• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.232-239
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• 2007

There is an increasing concern to interconnect DG(Distributed Generation) units into a distribution system and operate and maintain the system power quality within a proper level to distribution companies, regional electricity utilities and industrial customers. Recently, this situation makes many experts estimate a next generation of distribution system which is composed of some micro-grids. But the proposed micro-grid is only mentioned as a small grid with some DG units, some power quality compensators, communication and control equipments. In this paper, a topology and an operation/control algorithm of the micro-grid which is able to supply the electricity with high reliability and quality, are proposed.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.2
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• pp.182-190
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• 2011

This paper proposes a LVRT (Low Voltage Ride Through) control strategy which should be satisfied by grid-connected wind power system when grid faults occur. The LVRT regulation indicates rules or actions which have to be executed according to the voltage dip ratio and the fault duration. Especially the wind power system has to support the grid with specified reactive current to secure the grid stability when voltage reduction ratio is over 10%. The LVRT regulation in this paper is based on the German Grid Code and full-scale variable speed wind power conversion system is considered for LVRT control strategy. The proposed LVRT control strategy satisfies not only LVRT regulation but also makes power balance between wind turbine and power system through additional DC link voltage regulation algorithms. Because it is impossible to control grid side power when the 3-phase to ground fault occurs, the DC link voltage is controlled by a generator side inverter using the DC link voltage control strategy. Through the simulation and experiment result, the proposed LVRT control strategy is evaluated and its effectiveness is verified.

• Journal of the Korea Society of Computer and Information
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• v.13 no.3
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• pp.65-75
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• 2008

Grid Computing has enabled enormous amount of computational jobs by connecting distributed computing resources. This technology has developed and widely used in various fields. Previous researches usually focused on how to efficiently manage and use the grid resources. However, there was not enough tries to understand and manage information of application softwares in a well-defined structure. Therefore users in application domain need to how about grid deeply to identify and describe the resource requirements matching for each jobs. We introduce a semantic grid management system based on application ontology to overcome this problem. We design and implement the ontology to store various information of the applications. With the ontology, this system can infer the resource requirements from input parameters and input data of the application software and automatically assign appropriate resources by matching the requirement. Also it can transform the information to other forms which grid middlewares can handle. We apply the system to construct an analysis environment of bioinformatics and compare it with other grid systems to explain usefulness of the system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.188-197
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• 2022

We develop a coastal wave forecasting system by using the unstructured grid based on sea wind data of Global Data Assimilation and Prediction System. The verification is performed to examine the performance and accuracy of the wave model. Since the conventional grid has limited wave forecasting on complex coastlines and bathymetry, the unstructured grid system is applied for precise numerical simulation, and applicability for operational support is evaluated. Both grid systems show similar prediction trends in offshore and coastal areas, and the difference in prediction errors according to the grid system is not large. In addition, the applicability of the operational wave forecasting system is confirmed by dramatically reducing the model execution time of the unstructured grid under the same conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.8-13
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• 2007

During the last years, there has been an increased interest in the new energy such as photovoltaic(PV) system from the viewpoint of environmental pollution. In this regard, this paper estimates the power quality of grid-connected PV system. As the maximum power operating point(MPOP) of photovoltaic(PV) power systems alters with changing atmospheric conditions, the efficiency of maximum power point tracking(MPPT) is important in PV power systems. Moreover, grid-connected PV system occurs some problems such as voltage inequality and harmonics. Therefore, this paper presents the results of a grid-connected PV system modeling that contains incremental conductance MPPT controller by PSCAD/EMTDC simulator and investigates the influence that can occur in the grid-connected PV system from aspect of power quality, i.e. voltage drop, total harmonic distortion(TDD) and total demand distortion(TDD). For the case study, the measured data of the PV way in Cheongwadae, Seoul, Korea is used.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_1
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• pp.559-567
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• 2020

As the renewable energy market grows, grid-connected inverters have been improving and expanding in several fields in recent years because energy conversion devices are the main components of solar systems. In this paper, a high-precision new grid-connected three-phase inverter system is proposed. The proposed system consists of a main inverter, a sub inverter and a transformer. The main inverter operates at a low switching frequency and high power and transmits power to the grid. A sub-inverter connected in series with the transmission line through a matching transformer operates at lower power than the main inverter to provide input values to the transformer. The transformer acts as a power supply according to the voltage compensation value. This study is based on the principle of operation of the UPFC(Unified Power Flow Controller) structure used to regulate power flow in AC transmission lines. The grid-connected inverter system proposed in this paper is implemented with high precision and high resolution. The proposed system was verified through its ability to enhance and ensure the safety of the proposed system through simulation and experiment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1337-1346
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• 2014

Power system technologies in the area of smart grid are being converged with communication system technologies or information technologies(IT). This interdisciplinary action affects on two parts vigorously so that IT has become a essential part of power industry. But terminologies of two parts are confused and it is necessary that these are standardized to develop the industry. The writing system of the Open Korean Knowledge Dictionary for standardization of smart grid terminologies which are IEC TC 57 glossary and non-glossary is proposed. The writing system includes the process of collection, writing guideline and standardization of terminologies. Writing results of 90,000 terminologies for electricity, communication and computer fields including smart grid terminologies, which are registered in the Open Korean Knowledge Dictionary, are shown. The system provides the capability of collection and delivery of academic society opinions for the selected and interpreted terminologies through the internet for standardization and industry propagation of smart grid terminologies.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.6
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• pp.1375-1391
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• 2012

Smart grid is a next-generation intelligent power grid that applying ICT to power grid to maximize the energy efficiency ratio. Recently, technologies and standards for smart grid are being developed around the world. Information security which is an essential part of smart grid development has to be managed continuously. Information security management system certification for organizational risk management has been implemented in Korea. Although preparation for information security management system certification which is applicable to smart grid is considered, there are no specific methods. This paper is to propose core and added evaluation criteria for Korean smart grid based on K-ISMS through comparative analysis between ISMS operated in Korea and smart grid information security management system developed in the United States. Added evaluation criteria enable smart grid related business that certified existing ISMS to minimize redundant and unnecessary certification assessment work.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.170-175
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• 1999

Noncontact measuring methodology of 3-dimensional profile using CCD camera are very attractive because of it's high measuring speed and its's high sensitivity. Especially, when projecting a grid pattern over the object the captured image have 3 dimensional information of the object. Projection moire extract 3-D information with another grid pattern in front of CCD camera. However phase measuring profilometry(PMP) obtain similar results without additional grid pattern. In this paper, new method for grid pattern generation system by polygonal mirror and Laser Diode. This system is applied the projection moire and the PMP.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.543-544
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• 2007

Micro-grid consists of micro-sources which adopt environmentally friendly and reliable power sources with independent real and reactive power control capability for providing premium power quality. This paper presents dynamic modeling and the stable operating range of the micro-grid system varying the parameters of the micro-sources. Case study results show the parameters affecting the stability of the micro-grid and the stable operating range of the micro-sources.