• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1212-1220
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• 2013

In general, for a large power system like DC distribution system for buildings, several power converters are modularized for parallel operation. However, in parallel operation, inconsistency of parameters in each module causes circulating current in the whole system. Circulating current is directly related to loss, and, therefore, it is most important for the safety of the power system to supply the suitable current to each module. This paper proposes a control method to reduce circulating current caused during parallel operation. Accordingly, the validity of parallel operation system including response characteristics and normal state was verified by simulation and experiment result.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.331-337
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• 2015

The power flow analysis of electrified railway is required complicated calculation, because of variable load. Train runs trough rail supplied by electric power therefore, the load value in electrified railway system fluctuates along time. The power flow algorithm in electrified railway system is different from general power system, and the power flow simulation is peformed by the particular simulation software. Powerail is simulation software for analysis of traction power supply system developed by KRRI, in 2008. This consists of load forecasting module, including TPS and time scheduling, and power flow module. This software was verified by measured current under normal feeding condition, however, has not been verified by voltage on the condition of extended feeding. This paper presents the verification of PowerRail based on voltage drop under extended feeding condition. This is performed by comparing simulation result with field test. Field test and simulation is done in commercial railway line.

• Management & Information Systems Review
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• v.2
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• pp.311-334
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• 1998

By decreasing in CPU price and development of computer assembling technology, personal computer fake a good chance to accelerate its supply. Recently, as being introduced new computing technology so called multi media, teaming assist system which is based on single media such as studying book, cassette tape, video tape, or something else is rapidly being replaced by new assist education system based on multi media in which it is operated by the personal computer. In the computer assist education system, there is an evaluation module which appraise learner's study level into the next study strategy. At the view of this point, this part is very important. In this part, there are some factors like Importance, complexity, or difficulty which commonly include fuzzy factors in our surrounding. But until now, we are still out of the level to handle the evaluation module adequately among the some studies. In this study, we would like to suggest a new module that evaluate learning achievement of ICAI which have a variety of fuzzy environment. We combine Independent fuzzy environment like importance, complexity, difficulty into making total evaluation of learner's achievement. By the result, with expressing by linguistic form, this study can provide the theoretical basis in which we will be able to carry out sentence toward evaluation among elementary school.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.3
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• pp.105-112
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• 2008

Solar energy, which is one of renewable energy, would be the most useful resources that can be applied to making energy recycling villages without using fossil energy. This study analyzed energy potential on solar energy considering weather condition in three traditional villages and compared with energy consumption surveyed. A photovoltaic system having 3.0kWp capacity of unit module can generate 182.5%, 96.1% and 170.9% of the yearly mean consumption of electric power in Makhyun, Boojang, and Soso, respectively. A flat-plate solar collector having $2.64m^2$ area of unit module can generate warm water of $142{\ell}$/day, $89{\ell}$/day, and $173{\ell}$/day, respectively in three study villages. In Makhyun and Soso, photovoltaic power and warm water produced by solar energy were sufficient to supply required amount of electric power and warm water. However, both electric power and warm water produced by unit solar module were not sufficient in Boojang area, and so it is required to increase the module area by more than 50%. According to the results of this study, the appropriate combination of energy resources can be applied to rural green-village planning if the characteristic of energy potential for each local area is considered.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.169-172
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• 2005

Tiny camera module using in modern cellular phone requires precise assembly processes. Higher camera resolution and more functions such as zoom lens make the number of camera parts bigger. As market grows rapidly, automatic assembly process is required. However, diverse product line and short life cycle make it difficult. To attack this, a flexible and expandable lens assembly system is proposed. For the fast manufacturing line formation, modular concept is adopted. Also each module is designed to have intelligence to save system formation time. The assembly system is built up on the standard flat-form which provides vibration free base, air and electric supply, controllers, etc. Futhermore, the assembly cell has the capability of handling tiny, thin, or transparent parts which are very difficult to align with vision.

• Journal of the Korea Society of Computer and Information
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• v.24 no.1
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• pp.129-135
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• 2019

This paper is part of research and development for stand-alone solar system without commercial power supply. It implements firmware of controller for operation of stand-alone solar system by applying IoT technology and also develops communication modules that allow multiple solar lamps to send and receive data through wireless network. The controller of the developed stand-alone solar system can effectively charge the power generated by the solar module, taking into account the battery's charge and discharge characteristics. It also has the advantage of attaching wireless communication modules to solar lamp posts to establish wireless communication networks without incurring communication costs. In addition, by establishing IoT gateway middleware platform for each installation site, it forms a foundation to operate multiple solar lamp posts into multiple clusters. And, it is expected that the data collected in each cluster will be used to enable configuration and control of operational information, thereby inducing convenience and efficiency of remote operation and management.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.4
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• pp.278-284
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• 2002

The work presented here provides a control of the supply duct outlet air temperature in PEM (personal environment module) using fuzzy PID controller. In previous work, PID control systems were used, but the result shows that the outlet air temperature and electric heater regulating voltage were oscillated. Fuzzy PID control systems are designed to improve the system response obtained using PID control and implemented experimentally Also, PID controller and fuzzy controller without PID logic are provided to compare the result with that of the fuzzy PID controller. Data obtained shows that the fuzzy PID control system satisfies the design criteria and works proper1y in controlling the supply air temperature. Also it has bettor performance than the previous result obtained using PID control.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.77-85
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• 2018

Renewable energy has been increasingly used and widely acclaimed as one of the solutions to rampant environmental problems. Among numerous kinds of renewable sources, the penetration rate of the PV system is relatively higher than that of others due to ease of installation. However, one disadvantage of the PV system is its dependence on weather condition. The PV system is especially critical when it is used for standalone systems because it cannot operate when the power generated from a PV module is not enough. Therefore, PV systems are often used with an energy storage system, such as batteries, to store backup energy when the weather condition is insufficient to supply power to the system. Blackout time can be reduced by increasing the size of the energy storage system, but it is a trade-off with system cost. In this work, optimal sizing of a standalone PV system is proposed to supply power to the system without blackout. The sizing of PV modules and batteries is performed by a simulation based on actual irradiation data collected during the past five years. The Life cycle costing of each system is evaluated to determine an optimal set of PV modules and batteries among several different combinations. The standalone PV system designed by the proposed method can supply power to the system with no interruption as long as the weather condition is similar to those of the past five years.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.283-287
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• 2005

In this paper, one general approach is proposed for the design of power system that can be applicable for next generation LEO satellite application. The power system consists of solar panels, battery, and power control and distribution unit(PCDU). The PCDU contains solar array modules, battery interface modules, low-voltage power distribution modules, high-voltage distribution modules, heater power distribution modules, on-board computer interface modules, and internal DC/DC converter modules. The PCDU plays roles of protection of battery against overcharge by active control of solar array generated power, distribution of unregulated electrical power via controlled outlets to bus and instrument units, distribution of regulated electrical power to selected bus and instrument units, and provision of status monitoring and telecommand interface allowing the system and ground operate the power system, evaluate its performance and initiate appropriate countermeasures in case of abnormal conditions. We review the functional schemes of the main constitutes of the PCDU such as the battery interface module, the auxiliary supply module, solar array regulators with maximum power point tracking(MPPT) technology, heater power distribution modules, spacecraft unit power distribution modules, and instrument power distribution module.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.195-198
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• 2006

The technology of Solar Power conversion System is defined as a solar cell that changes the sol ar energy into the direct electric energy, power conversion and control technology that convert the dc power into ac power The solar cell module, power conversion, and a control part in component parts consisting a solar power conversion system have influence on its performance. The roles of power conversion and a control part supply the direct current generated by solar cell module for a load with high efficiency as conveniently as possible in this study, the power conversion systen that can generate solar power using DSC module was developed and its characteristics was experimented. The characteristics of the DSC power conversion system including MOSFET and DSP micro processor, high speed devices, was simulated using Psim. According to the results, converter and inverter was manufactured in detail and the performance characteristics were studied.