• 대한전기학회논문지:전력기술부문A
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• 제55권1호
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• pp.13-17
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• 2006

In this paper, the RCF(Resistive Companion Form) analysis method which is used to analyze small signal stability problems of non-continuous systems including switching devices. The RCF analysis method is mathematically rigorous and computes eigenvalue of the system periodic transition matrix based on discrete system analysis method. As an effect of switching operations, the eigenvalues of the systems are changed and newly unstable oscillation modes may be occurred. As an illustrating example, the oscillation modes of the system with different switching time intervals are computed exactly by the RCF analysis method and the results show that ON/OFF time intervals of switching equipments are important factors to make the system stable or unstable. This result shows that the RCF analysis method is very powerful to analyze small signal stability problems of power systems including switching devices such as FACTS equipments.

• Journal of Power Electronics
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• 제5권3호
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• pp.233-239
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• 2005

In this paper, a new conceptual circuit configuration of a 3-phase voltage source, soft switching AC-DC-AC converter using an IGBT module, which has one ARCPL circuit and one ARDCL circuit, is presented. In actuality, the ARCPL circuit is applied in the 3-phase voltage source rectifier side, and the ARDCL circuit is in the inverter side. And more, each power semiconductor device has a novel clamp snubber circuit, which can save the power semiconductor device from voltage and current across each power device. The proposed soft switching circuits have only two active power semiconductor devices. These ARCPL and ARDCL circuits consist of fewer parts than the conventional soft switching circuit. Furthermore, the proposed 3-phase voltage source soft switching AC-DC-AC power conversion system needs no additional sensor for complete soft switching as compared with the conventional 3-phase voltage source AC-DC-AC power conversion system. In addition to this, these soft switching circuits operate only once in one sampling term. Therefore, the power conversion efficiency of the proposed AC-DC-AC converter system will get higher than a conventional soft switching converter system because of the reduced ARCPL and ARDCL circuit losses. The operation timing and terms for ARDCL and ARCPL circuits are calculated and controlled by the smoothing DC capacitor voltage and the output AC current. Using this control, the loss of the soft switching circuits are reduced owing to reduced resonant inductor current in ARCPL and ARDCL circuits as compared with the conventional controlled soft switching power conversion system. The operating performances of proposed soft switching AC-DC-AC converter treated here are evaluated on the basis of experimental results in a 50kVA setup in this paper. As a result of experiment on the 50kVA system, it was confirmed that the proposed circuit could reduce conduction noise below 10 MHz and improve the conversion efficiency from 88. 5% to 90.5%, when compared with the hard switching circuit.

• Journal of Power Electronics
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• 제10권4호
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• pp.335-341
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• 2010

In this paper, an interleaved soft switching boost converter for a Photovoltaic Power Conditioning System (PV-PCS) with high efficiency is proposed. In order to raise the efficiency of the proposed converter, a 2-phase interleaved boost converter integrated with soft switching cells is used. All of the switching devices in the proposed converter achieve zero current switching (ZCS) or zero voltage switching (ZVS). Thus, the proposed circuit has a high efficiency characteristic due to low switching losses. To analyze the power losses of the proposed converter, two experimental sets have been built. One consists of normal devices (MOSFETs, Fast Recovery (FR) diodes) and the other consists of advanced power devices (CoolMOSs, SiC-Schottky Barrier Diodes (SBDs)). To verify the validity of the proposed topology, theoretical analysis and experimental results are presented.

• 전력전자학회논문지
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• 제16권5호
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• pp.477-483
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• 2011

일반적인 DC/DC 전력변환기의 스위칭 방식은 하드 스위칭 방식과 공진을 이용한 소프트 스위칭 방식으로 분류할 수 있으며, 하드 스위칭 방식은 스위치의 턴 온/오프시 스위칭 소자에 생기는 전력손실이 커서 효율 면에서 불리하며, 공진형 소프트 스위칭 방식은 별도의 리액터와 커패시터를 추가함으로서 시스템의 사이즈와 비용이 증가하는 단점이 있다. 본 논문에서는 이러한 단점을 극복하기 위해 새로운 스위칭 방식의 소프트 스위칭 방식의 Full-bridge 전력변환기의 구조를 제안하였으며, 제안된 소프트 스위칭 방식은 앞단의 벅 컨버터의 다이오드 전류시 영전압이 되는 구간에서 Full-Bridge 컨버터의 스위치를 교변 함으로써 리액터와 커패시터의 추가없이 소프트 스위칭을 이루어냄으로서 시스템의 효율과 신뢰성을 향상시킨다. 또한 제안된 절연형 소프트 Full-bridge DC/DC 컨버터의 타당성을 검증하기 위해 Psim을 이용한 시뮬레이션과 500[W]급 DC/DC 컨버터를 제작하여 DC/DC 컨버터의 효율이 우수함을 확인하였다.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권4호
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• pp.465-471
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• 2014

This paper proposes a new switching algorithm for an active clamp snubber to improve the efficiency of a module integrated converter system. This system uses an active clamp method for the snubber circuit for the efficiency and reliability of the system. However, the active clamp snubber circuit has the disadvantage that system efficiency is decreased by switch operating time because of heat loss in resonance between the snubber capacitor and leakage inductance. To address this, this paper proposes a new switching algorithm. The proposed algorithm is a technique to reduce power consumption by reducing the resonance of the snubber switch operation time. Also, the snubber switch is operated at zero voltage switching by turning on the snubber switch before main switch turn-off. Simulation and experimental results are presented to show the validity of the proposed new active clamp control algorithm.

• 한국정보시스템학회지:정보시스템연구
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• 제30권3호
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• pp.65-91
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• 2021

Purpose In this study, we investigated the impact of perceived risk and switching costs on switching intention to cloud service based on PPM (Pull-Push-Mooring) model. Design/methodology/approach We focused on revealing the switching factors of the switching intention to the cloud services. The switching factors to the cloud services were defined as perceived risk consisting of performance risk, economic risk, and security risk, and switching costs consisting of financial and learning costs. On the PPM model, we defined the pull factors consisting of perceived usefulness and perceived ease of use, and the push factor as satisfaction of the legacy system, and the mooring factor as policy supports. Findings The results of this study as follows; (1) Among the perceived risk factors, performance risk has a negative effect on the ease of use of pull factors, and finally it was found to affect the switching intention to the cloud services. Therefore, cloud service providers need to improve trust in cloud services, service timeliness, and linkage to the legacy systems. And it was found that economic risk and security risk among the perceived risk factors did not affect the switching intention to the cloud services. (2) Of the perceived risk factors, financial cost and learning cost did not affect the satisfaction of the legacy system, which is a push factor. It indicates that the respondents are positively considering switching to cloud service in the future, despite the fact that the respondents are satisfied with the use of the legacy system and are aware of the switching cost to cloud service. (3) Policy support was found to improve the switching intention to cloud services by alleviating the financial and learning costs required for cloud service switching.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.723-726
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• 2000

In this paper, we present an abstract object-oriented plat-form model .suitable for the real-time distributed telecommunication system. The proposed platform is constructed upon the extended version of the real-time, distributed operating system, SROS(Scalable Real-time Operating System), that is developed at ETRI and successfully operated in the ATM switching system for several years. The object-oriented software development and maintenance methodology will resolve the current software crisis in the area of telecommunication and switching systems due to the everlasting maintenance about the huge amount of the existing software and the ever increasing needs for the better and new communication services. In general, an object-oriented software platform realizes the object-oriented methodology and possesses many good aspects like high productivity, better reusability, easy maintenance, et at. The platform is also designed to present the distributed multimedia service in addition to real-time event delivery. Recently, we have been implementing a couple of prototype bated on the proposed platform. Reflecting the evaluation results from these prototypes, the final platform specification will be determined.

• 전기전자학회논문지
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• 제19권2호
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• pp.260-264
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• 2015

본 논문에서는 부하전류를 감지하여 스위칭 방식과 선형 방식의 레귤레이터를 동작하기 위한 mode selector를 제안한다. 제안된 mode selector는 선형 방식과 스위칭 방식으로의 모드 전환이 가능하며, 경부하 조건에서 낮은 효율을 갖는 스위칭 방식의 레귤레이터의 단점을 보완하고자 제안되었다. 경부하 조건에서는 선형 방식의 레귤레이터로 mode를 전환함으로써 경부하 상태에서도 높은 효율을 제공할 수 있다. 설계한 mode selector는 동부 하이텍의 $0.18{\mu}m$ CMOS 공정을 이용하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.121.4-121
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• 2002

The digital electronic switching system has some problems, when this system processes OAM(Operation, Administration And Maintenance) messages about the fault, the traffic, the account, and the performance, etc. , at the present. Therefore, we studied on Methods that could process OAM messages out of all digital electronic switching systems and, first of all, developed the MGS (Message Gathering System) to be able to accept and process the fault message of OAM messages out of all digital electronic switching systems in real time.

• 한국시뮬레이션학회논문지
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• 제6권2호
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• pp.117-124
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• 1997

A simulation model for the estimation of cutoff connection rate in the asynchronous transfer mode (ATM) switching system under multimedia traffic environments is presented. The simulator is developed by the integration of the AweSim tool with user-written C++ routines that model the internal structures of operational details of the switching system. For the case study, the simulator is applied to the ATM switching system developed by Electronics and Telecommunications Research Institute (ETRI) to compare design alternatives according to the cutoff connection rates.