• Journal of IKEEE
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• v.21 no.1
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• pp.30-38
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• 2017

It is necessary to check the fault of phased array antenna, when the active phased array radar installed in the site is suspected performance degradation due to external impact or long-term operation. However, the near-field test should be performed in anechoic chamber in order to measure the phased array antenna, so that much time and cost must be applied for radar disassembly and transportation, and the operational availability of the radar system is deteriorates. Therefore, we propose a near-field scanner with mobility to check the fault of the phased array antenna at the site, and the effectiveness of the proposed scanner was verified with ${\pm}0.5dB$ magnitude and ${\pm}1.5^{\circ}$ phase in comparison with measured data in anechoic chamber.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.1
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• pp.33-38
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• 1997

Generally, various semiconductor switching devices for power systems are used in battery chargers for electric vehicle. When these used, it takes the problems of transient-current or distortion of waveforms in power systems near by battery chargers because of harmonics and large peak-current, low power factor, etc., caused by the non-linearity of these devices. Recently, power factor control, line current peak-cut, harmonics reduction which was ignored in past is more and more important. In this paper, to solve those problems we will improve the characteristics of voltage rising and propose the high power factor converter circuit for battery chargers. Our proposed system convert commutated voltage to AC resonant wave in high frequency inverter and rectify the link voltages passed high-frequency transformer and transfer the DC voltages. Especially, the effect using these converter system can be improved very large by power factor control and we have to verify the possibilities of improvement through the experiment of Pb-Acid battery application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.74-77
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• 2000

The main objective of this paper is to design and test a new type of polymer ZnO surge arrester for AC power system of railroad vehicles. Metal oxide surge arrester for most electric power system applications, electric train and must not have explosive breakage of the housing to minimize damage to other equipment when subjected to internal high short circuit current. When breakdown of ZnO elements in a surge arrester occurs due to flashover, fault short current flows through the arrester and internal pressure of the arrester rises. The pressure rise can usually be limited by fitting a pressure relief diaphragm and transferring the arc from the inside to the outside of the housing. However, there is possibility of porcelain fragmentation caused by the thermal shock. pressure rise, etc. Non-fragmenting of the housing is the most desired way to prevent damage to other equipment. The pressure change which is occurred by flashover become discharge energy. This discharge energy raises to damage arrester housing and arrester housing is dispersed as small fragment. Therefore, the pressure relief design is requested to obstruct housing dispersion. The main research works are focused on the structure design by finite element method, pressure relief of module, and studies of performance of surge arrester for electric railway vehicle.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.1-7
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• 2016

Bioelectrical impedance (BI) at popliteal regions was measured using a bioelectrical impedance measurement system (BIMS), which employs the multi-frequency and the two-electrode method. Experiments were performed as follows. First, a constant AC current of $800{\mu}A$ was applied to the popliteal regions (left and right) and the BI was measured at eight different frequencies from 10 to 500 kHz. When the applied frequency greater than 50 kHz was applied to human's popliteal regions, the BI was decreased significantly. Logarithmic plot of impedance vs. frequency indicated two different mechanisms in the impedance phenomena before and after 50 kHz. Second, the relationship between resistance and reactance was obtained with respect to the applied frequency using BI (resistance and reactance) acquired from the popliteal regions. The phase angle (PA) was found to be strongly dependent on frequency. At 50 kHz, the PA at the right popliteal region was $7.8^{\circ}$ slightly larger than $7.6^{\circ}$ at the left popliteal region. Third, BI values of extracellular fluid (ECF) and intracellular fluid (ICF) were calculated using BIMS. At 10 kHz, the BI values of ECF at the left and right popliteal regions were $1664.14{\Omega}$ and $1614.08{\Omega}$, respectively. The BI values of ECF and ICF decreased sharply in the frequency range of 10 to 50 kHz, and gradually decreased up to 500 kHz. Logarithmic plot of BI vs. frequency shows that the BI of ICF decreased noticeably at high frequency above 300 kHz because of a large decrease in the capacitance of the cell membrane.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.37-44
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• 2004

This paper represents a new approach for the protective relay of power transmission lines using a Artificial Neural Network(ANN). A different fault m transmission lines need to be detected classified and located accurately and cleared as fast as possible. However, The protection range of the distance relay is always designed on the basis of fixed settings, and unfortunately these approach do not have the ability to adapt dynamically to the system operating condition. ANN is suitable for the adaptive relaying and the detection of complex faults. The backpropagation algerian based multi-layer protection is utilized for the teaming process. It allows to make control to various protection functions. As expected, the simulation result demonstrate that this approach is useful and satisfactory.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.10-22
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• 2009

This paper presents an LED lighting system with an LED color control algorithm that can independently change its color temperature and illuminance. To show the validity of the proposed algorithm, it is proven that its solution always exists. The proposed algorithm was applied to the control of an LED module that is composed of red, green, blue, and white (RGBW) LEDs. Its color temperature variation ranged from 3,500~7,500[$^{\circ}K$], and its illuminance ranges from 500~1,500[lux]. Within these range, the color temperature and illuminance deviations are as low as $\pm0.8$[%] when the junction temperature of LEDs are maintained at 40[$^{\circ}C$]. In the range of 30~70[$^{\circ}C$], the measured illuminance and color temperature deviations are as low as 2.1[%] and 3.6[%], and the compensated ones are as low as 1[%] and 0.49[%], when the desired illuminance and color temperature are 1,000[lux] and 6,500[$^{\circ}K$], respectively.nyang.ac.kr).

• Journal of Power Electronics
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• v.15 no.2
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• pp.455-468
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• 2015

A microgrid (MG) with integrated renewable energy resources can benefit both utility companies and customers. As a result, they are attracting a great deal of attention. The control of a MG is very important for the stable operation of a MG. The droop-control method is popular since it avoids circulating currents among the converters without using any critical communication between them. Traditional droop control methods have the drawback of an inherent trade-off between power sharing and voltage and frequency regulation. An adaptive droop control method is proposed, which can operate in both the island mode and the grid-connected mode. It can also ensure smooth switching between these two modes. Furthermore, the voltage and frequency of a MG can be restored by using the proposed droop controller. Meanwhile, the active power can be dispatched appropriately in both operating modes based on the capacity or running cost of the Distributed Generators (DGs). The global information (such as the average voltage and output active power of the MG and so on) required by the proposed droop control method to restore the voltage and frequency deviations can be acquired distributedly based on the Multi Agent System (MAS). Simulation studies in PSCAD demonstrate the effectiveness of the proposed control method.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.447-447
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• 2010

일찍이 $SiO_2$ (Silicon dioxide) 박막은 다양한 분야에서 유전층, 부식 방지층, passivation층 등의 역할을 해왔다. 그리고 이러한 박막 공정은 대부분 진공의 환경에서 그 공정이 이루어지고 있다. 하지만 이러한 진공 system은 chamber, loadlock 그리고 펌프 등의 다양한 진공장비로 인한 생산 비용 증가, 공정의 복잡성뿐만 아니라 공정의 대면적화에 어려움을 지니고 있다. 그리고 최근 flexible display의 제조 공정에서 polymer 혹은 plastic 기판을 제조 공정에 적용시키기 위해 저온 공정이 필수적으로 요구 되고 있다. 이러한 기술적 한계를 뛰어 넘기 위해 최근 많은 연구가들은 atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD)에 대해 지속적으로 다양한 연구를 하고 있다. 본 연구에서는 remote-type의 modified pin-to-plate dielectric barrier discharge (DBD) 시스템을 이용한 $SiO_2$ 무기 박막 증착에 관해 연구하였다. $O_2$/He/Ar의 gas와 5 kV AC power (30 kHz)의 전원장치를 통해 고밀도 대기압 플라즈마를 발생시켰고, silicon precursor로는 hexamethyldisilazane (HMSD)를 사용하였다. 먼저 HMDS와 $O_2$ gas의 flow rate 변화에 따른 증착률을 조사하였고 그 다음으로 박막의 조성 및 표면 특성을 조사하였다. HMDS의 유량이 100 ~ 300 sccm으로 증가함에 따라 증착속도는 증가했다. 하지만 FT-IR을 통해 HMDS의 유량이 증가하면 반응에 참여할 산소 분자의 부족으로 인해 $-(CH_3)_X$의 peak intensity가 증가하고, -OH의 peak intensity가 점차 감소함을 관찰 할 수 있었다. 또한 증착된 박막의 표면에 particle과 불균일한 surface morphology 등을 SEM image를 통해 관찰 하였다. 산소 유량이 탄소와 관련된 많은 불순물들의 제거에 도움이 됨에도 불구하고 14 slm 이상의 산소가 반응기 내로 주입되게 되면 대기압 플라즈마의 discharge가 불안정하게 되어 공정효율을 저하시키는 요소가 되었다. 결과적으로 HMDS (150 sccm)/$O_2$ (14 slm)/He (5 slm)/Ar (3 slm)의 조건에서 약 42.7 nm/min 증착률을 가지며, 불순물이 적고 surface morphology가 깨끗한 $SiO_2$ 박막을 증착할 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4083-4094
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• 2011

The Electric Power Steering (EPS) has been applied to the vehicles due to its better fuel efficiency, better steering feel, and the compact volume compared to the hydraulic power steering. The brushed PM (Permanent Magnet) DC motors had been adopted in most of the EPS systems until several years ago due to its easy control and a simple hardware configuration of the power converter, but nowadays the BLAC (Brushless AC) motor is becoming more popular for the EPS system because of its high efficiency and long lifetime. This paper reviews the configuration of the EPS system and the BLAC motor and drive technologies based on the papers published recently. The torque ripple reduction for steering feel and the fault detection algorithms for safety are also reviewed.

• Journal of Advanced Navigation Technology
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• v.22 no.4
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• pp.325-335
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• 2018

Limited access to state information in the design of a feedback controller has brought out a significant amount of research on the design of an output feedback controller. Despite its long endeavor to find an optimal one, it is still an open problem. Thus, we focus on the comparison of existing states of arts in the design of a static output feedback controller in terms of stability and complexity so as to find further research direction in this field. To this end, we present eight design methods in a unified presentation. We also provide the complete description of algorithms which can be applicable to any system configuration. Stability performance and complexity in terms of processing time are evaluated through numerical simulations. Simulation results show that the algebraic controller (AC) algorithm [20] has the smallest complexity while the scaling linear matrix inequality (SLMI) algorithm [18] seems to achieve the best stability in most cases with much higher complexity.