• 조명전기설비학회논문지
• /
• 제15권2호
• /
• pp.64-72
• /
• 2001

본 논문에서는 비접촉 충전 에너지 전달을 위한 포워드 ZVS MRC(Zero Voltage Switching Multi Resonant Converter)를 제안하였다. 포워드 ZVS MRC는 기생성분을 흡수하는데 그리고 스위칭손실을 최소화하는데 효과적이다. 이것은 높은 주파수동작에 적합하며 따라서 이것을 비접촉 충전에너지 전달에 적용하였다. 사용된 컨버터는 분리형 트랜스포머와 동기식정류기를 이용하였다. 갭의 크기에 따른 결합계수(k), 누설인덕턴스, 결합인 덕턴스 그리고 공진 주파수를 측정하였다. 구해진 값을 이용하여 회로를 설계, 구현하였으며 제안된 회로는 PSPICE로 시뮬레이션하였고 실험하였다. 주스위치의 전압 스트래스와 출력전력을 측정하였으며 제안된 컨버터가 비접촉 충전 에너지 전달에 적합함을 보였다.

• 조명전기설비학회논문지
• /
• 제28권6호
• /
• pp.99-105
• /
• 2014

Power transformers are applied throughout the power system to connect systems of different voltage to one another. Since a ratio differential relay offers high sensitivity in detection of internal faults in power transformers, it is widely used in the main protection system. The use of nonlinear devices such as rectifiers and other devices utilizing solid state switching have been increased in industry during recent years. For nonlinear loads, the load current is not proportional to the instantaneous voltage. This situation creates harmonic distortion on the system. The harmonic could differential relay misoperation if not recognized. This paper aims at analyzing and probing into the influences of harmonics on a ratio differential relay for power transformer protection.

• Journal of Power Electronics
• /
• 제14권4호
• /
• pp.661-670
• /
• 2014

A new DC/DC converter with zero voltage switching is proposed for applications with high input voltage and high load current. The proposed converter has two circuit modules that share load current and power rating. Interleaved pulse-width modulation (PWM) is adopted to generate switch control signals. Thus, ripple currents are reduced at the input and output sides. For high-voltage applications, each circuit module includes two half-bridge legs that are connected in series to reduce switch voltage rating to $V_{in}/2$. These legs are controlled with the use of asymmetric PWM. To reduce the current rating of rectifier diodes and share load current for high-load-current applications, two center-tapped rectifiers are adopted in each circuit module. The primary windings of two transformers are connected in series at the high voltage side to balance output inductor currents. Two series capacitors are adopted at the AC terminals of the two half-bridge legs to balance the two input capacitor voltages. The resonant behavior of the inductance and capacitance at the transition interval enable MOSFETs to be switched on under zero voltage switching. The circuit configuration, system characteristics, and design are discussed in detail. Experiments based on a laboratory prototype are conducted to verify the effectiveness of the proposed converter.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2017년도 추계학술대회
• /
• pp.429-432
• /
• 2017

본 논문에서는 고성능 비교기를 이용한 전파정류 애너지 하베스팅 회로를 설계하였다. 설계된 회로는 크게 Negative Voltage Converter, Active Diode단으로 나뉜다. 그리고 Active Diode단에 포함된 비교기는 3-stage 형태로 구현 하였으며 Pre-amplification, Decision circuit, Output buffer단으로 나뉜다. 이 비교기는 Propagation delay를 줄이고 하베스팅 회로의 전압 및 전력 효율을 향상 시키는 것이 주된 목적이다. 제안된 회로는 Magna $0.35{\mu}m$ CMOS 공정으로 설계하였으며, 모의실험을 통해 동작을 검증하였다. 설계된 에너지 하베스팅 회로의 칩 면적은 $612{\mu}m{\times}444{\mu}m$이다.

• Journal of Power Electronics
• /
• 제15권2호
• /
• pp.399-410
• /
• 2015

A 6.5 V/50 kA high-frequency switching power supply (HSPS) system composed of 10 power modules is developed to meet the requirements of copper-foil electrolysis. The power module is composed of a two-leg pulse width modulation (PWM) rectifier and a DC/DC converter. The DC/DC converter adopts two full-wave rectifiers in parallel to enhance the output. For the two-leg PWM rectifier, the ripple of the DC-link voltage is derived. A composite control method with a ripple filter is then proposed to effectively improve the performance of the rectifier. To meet the process demand of copper-foil electrolysis, the virtual impedance-based current-sharing control method with load current full feedforward is proposed for n-parallel DC/DC converters. The roles of load current feedforward and virtual impedance are analyzed, and the current-sharing control model of the HSPS system is derived. Virtual impedance is used to adjust the current-sharing impedance without changing the equivalent output impedance, which can effectively reduce current-sharing errors. Finally, simulation and experimental results verify the structure and control method.

• Journal of Power Electronics
• /
• 제15권4호
• /
• pp.994-1005
• /
• 2015

This paper presents a novel power control strategy for PWM current-source rectifiers (CSRs) in the stationary frame based on the instantaneous power theory. In the proposed control strategy, a virtual resistance based on the capacitor voltage feedback is used to realize the active damping. In addition, the proportional resonant (PR) controller under the two-phase stationary coordinate is designed to track the ac reference current and to avoid the strong coupling brought about by the coordinate transformation. The limitations on improving steady-state performance of the PR controller is investigated and mitigated using a cascaded lead-lag compensator. In the z-domain, a straightforward procedure is developed to analyze and design the control-loop with the help of MATLAB/SISO software tools. In addition, robustness against parameter variations is analyzed. Finally, simulation and experimental results verify the proposed control scheme and design method.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2012년도 전력전자학술대회 논문집
• /
• pp.379-380
• /
• 2012

A bidirectional full-bridge CLLC resonant converter using a digital control method is proposed for a LVDC power distribution system. This converter can operate under high power conversion efficiency since the CLLC resonant network has soft switching capability for primary switches and output rectifiers. In addition, the power conversion efficiency of any directions is exactly the same as each other because of the symmetric structure of the converter. Intelligent digital control methods are proposed to regulate output voltage under any power flow directions. A 5kW prototype converter was designed for a high-frequency galvanic isolation of 380V dc buses using a digital signal processor to verify the performance of the proposed topology and algorithms.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.276-278
• /
• 2005

For over 25 years, the stray currents from DC electric railroads have caused serious interference problems with underground metallic infrastructures in Korea. The most serious interference is reported at the pipelines near the depot areas. Our field survey proves that this phenomena is mainly due to the missing of dedicated rectifiers for mainline, depot and/or workshop areas. Because it takes so much time and costs too much to replace the traction power system, we consider a stray current confinement method which collects the stray currents and drains them to the negative terminal of the rectifier. This can be realized by installing a stray current collecting wire along the depot boundary. Moreover, we found the stray current collecting reinforcement bar located beneath the rails of concrete slab tracks. Using this bar, we arc going to draing the stray currents from mainline rails. In this paper we show the result of field survey on railroad facilities and present the stray current confinement method under field test.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
• /
• pp.1480-1482
• /
• 2005

The major causes of power quality deterioration are harmonic current through semiconductor switching device, due to use of nonlinear loads such as diodes rectifier or thyristor rectifiers. In response to this concerns, this paper presents a new control method of single-phase active power filter(APF) for the compensation of harmonic current components in nonlinear loads. In order to make the complex calculation to be possible, the single-phase system that has two phases was made by constructing a imaginary second-phase giving time delay to load currents. In the conventional method, a imaginary-phase lagged to the load current T/4(here T is the fundamental cycle) was made. But in this proposed method, the new signal, which has the delayed phase through the filter, using the phase-delay property of low-pass filter, was used as the second phase. As this control method is applied to the system of single phase, an instantaneous calculation was done rather by using the rotating reference frames that synchronizes with source-frequency than by applying instantaneous reactive power theory that uses the conventional fixed reference frames.

• Journal of Power Electronics
• /
• 제18권6호
• /
• pp.1819-1829
• /
• 2018

A three-phase, three-switch, and three-level boost-type PWM rectifier (Vienna rectifier) is proposed as an active front-end power factor correction (PFC) rectifier for telecom loads. The proposed active front-end PFC rectifier system is modeled by the switching cycle average model. The relation between duty ratios and DC link capacitor voltages is derived in terms of the system input currents. Furthermore, the feasible switching states are identified and applied to the proposed system to reduce the switching stress and DC ripples. A detailed equivalent circuit analysis of the proposed front-end PFC rectifier is conducted, and its performance is verified through simulations in MATLAB. Simulation results are verified using an experimental setup of an active front-end PFC rectifier that was developed in the laboratory. Simulation and experimental results demonstrate the improved power quality parameters that are in accordance with the IEEE and IEC standards.