• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.434-435
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• 2018

In this paper, a single-phase single-stage three-level AC/DC converter with a wide controllable output voltage is presented. It integrates a PFC converter and a three level DC/DC converter into one. The proposed converter operates at a fixed frequency and provides a wide controllable output voltage ($200V_{dc}-430V_{dc}$) with high efficiencies over a wide load range. In addition, the input boost inductors operate in a discontinuous mode to improve the input power factor. Moreover, all the switching devices operate with ZVS, and the converter's THD is small especially at full load. The feasibility of the proposed converter is verified with experimental results of a 1.5kW prototype.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.2
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• pp.184-191
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• 2013

In this paper, bidirectional AC-DC converter using dual half-bridge converter is proposed. A transformer leakage inductance in the dual half-bridge converter is used for making resonance with the capacitor of the voltage-doubler, which can help the switched current to be sinusoidal without extra inductive component and also the switching loss can be reduced through operation such as ZVS, ZCS. Both circuit analysis and design guideline are described, and also the feasibility for the proposed converter is shown through the hardware implementation and the experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2291-2294
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• 2003

In this paper, analysis and control design of ac-dc converter, normally nonlinear time-varying system, using sliding mode controller to achieve fast output voltage response, disturbance rejection and robust system in the presence of load variation are demonstrated. The objective of this method is to develop methodology for output voltage to be constant and input current sinusoidal that results in nearly unity power factor, respectively. In addition the converter can be also bidirectional power flow. Simulation results using Matlab/Simulink show the effectiveness of sliding mode control system compared with linear feedback controller to guarantee enhanced PF>0.98, THD<5%, and ripple output voltage is less than 1% at the maximum output power.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.1
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• pp.40-46
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• 2010

DC link electrolytic capacitors are widely used in various PWM power converter system, such as adjustable speed driver(ASD) or DC/DC converter. Electrolytic capacitors, which is the most of the time affected by aging effect, plays a very important role for the power electronics system quality and reliability. This objective of this paper is to propose a improvement method to detect the rise of equivalent series resistor(ESR) in order to realize the online failure prediction of electrolytic capacitor for DC link of PWM power converter. The ESR detection scheme is based on the determination of the electrolytic capacitor AC losses calculated from voltage/current measurement using AC coupling. Therefore, the preposed online failure prediction method has the merits of easy ESR computation and circuit simplicity compare with BPF method. Simulation results show the veridity of the proposed on-line ESR estimation method.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.4
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• pp.377-383
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• 1999

A new soft switching single stage AC-DC full bridge boost converter with unit input power factor and isolated output i is presented in this paper. Due to the use of a non-dissipative snubber on the primary side, a single stage high-power f factor isolated full bridge boost converter has a significant reduction of switching losses in the main switching devices. The non-dissipative snubber adopted in this study consists of a snubber capacitor Cr, a snubber inductor Cr, a fast r recovery snubber diode Dr' and a commutation diode Dp. This paper presents the complete operating principles, t theoretical analysis and experimental results.

• Journal of Power Electronics
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• v.13 no.5
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• pp.829-840
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• 2013

The modified sinusoidal pulse-width modulation (SPWM) is one of the PWM techniques used in three-phase AC-DC buck converters. The modified SPWM works without the current sensor (the converter is current sensorless), improves production of sinusoidal AC current, enables obtainment of near-unity power factor, and controls output voltage through modulation gain (ranging from 0 to 1). The main problem of the modified SPWM is the huge starting current and voltage (during transient) that results from a large step change from the reference voltage. When the load changes, the output voltage significantly drops (through switching losses and non-ideal converter elements). The single-input single-output (SISO) approach with minor-loop voltage feedback controller presented here overcomes this problem. This approach is created on a theoretical linear model and verified by discrete-model simulation on MATLAB/Simulink. The capability and effectiveness of the SISO approach in compensating start-up current/voltage and in achieving zero steady-state error were tested for transient cases with step-changed load and step-changed reference voltage for linear and non-linear loads. Tests were done to analyze the transient performance against various controller gains. An experiment prototype was also developed for verification.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.384-390
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• 2022

In this study, a single-stage, four-phase, interleaved, totem-pole AC-DC converter is proposed for a super-fast charger station that requires high power, a wide voltage range, and bidirectional operation capabilities and adopts various types of electric transport vehicles. The proposed topology is based on current-fed push-pull dual active bridge converter combined with the totem-pole operation. Owing to the four-phase interleaving effect, the bridge on the grid side can switch at 0.25, 0.5, and 0.75 to achieve a ripple-free grid current. The input filter can be removed theoretically. Switching methods for the duty of the secondary-side duty cycle are proposed, and they correspond to the primary duty cycle for reducing the circulating power and handling the total harmonic distortion. Therefore, the converter can operate under a wide voltage range. Experimental results from a 7.5 kW prototype are used to validate the proposed concept.

• Journal of Power Electronics
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• v.7 no.1
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• pp.44-54
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• 2007

Ac-dc power conversion can either be done with two separate converter stages or with a single converter stage. Two-stage ac-dc converters, however, can be costly and complex, while the performance of single-stage converters is compromised due to a reduced number of components. Several researchers have therefore proposed adding some sort of auxiliary circuit consisting of a second switch and some passive elements to single-stage converters to improve their performance. Although these modified single-stage converters may have two converters, they are not two-stage converters as they do not have two separate and independently controlled converters that are always operating to convert power from one form to another. In this paper, the operation of ac-dc single-stage converters is first reviewed and their strengths and weaknesses are noted. The operation of several modified single-stage converters, including one proposed by the authors, is then discussed, and the paper concludes by presenting experimental results that confirm the feasibility of the proposed converter.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.367-369
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• 1996

This paper proposed that a buck type AC-DC Converter for high power factor operates with four chopper connecting a number of parallel circuit. And, some simulative results on computer is included to confirm the validity of the analytical results.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.112-114
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• 2008

This paper proposes a new two-stage Z-source converter (TSZC). The purpose of the proposed system is to obtain the ac voltage with a maximum boost voltage for fuel cell applications as a renewable energy source. In order to provide a continuous current path, a switching strategy for the dc-ac ZSI and ac-ac ZSC of the proposed system was used. The operation principle, analysis and simulation results of 1.2 kW fuel cell stack were also presented.