• 조명전기설비학회논문지
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• 제24권9호
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• pp.36-43
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• 2010

This paper proposes a new type of voltage sag-swell compensator based on a Z-source AC-AC converter. The proposed topology employs a pulse width modulation (PWM) Z-source AC-AC converter along with a injection transformer. A safe commutation strategy is used to eliminate voltage spikes on switches without snubber circuit. During a voltage sag or swell, the proposed system controls the adding or missing voltage and maintains the rated voltage of sinusoidal waveform at the terminals of the critical loads. The proposed system is able to compensate 20[%] voltage swell and is also able to compensate 60[%] voltage sag. In order to control and detect the voltage sag and swell, the peak voltage detection method is applied. Also, the operating principles of the proposed system are described, and a circuit analysis is provided. Finally, PSIM simulation and experimental results are presented to verify the proposed concept and theoretical analysis.

• 전자공학회논문지
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• 제51권5호
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• pp.219-225
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• 2014

본 논문에서는 가정용 교류 전원을 DC 전원으로 변환하여 가전기기에 사용할 수 있는 역률 개선 회로를 설계하였다. 역률은 공급되는 교류 전원의 전압과 전압의 위상차 뿐만 아니라 특정구간에서 발생되는 급격한 전류 파형의 불균형 등과도 관련이 있다. 설계된 본 회로는 부하에 공급되는 교류전력의 전류 파형은 전압파형과 위상차가 적으면서 정현파에 가깝게 공급하는 기능을 제공한다. 자체 발진하는 10[kHz]~100[kHz] 내외의 주파수로 AC 전원에 연결된 코일을 스위칭 한 후 코일전류를 부하에 공급하는 기능을 위한 회로, AC 파형의 zero crossing 지점을 찾는 기능을 함께 수행하는 multiplier 회로, UVLO, OVP, BGR 등의 회로를 한 개의 IC에 집적할 수 있도록 설계하였다. 제작공정은 최소선폭 $0.5[{\mu}m]$, 내압 20[V], 2P_2M CMOS 공정을 사용하여 설계하였고 시뮬레이션을 통하여 전체 기능을 검증하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.155-160
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• 2002

Metal matrix composites had generated a lot of interest in recent times because of significant in specific properties. It was also highlighted as the materials of frontier industry because strength, heat-resistant, corrosion-resistant, wear-resistant were superiored. In this study the strength properties of $Al_{18}B_4O_{33}/AC4CH$ were represented mixing the binder of $Al_2O_3$ and $TiO_2$. It was also fabricated by squeeze casting. $Al_{18}B_4O_{33}/AC4CH$ was fabricated at the melt temperature of $760^{\circ}C$ the perform temperature of $700^{\circ}C$ and mold temperature of $200^{\circ}C$ under the pressure of 83.4MPa and observed SEM. Fatigue crack growth rate tests on compact tension specimen(half-size) of thickness 12.5mm were conducted by using sinusoidal waveform. Compact tension specimens(half-size) were used and fatigue crack growth rate da/dN and stress intensity factor range ${\Delta}K$ were analyzed concerning to the R value of 0.1 and 0.05. In order to find out the value of ${\Delta}K$, load amplitude constant method was applied by the standard fatigue testing method describes in ASTM E647-95a. As the results of this study, Fatigue crack growth rate increased with in creasing the load ratio, Consequently, At equivalent stress intensity factors, the fatigue crack growth rates in MMC were faster than those of AC4CH alloy. then the fatigue life and the fatigue crack growth rate was investigated using scanning election microscopy(SEM)

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.437-439
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• 1996

In this paper, an UPS system using high-frequency link AC to DC converter is Proposed. The AC to DC converter has sinusoidal input current and high power factor. In this UPS system, the waveform of the output voltage has smaller harmonic contents than those of a conventional UPS system. In this paper, an operating principle of the system is presented. This new control technique of the UPS system is capable of providing a wide range regulated output DC voltage compared with the conventional UPS system. Performance of the system carried out through theoretical and experimental means.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권10호
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• pp.501-507
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• 2001

In this paper, new high-efficiency zero voltage switching (ZVS) AC-DC boost converter is proposed to achieve power factor correction by simplifing energy recovery circuit. A lot of high power factor correction circuits have been proposed and applied to increase input power factor and efficiency. Most of these circuits may obtain unity power factor and achieve sinusoidal current waveform with zero voltage or/and zero current switching. However, it is difficult for them to obtain low cost, small size, low weight, and low noise. The topology proposed to improve these problems can compact the devices in circuit and can achieve high efficiency ZVS AC-DC boost converter. Simulation and experimental results show that this topology is capable of obtaining high power factor and increasing the efficiency of the system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.431-432
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• 2014

Recently, the demand of LED(light-emitting diode) lighting is gradually enlarged by governmental saveenergy policy, which the LED lighting has been established compulsorily in new buildings, public institutions, and residential installations etc.. The LED lighting is driven by SMPS (switching mode power supply). The SMPS requires high efficiency because the SMPS changes a commercial ac power source to low voltage dc power source. Harmonic components that occur in the conversion process of SMPS decrease system power factor and deal great damage in electric power system. To improve such problems, this paper proposes a SMPS of high efficiency. The switching devices in the proposed SMPS are operated by soft switching technique using a new quasi-resonant circuit. The input ac current waveform in the proposed SMPS becomes a quasi-sinusoidal waveform proportional to the magnitude of input ac voltage under constant switching frequency. As a result, the proposed SMPS obtains low switching power loss and high efficiency, and its input power factor is nearly in unity.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.309-312
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• 2000

Single-phase multi-level AC-DC converter is proposed that is composed of diode bridge and switch. The number of the supply current level is depending on the individual current level of the converter. A converter circuit the number of the level is equal to $\textrm{2}^{M+1}$-1 The proposed circuit has converter with 31 current levels. When the number of current level is increased smoother sinusoidal waveform can be obtained directly and it is possible to control the supply current almost continuously from zero to maximum without step changes of generating high voltage as pulse width modulation switching loss is decreased it has an advantage in large capacity. it is illustrated technique are confirmed the validity and effectiveness through the simulation & experiments

• 전기전자학회논문지
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• 제16권4호
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• pp.335-342
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• 2012

본 논문에서는 고효율과 고역률을 위한 새로운 DCM-ZVS 스텝 업-다운 AC-DC 컨버터에 대해 연구된다. 제안한 DCM-ZVS 컨버터에 사용된 스위칭 소자들은 새로운 유사공진 회로에 의해 소프트 스위칭 기법으로 동작되고, 펄스폭변조(PWM) 방식에 의한 전류불연속모드(DCM)로 구동된다. 제안한 컨버터의 유사공진 회로는 스텝 업-다운 인덕터와 무손실 스너버 커패시터로 구성되고, 또한 DCM에 의해 제어회로 기법과 제어회로 구성이 간단한 장점이 주어진다. 입력 교류 전류파형은 일정 스위칭 주파수에 의한 교류 입력전압의 크기에 비례한 유사 정현파형으로 된다. 그 결과, 제안한 DCM-ZVS 컨버터는 낮은 스위칭 손실과 고효율을 얻을 수 있으며, 컨버터의 입력역률은 거의 단위역률로 된다. 해석적 결과의 타당성은 다양한 컴퓨터 시뮬레이션과 실험 결과를 통해 입증된다.

• 전기학회논문지
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• 제58권7호
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• pp.1349-1355
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• 2009

This paper is studied on a novel power factor correction (PFC) AC-DC converter of high efficiency by soft switching technique. The input current waveform in the proposed converter is got to be a sinusoidal form composed of many a discontinuous pulse in proportion to the magnitude of a ac input voltage under the constant switching frequency. Therefore, the input power factor is nearly unity and the control method is simple. The proposed converter adding an electric isolation operates with a discontinuous current mode (DCM) of the reactor in order to obtain some merits of simpler control, such as fixed switching frequency, without synchronization control circuit used in continuous current mode (CCM). To achieve the soft switching (ZCS or ZVS) of control devices, the converter is constructed with a new loss-less snubber for a partial resonant circuit. It is that the switching losses are very low and the efficiency of the converter is high, Particularly, the stored energy in a loss-less snubber capacitor recovers into input side and increases input current from a resonant operation. The result is that the input power factor of the proposed converter is higher than that of a conventional PFC converter. This paper deals mainly with the circuit operations, theoretical, simulated and experimental results of the proposed PFC AC-DC converter in comparison with a conventional PFC AC-DC converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.400-402
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• 1994

This paper presents a digital implementation of delta modulation Technique for Active Power Filters. Delta modulated scheme is to control the harmonic-compensating current indirectly by adjusting the capacitor voltage to be sinusoidal. The overall control system has two feedback loops. One is the outer propotional feedback for loop regulating the dc current of active filters and the other is the inner feedback loop for maintaining the ac current waveform to be sinusoidal, and have zero power factor angle(i.e. unity power factor). The characteristics of the proposed is investigated by digital simulation using ACSL and experimental results are obtained by TMS370C756 Single-Chip Microprocessor relative to analog delta modulation technique.