• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.172-174
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• 2007

The AC-DC Adapter has been widely used in Mobile Phones, Note Book PC, LCD monitors, and portable electronic products. Recently, high-power-density Adapter was developed. This adapter increases power factor using a bridge diode rectifier and PFC, however, there are weak points that improving efficiency is limited. In the bridgeless rectifier circuit proposed in this paper, there is no PFC, however, the power factor and efficiency are improved by BCM and ZCS operations.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.477-482
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• 2021

Hydrogen production, hydrogen production cost, and utilization rate were calculated assuming four cases of hydrogen production system in combination of photovoltaic power generation (PV), water electrolysis system (WE), battery energy storage system (BESS), and power grid. In the case of using the PV and WE in direct connection, the smaller the capacity of the WE, the higher the capacity factor rate and the lower the hydrogen production cost. When PV and WE are directly connected, hydrogen production occurs intermittently according to time zones and seasons. In addition to the connection of PV and WE, if BESS and power grid connection are added, the capacity factor of WE can be 100%, and stable hydrogen production is possible. If BESS is additionally installed, hydrogen production cost increases due to increase in Capital Expenditures, and Operating Expenditure also increases slightly due to charging and discharging loss. Even in a hydrogen production system that connects PV and WE, linking with power grid is advantageous in terms of stable hydrogen production and improvement of capacity factor.

• 동력기계공학회지
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• 제8권2호
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• pp.5-11
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• 2004

The failure frequency of the Emergency Diesel Generator(EDG) at Nuclear Power Plants(NPPs) is not so much lower than that of the Marine engines, whereas the running hours of the diesel engine at NPPs is much less than those of the engines for commercial service. The primary factor results from the severe surveillance test requirements such as fast start, large number of starting test, fast load-run, high load running, etc. The other factor comes from the excessive maintenance based on the engine maker's instruction manual that did not incorporate the peculiar characteristics of the diesel engines at NPPs. In this paper, the present preventive maintenance program on the basis of the Pielstick diesel engines was reviewed for the purpose of securing the reliability of the emergency diesel generator at NPPs and the ways for its improvement were presented by referring to the overseas cases for their applications.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.227-228
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• 2012

In interfaces between carbon black or Pt and FTO glass in dye-sensitized solar cell counter electrodes, a marginal resistant channel for electrons, we tried to improve the connection by modifying the sintering process. A stepwise sintering process for carbon black and Pt counter electrodes was applied and its effect on power conversion efficiency was studied. Power conversion efficiencies of built-in DSSC made by a one-step sintering process with carbon black and Pt counter electrodes were about 5.01% and 5.02%, respectively. Cells made with the stepwise sintering process were 5.96% and 6.21%, respectively, indicating an 20% improvement. Fill factor (FF) increased, and it was them main reason for the power conversion efficiency improvement. Step wise sintering increased the adhesion of the interface and reduced the film thickness and surface roughness. As a result, the resistivity of the counter electrode and EIS impedance of DSSCs decreased.

• 한국정보전자통신기술학회논문지
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• 제2권4호
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• pp.13-18
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• 2009

본 연구는 DGS 결합 구조를 이용하여 고조파 억압 특성을 향상시키기 위하여 전력증폭기의 효율을 높이기 위한 방법을 제안하였다. 고조파 성분과 연관된 효율성은 전력 증폭기를 설계하는데 있어서의 중요한 요인 중의 하나이다. 그러므로 주기적인 슬릿이나 스터브를 갖는 DGS 전송선로를 전력 증폭기의 후단에 먼저 설계하고 결합함으로써 고조파의 효과적인 억압 특성을 가지며 효율을 높힐 수 있게 됨을 알 수가 있었다. 따라서 보 연구에서는 WCDMA용 전력 증폭기에 적용한 결과 효율성을 위한 측정 실험에 있어서 을 한 결과 PAE 보다 6%의 효율 향상을 얻을 수가 있었음을 보여주었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 추계학술대회
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• pp.169-170
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• 2011

PFC(Power Factor Correction) converters are commonly designed for CCM(Continuous Conduction Mode). However, DCM(Discontinuous Conduction Mode) appears in the input current near the ZCP(Zero Crossing Point) at light loads, resulting in input current distortion. It is caused by inaccurate average current values obtained in DCM. This paper studies a simple digital control scheme that can be operated in both CCM and DCM with minimal changes to the CCM average current control structure.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.395-397
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• 1999

This paper presents a method of improving the power factor and the waveform of A.C line currents and the out waveforms of AC to DC fully bridge converter systems which is achieved by connecting converters in series and parallel. The results of simulation show that the power factor and the source voltage and current waveforms are improved by the method of connecting converter in series, and the controlled input voltage and current waveform using a current limit controller.

• 한국조명전기설비학회지:조명전기설비
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• 제6권6호
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• pp.42-48
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• 1992

This paper shows a reasonable design standard of substation facility density and demand factor in office buildings, that was made by the systematic and statistical way considering actual conditions, such as investigated electric equipment capacity, electric power consumption, etc for 121 buildings. The saving of electric equipment investment, the decrease of power loss, the improvement of facilities utilization and the decrease of electric power rates an be contributed by the application of the design standard must be applied by the revision of current regulations and laws.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.207-216
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• 2017

Wind energy conversion systems (WECS) which consist of wind turbines with permanent magnet synchronous generator (PMSG) and full-power converters have become widespread in the field of renewable power systems. Generally, conventional diode bridge rectifiers have used to obtain a constant DC bus voltage from output of PMSG based wind generator. In recent years, together advanced power electronics technology, Pulse Width Modulation (PWM) rectifiers have used in WECS. PWM rectifiers are used in many applications thanks to their characteristics such as high power factor and low harmonic distortion. In general, L, LC and LCL-type filter configurations are used in these rectifiers. These filter configurations are not exactly compensate current and voltage harmonics. This study proposes a hybrid passive filter configuration for PWM rectifiers instead of existing filters. The performance of hybrid passive filter was tested via MATLAB/Simulink environment under various operational conditions and was compared with LCL filter structure. In addition, neuro-fuzzy controller (NFC) was preferred to increase the performance of PWM rectifier in DC bus voltage control against disturbances because of its robust and nonlinear structure. The study demonstrates that the hybrid passive filter configuration proposed in this study successfully compensates current and voltage harmonics, and improves total harmonic distortion and true power factor.

• 조명전기설비학회논문지
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• 제27권3호
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• pp.16-25
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• 2013

Now it's a trend to install a series of white fluorescent light and orange high pressure sodium lamps because tunnel lighting should be opaque to the safety of drivers from soot, dust, humidity, and fog. Also fluorescent lighting is replaced to LED due to the fact that it improves amenity and object recognition and LED lighting has gradually been improved its nature. In this paper, we have implemented the circuits of the yellow series of high-pressure sodium lamps and white series of LED lights at one board to improve the transparency and recognition of objects. It is possible for inductive high-pressure sodium lamps and the capacitive LED drivers to circuit without power factor compensation. Two circuit parts share only a small number of parts, so low cost LED drivers compared to conventional ones are possible. Therefore, the implementation of the hybrid lighting with high-pressure sodium lamps and LED lights that can be driven at the same time by one driving circuit is possible. The LED capacitive power factor was 0.91 while individually implemented the sodium lamp power factor was 0.98. It shows not only the 2% improvement of hybrid forms but also the efficiency and THD.