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Linear filter-based harmonic current detection method in three-phase four-wire system

A technology of three-phase four-wire system and detection method, which is applied in the field of electric power system, can solve problems such as poor real-time performance, large amount of calculation, and difficult selection of wavelet base

Inactive Publication Date: 2011-11-23
XIHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In addition, although wavelet analysis is used for harmonic detection, although it has achieved good results, it has a large amount of calculation and poor real-time performance. At the same time, the choice of wavelet base is also a difficult problem.

Method used

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  • Linear filter-based harmonic current detection method in three-phase four-wire system
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  • Linear filter-based harmonic current detection method in three-phase four-wire system

Examples

Experimental program
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Effect test

Embodiment 1

[0152] Ideally balanced mains voltage situation: figure 2 with image 3 The simulation results of the system in the case of ideal symmetrical three-phase sinusoidal mains voltage are shown. figure 2 The main voltage waveform V is given in abc (a), load current waveform i labc (b), power supply current waveform i sabc (c), the fundamental waveform i of the power supply current of each phase output by the two-dimensional linear filter fabc (d) and the waveform i of the positive sequence component of the current fundamental wave after the calculation of the symmetrical component fpabc (e). image 3 The compensation situation of neutral current and reactive current is given. Neutral current iln(a) before compensation, neutral current isn(b) after compensation, waveform Vsa, ila(c) of phase A voltage and current before compensation, voltage and current waveform Vsa, isa(d) after compensation. Table 2 shows the load current, power supply current, neutral current and their h...

Embodiment 2

[0157] Unbalanced sinusoidal mains voltage case: The unbalanced sinusoidal mains voltage is given by:

[0158] v a =380sinωt+38sinωt

[0159] v b =380sin(ωt-120°)+38sin(ωt+120°)

[0160] v c =380sin(ωt+120°)+38sin(ωt-120°)

[0161] The simulation results of the system in the case of unbalanced three-phase sinusoidal main voltage are as follows: Figure 4 with Figure 5 As shown, the meaning of each waveform in the figure is the same as figure 2 with image 3 same.

[0162] The simulation results show that under the action of unbalanced sinusoidal voltage, the load currents of A, B, and C phases are seriously unbalanced, and large harmonic currents appear on the neutral line. When the AFP is connected at 0.15s, the three-phase power supply current reaches balance, and the THD of the B-phase current drops from 39.34% to 1.14% between 0.15s and 0.3s. After the time is greater than 0.3s, the THD changes from the original 51.55% dropped to 1.27%, at the same time, the ne...

Embodiment 3

[0167] Balanced distorted main voltage situation: In order to study the system performance under balanced distorted main voltage, the following three-phase power supply is constructed:

[0168] v a =380sinωt+4.56sin3ωt+22.8sin(5ωt-120°)+5.7sin7ωt+3.8sin(11ωt-120°)

[0169] v b =380sin(ωt-120°)+4.56sin3ωt+22.8sin5ωt+5.7sin(7ωt-120°)+3.8sin11ωt

[0170] v c =380sin(ωt+120°)+4.56sin3ωt+22.8sin(5ωt+120°)+5.7sin(7ωt+120°)+3.8sin(11ωt+120°)

[0171] The simulation results of the system in the case of unbalanced three-phase sinusoidal main voltage are as follows: Image 6 with Figure 7 As shown, the meaning of each waveform in the figure is the same as figure 2 with image 3 same.

[0172] The simulation results show that under the action of the balanced and distorted main voltage, the load current and the power supply current are severely distorted and unbalanced, and the THD of the neutral current is 70.81%. It is well suppressed, the imbalance is compensated, and the ne...

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Abstract

The invention discloses a linear filter-based harmonic current detection method in a three-phase four-wire system. According to the method, a structural characteristic of the three-phase four-wire system is considered; according to the idea of an adaptive notch filter (ANF), a two-dimensional linear sine filter is obtained after rotation transformation on the basis of a minimum variance principleand a gradient decent method; fundamental currents of all phases are respectively separated from an actual measured current by the two-dimensional linear sine filter; and then a symmetrical fundamental wave positive sequence component is obtained by utilizing a modified instantaneous symmetric component calculation method; after calculation of the fundamental wave positive sequence component withthe original actual measured current, a harmonic component of a load current, a fundamental negative sequence component and a zero sequence component are drawn off. Compared with the prior art, a technique employed in the linear filter-based harmonic current detection method in the three-phase four-wire system provided of the invention enables the method to have the following advantages that: themethod is simple with a small amount of computation and it is not needed to carry out complicated rotation transformation and trigonometric function calculation; the method has a good real-time performance and high detection precision; and a harmonic current and a reactive current and a neutral current in the three-phase four-wire system can be detected on the condition of unsymmetrical nonlinearload and nonideal voltage.

Description

technical field [0001] The invention relates to the field of electric power system, specifically a three-phase four-wire system harmonic current detection method based on a linear filter. Background technique [0002] At present, with the development and application of modern power electronic technology, power electronic devices have become the most important source of harmonic pollution in the power grid, seriously threatening the safety of the power grid and electrical equipment. Harmonic control of power system has attracted the attention of many scholars at home and abroad. At present, the research on harmonic control of power system in our country is mainly concentrated in the three-phase three-wire system. Although there are some studies in the three-phase four-wire system, there are still many problems to be further studied. [0003] In the low-voltage power distribution system, the three-phase four-wire power supply mode is the most important power supply mode, whic...

Claims

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Application Information

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IPC IPC(8): G01R19/00
Inventor 邱晓初
Owner XIHUA UNIV
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