• Journal of Power Electronics
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• 제15권6호
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• pp.1429-1437
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• 2015

A new parallel hybrid soft switching converter with low circulating current losses during the freewheeling state and a low output current ripple is presented in this paper. Two circuit modules are connected in parallel using the interleaved pulse-width modulation scheme to provide more power to the output load and to reduce the output current ripple. Each circuit module includes a three-level converter and a half-bridge converter sharing the same lagging-leg switches. A resonant capacitor is adopted on the primary side of the three-level converter to reduce the circulating current to zero in the freewheeling state. Thus, the high circulating current loss in conventional three-level converters is alleviated. A half-bridge converter is adopted to extend the ZVS range. Therefore, the lagging-leg switches can be turned on under zero voltage switching from light load to full load conditions. The secondary windings of the two converters are connected in series so that the rectified voltage is positive instead of zero during the freewheeling interval. Hence, the output inductance of the three-level converter can be reduced. The circuit configuration, operation principles and circuit characteristics are presented in detail. Experiments based on a 1920W prototype are provided to verify the effectiveness of the proposed converter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.46-48
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• 2008

A concern about micro grid connection system is elevated. The reason is that carbon dioxide emission is regionally restricted to prevent the drain of fossil fuel, high oil prices and global warming. The existing photovoltaic DC-DC converter is operated by the full-bridge method. However, the configuration is complicated because a phase shift method is required to raise an efficiency. A photovoltaic DC-DC converter connected with second layered half-bridge converter and boost converter is proposed in this paper. This proposed DC-DC converter is easy to control and has an advantage of reducing the size. Finally, the validity of the proposed converter is verified by the experimentation.

• 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.

• Smart Structures and Systems
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• 제10권3호
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• pp.209-228
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• 2012

Structural health monitoring with wireless sensor networks has received much attention in recent years due to the ease of sensor installation and low deployment and maintenance costs. However, sensor network technology needs to solve numerous challenges in order to substitute conventional systems: large amounts of data, remote configuration of measurement parameters, on-site calibration of sensors and robust networking functionality for long-term deployments. We present a structural health monitoring network that addresses these challenges and is used in several deployments for monitoring of bridges and buildings. Our system supports a diverse set of sensors, a library of highly optimized processing algorithms and a lightweight solution to support a wide range of network runtime configurations. This allows flexible partitioning of the application between the sensor network and the backend software. We present an analysis of this partitioning and evaluate the performance of our system in three experimental network deployments on civil structures.

• Computers and Concrete
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• 제21권4호
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• pp.471-484
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• 2018

Refined analysis depicting mass transportation and physicochemical reaction and reasonable computing load with acceptable DOFs are the two major challenges of numerical simulation for concrete durability. Mesoscopic numerical simulation for chloride diffusion considering binder, aggregate and interfacial transition zone is unable to be expended to the full structure due to huge number of DOFs. In this paper, a multiscale approach of combining both mesoscopic model including full-graded aggregate and equivalent macroscopic model was introduced. An equivalent conversion of chloride content at the Interfacial Transition Layer (ITL) connecting both models was considered. Feasibility and relative error were discussed by analytical deduction and numerical simulation. Case study clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Difference for single-scale simulation and multiscale approach was observed. Finally, this paper addressed some worth-noting conclusions about the chloride distribution and rebar corrosion regarding the configuration of rebar placement, rebar diameter, concrete cover and exposure period.

• 한국정보통신학회논문지
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• 제13권6호
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• pp.1077-1082
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• 2009

무선 메쉬 네트워크는 네트워크 구성의 용이성과 비용적인 장점으로 각광받고 있는 무선 백본 네트워크 기술이다. 최근 상용화된 제품이 출시되고 있지만, 대부분의 기존 연구 기술은 시뮬레이션을 통해 성능을 분석하였다. 본 논문에서는 실제 상황을 고려하여 무선 메쉬 네트워크 테스트베드를 구축하였다. 본 테스트 베드는 무선 분산 시스템(Wireless Distribution System)과 브릿지를 응용하여 멀티채널 멀티 인터페이스와 동적인 위치기반 라우팅 프로토콜을 지원한다. 위치기반 라우팅 프로토콜은 링크 채널 변화와 물리적 거리를 고려한 메트릭을 이용하여 무선 간섭에 강하게 설계하였다. 그리고 메쉬 클라이언트들은 중앙 집중 주소 관리 서버를 통해 주소를 할당 받아 통신하며, 간이 망 네트워크 관리 프로토콜을 통해 망을 관리하도록 설계 및 구현하였다.

• Journal of Power Electronics
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• 제11권4호
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• pp.591-598
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• 2011

This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torches. A series resonant half-bridge topology is presented as a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. A plasma torch rated at 3MW, 2kA and having a physical size of 1m is selected to be the high enthalpy source for a waste disposal system. The steady-state and transient operations of a plasma torch are simulated. The parameters of a Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. The circuit simulation waveform shows that the ripple of the arc current can be maintained within ${\pm}10%$ of its rated value under the presence of a load disturbance. This power conversion configuration provides a high enough ignition voltage, around 5KA, during the ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.

• 전력전자학회논문지
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• 제15권5호
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• pp.376-380
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• 2010

본 논문에서는 양방향 스위치를 가지는 기존의 5-레벨 인버터를 직렬 결합하여 다수의 출력 전압 레벨을 형성할 수 있는 멀티레벨 인버터 구조를 제안한다. 무엇보다도 제안된 회로의 입력 전압원 크기를 5의 배수로 구성함으로서 보다 많은 수의 레벨을 생성시킬 수 있다. 동일한 수의 출력 전압 레벨 형성시 기존의 Cascaded H-bridge cell 방식보다 스위칭 소자를 줄일 수 있어 시스템 크기, 비용, 전력 손실을 저감시킬 수 있는 장점을 가진다. 두 대의 5-레벨 인버터를 직렬 결합함으로써 25-레벨의 출력전압을 생성시킬 수 있는 인버터에 대한 특성을 분석하고 시뮬레이션과 실험을 통해 타당성을 검증한다.

• 조명전기설비학회논문지
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• 제14권2호
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• pp.52-58
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• 2000

본 논문애서는 2단 스위치 구조를 가져는 역률 보상 회로를 적용하여 도통 손실을 저감할 수 있는 새로운 결합형 1단방식 AC/DC half-bridge 컨버터에 대한 토폴라지를 제안하고, 이에 관한 전류 불연속 모드 제어와 소프트 스위칭 특성에 대하여 연구하였다. 도통손실의 저감은 기존의 역률 보상 회로 대신 새로운 형태의 이단 스위치 구조를 가지는 역률 보상 회로를 적용함으로써 이루어친다. 제안된 토폴라지의 타당성 검증을 위해서 입력전압 100[V], 출력전압 50[V]의 500[W]급 컨버터에 대한 시뮬레이션 결과를 제시하고 분석하였다.

• 전력전자학회논문지
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• 제20권4호
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• pp.321-329
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• 2015

The static synchronous compensator (STATCOM) of cascaded H-bridge configuration accompanying multiple separate DC sides is inherently subject to the problem of uneven DC voltages. These DC voltages in one leg can be controlled by adjusting the AC-side output voltage of each cell inverter, which is proportional to the active power. However, when the phase current is extremely small, large AC-side voltage is required to generate the active power to balance the cell voltages. In this study, an alternative zero-sequence current injection method is proposed, which facilitates effective cell balancing controllers at no load, and has no effect on the power grid because the injected zero sequence current only flows within the STATCOM delta circuit. The performance of the proposed method is verified through simulation and experiments.