• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.135-142
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• 2008

Hydraulic power steering system has been adopted in seniority passenger and commercial vehicle system for an easy maneuverability and a smoother ride. In this study, hydraulic power steering system analysis model which includes hydraulics and mechanical sub-systems was developed using commercial software, AMESim in order to predict characteristics for various steering components. Each component which constructs system was modeled and verified by experimentally obtained characteristics curves of each components. The parameter sensitivity analysis such as valve opening area, torsional stiffness of torsion bar for system design are carried out by the analysis and experimental method. The predicted results by the development model were a good agreement with experimentally obtained results. The sensitivity investigation results rotary torque when changing an input shaft edge width, was most sensitive, to change in angle and slot width and supply flow of input shaft edge is not a lot sensitively.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.484-496
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• 2009

The strengthened regulations for atmospheric emissions from ships like MARPOL Annex VI have caused a necessity of new, alternative power system in ships for the low pollutant emissions and the high energy efficiency. This paper attempts to investigate the configuration of SOFC/GT hybrid power system for LNG tanker taking into account the safety and to analyze the influence of design parameters on the system performance. The simulation results provide the basic data for the design and efficiency improvement of SOFC/GT hybrid system and indicate the guidelines for the safe system operation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.232-241
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• 2010

This paper describes the development of robust contingency analysis program for Korean Energy Management System. The important function of contingency analysis is to determine the bus/branch model for contingency, and to calculate the state of the power network based on the network model and topology output. In the proposed method, the bus/branch models for contingencies are determined exactly using a fast linked-list method based on the application common model database. To calculate the state of the power system included contingency, the full-decoupled powerflow approach, the partial powerflow method for contingencies and the proposed contingency screening algorithm are also used to contingency analysis. To verify the performance of the developed processor, we performed a file-based test using several structured input data and online test using the database which resides on memory. The results of these comprehensive tests showed that the developed processors can accurately calculate the power system contingency state from online data and can be applied to Korea Power Exchange system.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1501-1510
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• 2014

Low voltage direct current (LVDC) distribution system is a suitable techno-economic candidate which can create an innovative solution for distribution network development with respect to rural electrification. This research focuses on the use of LVDC distribution system to replace some of KEPCO's existing traditional medium voltage alternating current (MVAC) distribution network for rural electrification in South Korea. Considering the technical and economic risks and benefits involved in such project, a comparative techno-economic analysis on the LVDC and the MVAC distribution networks is conducted using economic assessment method such as the net present value (NPV) on a discounted cash flow (DCF) basis as well as the sensitivity analysis technique. Each would play a role in an economic performance indicator and a measure of uncertainty and risk involved in the project. In this work, a simulation model and a computational tool are concurrently developed and employed to aid the techno-economic analysis, evaluation, and estimation of the various systems efficiency and/or performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.148-155
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• 2006

Portable embedded systems which mainly handle multimedia applications involve the problem that frequent accesses to fetch data from memory make running time increased. To cope with the problem, embedded processors have adopted data prefetching schemes. From a power point of view, which is a main performance indicator of embedded systems, this paper analyzed to investigate how data prefetching schemes influence on system's performance. To solve the problem, we proposed a power-consumption analysis model of a memory system with data prefetching scheme and measured the power dissipated during running application programs. As a result data prefetching schemes have application program's running time reduced but have system's power increased. Also we proposed a performance analysis model considering execution time and power consumption for embedded system with data prefetching schemes.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.275-286
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• 2019

This paper presents real-time Direct Current (DC) network analysis applications for operation of DC distribution system or DC microgrid. These applications are installed on central Energy Management System (EMS) and provide solutions of DC network operation. To analysis DC distribution network, this paper proposes composition and sequence of applications. Algorithm of applications is presented in this paper. Demonstration tests are performed on DC distribution site in Gochang Power Testing Center of Korea Electric Power Corporation (KEPCO). To verify the performance, developed DC applications installed on EMS. Scenarios for demonstration test of voltage control are presented. Finally, measured data, application output data and simulation data (by PSCAD/EMTDC) are compared and analyze accuracy of applications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1349-1353
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• 2013

The optimal analysis has objective functions, equality constraint functions and inequality functions. Objective functions may be used with inequality function, because occasionally variables are moved to non-analytic condition with calculating objective functions. But inequality constraint functions are very complicated problem in a optimal analysis. this paper suggest a method to solve inequality constraint functions.

• Journal of Power Electronics
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• v.11 no.5
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• pp.734-742
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• 2011

In this paper a robust method is presented for the combined design of STATCOM and Power System Stabilizer (PSS) controllers in order to enhance the damping of the low frequency oscillations in power systems. The combined design problems among PSS and STATCOM internal ac and dc voltage controllers has been taken into consideration. The equations that describe the proposed system have been linearized and a Fuzzy Logic Controller (FLC) has been designed for the PSS. Then, the Particle Swarm Optimization technique (PSO) which has a strong ability to find the most optimistic results is employed to search for the optimal STATCOM controller parameters. The proposed controllers are evaluated on a single machine infinite bus power system with the STATCOM installed in the midpoint of the transmission line. The results analysis reveals that the combined design has an excellent capability in damping a power system's low frequency oscillations, and that it greatly enhances the dynamic stability of power systems. Moreover, a system performance analysis under different operating conditions and some performance indices studies show the effectiveness of the combined design.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.702-705
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• 2005

The wind power is known as the most promising future energy source to obtain the electricity. Induction generator is a simple energy conversion wit in the wind power generation system but it consumes the reactive power from the interconnected power system. Switched capacitor banks are normally used to compensate the reactive power, which bring about the transient overvoltage. This paper proposes a method for compensating the reactive power with STATCOM. A detail simulation model for analyzing the interaction between the wind power system and the commercial power system was developed using EMTDC software. The developed simulation model can be effectively utilized to plan the reactive power compensation for newly designed wind power system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.6
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• pp.309-315
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• 2004

The wind power is known as the most promising future energy source to obtain the electricity Induction generator is a simple energy conversion unit in the wind power generation system but it consumes the reactive power from the interconnected power system. Switched capacitor banks are normally used to compensate the reactive power, which bring about the transient overvoltage. This paper proposes a method for compensating the reactive power with STATCOM. A detail simulation model for analyzing the interaction between the wind power system and the commercial power system was developed using EMTDC software. The developed simulation model can be effectively utilized to plan the reactive power compensation for newly designed wind power system.