• Title/Summary/Keyword: Negative Capacitance

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Robust Circulating Current Control in MMC Under the Unbalanced Voltage Condition (불평형 전압 조건에 강인한 모듈형 멀티레벨 컨버터의 순환전류 억제기법)

  • Moon, Ji-Woo;Park, Jung-Woo;Kang, Dae-Wook;Kim, Jang-Mok
    • Proceedings of the KIEE Conference
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    • 2015.07a
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    • pp.996-997
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    • 2015
  • This paper proposes parameter design principle of the sub-module capacitance, Arm inductance and a control method to reduced the circulating currents in modular multilevel converter(MMC) under unbalanced voltage conditions. Under balanced voltage conditions, only negative-sequence circulating currents exist. Consequently, the conventional method has considered only negative-sequence circulating currents in MMC. However, under unbalanced voltage conditions, there are positive-sequence, zero-sequence and negative-sequence circulating currents in MMC. Thus, under unbalanced voltage conditions, a control method should consider these all components. This study proposes the control method to reduced the circulating currents under the unbalanced voltage.

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The Study on the Active Power Filter in Unbalanced Load (불평형 부하에서의 능동필터에 관한 연구)

  • Choi, See-Young;Lee, Woo-Cheol;Lee, Taeck-Kie;Hyun, Dong-Seok
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.50 no.3
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    • pp.130-140
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    • 2001
  • This paper presents the performance of a parallel active power filter(PT) system in unbalanced load condition. The unbalanced load leads to negative sequence of current, and makes 120Hz ripple in the DC-link voltage forcing large capacitance and increases the rating of APF. thus, the separation of negative sequence is performed in synchronous reference frame and controlled to flow into supply network. The validity of the scheme is investigated through simulation and the experimental results for a prototype active power filter system rated at 10kVA.

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The far-end crossta1k voltage for CMOS-IC load

  • Miyao, Nobuyuki;Noguchi, Yasuaki;Matsumoto, Fujihiko
    • Proceedings of the IEEK Conference
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    • 2002.07c
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    • pp.1878-1881
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    • 2002
  • The capacitance of nonlinear component such as a CMOS inverter varies largely around the threshold voltage. We measured the far-end crosstalk of two parallel microstrip lines with the CMOS inverter load near the threshold voltage of the CMOS inverter, The negative voltage of the crosstalk agrees with that for a 4pF capacitor toad. The positive voltage of the crosstalk hardly changes of the amplitude of the input step voltage.

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Accurate Equation Analysis for RF Negative Resistance circuit at High Frequency Operation Range (고주파수 영역의 정확도 높은 RF 부성저항 회로 분석)

  • Yun, Eun-Seung;Hong, Jong-Phil
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.4
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    • pp.88-95
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    • 2015
  • This paper presents a new analysis of RF negative resistance (RFNR) circuits, known as a negative resistance generator. For accurate equation analysis of RFNR, this study examined the effects of the gate resistance and the source parasitic capacitance of the transistor. In addition, the input admittance of the conventional equation was calculated by looking into the source-terminal of the transistor, whereas that of the proposed equation was calculated by examining the gate-terminal of the transistor. The proposed equation analysis is more accurate than that of the conventional analysis, especially for higher frequency range. This paper verify the accuracy of the proposed analysis at high frequency range using the simulation.

Compact Metamaterial-Based Tunable Zeroth-Order Resonant Antenna with Chip Variable Capacitor

  • Jung, Youn-Kwon;Lee, Bomson
    • Journal of electromagnetic engineering and science
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    • v.13 no.3
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    • pp.189-191
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    • 2013
  • This letter presents a compact metamaterial-based tunable zeroth-order resonant antenna. It is based on the double-negative unit cell with a function of tunable inductance realized by a varactor and impedance convertor in the shunt branch. The resonant frequency of the designed antenna ranges from 2.31 to 3.08 GHz, depending on the capacitance of the used varactor. Its size is very compact ($0.05{\lambda}_0{\times}0.2{\lambda}_0$) with a relatively wide tunable range of 29.1%. The impedance bandwidth of the antenna is from 20 to 50 MHz for the resonant center frequency. The measured maximum total realized gain is from -0.68 dBi (2.43 GHz) to 1.69 dBi (2.97 GHz). The EM-simulated and measured results are in good agreement.

Magnetoresistance Characteristics due to the Schottky Contact of Zinc Tin Oixide Thin Films (ZTO 박막의 쇼키접합에 기인하는 자기저항특성)

  • Li, XiangJiang;Oh, Teresa
    • Journal of the Semiconductor & Display Technology
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    • v.18 no.4
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    • pp.120-123
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    • 2019
  • The effect of surface plasmon on ZTO thin films was investigated. The phenomenon of depletion occurring in the interface of the ZTO thin film created a potential barrier and the dielectric layer of the depletion formed a non-mass particle called plasmon. ZTO thin film represents n-type semiconductor features, and surface current by plasma has been able to obtain the effect of improving electrical efficiency as a result of high current at positive voltage and low current at negative voltage. It can be seen that the reduction of electric charge due to recombination of electronic hole pairs by heat treatment of compound semiconductors induces higher surface current in semiconductor devices.

The Comparison of Shampoos for Skin Hydration by Measurement of Epidermal Capacitance in Normal Canine Skin (Epidermal Capacitance를 이용한 시판되는 치료용 샴푸의 정상적인 개 피부에 대한 가수효과)

  • Oh, Tae-Ho;Jae-Hoon heong;Jang, Kwang-Ho
    • Journal of Veterinary Clinics
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    • v.18 no.3
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    • pp.206-210
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    • 2001
  • Various commercial shampoos were frequently prescribed for dermatologic therapy in small animal practice. Skim hydration affected by the shampoos, however, was not evaluated routinely. In order to evaluate the skin hydration for the exact prescription of shampoos method to measure skin hydration of shampoos are needed. This study was undertaken to evaluate the skin hydration effect of shampoo on canine skin using Corneometer. Five healthy dogs were applied with 7 commercial shampoos: Humilac, Sebocalm, Sebolytics, Etiderm, Benzoyl peroxide, HyLyt and Zn-7 Derm. Skin hydrations were evaluated by measurement of electrical capacitance by Corneometer. A statistically significant increase in skim hydration was found 17(p<0.05) and 77 minutes(p<0.01) after application of Humilac indicating a humidifying effect of this product. A statistically significant decrease in skin hydration was found for the Benzoyl peroxide after 77 minutes(p<0.05). No statistically significant differences between the other shampoos were found. None of the products tested had any negative effect on the skin barrier function. The Corneometer was found useful for detecting skin hydration to shampoos and considered as a simple and useful tool for prescription of various shampoos routine practice.

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Polymorphic Phase Transition and Temperature Coefficient of Capacitance of Alkaline Niobate Based Ceramics

  • Bae, Seon-Gi;Shin, Hyea-Gyiung;Sohn, Eun-Young;Im, In-Ho
    • Transactions on Electrical and Electronic Materials
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    • v.14 no.2
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    • pp.78-81
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    • 2013
  • $0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3+0.2wt%\;Ag_2O$ (hereafter, No excess NKN) ceramics and $0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3+0.2wt%\;Ag_2O$ with excess $(Na_{0.5}K_{0.5})NbO_3$ (hereafter, Excess NKN) were fabricated by the conventional solid state sintering method, and their phase transition properties and dielectric properties were investigated. The crystalline structure of No excess NKN ceramics and Excess NKN ceramics were shown characteristics of polymorphic phase transition (hereafter, PPT), especially shift from the orthorhombic to tetragonal phase by increasing sintering temperature range from $1,100^{\circ}C$ to $1,200^{\circ}C$. Also, the temperature coefficient of capacitance (hereafter, TCC) of No excess NKN ceramics and Excess NKN ceramics from $-40^{\circ}C$ to $100^{\circ}C$ was measured to evaluate temperature stability for applications in cold regions. The TCC of No excess NKN and Excess NKN ceramics showed positive TCC characteristics at a temperature range from $-40^{\circ}C$ to $100^{\circ}C$. Especially, Excess NKN showed a smaller TCC gradient than those of Excess NKN ceramics in range from $-40^{\circ}C$ to $100^{\circ}C$. Therefore, NKN piezoelectric ceramics combined with temperature compensated capacitor having negative temperature characteristics is desired for usage in cold regions.

Effects of Peripheral Pentacene Region on C-V Characteristics of Metal-Oxide-Pentacene Capacitor Structure

  • Jung, Keum-Dong;Jin, Sung-Hun;Park, Chang-Bum;Shin, Hyung-Cheol;Park, Byung-Gook;Lee, Jong-Duk
    • 한국정보디스플레이학회:학술대회논문집
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    • 2005.07b
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    • pp.1284-1287
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    • 2005
  • Peripheral pentacene region gives a significant influence on C-V characteristics of metal-oxide-pentacene capacitor structure. When the gate voltage goes toward negative, the effect of peripheral pentacene region becomes larger. Remaining gate DC bias constant and changing small signal frequency, the capacitance of peripheral pentacene changes along with frequency so that the total capacitance value also changes. The influence of peripheral pentacene region should be removed to measure accurate C-V characteristics, because it is hard to take into account the effect of the region quantitatively. After removing the influence of peripheral pentacene region, acceptor concentration, flat band voltage and depletion width of pentacene thin film are extracted from an accurate C-V curve as $1.58{\times}10^{17}cm^{-3}$, -1.54 V and 39.4 nm, respectively.

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Implementation and Problem Analysis of Phase Shifted dc-dc Full Bridge Converter with GaN HEMT (Cascode GaN HEMT를 적용한 위상 천이 dc-dc 컨버터의 구현 및 문제점 분석)

  • Joo, Dong-Myoung;Kim, Dong-Sik;Lee, Byoung-Kuk;Kim, Jong-Soo
    • The Transactions of the Korean Institute of Power Electronics
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    • v.20 no.6
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    • pp.558-565
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    • 2015
  • Gallium nitride high-electron mobility transistor (GaN HEMT) is the strongest candidate for replacing Si MOSFET. Comparing the figure of merit (FOM) of GaN with the state-of-the-art super junction Si MOSFET, the FOM is much better because of the wide band gap characteristics and the heterojunction structure. Although GaN HEMT has many benefits for the power conversion system, the performance of the power conversion system with the GaN HEMT is sensitive because of its low threshold voltage ($V_{th}$) and even lower parasitic capacitance. This study examines the characteristics of a phase-shifted full-bridge dc-dc converter with cascode GaN HEMT. The problem of unoptimized dead time is analyzed on the basis of the output capacitance of GaN HEMT. In addition, the printed circuit board (PCB) layout consideration is analyzed to reduce the negative effects of parasitic inductance. A comparison of the experimental results is provided to validate the dead time and PCB layout analysis for a phase-shifted full-bridge dc-dc converter with cascode GaN HEMT.