• Title/Summary/Keyword: Three-phase power system

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Variable Charger of Vehicle using Relay (릴레이를 이용한 차량용 배터리의 가변 충전기)

  • Song, Sung-Geun;Chung, Seung-Tae;Kang, Sung-Gu;Lee, Sang-Hun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.26 no.9
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    • pp.47-56
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    • 2012
  • This research is to develop satiable battery charger with a variety of capacity and voltage specifications of battery. For this, voltage or current were controlled through buck converter which is DC voltage that already received three-phase at primary side and passed bridge rectifier diode. And, it was comprised of full-bridge converter and HFTR for insulation and a square wave AC. The transformer primary side was comprised in series to divide certain charging current and the secondly side was comprised of 6 fixed transformers so that they can generate certain amount of power and various output voltage through relay parallel compound 6 DC Link outputs. To confirm such structure's verification and validity, simulation with PSIM was conducted, and validity of proposed variable charger system was verified through 3kW stack production.

Vector control of an induction motor using extended Kalman filter (확장 칼만필터를 이용한 유도전동기의 벡터제어)

  • Hwang L.H.;Jang E.S.;Nam W.Y.;Ahn I.K.;Cho M.T.;Joo H.J.;Lee C.S.;Na S.K.
    • Proceedings of the KIPE Conference
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    • 2003.07b
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    • pp.803-806
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    • 2003
  • This paper presents a detailed study of the extended Kalman filter for estimating the rotor speed of an IM drive. The general structure of the Kalman filter is reviewed and the various system vectors and matrices are defined. By including the rotor speed as a state variable, the EKF equations are established from a discrete two axis model of the three-phase induction motor using the software MATLAB/Simulink, simulation of the EKF speed estimation algorithm is carried out for an induction motor drive with direct self control. The investigations show that the EKF is capable of tracking the actual rotor speed provided that the elements of the covariance matrices are properly selected.

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Stabilization of Plasma in a Three-Phase AC Plasma Generator (삼상 교류 플라즈마 발생의 안정화)

  • Lee, K.H.;Kim, K.S.;Lee, H.S.;Rim, G.H.
    • Proceedings of the KIEE Conference
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    • 2002.11a
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    • pp.209-211
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    • 2002
  • A simple-structured thermal plasma generator for waste gas treatment has been studied. The thermal plasma technology applied to waste treatment has undoubtedly gained high importance owing to its outstanding properties such as flexibility, compact reactor, and clean treatment. Moreover, the thermal plasma generated by ac power has some additional advantages such as simple electrode system and easy maintenance. A prototype 200kW class plasma generator with specifications of 10-30m/sec gas velocity and 3000-5000K temperature on the center just outside of the nozzle has been designed and tested. Case studies on heat transfer, heat flow, velocity distribution, and temperature distribution using a commercial simulation package show lots of flexibility in design. The experimental results from theprototype generator show that the ac thermal plasma is easily controlled by working gas flow once it is ignited. A stabilization condition is discussed with the data from monitoring arc voltage drops with respect to gas flow rate during the test.

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A Study on Fault Characteristics of Wind Power in Distribution Feeders (풍력발전(DFIG)의 고압배전선로의 사고특성 해석에 관한 연구)

  • Kim, So-Hee;Kim, Byung-Ki;Rho, Dae-Seok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.3
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    • pp.1288-1295
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    • 2012
  • Korea Ministry of Knowledge Economy has estimated that wind power (WP) will be occupied 37% in 2020 and 42% in 2030 of the new energy sources, and also green energies such as photovoltaic (PV) and WP are expected to be interconnected with the distribution system because of Renewable Portfolio Standard (RPS) starting from 2012. However, when a large scale wind power plant (over 3[MW]) is connected to the traditional distribution system, protective devices (mainly OCR and OCGR of re-closer) will be occurred mal-function problems due to changed fault currents it be caused by Wye-grounded/Delta winding of interconnection transformer and %impedance of WP's turbine. Therefore, when Double-Fed Induction Generator (DFIG) of typical WP's Generator is connected into distribution system, this paper deals with analysis three-phase short, line to line short and a single line ground faults current by using the symmetrical components of fault analysis and PSCAD/EMTDC modeling.

Three-dimensional CFD simulation of geyser boiling in high-temperature sodium heat pipe

  • Dahai Wang;Yugao Ma;Fangjun Hong
    • Nuclear Engineering and Technology
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    • v.56 no.6
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    • pp.2029-2038
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    • 2024
  • A deep understanding of the characteristics and mechanism of geyser boiling and capillary pumping is necessary to optimize a high-temperature sodium heat pipe. In this work, the Volume of Fluid (VOF) two-phase model and the capillary force model in the mesh wick were used to model the complex phase change and fluid flow in the heat pipe. Computational Fluid Dynamics (CFD) simulations successfully predicted the process of bubble nucleation, growth, aggregation, and detachment from the wall in the liquid pool of the evaporation section of the heat pipe in horizontal and tilted states, as well as the reflux phenomenon of capillary suction within the wick. The accuracy and stability of the capillary force model within the wick were verified. In addition, the causes of geyser boiling in heat pipes were analyzed by extracting the oscillation distribution of heat pipe wall temperature. The results show that adding the capillary force model within the wick structure can reasonably simulate the liquid backflow phenomenon at the condensation; Under the horizontal and inclined operating conditions of the heat pipe, the phenomenon of local dry-out will occur, resulting in a sharp increase in local temperature. The speed of bubble detachment and the timely reflux of liquid sodium (condensate) replenishment in the wick play a vital role in the geyser temperature oscillation of the tube wall. The numerical simulation method and the results of this study are anticipated to provide a good reference for the investigation of geyser boiling in high-temperature heat pipes.

Effect of the Oriental Medicine Gi-Gong Exercise on the Brain Power, HRV, Live Blood Condition in the Youth (한방기공체조가 두뇌력, 심박변이율, 생혈액형태에 미치는 영향)

  • Lee, Jeong-Won;Kim, Yi-Soon;Kim, Gyeong-Cheol
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.21 no.1
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    • pp.126-135
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    • 2007
  • This study was conducted to identify the effects of the oriental medicine Qigong Exercise on the brain power, HRV, pulsation, live blood condition among young boys and girls. The study was performed with two group(control group and experimental group) in a pre-test/post-test design. The subjects were 44 young boys and girls selected by a some middle school in Busan. The oriental medicine Qigong Exercise program consists of 80-minute sessions three times a week over 5 months. All of the subjects were examined on the congnition assessment tool, stress assessment tool, oriental medicine pulsation 3-D MAC, live blood condition analyzer Prior and post surveys were measured before and after the experiment. In the cognition assessment, the amplitude of ERS were increased afer Qigong Exercise. The Success and the Concentration were significantly increased afer Qigong Exercise, the Error was significantly decreased afer Qigong Exercise. The Cognition strength was significantly increased, but the Reponse time was not significantly decreased afer Qigong Exercise. And the Workload was not significantly decreased, the Total Score was not significantly increased afer Qigong Exercise. Among the stress assessment, RRV tachogram's ‘mean RR’ was significantly increased, ‘mean HRV’ was significantly decreased afer Qigong Exercise. SDNN was not significantly increased, Complexity was not significantly increased afer Qigong Exercise. And TP(RRV power's total power) was not significantly increased, VLF and HF was significantly increased, and LF was significantly decreased afer Qigong Exercise. ANS's norm LF was not significantly decreased, but norm HF was significantly increased afer Qigong Exercise. In the RRV's Phase Plot, RMSSD and SDSD were not significantly increased, pnn50 was not significantly decreased afer Qigong Exercise. On the whole, Parasympathetic Activity and Stress Endurance were significantly increased, but Cardiac Activity and Physical Arousal were not significantly increased afer Qigong Exercise. Cardiac Aging was not significantly decreased afer Qigong Exercise. Sympathetic Activity, Autonomic Nervous System Balance and Heart-load were not significantly decreased afer Qigong Exercise. In the pulsation, press power was increased(15%), and w/t(pressurization time / pulsation time) was decreased(20%) afer Oigong Exercise. And the live blood condition was not changed afer Qigong Exercise. As mentioned above; the oriental medicine Qigong Exercise program was identified the effects of the inspiration of the brain power, heart rate and anti-stress.

Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013 (설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.12
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

An Efficient symbol Synchronization Scheme with an Interpolator for Receiving in OFDM (OFDM 전송방식의 수신기를 위한 보간기의 효율적인 심볼 동기방법의 성능분석)

  • 김동옥;윤종호
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.6 no.4
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    • pp.567-573
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    • 2002
  • In this paper, we propose a new symbol time synchronization scheme suitable for the OFDM system with an interpolator. The proposed scheme performs the following three steps. In the first step, the coarse symbol time synchronization is achieved by continuously measuring the average power of the received envelope signal. Based on this average power, the detection possibility for the symbol time synchronization is determined. It the signal is sufficient for synchronization, we next perform a relatively accurate symbol time synchronization by measuring the correlation between a short training signal and the received envelope signal. Finally, an additional frequency synchronization is performed with a long training signal to correct symbol synchronization errors caused by the phase rotation. From the simulation results, one can see that the proposed synchronization scheme provides a good synchronization performance over frequency selective channels.

Numerical Simulation of Irregular Airflow in OWC Wave Generation System Considering Sea Water Exchange (해수교환을 고려한 진동수주형 파력발전구조물에서 불규칙공기흐름에 관한 수치해석)

  • Lee, Kwang Ho;Park, Jung Hyun;Cho, Sung;Kim, Do Sam
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.25 no.3
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    • pp.128-137
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    • 2013
  • Due to the global warming and air pollution, interest in renewable energies has increased in recent years. In particular, the crisis of the depletion of fossil energy resources in the near future has accelerated the renewable energy technologies. Among the renewable energy resources, oceans covering almost three-fourths of earth's surface have an enormous amount of energy. For this reason, various approaches have been made to harness the tremendous energy potential. In order to achieve two purposes: to improve harbor water quality and to use wave energy, this study proposed a sea water exchange structure applying an Oscillating Water Column (OWC) wave generation system that utilizes the air flow velocity induced by the vertical motion of water column in the air chamber as a driving force of turbine. In particular, the airflow velocity in the air chamber was estimated from the time variations of water surface profile computed by using 3D-NIT model based on the 3-dimensional irregular numerical wave tank. The relationship of the frequency spectrums between the computed airflow velocities and the incident waves was analyzed. This study also discussed the characteristics of frequency spectrums in the air chamber according to the presence of the structure, wave deformations by the structure, and the power of the water and air flows were also investigated. It is found that the phase difference exists in the time series data of water level fluctuations and air flow in the air chamber and the air flow power is superior to the fluid flow power.

A Study on Fault Characteristics of DFIG in Distribution Systems Based on the PSCAD/EMTDC (PSCAD/EMTDC를 이용한 풍력발전의 배전계통 사고특성에 관한 연구)

  • Son, Joon-Ho;Kim, Byung-Ki;Jeon, Jin-Taek;Rho, Dae-Seok
    • Journal of the Korea Convergence Society
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    • v.2 no.2
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    • pp.47-56
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    • 2011
  • Korea Ministry of Knowledge Economy has estimated that wind power (WP) will be occupied 37% in 2020 and 42% in 2030 of the new energy sources, and also green energies such as photovoltaic (PV) and WP are expected to be interconnected with the distribution system because of Renewable Portfolio Standard (RPS) starting from 2012. However, when a large scale wind power plant (over 3[MW]) is connected to the traditional distribution system, protective devices (mainly OCR and OCGR of re-closer) will be occurred mal-function problems due to changed fault currents it be caused by Wye-grounded/Delta winding of interconnection transformer and %impedance of WP's turbine. Therefore, when Double-Fed Induction Generator (DFIG) of typical WP's Generator is connected into distribution system, this paper deals with analysis three-phase short, line to line short and a single line ground faults current by using the symmetrical components of fault analysis and PSCAD/EMTDC modeling.