• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.476-479
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• 2001

Interconnection of new energy sources, such as photovoltaic generation, wind power generation, etc., into the electric power distribution system may result in the increasing short-circuit capacity when a short circuit fault occurs. The short-circuit capacity becomes over the interrupting ratings of circuit breakers, and then they fails to operate in the proper way they prevent fault currents from flowing into the distribution facilities and thus causing them serious damages. This study deals with impacts on the respective short-circuit capacity of both low voltage and extra high voltage distribution systems at which new energy sources are installed. In order to obtain more accurate and all-case values very close to reality in the complicated distribution system, computer simulation tools should be required. In this paper, however, its focus is placed on examining the varying trend of short-circuit capacity, which may happen owing to new energy source interconnection, as a previewing step for exhaustive simulation studies.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.937-944
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• 2022

Electric vehicles (EVs) have been growing to reduce energy consumption and greenhouse gas (GHG) emissions in the transportation sector. The increasing number of EVs requires adequate recharging infrastructure, and at the same time, adopts low- or zero-emission electricity production because the GHG emissions are highly dependent on primary sources of electricity production. Although previous research has studied solar photovoltaic (PV) -integrated EV charging stations, it is challenging to optimize spatial areas between where the charging stations are required and where the renewable energy sources (i.e., solar photovoltaic (PV)) are accessible. Therefore, the primary objective of this research is to support decisions of siting EV charging stations using a spatial data clustering method integrated with Geographic Information System (GIS). This research explores spatial relationships of PV power outputs (i.e., supply) and traffic flow (i.e., demand) and tests a community in the state of Indiana, USA for optimal sitting of EV charging stations. Under the assumption that EV charging stations should be placed where the potential electricity production and traffic flow are high to match supply and demand, this research identified three areas for installing EV charging stations powered by rooftop PV in the study area. The proposed strategies will drive the transition of existing energy infrastructure into decentralized power systems. This research will ultimately contribute to enhancing economic efficiency and environmental sustainability by enabling significant reductions in electricity distribution loss and GHG emissions driven by transportation energy.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.1
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• pp.129-133
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• 2010

A hybrid system which is combined several complementary new and renewable power sources, such as photovoltaic, fuel-cell, and wind generator, etc., has been presented in various approaches. For instance, a photovoltaic cannot always generate stable output power with ever-changing weather condition, so it might be co-generated with a wind generator, diesel generator, and some other sources. In this paper, a residential PV-FC hybrid system is suggested as a distribution power source, and its operation is optimized by HOMER$^{(R)}$. As a result, it is the most economic that 5[kW] PV, 1[kW] FC, 4 batteries, 2[kW] electrolyzer, 0.5[kg] $H_2$ tank, 3[kW] converter are applied to the hybrid system.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.44-45
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• 2011

Research on photovoltaic (PV) generation is taking a lot of attention due to its infinity and environment-friendliness with decrease of price per PV cell. While central inverters connect group of PV modules to utility grid in which maximum power point tracking (MPPT) for each module is difficult, micro inverter is attached on each module so that MPPT for individual modules can be easily achieved. Moreover, energy generation and consumption efficiency can be much improved by employing direct current (DC) distribution system. In this paper, a digitally controlled PV micro converter interfacing PV to DC distribution system is proposed. Boundary conduction mode (BCM) is utilized to achieve zero voltage switching (ZVS) of active switch and eliminate reverse recovery problem of passive switch. A 120W prototype boost PV micro converter is implemented to verify the feasibility and experimental results show higher than 98% efficiency at peak power and 97.29% of European efficiency.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.312-317
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• 2007

최근 다수의 태양광 발전기가 배전계통에 연계되고 있으며 특히, 특정지역을 중심으로 대규모의 태양광발전 단지가 구성되어 배전계통에 연계되고 실정이다. 본 논문에서는 순천에 구축된 l000KW급 태양광발전소의 계통해석영향을 분석하기 위하여 PSCAD/EMTDC 툴을 이용하여 모델링 하고 태양광발전이 연계된 배전계통 조류해석과 태양광 발전의 출력에 의한 22.9KV 배전계통의 전압변동을 시뮬레이션 하였으며, 태양광발전에 따른 역조류에 의한 배전계통 전압변동을 분석하였다. 또한, 태양광발전기의 배전계통 연계 전,후의 배전선로의 임의의 지락고장 모의로 태양광발전기가 고장전류에 미치는 영향 분석과 태양광 발전이 양호, 불량한 경우에 대한 상전압, 고조파 전류, 역률 등의 측정결과에 의한 전력품질을 분석 하였다.

• Proceedings of the KIEE Conference
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• summer
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• pp.548-550
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• 2004

This paper suggests a methodology for calculation of photovoltaic(PV) generation system output using probability distribution function, PV way efficiency and PV system design Parameters. Long term irradiance recorded for every hour of the day for 11 years were used. For goodness-fit test, several distribution functions are tested by Kolmogorov- Smirnov(K-S) test. And the calculated generation output is compared with that of CMS(Centered Monitoring System), which can monitoring PV generation output of each PV generation site.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.581-584
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• 2014

In this paper, a micro-scale photovoltaic(PV) energy harvesting system is proposed where an MPPT(Maximum Power Point Tracking) control is implemented using an energy distribution technique. Miniature PV cells output very low energy and low voltages, and thus, they cannot be used to directly power the MPPT controller. In the proposed system, a start-up circuit boosts an internal Vcp, and the boosted Vcp is used to operate the internal MPPT control block. When the Vcp reaches a predefined value, a detector circuit makes the start-up block turn off and provide a power converter with the energy from the PV cell. When the Vcp decreases such that the MPPT controller can not be operated, the energy transferred to the power converter is blocked and the start-up circuit is reactivated. In this way, the MPPT function is achieved by alternately operating the start-up circuit and the power converter using the energy distribution technique, and the harvested energy is transferred to a load through a PMU(Power Management Unit). The proposed circuit is designed in a 0.35um CMOS process and its functionality has been verified through extensive simulations. The designed chip area including pads is $1430um{\times}1110um$.

• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.99-106
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• 2011

Since the solar energy resource is the main input for sizing any solar photovoltaic system, it is essential to utilize the solar radiation data as an application and development of solar energy system increase. It will be necessary to understand and evaluate the insolation data. The Korea Institute of Energy Research(KIER) has begun collecting horizontal global insolation data since May, 1982 at 16 different locations in Korea and for the more detailed analysis, images taken by geostationary satellite may be used to estimate solar irradiance fluxes at earth"s surface. It is based on the empirical correlation between a satellite derived cloud index and the irradiance at the ground. From the results, the measured data has been collected at 16 different stations and estimated using satellite at 23 different stations over the South Korea from 1982 to 2009. The Result of analysis shows that the annual-average daily global radiation on the horizontal surface is 3.56 kWh/ $m^2$/day and estimated solar radiation fluxes show reliable results for estimating the global radiation with average deviation of -7.27 to +3.65% from the measured values.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.573-579
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• 2011

Highly textured Ag, Al and Al:Si back reflectors for flexible n-i-p silicon thin-film solar cells were prepared on 100-${\mu}m$-thick stainless steel substrates by DC magnetron sputtering and the influence of their surface textures on the light-scattering properties were investigated. The surface texture of the metal back reflectors was influenced by the increased grain size and by the bimodal distribution that arose due to the abnormal grain growth at elevated deposition temperatures. This can be explained by the structure zone model (SZM). With an increase in the deposition temperatures from room temperature to $500^{\circ}C$, the surface roughness of the Al:Si films increased from 11 nm to 95 nm, whereas that of the pure Ag films increased from 6 nm to 47 nm at the same deposition temperature. Although Al:Si back reflectors with larger surface feature dimensions than pure Ag can be fabricated at lower deposition temperatures due to the lower melting point and the Si impurity drag effect, they show poor total and diffuse reflectance, resulting from the low reflectivity and reflection loss on the textured surface. For a further improvement of the light-trapping efficiency in solar cells, a new type of back reflector consisting of Ag/Al:Si bilayer is suggested. The surface morphology and reflectance of this reflector are closely dependent on the Al:Si bottom layer and the Ag top layer. The relationship between the surface topography and the light-scattering properties of the bilayer back reflectors is also reported in this paper.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.234-235
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• 2013

Recently, interest in renewable energy is rising in rural areas in order to reduce heating and air-conditioning costs which are directly connected to farmhouse income. Thus, in this paper, I study renewable energy supporting projects in rural area: I analyze distribution of the Agriculture & Fishery Energy use Efficiency Project and 1 Million the Green Homes program by using project performance data and the data of Korea Energy Handbook. The results of my analysis of the two programs show that, while annual average increase of the 1 million Green homes prgram is 15.6%, the distribution rate of heating and air-conditioning facilities using geothermal heating and cooling system of the project has decreased by average 37% every year.