• Title/Summary/Keyword: Power main transformers

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Design Guidelines for a Capacitive Wireless Power Transfer System with Input/Output Matching Transformers

  • Choi, Sung-Jin
    • Journal of Electrical Engineering and Technology
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    • v.11 no.6
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    • pp.1656-1663
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    • 2016
  • A capacitive wireless power transfer (C-WPT) system uses an electric field to transmit power through a physical isolation barrier which forms a pair of ac link capacitors between the metal plates. However, the physical dimension and low dielectric constant of the interface medium severely limit the effective link capacitance to a level comparable to the main switch output capacitance of the transmitting circuit, which thus narrows the soft-switching range in the light load condition. Moreover, by fundamental limit analysis, it can be proved that such a low link capacitance increases operating frequency and capacitor voltage stress in the full load condition. In order to handle these problems, this paper investigates optimal design of double matching transformer networks for C-WPT. Using mathematical analysis with fundamental harmonic approximation, a design guideline is presented to avoid unnecessarily high frequency operation, to suppress the voltage stress on the link capacitors, and to achieve wide ZVS range even with low link capacitance. Simulation and hardware implementation are performed on a 5-W prototype system equipped with a 256-pF link capacitance and a 200-pF switch output capacitance. Results show that the proposed scheme ensures zero-voltage-switching from full load to 10% load, and the switching frequency and the link capacitor voltage stress are kept below 250 kHz and 452 V, respectively, in the full load condition.

Improved High Efficiency Bidirectional Resonant Converter for V2G EV Charger (OBC) (V2G EV 충전기(OBC)를 위한 개선된 고효율 양방향 공진컨버터)

  • Oh, Jae-Sung;Kim, Min-Ji;Lee, Jun-Hwan;Woo, Jung-Won;Kim, Eun-Soo;Won, Jong-Seob
    • The Transactions of the Korean Institute of Power Electronics
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    • v.24 no.6
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    • pp.438-444
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    • 2019
  • In this paper, bidirectional LLC resonant DC/DC converters with the primary auxiliary windings in transformers of resonant circuits are proposed. Although the resonant capacitors are used on both the primary and secondary sides, regardless of the direction of power flow, the main feature of the proposed converters exhibits high gain characteristics without any mutual coupling between the resonant capacitors. For one of the proposed converters, an investigation of the operating characteristics in each mode has been carried out. A prototype of a 3.3 kW bidirectional LLC resonant converter for interfacing 750 V DC buses has been built and tested to verify the validity and applicability of the proposed converter.

Zero-Voltage Switching Two-Transformer Full-Bridge PWM Converter With Lossless Diode-Clamp Rectifier (새로운 무 손실 다이오드 클램프 회로를 채택한 두 개의 트랜스포머를 갖는 영 전압 스위칭 풀 브릿지 컨버터)

  • Yoon H. K.;Han S. K.;Park J. S.;Moon G. W.;Youn M. J.
    • Proceedings of the KIPE Conference
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    • 2004.07b
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    • pp.551-555
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    • 2004
  • The two-transformer full bridge (TTFB) PWM converter has two transformers which act as the output inductor as well as the main transformer, i.e. as the forward and the flyback transformer. Although the doubled leakage inductor of the TTFB makes it easier to achieve the zero-voltage switching (ZVS) of the lagging leg switch along the wide load range, it instigates a serious voltage ringing in the secondary rectifier diodes, which would require the dissipative snubber circuit, cause the serious power dissipation, and increase the voltage stress across those diodes. To overcome these problems, a, new lossless diode-clamp rectifier (LDCR) is employed as the output rectifier, which helps the voltage across rectifier diodes to be clamped on a half the output voltage $(V_o/2)$ or the output voltage $(V_o)$. Therefore, no dissipative snubber for rectifier diodes is needed and a high efficiency as well as low noise output voltage can be realized. The operations, analysis and design consideration of proposed converter are presented in this paper. To verify the validity of the proposed converter, experimental results from a 425W, 385-170Vdc prototype for the plasma display panel (PDP) sustaining power module (PSPM) are presented.

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Variable Output and Parallel Operation Control of EV Charger (전기자동차용 충전기의 가변출력 및 병렬운전 제어)

  • Lee, Sang-Hyeok;Kang, Seong-Gu;Awasthi, Prakash;Hwang, Jung-Goo;Lee, Seung-Yul;Wi, Han-Byul;Park, Sung-Jun
    • The Transactions of the Korean Institute of Power Electronics
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    • v.18 no.2
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    • pp.153-160
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    • 2013
  • This research paper describes the development of battery charger with a variable output voltage capacity for charging the batteries used in electrical vehicles. The voltage and current accordingly is control via the buck converter that receives three phase current at primary side and fed to bridge rectifier which is comprised of full bridge converter and HFTR(High Frequency Transformer) for isolation and a square wave AC output. The transformer primary side is in series to divide certain charging current and the secondary side is comprised of six fix transformers so that they can generate certain amount of power and various output voltage through relay connection using 6 DC outputs. Moreover, all parallel connected full bridge serial resonant converter communicate together with upper(main) controller. The constructed structure is verified by conducting the test on PSIM as well as experimentally.

Study of Temporal Data Mining for Transformer Load Pattern Analysis (변압기 부하패턴 분석을 위한 시간 데이터마이닝 연구)

  • Shin, Jin-Ho;Yi, Bong-Jae;Kim, Young-Il;Lee, Heon-Gyu;Ryu, Keun-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.11
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    • pp.1916-1921
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    • 2008
  • This paper presents the temporal classification method based on data mining techniques for discovering knowledge from measured load patterns of distribution transformers. Since the power load patterns have time-varying characteristics and very different patterns according to the hour, time, day and week and so on, it gives rise to the uninformative results if only traditional data mining is used. Therefore, we propose a temporal classification rule for analyzing and forecasting transformer load patterns. The main tasks include the load pattern mining framework and the calendar-based expression using temporal association rule and 3-dimensional cube mining to discover load patterns in multiple time granularities.

A Study on Nodal Probabilistic Reliability Evaluation at Load Points (각 지역별 확률론적 신뢰도 평가에 관한 연구)

  • Kim, Hong-Sik;Moon, Seung-Pil;Choi, Jae-Seok;Cha, Jun-Min
    • Proceedings of the KIEE Conference
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    • 2001.07a
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    • pp.206-209
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    • 2001
  • This paper illustrates a new method for reliability evaluation at load points in a composite power system. The algorithm includes uncertainties of generators and transmission lines as well as main transformers at substations. The CMELDC based on the new effective load model at HLII has been developed also. The CMELDC can be obtain from convolution integral processing of the outage capacity probabilistic distribution function of the fictitious generator and the original load duration curve given at the load point. The CMELDC based on the new model at HLII will extend the application areas of nodal probabilistic production cost simulation, outage cost assessment and reliability evaluation etc. at load points. The characteristics and effectiveness of this new model are illustrated by a case study of a small test system.

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Bus-voltage Sag Suppressing and Fault Current Limiting Characteristics of the SFCL Due to its Application Location in a Power Distribution System

  • Kim, Jin-Seok;Lim, Sung-Hun;Kim, Jae-Chul
    • Journal of Electrical Engineering and Technology
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    • v.8 no.6
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    • pp.1305-1309
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    • 2013
  • The application of the superconducting fault current limiter (SFCL) in a power distribution system is expected to contribute the voltage-sag suppression of the bus line as well as the fault-current reduction of the fault line. However, the application effects of the SFCL on the voltage sag of the bus line including the fault current are dependent on its application location in a power distribution system. In this paper, we investigated the fault current limiting and the voltage sag suppressing characteristics of the SFCL due to its application location such as the outgoing point of the feeder, the bus line, the neutral line and the 2nd side of the main transformer in a power distribution system, and analyzed the trace variations of the bus-voltage and fault-feeder current. The simulated power distribution system, which was composed of the universal power source, two transformers with the parallel connection and the impedance load banks connected with the 2nd side of the transformer through the power transmission lines, was constructed and the short-circuit tests for the constructed system were carried out. Through the analysis on the short-circuit tests for the simulated power distribution system with the SFCLs applied into its representative locations, the effects from the SFCL's application on the power distribution system were discussed from the viewpoints of both the suppression of the bus-voltage sag and the reduction of the fault current.

An SCR Thyristor Based Three-Phase Voltage Disturbance Generator

  • Han, Heung-Soo;Jung, Jae-Hun;Nho, Eui-Cheol;Kim, In-Dong;Kim, Heung-Geun;Chun, Tae-Won
    • Journal of international Conference on Electrical Machines and Systems
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    • v.1 no.3
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    • pp.372-378
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    • 2012
  • This paper deals with a 3-phase voltage disturbance generator for a performance test of custom power devices such as dynamic voltage restorers (DVR), dynamic uninterruptable power supplies (UPS), etc. The operating principle of the proposed circuit is described in each mode of voltage sag, swell, outage, and unbalance. The main components of the proposed disturbance generator are silicone controlled rectifier (SCR) thyristors, variable autotransformers, and transformers. Therefore, the disturbance generator can be implemented with a considerably low cost compared to the conventional pulse width modified (PWM) inverter and converter type generators. Furthermore, it has good features of high reliability with simple structure, high efficiency caused by no PWM switching of the SCR thyristors, and easy control with a wide variation range. To verify the validity of the proposed scheme, simulations and experiments are carried out.

A Study on the Optimal Distribution toss Management Using toss factor in Power Distribution Systems (분산형전원이 도입된 배전계통의 손실산정기법에 관한 연구)

  • Rho Dae-Seok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.6 no.3
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    • pp.231-240
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    • 2005
  • Recently, the needs and concerns for the power loss are increasing according to the energy conservation at the level of the national policies and power utilities's business strategies. Especially, the issue of the power loss is the main factor for the determining the electric pricing rates in the circumstances of the deregulation of electrical industry. However, because of the lacking of management for power loss load factors (LLF) it is difficult to make a calculation for the power loss and to make a decision for the electric rates. And loss factor (k-factor) in korea, which is a most important factor for calculation of the distribution power loss, has been used as a fixed value of 0.32 since the fiscal year 1973, There(ore, this study presents the statistical calculation methods of the loss factors classified by load types and seasons by using the practical data of 65 primary feeders which are selected by proper procedures. Based on the above the algorithms and methods, the optimal method of the distribution loss management classified by facilities such as primary feeders, distribution transformers and secondary feeders is presented. The simulation results show the effectiveness and usefulness of the proposed methods.

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Identification of Normally Operating High-Voltage Cables beyond Expected Life time (예상 수명을 초과하여 정상적으로 동작하는 고압 케이블의 확인)

  • Um, Kee-Hong;Lee, Kwan-Woo
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.15 no.5
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    • pp.207-212
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    • 2015
  • Continuous, high-quality supply of electrical energy is the backbone of any modern economy. Any equipment operating at a power station must be reliable and safe. All major power supply components such as transformers, cables, generators, and switchgear need to be kept in perfect operating condition. The lifetime of power cables, used as the main means of transferring electric power, is understood to be about 30 years, from the time of manufacturing. The dielectrics between two conductors of a cable must be able to withstand electrical stresses from high-voltage input. This condition should be verified throughout the lifetime of the cable system. Several techniques, such as VLF-tan${\delta}$, partial discharge, and insulation resistance are used in order to determine the operating conditions of cables. In this paper, we present our work on insulation resistance to diagnose cables in operation at the Western Power station in Taean, Chungcheong Namdo Province, South Korea. As a result we have found cables the life time of which is 38 years.