KR101042169B1 - Apparatus and method for detecting/tracing time-varying harmonic in the power system - Google Patents

Abstract

An apparatus and method for detecting and tracking time varying harmonics of a power signal are provided. An apparatus for detecting and tracking time varying harmonics of a power signal according to an embodiment of the present invention, the apparatus for detecting and tracking time varying harmonics of a power signal includes: a filter bank for decomposing harmonics of a power signal; And an adaptive predictor for processing each harmonic decomposed by the filter bank to detect and track the frequency and amplitude of time-varying harmonics.

In addition, the time-varying harmonic detection and tracking method of the power signal according to another embodiment of the invention, in the time-varying harmonic detection and tracking method applied to the time-varying harmonic detection and tracking device of the power signal, using a filter bank harmonics of the power signal Harmonic decomposition step of decomposing; And an adaptive prediction step for detecting and tracking the frequency and amplitude of time-varying harmonics by processing each harmonic decomposed through the harmonic decomposition step.

Time-varying harmonics, detection, tracking, filterbanks, harmonic decomposition, adaptive prediction

Description

Apparatus and method for detecting / tracing time-varying harmonic in the power system}

The present invention relates to an apparatus and method for detecting and tracking time-varying harmonics of a power signal, and more particularly, to an apparatus and method for detecting and tracking time-varying harmonics of a power signal for accurately detecting and tracking harmonics, which are the most important factor in power quality measurement. It is about.

Due to the high use of nonlinear loads and time-varying loads in power systems, factors that reduce power quality such as sag, swell, harmonics, and transient noise have increased. Harmonic components cause many problems in the power system, such as echo, device failure, heat generation of electronic equipment, and reduced life of rotating machines.

In general, since harmonics in power systems have a characteristic that frequency and amplitude change with time, it is very difficult to accurately track and detect them.

Conventional methods based on Fourier transform are widely used to detect harmonics.In environments where the statistical properties of signals do not change over time, Fourier-based techniques are simple due to their simple structure and ease of implementation. While it can be used very usefully, the statistical characteristics of the signal change with time has a problem that the performance is degraded due to the spectral leakage effect (aliasing effect) and aliasing (aliasing effect) in the environment.

To remedy this problem, techniques based on wavelet transform, which have problems in actual implementation but have high performance, digital filtering techniques, enhancement phase-locked loop (EPLL) techniques, and adaptive notch filtering techniques ( Adaptive notch filtering has been studied for time-varying harmonic analysis.

Looking at the recent domestic patents related to power quality, most of them apply FFT (Fast Fourier Transform) to power signal and its harmonic measurement, and some methods have been found to measure frequency using cosine filter and sine filter. . However, in this method, if the frequency and amplitude of the fundamental wave changes with time, there is a problem that an error occurs because the spectral leakage is inevitable in each harmonic measurement, thereby affecting accuracy.

An object of the present invention is to provide an apparatus and method for detecting and tracking time-varying harmonics of a power signal for accurately detecting and tracking harmonics, which are the most important factors in power quality measurement.

In other words, the present invention proposes a method for solving the problems in the existing harmonic measurement, by decomposing harmonics whose characteristics (frequency and amplitude) change with time using a filter bank, and decomposing the decomposed harmonics into an adaptive predictor. It is an object of the present invention to provide an apparatus and method for detecting and tracking time-varying harmonics of a power signal that can more accurately measure the time-varying frequency and amplitude even under a noisy environment.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the time-varying harmonic detection and tracking device of the power signal according to an embodiment of the present invention, the time-varying harmonic detection and tracking device of the power signal, the filter bank for decomposing harmonics of the power signal; And an adaptive predictor for processing each harmonic decomposed by the filter bank to detect and track the frequency and amplitude of time-varying harmonics.

The filter bank may include a basic filter bank (FB) including a band stop filter (BRF), a band pass filter (BPF), a low pass filter (LPF), and a high pass filter (HPF). However, more preferably, such a basic filter bank may be applied in stages and successively so as to be able to decompose a plurality of higher harmonics.

In this case, the adaptive predictor may be configured to detect and track the frequency and amplitude of time-varying harmonics using an adaptive algorithm based on a Least Mean Square (LMS) algorithm.

On the other hand, the time-varying harmonic detection and tracking method of the power signal according to an embodiment of the invention, in the time-varying harmonic detection and tracking method applied to the time-varying harmonic detection and tracking device of the power signal, using a filter bank to the harmonics of the power signal A harmonic decomposition step of decomposing; And an adaptive prediction step for detecting and tracking the frequency and amplitude of time-varying harmonics by processing each harmonic decomposed through the harmonic decomposition step.

Here, the adaptive prediction step may be configured to detect and track the frequency and amplitude of time-varying harmonics using an adaptive algorithm based on a Least Mean Square (LMS) algorithm.

According to the apparatus and method for detecting and tracking time-varying harmonics of power signals of the present invention as described above, there is an advantage that the frequency and amplitude of time-varying harmonics can be more accurately tracked using a filter bank and an adaptive predictor.

This not only improves the accuracy of measuring the harmonics of the power signal, but also the measurement of total harmonics distortion, and also allows the basic filter bank to be applied continuously, thus simplifying the number of harmonics to be resolved. There are also a number of advantages, including the ability to change the design of the hardware.

An apparatus for detecting and tracking time varying harmonics of a power signal according to an embodiment of the present invention, the apparatus for detecting and tracking time varying harmonics of a power signal includes: a filter bank for decomposing harmonics of the power signal; And an adaptive predictor for processing each harmonic decomposed by the filter bank to detect and track the frequency and amplitude of time-varying harmonics.

In addition, the time-varying harmonic detection and tracking method of the power signal according to another embodiment of the invention, in the time-varying harmonic detection and tracking method applied to the time-varying harmonic detection and tracking device of the power signal, using a filter bank harmonics of the power signal Harmonic decomposition step of decomposing; And an adaptive prediction step for detecting and tracking the frequency and amplitude of time-varying harmonics by processing each harmonic decomposed through the harmonic decomposition step.

Specific details of other embodiments are included in the detailed description and the drawings.

Advantages and features of the present invention, and methods for achieving them will be apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Although the first, second, etc. are used to describe various elements, components or sections, these elements, components or sections are of course not limited by these terms. These terms are only used to distinguish one element, component or section from another element, component or section. Therefore, the first element, the first component, or the first section mentioned below may be a second element, a second component, or a second section within the technical spirit of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, the term "comprises" or "comprising" does not exclude the presence or addition of one or more other components, steps, operations or elements. . And "A or B" means A, B, A and B. In addition, like reference numerals refer to like elements throughout the following specification.
In addition, in the following description, the attenuation process (↓ 2) is performed in the signal attenuator, which will be omitted below.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is an explanatory view showing a structure of a basic filter bank applied to a time-varying harmonic detection and tracking device of a power signal according to an embodiment of the present invention, Figure 2a is a low pass filter (LPF) applied to the basic filter bank of FIG. 2B is a graph showing the frequency characteristics of the band stop filter (BRF) and the band pass filter (BPF) applied to the basic filter bank of FIG.

1 to 2B, a Fundamental Filter Bank (FB) applied to an apparatus for detecting and tracking time-varying harmonics of a power signal according to an embodiment of the present invention includes a band stop filter (BRF) and a band pass filter. (BPF), low pass filter (LPF), high pass filter (HPF) and the like. ↓ 2 means the process of canceling the signal.
That is, the filter bank includes a band pass filter for passing a specific band of the high band and the low band of the input power signal; A band blocking filter for blocking and passing a signal of a specific band passed through the band pass filter among the input power signals; A low pass filter for passing only the low pass signal among the signals passed through the band stop filter; A high pass filter for passing only a high pass signal among the signals passed through the band stop filter; And a basic filter bank including first and second signal attenuators which receive the output signals of the low pass filter and the high pass filter, respectively, and increase the bandwidth reduced in half to half before reducing. By separating the harmonics of the higher order and the harmonics of the even order, it is possible to resolve the higher order harmonics.

That is, in FIG. 1, X (n) is an input power signal, and H _BR (Z), H _BP (Z), H _LP (Z), and H _HP (Z) are respectively a band stop filter (BRF) and a band pass filter. (BPF), low pass filter (LPF) and high pass filter (HPF). Also, Y _L (n) is an odd harmonic signal output through the low pass filter, Y _H (n) is an odd harmonic signal output through the high pass filter, and Y _B (n) is an even harmonic output through the bandpass filter. Means signal.

The low pass filter LPF and the high pass filter HPF have a frequency characteristic as shown in FIG. 2A, and the band stop filter BRF and the band pass filter BPF have a frequency characteristic as shown in FIG. 2B.

The harmonic resolution characteristics of the basic filter bank having such a configuration are, for example, if the power signal includes only the third harmonic, the fundamental wave at the top output of the basic filter bank, the third harmonic at the second output, and the second harmonic at the last output. Are respectively disassembled and output. And, the position of each harmonic frequency is located in the center of each filter pass band.

By designing the basic filter bank as described above, spectral leakage between adjacent harmonics in harmonic decomposition can be greatly reduced.

At this time, since the use of the low pass filter (LPF) and the high pass filter (HPF) reduces the bandwidth of the signal by half, the number of samples of the signal can be reduced by half through the noise reduction process (↓ 2), which is effective in terms of calculation. Becomes These basic filter banks can be used repeatedly for higher order harmonic decomposition systems.

The Z-conversion expression for each output signal of the basic filter bank shown in FIG. 1 is as follows.

3 is a block diagram illustrating a filter bank system for detecting and tracking harmonics of a power signal using a basic filter bank (FB) of FIG. 1, and FIG. 4 is a frequency characteristic of the filter bank system of FIG. 3. It is explanatory drawing which shows.

First, referring to FIG. 3, it can be seen that it is a configuration of a three-stage harmonic decomposition filter bank designed to repeatedly detect a harmonic up to 15th order by decomposing a power signal by repeatedly applying a basic filter bank (FB). Can be.

Where FB is the basic filter bank shown in FIG. 1, h _i (i = 1 to 15, i-th harmonic) is harmonics decomposed by the filter bank, and f _i and a _i (i = 1 to 15) are respectively. It represents the estimated frequency and amplitude of harmonics h _i .

Possible harmonic filter bank system is in harmonic decomposition step (stage) number n decomposition as shown in FIG. 3 is a 2 ^{(n + 1)} becomes possible to -1, an even order harmonic decomposition of more than 15 by increasing the number of stages is possible to use the default filter bank can confirm.

The frequency characteristics of the filter bank system shown in FIG. 3 are approximately the same as those of FIG. 4. Referring to FIG. 4, h ₁ is a fundamental wave frequency of 60 Hz, and h ₁₅ is a fifteenth harmonic frequency of 900 Hz. Able to know.

5 is an explanatory view showing the structure of an adaptive predictor applied to a time-varying harmonic detection and tracking device of a power signal according to an embodiment of the present invention.

); 지연부(

)를 통해 지연된 지연신호로부터 고조파의 시간에 따라 변하는 특성에 대해 적응 예측을 수행하여 정수배의 고조파 신호를 출력하는 적응필터(W(Z)); 및 필터뱅크의 분해된 각 고조파 신호에서 정수배의 고조파 신호를 감산하여 오차신호로 비정수배의 고조파 신호를 출력하는 감산기를 포함한다.
이러한 적응예측기는 신호의 통계적 특성이 시변인 경우에도 최적의 해를 찾아가게 설계되므로, 시변 환경 고조파의 검출과 추적에 효과적인 시스템으로 사용될 수 있다. 5 shows the structure of the adaptive predictor for predicting the frequency and amplitude of the decomposed time varying harmonics in a time varying environment because the harmonics are also time varying when the frequency and amplitude of the power signal are time varying.
The adaptive predictor includes a delay unit for delaying each decomposed harmonic signal of the filter bank and outputting the delayed signal for a specific time.

); Delay section (

An adaptive filter (W (Z)) outputting an integer multiple of harmonic signals by performing adaptive prediction on characteristics varying with time of harmonics from a delayed signal delayed through; And a subtractor for subtracting an integer multiple harmonic signal from each of the decomposed harmonic signals of the filter bank and outputting a non-integer harmonic signal as an error signal.
Since the adaptive predictor is designed to find the optimal solution even when the statistical characteristics of the signal are time-varying, it can be used as an effective system for detecting and tracking time-varying environmental harmonics.

delete

By applying such an adaptive predictor to the processing of each harmonic decomposed by the filter bank, it is possible to more accurately detect and track the frequency and amplitude of time-varying harmonics.

는 지연을 의미하며, u(n)은 고조파 h_i가 지연된 신호이고, W(Z)는 적응필터, y(n)은 예측된 신호를 나타내고, e(n)=h_i(n)-y(n)의 오차신호로써 적응필터의 계수를 갱신하는데 사용된다.here

Denotes a delay, u (n) denotes a signal whose harmonic h _i is delayed, W (Z) denotes an adaptive filter, y (n) denotes a predicted signal, and e (n) = h _i (n) -y The error signal of (n) is used to update the coefficient of the adaptive filter.

를 적절히 조정함으로써 전력신호에 포함된 백색잡음(white noise)이나 임펄시브 잡음(impulsive noise) 등의 제거도 가능 하다.Delay through this adaptive predictor

By appropriately adjusting, it is possible to remove white noise, impulsive noise, and the like included in the power signal.

The signal y (n) processed by the adaptive predictor can be expressed as follows.

As the adaptive algorithm used in the adaptive predictor, various techniques based on the Least Mean Square (LMS) algorithm widely used for simplicity and stability may be applicable, but the present invention is not limited thereto.

At this time, it will be apparent to those skilled in the art that any conventional technique may be used as a method for calculating the magnitude of the frequency value and amplitude of each harmonic from the output signal of the adaptive predictor.

According to the apparatus and method for detecting and tracking time-varying harmonics of a power signal according to an embodiment of the present invention described above, a plurality of higher orders are provided by using a basic filter bank that can perform a function of reducing spectrum leakage between adjacent harmonics stepwise and continuously. Through the application of a filter bank system that decomposes harmonics and an adaptive predictor that detects and tracks the frequency and amplitude of time-varying harmonics with high accuracy, it eliminates transient noise and white noise, thereby improving the measurement accuracy of harmonics. In addition, it can be seen that robust measurement of harmonics is possible under noisy environment.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention belongs may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. You will understand that. Therefore, the embodiments described above are to be understood in all respects as illustrative and not restrictive.

1 is an explanatory diagram showing a structure of a basic filter bank applied to a time-varying harmonic detection and tracking device of a power signal according to an embodiment of the present invention.

2A is a graph illustrating frequency characteristics of a low pass filter (LPF) and a high pass filter (HPF) applied to the basic filter bank of FIG. 1.

FIG. 2B is a graph illustrating frequency characteristics of a band stop filter (BRF) and a band pass filter (BPF) applied to the basic filter bank of FIG. 1.

FIG. 3 is a block diagram illustrating an entire filter bank system for detecting and tracking harmonics of a power signal using a basic filter bank (FB) of FIG. 1.

4 is an explanatory diagram showing the frequency characteristics of the entire filter bank system of FIG.

5 is an explanatory view showing the structure of an adaptive predictor applied to a time-varying harmonic detection and tracking device of a power signal according to an embodiment of the present invention.

Claims (6)

In the time-varying harmonic detection and tracking device of the power signal, A filter bank for resolving harmonics of the power signal; And It includes an adaptive predictor for detecting and tracking the frequency and amplitude of time-varying harmonics by processing each harmonic decomposed by the filter bank, The filter bank may include: a band pass filter (BPF) for passing a specific band of an intermediate band of a high band and a low band of an input power signal; A band blocking filter (BRF) for blocking and passing a signal of a specific band passed through the band pass filter among the input power signals; A low pass filter (LPF) for passing only a low pass signal among the signals passed through the band stop filter; A high pass filter (HPF) for passing only a high pass signal among the signals passed through the band stop filter; And a basic filter bank (FB) including first and second signal attenuators which receive the output signals of the low pass filter and the high pass filter, respectively, and increase the bandwidth reduced in half to the bandwidth before reducing in half. It is possible to decompose high order harmonics by separating radix harmonics and even order harmonics by applying each harmonic decomposition stage (stage), The adaptive predictor may include: a delay unit configured to delay and output respective harmonic signals of the filter bank by a specific time delay; An adaptive filter outputting an integer multiple of harmonic signals by performing adaptive prediction on characteristics varying with time of harmonics from the delayed signal delayed through the delay unit; And a subtractor for subtracting the integer harmonic signal from each decomposed harmonic signal of the filter bank and outputting a non-integer harmonic signal as an error signal. delete delete delete In the time-varying harmonic detection and tracking method applied to the time-varying harmonic detection and tracking device of the power signal using the time-varying harmonic detection and tracking device of the power signal according to claim 1, A harmonic decomposition step of decomposing harmonics of the power signal using the filter bank; And It includes an adaptive prediction step for detecting and tracking the frequency and amplitude of the time-varying harmonics by processing each harmonic decomposed through the harmonic decomposition step, The harmonic decomposition step includes: (a) a band pass filter of a power signal to which a band pass filter (BPF) is input, and a specific band of a middle band of a high band and a low band to pass, and (b) a band pass filter of a power signal to which a band stop filter (BRF) is input. Passes the signal of a specific band passing through the block, and (c) the low pass filter (LPF) passes only the low pass signal of the signal passed through the band stop filter, (d) the high pass filter (HPF) is the band Passes only the high pass signal among the signals passed through the stop filter, and (e) the bandwidth before the first and second signal attenuators receive the output signals of the low pass filter and the high pass filter, respectively, and reduce the bandwidth reduced in half by half. To increase, In the adaptive prediction step, (f) the delay unit outputs each harmonic signal decomposed by the filter bank by a specific time delay, and (g) the adaptive filter changes the characteristics of the harmonics from the delayed signal delayed through the delay unit. Perform an adaptive prediction on the result and output an harmonic signal of an integer multiple, and (h) a subtractor subtracts the integer harmonic signal from each of the decomposed harmonic signals of the filter bank to output a non-integer harmonic signal as an error signal. Time-varying harmonic detection and tracking method of the power signal. delete

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