KR101822004B1 - Apparatus for detecting resonance frequency of grid-connected inverter and method thereof - Google Patents

Apparatus for detecting resonance frequency of grid-connected inverter and method thereof Download PDF

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KR101822004B1
KR101822004B1 KR1020150136724A KR20150136724A KR101822004B1 KR 101822004 B1 KR101822004 B1 KR 101822004B1 KR 1020150136724 A KR1020150136724 A KR 1020150136724A KR 20150136724 A KR20150136724 A KR 20150136724A KR 101822004 B1 KR101822004 B1 KR 101822004B1
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South Korea
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harmonic
frequency
component
current
grid
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KR1020150136724A
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Korean (ko)
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KR20170037771A (en
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임지훈
윤용범
전웅재
김수열
조성민
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한국전력공사
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/16—Spectrum analysis; Fourier analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/145—Indicating the presence of current or voltage
    • G01R19/15—Indicating the presence of current
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/16—Spectrum analysis; Fourier analysis
    • G01R23/165—Spectrum analysis; Fourier analysis using filters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

A method of detecting a resonant frequency of a grid interconnected inverter according to an embodiment of the present invention includes a harmonic current extraction step of extracting a harmonic current by filtering a grid current of a grid interconnected inverter, A first coordinate conversion step of converting a coordinate of a component to extract a direct current component; a maximum harmonic component extraction step of extracting a harmonic component having a maximum value by comparing magnitudes of the direct current components of the harmonic component; A second coordinate transformation step of transforming coordinates of a harmonic component having a non-integer frequency within a predetermined frequency range around a frequency of a harmonic component having a non-integer frequency, And the magnitude of the DC component of the harmonic component having the maximum value W and a further resonance frequency detection stage for detecting the frequency of the harmonic components with a value of the resonance frequency.

Description

[0001] APPARATUS FOR DETECTING RESONANCE FREQUENCY OF GRID-CONNECTED INVERTER AND METHOD THEREOF [0002]

The present invention relates to an apparatus and method for detecting resonance frequency of a grid interconnected inverter.

Generally, when linking solar energy, wind energy and energy storage system (ESS) to a system, it connects with the system through a power conditioning system that converts DC power to AC power.

Generally, systems connected to a system have a very large impedance compared to a system. Recently, a large-capacity new renewable complex or a large-scale ESS has a low impedance due to a parallel configuration of the system, and an accident may occur due to resonance with the system.

In general, a power conversion device (PCS) performs power conversion of DC and AC through switching of power electronic devices. It can not implement a perfect sine wave type as a digital device, not an analog device, and thus includes harmonics of a certain component. Harmonics of certain components of the harmonics contained may not attenuate or increase in size due to resonance with the system, leading to equipment accidents.

In order to block the resonance between the harmonics and the system, the resonance frequency must be accurately detected.

However, the conventional resonance frequency detecting apparatus only detects the resonance frequency with respect to harmonics having an integer multiple of harmonics, and can not detect the resonance frequency with respect to harmonics having a frequency of a non-integer multiple, The accurate resonance frequency can not be detected.

The following Patent Document 1 relates to a harmonic suppression apparatus, but fails to provide a solution to the above-mentioned problem.

Japanese Patent Publication No. 2788473

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the problems of the prior art described above, and it is an object of the present invention to provide a method and apparatus for searching a resonance frequency for a harmonic component having an integer multiple frequency and searching a resonance frequency for harmonic components having an undetermined frequency, The present invention also provides an apparatus and method for detecting a resonant frequency of a grid interconnected inverter capable of detecting a resonant frequency of a grid interconnected inverter.

A method of detecting a resonant frequency of a grid interconnected inverter according to an embodiment of the present invention includes a harmonic current extraction step of extracting a harmonic current by filtering a grid current of a grid interconnected inverter, A first coordinate conversion step of converting a coordinate of a component to extract a DC component; a maximum harmonic component extraction step of extracting a harmonic component having a maximum value by comparing magnitudes of the DC components of the harmonic component; A second coordinate transformation step of transforming coordinates of a harmonic component having a non-integer frequency within a predetermined frequency range around a frequency of a harmonic component having a non-integer frequency, And the magnitude of the DC component of the harmonic component having the maximum value W and a further resonance frequency detection stage for detecting the frequency of the harmonic components with a value of the resonance frequency.

In one embodiment, the resonant frequency detecting method of the grid interconnected inverter may further include an AC component filtering step of filtering an AC component of the harmonic current between a first coordinate transformation step and a maximum harmonic component extraction step.

In one embodiment, the harmonic current extraction step may extract the harmonic current using a high-pass filter that filters fundamental waves and harmonics of a predetermined order or less.

In one embodiment, the first coordinate transformation step may extract the DC component from harmonic components having the integer frequency by using a DQ coordinate transformation method.

In one embodiment, the second coordinate transformation step may extract the DC component from harmonic components having the non-integer frequency using a DQ coordinate transformation method.

A resonance frequency detecting apparatus for a grid-connected inverter according to an embodiment of the present invention includes a harmonic current extracting unit for filtering a grid current of a grid-connected inverter to extract a harmonic current, a harmonic current extractor for extracting a harmonic current, And a frequency detector for detecting a frequency of a harmonic component having a maximum value by comparing magnitudes of the DC components extracted by the coordinate converter, wherein the coordinate converter converts the coordinates A harmonic component having a maximum value among the harmonic components having the integer multiple of frequency is detected by the frequency detector, a harmonic component having an undetermined frequency within a predetermined frequency range centered on the frequency, The DC component is extracted, and the frequency The detection unit compares the DC component of the harmonic component having the maximum value detected between the harmonic components having the integer frequency and the DC component of the harmonic component having the non-integer multiple frequency (Inter-Harmonic) As a resonance frequency.

In one embodiment, the resonance frequency detecting device of the grid interconnected inverter may further include a low-pass filter for filtering the AC component of the harmonic current between the coordinate converter and the frequency detector.

In one embodiment, the harmonic current extractor may extract the harmonic current by filtering harmonics of a fundamental wave and a predetermined order or less.

In one embodiment, the coordinate transforming unit may extract the DC component from harmonic components having the integer frequency by using a DQ coordinate transformation method.

According to an embodiment of the present invention, a resonance frequency is searched for a harmonic component having an integer frequency, and also a harmonic component having a non-integer frequency is searched for a resonance frequency to detect a frequency close to an actual resonance frequency. .

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a block diagram for explaining a resonance frequency detecting apparatus of a grid-connected inverter according to an embodiment of the present invention; FIG.
2 is a block diagram illustrating a resonance frequency detecting apparatus of a grid interconnect type inverter according to another embodiment of the present invention.
3 is a flowchart illustrating a method of detecting a resonant frequency of a grid interconnected inverter according to an embodiment of the present invention.
4 is a flowchart illustrating a method of detecting a resonant frequency of a grid interconnected inverter according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

In the drawings referred to in the present invention, elements having substantially the same configuration and function will be denoted by the same reference numerals, and the shapes and sizes of the elements and the like in the drawings may be exaggerated for clarity.

FIG. 1 is a block diagram for explaining a resonance frequency detecting apparatus of a grid-connected inverter according to an embodiment of the present invention. FIG. 2 is a circuit diagram of a resonance frequency detecting apparatus of a grid-connected inverter according to another embodiment of the present invention. Fig.

1, an apparatus 100 for detecting a resonance frequency of a grid-connected inverter according to an embodiment of the present invention includes a harmonic current extracting unit 110, a coordinate transforming unit 120, and a frequency detecting unit 130 .

In one embodiment, the resonant frequency detection device 100 of the grid interconnected inverter may further include a low-pass filter 140, as in Fig.

The harmonic current extraction unit 110 may extract the harmonic current i h by filtering the grid current of the grid interconnected inverter. In one embodiment, the harmonic current extraction unit 110 may be a high-pass filter 112 that extracts harmonics current i h by filtering fundamental waves and harmonics below a predetermined order, as in Fig. 2 .

For example, when the fundamental frequency is 60 Hz and the resonance frequency is detected with respect to the fifth harmonic component or more, the high-pass filter 112 can be designed to block the signal of 300 Hz or less. Here, the high-pass filter 112 can use a digital signal processing method and can use the transfer function by discretizing it.

The coordinate transforming unit 120 may extract the direct current component by converting the coordinates of the harmonic components having an integer multiple of the fundamental frequency (3n + 1) from the harmonic current i h .

In one embodiment, the coordinate transforming unit 120 may extract a DC component from a harmonic component using a DQ coordinate transformation method. Specifically, the coordinate transforming unit 120 can extract the DC component of each harmonic component by rotating the coordinates according to the frequency of each harmonic component.

For example, in the case of a third harmonic component having a fundamental frequency of 60 Hz, it may be an AC signal of 180 Hz. If the coordinate is rotated at 180 Hz, the DC component of the third harmonic component can be extracted.

When a frequency of a harmonic component having a maximum value among the harmonic components having the frequency is detected by the frequency detector, the coordinate converter 120 converts the non-integer multiple frequency in a predetermined frequency range (± Δf) The DC component can be extracted by transforming the coordinate of the harmonic component (Inter-Harmonic).

In searching for a resonance frequency, a resonance frequency is searched for a harmonic component having an integer frequency, and a harmonic component having a non-integer frequency can be detected to detect a frequency close to an actual resonance frequency. It is possible to perform more accurate harmonic compensation by controlling the current of the grid-connected inverter.

The frequency detector 130 may extract a harmonic component having a maximum value by comparing magnitudes of DC components of the harmonic components extracted from the coordinate converter, and may detect the frequency of the extracted harmonic component as a resonant frequency.

Specifically, the frequency detector 130 may first extract harmonic components having the largest value by comparing DC components of harmonic components having an integer frequency.

Next, when the coordinate transforming unit 120 transforms the coordinates of the harmonic components having the non-integer frequency extracted in the predetermined frequency range around the frequency of the harmonic component having the largest value to extract the DC component, 130 compares the magnitude of the DC component of the harmonic component having the extracted non-integer frequency with the magnitude of the DC component of the harmonic component having the largest value among the harmonic components having the integer frequency, The frequency can be detected as the resonance frequency.

The low-pass filter 140 can filter the AC component of the harmonic current between the coordinate converter 120 and the frequency detector 130. In this manner, after the coordinate conversion unit 120 performs the coordinate conversion to extract the DC component from the harmonic component, the low-pass filter 140 removes the AC component other than the DC component to accurately analyze the harmonic component do.

In one embodiment, the resonant frequency detecting device 100 of the grid interconnected inverter of Figs. 1 and 2 can be implemented by hardware such as a processor.

The method of detecting the resonant frequency of the grid interconnected inverter shown in Figs. 3 and 4 is performed in the resonant frequency detecting apparatus 100 of the grid interconnected inverter described above with reference to Figs. 1 and 2, and therefore, Or the corresponding contents shall not be described redundantly.

3 is a flowchart illustrating a method of detecting a resonant frequency of a grid interconnected inverter according to an embodiment of the present invention.

Referring to FIG. 3, in the resonant frequency detecting method of the grid-connected inverter according to the embodiment of the present invention, the harmonic current extracting unit 110 may extract the harmonic current by filtering the grid current (S200) .

Next, the coordinate transforming unit 120 transforms the coordinates of the harmonic component having the integer frequency of the fundamental frequency from the harmonic current extracted by the harmonic current extracting unit 110 to extract the DC component (S210).

Next, the frequency detector 130 may compare the magnitudes of the DC components of the harmonic components having the integer frequency to extract harmonic components having the maximum value (S220).

Next, the coordinate transforming unit 120 transforms the coordinates of the harmonic component having the non-integer frequency within a predetermined frequency range around the frequency of the harmonic component having the maximum value to extract the DC component (S230) .

Next, the frequency detector 130 compares the magnitude of the DC component of the harmonic component having the largest value among the harmonic components having the integer frequency and the magnitude of the DC component of the harmonic component having the non-integer frequency, The frequency of the component can be detected as the resonance frequency (S240).

4 is a flowchart illustrating a method of detecting a resonant frequency of a grid interconnected inverter according to another embodiment of the present invention.

The basic steps of the embodiment of FIG. 4 are the same as the embodiment of FIG. 3 except that a low-pass filter 140 is used between the first coordinate transformation steps S210 and S310 and the maximum harmonic component extraction step S220 and S330 And an AC component filtering step (S320) of filtering the AC component of the harmonic current.

Since the other steps are the same as those of the above-described basic embodiment, the remaining description will be omitted.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the particular forms disclosed. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100: Resonant frequency detection device of grid-connected inverter
110: Harmonic current extraction unit
120: Coordinate transformation unit
130:
140: low-pass filter

Claims (9)

A harmonic current extraction step of extracting a harmonic current by filtering the grid current of the grid-connected inverter;
A first coordinate transformation step of transforming coordinates of a harmonic component having an integer multiple of a fundamental frequency in the harmonic current to extract a direct current component;
A maximum harmonic component extraction step of extracting a harmonic component having a maximum value by comparing magnitudes of the DC components of the harmonic components;
A second coordinate transformation step of transforming coordinates of a harmonic component (Inter-Harmonic) having a non-integer frequency within a predetermined frequency range around the frequency of the harmonic component having the maximum value to extract a direct current component; And
And a resonance frequency detecting step of comparing the magnitude of the DC component of the harmonic component having the non-integer frequency and the magnitude of the DC component of the harmonic component having the maximum value to detect the frequency of the harmonic component having a larger value as the resonance frequency A method of detecting resonance frequency of a grid - connected inverter.
The method according to claim 1,
Between the first coordinate transformation step and the maximum harmonic component extraction step,
An AC component filtering step of filtering an AC component of the harmonic current; Further comprising the steps of: detecting a resonant frequency of the grid-connected inverter;
The method of claim 1, wherein the harmonic current extraction step comprises:
And extracting the harmonic current using a high-pass filter for filtering harmonics of a fundamental wave and a predetermined order or less.
2. The method according to claim 1,
And extracting the DC component from the harmonic components having the integer frequency by using the DQ coordinate conversion method.
2. The method according to claim 1,
And extracting the DC component from the harmonic components having the non-integer multiple frequency using a DQ coordinate transformation method.
A harmonic current extractor for extracting a harmonic current by filtering the grid current of the grid interconnected inverter;
A coordinate transforming unit for transforming coordinates of harmonic components having an integer frequency of the fundamental frequency in the harmonic current to extract a direct current component; And
And a frequency detector for detecting a frequency of a harmonic component having a maximum value by comparing magnitudes of the DC components extracted by the coordinate converter,
Wherein when the frequency of the harmonic component having the maximum value among the harmonic components having the integer frequency is detected in the frequency detector, the coordinate converter converts the harmonic component having the non-integer frequency within a predetermined frequency range around the frequency Inter-Harmonic) is transformed to extract DC components,
Wherein the frequency detector compares the DC component of the harmonic component having the maximum value detected between the harmonic components having the integer frequency and the DC component of the harmonic component having the non-integer multiple frequency (Inter-Harmonic) A resonant frequency detecting apparatus for a grid interconnection inverter for detecting a frequency of a harmonic component at a resonant frequency.
The method according to claim 6,
Between the coordinate converter and the frequency detector,
And a low-pass filter for filtering the AC component of the harmonic current.
[7] The apparatus of claim 6, wherein the harmonic current extractor comprises:
Wherein the harmonic current is extracted by filtering a fundamental wave and harmonics of a predetermined order or less.
The apparatus as claimed in claim 6,
And extracting the direct current component from harmonic components having the integer frequency by using a DQ coordinate conversion method.

KR1020150136724A 2015-09-25 2015-09-25 Apparatus for detecting resonance frequency of grid-connected inverter and method thereof KR101822004B1 (en)

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CN108196121B (en) * 2018-01-16 2020-05-19 天津瑞能电气有限公司 Intelligent micro-grid dynamic frequency detection method
CN108490257B (en) * 2018-03-26 2020-08-21 华北电力大学 Short-time window inter-harmonic measurement method based on spectral curve fitting
KR102276105B1 (en) * 2019-12-13 2021-07-12 아주대학교산학협력단 Apparatus and method for selective harmonic compensation method for grid-connected inverter

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JP2788473B2 (en) 1989-04-01 1998-08-20 ニチコン株式会社 Harmonic suppression device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110231514A (en) * 2019-06-26 2019-09-13 北京四方继保自动化股份有限公司 A kind of synchronous phasor measuring method suitable for wideband measurement
CN110231514B (en) * 2019-06-26 2021-06-08 北京四方继保自动化股份有限公司 Synchronous phasor measurement method suitable for broadband measurement

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