• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.560-573
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• 2015

In this paper, a battery charger is introduced for an interleaved DC-DC converter with an LCLC filter. To improve the overall performance of the DC-DC converter for battery charger, a method is proposed. First, the structure of the system is presented. Second, an LC filter is compared to an LCLC filter in terms of the response characteristics and size. Third, the small-signal model of a bidirectional DC-DC converter using a state-space averaging method and the required transfer functions are introduced. Next, the frequency characteristics of the converter are discussed. Finally, the simulation and experimental results are analyzed to verify the proposed state space of the bidirectional converter.

• 한국유체기계학회 논문집
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• 제16권4호
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• pp.35-43
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• 2013

Most of the nuclear power plants(NPPs) adopts pressure difference type flow meters such as venturi and orifice meters for the measurement of feedwater flow rates to calculate reactor thermal power. However, corrosion products in the feedwater deposits on the flow meter by fouling as operating time goes. These effects lead to severe errors in the flow indication and then determination of reactor thermal power. The averaging BDFT, which has developed by Yun et al., has a potentiality to minimize this problem thanks to its inherent measurement principle. Therefore, it is expected that the averaging BDFT can replace the venturi meter for the feedwater pipe of steam generator of NPPs. The present work compares the amplification factor, K, based on CFD calculation against the K obtained from experiments in order to confirm whether a commercial CFD code can be applicable to the evaluation of characteristic for the averaging BDFT. In addition to this, the simulations to take into account of fouling effect are also carried out by rough wall option. The results show that the averaging BDFT is a promising flow meter for the accurate measurement of flow rates in the fouling condition of the NPPs.

• 전기전자학회논문지
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• 제26권2호
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• pp.287-291
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• 2022

일반적으로 V2X 통신은 차량의 고속이동에 따라 물리계층 채널 임펄스 응답의 진폭과 위상정보가 시간 및 주파수에서 빠르게 변화하기 때문에, 수신단에서 이러한 채널을 정확하게 추정하는 것이 매우 어려운 일이다. 이러한 문제를 효과적으로 극복하기 위해 최근 패킷 내부에 주기적으로 미드앰블을 삽입하는 미드앰블 기반 채널추정 방식이 고려되고 있다. 하지만 단순히 미드앰블을 삽입하는 방법은 미드앰블의 수가 증가할수록 성능 이득 대비 주파수 효율이 빠르게 감소하는 문제점을 가지고 있다. 본 논문에서는 이러한 문제점을 해결하기 위해 기존의 데이터 파일럿 기반 채널추정방법과 미드앰블 방법을 결합한 새로운 양방향 평균화 채널추정기법을 제안한다. 제안하는 기법은 이러한 평균화 과정과 미드앰블의 위치 최적화를 통해 보다 적은 수의 미드앰블로 채널 추정의 정확도를 비약적으로 향상시킬 수 있다. 마지막으로 미드앰블의 수에 따른 패킷오류율 시뮬레이션을 통해 주파수 효율 관점에서 제안하는 기법의 우수성을 입증한다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 The Third Asian Fuzzy Systems Symposium
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• pp.579-584
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• 1998

In this work, we present a method to deal with the interval valued decision making systems. First, we propose a new type of equality measure based on the Ordered Weighted Averaging (OWA) operator. The proposed equality measure has a structure to render the extreme values of the measure by choosing a suitable weighting vector of the OWA operator. From this property, we derive a bidirectional fuzzy inference network which can be applied for the decisionmaking systems requiring the inverval valued decisions.

• 전자공학회논문지C
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• 제34C권10호
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• pp.98-105
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• 1997

In this work, we proesent a bidirectional approximate reasoning method and fuzzy inference network for interval valued decision making systems. For this, we propose a new type of similarity measure between two fuzzy vectors based on the Ordered Weighted Averaging (OWA) operator. Since the proposed similarity measure has a structure to give the extreme values by choosing a suitable weighting vector of the OWA operator, it can render an interval valued similarity value. From this property, we derive a bidirectional approximate reasoning method based on the similarity measure and show its fuzzy inference network implementation for the decision making systems requiring the interval valued decisions.

• 전력전자학회논문지
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• 제19권5호
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• pp.422-430
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• 2014

This study proposes a small-signal model and control design for a two-stage DC-DC-AC converter to investigate its dynamic characteristics in relation to battery energy storage system. When the circuit analysis of the two-stage DC-DC-AC converter is attempted simultaneously, the mathematical procedure of deriving the dynamic equation is complex and difficult. The main idea of modeling the two-stage DC-DC-AC converter states that this topology is separated into a bidirectional DC-DC converter and a single-phase inverter with an equivalent current source corresponding to that of the inverter or converter. The dynamic equations for the separated converter and inverter are then derived using the state-space averaging technique. The procedures of building the small-signal model of the two-stage DC-DC-AC converter are described in detail. Based on the derived small-signal model, the individual controllers are designed through a frequency-domain analysis. The simulation and experimental results verify the validity of the proposed modeling approach and controller design.