• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.5
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• pp.95-108
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• 2011

Smart Grids are intelligent next generating Electric Power System (EPS) that provide environment-friendliness, high-efficiency, and high-trustworthiness by integrating information and communication technology with electric power technology. Smart grids help to supply power more efficiently and safely than past systems by bilaterally exchanging information between the user and power producer. In addition, it alleviates environmental problems by using renewable energy resources. However, smart grids have many cyber security risks because of the bilateral service, the increase of small and medium-sized energy resources, and the installation of multi-sensors or control devices. These cyber risks can cause critical problems within a national grid through even small errors. Therefore, in order to reduce these risks, it is necessary to establish a cyber security strategy and apply it from the developmental stage to the implementation stage. This thesis analyzes and recommends security strategy in order to resolve the security risks. By applying cyber security strategy to a smart grid, it will provide a stepping-stone to creating a safe and dependable smart grid.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2826-2832
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• 2012

A smart grid is an electric-power grid that employs a new information technology.This technology makes it possible to exchange real-time energy information between suppliers and consumers, finally resulting in high energy efficiency. The energy management system in smart grid provides up to date information on electricity consumption as well as dynamic electricity price to consumers of smart grid system. However, the existing energy management systems only focus on pricing system, for example, real-time electricity prices. In this paper, we try to improve the existing energy management system and propose the energy management system that mainly focuses on the efficiency of electricity consumption. In the proposed management system, PMU(Phasor Measurement Units) installed in switchboards gathers electricity data in a real time. We also propose to use data mining method, which is applied to analyzed electricity data for improving energy efficiency. Also, the proposed energy management system is designed to efficiently control the electricity between PMU and management system in case of a shortage of electricity or surplus electricity.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.6
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• pp.590-596
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• 2020

In the island areas where system connection with the commercial power grid is difficult, it is quite important to find a method to efficiently manage energy produced with independent microgrids. In this paper, a prosumer management system for P2P power transaction was realized through the testing the power meter and the response rate of the collected data for the power produced in the small-scale microgrids in which hybrid models of solar power and wind power were implemented. The power network of the microgrid prosumer was composed of mesh structure and the P2P power transaction was tested through the power meter and DC power transmitter in the off-grid sites which were independently constructed in three places. The measurement values of the power meter showed significant results of voltage (average): 380V + 0.9V, current (average): + 0.01A, power: 1000W (-1W) with an error range within ±1%. Stabilization of the server was also confirmed with the response rate of 0.32 sec. for the main screen, 2.61 sec. for the cumulative power generation, and 0.11 sec for the power transaction through the transmission of 50 data in real time. Therefore, the proposed system was validated as a P2P power transaction system that can be used as an independent network without transmitted by Korea Electric Power Corporation (KEPCO).

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.629-630
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• 2015

본 논문에서는 소규모 에너지저장장치를 주파수조정 서비스에 활용하기 위한 클러스터링 기법을 제안하였다. 다양한 클러스터링 기법에서 에너지저장장치에 적합한 기법을 선정하고 적합도 산정방법을 통하여 수명비용을 최소화 하는 방향으로 충 방전하는 기법을 제안하였다. 사례연구에서는 무작위로 에너지저장장치를 운영하는 방법과 제안한 방법의 비교를 통하여 제안한 기법의 효과를 입증하였다.

• Journal of Biomedical Engineering Research
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• v.22 no.2
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• pp.139-144
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• 2001

자기 신경자극기는 신경의학, 재활의학을 포함한 많은 임상의학 분야에서 널리 쓰이고 있다. 자기 신경자극기는 전력소모가 크고 고압 전원이 필요한 이유 때문에 단채널 시스템만이 임상환경이나 연구환경에서 쓰여 왔었다. 본 논문에서는 4채널 자기 신경자극기 개발을 소개하였다. 고압 커패시터를 충전하는데 있어서 단계적 충전방식을 사용하여 작은 크기의 직류 전원장치로 다채널 시스템을 구현하였고, 채널별로 서로 다른 자극 프로토콜로 자극 코일을 구동할 수 있는 다채널 제어시스템을 구성하였다. 개발된 시스템은 신경계통 장애가 있는 환자들의 재활이나 자기적인 침술 등 다양한 기능적 자기 자극에 활용될 수 있을 것으로 기대된다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.8
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• pp.387-394
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• 2005

This paper deals with the grid-interactive small battery energy storage system, which aims at the integration o( power quality improvement and demand side management. The main purpose of the proposed system is to achieve the peak power cutting and to compensate the current harmonics and reactive power at the point of installation on power distribution for residential homes. paper deals with the grid-interactive small battery energy storage system, In this paper, the basic principle and control algorithm is analyzed, theoretically and the design methodology of the system is discussed. To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results for 1 KVA load capacity is presented.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.238-243
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• 2003

The solar cells should be operated at the maximum power point because its output characteristics are greatly fluctuated on the variation of insolation, temperature and load. The output power of solar cell is DC, therefore it is necessary to install an inverter among electric power converts. The inverter have to supply a sinusoidal current and voltage to the load and the interactive utility line. In the paper, the proposes a photovoltaic system designed with a step up chopper and single phase PWM voltage source inverter. Synchronous signal and control signal was processed by microprocessor for stable modulation. The step up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature because solar cell has typical dropping character. The single phase PWM voltage source inverter consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be developed continuously by connecting with the source of electric power, from 10 to $20\%$. The single phase PWM voltage source inverter operates in situation that its output voltage is in same phase with the utility voltage. The inverter supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• Journal of IKEEE
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• v.23 no.1
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• pp.289-294
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• 2019

At present, domestic small islands mainly supply electric power using diesel generators. However, diesel generators can cause instability of the power system due to slow response on power load fluctuation, and cause environmental problems due to the emission of carbon gas by using fossil fuels. In order to overcome this problem, this paper proposes a method to establish an optimal microgrid by introducing solar power, wind power, and energy storage device to Chujado Island, which is supplied with electric power through a diesel generator. The economical optimum capacity of each distributed power source is calculated by using HOMER (Hybrid Optimization Model for Multiple Energy Resources) program and the proposed microgrid is validated by using PSCAD/EMTDC (Power Systems Computer Aided Design/ Electromagnetic Transients including DC) program which can analyze system stability.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.179-184
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• 2019

In many countries, such as developing countries where electricity is scarce, small wind turbines in the form of Off Grid are an effective solution to solve power supply problems. In some countries, the expansion of power systems and the decline of electricity-intensive areas have led to the use of small wind power in urban road lighting, mobile communications base stations, aquaculture and seawater desalination. With this change, the size of the small wind power industry is expected to have greater potential than large-scale wind power. In the case of small wind power generators, the generator is controlled at a variable speed, and the voltage and current generated by the generator have many harmonic components. To solve this problem, the AC to DC converter to be studied in this paper is a three-phase step-up type converter with a single switch. The inductor current is controlled in discontinuous mode, and has a characteristic of having a unit power factor by eliminating the harmonic of the input current. The proposed converter is composed of LCL filter and three phase rectification boost converter at the input stage and a single phase full bridge for grid connection. It is a control system with energy storage system(ESS) that the system stabilization can be pursued against the electric power.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.106-114
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• 2009

This paper addresses unit commitment for microgrid optimization including renewable energy sources, working under deregulated power market. As microgrid supplies both heat and electricity for consumer, operational optimization must be done to meet their demand economically. So renewable energy sources are considered to be negative load, and batteries are used as the load flattening device to raise possibly operational function. In the state of solution, the program is developed to solve out the maximum profit of microgrid using dynamic programming method. Finally, its validity is verified through case study in isolation mode and interconnected mode. The S/W will be used to operate microgrid economically after the market of microgrid is formed.