• 제목/요약/키워드: low loss

검색결과 5,122건 처리시간 0.033초

ATM 망에서 공평한 지연 및 손실 우선순위 제어 (Fair delay and loss priority control in ATM networks)

  • 박창욱;임인칠
    • 전자공학회논문지A
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    • 제33A권6호
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    • pp.23-32
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    • 1996
  • This paper proposes a new buffer management scheme to service delay-sensitive traffic and loss-sensitive traffic fairly in ATM networks. The proposed scheme uses tow buffers for delay-sensitive traffic and loss-sensitive traffic. To satisfy the average delay time of delay-sensitive traffic, cells in real-time buffer are served first. When congestion occurs in nonreal-time buffer, low loss priority cell in real-time buffer can be pushed out by high loss priority cell in nonreal-time buffer can be transferred to real-time buffer considering threshold value in real-time buffer. Using computer simulation, the existing methods and proposed scheme are compared and analyzed with respect to cell loss rate and average delay time. Simulation results show that the proposed scheme have superior performance to conventional schemes.

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Study of Optimal Location and Compensation Rate of Thyristor-Controlled Series Capacitor Considering Multi-objective Function

  • Shin, Hee-Sang;Cho, Sung-Min;Kim, Jin-Su;Kim, Jae-Chul
    • Journal of Electrical Engineering and Technology
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    • 제8권3호
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    • pp.428-435
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    • 2013
  • Flexible AC Transmission System (FACTS) application study on enhancing the flexibility of AC power system has continued to make progress. A thyristor-controlled series capacitor (TCSC) is a useful FACTS device that can control the power flow by adjusting line impedances and minimize the loss of power flow and voltage drop in a transmission system by adjusting line impedances. Reduced power flow loss leads to increased loadability, low system loss, and improved stability of the power system. This study proposes the optimal location and compensation rate method for TCSCs, by considering both the power system loss and voltage drop of transmission systems. The proposed method applies a multi-objective function consisting of a minimizing function for power flow loss and voltage drop. The effectiveness of the proposed method is demonstrated using IEEE 14- and a 30-bus system.

모델 기반의 풍력발전용 유도발전기의 최소 손실 제어 (Model-Based Loss Minimization Control for Induction Generators - in Wind Power Generation Systems)

  • 아보칼릴 아메드;이동춘
    • 대한전기학회논문지:전기기기및에너지변환시스템부문B
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    • 제55권7호
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    • pp.380-388
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    • 2006
  • In this paper, a novel control algorithm to minimize the power loss of the induction generator for wind power generation system is presented. The proposed method is based on the flux level reduction, where the flux level is computed from the machine model for the optimum d-axis current of the generator. For the vector-controlled induction generator, the d-axis current controls the excitation level in order to minimize the generator loss while the q-axis current controls the generator torque, by which the speed of the induction generator is controlled according to the variation of the wind speed in order to produce the maximum output power. Wind turbine simulator has been implemented in laboratory to validate the theoretical development. The experimental results show that the loss minimization process is more effective at low wind speed and that the percent of power loss saving can approach to 25%. Experimental results are shown to verify the validity of the proposed scheme.

휴리스틱 탐색전략을 이용한 배전계통 계획의 급전선 최적 경로 선정 (Optimal Feeder Routing for Distribution System Planning Using a Heuristic Strategy)

  • 최남진;김병섭;신중린
    • 대한전기학회논문지:전력기술부문A
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    • 제49권11호
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    • pp.566-574
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    • 2000
  • This paper propose a heuristic algorithm based on the Branch-Exchange (BE) method to solve Optimal feeder Routing(OFR) problem for the distribution system planning. The cost function of the OFR problem is consisted of the investment cost representing the feeder installation and the system operation cost representing the system power loss. We propose a properly designed heuristic strategy, which can handle the horizon-year expansion planning problem of power distribution network. We also used the loop selection method which can define the maximum loss reduction in the network to reduce calculation time, and proposed a new index of power loss which is designed to estimate the power loss reduction in the BE. The proposed index, can be considered with both sides, the low voltage side and voltage side branch connected with tie one. The performances of the proposed algorithms and loss index were shown with 32, 69 example bus system.

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가변 임계값을 갖는 푸쉬 아웃 기법을 이용한 트래픽 제어 (A Study on Buffer Processing using Push Out Scheme with Variable Threshold)

  • 최인수;박호균;류황빈
    • 한국통신학회논문지
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    • 제18권12호
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    • pp.1884-1892
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    • 1993
  • 푸쉬 아웃 기법은 버퍼가 찼을때 도착되는 높은 우선 순위의 셀에 의해 낮은 우선 순위의 셀을 밀어내는 방법이며, PBS기법은 버퍼에 가변적인 임계값을 두어 우선순위를 제공하는 기법이다. 본 연구에서는 ATM망에서의 과밀 현상을 제어하기 위하여 푸쉬 아웃 기법에 가변적인 임계값을 두어 버퍼 처리 기법을 제안하였으며, 이를 성능 분석하였다. 시뮬레이션 결과, 제안된 가변적인 임계값을 갖는 푸시 아웃기법이 기존의 푸쉬아웃 기법과 PBS 기법에 비해 낮은 우선 순위의 셀 손실이 감소되었다. 따라서, 제안된 이 기법은 기존의 푸쉬아웃 기법과 같이 높은 우선 순위위 셀 손실을 줄일 뿐만 하니라 임계값을 가변시킴으로서 낮은 우선 순위의 셀 손실도 감소시킬 수 있었다.

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태양광 발전을 위한 대용량 소프트 스위칭 승강압 DC-DC 컨버터 (High Power Buck-boost DC-DC Converter of Soft Switching for Photovoltaic Power Generation)

  • 김영철;김재준;이종근;전중함;곽동걸;이현우
    • 전력전자학회:학술대회논문집
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    • 전력전자학회 1996년도 창립기념 전력전자학술발표회 논문집
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    • pp.117-120
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    • 1996
  • Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. In this paper, the authors propose a DC-DC boost converter of high power by partial resonant switch method (PRSM). The switching devices in a proposed circuit are operated with soft switching and the control technique of those is simplified for switch to drive in constant duty cycle. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. Also the circuit has a merit which is taken to increase of efficiency, as it makes to a regeneration at input source of accumulated energy in snubber condenser without loss of snubber in conventional circuit. The result is that the switching loss is very low and the efficiency of system is high. The proposed converter is deemed the most suitable for high power applications where the power switching devices are used.

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Highly Efficient AC-DC Converter for Small Wind Power Generators

  • Ryu, Hyung-Min
    • Journal of Power Electronics
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    • 제11권2호
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    • pp.188-193
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    • 2011
  • A highly efficient AC-DC converter for small wind power generation systems using a brushless DC generator (BLDCG) is presented in this paper. The market standard AC-DC converter for a BLDCG consists of a three-phase diode rectifier and a boost DC-DC converter, which has an IGBT and a fast recovery diode (FRD). This kind of two-stage solution basically suffers from a large amount of conduction loss and the efficiency greatly decreases under a light load, or at a low current, because of the switching devices with a P-N junction. In order to overcome this low efficiency, especially at a low current, a three-phase bridgcless converter consisting of three upper side FRDs and three lower side Super Junction FETs is presented. In the overall operating speed region, including the cut-in speed, the efficiency of the proposed converter is improved by up to 99%. Such a remarkable result is validated and compared with conventional solutions by calculating the power loss based on I-V curves and the switching loss data of the adopted commercial switches and the current waveforms obtained through PSIM simulations.

Energy efficiency strategy for a general real-time wireless sensor platform

  • Chen, ZhiCong
    • Smart Structures and Systems
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    • 제14권4호
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    • pp.617-641
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    • 2014
  • The energy constraint is still a common issue for the practical application of wireless sensors, since they are usually powered by batteries which limit their lifetime. In this paper, a practical compound energy efficiency strategy is proposed and realized in the implementation of a real time wireless sensor platform. The platform is intended for wireless structural monitoring applications and consists of three parts, wireless sensing unit, base station and data acquisition and configuration software running in a computer within the Matlab environment. The high energy efficiency of the wireless sensor platform is achieved by a proposed adaptive radio transmission power control algorithm, and some straightforward methods, including adopting low power ICs and high efficient power management circuits, low duty cycle radio polling and switching off radio between two adjacent data packets' transmission. The adaptive transmission power control algorithm is based on the statistical average of the path loss estimations using a moving average filter. The algorithm is implemented in the wireless node and relies on the received signal strength feedback piggybacked in the ACK packet from the base station node to estimate the path loss. Therefore, it does not need any control packet overheads. Several experiments are carried out to investigate the link quality of radio channels, validate and evaluate the proposed adaptive transmission power control algorithm, including static and dynamic experiments.

낮은 삽입손실을 갖는 소형 이중모드 공진기와 스위치 기능을 가진 여파기로의 응용 (Compact and Low Insertion Loss Dual-Mode Resonator and Its Applications for Switchable Filters)

  • 성영제;김보연;이건준;김영식
    • 한국전자파학회논문지
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    • 제15권3호
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    • pp.301-310
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    • 2004
  • 본 논문에서는 마이크로스트립 공진기에 엇갈린 슬롯과 한 쌍의 spur-line을 삽입한 소형 이중모드(dual-mode)여파기를 제안하였다. 제안한 여파기는 급전선과 공진기 사이에 존재하는 급전 갭(coupling gap)을 없앰으로써 삽입손실의 특성이 향상되었다. 엇갈린 슬롯만 가진 기존의 이중모드 여파기와 비교할 때, 엇갈린 슬롯과 spur-line을 동시에 갖는 이중모드 여파기는 이중모드 특성을 나타내는 섭동의 범위가 상당히 넓기 때문에 이중 모드 여파기의 설계가 용이해졌다. 또한, 제안된 구조의 가장자리에 존재하는 spur-line에 2개의 PIN다이오드를 삽입하여 개폐기 특성을 갖는 여파기로의 응용도 가능하였다. 또한 제안한 구조는 공진기에 삽입된 슬롯과 spur-line에 의해 전기적인 길이가 길어지므로 기존의 구조에 비해 34.7 %의 크기 감소 효과를 얻을 수 있었다.

50 kVA 주상용 몰드변압기의 설계 및 특성평가 (The Design and Performance Test of Mold Transformer for Outdoor Pole)

  • 조한구;이운용;황보국
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
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    • pp.132-137
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    • 2002
  • The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and low loss. The life of transformer is significantly dependent on the thermal behavior in windings. To analyse winding temperature rise, many transformer designer have calculated temperature distribution and hot spot point by finite element method(FEM). Recently, numerical analyses of transformer are studied for optimum design, that is electric field analysis, magnetic field, potential vibration, thermal distribution and thermal stress. In this paper, the temperature distribution of 50 kVA pole mold transformer for power distribution are investigated by FEM program and the temperature rise test of designed mold transformer carried out and test result is analyzed compare to simulation data. In this result, the designed mold transformer is satisfied to limit value of temperature and the other property is good such as voltage ratio, winding resistance, no-load loss, load loss, impedance voltage and percent regulation.

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