• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.232-233
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• 2012

This paper presents an effective control scheme for an electric vehicle battery charger where a symmetrical bridgeless power factor-corrected converter and a buck converter are cascaded. Both converters have been popular in industries because of their high efficiency, low cost, and compact size, hence combining these converters makes the overall battery charging system strongly efficient. Moreover, this charger topology can operate at universal input voltage and attain a desired battery current and voltage without ripple. In order to achieve a unity input power factor and zero input current harmonic distortion, the proposed control scheme adopts duty ratio feed-forward control technique in both current and voltage control loop. Additionally, in the current loop, its reference is created by a phase-locked loop (PLL) block, leading to a pure sinusoidal input current although the input voltage waveform is being distorted. The feasibility and practical value of the proposed approach are verified by simulation and experiment with an 110V/60Hz ac line input and 1.5kW-72V dc output of the battery charging system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1401-1403
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• 2005

This paper presents generalized small-signal models for asymmetrically-driven double-ended dc-to-dc converters. The proposed small-signal models include the effects of the parasitic resistances, which have dominant influence on the damping of the secondary power stage double-pole. To confirm the validity of new models, an asymmetrical half-bridge converter with center-taped rectifier and a forward-flyback converter with current doubler rectifier were built, and their performances were compared with the theoretical predictions.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.259-264
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• 2009

This paper proposes a real-time estimation of the boost inductance in a single-phase AC/DC parallel PWM converter for high-speed EMU. The estimation procedure of the boost inductance is only based on the variation of input current and the input AC voltage measurement. The estimated boost inductance is optimized by the least square method. This estimation technique can improve the performance of current controller and reduce the harmonics of the input current in the feed-forward controller. The validity of proposed technique is verified through the MATLAB SIMULINK simulation results.

• Journal of Power Electronics
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• 제13권2호
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• pp.186-196
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• 2013

This paper presents a low voltage-stress AC-linked charge equalizing system for balancing the energy in a serially connected, valve-regulated lead acid battery string using a modular converter that consists of multiple transformers coupled together. Each converter was coupled through an AC-linked bus to increase the overall energy transfer efficiency of the system and to eliminate the problem of the unbalanced charging of batteries. Previous solutions are based on centralized and modularized topologies. A centralized topology requires a redesign of the hardware and related components. It also faces a high voltage stress when the number of batteries is expanded. Modularized solutions use low-voltage-stress, double-stage, DC-linked topologies which leads to poor energy transfer efficiency. The proposed solution uses a low-voltage stress, AC-linked, modularized topology that makes adding more batteries easier. It also has a better energy transfer efficiency. To ensure that the charge equalization system operates smoothly and safely charges batteries, a small intelligent microcontroller was used in the control section. The efficiency of this charge equalization system is 85%, which is 21% better than other low-voltage-stress DC-linked charging techniques. The validity of this approach was confirmed by experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.967_968
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• 2009

For lighting application, high-power LED nowadays is driven at 350mA and a sensing resistor is used to provide feedback for LED-current regulation. This method adds an IR drop at the output branch, and limits power efficiency as LED current is large and keeps increasing. In this paper, a power efficient LED-current sensing circuit is proposed. The circuit does not use any sensing resistor but extracts LED-current information from the output capacitor of the driver. Controlling the brightness of LEDs requires a driver that provides a constant, regulated current. In one case, the converter may need to step down the input voltage, and, in another, it may need to boost up the output voltage. These situations often arise in applications with wide-ranging ""dirty"" input power sources, such as automotive systems. And, the driver topology must be able to generate a large enough output voltage to forward bias the LEDs. So, to provide this requirements, 13W prototype Buck-Boost Converter is used.

• Journal of Power Electronics
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• 제18권2호
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• pp.407-417
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• 2018

A novel family of Buck mode three-level direct ac converters with a high frequency link is proposed. These converters can transfer an unsteady high ac voltage with distortion into a regulated sinusoidal voltage with a low THD at the same frequency. The circuit configuration is constituted of a three-level converter, high frequency transformer, cycloconverter, as well as input and output filters. The topological family includes forward, push-pull, half-bridge, and full-bridge modes. In order to achieve a reliable three-level ac-ac conversion, and to overcome the surge voltage and surge current of the cycloconverter, a phase-shifted control strategy is introduced in this paper. A prototype is presented with experimental results to demonstrate that the proposed converters have five advantages including high frequency electrical isolation, lower voltage stress of the power switches, bi-directional power flow, low THD of the output voltage, and a higher input power factor.

• 센서학회지
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• 제14권5호
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• pp.350-356
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• 2005

We have developed a dual-channel type automatic measurement system to evaluate AC-DC current transfer difference of the thermal current converter(TCC) which is primary standard of AC current. The output drift effect of the TCC is minimized by measuring simultaneously the output voltages of two TCCs using voltmeter. Furthermore, the offset voltage of the voltmeter is cancelled nearly out by taking the average values of two outputs of TCCs measured with the forward-reverse directions using dual channel scanner. The uncertainties of the automatic system were 7 to $86{\mu}A/A$ for 3 mA to 10 A at 40 Hz to 20 kHz, which were evaluated by the comparisons between adjacent range of TCCs and inter-comparison with national measurement institute of Germany(PTB). The capability for ac-dc transfer difference measurement was improved by one order compared with that for the manual ac-dc measurement system.

• 전력전자학회논문지
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• 제7권4호
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• pp.332-338
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• 2002

토카막 장치의 초전도 코일에 사용되는 전원 공급장치는 초대형급(20kA) 직류 전원 공급기로서 빠른 전류제어 응답성과 매우 작은 정상상태 리플이 필수적이다. 특히 역전류 공급이 가능한 회생형 컨버터의 운전중 전류 방향이 바뀌는 순간에도 전류기준값을 잘 추종하는 것이 중요하다. 이러한 조건들을 만족시키기 위하여 입력측에 2중 출력($\Delta$, Y)를 갖는 변압기와 출력단에 상간변압기(interphase transformer, IPT)를 이용한 12펄스 싸이리스터 듀얼 컨버터를 설계, 제작하였다. 각 컨버터에서 출력되는 전류의 합이 부하전류 지령치를 따르도록 제어하는 동시에 차 전류의 평균값이 영이 되도록 함으로써 각 컨버터의 부하 분담율을 일정하게 하여 상간 변압기의 포화를 방지한다. 대전류 코일 전류 공급장치의 양방향 전류 제어 성능을 높이기 위하여 위상각 검출 및 게이팅 지연각 구현을 디지털화하고 컨버터 전류방향 정역절환시 초기 응답특성을 개선하는 방법을 제안하였다. 또한 시뮬레이션과 실부하 전류실험을 통해 제안된 제어기의 동작성능을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1161-1162
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• 2011

본 논문에서는 독립된 DC 입력전원을 요구하는 Cascaded H-bridge 멀티레벨 인버터를 단일 입력전원으로 구동시키기 위한 회로 구조를 제안한다. 변압기 포화를 방지하기 위해 채용되는 리센 권선을 가지는 포워드 컨버터의 구조를 변경한 것으로 리셋 권선에 의해 전원으로 회생되는 에너지가 출력단으로 전달되도록 변경된다. 제안된 회로 구조의 입출력전압과 스위치의 도통비와의 관계를 이론적으로 분석하고 시뮬레이션을 통해 타당성을 검증한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.560-563
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• 2000

In this paper we proposed AC/DC boost converter to improve input current harmonic reduction in TIG welder. The proposed harmonic reduction circuit with UC2854AN acting on constant switching frequency average current control has a three-loop control structure : the inner current loop the line voltage feed-forward loop and th outer voltage loop. Also we applied the constant current strategy on full bridge IGBT inverter to stabilized the output current using the analog PI controller. To demonstrate the practical significance of the proposed methods some simulation studies and experimental results are presented.