• 조명전기설비학회논문지
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• 제29권1호
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• pp.80-85
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• 2015

In the issues of interleaved topology which have been in limelight as high power converter, various soft-switching methods are studied to reduce switching losses in high power application. The interleaved ZCT converter has an additional filter inductor to reduce losses of diodes during reverse recovery process. However, additional current conduction modes are occurred by the inductor, we need to analyze switching losses with inductor values on each mode. In this paper, current conduction modes and boundary conditions of interleaved ZCT converter are analyzed. In the conclusion, the minimum of switching losses in converter operation modes is analyzed by calculating switching losses.

• 시스템엔지니어링학술지
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• 제1권2호
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• pp.43-48
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• 2005

This paper describes the results of applying States and Modes Analysis, one of the requirements analysis techniques, to the development requirements of flight control software for Smart UAV. State/mode table enabled us to investigate various operation and design concepts, and as a result essential requirements for flight control software were established without omitting necessary requirements. Through the use of scenario-specific state transition diagrams, dynamic behaviours and control/response interfaces between each state and mode could been clearly identified, which made it possible to establish requirements related to dynamic behaviours of states and modes which are essential to the design of flight control software.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.114-120
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• 2000

Friction forces of piston rings for a typical SI engine were independently measured while excluding the effects of cylinder pressure, oil starvation and piston secondary motion using a floating liner system. Friction patterns, represented by the measured friction forces, were classified into five frictional modes with regard to the combination of predominant lubrication regimes(boundary, mixed and hydrodynamic lubrication) and stroke regions(mid-stroke and dead centers). The modes were identified on the Stribeck diagram of the dimensionless bearing parameter and friction coefficients which were evaluated at the mid-stroke and at the dead centers. And the frictional modes were estimated to the full operation range. The compression rings behave in the mode where hydrodynamic lubrication is dominant at the mid-stroke and mixed lubrication is dominant at the dead centers under steady operating conditions. However, the oil control ring behave in the mode where mixed lubrication is dominant throughout the entire stroke.

• 전기학회논문지
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• 제67권2호
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• pp.224-232
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• 2018

According to government policy, renewable energy facility such as solar power generation is being implemented for newly constructed buildings. In recent years, the introduction of Energy Storage System (ESS) served as an emergency power for replacing an existing diesel generator has been increasing. Furthermore, in order to expand the efficacy of the ESS operation, operation in combination with renewable energy sources such as solar and wind power generation is increasing. Hence, development of the ESS operation algorithms for emergency mode as well as the peak power cut mode, which is the essential feature of ESS, are necessary. The operational scenarios of ESS need to consider load power requirement and the amount of the power generation by renewable energy sources. For the verification of the developed scenarios, tests under the actual situation are demanded, but there is a difficulty in simulating the emergency operation situation such as system failure in the actual site. Therefore, this paper proposes simulation models for the HILS(Hardware In the Loop Simulation) and operation modes developed through HILS for the ESS operated with renewable energy source under peak power reduction and emergency modes. The paper shows that the ESS operation scenarios developed through HILS work properly at the actual site, and it verifies the effectiveness of the control logic developed by the HILS.

• 한국정보통신학회논문지
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• 제16권4호
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• pp.771-777
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• 2012

본 논문에서는 공통 연산기(Common Operation Unit)를 이용한 CABAC의 이진 산술 부호화기를 제안한다. 제안한 공통 연산기는 모드에 상관없이 하나의 공통 연산기를 이용하여 산술 부호화 및 재정규화를 수행하는 이진 산술 부호화기의 하드웨어 구조를 단순하게 구현할 수 있다. 제안하는 CABAC의 이진 산술 부호화기는 Context RAM, Context Updater, Common Operation Unit, Bit-Gen으로 구성되며 매 클럭당 하나의 심볼이 부호화될 수 있는 4단 파이프라인으로 구성하였다. 제안한 CABAC의 이진 산술 부호화기는 기존 CABAC의 이진 산술 부호화기와 비교하여 게이트 수는 최대 47% 감소하였고, 동작 주파수는 최대 19% 성능이 향상됨을 확인하였다.

• 대한기계학회논문집B
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• 제30권3호
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• pp.193-200
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• 2006

The purpose of this study is to compare the part-load performance of a SOFC/GT hybrid power system with three different kinds of load-following operation modes. The primary mode for the part load operation of a hybrid power system is the reduction of supplied fuel (e.g., fuel control mode) to the hybrid system. The other two options, i.e., variable speed and VIGV controls, are related to the reduction of supplied air simultaneously with the reduction of supplied fuel to the system. With the performance analysis of a SOFC/GT hybrid power system, it is concluded that the variable speed con佐ol mode Provides the best performance for the part-load operations. It is also found that the VIGV control mode, with its better performance behavior than the fuel control mode, can be used as an important option for the part-load operation especially in case that the variable speed control mode can not be adopted.

• 전기전자학회논문지
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• 제25권1호
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• pp.218-228
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• 2021

본 논문에서는 다중공진회로를 이용한 고효율 DC-DC 컨버터를 제안한다. 제안한 컨버터는 하프브리지 전력구조이며 컨버터의 고효율화를 위해 2개의 인덕터(LL)와 1개의 커패시터(C)로 구성된 다중공진회로를 이용한다. 이 다중공진회로는 동작모드에 따라, 각각의 공진주파수를 가진 직렬회로 형태의 공진회로를 각각 형성한다. 본 논문에서는 먼저, 동작모드와 정상상태 기본파 근사 모델링에 의해 제안한 컨버터의 동작원리를 설명한다. 그다음 이에 근거하여 제안한 컨버터의 설계예시를 보인다. 그리고 설계된 회로 파라미터에 의해 제작된 프로토타입 컨버터의 실험결과를 통하여 제안한 컨버터의 고효율 DC-DC 전력변환 동작특성을 입증한다.

• 전기학회논문지
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• 제64권11호
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• pp.1618-1625
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• 2015

The reliability of catenary system is very important for uninterrupted train operation as it supplies electric power to train without redundant facilities. This paper provides a systematic approach to the reliability analysis of the catenary system based on FMECA procedures defined by global standards such as MIL Std 1692a and IEC 60812. Field failure data collected from the operation and maintenance of high-speed railway catenary system for 9 years are used to derive critical failure modes and to evaluate the criticality of the failure modes. Evaluation of the criticality are carried out by quantitative procedures defined by MIL Std 1692a and by criticality matrix defined by IEC 60812. FMECA results suggests that three critical failure modes should be checked carefully during maintenance work, which include strand break of dropper and voltage equalizing wire, power supply failure of feeder. Maintenance procedure of catenary system in order of importance is suggested too. These results can be applied to maintenance planning and design of catenary system to improve the reliability of electric railway system.

• Journal of Power Electronics
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• 제17권3호
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• pp.744-755
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• 2017

With the high penetration of various sustainable energy sources, the control and protection of Microgrids has become a challenging problem considering the inherent current limitation feature of inverter-based Distributed Generators (DGs) and the bidirectional power flow in Microgrids. In this paper, a hybrid control and protection scheme is proposed, which combines the traditional inverse-time overcurrent protection with the biased differential protection for different feeders with different kinds of loads. It naturally accommodates various control strategies such as P-Q control and V-f control. The parameter settings of the protection scheme are analyzed and calculated through a fast Fourier transform algorithm, and the stability of the control strategy is discussed by building a small signal model in MATLAB. Different operation modes such as the grid-connected mode, the islanding mode, and the transitions between these two modes are ensured. A Microgrid model is established in PSCAD and the analysis results show that a Microgrid system can be effectively protected against different faults such as the single phase to ground and the three phase faults in both the grid-connected and islanded operation modes.

• 정보보호학회논문지
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• 제11권4호
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• pp.55-66
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• 2001

본 논문에서는 블록 암호의 기본적인 동작 모드 중의 하나인 OFB 암호화 모드와 비동기식 IMT-2000의 무선 구간 메시지 암호화를 위해 사용되는 3GPP f8 암호화 모드의 안전성을 분석한다. Left-or-right 안전성 개념을 적용하여 각각 랜덤 함수 모델과 랜덤 치환 모델에서의 안전성에 대한 하한과 상한을 증명하고, 또한 유사랜덤 함수 모델과 유사 랜덤 치환 모델에서의 안전성을 각각 증명한다.