• 전력전자학회논문지
• /
• 제19권1호
• /
• pp.31-40
• /
• 2014

This paper describes an optimal configuration for multi-central inverters in a medium-voltage (MV) grid, which is suitable for large-scale photovoltaic (PV) power plants. We theoretically analyze a proposed common-mode equivalent model for problems associated with multi-central transformerless-type three-phase full bridge(3-FB) PV inverters employing two-winding MV transformers. We propose a synchronized PWM control strategy to effectively reduce the common-mode voltages that may simultaneously occur. In addition, we propose that the existing 3-FB topology may also have the configuration of a multi-central inverter with a two-winding MV transformer by making a simple circuit modification. Simulation and experimental results of three 350kW PV inverters in a multi-central configuration verify the effectiveness of the proposed synchronization control strategy. The modified transformerless-type 3-FB topology for a multi-central PV inverter configuration is verified using an experimental prototype of a 100kW PV inverter.

• KSBB Journal
• /
• 제6권2호
• /
• pp.181-187
• /
• 1991

본 연구에서는 PV에 아나베나세포를 흡착법에 의하여 고정화하였다. 진탕배양하면서 고정화한 겨웅에 비하여 반응기속에 배양액을 trickling 시키면서 배양하고 고정한 경우 높은 세포밀도를 보였다. PV에 고정화한 세포들의 생리적 활성을 조사한 결과 광합성능이 암처보관시에 free cell에 비하여 안정됨을 보였고, msx처리시의 암모니아의 방출도 증가하였다. 뿐만 아니라 고정화한 세포에서 광합성활성의 온도에 대한 내성이 증가하였으며 nitrogenase 효소 활성도 free cell에 비하여 크게 증가하였다. nitrogenase효소에 의한 연속적인 광수소발생을 조사한 결과 혐기적 조건하에서 연속적으로 수소가 생성됨을 볼 수 있었는데 그 발생양은 4mg의 엽록소에 해당하는 아나베나를 충진한 trickling-medium 반응기에서 6일동안 1.6ml의수소가 생성되었다.

• 식물병연구
• /
• 제18권2호
• /
• pp.129-132
• /
• 2012

Citrus bacterial canker is an economically important disease affecting citrus production in many citrusgrowing areas and several pathotypes have been recognized within the Xanthomonas pathogens causing canker. In view of the containment of the disease, accurate identification of the causal bacterium is important. In this study, triplex PCR method was developed by using the previously reported primers. Two groups of primer combination, such as, one group including primers 2/3, J-pth1/J-pth2 and XACF/XACR, and another group 2/3, J-pth1/J-pth2 and Xac01/Xac02, were suitable for the detection and differentiation of X. a. pv. citri $A^w$, X. a. pv. aurantifolii B and C, and X. a. pv. citrumelo E strains. Moreover, the primer combination of Xac01 and J-pth2 promised us to use as a specific primer set to detect X. a. pv. citrumelo E strain. The PCR methods developed in this study could be used for the rapid differentiation of Xanthomonas pathotypes of citrus.

• Advances in nano research
• /
• 제13권5호
• /
• pp.475-485
• /
• 2022

Crystalline silicon photovoltaic cells have advantages of zero pollution, large scale and high reliability. A major challenge is that sunlight wavelength with photon energy lower than semiconductor band gap is converted into heat and increase its temperature and reduce its conversion efficiency. Traditional cooling PV method is using water flowing below the modules to cool down PV temperature. In this paper, the idea is proposed to reduce the temperature of the module and improve the energy conversion efficiency of the module through the modulation of the solar spectrum. A spectrally selective nanofilm reflector located directly on the surface of PV is designed, which can reflect sunlight wavelength with low photon energy, and even enhance absorption of sunlight wavelength with high photon energy. The results indicate that nanofilm reflector can reduce spectral reflectivity integral from 9.0% to 6.93% in 400~1100 nm wavelength range, and improve spectral reflectivity integral from 23.1% to 78.34% in long wavelength range. The nanofilm reflector can reduce temperature of PV by 4.51℃ and relatively improved energy conversion efficiency of PV by 1.25% when solar irradiance is 1000 W/m². Furthermore, the nanofilm reflector is insensitive in sunlight's angle and polarization state, and be suitable for high irradiance environment.

• 한국환경농학회지
• /
• 제24권4호
• /
• pp.350-357
• /
• 2005

농약별 수직이동 양상을 파악하고, 흡착계수와 토양관련 매개변수를 이용하여 대류이동성 모형(Convective mobility test model)으로 예측한 용탈 속도와 비교 평가하기 위하여 강서통(논), 중동통(밭), 예산통(산림토양) 및 신엄통(화산회토)을 사용하여 카바메이트계 농약 metolcarb, molinate, fenobucarb 및 dimepiperate와 유기인계 농약 isazofos, diazinon, fenitrothion, parathion 및 chlorpyrifos-methyl의 도주용탈실험을 수행하였다. 각 농약을 $50{\mu}g/cm^2$ 수준으로 토주 상단에 처리하였을 때 토심 10 cm 이동 후 용탈되는 농약별 최대용탈(peak) 농도는 화산회토를 제외한 3종 토양의 경우 metolcarb $6.5{\sim}12.6mg/L$, molinate $2.6{\sim}5.0mg/L$, fenobucarb $4.5{\sim}7.8mg/L$, dimepiperate $0.39{\sim}1.36mg/L$ isazofos $1.1{\sim}4.6mg/L$, diazinon $0.01{\sim}0.14mg/L$, fenitrothion 0.01 mg/L 미만${\sim}0.70mg/L$ 및 parathion 0.01 mg/L 미만${\sim}0.44mg/L$ 수준이었고 chloipyrifos-methyl은 네 토양 모두에서 용탈되지 않았다. Peak 농도 출현까지 소요된 용탈수량은 metolcarb $1.1{\sim}2.1$ pore volume(PV), molinate $1.6{\sim}3.3$ PV, fenobucarb $1.6{\sim}3.3$ PV, isazofos $2.1{\sim}4.4$ PV, diazinon $6{\sim}15$ PV 및 dimepiperate $8{\sim}21$ PV 수준이었다. 대류이동성 모형에 의한 예측결과는 대부분의 토양-농약 조합에서 토주용탈 양상과 일치하였고 표준조건(water flux 1 cm/일)에서 예측된 이동소요시간에 따라 metolcarb는 most mobile, molinate와 fenobucarb, isazofos는 mobile내지 most mobile, dimepiperate는 moderately mobile이나 mobile, diazinon은 mobile, fenitrothion과 parathion은 slightly mobile 또는 mobile, chloipyrifos-methyl은 immobile이나 slightly mobile 등급에 속하는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
• /
• 제7권2호
• /
• pp.108-110
• /
• 1986

The solution epr spectra of ${\alpha}-1,2,3-[H_nPV(IV)V_2W_9O_{40}]^{(7-n)-}$were measured at various pH and three protonated species have been identified. The spectrum of $H_3PV(IV)Ⅴ_2$ consisting of 8 lines indicates that the V-OH-V bridge prevents effectively the electron transfer between the vanadium atoms. The spectrum of $H_2PV(IV)V_2$ consisting of 15 lines can be interpreted by assuming that the electron is hopping fast between the two vanadium atoms in the V-O-V sequence. The multi-line spectrum of $HPV(IV)V_2$ is interpreted as a poorly resolved 43-line spectrum which originates from the electron hopping among the three vanadium atoms with the forward and backward transition probabilities of 4:1 in the OH-V-O-V sequence.

• 신재생에너지
• /
• 제16권1호
• /
• pp.47-57
• /
• 2020

In Floating PV (Photovoltaic) systems, PV modules are installed on water by utilizing the surface of idle water such as a reservoir and multipurpose dam. A floating PV system, therefore, has the advantage of efficiency in national land use and improved energy yield owing to cooling effect compared to on-land PV systems. Owing to the limitation of installation environment for a floating PV system, the system, however, has the disadvantage of an increase in transmission distance of DC (Direct current) cables. A longer transmission distance of a DC cable results in greater power loss due to a voltage drop. This leads to a decline in economic feasibility for the floating PV system. In this paper, the economic analysis for 10 floating PV systems installed in a reservoir has been conducted in terms of a change in annual power sales according to the variation of transmission losses depending on the factors affecting the voltage drop, such as transmission distance, cross-section area of underwater cable, the presence of joint box, and PV capacity.

• 한국공간구조학회논문집
• /
• 제10권1호
• /
• pp.67-74
• /
• 2010

국내에 설치될 강구조 스타디움에 향후 신재생에너지 중 하나인 태양광 발전을 위한 PV 시스템을 적용하는 것에 따른 강재 어레이에 관한 기초 연구로 해외의 사례를 토대로 구성되었다. 연구를 진행하기 위하여 1990년대 이후 PV 시스템이 적용된 강구조 스타디움 20건을 사례 분석 대상으로 선정하였다. 선정된 20건의 강구조 스타디움을 PV 모듈을 고정하기 위하여 설치된 레일 시스템에 따라 분류해 보았다. 그 결과 격자고정방식 중 선형모듈고정방식과 지붕 통합형이 전체의 28%에 해당되는 것으로 조사되었으며 그 뒤로 레일 고정형 17%, 세로 고정방식 중 모듈그룹 고정 11% 순으로 조사되었다. 또한 스타디움 내부에는 주로 격자 고정방식 중 선형모듈 고정방식과 지붕통합형이 적용되고 있었으며 스타디움 외부나 그 외 부분에서는 앵글 브라킷으로 PV 모듈이 고정되고 있는 것으로 조사되었다.

• 전기전자학회논문지
• /
• 제27권4호
• /
• pp.657-667
• /
• 2023

배전계통에 연계되는 분산전원의 수가 증가함에 따라 계통 내 과전압 문제를 일으키지 않고 접속될 수 있는 한계접속용량인 photovoltaic(PV) hosting capacity(HC)를 추정하는 것이 매우 중요해졌다. 이에 본 연구에서는 접속점의 전압을 유지하는 제어를 수행하면서 향상된 hosting capacity를 추정하기 위한 방안을 제안하고 있다. 제안된 방안은 two-stage optimization framework로 구성되며 Stage 1에서 IEEE Std 1547-2018 가이드라인을 이용한 Volt-Var(VV) 및 Volt-Watt(VW) 제어 PV hosting capacity 추정을 수행한다. Stage 2에서는 VV 및 VW의 파라미터를 개선하는 절차를 거쳐 향상된 PV HC 값을 다시 도출해낸다. 제안한 방식의 성능 검증을 위해 IEEE 37-버스 시스템이 OpenDSS를 사용해 테스트되었으며 결과에서 제안된 방식의 적용을 통해 PV hosting capacity가 증가함을 확인하였다.

• Advances in Energy Research
• /
• 제4권1호
• /
• pp.1-28
• /
• 2016

A grid-connected photovoltaic (PV) system comprised of multicrystalline silicon (mc-Si) modules was installed in a cold climate region in the U.S. This roof-mounted stationary PV system is a real-world application of PV for building energy generation in International Energy Conservation Code (IECC) Climate Zone 5 (and possibly similar climate zones such as 6, 7 and 8), and it served the purposes of research, demonstration, and education. The importance of this work is highlighted by the fact that there has been less emphasis on solar PV system in this region of the U.S. because of climate and latitude challenges. The system is equipped with an extensive data acquisition system capable of collecting performance and meteorological data while visually displaying real-time and historical data through an interactive online interface. Experimental data was collected and analyzed for the system over a one-year period with the focus of the study being on measurements of power production, energy generation, and efficiency. The annual average daily solar insolation incident upon the array was found to be $4.37kWh/m^2$. During the first year of operation, the PV system provided 5,801 kWh (1,264 kWh/kWp) of usable AC electrical energy, and it was found to operate at an annual average conversion efficiency and PR of 10.6 percent and 0.79, respectively. The annual average DC to AC conversion efficiency of the inverter was found to be 94 percent.