• 전력전자학회논문지
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• 제20권1호
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• pp.1-10
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• 2015

This paper proposes a control algorithm for permanent magnet synchronous generators with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage off-shore wind power system under unbalanced grid conditions. Specifically, the proposed control algorithm compensates for unbalanced grid voltage at the PCC (Point of Common Coupling) in a collector bus of an off-shore wind power system. This control algorithm has been formulated based on symmetrical components in positive and negative synchronous rotating reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power is described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of AC input current is injected into the PCC in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm enables the provision of balanced voltage at the PCC resulting in the high quality generated power from off-shore wind power systems under unbalanced network conditions.

• ETRI Journal
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• 제27권1호
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• pp.75-80
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• 2005

This paper addresses a fully-integrated low phase noise X-band oscillator fabricated using a carbon-doped InGaP heterojunction bipolar transistor (HBT) GaAs process with a cutoff frequency of 53.2 GHz and maximum oscillation frequency of 70 GHz. The oscillator circuit consists of a negative resistance generating circuit with a base inductor, a resonating emitter circuit with a microstrip line, and a buffering resistive collector circuit with a tuning diode. The oscillator exhibits 4.33 dBm output power and achieves -127.8 dBc/Hz phase noise at 100 kHz away from a 10.39 GHz oscillating frequency, which benchmarks the lowest reported phase noise achieved for a monolithic X-band oscillator. The oscillator draws a 36 mA current from a 6.19 V supply with 47.1 MHz of frequency tuning range using a 4 V change. It occupies a $0.8mm{\times}0.8mm$ die area.

• 전기학회논문지
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• 제67권3호
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• pp.454-459
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• 2018

The BIPV system must be designed to reflect the architectural and electrical characteristics simultaneously because it replaces the role of the exterior material of the building, which makes it difficult to design the BIPV. The thin film type BIPV module has an electrical characteristic that the open voltage is higher and the short circuit current is lower than that of the crystalline type BIPV module. However, there are many differences in the design of the array, the collector distribution board, and the inverter in the system configuration since the crystal type BIPV module has the opposite feature. In this study, a crystalline BIPV module and a thinfilm BIPV module were applied to actual buildings. As a result, the elements to be considered in designing BIPV system were derived, and the architectural and electrical characteristics were mutually analyzed.

• 한국전기전자재료학회논문지
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• 제18권8호
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• pp.702-707
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• 2005

Spinel $LiMn_2O_4$ has become appealing because manganese is inexpensive and environmentally benign. In general, cathodes for lithium ion batteries include carbon as a conductive agent that provides electron transfer between the active material and the current collector. In this work, we selected Acetylene Black and Super P Black as conductive agents, and then carried out their comparative investigation for the performances of the $Li/LiMn_2O_4$ cells using different conductive agents with different particle size. In addition, their electrochemical impedance characteristic of $Li/Mn_2O_4$ cells using different conductive agents is effectively identified through a.c. impedance technique. As a consequence, $Li/LiMn_2O_4$ cells with Super P Black show better electrochemical performances ascribed to the significant contribution of feasible ionic conduction due to larger particle size than those with Acetylene Black.

• 한국산업융합학회 논문집
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• 제23권2_2호
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• pp.219-224
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• 2020

This study is based on the principle of solar power system and fire breakout. The result of the survey indicates that a solar power system is vulnerable to fire due to lack of maintenance after the installation. Currently the national fire safety agency does not have standards and legal provisions for the installation and maintenance of solar power facilities. Therefore, it increases the risk of fire breakouts as well as possibility of electric shock for the firefighters during fire fighting. This results possible damages to the human and equipments. In this study is proposing an automatic fire extinguishing system to reduce the power generation of solar panels during fire breakouts. Also, propose an over load current alarm system and fire prevention measures for fire fighters. The results of this study will be used as basic data for further fire testing of solar power systems.

• 한국분말재료학회지
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• 제12권6호
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• pp.413-421
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• 2005

Copper is able to work as a current collector under wide range of hydrocarbon fuels without coking in Solid oxide fuel cells (SOFCs). The application of copper in SOFC is limited due to its low melting point, which result in coarsening the copper particle. This work focuses on the sintering of copper powder with ceria coating layer. Ceria-coated powder was prepared by thermal decomposition of urea in $Ce(NO_3)_3\cdot6H_2O$ solution, which containing CuO core particles. The ceria-coated powder was characterized by XRD, ICP, and SEM. The thermal stability of the ceria-coated copper in fuel atmosphere $(H_2)$ was observed by SEM. It was found that the ceria coating layer could effectively hinder the grain growth of the copper particles.

• Environmental Engineering Research
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• 제25권2호
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• pp.238-242
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• 2020

Sediment microbial fuel cells (SMFCs) illustrated great potential for powering environmental sensors and bioremediation of sediments. In the present study, array anodes for SMFCs were fabricated with graphite rods as anode material and stainless steel plate as electric current collector to make it inconvenient to in situ settle down and not feasible for large-scale application. The results demonstrated that maximum power of 89.4 ㎼ was obtained from three graphite rods, twice of 43.3 ㎼ for two graphite rods. Electrochemical impedance spectroscopy revealed that three graphite rods resulted in anodic resistance of 61.2 Ω, relative to 76.0 Ω of two graphite rods. It was probably caused by the parallel connection of the graphite rods, as well as more biomass which could reduce the charge transfer resistance of the biofilm anode. The presently designed array configuration possesses the advantages of easy to enlarge the surface area, decrease in anodic resistance because of the parallel connection of each graphite rod, and convenience to berry into sediment by gravity. Therefore, the as prepared array node would be an effective method to fabricate large-scale SMFC and make it easy to in situ applicate in natural sediments.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.25-28
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• 1998

Lithiated cobalt and nickel oxides are becoming very attractive as active cathode materials for secondary lithium ion secondary battery. $LiCoO_2$ is easily synthesized from lithium cobalt salts, but has a relatively high oxidizing potential on charge. LiNiOz is synthesized by a more complex procedure and its nonstoichiometry significantly degraded the charge-discharge characteristics. But $LiNiO_2$ has a lower charge potential which increases the system stability. Lithiated cobalt and nickel oxides are iso-structure which make the preparation of solid solutions of $LiNi_{1-x}Co_xO_2$ for O$LiCoO_2 and LiNiO_2$ electrode. The aim of the presentb paper is to study the electrochemical behaviour, as weU as the possibilities for practical application of layered Iithiated nickel oxide stabilized by $Co^{3+}$ substitution as active cathode materials in lithium ion secondary battery.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.236-238
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• 1997

A cellular power amplifier using an APCVD(Atmospheric Pressure Chemical Vapor Deposition)-grown SiGe base HBT of ETRI has been designed with a linear simulation CAD. The Si/SiGe HBT with an emitter area of 2$\times$8${\mu}{\textrm}{m}$$^2$typically has a cutoff frequency(f$_{T}$) of 7.0 GHz and a maximum oscillation frequency(f$_{max}$) of 16.1 GHz with a pad de-embedding A packaged power Si/SiGe HBT with an emitter area of 2$\times$8$\times$80${\mu}{\textrm}{m}$$^2$typically shows a f$_{T}$ of 4.7 GHz and a f$_{max}$ of 7.1 GHz at a collector current (Ic) of 115 mA. The power amplifier exhibits a Forward transmission coefficient(S21) of 13.5 dB, an input and an output reflection coefficients of -42 dB and -45 dB respectively. Up to now the III-V compound semiconductor devices hale dominated microwave applications, however a rapid progress in Si-based technology make the advent of the Si/SiGe HBT which is promising in low to even higher microwave range because of lower cost and relatively higher reproducibility of a Si-based process.ess.ess.

• 한국재료학회지
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• 제22권1호
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• pp.1-7
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• 2012

Thin film electrode consisting purely of porous anodic tin oxide with well-defined nano-channeled structure was fabricated for the first time and its electrochemical properties were investigated for application to an anode in a rechargeable lithium battery. To prepare the thin film electrode, first, a bi-layer of porous anodic tin oxides with well-defined nano-channels and discrete nano-channels with lots of lateral micro-cracks was prepared by pulsed and continuous anodization processes, respectively. Subsequent to the Cu coating on the layer, well-defined nano-channeled tin oxide was mechanically separated from the specimen, leading to an electrode comprised of porous tin oxide and a Cu current collector. The porous tin oxide nearly maintained its initial nano-structured character in spite of there being a series of fabrication steps. The resulting tin oxide film electrode reacted reversibly with lithium as an anode in a rechargeable lithium battery. Moreover, the tin oxide showed far more enhanced cycling stability than that of powders obtained from anodic tin oxides, strongly indicating that this thin film electrode is mechanically more stable against cycling-induced internal stress. In spite of the enhanced cycling stability, however, the reduction in the initial irreversible capacity and additional improvement of cycling stability are still needed to allow for practical use.