• 조명전기설비학회논문지
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• 제18권4호
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• pp.60-67
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• 2004

비선형 부하의 증가로 3상 4선식 배전계통을 채용하는 중성선에는 많은 중성선 고조파 전류가 관측되고 있다. 또한 접지 임피던스는 고주파가 있는 중성선 전류에 영향 끼친다고 알려져 있다. 현장에서 실측한 고조파 전압과 전류, 그리고 대지 고유 저항률과 접지 저항을 토대로 고조파 해석용 등가 회로를 구성하였다. MATLAB과 CDEGS 프로그램으로 시뮬레이션 하여 수치와 파형으로 적절한 결과를 도출하였다.

• 조명전기설비학회논문지
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• 제17권3호
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• pp.40-48
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• 2003

컴퓨터 부하는 현대사회 전반에 걸쳐 널리 사용되고 있다. 개인용 컴퓨터의 스위칭 모드 전원공급 장치는 고조파 전류를 발생시키는 주된 발생원이다. 고조파 전류는 전압파형 왜곡, 과다한 중성선 전류, 측정오차, 컴퓨터 일시 정지등 많은 고조파 장해를 일으킬 수 있다. 본 논문의 목적은 단상 개인용 컴퓨터 부하의 고조파 해석용 등가회로 모델링과 고조파 전류를 저감하기 위한 상품화된 직렬 동조 필터를 국제 고조파 관리 기준인 IEEE 519-1992와 IEC 1000-3-2를 근거로 평가하는데 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1033-1036
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• 2002

This paper introduces a control method of series active power filter that compensate harmonic currents and eliminate a neutral line current in 3 phase 3 wire and 3 phase 4 wire power system with harmonic voltage source. These harmonic currents and neutral line current are caused by a nonlinear loads such as diode rectifiers and thyristor converters. Proposed methode extracts a voltage reference directly from performance function without phase transformation. Therefore, the control method is simpler than any other conventional methods. Experimental results for 3-phase 3-wire and 3-phase 4-wire series active power filter system were shown to verify the effectiveness of this control method.

• 전력전자학회논문지
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• 제3권3호
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• pp.184-190
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• 1998

대부분의 빌딩과 공장에서는 3상 4선식 저압 배전 시스템으로 전력을 공급받고 있다. 이 방식은 중성선에 전류가 흐르게 하는데 오늘날 전력 변환 기술의 개발과 컴퓨터의 보급으로 심각한 중성 전류가 발생하고 있다. 본 논문은 병렬형 3상 4선 능동 필터를 사용하여 계통의 전원 전압이 불평형이고 불평형 부하 및 비선형 부하가 접속된 상태에서 전원쪽으로 흐르는 중성 전류를 제거시키고, 전원전류의 파형을 정현파로 개선하는데 목적이 있으며, 부하 조건을 변화시키면서 시뮬레이션을 실행하여 능동 필터의 우수한 성능을 입증하였다.

• Journal of Power Electronics
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• 제12권2호
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• pp.344-356
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• 2012

In recent years, multilevel technology has become an effective and practical solution in the field of moderate and high voltage applications. This paper discusses an APF with a three-level NPC inverter. Obviously, the application of such converter to APFs is hindered by the problem of the voltage unbalance of DC capacitors, which leads to system instability. This paper comprehensively analyzes the theoretical limitations of the neutral-point voltage balancing problem for tracking different harmonic currents utilizing current switching functions from the space vector PWM (SVPWM) point of view. The fluctuation of the neutral point caused by the load currents of certain order harmonic frequency is reported and quantified. Furthermore, this paper presents a close-loop digital control algorithm of the DC voltage for this APF. A PI controller regulates the DC voltage in the outer-loop controller. In the current-loop controller, this paper proposes a simple neutral-point voltage control method. The neutral-point voltage imbalance is restrained by selecting small vectors that will move the neutral-point voltage in the direction opposite the direction of the unbalance. The experiment results illustrate that the performance of the proposed approach is satisfactory.

• 조명전기설비학회논문지
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• 제22권10호
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• pp.76-83
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• 2008

중성선 전류는 부하 불평형 전류와 3배수 고조파 전류로 이루어져 있다. 중성선 전류의 주요한 원인이 되는 3배수 고조파 전류는 단상 비선형 부하가 사용하는 단상 정류회로에 기인하며, IEC 61000-3-2의 클래스 D에 속하는 TV, 컴퓨터, 모니터가 부하전류 대 3배수 고조파 전류를 가장 많이 발생시킨다. 배전계통에 미치는 고조파 영향의 예를 보이기 위해 고조파를 고려하지 않은 중성선 공용 문제에 대해 현행 배전설비 설계기준을 살펴보고 대책을 살펴본다.

• 전기학회논문지P
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• 제66권3호
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• pp.99-104
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• 2017

The three-phase four-wire power distribution system can be used to supply power to single-phase and three-phase loads at the same time. There are linear loads and nonlinear loads as single-phase loads connected to each phase. The nonlinear load generates a harmonic current during the power energy conversion process. In particular, the single-phase nonlinear load has a higher proportion of generation of the third harmonic current than the harmonics of the other orders. In a three-phase four-wire system, the third harmonic current flows through the neutral wire to the power supply side, affecting the power supply side and the line. Furthermore, the magnitude of the current flowing in the neutral line can be higher than the current flowing in the individual phase. If the neutral current is higher than the phase current, the breaker may be blocked. Therefore, it is necessary to reduce the amount of current flowing in the neutral line by harmonics. There is a method of zigzag connecting a single phase transformer by a method of reducing 3 harmonic current. In this study, the method of reducing the magnitude of the three harmonic currents flowing through the zigzag wire by comparing the polarity and the negative polarity characteristics of the single phase transformer was compared through measurement and simulation.

• Journal of Power Electronics
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• 제14권2호
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• pp.315-323
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• 2014

An optimized space vector pulse width modulation (SVPWM) method with common mode voltage elimination and neutral point potential balancing is proposed for an open-end winding induction motor. The motor is fed from both of the ends with two neutral point clamped (NPC) three-level inverters. In order to eliminate the common mode voltage of the motor ends and balance the neutral point potential of the DC link, only zero common mode voltage vectors are used and a balancing control factor is gained from calculation in the strategy. In order to improve the harmonic characteristics of the output voltages and currents, the balancing control factor is regulated properly and the theoretical analysis is provided. Simulation and experimental results show that by adopting the proposed method, the common mode voltage can be completely eliminated, the neutral point potential can be accurately balanced and the harmonic performance for the output voltages and currents can be effectively improved.

• Journal of Power Electronics
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• 제18권6호
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• pp.1866-1878
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• 2018

This paper presents a neutral point deviation and ripple compensation control method for application to 3-level NPC converters. The neutral point deviation and its harmonic components are analyzed with a focus on the average current flowing through the neutral point of the dc-link. This paper also proposes a control scheme to compensate for the neutral point deviation and dominant harmonic components under generalized unbalanced grid operating conditions. The positive and negative sequence components of the pole voltages and ac input currents are employed to accurately explain the behavior of 3-level NPC converters. Simulation and experimental results are presented to verify the validity of the proposed method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.183-184
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• 2008

In this paper, the THD(Total Harmonic Distortion) in distribution systems according to the ratio of non-linear loads was calculated and analyzed. The PCC(Point of Common Coupling) is selected to analyze THD of a 3-phase current and a neutral current.