• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.247-248
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• 2012

본 논문에서는 빌딩용 직류배전에 적용된 리던던트 전력 시스템을 제안하였다. 제안한 시스템 방식은 3상 다이오드 정류회로를 AC/DC 컨버터와 병렬로 연결하여 전력변환장치의 유지보수 시 직류전원의 무정전 공급이 가능하도록 하였다. 이에 따라 제안된 시스템의 구성에 대하여 기술하고, 시뮬레이션을 통하여 리던던트 전력 시스템의 타당성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.50-51
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• 2012

The paper presents a non-isolated bidirectional DC-DC converter for use in renewable power generation, battery, electric vehicles (EV) and small scale DC-UPS systems. In the propose design, the conventional interleaved operation of two-inductor boost structure is modified to accommodate bidirectional operation, and zero-voltage-transition (ZVT) is applied, where both the switch and the rectifier diode achieve soft condition without increasing their voltage and current stresses. The proposed converter has the merits of simple circuitry, reduced size, low cost and high efficiency. The operation principle of the converter is analyzed and verified. Also, simulation results of the proposed bidirectional dc-dc converter is shown.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1334-1339
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• 2004

This paper proposes transformerless power conversion system consisting of a single-phase diode rectifier and a shunt hybrid filter for the electric-railway system. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multi-level inverter. Compared with conventional active filters. Transformers are not used. Also, LC filter works as not only a harmonic filter tuned at the 5th harmonic frequency but also a switching-ripple filter. The rating of the active filter can be decreased by using a NPC type multi-level inverter. The simulation results confirm the validity of the system.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1427-1432
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• 2004

This paper proposes transformerless power conversion system consisting of a single-phase diode rectifier and a shunt hybrid filter for the electric-railway system. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multi-level inverter. Compared with conventional active filters. Transformers are not used. Also, LC filter works as not only a harmonic filter tuned at the 5th harmonic frequency but also a switching-ripple filter. The rating of the active filter can be decreased by using a NPC type multi-level inverter. The simulation results confirm the validity of the system

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.59-64
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• 2015

This paper proposes an analysis and operation strategy of a grid-connected wind turbine system using a diode rectifier. The currents of generators are the same as that of a small wind turbine system. Therefore, the analysis of generator torque is required as opposed to an analysis of blade speed. In this paper, the appropriate MPPT control method is proposed to control generator torque. Usefulness of the proposed operation strategy is verified by simulations and experiments.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.338-340
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• 2001

Power factor improved for single-phase buck-converter is studied in the paper. To sinusoidal waveform the input current with a near-unity power factor over a wide variety of operating conditions, the output capacitor is operated with voltage reversibility for the supply by arranging the auxiliary diode and power switching device. Then the output voltage is superposed on the input voltage during on time duration of power switching devices in order to minimize the input current distortion caused by the small input voltage when changing the polarity. The tested setup, using two insulated gate bipolar transistors(IGBT) and a microcomputer, is implemented and IGBT are switched with 20[kHz], which is out of the audible band. Moreover, a rigorous state-space analysis is introduced to predict the operation of the rectifier. The simulated results confirm that the input current can be sinusoidal waveform with a near-unity power factor and a satisfactory output voltage regulation can be achieved.

• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.46-48
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• 2003

A single phase voltage-controlled active power filter(APF) is introduced to improve power quality and to reduce harmonic generated from nolinear loads. Real and reactive power control scheme was addressed using a new power circuit model. By analyzing the reactive power, a unit power factor control scheme was proposed. Simulation and experiment results using a nonlinear diode rectifier showed that the voltage-controlled APF, unlike the current-controlled APF, can reduce the voltage harmonics as well as current harmonics. Also the results showed that the input power factor was greatly improved.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.6
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• pp.77-84
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• 1997

buck type converter doesn't appear when an input voltag eis lower than an output voltage. This is the main reason the buck converter has not been used for high power factor converters. In this paper, soft switching high power factor buck converter is proposed. This converter is composed of diode rectifier, input capacitor can be small enough to filter input current, buck converter with loss less snubber circuit. Converter is operated in discontinous conduction mode, turn on of the switching device is a zero current switching (ZCS) and high powr factor input is obtianed. In addition, zero voltage switching (ZVS) at trun off is achieved and switching loss is reduced using loss less snubber circuit. The capacitor used in the snubber circuit raised output voltage. Therefore, proposed converter has higher output voltage and higher efficiency than conventional buck type converter at same duty factor in discontinous conduction mode operation. High power factro, efficiency, soft switching operation of proposed converter is veified by simulation using Pspice and experimental results.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.2
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• pp.50-54
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• 2010

Soft recovery (SR) quasi-resonant converter (QRC) including a Folding snubber network (FSN) is introduced. It is obtained by combining normal quasi-resonant converter with folding snubber network of which the surrounding components are composed of passive devices only (diodes and capacitors). The reverse recovery loss of the main rectifier diode is eliminated by this method utilizing quasi resonance with Folding snubber network. By realizing soft switching condition, the proposed converter has PWM capability with high efficiency and is suitable for high output current and high power DC to DC converter application.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.166-168
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• 2004

Conventional Switched Mode Power Supplies(SMPS) with diode-capacitor rectifier have distorted input current waveform with high harmonic order contents. Typically, these SMPS have a power factor lower than 0,7. To improve with this problem the power factor correction(PFC) circuit of power supplies has to be introduced. Specially, to the reduce size and manufacture cost of power conversion device, the single-stage PFC converter is increased to demand as necessary of study. In this paper, comparative analysis of Valley-fill, boost and feedforward type single stage power factor correction circuit based on the flyback converter is given. Also, the validity of designed three type of single stage PFC circuit are confirmed by simulation and experimental results.