• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.591-594
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• 2005

Islanding of PV systems occurs when the uitilty grid is removed but local sources continue to operate and provide power to local loads. Islanding Is one of the serious problems in an electric power system connected with dispersed power sources. Also, this scan present safety hazards and the possibility of damage to other electric equipments. If the real and reactive power of RLC load and PV system are closely matched, islanding phenomena can't be detected by the passive methods. Several active methods were proposed to detect islanding phenomena. The most effective method is SFS method which was suggested by Sandia National Laboratory. In this paper, a new anti-islanding algorithm is proposed and its validity is verified through simulation and experimental results for utility interconnection of PV system.

• 한국태양에너지학회 논문집
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• 제34권6호
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• pp.1-10
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• 2014

The efficiency of the maximum power point tracking(MPPT) of inverter which is used in grid-connected photovoltaic systems is changed according to dynamic environment conditions. Hence, this paper evaluates the performance of the proposed method and other MPPT algorithm on the basis of European Efficiency Test(EN50530). The modeling of MPPT algorithm is made by the Matlab & Simulink. In the result of simulation, the more control period is shorter, the more MPPT efficiency is higher. Also, the Proposed MPPT algorithm has higher performance than other MPPT algorithm with no regard to control period.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.659-668
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• 2018

This paper proposes an optimization approach of a grid-connected photovoltaic and wind hybrid energy system including energy storage considering voltage fluctuation in the electricity grid. A techno-economic analysis is carried out in order to minimize the size of hybrid system by considering the benefit-cost. Lithium-ion battery type is used for both managing the electricity selling to the grid and reducing voltage fluctuation. A new technique is developed to limit the voltage perturbation caused by the solar irradiance and the wind speed through determining the state-of-charge of battery for every hour of a day. Improved particle swarm optimization (PSO) methods, referred to as FC-VACPSO which combines Fast Convergence Particle Swarm Optimization (FCPSO) method and Variable Acceleration Coefficient Based Particle Swarm Optimization (VACPSO) method are used to solve the optimization problem. A comparative study has been performed between standard PSO method and PSO based methods to extract the best size with the benefit cost. A sensitivity analysis has been studied for different kinds and costs of batteries, by considering variable and constant state-ofcharge of battery. The simulations, performed under Matlab environment, yield good results using the FC-VACPSO method regarding the convergence and the benefit cost of the hybrid system.

• Journal of Power Electronics
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• 제15권1호
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• pp.256-267
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• 2015

Grid-connected transformerless photovoltaic (PV) inverters (TPVIs) are increasingly dominating the market due to their higher efficiency, lower cost, lighter weight, and reduced size when compared to their transformer based counterparts. However, due to the lack of galvanic isolation in the low voltage grid interconnections of these inverters, the PV systems become vulnerable to leakage currents flowing through the grounded star point of the distribution transformer, the earth, and the distributed parasitic capacitance of the PV modules. These leakage currents are prohibitive, since they constitute an issue for safety, reliability, protection coordination, electromagnetic compatibility, and module lifetime. This paper investigates a wide range of multi-kW range power rating TPVI topologies and classifies them in terms of their leakage current attributes. This systematic classification places most topologies under a small number of classes with basic leakage current attributes. Thus, understanding and evaluating these topologies becomes an easy task. In addition, based on these observations, new topologies with reduced leakage current characteristics are proposed in this paper. Furthermore, the important efficiency and cost determining characteristics of converters are studied to allow design engineers to include cost and efficiency as deciding factors in selecting a converter topology for PV applications.

• Journal of Power Electronics
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• 제14권6호
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• pp.1233-1242
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• 2014

A new inverter topology for single-phase photovoltaic (PV) systems is proposed in this study. The proposed inverter offers a four-level voltage in its output terminals. This feature results in easier filtering in comparison with other conventional two-level or three-level inverters. In addition, the proposed four-level inverter (PFLI) has a transformer-less topology, which decreases the size, weight, and cost of the entire system and increases the overall efficiency of the system. Although the inverter is transformer-less, it produces a negligible leakage ground current (LGC), which makes this inverter suitable for PV grid-connected applications. The performance of the proposed inverter is compared with that of a four-level neutral point clamped inverter (FLNPCI). Theoretical analysis and computer simulations verify that the PFLI topology is superior to FLNPCI in terms of efficiency and suitability for use in PV transformer-less systems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.327-330
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• 2003

The frequency and Phase angle of the utility voltage are important in many industrial systems. In this paper, the analysis and generalized approach of single-phase PLL control have been presented. The experimental results have been presented and demonstrated the feasibility of proposed methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.1159-1160
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• 2006

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, this has raised potential problems of network protection on electrical power system. One of the numerous problems is an Island phenomenon. There has been an argument that because the probability of islanding is extremely low it may be a non-issue in practice. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an island can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficient to cause a trip, plus the time required to execute the trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. And, third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an island. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. So the verification of anti-islanding performance is strongly needed. In this paper, the authors propose the improved RPV method through considering power quality and anti-islanding capacity of grid-connected three-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"). And the simulation and experimental results are verified.

• 한국정보통신학회논문지
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• 제11권3호
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• pp.532-539
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• 2007

신재생 에너지 자원의 하나로 각광받고 있는 태양광발전시스템은 분산형 발전시스템으로서 설치 이후의 효율적인 시스템 관리와 운영이 중요한 문제로 대두되고 있다. 이러한 문제점을 해결할 수 있는 방법 중 하나는 원격 모니터링 및 제어 시스템을 적용하는 것이다. 본 논문에서는 태양광 발전 시스템의 효율적인 관리와 운용을 위한 LabVIEW 기반의 모니터링 및 제어시스템을 제안한다. 모니터링부와 태양광 인버터의 DSP(Digital Signal Processor) 제어기간의 인터페이스에 대하여 자세히 설명하고, 계통연계형 태양광발전시스템에 적용하여 제안된 시스템의 타당성을 검증한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.65-68
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• 2003

3kW grid-connected photovoltaic(PV) systems and data acquisition system are constructed for performance analysis of PV system at field demonstration test center of Gwang-Ju in Korea. As climatic and irradiation conditions are varied, operation characteristics of the PV system are collected and analyzed in data acquisition system. From these results, the performances of PV systems have simulated and evaluated using simulation tool In comparison with actual value of data acquisition system of field demonstration test center. Furthermore, performance of each PV system e.g. electric power and loss factor is reviewed.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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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.