge pulses, are extracted as the reference pulse signals. A dynamic time warping algorithm is used to calculate the distance between the pulse signals to be classified and the reference pulse signals, obtaining the optimal distance matrix. Finally, interference signals are removed by setting a distance threshold. This method can suppress periodic pulsating electromagnetic interference in converter transformers, providing important support for converter transformer condition assessment and possessing significant practical value. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1A flowchart of a method for suppressing periodic pulsating electromagnetic interference in a converter transformer provided in an embodiment of the present invention;

[0039] Figure 2 The current signal acquired in this embodiment of the invention;

[0040] Figure 3 The optimal path distance of the pulse signal to be classified obtained in the embodiments of the present invention;

[0041] Figure 4 This is the denoised discharge signal according to an embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0044] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0045] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0046] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0047] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.

[0048] Please refer to Figure 1This embodiment provides a method for suppressing periodic pulsating electromagnetic interference in converter transformers (hereinafter referred to as the "method"), which includes the following steps:

[0049] S1: Use a through-hole high-frequency current sensor (HFCT) or a through-hole ultra-high frequency current sensor (UHFCT) to collect the current signal X(t) at the grounding wire of the core or clamp of the converter transformer.

[0050] The current signal collected in this embodiment is as follows: Figure 2 As shown, the acquired signal duration is 1s, the sampling rate is 1MS / s, there is a discharge pulse at 800ms, and the remaining time period is the periodic pulsation interference caused by the opening and closing of the converter valve.

[0051] S2: Filter and smooth the acquired current signal X(t) to remove noise interference from the signal.

[0052] In this embodiment, the acquired current signal X(t) is filtered using an SG filter to remove noise interference.

[0053] S3: Extract all pulse signals from the current signal X(t), with each pulse signal having a pulse length of L1, ultimately obtaining M pulse signals to be classified.

[0054] The m-th pulse signal to be classified is denoted as:

[0055] pulse(m) = (x1, ..., x i ,…,x L1 )

[0056] In the formula, x i Let be the signal amplitude at the i-th sampling point.

[0057] The M pulse signals to be classified here include periodic pulsating interference generated by the opening and closing of the converter valve, as well as discharge signals.

[0058] In this embodiment, the extracted pulse length L1 is 600, resulting in 632 pulses to be classified.

[0059] S4: Extract all pulse signals within one power frequency cycle of the current signal X(t) where there is no discharge pulse. The pulse length of each pulse signal is L2, and finally N reference pulse signals are obtained.

[0060] The nth reference pulse signal is denoted as:

[0061] pulse(n) = (x1, ..., x j ,…,x L2 )

[0062] In the formula, x jLet be the signal amplitude at the j-th sampling point.

[0063] In this embodiment, the extracted pulse length L2 is 600, and 12 reference pulse signals are finally obtained.

[0064] S5: Compare the M pulse signals to be classified with the N reference pulse signals respectively, and use the dynamic time warping algorithm to obtain the DTW distance, resulting in an M*N DTW distance matrix.

[0065] Wherein, the m-th pulse signal to be classified is pulse(m) = (x1,…,x i ,…,x L1 ) and the nth reference pulse signal pulse(n)=(x1,…,x j ,…,x L2 The DTW distance calculation method is as follows:

[0066]

[0067]

[0068] max(L1,L2)≤s≤L1+L2

[0069] In the formula, D(i,j) represents x i With y j The Euclidean distance, where S represents the path length.

[0070] In this embodiment, there are 632 pulse signals to be classified and 12 reference pulse signals, thus obtaining a 632*12 DTW distance matrix.

[0071] S6: Select the minimum value of each row in the M*N DTW distance matrix as the optimal path distance for the M pulse signals to be classified, and obtain the optimal distance matrix.

[0072] The optimal distance matrix is ​​denoted as:

[0073] d(M)=(d1,d2,…,d M )

[0074] In the formula, d M This is the distance of the Mth optimal path.

[0075] In this embodiment, an optimal distance matrix of 632*1 is obtained, where the optimal path distances of the 632 pulse signals to be classified are as follows: Figure 3 As shown, it can be seen that the DTW distance of the periodic interference pulse is very small, close to 0, while the DTW distance of the discharge pulse is very large, with a maximum value of nearly 170.

[0076] S7: Set the optimal distance threshold dthres The optimal path distance in the optimal distance matrix is ​​compared with d. thres Comparing them one by one, if the optimal distance d of the m-th pulse signal to be classified... m Less than d thres If the m-th pulse signal to be classified is considered to be pulsating electromagnetic interference, then all pulsating electromagnetic interferences are obtained by comparing them one by one.

[0077] In this embodiment, d thres The reason for setting it to 2 is that, from Figure 3 It can be seen that the DTW distance of the discharge signal is very large, exceeding 10, while the DTW distance of the interference signal is very small, less than 2. Therefore, d thres Setting it to 2 allows for a more accurate distinction between discharge signals and interference signals.

[0078] S8: Remove all pulsating electromagnetic interference from the acquired current signal to obtain the denoised discharge signal.

[0079] The denoising result in this embodiment is as follows: Figure 4 As shown in the figure, this method can accurately and effectively remove interference and extract the discharge signal.

[0080] This embodiment also provides a device for suppressing periodic pulsating electromagnetic interference of a converter transformer (hereinafter referred to as the "device"). The device is used to perform the above-described method and includes a through-hole high-frequency current sensor and a processor. The through-hole high-frequency current sensor can also be replaced by a through-hole ultra-high-frequency current sensor.

[0081] Specifically, the through-hole high-frequency current sensor is connected to the processor and is used to collect the current signal X(t) at the grounding wire of the core or clamp of the converter transformer.

[0082] The processor is used to execute S2 to S8 of the method.

[0083] The beneficial effects of the converter transformer periodic pulsating electromagnetic interference suppression method and device provided in this embodiment include:

[0084] First, a through-hole high-frequency current sensor (HFCT) or a through-hole ultra-high-frequency current sensor (UHFCT) is used to detect the current signal at the grounding wire of the converter transformer core or clamps. The current signal is then filtered and smoothed. Next, all pulsating signals in the current signal are extracted as the pulse signals to be classified. Then, all pulse signals within one power frequency cycle of the pulse signals to be classified, where there are no discharge pulses, are extracted as the reference pulse signals. A dynamic time warping algorithm is used to calculate the distance between the pulse signals to be classified and the reference pulse signals, obtaining the optimal distance matrix. Finally, interference signals are removed by setting a distance threshold. This method can suppress periodic pulsating electromagnetic interference in converter transformers, providing important support for converter transformer condition assessment and possessing significant practical value.

[0085] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for suppressing periodic pulsating electromagnetic interference in a converter transformer, characterized in that, The method includes: S1: Use a through-type high-frequency current sensor or a through-type ultra-high-frequency current sensor to collect the current signal X(t) at the grounding wire of the core or clamp of the converter transformer. S2: Filter and smooth the acquired current signal X(t) to remove noise interference from the signal; S3: Extract all pulse signals from the current signal X(t), with each pulse signal having a pulse length of L1, and finally obtain M pulse signals to be classified; S4: Extract all pulse signals within one power frequency cycle in the current signal X(t) where there is no discharge pulse. The pulse length of each pulse signal is L2, and finally N reference pulse signals are obtained. S5: Compare the M pulse signals to be classified with the N reference pulse signals respectively, and use the dynamic time warping algorithm to obtain the DTW distance, resulting in an M*N DTW distance matrix; S6: Select the minimum value of each row in the M*N DTW distance matrix as the optimal path distance for the M pulse signals to be classified, and obtain the optimal distance matrix; S7: Set the optimal distance threshold d thres The optimal path distance in the optimal distance matrix is ​​compared with d. thres Comparing them one by one, if the optimal distance d of the m-th pulse signal to be classified... m Less than d thres If the m-th pulse signal to be classified is considered to be pulsating electromagnetic interference, then all pulsating electromagnetic interferences are obtained by comparing them one by one. S8: Remove all pulsating electromagnetic interference from the acquired current signal to obtain the denoised discharge signal.

2. The method for suppressing periodic pulsating electromagnetic interference in a converter transformer according to claim 1, characterized in that, S2 include: The acquired current signal X(t) is filtered by an SG filter to remove noise interference.

3. The method for suppressing periodic pulsating electromagnetic interference in a converter transformer according to claim 2, characterized in that, In S3, the m-th pulse signal to be classified is denoted as: In the formula, x i Let be the signal amplitude at the i-th sampling point.

4. The method for suppressing periodic pulsating electromagnetic interference in a converter transformer according to claim 3, characterized in that, In S4, the nth reference pulse signal is denoted as: In the formula, x j Let be the signal amplitude at the j-th sampling point.

5. The method for suppressing periodic pulsating electromagnetic interference in a converter transformer according to claim 4, characterized in that, In S5, the m-th pulse signal to be classified With the nth reference pulse signal The DTW distance is calculated as follows: In the formula, D(i,j) represents x i With y j The Euclidean distance, where S represents the path length.

6. The method for suppressing periodic pulsating electromagnetic interference in a converter transformer according to claim 5, characterized in that, In S6, the optimal distance matrix is ​​denoted as: In the formula, d M This is the distance of the Mth optimal path.

7. The method for suppressing periodic pulsating electromagnetic interference in a converter transformer according to claim 1, characterized in that, In S7, the optimal distance threshold d thres Set to 2.

8. A device for suppressing periodic pulsating electromagnetic interference in a converter transformer, characterized in that, The apparatus is used to perform the method of claim 1, the apparatus comprising: A through-hole high-frequency current sensor is used to collect the current signal X(t) at the grounding wire of the core or clamp of a converter transformer. The processor is used to filter and smooth the acquired current signal X(t) to remove noise interference; extract all pulse signals from the current signal X(t), with each pulse signal having a pulse length of L1, resulting in M ​​pulse signals to be classified; extract all pulse signals within one power frequency cycle of the current signal X(t) where there is no discharge pulse, with each pulse signal having a pulse length of L2, resulting in N reference pulse signals; compare the M pulse signals to be classified with the N reference pulse signals, and use the dynamic time warping algorithm to calculate the DTW distance, resulting in an M*N DTW distance matrix; select the minimum value of each row in the M*N DTW distance matrix as the optimal path distance for the M pulse signals to be classified, resulting in the optimal distance matrix; and set the optimal distance threshold d. thres The optimal path distance in the optimal distance matrix is ​​compared with d. thres Comparing them one by one, if the optimal distance d of the m-th pulse signal to be classified... m Less than d thres If the m-th pulse signal to be classified is considered to be pulsating electromagnetic interference, then all pulsating electromagnetic interferences are obtained by comparing them one by one; after removing all pulsating electromagnetic interferences from the collected current signal, the denoised discharge signal is obtained.

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