• 전기학회논문지
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• 제67권7호
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• pp.809-815
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• 2018

Distributed generations (DGs) using renewable energy resources in power systems have been widely integrated, and many of these DGs have intermittency. DGs can significantly affect the overall voltage profile of the system through the reactive power control for a voltage support. Therefore, in the planning stage of the optimal operation and dispatch of voltage regulation devices, DGs' hosting capacity with the reactive power control scheme should be considered. In this paper, we model the IEEE 34-bus test feeder, including all essential equipment. An optimization method is utilized to determine the optimal siting and operation of the voltage regulation devices in the presence of DGs with reactive power control scheme. Finally, we compare the optimal results of the each case to analyze the relationship among the hosting capacity of the DGs and voltage regulation devices operation.

• Transactions on Electrical and Electronic Materials
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• 제17권2호
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• pp.57-68
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• 2016

In this study, we present the modern hybrid system based power generation for electric vehicle applications. We describe the hybrid structure of modified current source based DC - DC converters used to extract the maximum power from Photovoltaic (PV) and Fuel Cell system. Due to reduced dc-link capacitor requirement and higher reliability, the current source inverters (CSI) better compared to the voltage source based inverter. The novel control strategy includes Distributed Maximum Power Point Tracking (DMPPT) for photovoltaic (PV) and fuel cell power generation system. The proposed DC - DC converters have been analyzed in both buck and boost mode of operation under duty cycle 0.5>d, 0.5<d<1 and 0.5<d for capable electric vehicle applications. The proposed topology benefits include one common DC-AC inverter that interposes the generated power to supply the charge for the sharing of load in a system of hybrid supply with photovoltaic panels and fuel cell PEM. An improved control of Direct Torque and Flux Control (DTFC) based induction motor fed by current source converters for electric vehicle.In order to achieve better performance in terms of speed, power and miles per gallon for the expert, to accepting high regenerative braking current as well as persistent high dynamics driving performance is required. A simulation model for the hybrid power generation system based electric vehicle has been developed by using MATLAB/Simulink. The Direct Torque and Flux Control (DTFC) is planned using Xilinx ISE software tool in addition to a Modelsim 6.3 software tool that is used for simulation purposes. The FPGA based pulse generation is used to control the induction motor for electric vehicle applications. FPGA has been implemented, in order to verify the minimal error between the simulation results of MATLAB/Simulink and experimental results.

• 한국결정성장학회지
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• 제7권2호
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• pp.334-340
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• 1997

불순물 주입에 의한 $SrTiO_3$ 박막의 전기적 특성 개선에 관하여 연구하였다. 잉여 SrO가 첨가되고 Fe, Cr 이온이 불순물 도핑된 박막은 $550^{\circ}C$, $Ar/O_2$비를 변화시키면서 형성되었다. 어셉터 이온 도핑에 의한 누설전류 특성이 개선됨을 알 수 있었다. 5 mol% SrO가 첨가되고, $550^{\circ}C$, $Ar/O_2$비가 5 : 5에서 형성된 $SrTiO_3$ 박막의 유전상수 값은 320, 누설전류 밀도는 $1.0 {\times} 1.0 A/\textrm{cm}^2$까지 개선될 수 있었다. 이러한 결과는 고유전 박막의 전기적 특성을 향상시킴으로써 차세대 메모리 유전체 물질 개발에 응용될 수 있을 것으로 기대한다.

• Journal of Electrical Engineering and Technology
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• 제5권3호
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• pp.353-362
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• 2010

This paper presents a centralized control algorithm for power system performance in the Korean power system using Flexible AC Transmission Systems (FACTS) devices. The algorithm is applied to the Korean power system throughout the metropolitan area in order to alleviate inherent stability problems, especially concerns with voltage stability. Generally, control strategies are divided into local and centralized control. This paper is concerned with a centralized control strategy in terms of the global system. In this research, input data of the proposed algorithm and network data are obtained from the SCADA/EMS system. Using the full system model, the centralized controller monitors the system condition and decides the operating point according to the control objectives that are, in turn, dependent on system conditions. To overcome voltage collapse problems, load-shedding is currently applied in the Korean power system. In this study, the application of the coordination between FACTS and switch capacitor (SC) can restore the solvability without load shedding or guarantee the FV margin when the margin is insufficient. Optimal Power Flow (OPF) algorithm, for which the objective function is loss minimization, is used in a stable case. The results illustrate examples of the proposed algorithm using SCADA/EMS data of the Korean power system in 2007.

• Journal of Power Electronics
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• 제17권5호
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• pp.1298-1307
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• 2017

The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.

• 한국전기전자재료학회논문지
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• 제19권9호
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• pp.808-812
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• 2006

In this dissertation, Ru-Zr metal gate electrode deposited on two kinds of dielectric were formed for MOS capacitor. Sample co-sputtering method was used as a alloy deposition method. Various atomic composition was achieved when metal film was deposited by controlling sputtering power. To study the characteristics of metal gate electrode, C-V(capacitance-voltage) and I-V(current-voltage) measurements were performed. Work function and equivalent oxide thickness were extracted from C-V curves by using NCSU(North Carolina State University) quantum model. After the annealing at various temperature, thermal/chemical stability was verified by measuring the variation of effective oxide thickness and work function. This dissertation verified that Ru-Zr gate electrodes deposited on $SiO_{2}\;and\;ZrO_{2}$ have compatible work functions for NMOS at the specified atomic composition and this metal alloys are thermally stable. Ru-Zr metal gate electrode deposited on $SiO_{2}\;and\;ZrO_{2}$ exhibit low sheet resistance and this values were varied with temperature. Metal alloy deposited on two kinds of dielectric proposed in this dissertation will be used in company with high-k dielectric replacing polysilicon and will lead improvement of CMOS properties.

• 한국철도학회논문집
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• 제20권2호
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• pp.190-195
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• 2017

본 논문에서는 임피던스 측정을 통한 레일절손을 검지하는 방법에 대해서 제시하도록 한다. 일반적으로 레일절손은 궤도회로를 통해 실시간으로 판단을 하나 궤도회로를 사용하지 않고 레일의 임피던스를 측정함으로 인해서 절손유무와 절손위치를 추정하였다. 레일의 한쪽에 병렬공진을 발생시켜 전기적으로 절연을 함으로써 다른쪽 레일의 임피던스가 측정되도록하였다. 측정된 임피던스가 인덕턴스 성분을 가지면 레일의 절손이 존재하지 않으며, 캐패시턴스 성분을 가지면 레일의 절손이 발생하게된다. 전송선로모델을 이용하여 제시한 구조를 모델링하였으며, 모델링을 통해 임피던스 값에 따라 절손위치가 추정가능함을 보였다. 실제 60m 레일 모형에 대해서 제안한 방법으로 임피던스를 측정하였으며, 임피던스 값에 따라 절손유무가 판단이 되는 것을 확인하였다.

• 한국지능시스템학회논문지
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• 제24권5호
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• pp.457-461
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• 2014

생물학적 신경 세포의 모델링을 위한 펄스타입 실리콘 뉴런 회로를 $0.18{\mu}m$ CMOS 공정을 이용하여 반도체 집적회로로 설계하였다. 제안하는 뉴런 회로는 입력 전류신호를 위한 커패시터 입력단과, 출력 전압신호 생성을 위한 증폭단 및 펄스신호 초기화를 위한 MOS 스위치로 구성된다. 전압신호 입력을 전류신호 출력으로 변환하는 기능의 시냅스 회로는 몇 개의 PMOS와 NMOS 트랜지스터로 이루어지는 범프회로를 사용한다. 제안하는 뉴런 모델의 검증을 위하여, 2개의 뉴런과 시냅스가 직렬연결된 뉴런체인을 구성하여 SPICE 모의실험을 실시하였다. 모의실험 결과, 뉴런신호의 생성과 시냅스 전달특성의 정상적인 동작을 확인하였다.

• Journal of Power Electronics
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• 제16권3호
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• pp.1209-1217
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• 2016

This paper presents a novel charge pump scheme that combines the advantages of Fibonacci and Dickson charge pumps to obtain 30 V voltage for display driver integrated circuit application. This design only requires four external capacitors, which is suitable for a small-package application, such as smart card displays. High-amplitude (<6.6 V) clocks are produced to enhance the gate drive of a Dickson charge pump and improve the system's current drivability by using a voltage-doubler charge pump with a pulse skip regulator. This regulation engages many middle-voltage devices, and approximately 30% of chip size is saved. Further optimization of flying capacitors tends to decrease the total chip size by 2.1%. A precise and simple model for a one-stage Fibonacci charge pump with current load is also proposed for further efficiency optimization. In a practical design, its voltage error is within 0.12% for 1 mA of current load, and it maintains a 2.83% error even for 10 mA of current load. This charge pump is fabricated through a 0.11 μm 1.5 V/6 V/32 V process, and two regulators, namely, a pulse skip one and a linear one, are operated to maintain the output of the charge pump at 30 V. The performances of the two regulators in terms of ripple, efficiency, line regulation, and load regulation are investigated.

• 전기전자학회논문지
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• 제15권4호
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• pp.319-323
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• 2011

본 논문에서는 Mobile 기기의 다양한 기능을 지원하기 위해 사용되는 내부 회로들의 낮은 전압 레벨을 지원하기위해 가장 널리 사용되는 SMPS(Switch Mode Power Supply)방식의 Buck converter를 설계한다. 제안된 Buck converter는 넓은 부하 영역에서 높은 효율을 가지는 것을 목적으로 일반적인 구동 방식인 PWM (Pulse Width Modulation)Mode의 고 효율 저 리플 특성 구현 외에 PFM(Pulse Frequency Modulation) Mode를 적용하여 낮은부하 조건 혹은 부하를 사용하지 않는 대기 시간에서도 고 효율 저 리플 특성을 가지는 Dual mode synchronous buck converter를 설계한다. 이를 위해 본 논문에서는 부하 변동 시에 PWM - PFM Mode로의 효율적인 변환방법 및 저 리플 특성을 위한 방법을 제안한다. 또한 제안된 IC는 Mobile 기기에 부합하는 입력 전압 범위 2.5V-5V를 가지며, 2.5Mhz의 높은 주파수로 동작하여 리플 특성이 양호하고 집적화가 유리하다. 고효율을 위하여 Synchronous Type 설계 및 Dynamic Control 방식을 적용하였다. 보호 기능으로는 회로 동작의 초기 시에 발생하는 Inrush Current를 방지하기 위한 Soft start function 외에 Current limit, Thermal shutdown function, UVLO 회로가 내장되어 신뢰성을 높였다.