• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.586-587
• /
• 2011

에디슨이 전기를 발명한 후 지난 100년간 전력산업은 증가하는 전력수요에 대응하기 위해 공급측면에서 발전소 및 송배전 설비 건설을 통해 전력공급 문제를 해결하여 왔다. 이 과정에서 화석연료 사용으로 인한 지구환경오염, 화석연료 고갈에 따른 에너지 가격 급등등으로 신규 대체자원의 개발과 수요측면에서 대응방안 마련이 절실한 상황에 이르렀다. 이러한 문제를 해결하고자 하는 전력산업의 패러다임이 스마트그리드이며, 본 논문에서는 스마트그리드 핵심자원인 수요측자원에 대해 스마트그리드 제주실증단지 전력시장에서의 수요자원 운영방안에 대한 체계를 제시하고자 한다.

• Journal of Power Electronics
• /
• v.16 no.4
• /
• pp.1526-1540
• /
• 2016

This work mainly discusses an accurate and fast islanding detection based on fractional wavelet packet transform (FRWPT)for multibus microgrid systems. The proposed protection scheme uses combined desirable features retrieved from discrete fractional Fourier transform (FRFT) and wavelet packet transform (WPT) techniques, which provides precise time-frequency information on minute perturbation signals introduced in the system. Moreover, this study focuses on the design of decoupling control with a distributed controller based on state feedback for the efficient operation of microgrid systems that are transitioning from the grid-connected mode to the islanded mode. An IEEE 9-bus test system with inverter based distributed generation (DG) units is considered for islanding assessment and smooth operation. Finally, tracking errors are greatly reduced with stability improvement based on the proposed controller. FRWPT based islanding detection is demonstrated via a time domain simulation of the system. Simulated results show an improvement in system stability with the application of the proposed controller and accurate islanding detection based on the FRWPT technique in comparison with the results obtained by applying the wavelet transform (WT) and WPT.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.6
• /
• pp.1100-1104
• /
• 2009

As national power consumption every year increases, the power plant which is in the process of planning tries to establish high-capacity generator. The power system tends to become a large size. With the progress of electronic components, the control systems of the generator have been digitalized and rapid-response control system is possible. However, the minute frequency vibration of grid occurred with the effect of rapid-response control system. To solve these problem, PPS(Power System Stability) has been introduced since 2004, and it has being installed and applied to the thermal and nuclear power plant which are high-capacity, over 800MVA. However the minute frequency vibration is gradually changed to the bigger frequency vibration by fast-action control system, and this regional frequency fluctuation might be diffused wide area. Therefore, it is applied to the hydro generator which is small with fast-action governor system, and it is necessary to control the minute frequency vibration to prevent to diffuse. In this paper, the effect will be proved by establishing PSS on the Hydro-Generator which has both digital excitation and governor system for the first time in Korea.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.63 no.3
• /
• pp.183-188
• /
• 2014

Power conversion systems used in large gas turbine power plant can be divided into two main part. Because of the initial start-up characteristic of the gas turbine combustor, the gas turbine must be accelerated by starting device(LCI : Load Commutated Inverter) up to 10%~20% of rated speed to ignite it. In addition, the ECS(Excitation Control system) is used to control the rotor field current and reactive power in grid-connected synchronous generator. These two large power conversion systems are located in the same space(container) because of coordination control. Recently, many manufactures develop high speed controller based on function block available in the LCI and ECS with the newest power semiconductor. We also developed high speed controller based on function block to be using these two system and it meets the international standard IEC61131 as using real-time OS(VxWorks) and ISaGRAF. In order to install easily these systems at power plant, main controller, special module and IO module are used with high speed communication line other than electric wire line. Before initial product is installed on the site, prototype is produced and tests are conducted for it. The performance results of Integrated controller and application program(SFC, ECS) were described in this paper. The test results will be considered as the important resources for the application in future.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.17 no.1
• /
• pp.55-59
• /
• 2005

The present data concerns the wave height distribution around the Ieodo underwater rocks and it was obtained from a 3D hydraulic model experiment which was performed in 1999 by Konkuk University and Korea Ocean Research and Development Institute. The experiment was separately undertaken for 4 different wave directions (NNW, SE, S, NNW) under which wave heights were measured at every 1m interval within the preset grid area, 16m×18m. It was observed that the wave breaking occurred on the top of the Ieodo model for all wave directions. This data may be effectively used for improving or verifying the performance of numerical wave propagation models in the area with the local breaking wave zones.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.50 no.3
• /
• pp.91-104
• /
• 2008

This study developed the WSM (weighted scenario method)-AHP method that can optimize the weighting value for multi-criteria to make GIS grid-based potential surface. The potential surface has been used to simulate urban expansion using distributed cellular automata model and to generate land-use planning as basic data. This study formulated the WSM-AHP method in mathematically and applied to test region, Suwon city, which located on south area from Seoul. WSM-AHP method generates potential map for each pair of weighting value for all criteria, which one criterion is weighted with high weighting value and the others use low weighting value, considering that the summation for all criteria weighting values should be "1". The potential change rate to the step of weighted scenario for weighting value of criteria is standardized like AHP intensity matrix in this study. From the standard potential change rate, WSM-AHP intensity matrix is completed, and then the optimal weighting value is calculated from the maximum eigenvector of the WSM-AHP matrix, according to the new WSM-AHP method developed in this study. The applied results of new method showed that the optimal weighting value from WSM-AHP is more resonable than the general AHP specialists' evaluation for weighting value. The another new finding of this study is to suggest the deterministic approach to optimize the weighting value for the distributed CA model, which is used to find new city area and to generate rational land-use planning.

• Earthquakes and Structures
• /
• v.9 no.1
• /
• pp.233-256
• /
• 2015

This paper presents an experimental study to assess the effectiveness of using ferrocement to strengthen deficient beam-column joints. Ferrocement is proposed to protect the joint region through replacing concrete cover. Six exterior beam-column joints, including two control specimens and four strengthened specimens, are prepared and tested under constant axial load and quasi-static cyclic loading. Two levels of axial load on column (0.2fc'Ag and 0.4fc'Ag) and two types of skeletal reinforcements in ferrocement (grid reinforcements and diagonal reinforcements) are considered as test variables. Experimental results have indicated that ferrocement as a composite material can enhance the seismic performance of deficient beam-column joints in terms of peak horizontal load, energy dissipation, stiffness and joint shear strength. Shear distortions within the joints are significantly reduced for the strengthened specimens. High axial load (0.4fc'Ag) has a detrimental effect on peak horizontal load for both control and ferrocement-strengthened specimens. Specimens strengthened by ferrocement with two types of skeletal reinforcements perform similarly. Finally, a method is proposed to predict shear strength of beam-column joints strengthened by ferrocement.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.8 no.2
• /
• pp.188-197
• /
• 2016

Offshore substructures have been developed to support structures against complex offshore environments. The load at offshore substructures is dominated by waves, and deformation of waves caused by interactions with the current is an important phenomena. Wave load simulation of fixed offshore substructures in waves with the presence of uniform current was carried out by numerical wave tank technique using the commercial software, FLUENT. The continuity and Navier-Stokes equations were applied as the governing equations for incompressible fluid motion, and numerical wavemaker was employed to reproduce offshore wave environment. Convergence test against grids number was carried out to investigate grid dependency and optimized conditions for numerical wave generation were derived including investigation of the damping effect against length of the damping domain. Numerical simulation of wave and current interactions with fixed offshore substructure was carried out by computational fluid dynamics, and comparison with other experiments and simulations results was conducted.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.8 no.6
• /
• pp.589-601
• /
• 2016

The hybrid grid was adopted and numerical prediction analysis of propeller unsteady bearing force considering free surface was performed for mode and full-scale KCS hull-propeller-rudder system by employing RANS method and VOF model. In order to obtain the propeller velocity under self-propulsion point, firstly, the numerical simulation for self-propulsion test of full-scale ship is carried out. The results show that the scale effect of velocity at self-propulsion point and wake fraction is obvious. Then, the transient two-phase flow calculations are performed for model and full-scale KCS hull-propeller-rudder systems. According to the monitoring data, it is found that the propeller unsteady bearing force is fluctuating periodically over time and full-scale propeller's time-average value is smaller than model-scale's. The frequency spectrum curves are also provided after fast Fourier transform. By analyzing the frequency spectrum data, it is easy to summarize that each component of the propeller bearing force have the same fluctuation frequency and the peak in BFP is maximum. What's more, each component of full-scale bearing force's fluctuation value is bigger than model-scale's except the bending moment coefficient about the Y-axis.

• Journal of Welding and Joining
• /
• v.20 no.2
• /
• pp.90-94
• /
• 2002

FC-BGA has advantages over other interconnection methods including high I/O counts, better electrical performance, high throughput, and low profile. But, FC-BGA has a lot of reliability issues. The 2nd level solder joint reliability of the FC-BGA with large chip on laminate substrate was studied in this paper. The purpose of this study is to discuss solder joint failures of 2nd level thermal cycling test. This work has been done to understand the influence of the structure of package, the properties of underfill, the properties and thickness of bismaleimide tiazine substrate and the temperature range of thermal cycling on 2nd level solder joint reliability. The increase of bismaleimide tiazine substrate thickness applied to low modulus underfill was improve of solder joint reliability. The resistance of solder ball fatigue was increased solder ball size in the solder joints of FC-BGA.