• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.7
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• pp.1159-1164
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• 2006

Broadband antennas have late-time ringing by multi-reflections between feed points and 0pen ends of the antennas, which indicates the narrowband nature of the antenna. The resistive loading has been used to reduce the late time ringing that is important for ground penetrating radar and resonance detection systems in order to prevent masking of target. In this paper, we design an ultra wide band antenna with resistive loading technique to reduce the internal reflections within the antenna.. The designed antenna is implemented and tested to show inIproved characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.270-277
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• 2013

In this paper, we propose a wideband ridge SIW(Ridge Substrate Integrated Waveguide)-to-SIW(Substrate Integrated Waveguide) transition. The proposed transition structure is designed to acquire a wide bandwidth by inserting through via holes at the regular interval for an impedance matching and an E-field mode matching method. The measurement results show a fractional bandwidth is 29.1 % at 20 dB return loss from the center frequency(11 GHz). The maximum insertion loss is 0.49 dB from 9.21 GHz to 12.41 GHz.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1023-1030
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• 2007

This paper presents a new and efficient approach for solving the economic dispatch (ED) problems with nonconvex cost functions using particle swarm optimization (PSO). Although the PSO is easy to implement and has been empirically shown to perform well on many optimization problems, it may easily get trapped in a local optimum when solving problems with multiple local optima and heavily constrained. This paper proposes an improved PSO, which combines the conventional PSO with chaotic sequences (CPSO). The chaotic sequences combined with the linearly decreasing inertia weights in PSO are devised to improve the global searching capability and escaping from local minimum. To verify the feasibility of the proposed method, numerical studies have been performed for two different nonconvex ED test systems and its results are compared with those of previous works. The proposed CPSO algorithm outperforms other state-of-the-art algorithms in solving ED problems, which consider valve-point and multi-fuels with valve-point effects.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1019-1025
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• 2004

The X-band 10${\times}$10 waveguide slot array antenna for SAR is designed, fabricated and measured. The array antenna is designed using the equivalent circuit model based on the field distribution of the dominant mode, TE$\sub$10/, and EM simulation. The method to decide optimum angle of the centered inclined slot(coupling slot) and the optimum of offset of the longitudinal slot(radiating slot) is provided. The designed antenna structure is EM simulated and fabricated. The measured return loss bandwidth is 180 MHz at 9.15 GHz , the side lobe level is below -25 dB, HPBW is about 9$^{\circ}$, and the gain is 25.5 dB. These results are similar to the simulation data.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.10
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• pp.480-488
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• 2001

This paper presents a technique that can obtain an optimal solution for the Security-Constrained Economic Dispatch (SCED) problems using the Interior Point Method (IPM) while taking into account of the power flow constraints. The SCED equations are formulated by using only the real power flow equations from the optimal power flow. Then an algorithm is presented that can linearize the SCED equations based on the relationships among generation real power outputs, loads, and transmission losses to obtain the optimal solutions by applying the linear programming (LP) technique. The objective function of the proposed linearization algorithm are formulated based on the fuel cost functions of the power plants. The power balance equations utilize the Incremental Transmission Loss Factor (ITLF) corresponding to the incremental generation outputs and the line constraints equations are linearized based on the Generalized Generation Distribution Factor (GGDF). Finally, the application of the Primal Interior Point Method (PIPM) for solving the optimization problem based on the proposed linearized objective function is presented. The results are compared with the Simplex Method and the promising results ard obtained.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1131-1140
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• 2004

In this paper, we proposed a flate-plate antenna employing semi-annular slots for satellite broadcast reception. The radiating element of the antenna is dual annular slots fed by a strip dipole, which have a wider bandwidth than the rectangular slot. A $16{\times}16$ array antenna is designed using stripline T-junction power dividers. Measurements of the fabricated antenna show a gain of 28.0$\~$29.5 dB in 11.7$\~$12.8 GHz frequency range.

• Journal of IKEEE
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• v.10 no.1 s.18
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• pp.1-9
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• 2006

This paper presents the characteristics of a half-bowtie-shaped meander-type antenna for the 5-GHz band. Its design is based on a modified meander line width and bowtie shape with coaxial feeding. Its maximum measured impedance bandwidth (-10 dB below) is approximately 1.055 GHz (5.01-6.065 GHz) or 19.05%. Radiation patterns at different frequencies are presented. The measured gain was 2.26-8.86 dBi.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.27-33
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• 2005

Constant load model is generally used for an electric train to perform the static analysis of AT feeding systems. In this model, the train will be considered as a constant load model when it drives or as a constant source model when it applies regenerative brake. However there must be some voltage constraints on the catenary in actual operations. These constraints are established for the reason of protecting the feeding facilities from excessive rise of regenerative braking voltage or guaranteeing the minimum traction power of train. In normal operating situation, the pantagraph voltage of the train should be maintained within these limits. Keeping these facts in minds, we suggest new methods of analyzing AT feeding systems using the constant power models with the conditions of voltage constraints. The simulation results from a sample system using the proposed method illustrate both the states of system variables and the supply-demand relation of power among the trains and the systems very clearly, so it is believed that the proposed method yields more accurate results than conventional methods do. The proposed methods are believed to contribute to the assessment of TCR-TSC for compensating reactive powers too.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1579-1580
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• 2015

철도차량의 동력원은 화석연료를 사용하던 디젤차량에서 최근 고속전철 및 도시철도차량, 경량전철 등 전기를 주 동력원으로 사용되고 있다. 철도차량에 전기를 공급하는 시스템은 일반적으로 개활지 등 지상구간에 적용되고 있는 가공전차선 방식과 지하구간, 터널 등에 적용되고 있는 강체가선방식 그리고 경량전철 등에 채용되고 있는 제 3궤조방식이 있다. 최근에는 일반적으로 지하구간의 가선시스템에 적용되던 T-Bar방식의 강체가선 방식에서 탈피하여 고속주행이 가능한 R-Bar방식의 강체가선 방식에 대한 연구가 많이 이루어지고 있다. 최근까지 지하구간의 터널구조에서 강체전차선로를 급전시스템으로 채택할 경우 열차의 최고속도는 국내의 경우 90km/h, 국외의 경우 160km/h를 넘지 못하는 실정이었다. 그러나 이를 극복한 제품이 개발되어 열차운행 최고속도를 200~250km/h까지 향상시킬 수 있게 되었다. 본 논문에서는 최근 설계속도 250km/h 급 R-bar방식 강체전차선로 인터페이스를 위한 이선현상 모의 시뮬레이터 개념 설계에 관한 연구를 수행하였다. 이를 위해 집전성능과 관계가 있는 전기철도차량 이선현상 요인 및 영향 분석하였으며 강체전차선로 운행에 따른 이선 등으로 인한 영향을 고찰하기 위해 이선 현상 모의 시뮬레이터 개념 설계에 대한 연구를 수행하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.149-155
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• 2004

This paper presents how to find proper operating points of FACTS devices to enhance the steady-state security level considering line contigency analysis. Three generic types of FACTS devices such as series controllers, shunt controllers, and series-shunt controllers are introduced and applied to moximize a security margin and to minimize security indices. Security indices related to line flows and bus voltages are utilized and minimized iteratively in this paper. Contingency analysis is performed to detect the most severe single line fault. In various load conditions, FACTS devices are tested to establish appropriate preventive or corrective action without generation re-dispatching or load shedding. The FACTS operation scheme is verified on the IEEE 57-bus system in a line-faulted contingency.