• Title/Summary/Keyword: Cell Capacitance

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The Dual Design of Fuel Cell Hybrid Power System using Dual Converter PCS (1.5kW 연료전지 복합발전 시스템의 듀얼 컨버터 설계)

  • Shin, Soo-Cheol;Lee, Hee-Jun;Hong, Suk-Jin;Kim, Hak-Sung;Won, Chung-Yuen
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.7
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    • pp.67-75
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    • 2013
  • In this paper, parallel input/serial output dual converter is designed appropriately for fuel cell hybrid power system. In case of proposed converter, zero voltage switching condition is designed without additional resonance device using leakage inductance of transformer and output capacitance of switch, and zero voltage switching method is used. Also, the system method is for increasing power by connecting half-bridge in parallel and increasing output voltage by connecting secondary output of transformer in serial. Through this method we can increase power and decrease volume of system. So in this paper, dual converter is designed. 1.5kW fuel cell hybrid power system was implemented, and system operation and stability was verified through experiment.

High-efficiency fuel-cell power inverter with soft-switching resonant technique (Soft-switching resonant technique을 적용한 고효율 PEMFC inverter)

  • Han, K.H.;Cho, Y.R.;Baek, S.H.
    • Proceedings of the KIEE Conference
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    • 2005.10c
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    • pp.326-328
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    • 2005
  • In order to reduce the capital and overall operating cost of a fuel-cell system, a high-efficiency fuel-cell power inverter with a simple framework is required. The high-order two-inductance two-capacitance (LLCC) resonant technique is adopted in this study to implement a low-frequency 60-Hz sine wave voltage inverter utilized in the proton exchange membrane fuel-cell (PEMFC) system. The methodology for inverting dc voltage into low-frequency ac boltage is usually generated by the pulse-width-modulation (PWM) technique. However, the PWM-type inverter output has high-frequency harmonic components. Although an adequately designed filter could be utilized to overcome this problem, there are still some undesirable effects introduced by the high-frequency switching loss, electromagnetic-interference, harmonic current, and load variation. A novel power inverter via the LLCC resonant technique is designed for inverting dc voltage into 60-Hz ac sine wave voltage in the PEMFC system. This circuit scheme has the merits of low harmonic components, soft switching, high efficiency, and simplified implementation. The effectiveness of the proposed resonant inverter used for the PEMFC system is verified by numerical simulations and experimental results.

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Full Parametric Impedance Analysis of Photoelectrochemical Cells: Case of a TiO2 Photoanode

  • Nguyen, Hung Tai;Tran, Thi Lan;Nguyen, Dang Thanh;Shin, Eui-Chol;Kang, Soon-Hyung;Lee, Jong-Sook
    • Journal of the Korean Ceramic Society
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    • v.55 no.3
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    • pp.244-260
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    • 2018
  • Issues in the electrical characterization of semiconducting photoanodes in a photoelectrochemical (PEC) cell, such as the cell geometry dependence, scan rate dependence in DC measurements, and the frequency dependence in AC measurements, are addressed, using the example of a $TiO_2$ photoanode. Contrary to conventional constant phase element (CPE) modeling, the capacitive behavior associated with Mott-Schottky (MS) response was successfully modeled by a Havriliak-Negami (HN) capacitance function-which allowed the determination of frequency-independent Schottky capacitance parameters to be explained by a trapping mechanism. Additional polarization can be successfully described by the parallel connection of a Bisquert transmission line (TL) model for the diffusion-recombination process in the nanostructured $TiO_2$ electrode. Instead of shunt CPEs generally employed for the non-ideal TL feature, TL models with ideal shunt capacitors can describe the experimental data in the presence of an infinite-length Warburg element as internal interfacial impedance - a characteristic suggested to be a generic feature of many electrochemical cells. Fully parametrized impedance spectra finally allow in-depth physicochemical interpretations.

Bioelectrical Impedance Analysis at Popliteal Regions of Human Body using BIMS

  • Kim, J.H.;Kim, S.S.;Kim, S.H.;Baik, S.W.;Jeon, G.R.
    • 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.

Minimization of Cell Capacitance Voltage Ripple Using Second Order Harmonic Current on Modular Multi-Level Converter (2 고조파 전류를 이용한 Modular Multi-Level Converter의 셀 캐패시터 전압맥동 최소화)

  • Jung, Sungho;Lee, Hak-Jun;Sul, Seung-Ki
    • Proceedings of the KIPE Conference
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    • 2011.11a
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    • pp.67-68
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    • 2011
  • 본 논문에서는 Modular Multi-Level Converter(MMLC)의 셀(Cell) 캐패시터(Capacitor) 전압 밸런싱에서 전압맥동 최소화 방법을 제안한다. 암(Arm) 평균 전류를 직류성분으로만 제어 할 경우 기본파 주파수와 2 고조파로 흔들리는 순시전력 항이 셀 캐패시터 전압 맥동을 만든다. 이를 억제 하기위해 암 평균 전류에 2 고조파 교류 성분을 직류성분과 함께 제어하는 방법을 제안한다. 이 방법을 통하여 전압맥동을 줄일 수 있음을 밝히고, 주입되는 2 고조파 전류의 크기와 위상각 계산 방법을 제시한다. 모의실험 결과를 통해 제안된 방법의 유효성을 검증하였다.

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A Study on High Performance Converter Topology for Hydrogen Gas Generation Electrolysis System

  • Kang, Tae-Won;Go, Yu-Ran;Suh, Yong-Sug;Jeong, Jun-Ik;Rho, Do-Hawn
    • Proceedings of the KIPE Conference
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    • 2010.07a
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    • pp.196-197
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    • 2010
  • This paper investigates a high performance converter topology for hydrogen gas generation electrolysis system. The proposed converter topology consists of full-bridge inverter, medium frequency transformer, and diode rectifier. Hydrogen gas generation electrolysis process considered in the paper is analyzed and characterized by its equivalent circuit. The electrolysis cell is modeled as effective resistance, capacitance, inductance, and internal emf voltage source. The proposed converter topology provides enhanced efficiency of hydrogen gas generation process under the operating condition of dc output voltage with high frequency ripple on it. The high performance operation of proposed converter is confirmed through the simulation with the electrolysis cell considered in the equivalent circuit model.

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Photovoltaic effect in $\beta$-carotene glass ($\beta$-carotene glass의 광기전력효과)

  • 김의훈
    • 전기의세계
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    • v.20 no.4
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    • pp.23-30
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    • 1971
  • The photovoltaic behaviors ahve been observed with a sandwich-type cell, consisting of a junction between .betha.-carotene and stannic oxide conducting layer to provide a junction electrode. In the stannic oxide and .betha.-carotene junction it was found that its electromotive forse decreased to a value smaller than the original one. This is due to a space charge formation. Photovoltage reached approximately 40mV with an irradiation energy of 250Kcal/M$^{2}$hr. It appeared that a magnitude of the photovoltaic response was proportional to the logarithm of irradiance. The time constant of the photovoltaic effect was shown to be approximately 0.7 sec. The wavelength dependence of the photovoltaic behavior was very anomalous. It is assumed that such an anomalous photoresponse depends on a internal capacitance due to some bubble during process to make a cell.

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Electrochemical Characteristics of Activated Carbon Electrode for Supercapacitor (Supercapacitor용 활성탄 전극의 전기 화학적 특성)

  • 김경민;이용욱;강안수
    • Proceedings of the Safety Management and Science Conference
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    • 2002.11a
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    • pp.273-277
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    • 2002
  • In the electrode fabrication of unit cell, we found that optimal the electrochemical characteristics were obtained with at 90 wt.% of activated carbon(BP-20), 5 wt.% of conducting agent(Ppy, Super P) and 5 wt.% of P(VdF-co-HFP)/PVP mixed binder. The electrochemical characteristics of unit cell with Ppy improver were as follows : 37.6 F/g of specific capacitance, 0.98 $\Omega$ of AC-ESR, 2.92 Wh/kg and 6.05 Wh/L of energy density, and 754 W/kg and 1,562 W/L of power density. It was confirmed that internal resistance were reduced due to the increase of electrical conductivity and filling density by the introduction of conductivity agent, and content of conducting agent was suitable in the range of 4~6 wt.%. According to the impedance measurement of the electrode with conductivity agent, we found that it was possible to charge rapidly by the fast steady-state current convergence due to low equivalent series resistance(AC-ESR), fast charge transfer rate at interface between electrode and electrolyte, and low RC time constant.

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Study on Controlling Pretilt Angle and Electrical Characteristics in ECB cell by Polymerized Reactive Mesogen monomer (ECB 셀에서 UV 경화성 RM 단분자에 의한 선경사각 조절 및 전기적 특성에 관한 연구)

  • Jeon, Eun-Jeong;Kim, Seong-Su;Lim, Young-Jin;Lee, Myoung-Hoon;Lee, Seung-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.397-398
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    • 2008
  • We have studied the electrically controlled birefringence (ECB) mode using reactive mesogen (RM) monomer to control pretilt angle and improve electrical characteristics. The measure of capacitance confirmed new pretilt angle by RM monomer, and Voltage Holding Ratio (VHR) was increased more than normal ECB cell.

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An Efficient Delay Calculation Tool for Timing Analysis (타이밍 분석을 위한 효율적인 시간 지연 계산 도구)

  • Kim, Joon-Hee;Kim, Boo-Sung;Kal, Won-Koang;Maeng, Tae-Ho;Baek, Jong-Humn;Kim, Seok-Yoon
    • Proceedings of the KIEE Conference
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    • 1998.11b
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    • pp.612-614
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    • 1998
  • As chip feature size decrease, interconnect delay gains more importance. A accurate timing analysis required to estimate interconnect delay as well as cell delay. In this paper, we present a timing-level delay calculation tool of which the accuracy is bounded within 10% of SPICE results. This delay calculation tool generates delay values in SDF(Standard Delay Format) for parasitic data extracted in SPEF(Standard Parasitic Exchange Format). The efficiency of the tool is easily seen because it uses AWE(Asymptotic Waveform Evaluation) algorithm for interconnect delay calculation, and precharacterized library and effective capacitance model for cell delay calculation.

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