• Title/Summary/Keyword: Charge balance

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Interleaved DC-DC Converters with Partial Ripple Current Cancellation

  • Lin, Bor-Ren;Chiang, Huann-Keng;Cheng, Chih-Yuan
    • Journal of Power Electronics
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    • v.12 no.2
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    • pp.249-257
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    • 2012
  • An interleaved PWM converter is proposed to implement the features of zero voltage switching (ZVS), load current sharing and ripple current reduction. The proposed converter includes two ZVS converters with a common clamp capacitor. With the shared capacitor, the charge balance of the two interleaved parts is automatically regulated under input voltage and load variations. The active-clamping circuit is used to realize the ZVS turn-on so that the switching losses on the power switches are reduced. The ZVS turn-on of all of the switching devices is achieved during the transition interval. The interleaved pulse-width modulation (PWM) operation will reduce the ripple current and the size of the input and output capacitors. The current double rectifier (CDR) is adopted in the secondary side to reduce output ripple current so that the sizes of the output chokes and capacitor are reduced. The circuit configuration, operation principles and design considerations are presented. Finally experimental results based on a 408W (24V/17A) prototype are provided to verify the effectiveness of the proposed converter.

Synthesis and Light-emitting Properties of Poly (fluorene) Copolymers Containing EDOT Comonomer

  • Hwang, Do-Hoon;Park, Moo-Jin;Lee, Ji-Hoon
    • Journal of Information Display
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    • v.5 no.4
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    • pp.12-17
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    • 2004
  • A series of statistical random copolymers of dioctylfluorene (DOF) and 3,4-ethylenedioxythiophene (EDOT) were synthesized by Ni (0) mediated polymerization and their light-emitting properties were compared with poly (9,9-di-n-octylfluorene) (PDOF). The synthesized polymers were characterized using UV-vis spectroscopy, TGA, photoluminescence (PL) & electroluminescence (EL) spectroscopy and by conducting molecular weight studies. The resulting polymers were found to be thermally stable and readily soluble in organic solvents. The UV-visible absorption and PL emission spectra of the copolymers were gradually red-shifted as the fraction of EDOT in copolymers increased. Light-emitting devices were fabricated in an ITO (indium-tin oxide)/PEDOT/polymer/Ca/Al configuration. Interestingly, the EL spectra of these devices were similar to the PL spectra of the corresponding polymer film. However, the EL devices constructed from the copolymer showed more than 10 times higher efficiency level than the devices constructed from the PDOF homopolymer. This higher efficiency is possibly the result of better charge carrier balance in the copolymer systems due to the lower HOMO levels of the copolymers in comparison to that of PDOF homopolymer.

Efficient Organic Light-emitting Diodes with Aluminum-doped Zinc Oxide Anodes (알루미늄 도핑된 산화아연 양극을 적용한 고효율 유기발광다이오드)

  • Lee, Ho-Nyeon;Lee, Young-Gu;Jung, Jong-Guk;Lee, Seung-Eui;Oh, Tae-Sik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.8
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    • pp.711-715
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    • 2007
  • Properties of organic light-emitting diodes (OLEDs) with aluminum-doped zinc oxide (ZnO:Al) anodes showed different behaviors from OLEDs with indium tin oxide (ITO) anodes according to driving conditions. OLEDs with ITO anodes gave higher current density and luminance in lower voltage region and better EL and power efficiency under lower current density conditions, However, OLEDs with ZnO:Al anodes gave higher current density and luminance in higher voltage region over about 8V and better EL and power efficiency under higher current density over $200mA/cm^2$. These seemed to be due to the differences in conduction properties of semiconducting ZnO:Al and metallic ITO. OLEDs with ZnO:Al anodes showed nearly saturated efficiency under high current driving conditions compared with those of OLEDs with ITO anodes. This meant better charge balance in OLEDs with ZnO:Al anodes. These properties of OLEDs with ZnO:Al anodes are useful in making bright display devices with efficiency.

A Comparative Study on the Electrostatic Eliminator of Piezo Type Ionizer and Pulse AC Corona Type Ionizer (피에조를 이용한 코로나 방전과 펄스교류 코로나 방전을 이용한 정전기 제거장치의 비교 연구)

  • Kwon, Sung-Yul;Lee, Dong-Hoon;Choi, Jae-Wook
    • Journal of the Korean Society of Safety
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    • v.24 no.6
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    • pp.50-54
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    • 2009
  • Ionizer is used for improving manufacturing process and reducing inferior goods in the clean room. As a general rule, neutralization of the electrostatic charge is most important to make TFT-LCD, PDP and OLED. Pulse AC-static eliminator with output voltage of about 10.5kV has been used these days as neutralization device. But this device has a problem with lower performance which was caused by particles-adhesion on the electrode when it has been used for a long time. So we studied to solve the problem with lower performance using high Frequency(72kHz) static eliminator which was produced by Piezo transformer device, and compared Pulse-AC type with Piezo-electronic device such as decay time and ion balance for 10 weeks periods. As a result of this study, we found that Piezo transformer device has been maintained normal condition for 10 weeks. Also, we made the rule by this study, normally Piezo transformer device has to clean the electrode during every 11th weeks.

Fuzzy Droop Control considering SOC Balancing of BESSs (다수 BESS의 SOC Balancing을 고려한 퍼지 드룹 제어)

  • Han, Seong-Geun;Yoo, Hyeong-Jun;Kim, Hak-Man
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.4
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    • pp.616-622
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    • 2015
  • A microgrid which is composed of distributed generation systems, energy storage systems and loads is operated in the grid-connected mode and in the islanded mode. Especially, in the islanded mode, a microgrid should maintain frequency in the allowed range. The frequency is decided by a balance between power supply and power demand. In general, the frequency is controlled by using battery energy storage systems (BESSs) in the microgrid. Especially, droop control is applied to controlling BESSs in the microgrid. Meanwhile, over-charging and deep-discharging of BESS in operation and control cause life-shortening of batteries. In this paper, a fuzzy droop control is proposed to change droop gains adaptively by considering state of charge (SOC) of BESSs to improve the life cycle of the battery. The proposed fuzzy droop control adjusts droop gains based on SOC of BESSs in real time. In other to show the performance of the proposed fuzzy droop control, simulation based on Matlab/Simulink is performed. In addition, comparison of the convention droop control and the proposed fuzzy droop control is also performed.

Electroluminescence Characteristics of a New Green-Emitting Phenylphenothiazine Derivative with Phenylbenzimidazole Substituent

  • Ahn, Yeonseon;Jang, Da Eun;Cha, Yong-Bum;Kim, Mansu;Ahn, Kwang-Hyun;Kim, Young Chul
    • Bulletin of the Korean Chemical Society
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    • v.34 no.1
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    • pp.107-111
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    • 2013
  • A new green-emitting material with donor-acceptor architecture, 3,7-bis(1'-phenylbenzimidazole-2'-yl)-10-phenylphenothiazine (BBPP) was synthesized and its thermal, optical, and electroluminescent characteristics were investigated. Organic light-emitting diodes (OLEDs) with four different multilayer structures were prepared using BBPP as an emitting layer. The optimized device with the structure of [ITO/2-TNATA (40 nm)/BBPP (30 nm)/TPBi (30 nm)/Alq3 (10 nm)/LiF (1 nm)/Al (100 nm)] exhibited efficient green emission. Enhanced charge carrier balance and electron mobility in the organic layers enabled the device to demonstrate a maximum luminance of 31,300 cd/$m^2$, a luminous efficiency of 6.83 cd/A, and an external quantum efficiency of 1.62% with the CIE 1931 chromaticity coordinates of (0.21, 0.53) at a current density of 100 mA/$cm^2$.

An Experimental Stuff on the Performance of Multi-type Heat Pump using Capillary Tubes (모세관을 이용한 멀티형 열펌프의 신뢰성에 관한 실험적 연구)

  • 권영철;장근선;이윤수;김대훈;전용호;이상재
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.9
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    • pp.749-755
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    • 2002
  • In order to develop a multi-type heat pump system with two indoor units of non-uniform capacities, the optimum refrigerant circuit was developed using capillary tubes. The refrigerant circuit was composed of four main parts, a heating circuit, a cooling circuit, a by-pass circuit and a balance circuit. The system characteristics of multi-type heat pump was investigated through the rating test and the reliability test, using the multi-type psy-chrometric calorimeter. The results of the rating test showed that the capacity of the multi-type heat pump was about 93% of the design value. In particular, the capacity of cooling single mode was about 13% higher than the design value, and the capacity of heating multi mode was about 5% higher than the design value. The reliability of the multi-type heat pump was verified by various reliability tests (overload, extension tube, freeze up, under/over charging, sweat, flood back). The optimal amount of refrigerant charge and compressor capacity were determined from the present work.

Ionic Equilibria Analysis of $NiCl_2$ in Chloride Solutions by Using Bromley Equation (염산용액에서 Bromley식을 이용한 염화니켈의 이온평형해석)

  • Lee Man-Seung;Lee Gwang-Seop
    • Resources Recycling
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    • v.12 no.3
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    • pp.38-45
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    • 2003
  • ionic equilbria of nickel chloride in hydrochloric acid solutions were analyzed by considering chemical equilibria, mass and charge balance equations. The activity coefficients of solutes were calculated by using Bromley equation. It was found that most of species containing nickel existed as $Ni^{2+}$$NiCl^{+}$. The mole fractions of nickel hydroxides were very low in the con-centration ranges considered in this study and the mole fraction of$Ni_4$ $(OH)_{4}^{4+}$ increased greatly with the pH of the solution. The pH values of $NiCl_2$ $-HCl-NaOH-H_2$O system at $25^{\circ}C$ calculated in this study agreed well with those experimentally measured up to ionic strength of 9.4m.

Integrated Control Strategy of Multiple BESS for providing Primary Frequency Control (주파수추종서비스 제공을 위한 다수 배터리전기저장장치(BESS)의 통합제어 전략)

  • Yu, Ga Ram;Choi, Woo Yeong;Kook, Kyung Soo
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.7
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    • pp.1169-1175
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    • 2016
  • As an Increased penetration level of renewable resources has caused concerns about primary frequency response, an increase in BESS(Battery Energy Storage System) capacity has been expected because of its fast response to the disturbances in the power system. This paper proposes the Integrated Control Strategy of multiple BESS for effectively providing the primary frequency control in the bulk power systems by coordinating the response, SOC and its recovery of BESS. The proposed strategy prevents multiple BESS from providing exceeding response and keeps the balance between SOC of multiple BESS. In addition, It would recover the SOC of BESS efficiently. The effectiveness of the proposed strategy is verified through various case studies employing Korean power system.

Highly Enhanced EL Properties of PF Copolymers with Pyrazole Derivatives (피라졸 유도체를 함유한 폴리알킬플루오렌 공중합체의 향상된 EL 특성)

  • Kang, In-Nam;Lee, Ji-Hoon
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.7
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    • pp.539-544
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    • 2010
  • We have synthesized new blue electroluminescent polyalkylfluorene-based copolymers [poly(F-co-Py)x:y, where x:y = 99:1 or 95:5 mole ratios] containing the hole-injecting pyrazole derivative [3,3'-(4,6-bis(octyloxy)-1,3-phenylene)bis(1,5-diphenyl-4,5-dihydro-1H-pyrazole] through Ni(0) mediated polymerization, and their electroluminescent properties were investigated. Electroluminescent (EL) devices were fabricated with ITO / PEDOT:PSS (110 nm) / copolymers or PF homopolymer (80 nm) / Ca (50 nm) / Al (200 nm) configuration. Each EL device constructed from the copolymer exhibited significantly enhanced brightness and efficiency compared with a device constructed from the PF homopolymer. The EL device constructed with poly(F-co-Py)99:1 exhibited the highest luminous efficiency and brightness (0.95 cd/A and $2,907\;cd/m^2$, respectively). The achieved luminous efficiency was an excellent result, providing almost a 4-fold improvement on the efficiency obtainable with the a PF homopolymer device. This enhanced efficiency of the copolymer devices results from their improved hole injection and more efficient charge carrier balance, which arises from the HOMO level (~5.83 eV) of the poly(F-co-Py)99:1 copolymer, which is higher than that of the PF homopolyme (~5.90 eV).