• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.297-304
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• 2022

The models used for ionosphere error correction in positioning using Global Navigation Satellite System (GNSS) are representatively Klobuchar model and NeQuick model. Although these models can correct the ionosphere error in real time, the disadvantage is that the accuracy is only 50-60%. In this study, a method for polynomial modeling of Global Ionosphere Map (GIM) which provides Vertical Total Electron Content (VTEC) in grid type was studied. In consideration of Ionosphere Pierce Points (IPP) of satellites with a receivable elevation angle of 15 degrees or higher on the Korean Peninsula, the target area for model generation and provision was selected, and the VTEC at 88 GIM grid points was modeled as a polynomial. The developed VTEC polynomial model shows a data reduction rate of 72.7% compared to GIM regardless of the number of visible satellites, and a data reduction rate of more than 90% compared to the Slant Total Electron Content (STEC) polynomial model when there are more than 10 visible satellites. This VTEC polynomial model has a maximum absolute error of 2.4 Total Electron Content Unit (TECU) and a maximum relative error of 9.9% with the actual GIM. Therefore, it is expected that the amount of data can be drastically reduced by providing the predicted GIM or real-time grid type VTEC model as the parameters of the polynomial model.

• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.29-33
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• 2010

For last 10 years, there are big progress and many efforts in the development of HTS power equipments by some country including South Korea. Especially HTS cable system is the strongest candidate among them from the viewpoint of applying to real grid, because of the feature of it, compact and large capacity. In South Korea, transmission level 154kV, the world top voltage class, HTS cable system was installed and has been tested in KEPCO Gochang Underground Cable Test Field since the early of 2010 in order to meet test requirements made by KEPCO, the only grid company in South Korea. The type test of it will be completed by October 2010 and subsequently long-term load cycle test will be performed during 6 months. Also in the near future, KEPCO has a plan to demonstrate transmission level HTS cable system in real grid, in order to meet practical requirements and confirm the feasibility of it. This paper says the test plan of transmission level 154kV HTS cable system and the way how to test it.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3327-3334
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• 2021

Present electric grids are advanced to integrate smart grids, distributed resources, high-speed sensing and control, and other advanced metering technologies. Cybersecurity is one of the challenges of the smart grid and nuclear plant digital system. It affects the advanced metering infrastructure (AMI), for grid data communication and controls the information in real-time. The research article is emphasized solving the nuclear and smart grid hardware security issues with the integration of field programmable gate array (FPGA), and implementing the latest Time Authenticated Cryptographic Identity Transmission (TACIT) cryptographic algorithm in the chip. The cryptographic-based encryption and decryption approach can be used for a smart grid distribution system embedding with FPGA hardware. The chip design is carried in Xilinx ISE 14.7 and synthesized on Virtex-5 FPGA hardware. The state of the art of work is that the algorithm is implemented on FPGA hardware that provides the scalable design with different key sizes, and its integration enhances the grid hardware security and switching. It has been reported by similar state-of-the-art approaches, that the algorithm was limited in software, not implemented in a hardware chip. The main finding of the research work is that the design predicts the utilization of hardware parameters such as slices, LUTs, flip-flops, memory, input/output blocks, and timing information for Virtex-5 FPGA synthesis before the chip fabrication. The information is extracted for 8-bit to 128-bit key and grid data with initial parameters. TACIT security chip supports 400 MHz frequency for 128-bit key. The research work is an effort to provide the solution for the industries working towards embedded hardware security for the smart grid, power plants, and nuclear applications.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.7
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• pp.9-19
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• 2010

Fuel cell (FC) distributed generation (DG) is gradually becoming more attractive to mainstream electricity users as capacity improves and costs decrease. New technologies including inverters are becoming available to provide a uniform standard interconnection of DGs with an electric power system. Some of the operating conflicts and the effect of DG on power quality are addressed and investigated through simulations on a real distribution network with an FC power plant. The results of these simulations have proved load tracking capability following the real and reactive power change of the load and have shown the flow of overcurrent from an FC power plant during the ground fault of a distribution line.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.721-725
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• 2004

Multiple-count problem is occurred when rectangle objects span across several buckets. The Cumulative Density (CD) histogram is a technique which solves multiple-count problem by keeping four sub-histograms corresponding to the four points of rectangle. Although it provides exact results with constant response time, there is still a considerable issue. Since it is based on a query window which aligns with a given grid, a number of errors may be occurred when it is applied to real applications. In this paper, we proposed selectivity estimation techniques using the generalized cumulative density histogram based on two probabilistic models: (1) probabilistic model which considers the query window area ratio, (2) probabilistic model which considers intersection area between a given grid and objects. In order to evaluate the proposed methods, we experimented with real dataset and experimental results showed that the proposed technique was superior to the existing selectivity estimation techniques. The proposed techniques can be used to accurately quantify the selectivity of the spatial range query on rectangle objects.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.268-270
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• 2005

A tendency to erect more wind turbines can be observed in order to reduce the environmental consequences of electric power generation. As a result of this, in the near future, wind turbines may start to influence the behavior of electric power systems by interacting with conventional generation and loads. Therefore, wind turbine models that can be integrated into power system simulation software are needed. In this paper, a model that can be used to represent all types of variable speed wind turbines in power system simulations is presented. Wind turbine characteristic equation of a wind turbine is implemented in the RTDS, and the real data of weather conditions are interfaced to the RTDS for the purpose of real time simulation of grid-connection wind power system. The outcomes of the simulation demonstrate the effectiveness of the proposed simulation scheme in this paper. The results show that the cost effective verifying for the efficiency and stability of WPGS.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.248-249
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• 2010

This paper describes development of hardware simulator for the PMSG(Permanent Magnet Synchronous Generator) wind power system, which was designed using real wind data. The simulator consists of a realistic wind turbine model using anemometer, vector drive, induction motor. The turbine simulator generates torque and speed signals for a specific wind turbine with respect to given wind speed. This torque and speed signals are scaled down to fit the input of 3kW PMSG. The PMSG-side converter operates to track the maximum power point and the grid-side inverter controls the active and reactive power supplied to the grid. The operational feasibility was first verified by computer simulations with PSCAD/EMTDC. The feasibility of real system implementation was confirmed through experimental works with a hardware set-up.

• International Journal of Advanced Culture Technology
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• v.6 no.4
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• pp.284-291
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• 2018

As environmental pollution has become worse green technologies to replace or reduce consumption of fossil fuel get spotlight from government, industry and academia globally. It is reported that 40% of carbon dioxide emission is caused by electricity power generation. And 37% of end user electricity power is used by residential costumer in US. Smart Grid is considered as one of promising technology to alleviate severe environmental problem. In residential environment, Home Energy Management System (HEMS) can play a key role for green smart home. The HEMS can give several benefits like aslowering electric utility bill, improvement of efficiency of electric power consumption and integration of generator using renewable energy resources. However just limited functions of HEMS can be used for residential customer in real life because of lack of smart function in home appliances and optimal managing software for HEMS. This study provides comprehensive analysis for Home Energy Management System for residential customer. Simple HEMS system with real products on the market are explained and limitation of current HEMS are also discussed.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.2
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• pp.415-423
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• 2016

Smart grid systems can be real-time information exchange between suppliers and consumers, and provides a lot of convenience. However, the risk to the user's personal information exposure is ever-present. Depending on the characteristic of the smart grid environment, there is a threat of the disclosure of personal information based on the personal information life-cycle, and can also be exposed a variety of information based on energy consumption pattern analysis. In this paper, we analyze the existing privacy act in the smart grid and propose improvements for the existing directive.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.1074-1079
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• 2004

So far, many sensors such as a structured grid pattern generator, a laser, and CCD camera to obtain 3D information have been used, but most of algorithms for a calibration are inefficient since a huge memory and experiment time are required. In this paper, the calibration algorithm of a structured grid pattern based on triangulation method is introduced to calculate 3D information in the real world. The beams generated from structured grid pattern generator established horizontally with the CCD camera are projected on the calibration plat. A CCD camera measures the intersection plane of a projected beam and an object plane. The 3D information is calculated using measured and calibration datum. This proposed method in this paper has advantages such as a memory saving and an efficient experimental time since the 3D information is obtained simply the triangulation method.