• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.188.1-188.1
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• 2010

This paper describes the effort for the development of an actual wind simulation method on the wind turbine performance evaluation. It should be emphasized that the deep knowledge on real wind field is a key factor for both the design of a wind turbine and the performance evaluation. With this reason, there had been several simulation attempts to accurately match with the actual wind data. With an existing wind generation algorithm is under consideration, this study introduces several more new concepts including Van der Hoven spectrum being implemented in different methodology. Also this paper will compare the result from the wind simulations by using the basic formula with that by using MATLAB and SIMULINK previously developed. In addition, like the existing wind generation algorithm, random process for actual wind field simulation and white noise are incorporated to closely produce the actual wind field models.

• Korean Journal of Computational Design and Engineering
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• v.1 no.1
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• pp.76-83
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• 1996

A three dimensional FE mesh generation scheme based on mapping approach is proposed in this study. A volume in Eucledian space is represented by composite hyperpatches which are piecewise cubic functions in parameters u, v, w. A key idea in the proposed approach is that I sampled grid data points lying only on the boundary surfaces are needed for the shape representation. Inner points which are necessary to form a hyperpatch are internally generated by Coons patches. This approach is most appropriate for the shapes which are compositions of hexahedronlike shapes and also severely curved.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.425-433
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• 2012

As the demand for electric power increases rapidly and the amount of fossil fuels decreases year by year, making use of renewable resources seem very necessary. However, due to the discontinuous nature of renewable resources and the hierarchical topology of existing grids, power quality and grid stability will deteriorate as more and more distributed generations (DGs) are connected to the grids. It is a good idea to combine local utilization, local consumption, energy storage and DGs to form a grid-friendly micro grid, these micro grids can then assembled into an intelligent power system - the smart Grid. It can optimize power flow and integrate power generation and consumption effectively. Most importantly, the power quality and grid stability can be improved greatly. This paper depicts how the smart grid addresses the current issues of a power system. It also figures out the key technologies and expectations of the smart grid.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.117-118
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• 2013

Recent global warming to the promotion of electric vehicles (EV), plug-in hybrid (PEV), including the next generation of cars and solar power, wind power and other renewable energy, and next-generation power grid (smart grid) are getting attention. In addition, the system utilizes the battery life in the industry and the convenience of a variety of social systems, economics, environmental impact, and the inherent potential to change significantly, and you can not walk into a next-generation industrial strategy and the need increases more and more present, and its early commercialization In order to do this, as well as a key energy source, the battery charger for charging efficiency technologies is essential. In this paper, fast charge multiple battery modules and optional modules that can charge distribution charge will be introduced.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.06a
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• pp.61-70
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• 2000

This paper described the current status of machine tool technology and its future trends with a particular emphasis on high-speed machining. People in machine tool industry have continuously sought to serve fast-changing manufacturing industry with economical machining solutins. At presents, it appears that more productivity gain is demanded to shorten time-to-market and machining requirements become more stringent. In this regard, this paper firstly addressed a high-speed spindle as a key element for the next-generation machine tools. The sequel to it apparently went to high-speed feed axes and final discussion included the problem of how to optimize overall system including servo function. Lastly a brief look to NC technology including machine intelligence was taken.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.89-91
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• 2008

The photovoltaic industry is growing at a tremendous speed. And it can be one of the key factors for success in the photovoltaic business to choose a suitable system, and setting it up right so as to get a maximum efficiency of the site. Therefore, it is regarded to be necessary to research the efficiency of systems to catch maximum photovoltaic energy. In this research, the expected power generation efficiencies are analysed, and compared with each other. This research considered the direct sunlight only, and the angle between the direction of solar panel and sunlight as factors to affect the power generation. Therefore, only rough analyses and estimations are found on 3 systems of fixed system, double-axes tracking system, and horizontal tracking system.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.789-796
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• 2012

Fingerprinting is a widely used positioning technology for received signal strength (RSS) based wireless local area network (WLAN) positioning system. Though spatial RSS variation is the key factor of the positioning technology, temporal RSS variation needs to be considered for more accuracy. To deal with the spatial and temporal RSS characteristics within a unified framework, this paper proposes an extended signal propagation mode (ESPM) and a fingerprint generation method. The proposed spatiotemporal fingerprint generation method consists of two algorithms running in parallel; Kalman filtering at several measurement-sampling locations and Kriging to generate location fingerprints at dense reference locations. The two different algorithms are connected by the extended signal propagation model which describes the spatial and temporal measurement characteristics in one frame. An experiment demonstrates that the proposed method provides an improved positioning accuracy.

• Journal of Power Electronics
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• v.14 no.2
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• pp.324-340
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• 2014

Recent developments in power electronics technology have spurred interest in the use of renewable energy sources as distributed generation (DG) generators. The key component in DG generators is a grid-connected inverter that serves as an effective interface between the renewable energy source and the utility grid. The multifunctional inverter (MFI) is special type of grid-connected inverter that has elicited much attention in recent years. MFIs not only generate power for DGs but also provide increased functionality through improved power quality and voltage and reactive power support; thus, the capability of the auxiliary service for the utility grid is improved. This paper presents a comprehensive review of the various MFI system configurations for single-phase (two-wire) and three-phase (three- or four-wire) systems and control strategies for the compensation of different power quality problems. The advances in practical applications and recent research on MFIs are presented through a review of nearly 200 papers.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.2995-3006
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• 1993

An automatic mesh generation scheme has been developed for finite element analysis with two-dimensional, quadrilateral elements. The basic strategies of the method are to transform the analysis domain into loops with key nodes and the loops are recursively subdivided into subloops with the use of best split lines. Finally by using the basic loop operators, the meshes are completed. In this algorithm an eight-node loop operator is proposed, which is useful in the area where the change of element size is large and the splitting criteria for subdividing the loops have also been modified to the existing algorithms. Lines, arcs, and cubic spline curves are used to define the boundaries of analysis domain. Sample meshes for several geometries are presented to demonstrate the robustness of the algorithm.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.397-399
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• 2000

This paper presents a method for assessing reliability indices of transmission system. Because successful operation of electric power under the deregulated electricity market depends on transmission system reliability management, quantity evaluation of transmission system reliability is very important. The key point idea is based on that the reliability level of transmission system is equal to reliability level difference of between composite power system(HLII) and generation system(HLI). It is sure that risk indices of reliability of composite power system are larger than those of generation system. It is the reason that composite power system includes uncertainties and capacity limit of transmission lines. The characteristics and effectiveness of this methodology are illustrated by the case study using MRBTS.