• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.6
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• pp.87-95
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• 2006

In this study, in order to obtain high qualify of electric power, single phase active filter which is composed of Zig-Zag transformer and three phase bridge rectifier and capacitor at the secondary of its transformer to be able to reduce the components of the zero phase current and the third harmonic current in neutral line and power line respectively. By connecting this filter to the Zig-Zag transformer and nonlinear load, their third harmonic components due to the nonlinear loads were reduced.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1235-1247
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• 2019

Zero-Voltage-Switching (ZVS) operation for a Wireless Power Transfer (WPT) system can be achieved by designing a ZVS controller. However, the performance of the controller in some industrial applications needs to be designed tightly. This paper introduces a ZVS controller design method for WPT systems. The parameters of the controller are designed according to the desired performance based on the closed loop dominant pole placement method. To describe the dynamic characteristics of the system ZVS angle, a nonlinear dynamic model is deduced and linearized using the small signal linearization method. By analyzing the zero-pole distribution, a low-order equivalent model that facilitates the controller design is obtained. The parameters of the controller are designed by calculating the time constant of the closed-loop dominant poles. A prototype of a WPT system with the designed controller and a five-stage multistage series variable capacitor (MSVC) is built and tested to verify the performance of the controller. The recorded response curves and waveforms show that the designed controller can maintain the ZVS angle at the reference angle with satisfactory control performance.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.6
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• pp.13-21
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• 2010

A energy efficient $V_{pp}$ generator using a variable pumping frequency for mobile DRAM is presented in this paper. The proposed $V_{pp}$ generator exploits 3 stages of a cross-coupled charge pump for energy efficiency. Instead of using a fixed pumping frequency in the conventional $V_{pp}$ generator, our proposed $V_{pp}$ generator adopts a voltage-controlled oscillator and uses variable frequencies to reduce the ramp-up time. As a result, our $V_{pp}$ generator generates 3.0 V output voltage with 24.0-${\mu}s$ ramp-up time at 2 mA current load and 1 nF capacitor load with 1.2 V supply voltage. Experimental results show that the proposed $V_{pp}$ generator consumes around 26% less energy (1573 nJ $\rightarrow$ 1162 nJ) and reduces 29% less ramp-up time (33.7-${\mu}s$ $\rightarrow$ 24.0-${\mu}s$) compared to the conventional approach.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.8
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• pp.107-114
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• 2017

In this paper, a novel power factor compensation system based on voltage-controlled method is proposed for 3-phase 4-wire power system. The proposed voltage-controlled power factor compensation system generates a reactive power required for compensation by applying a variable output voltage by a slidac to a capacitor. In conventional power factor compensation system using the capacitor bank method, the power factor compensation error occurs depending on the load condition due to the limited capacity of the capacitors. However, the proposed system compensates the power factor up to 100% without error. In this paper, we have developed a voltage-controlled power factor compensation system and a control algorithm for 3-phase 4-wire power system, and verify its performance through simulation and experiments. If the proposed power factor compensation system is applied to an industrial field, a power factor compensation performance can be maximized. As a result, it is possible to reduce of electricity prices, reduce of line loss, increase of load capacity, ensure the transmission margin capacity, and reduce the amount of power generation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.4
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• pp.300-306
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• 2004

This paper reports a novel tunable bandpass filter using two-state switched inductor with direct-contact MEMS switches for wireless LAN applications. In our filter configuration, the switched inductor is implemented to obtain more stable and much larger frequency tuning ratio compared with variable capacitor-based tunable filter. The proposed tunable filter was fabricated using a micromachining technology and electrical performances of the fabricated filter were measured. The filter consists of spiral inductors, MIM capacitors and direct-contact type MEMS switches, and its frequency tunability is achieved by changing the inductance that is induced by ON/OFF actuations of the MEMS switches. The actuation voltage of the MEMS switches was measured of 58 V, and they showed the insertion loss of 0.1 dB and isolation of 26.3 dB at 2 GHz, respectively. The measured center frequencies of the fabricated filter were 2.55 GHz and 5.1 GHz, respectively. The passband insertion loss and 3-dB bandwidth were 4.2 dB and 22.5 % at 2.55 GHz, and 5.2 dB and 23.5 % at 5.1 GHz, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.10
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• pp.1973-1981
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• 1994

A PLDRO(Phase Locked Dielectric Resonator Oscillator) in Ku-band(10.95-11.70GHz) is designed with the concept of the feedback property of PLL(Phase Locked Loop). A series feedback type DRO is developed, and VCDRO(Voltage Controlled Dielectric Resonator Oscillator) using a varactor diode as a voltage-variable capacitor is implemented to tune oscillating frequency electrically. Then, PLDRO is designed by using a SPD(Sampling Phase Detector). This PLDRO is phase-locked voltage controlled DRO to reference source(VHF band) by SPD at 10.00 GHz for European FSS(Fixed Satellite Service). The PLDRO generates output power greater than 10dBm at 10.00 GHz and has phase noise of -80 dBc/Hz at 10 KHz offset from carrier. This PLDRO achieves much better frequency stability than conventional VCDRO.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1305-1317
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• 2015

Distributed generation systems (DGSs) have been getting more and more attention in terms of renewable energy use and new generation technologies in the past decades. The self-excited induction generator (SEIG) occupies an important role in the area of energy conversion due to its low cost, robustness and simple control. Unlike synchronous generators, the SEIG has to absorb capacitive reactive power from the outer device aiming to stabilize the terminal voltage at load changes. This paper presents a novel static VAR compensator (SVC) called a magnetic energy recovery switch (MERS) to serve as a voltage controller in SEIG powered DGSs. In addition, many small scale SEIGs, instead of a single large one, are applied and devoted to promote the generation efficiency. To begin with, an expandable mathematic model based on a d-q equivalent circuit is created for parallel SEIGs. The control method of the MERS is further improved with the objective of broadening its operating range and restraining current harmonics by parameter optimization. A hybrid control strategy is developed by taking both of the stand-alone and grid-connected modes into consideration. Then simulation and experiments are carried out in the case of single and double SEIG(s) generation. Finally, the measurement results verify that the proposed DGS with SVC-MERS achieves a better stability and higher feasibility. The major advantages of the mentioned variable reactive power supplier, when compared to the STATCOM, include the adoption of a small DC capacitor, line frequency switching, simple control and less loss.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.6
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• pp.65-72
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• 2001

This paper deals with a novel full digital control of the single-phase PWM(Pulse Width Modulation) inviter for UPS(Uninterruptible Power Supp1y). The voltage and current of output filter capacitor as a state variable are the feedback control input. In the proposed scheme a double deadbeat control consisting of minor current control loop and major voltage control loop have been developed In addition, a second order deadbeat currents control which should be exactly equal to its reference in two sampling time without error and overshoot is proposed to remove the influence of the calculation time delay. The load current prediction is achieved to compensate the load disturbance. The simulation and experimental result shows that the proposed system offers an output voltage with THD(Total Harmonic Distortion) less than 5% at a full nonlinear load.

• KIEE International Transactions on Power Engineering
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• v.3A no.1
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• pp.27-34
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• 2003

In this paper, the power conditioner composed of the stand-alone single-phase squirrel cage rotor type self-excited induction generator (SEIG) driven by prime movers such as a wind turbine and a micro gas turbine (MGT) is presented by using the steady-state circuit analysis based on the two nodal admittance approaches using the per-unit frequency in addition to a new state variable defined by the per-unit slip frequency along with its performance evaluations for the stand-alone energy utilizations. The stande-alone single-phase SEIG operating performances in unregulated voltage control loop are then evaluated on line under the conditions of the speed change transients of the prime mover and the stand-alone electrical passive load power variations with the simple theoretical analysis and the efficient computation processing procedures described in the part I of this paper. In addition, a feasuible PI controlled feedback closed-loop voltage regulation scheme of the stande-alone single-phase SEIG is designed on the basis of the static VAR compensate. (SVC) and discussed in experiment for the promising stand-alone power conditioner. The experimental operating performance results are illustrated and give good agreements with the simulation ones. The simulation and experimental results of the stand-alone single-phase SEIG with the simple SVC controller for its stabilized voltage regulation prove the practical effectiveness of the additional SVC control loop scheme including the PI controller with fast response characteristics and steady-sate performance improvements.

• Journal of Electrical Engineering and information Science
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• v.3 no.2
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• pp.239-244
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• 1998

Piezoelectric pressure sensors and pyroelectric infrared detectors based on ZnO thin film have been integrated with GaAs metal-semiconductor field effect transistor (MESFET) amplifiers. Surface micromachining techniques have been applied in a GaAs MESFET process to form both microsensors and electronic circuits. The on-chip integration of microsensors such as pressure sensors and infrared detectors with GaAs integrated circuits is attractive because of the higher operating temperature up to 200 oC for GaAs devices compared to 125 oC for silicon devices and radiation hardness for infrared imaging applications. The microsensors incorporate a 1${\mu}$m-thick sputtered ZnO capacitor supported by a 2${\mu}$m-thick aluminum membrane formed on a semi-insulating GaAs substrate. The piezoelectric pressure sensor of an area 80${\times}$80 ${\mu}$m2 designed for use as a miniature microphone exhibits 2.99${\mu}$V/${\mu}$ bar sensitivity at 400Hz. The voltage responsivity and the detectivity of a single infrared detector of an area 80${\times}$80 $\mu\textrm{m}$2 is 700 V/W and 6${\times}$108cm$.$ Hz/W at 10Hz respectively, and the time constant of the sensor with the amplifying circuit is 53 ms. Circuits using 4${\mu}$m-gate GaAs MESFETs are fabricated in planar, direct ion-implanted process. The measured transconductance of a 4${\mu}$m-gate GaAs MESFET is 25.6 mS/mm and 12.4 mS/mm at 27 oC and 200oC, respectively. A differential amplifier whose voltage gain in 33.7 dB using 4${\mu}$m gate GaAs MESFETs is fabricated for high selectivity to the physical variable being sensed.