• Journal of IKEEE
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• v.24 no.1
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• pp.364-367
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• 2020

This paper presents the off-grid PV-ESS system of sequential voltage control method applied to OR logic gate. The conventional off-grid PV-ESS system with the low-voltage series connection has problems due to capacity expansion. To solve these problems, this paper proposes a noble PV-ESS system with high efficiency and low cost by applying sequential voltage control technique of the high-voltage series connection of analog circuit type. The input voltage of DC to AC inverter can be converted from the low-voltage by the combinations of series connection of the conventional cascaded 24V solar cell unit modules to the high-voltage of 384V in battery. The output voltage of the battery was 384V as the each input voltage of three phase DC to AC inverter, and the each output voltage of three phase 10kW DC to AC inverter is designed to be AC380V@60Hz as the line to line rms voltage value. To prove the validity of the theoretical analysis by PSIM simulation, the operating characteristics of sequential voltage control system with OR logic gate were confirmed through experiment results.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.2
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• pp.321-326
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• 2012

The mechanism unit, arc chamber and trip unit are imperative components of MCCB which will decide the level of performance of MCCB. Among them, Arc chamber unit is used for extinguishing arc rapidly of fault current and induce the arc inside of grid. At that time inducing arc will split into parts and cooled rapidly so the arc would disappear. This paper suggests new arc chamber unit to improve arc extinguishing performance with optimum design and are applied to actual products based on the results.

• Journal of Digital Convergence
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• v.20 no.2
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• pp.217-223
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• 2022

Subspace clustering for online data streams requires a large amount of memory resources as all subsets of data dimensions must be examined. In order to track the continuous change of clusters for a data stream in a finite memory space, in this paper, we propose a grid-based subspace clustering algorithm that effectively uses memory resources. Given an n-dimensional data stream, the distribution information of data items in data space is monitored by a grid-cell list. When the frequency of data items in the grid-cell list of the first level is high and it becomes a unit grid-cell, the grid-cell list of the next level is created as a child node in order to find clusters of all possible subspaces from the grid-cell. In this way, a maximum n-level grid-cell subspace tree is constructed, and a k-dimensional subspace cluster can be found at the k^th level of the subspace grid-cell tree. Through experiments, it was confirmed that the proposed method uses computing resources more efficiently by expanding only the dense space while maintaining the same accuracy as the existing method.

• ETRI Journal
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• v.42 no.4
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• pp.585-595
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• 2020

Integration of multiple communication technologies in a smart grid (SG) enables employing cognitive radio (CR) technology for improving reliability and security with low latency by adaptively and effectively allocating spectral resources. The versatile features of the CR enable the smart meter to select either the unlicensed or the licensed band for transmitting data to the utility company, thus reducing communication outage. Demand response management is regarded as the control unit of the SG that balances the load by regulating the real-time price that benefits both the utility company and consumers. In this study, joint allocation of the transmission power to the smart meter and consumer's demand is formulated as a two stage multi-armed bandit game in which the players select their optimal strategies noncooperatively without having any prior information about the media. Furthermore, based on historical rewards of the player, a real-time pricing adaptation method is proposed. The latter is validated through numerical results.

• Journal of the Korea Society for Simulation
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• v.12 no.4
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• pp.51-59
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• 2003

Real-Time applications on Grid environment have several problems in terms of resource management addressed as follows; (1) dynamic resource allocation to provide QoS objectives, (2) heterogeneous resources that is different scale, or capacity in same unit, and (3) resource availability, and resource needs. This paper describes the techniques of resource manager (RM) handling above problems to support QoS of dynamic real-time applications on Grid. The contributions of this paper to solve problems are as follows: unification of dynamic resource requirements among heterogeneous hosts, control of resources in heterogeneous environments, and dynamic load balancing/sharing. Our heuristic allocation scheme works not only 257% better than random, 142% better than round robin, and 36.4% better than least load in QoS sensitivity, but also 38.6% better than random, 28.5% better than round robin, and 31.6% better than least load in QoS.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.159-162
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• 2011

스마트그리드는 기존의 전력 생산, 운반, 소비의 과정에 정보통신 기술을 접목하여 에너지 절감 및 전기 품질 향상 등을 제공하는 차세대 전력망으로써 스마트 미터 중심의 AMI, 에너지 관리 시스템, 전기 자동차 및 충전소, 재생에너지, 양방향 정보통신 기술, 배전 자동화 시스템 등으로 구성된다. 이중 미터기, 수용가 전력기기, 근거리 통신기술, 데이터 관리 시스템 등은 "제주도 실증단지구축"사업의 핵심 요소로써, 국내 기업들의 활발한 연구가 이루어지고 있다. 하지만 국내에서 연구되고 있는 스마트그리드 구축과 관련된 소프트웨어들은 외산 솔루션에 기반하고 있거나 자체개발을 통해 이루어지고 있어 기술 지원 부재 및 개발 소요 시간이 길다는 문제점을 가지고 있다. 따라서 본 논문에서는 이러한 문제점을 해결하기 위해 오픈 소스 소프트웨어 기반의 스마트그리드 통합시설관제시스템을 제안하고, 구축하도록 한다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.1
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• pp.57-62
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• 2005

Grid-connected photovoltaic (PV) systems were installed and monitored at the field demonstration test center (FDTC) in Korea in October 2002. Before long-term field testing of installed PV systems, the performances of PV components were evaluated and compared through short-term performance tests of each of the PV system components such as power conditioning system and PV module under standard test conditions. A data acquisition system has been constructed for measuring and analyzing the performance of PV systems to observe the overall effect of environmental conditions on their operation characteristics. Performances of PV systems have been evaluated and analyzed not only for component perspective (PV array, power conditioning unit) but also for global perspective (system efficiency, capacity factor, electrical power energy) by review of the field test and loss factors of the systems. These results indicate that it is highly imperative to develop an optimum design technology of grid connected PV systems. The objective of this paper is not only to evaluate and analyze the performance of domestic PV systems application through long-term field testing at FDTC but also to develop evaluation, analysis and optimum technology for long-term stability and reliability of grid-connected PV systems in Korea.

• Journal of Information Technology Services
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• v.11 no.sup
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• pp.41-50
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• 2012

With the recent advances in smart grid technologies and the increasing dissemination of smart meters, the power usage of each time unit can be detected in modern smart building environments. Thus, the utility company can adopt different price of electricity at each time slot considering the peak time. Korea government also announces the smart-grid roadmap that includes a law for realtime price of electricity. In this paper, we propose an efficient power scheduling scheme for smart buildings that adopt smart meters and real-time pricing of electricity. Our scheme dynamically changes the power mode of each consumer device according to the change of power rates. Specifically, we analyze the electricity demands and prices at each time, and then perform real-time power scheduling of consumer devices based on collaboration of each device. Experimental results show that the proposed scheme reduces the electricity charge of a smart building by up to 36.4%.

• Proceedings of the Zoological Society Korea Conference
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• 1997.10a
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• pp.42-57
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• 1997

The multicriterion matrix technique (MM-technique) was proposed for a method of monitoring and assessment about vegetation naturalness. Four criteria and 10 subcriteria were selected and two evaluation indices such as VN-value and VN-class were used. The criteria were characterized by syntaxonomical informations of hemeroby concept and potential natural vegetation, hierarchical system between criteria, and ordinal scale of VN-values. VN-values were classified into 11 ordinal levels and condensed to five VN-classes for facilitating practical use. A vegetation map of naturalness described by combination o( two indices was proposed as an alternative resolution of the DGN map. We also discuss the organization of the map content which is a matter of grid size (unit-area). In the case study, a grid size proper to show a full account of real information of actual vegetation is less 250-grid (250 $\times$ 250 $m^2$) in a medium size of city area containing relatively fragmented ecosystems. In conclusion, it was recognized that this new assessment technique was useful and vegetation assessment was accomplished with the smaller grid size in Korea.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1807-1813
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• 2018

In this paper, the fault line selection and location problems of single line-to-ground (SLG) fault in distribution network are addressed. Firstly, the adaptive filtering property for empirical mode decomposition is formulated. Then in view of the different characteristics showed by the intrinsic mode functions(IMF) under different fault inception angles obtained by empirical mode decomposition, the sign of peak value about the low-frequency IMF and the capacitance transient energy is chosen as the fault line selection criteria according to the different proportion occupied by the low-frequency components. Finally, the fault location is determined based upon the comparison result with adjacent fault passage indicators' (FPI) waveform on the strength of the interaction between the distribution terminal unit(DTU) and the FPI. Moreover, the logic nodes regarding to fault line selection and location are newly expanded according to IEC61850, which also provides reference to acquaint the DTU or FPI's function and monitoring. The simulation results validate the effectiveness of the proposed fault line selection and location methods.