• Title/Summary/Keyword: Operation voltage

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Analysis of Hybrid Converter with Wide Voltage Range Operation

  • Lin, Bor-Ren
    • Journal of Power Electronics
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    • v.19 no.5
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    • pp.1099-1107
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    • 2019
  • A soft switching converter with wide voltage range operation is investigated in this paper. A series resonant converter is implemented to achieve a high circuit efficiency with soft switching characteristics on power switches and rectifier diodes. To improve the weakness of the narrow voltage range in LLC converters, an alternating current (ac) power switch is used on the primary side to select a half-bridge or full-bridge resonant circuit to implement 4:1 voltage range operation. On the secondary-side, another ac power switch is adopted to select a full-wave rectifier or voltage-doubler rectifier to achiever an additional 2:1 output voltage range. Therefore, the proposed resonant converter has the capacity for 8:1 (320V~40V) wide output voltage operation. A single-stage hybrid resonant converter is employed in the study circuit instead of a two-stage dc converter to achiever wide voltage range operation. As a result, the study converter has better converter efficiency. The theoretical analysis and circuit characteristics are verified by experiments with a prototype circuit.

Target Operation Voltage Guidelines Considering Voltage Level in Each Voltage Control area by Applying Optimization Technique Through EMS Data Observation (EMS data 분석 및 최적화 기법을 적용한 제어지역별 목표운전전압 제안)

  • Sung, Ung;Kim, Jae-Won;Kim, Tae-Gyun;Lee, Byong-Jun;Jung, Eung-Soo;Cho, Jong-Man
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.4
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    • pp.671-678
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    • 2009
  • This paper presents target operation voltage guidelines of each voltage control area considering both voltage stability and economical efficiency in real power system. EMS(Energy Management System) data, Real-time simulator, shows not only voltage level but lots of information about real power system. Also this paper performs optimal power flow calculation of three objective functions to propose the best target operation voltage. objective function of interchange power flow maximum and active power loss minimization stand for economical efficiency index and reactive power reserve maximum objective unction represents stability index. Then through simulation result using optimazation technique, the most effective objective function is chosen. To sum up, this paper divides voltage control area into twelve considering electric distance characteristics and estimate or voltage level by the passage of time of EMS peak data. And through optimization technique target operation voltage of each voltage control area is estimated and compare heir result. Then it is proposed that the best scenario to keep up voltage stability and maximize economical efficiency in real power system.

CCD Image Sensor with Variable Reset Operation

  • Park, Sang-Sik;Uh, Hyung-Soo
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.3 no.2
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    • pp.83-88
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    • 2003
  • The reset operation of a CCD image sensor was improved using charge trapping of a MOS structure to realize a loe voltage driving. A DC bias generating circuit was added to the reset structure which sets reference voltage and holds the signal charge to be detected. The generated DC bias is added to the reset pulse to give an optimized voltage margin to the reset operation, and is controlled by adjustment of the threshold voltage of a MOS transistor in the circuit. By the pulse-type stress voltage applied to the gate, the electrons and holes were injected to the gate dielectrics, and the threshold voltage could be adjusted ranging from 0.2V to 5.5V, which is suitable for controlling the incomplete reset operation due to the process variation. The charges trapped in the silicon nitride lead to the positive and negative shift of the threshold voltage, and this phenomenon is explained by Poole-Frenkel conduction and Fowler-Nordheim conduction. A CCD image sensor with $492(H){\;}{\times}{\;}510(V)$ pixels adopting this structure showed complete reset operation with the driving voltage of 3.0V. The resolution chart taken with the image sensor shows no image flow to the illumination of 30 lux, even in the driving voltage of 3.0V.

An Improvement in Synchronously Rotating Reference Frame-Based Voltage Sag Detection under Distorted Grid Voltages

  • Sillapawicharn, Yutthachai;Kumsuwan, Yuttana
    • Journal of Electrical Engineering and Technology
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    • v.8 no.6
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    • pp.1283-1295
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    • 2013
  • This study proposed an improvement in synchronously rotating reference frame-based voltage sag detection under distorted grid voltages. In the past, the conventional synchronously rotating reference frame (CSRRF)-based voltage sag detection was generally used in the voltage sag compensation applications. Its disadvantage is a long delay of detection time. The modified synchronously rotating reference frame (MSRRF)-based voltage sag detection is able to detect the voltage sag with only a short delay in detection time. However, its operation under distorted grid voltage conditions is unavailable. This paper proposed the improvement of modified synchronously rotating reference frame (IMSRRF)-based voltage sag detection for use in distorted grid voltages with very fast operation of voltage sag detection. The operation of the proposed voltage sag detections is investigated via simulations and experimentations to verify the performance of the IMSRRF-based voltage sag detection.

Response Characteristics for Low Voltage Liquid Crystal Display Employing a Constant Charge Model

  • Kim, Mi-Soon;Huh, Su-Jung;Suh, Duck-Jong;Ahn, Yi-Joon;Lee, Kyung-Jin;Ahn, Seon-Hong;Kim, Kyeong-Hyeon;Kim, Sang-Soo
    • 한국정보디스플레이학회:학술대회논문집
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    • 2008.10a
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    • pp.228-230
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    • 2008
  • The response time characteristic of low voltage liquid crystals (LCs) is investigated and a new simulator for low voltage LCs is proposed. In order to enable low voltage operation, it is important to minimize Vth of LCs and variation of pixel voltage caused by dynamic capacitance operation of LC Display. Because dynamic capacitance variation is much larger for low voltage LC operation compared to that of conventional LC material, it is necessary to make a better model for dynamic capacitance operation. A proposed minimizing Vth of LCs and variation of pixel voltage study results through a new constant charge model improve response characteristics for low voltage LCs operation.

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Development of Low-voltage Seamless Transfer Microgrid on Grid-connected Type Islands by Autonomous Operation (자율운전에 의한 계통연계형 도서의 저압 무순단 마이크로그리드 구축)

  • Kim, Jeong Hun;Kwon, Jung-Min;Yun, Sang-Yun
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.66 no.4
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    • pp.169-176
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    • 2017
  • This paper presents research on low-voltage microgrids to maintain a continuous power supply to critical loads on grid-connected islands in Korea. The low-voltage microgrids of this paper focused on that changes public office buildings into uninterrupted microgrids by autonomous operation. For this, a microgrid controller (MGC) and a power conditioning system (PCS) that allow a seamless transfer between grid-connected and grid-isolated operation are proposed. The proposed PCS operates with a silicon controlled rectifier (SCR) switch and employs a simple structure. It supplies power continuously without operators through a coordinated operation between MGC and PCS. In addition, proposed MG has a schedule operation for minimizing electricity charges and provides ancillary services that enable the utilization of resources according to the operation purpose of utility distribution networks. To demonstrate the uninterrupted low-voltage microgrid proposed in this study, a microgrid was implemented and tested in a public office building in Anjwa Island, Jeollanam-do in Korea. A seamless, autonomous operation history, despite system disturbances, was obtained through a long-term demonstration of operation. The results showed that the proposed microgrid technology can be used to achieve energy resilience in grid-connected island areas.

DC Bus Voltage Regulation With Six-Step Operation in Maritime DC Power System (식스 스텝 운전을 이용한 선박용 DC 전력 시스템의 직류단 전압 제어)

  • Yun, Jonghun;Son, Young-Kwang;Sul, Seung-Ki
    • The Transactions of the Korean Institute of Power Electronics
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    • v.26 no.4
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    • pp.263-270
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    • 2021
  • Active AC/DC converters with PWM operation are utilized to regulate rectified DC bus voltage of a permanent magnet synchronous generator in the maritime DC power system. A DC bus voltage regulation strategy that exploits the six-step operation is proposed in this study. Compared with that of the PWM operation, switching loss of the converter can be significantly reduced under the six-step operation. Moreover, conduction loss can also be reduced due to the high modulation index and reduced flux-weakening current of the six-step operation. A controller is used for the proposed DC bus voltage regulation strategy to verify its validity with the simulation and experimental setup. The simulation and the experimental test results showed that the converter loss reduces to a maximum of 70% and 19%, respectively.

A Study on the Stability of High Density SRAM Cell) (고집적 SRAM Cell의 동작안정화에 관한 연구)

  • Choi, Jin-Young
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.11
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    • pp.71-78
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    • 1995
  • Based on the popular 4-transistor SRAM cell, an analytical expression of the minimum cell ratio was derived by modeling the static read operation. By analyzing the relatively simple expression for the minimum cell ratio, which was derived assuming the ideal transistor characteristics, effects of the changes in supply voltage and process parameters on the minimum cell ratio was predicted, and the minimum power supply voltage for read operation was determined. The results were verified by simulations utilizing the suggested simulation method, which is suitable for monitoring the lower limit of supply voltage for proper cell operation. From the analysis, it was shown that the worst condition for cell operation is low temperature and low supply voltage, and that the operation margin can be effectively improved by reducing the threshold voltage of the cell transistors.

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Operation modes and Protection of VS(Vertical Stabilization) Converter for International Thermonuclear Experimental Reactor (국제 핵융합실험로용 VS(Vertical Stabilization) 컨버터의 운전모드 및 보호동작)

  • Jo, Hyunsik;Jo, Jongmin;Oh, Jong-Seok;Suh, Jae-Hak;Cha, Hanju
    • The Transactions of the Korean Institute of Power Electronics
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    • v.20 no.2
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    • pp.130-136
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    • 2015
  • This study describes the structure and operation modes of vertical stabilization (VS) converter for international thermonuclear experimental reactor (ITER) and proposes a protection method. ITER VS converter supplies voltage (${\pm}1000V$)/current (${\pm}22.5kA$) to superconducting magnets for plasma current vertical stabilization. A four-quadrant operation must be achieved without zero-current discontinuous section. The operation mode of the VS converter is separated in 12-pulse mode, 6-pulse mode and circulation current mode according to the magnitude of the load current. Protection measures, such as bypass and discharge, are proposed for abnormal conditions, such as over current, over voltage, short circuit, and voltage sag. VS converter output voltage is controlled to satisfy voltage response time within 20 msec. Bypass operation is completed within 60 msec and discharge operation is performed successfully. The feasibility of the proposed control algorithm and protection measure is verified by assembling a real controller and implementing a power system including the VS converter in RTDS for a hardware-in-loop (HIL) facility.

5-Level Inverter for Excitation Voltage Control of SRM (SRM의 여자전압제어를 위한 5-레벨 인버터)

  • Lee, S.H.;Park, S.J.;Ahn, J.W.
    • Proceedings of the KIEE Conference
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    • 2000.11b
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    • pp.294-296
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    • 2000
  • Energy recovery in the regenerative region is very important when SRM(Switched Reluctance Motor) is used in traction drive. This is because that to reduce energy loss during mechanical braking and/or to have a high efficiency drive during braking. To control excitation voltage in motor operation and regenerative voltage in the generator operation in the SRM, multi-level voltage control is effective. This paper suggests multi-level inverter which is useful for motoring and regenerative operation in SRM.

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