• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권11호
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• pp.563-571
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• 2003

In this paper, the control algorithm and control method for a combined system of shunt passive filter and series active filter in 3-phase 4-wire system are discussed. Moreover, the three-phase four-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and its 3th harmonics are termed as triple and zero sequence components that do not cancel each other in the system neutral. Consequently, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control algorithm for a series hybrid active system, whereas the control approach it adopts may directly influence its compensation characteristics. Hence, the advantage of this control algorithm is direct extraction of compensation voltage reference and the required rating of the series active filter is much smaller than that of a conventional shunt active filter. Some experiments were executed and experimental results from a prototype active power filter confirm the suitability of the proposed approach.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1072-1074
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• 2003

In this paper, a new control strategy of a series active power filter using direct compensating voltage extraction method is proposed. This control algorithm compensates harmonics, reactive power and neutral line currents which are generated by balanced or unbalanced nonlinear loads. The advantage of this method is that the compensating voltage of the series active power filter can be extracted without phase transformation. Therefore, calculation time is shorten and the control method is simple compared with conventional method as the p-q theory In addition, this control strategy was applied for the series active power filter in 3-phase 4-wire system which is widely employed in distributing electric energy to several office building and manufacturing plants. Some results obtained from the experimental model using the proposed method are presented to demonstrate and confirm its validity.

• 전기학회논문지P
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• 제54권2호
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• pp.88-93
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• 2005

Most of the LV customer have been applied the distribution system of 3-phase four wire system because of its advantage of supplying both of 1-phase & 3-phase loads simultaneously. Due to its structural simplicity, it is more convenient for use rather than the conventional separated scheme. But uneven load distribution or unclean voltage quality has occurred various problems such as de-rating, losses increase and vibration, etc. In this paper, voltage, current and power waveform in the actual fields have measured and analyzed in relation with internationally allowable voltage unbalance limits and compared the current unbalance factor with the load unbalance factor.

• Journal of Electrical Engineering and Technology
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• 제2권3호
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• pp.358-365
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• 2007

This paper deals with a novel solid state controller (NSSC) for parallel operated isolated asynchronous generators (IAG) feeding 3-phase 4-wire loads in constant power applications, such as uncontrolled pico hydro turbines. AC capacitor banks are used to meet the reactive power requirement of asynchronous generators. The proposed NSSC is realized using a set of IGBTs (Insulated gate bipolar junction transistors) based current controlled 4-leg voltage source converter (CC-VSC) and a DC chopper at its DC bus, which keeps the generated voltage and frequency constant in spite of changes in consumer loads. The complete system is modeled in MATLAB along with simulink and PSB (power system block set) toolboxes. The simulated results are presented to demonstrate the capability of isolated generating system consisting of NSSC and parallel operated asynchronous generators driven by uncontrolled pico hydro turbines and feeding 3-phase 4-wire loads.

• 조명전기설비학회논문지
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• 제20권8호
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• pp.54-62
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• 2006

3상 4선식 전원공급 시스템에서 단상 및 3상 부하의 운전하에서 전압 불평형은 부하의 불평형 운전에 의해 발생되고, 전류 불평형은 떨어진 전압 품질에 의해 더욱 심해진다. 에너지 변환장치로 사용되는 여러 형태의 컨버터는 3상 4선식 배전시스템에 직접적으로 고조파 전류를 주입함으로서 고조파 왜란을 증가시킨다. 고조파 전류는 전동기 출력 토크를 감소시키고, 전동기를 과열 또는 소음을 증가시키며 회전자에 토크 맥동을 증가하여 기계적인 공진과 진동을 발생하는 등 여러 가지 부작용을 낳고 있다. 따라서 본 논문은 3상 4선식 배전시스템에서 선형 및 비선형 부하의 혼합 운전시 불평형과 고조파 성분에 의해 유도전동기의 특성 변화에 대한 연구로서 선형 단독운전, 비선형 부하 결합에 따른 특성 변화를 해석한 것으로서 단상 비선형 부하의 추가 운전시 5 고조파 필터로도 저감이 어려운 고조파로 인해 토크 맥동 횟수는 줄고 리플값은 증가함을 확인할 수 있었다.

• 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.

• 조명전기설비학회논문지
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• 제18권6호
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• pp.91-99
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• 2004

대부분의 저압 수용가는 단상 및 3상 부하를 동시에 공급할 수 있는 장점을 지닌 3상 4선식 배전시스템을 적용하고 있다. 이 시스템은 구조적인 간단함 때문에 종래의 단상 및 3상 부하를 분리하는 방식보다 편리하다. 그러나 고르지 못한 부하 불평형이나 낮은 전기품질은 출력저하나 손실과 같은 문제를 발생하고 있다. 본 논문에서는 실제현장에서 전압 및 전류 파형을 측정하여 국제적으로 허용되고 있는 전압불평형 기준과 비교 분석을 실시하였다.

• 전기의세계
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• 제20권4호
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• pp.5-11
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• 1971

This is a study on the insulation methods of home appliances and wiring devices proper to the new electric distribution system, primary side is 22.9/13.2KV, 3 phase 4 wire multigrounding system and secondary side is 380/220V, 3 phase 4 wire common neutral system. 1800V is determined as the electrical insulation voltage of the functional insulation because the abnormal voltage rise of the neutral line is 1300V. In the case of the functional insulation faults, the following safety methods will be suggested to protect the accidental faults: (a) class I appliance (accessible metal part is earthed), (b) class II appliance (doublly insulated), (c) class III appliance (operates at low voltage source). The mechanisms of the wiring devices are not improved to guarantee for the harmful electric shock but also the electrical insulation voltage is rised to 2000V.

• 태양에너지
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• 제12권3호
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• pp.37-46
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• 1992

상변화 물질로 Paraffin wax를 사용한 잠열축열 시스템의 축열성능을 실험을 통하여 조사하였다. 가열유체로는 ethylene glycol을 사용하였고 왁스로의 전열을 위해 열싸이폰을 사용하였다. 왁스의 유효열전도율을 높이기 위해 여러장의 구리망을 왁스에 넣었고 실험은 체적비 2%, 3%, 4%에 대해 유량을 변화시키며 수행하였으며 몇가지 주요결과는 다음과 같다. (1) 구리망은 열전도를 촉진시켜 왁스의 온도를 균일화 하는 역할을 한다. (2) 구리망수의 증가는 열전도를 향상시키는 반면 응해된 왁스의 대류작용을 억제한다. (3) 축열시스템에 최적인 구리망의 수가 존재하며 이 연구에서는 체적비로 나타낼 때 $3{\sim}4%$인 것으로 나타났다.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.75-82
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• 2015

This paper presents a new technique for enhancing power quality by reducing harmonics in the neutral conductor. Three-Phase Four-Wire (3P4W) system is commonly used where single and three phase loads are connected to Point of Common Coupling (PCC). Due to unbalance loads, the 3P4W distribution system becomes unbalance and current flows in the neutral conductor. If loads are non-linear, then the harmonic content of current will flow in neutral conductor. The neutral current that may flow towards transformer neutral point is compensated by using a series active filter. In order to reduce the harmonic content, the series active filter is connected in series with the neutral conductor by which neutral and phase current harmonics are reduced significantly. In this paper, solar PV based inverter circuit is proposed for compensating neutral current harmonics. The simulation is carried out in MATLAB/SIMULINK and also an experimental setup is developed to verify the effectiveness of the proposed method.