阅读说明：本技术 一种行波波头标定方法、装置、终端以及介质 (Traveling wave head calibration method, device, terminal and medium ) 是由 张怿宁 方苏 国建宝 杨光源 于 2020-04-10 设计创作，主要内容包括：本发明公开了一种行波波头标定方法、装置、终端以及介质,该方法包括分析线路发生故障后的暂态过程,提取故障后合适时间窗内的MMC直流侧母线电压数据；对所提取到的电压数据进行相模变换,得到线模电压信号；对线模电压信号进行EMD分解,得到暂态行波信号中的IMF最高频分量；对所得到IMF最高频分量进行二阶差分,二阶差分的最大值点对应时刻即为行波波头到达时刻。由于零模信号衰减比较严重,所以本发明采用线模电压信号。之后对线模电压信号进行EMD分解得到暂态行波信号中的IMF高频分量,最后利用得到的IMF高频分量进行二阶差分,二阶差分的最大值点对应时刻即为行波波头到达时刻,从而能够准确地标定故障行波波头。(The invention discloses a traveling wave head calibration method, a traveling wave head calibration device, a traveling wave head calibration terminal and a traveling wave head calibration medium, wherein the method comprises the steps of analyzing a transient process after a line has a fault, and extracting MMC direct-current side bus voltage data in a proper time window after the fault; carrying out phase-mode conversion on the extracted voltage data to obtain a line-mode voltage signal; EMD decomposition is carried out on the line mode voltage signal to obtain the IMF highest frequency component in the transient traveling wave signal; and performing second-order difference on the obtained IMF highest frequency component, wherein the time corresponding to the maximum point of the second-order difference is the arrival time of the traveling wave head. Because the zero mode signal attenuation is serious, the invention adopts a line mode voltage signal. And then EMD decomposition is carried out on the line mode voltage signal to obtain an IMF high-frequency component in the transient traveling wave signal, second-order difference is carried out by using the obtained IMF high-frequency component, and the time corresponding to the maximum point of the second-order difference is the arrival time of the traveling wave head, so that the fault traveling wave head can be accurately calibrated.)

1. A traveling wave head calibration method is characterized by comprising the following steps:

analyzing a transient process after a line has a fault, and extracting MMC direct-current side bus voltage data in a proper time window after the fault;

carrying out phase-mode conversion on the extracted voltage data to obtain a line-mode voltage signal;

EMD decomposition is carried out on the line mode voltage signal to obtain the IMF highest frequency component in the transient traveling wave signal;

and performing second-order difference on the obtained IMF highest frequency component, wherein the time corresponding to the maximum point of the second-order difference is the arrival time of the traveling wave head.

2. The traveling wave head calibration method according to claim 1, wherein the formula of the second order difference is:

in the formula, h (n-1) represents the IMF component of the previous point, h (n) represents the IMF component of the calculation point, and h (n +1) represents the IMF component of the subsequent point.

3. The traveling wave head calibration method according to claim 1, wherein the formula of the phase-mode transformation is:

in the formula u⁺And u^-Respectively representing the positive and negative voltages of the line bus, u₁And u₀Representing the line mode voltage and the zero mode voltage signal, respectively.

4. The traveling wave head calibration method according to claim 1, wherein the suitable time window is 2 ms.

5. A traveling wave head calibration device is characterized by comprising:

the voltage data extraction module is used for analyzing a transient process after a line fails and extracting MMC direct-current side bus voltage data in a proper time window after the line fails;

the phase-mode conversion module is used for carrying out phase-mode conversion on the extracted voltage data to obtain a line-mode voltage signal;

the EMD decomposition module is used for performing EMD decomposition on the line mode voltage signal to obtain the IMF highest frequency component in the transient traveling wave signal;

and the second-order difference module is used for carrying out second-order difference on the obtained IMF highest frequency component, and the time corresponding to the maximum point of the second-order difference is the arrival time of the traveling wave head.

6. The traveling wave head calibration device according to claim 5, wherein the formula of the second order difference is:

in the formula, h (n-1) represents the IMF component of the previous point, h (n) represents the IMF component of the calculation point, and h (n +1) represents the IMF component of the subsequent point.

7. The traveling wave head calibration device according to claim 5 or 6, wherein the formula of the phase-mode transformation is as follows:

in the formula u⁺And u^-Respectively representing the positive and negative voltages of the line bus, u₁And u₀Representing the line mode voltage and the zero mode voltage signal, respectively.

8. The traveling wave head calibration method according to claim 5, wherein the suitable time window is 2 ms.

9. Travelling wave head calibration terminal comprising a memory, a processor and a computer program stored in said memory and executable on said processor, characterized in that said processor implements the steps of the method according to any of claims 1 to 4 when executing said computer program.

10. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 4.

Technical Field

The invention relates to the technical field of electric power, in particular to a method, a device, a terminal and a medium for calibrating a traveling wave head.

Background

Compared with alternating current transmission, the flexible direct current transmission line has the advantages of large transmission capacity, long transmission distance, convenience in power adjustment, easiness in power grid interconnection, small occupied area and the like, and the application prospect is more and more extensive. Because of the long distance of the dc transmission line, overhead lines are often used. The overhead line passes through different climates and terrain environments and is the element with the highest fault rate in the direct current transmission system. The transient traveling wave signal generated after the line is in fault is a sudden change and singular signal and contains a lot of fault information. The fault traveling wave is utilized for positioning, the influence of a system operation mode and transition resistance is small, the positioning precision is high, and certain advantages are achieved. However, accurate calibration of a fault traveling wave head is a key point of traveling wave method distance measurement and is also a difficult point, and if the fault occurs, the wave head cannot be successfully captured or does not exist at all, fault positioning fails, so that the method for accurately calibrating the traveling wave head in fault positioning has great significance in research.

At present, the traveling wave head identification method mainly comprises a derivative method, a wavelet transformation method, a mathematical morphology method and the like. The derivative method is sensitive to noise and is greatly influenced by the noise. The wavelet transform has good time-frequency localization performance, can give the frequency information of the traveling wave signal at the moment in any small time period, and when the mathematical morphology method and the wavelet transform method are applied to traveling wave head identification, the key point is that a proper 'base' is selected, and relatively speaking, the wavelet transform method is more mature than the mathematical morphology method. The paper "singular detection and processing with wavelets" by MALLAT S, HWANG W L et al demonstrates that the cubic B-spline function, when used as a basis function for wavelet changes, can effectively check out signal Singularity in the presence of noise, but may not detect a wave head in the case of weak faults such as high impedance. The paper of the swords et al, "transmission line single-ended traveling wave fault location based on wavelet transform technology", proposes to extract fault characteristics of fault traveling waves by using wavelet transform technology and eliminate the influence of traveling wave dispersion on location accuracy, but needs to select a proper wavelet basis and a proper decomposition scale according to the characteristics of traveling waves; zhaoyangli et al, the study of a traveling wave fault locating method of an HVDC transmission line based on wavelet modulus maximum theory, provides a traveling wave head extraction method based on wavelet modulus maximum by combining wavelet transformation according to singular points of fault traveling wave signals. However, the wavelet transform needs to consider the problems of the type of wavelet basis, the sampling rate of signals, the decomposition scale, the wide data window, the integration operation used in the operation, and the like, so that the wavelet transform has no self-adaptability, and cannot analyze all types of faults by using a family of wavelet bases. If proper basis functions and scales cannot be selected, the correct wave head time is difficult to obtain.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a traveling wave head calibration method, a traveling wave head calibration device, a traveling wave head calibration terminal and a traveling wave head calibration medium so as to accurately calibrate a fault traveling wave head.

In order to achieve the purpose, the technical scheme of the invention is as follows:

in a first aspect, an embodiment of the present invention provides a method for calibrating a traveling wave head, including:

analyzing a transient process after a line has a fault, and extracting MMC direct-current side bus voltage data in a proper time window after the fault;

carrying out phase-mode conversion on the extracted voltage data to obtain a line-mode voltage signal;

EMD decomposition is carried out on the line mode voltage signal to obtain the IMF highest frequency component in the transient traveling wave signal;

and performing second-order difference on the obtained IMF highest frequency component, wherein the time corresponding to the maximum point of the second-order difference is the arrival time of the traveling wave head.

In the method for calibrating a traveling wave head, the formula of the second-order difference is as follows:

in the formula, h (n-1) represents the IMF component of the previous point, h (n) represents the IMF component of the calculation point, and h (n +1) represents the IMF component of the subsequent point.

The traveling wave head calibration method further comprises the following formula:

in the formula u⁺And u^-Respectively represent positive and negative voltages of a line bus, and u1 and u0 respectively represent a line mode voltage signal and a zero mode voltage signal.

According to the method for calibrating the traveling wave head, the suitable time window is 2 ms.

In a second aspect, an embodiment of the present invention provides a traveling wave head calibration apparatus, including:

the voltage data extraction module is used for analyzing a transient process after a line fails and extracting MMC direct-current side bus voltage data in a proper time window after the line fails;

the phase-mode conversion module is used for carrying out phase-mode conversion on the extracted voltage data to obtain a line-mode voltage signal;

the EMD decomposition module is used for performing EMD decomposition on the line mode voltage signal to obtain the IMF highest frequency component in the transient traveling wave signal;

and the second-order difference module is used for carrying out second-order difference on the obtained IMF highest frequency component, and the time corresponding to the maximum point of the second-order difference is the arrival time of the traveling wave head.

In a third aspect, an embodiment of the present invention provides a traveling wave head calibration terminal, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, where the processor implements the steps of the traveling wave head calibration method described above when executing the computer program.

In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, where a computer program is stored, and when the computer program is executed by a processor, the steps of the traveling-wave head calibration method described above are implemented.

Compared with the prior art, the invention has the beneficial effects that:

the method extracts the voltage data of the direct-current side bus of the MMC by analyzing the transient process after the fault occurs in the line, selects a proper time window, intercepts the original signal, and performs phase-mode conversion processing. And then EMD decomposition is carried out on the line mode voltage signal to obtain an IMF high-frequency component in the transient traveling wave signal, second-order difference is carried out by using the obtained IMF high-frequency component, and the time corresponding to the maximum point of the second-order difference is the arrival time of the traveling wave head, so that the fault traveling wave head can be accurately calibrated.

Drawings

Fig. 1 is a flowchart of a method for calibrating a traveling wave head according to an embodiment of the present invention;

FIG. 2 is a diagram of an EMD decomposition process;

FIG. 3 is a three-terminal DC transmission line model diagram;

fig. 4 is a line mode voltage time variation diagram of the converter station 1;

fig. 5 is a time variation diagram of the high frequency component IMF1 of the line mode voltage of the converter station 1;

FIG. 6 is a second order differential time variation graph of the high frequency component IMF 1;

fig. 7 is a schematic composition diagram of a traveling wave head calibration apparatus according to an embodiment of the present invention;

fig. 8 is a schematic composition diagram of a traveling wave head calibration terminal according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and detailed description.