KR20090037549A - System for logging data of power line and method therefor - Google Patents

Abstract

A system for logging a data of power line and a method thereof are provided to reduce the capacitance burden of a memory by remarkably reducing electric power related data which are accumulated at a memory. A data logging system of an electric wire path includes a data logging device(100). The data logging device includes an A/D(Analog to Digital) converter(120), a discrete Fourier transform unit(140), a first buffer(150), a second buffer(160), a spectrum comparison unit(170), and a storage(180). The discrete Fourier transform unit performs discrete Fourier transform of electric power wave data, and creates electric power wave spectrum elements for each frequency. The storage stores the extracted electric power wave spectrum elements as data.

Description

System and method for data logging of power line {SYSTEM FOR LOGGING DATA OF POWER LINE AND METHOD THEREFOR}

The present invention belongs to a technique for efficiently and efficiently accumulating data related to power quality analysis, such as harmonics, voltage fluctuations, and frequency of power lines.

With the rapid progress of digital technology in the modern society, the use of high integration, multifunctionalization and miniaturized electric and electronic devices is on the rise. However, as this trend intensifies, electric and electronic devices are sensitive to power quality such as abnormal overvoltage, voltage fluctuations, instantaneous blackouts, and harmonics, such as lightning strikes and surges.

Therefore, it is necessary to monitor and analyze the power supply status for a long time in order to analyze the cause of the disturbance phenomenon caused by the electric environment of the power supply line supplying electric and electronic equipment and to design countermeasures. Implemented as a logging system.

In the related art, a conventional logging system stores power waveform-related data in a memory when an error occurs or continuously, but it is difficult to accumulate for a sufficient time due to the capacity limitation of the memory.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a main object of enabling a long-term accumulation (logging, logging) in memory by significantly reducing the amount or size of power waveform related data.

In addition, even if the power waveform is restored from the power waveform-related data accumulated in the memory for later quality analysis, it is intended to be restored within the allowable error range in preparation for the actual power waveform at the time of measurement.

In order to achieve the above technical problem, a system consisting of a data logging device and a waveform restoration device of the present invention is disclosed.

Specifically, the data logging device includes an A / D converter for sampling a power waveform of a power line and converting the power waveform to power waveform data, a discrete Fourier transformer for generating power waveform spectrum elements by frequency by performing discrete Fourier transform on the power waveform data; The first buffer for storing the power waveform spectral elements for each frequency, the second buffer for storing the reference waveform spectral elements for each frequency, and the power supply beyond the error range by comparing the magnitudes of the power waveform spectral elements and the reference waveform spectral elements for each frequency. A spectral comparator for extracting the waveform spectral elements and a storage for accumulating the extracted power waveform spectral elements.

The waveform restoring apparatus may further include a data readout unit for reading power waveform spectrum elements stored in the storage unit, a reference waveform information unit for storing reference frequency spectrum elements for each frequency, and reference waveform spectral elements of the reference waveform information unit. The inverse transform is performed, but the discrete Fourier inverse transform unit replaces the power waveform spectrum elements read through the data reader with reference waveform spectrum elements corresponding to frequencies.

On the other hand, the present invention is a method for logging the power waveform-related data of the power line, the first step of generating the power waveform data by setting the reference waveform spectrum element for the power line for each frequency and sampling the power waveform of the power line; A second process of generating power waveform spectral elements for each frequency by discrete Fourier transforming the power waveform data, and comparing the magnitudes of the power waveform spectral elements and the reference waveform spectral elements for each frequency and supplying power waveform spectral elements that deviate from the error range as data. The third step is to store.

In addition, the present invention is a waveform restoration method, the fourth process of reading the stored power waveform spectral elements through the third process, and performing the Fourier inverse transform of the reference waveform spectral elements, but corresponds to the read power waveform spectral elements by frequency A fifth process of inverse transformation by substituting with reference spectral components is described.

According to the present invention as described above, the capacity burden of the memory is significantly reduced by reducing the power waveform-related data accumulated in the memory at the time of monitoring the power line. In other words, even when a memory having the same capacity as in the prior art is used, power waveform-related data can be accumulated for a long time. In addition, it is possible to restore the actual power waveform at the time of measurement from the power waveform related data accumulated for power line quality analysis.

Therefore, the present invention can contribute to improving the reliability of power quality in response to the current situation where high quality power demand is required.

Specific features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. In the meantime, when it is determined that the detailed description of the known functions and configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, it should be noted that the detailed description is omitted.

1 is a block diagram of a data logging system of a power line according to the present invention. Referring to the drawings, a data logging system (hereinafter, referred to as a "logging system") of a power line includes a data logging device 100 and a waveform restoration device 200.

The logging device 100 may include a power waveform input unit 110, an A / D converter 120, a power waveform buffer 130, a Fourier transform unit 140, a first buffer 150, and a second buffer 160. ), The spectrum comparator 170 and the storage 180.

Specifically, the power waveform input unit 110 receives a power waveform (AC, AC) of the power line 10 to be monitored. The input power waveform is sampled through the A / D converter 120 and converted into a digital signal (power waveform data), and the A / D converted power waveform data is sequentially stored in the power waveform buffer 130. .

The discrete Fourier transform unit 140 receives power waveform data having a predetermined size from the power waveform buffer 130 and performs Discrete Fourier Transform to perform power frequency spectrum elements of the real part and the imaginary part on a first frequency basis. Stored in the buffer 150 (see FIG. 2). Here, the term 'constant size' means 2 ^N and corresponds to a size capable of constructing a reference waveform to be described below.

Hereinafter, a mathematical background will be described with respect to the discrete Fourier transform unit 140 of the present invention. Low voltage AC commercial power flows through the power line 10 mentioned in the present invention. Commercial power is a sinusoidal wave of 60 kHz frequency can be expressed as shown in Equation 1 below.

......................................... [수학식 1]

................................... Equation 1

V _m is the maximum value of the commercial power supply.

However, power sources used in homes and industrial sites include a number of harmonic components depending on the load and power environment, which can be expressed as follows.

........................... [수학식 2]

........................... [ Equation 2 ]

Where k is 1, 2, 3,... , Harmonics up to ∞.

Equation 2 is summarized as Equation 3 according to Euler's equation.

........................ [수학식 3]

..... [ Equation 3 ]

To simplify the above Equation 3, the complex constant is defined as follows.

와

는 복소공액(complex conjugate) 관계에 있다.here,

Wow

Is in a complex conjugate relationship.

Using the complex constant, Equation 3 may be expressed as follows.

............ [수학식 4]

[ Equation 4 ]

The Fourier transform equation of Equation 4 expressed as above is as follows.

...................................... [수학식 5]

............ [Equation 5]

However, since the discrete data (power waveform data) is acquired according to the sampling frequency of the A / D converter 120 of the present invention, the above-described continuous Fourier transform cannot be applied. Therefore, the following Discrete Fourier Transform should be used.

..................................... [수학식 6]

[ Equation 6 ]

For reference, the inverse conversion equation for [Equation 6] is as follows.

......................................... [수학식 7]

................................... [Equation 7]

In summary, since the power waveform data of the power waveform buffer 130 is converted into power waveform spectral elements by the discrete Fourier transform unit 140, analysis of power quality including harmonic components is possible.

Meanwhile, the second buffer 160 stores spectral components for each frequency of the reference power source. In this case, the 'reference power source' refers to a preferred power waveform of a power line or a power waveform that is a reference. For the sake of clarity of terminology herein, the 'spectral element' mentioned in the second buffer 160 is defined as a 'reference waveform spectral element' comprising a real part and an imaginary part (see FIG. 2).

The spectrum comparator 170 reads the 'reference waveform spectral component' and the 'power waveform spectral component' from the first and second buffers 150 and 160 described above for each frequency (which may be understood as a voltage value). In comparison, only the power waveform spectrum elements outside the error range are stored in the storage unit 180 (memory) as data. The storage unit 180 may include a function of recording data in a storage medium such as an SD card or a USB memory. In other words, it is possible to facilitate the maintenance by removing the storage medium. However, the present invention is not limited only to these examples.

Meanwhile, the waveform restoration apparatus 200 includes a data reader 210, a reference waveform information unit 220, and a discrete Fourier inverse transform unit 230 to read data stored in the storage unit 180 and restore the power waveform. do.

In detail, the data reader 210 reads the power waveform spectrum element stored in the storage 180. In this case, data movement between the storage 180 and the data reader 210 may be implemented through an information communication network (not shown) or through the aforementioned storage medium.

The reference waveform information unit 220 stores reference waveform spectrum elements for each frequency. Of course, the reference waveform spectrum element at this time is the same as the reference waveform spectrum element stored in the second buffer 160 of the data logging apparatus 100.

According to a feature of the present invention, the discrete Fourier inverse transform unit 230 performs discrete Fourier inverse transform on the reference waveform spectral elements of the reference waveform information unit 220 and corresponds to the power waveform spectrum elements read through the data reader 210 for each frequency. The reference waveform is replaced with the spectral components to restore the power waveform in the time domain.

In order to clarify the technical spirit of the present invention described above, it will be described with reference to a number of exemplary drawings. 3 is an exemplary diagram of a power waveform V (t) which can be measured in a power line, and the power waveform is defined as follows.

............. [수학식 8]

............. [ Equation 8 ]

In order to perform discrete Fourier transform on the arbitrary power waveform with N = 1024 power waveform data (N / 2 real part and N / 2 imaginary part) at a sampling frequency of 10 kHz, and to check the magnitude By multiplying this by the conjugate complex number, data as shown in FIG. 4 can be obtained. In FIG. 4, the value of the Y-axis is the magnitude of the signal for each frequency, and the correlation with the voltage has the following meaning according to the complex constant defined above and the following equations.

The periodic function of amplitude A, frequency ω and phase θ is expressed by Equation (9).

............. [수학식 9]

............. [ Equation 9 ]

,

라 하면

가 되어, 푸리에 급수의 기본항이 됨을 알 수 있다. here,

,

If

It turns out that it becomes the basic term of Fourier series.

이므로, 그 공액 값과 곱해보면,

가 된다. 즉,

임을 알 수 있다.And in the Fourier transform

If you multiply by that conjugate,

Becomes In other words,

It can be seen that.

Using this, the Y-axis of FIG. 4 is changed to the amplitude of an arbitrary power supply waveform previously set, and the sampling period of the X-axis is calculated to be changed into a frequency domain (domain), as shown in FIG. 5.

로 가정하였다. 한편, 도 7은 오차 범위로써 설명의 편의상 상한(+10V)만을 가정하고 도 6과 같이 푸리에 변환된 기준파형에 적용한 후, 앞서 푸리에 변환된 전원파형과 마스크(중첩)하여 나타낸 도면이다. The Fourier transform of the reference waveform in the same manner as described above is shown in FIG. Where the reference waveform is

Assume that Meanwhile, FIG. 7 is a diagram illustrating a Fourier-converted power waveform and a mask (overlapping) after applying the Fourier-converted reference waveform as shown in FIG.

Referring to the enlarged part of FIG. 7, it can be seen that the magnitude of the power waveform spectral element for each frequency deviates from the magnitude of the reference waveform spectral element to which an error range is applied as mentioned above. That is, the spectral comparator 170 of the present invention compares and judges them, and stores the corresponding power waveform spectral elements that are out of the magnitude of the reference waveform spectral elements in the storage unit 180.

Thus, the amount of data stored in the storage unit 180 is significantly reduced. In addition, as described above, the Fourier inverse transform of the reference waveform spectrum elements, but by inverting the power waveform spectral elements of the storage unit 180 with the corresponding reference waveform elements corresponding to the frequency, and restores the power waveform in the time domain do. Of course, some difference (error) occurs between the restored power waveform and the power waveform at the time of measurement as illustrated in FIG. 8, but this falls within an error tolerance range.

Hereinafter, a data logging method (hereinafter, referred to as a 'logging method') of a power line according to the present invention will be summarized based on the above description. 9A and 9B are flowcharts illustrating the logging method of the present invention.

First, a reference waveform spectrum element for a power line to be measured is prepared for each frequency (S110). Spectral elements (including real and imaginary parts) with respect to the reference waveform can be provided by measuring the power waveform of the power line by discrete Fourier transform, or can also be provided through the virtual setting of the power waveform considered to be the most desirable. . The setting of the reference waveform may be accomplished through a 'user setting unit' (not shown in FIG. 1).

Subsequently, power waveforms of the power line are sampled to generate digitally converted power waveform data (S120), and power waveform data having a predetermined size are discretely Fourier-transformed to generate power waveform spectrum elements for each frequency (S130).

Next, the magnitude (voltage value) of the power waveform spectral element generated in step S130 is compared with the magnitude of the reference waveform spectral element corresponding to each frequency (S140), and the corresponding power waveform spectral element out of the error range is used as data. Output or store (S150, S160).

The following is the process of restoring the power waveform by using the stored power waveform spectrum elements. First, the power waveform spectrum elements stored in step S160 are read (S170).

Subsequently, the Fourier Inverse Transform is performed on the reference spectral spectral elements, and the readout power spectral spectral elements are replaced with reference spectral spectral elements corresponding to frequencies, and then inversely transformed.

As described above and described with reference to a preferred embodiment for illustrating the technical idea of the present invention, the present invention is not limited to the configuration and operation as shown and described as described above, it is a deviation from the scope of the technical idea It will be understood by those skilled in the art that many modifications and variations can be made to the invention without departing from the scope of the invention. Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

1 is a schematic configuration diagram of a data logging system of a power line according to the present invention;

Figure 2 is an exemplary view showing the configuration of the power waveform spectral elements and reference waveform spectral elements used in the present invention,

3 to 8 are exemplary diagrams for further explaining the functions of the data logging system of the power line according to the present invention;

9A and 9B are flowcharts illustrating a data logging method of a power line according to the present invention.

** Description of symbols for the main parts of the drawing **

100: data logging device 110: power waveform input unit

120: A / D converter 130: power waveform buffer

140: Discrete Fourier Transform unit 150: First buffer

160: second buffer 170: spectrum comparison unit

180: storage unit 200: waveform restoration device

210: data reading unit 220: reference waveform information unit

230: discrete Fourier inverse transform unit

Claims (6)

This is a system that logs power waveform related data of power line. An A / D converter configured to sample the power waveform of the power line and convert the power waveform into power waveform data; A discrete Fourier transform unit for generating a power waveform spectrum element for each frequency by performing discrete Fourier transform on the power waveform data; A first buffer for storing the power waveform spectral components for each frequency; A second buffer for storing the reference waveform spectrum elements for each frequency; A spectrum comparator for extracting power waveform spectral elements that deviate from an error range by comparing the magnitudes of the power waveform spectral elements and reference waveform spectral elements for each frequency; And A storage unit for accumulating the extracted power waveform spectral elements as data; Power logging data logging system comprising a data logging device 100 configured. The method according to claim 1, The power waveform spectral element and the reference waveform spectral element, A power line data logging system comprising a real part and an imaginary part. The method according to claim 1, The data logging device, A power waveform buffer for storing the power waveform data; Data logging system of the power line further comprising a. The method according to claim 1, A data reading unit reading the power waveform spectrum element stored in the storage unit; A reference waveform information unit for storing reference frequency spectrum elements for each frequency; And A discrete Fourier inverse transform unit for inversely transforming reference waveform spectral elements of the reference waveform information unit by inverting power waveform spectral elements read through the data reader with the reference waveform spectral elements corresponding to frequencies; The data logging system of the power line, characterized in that it further comprises a waveform restoration device 200 configured. As a method of logging the power waveform related data of the power line, Setting a reference waveform spectrum element for the power line for each frequency, and generating power waveform data by sampling the power waveform of the power line; Generating a power waveform spectral component for each frequency by discrete Fourier transforming the power waveform data; And A third step of comparing the magnitudes of the power waveform spectral elements with the reference waveform spectral elements for each frequency and storing the power waveform spectral elements that deviate from an error range as data; Data logging method of the power line comprising a. The method according to claim 5, A fourth process of reading the stored power waveform spectral elements through the third process; And A fifth process of performing discrete Fourier inverse transform on the reference waveform spectral elements and replacing the read power waveform spectral elements with reference waveform spectral elements corresponding to frequencies for inverse transform; Data logging method of the power line further comprising a.

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