• Title/Summary/Keyword: transformers

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Controlling Zero Sequence Component in DVR for Compensating Unbalanced Voltage Dip of a DFIG

  • Ko, JiHan;Thinh, Quach Ngoc;Kim, SeongHuyn;Kim, Eel-Hwan
    • Proceedings of the KIPE Conference
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    • 2012.07a
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    • pp.154-155
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    • 2012
  • The dynamic voltage restorer (DVR) is an effective protection device for wind turbine generator based on doubly-fed induction generator (DFIG) operated under the unbalanced voltage dip conditions. The compensating voltages of DVR depend on the voltage dips and on the influence of the zero sequence components. If the $Y_0/{\Delta}$ step-up transformers are used, there are no zero sequence components on the DFIG side. However, if the $Y_0/Y_0$ step-up transformers are used, the zero sequence components will appear during faults. The zero sequence components result in the high insulation costs and the asymmetric of the terminal voltages. This paper proposes a method for controlling zero sequence components in DVR to protect DFIG under unbalanced voltage dips. Simulation results are presented to verify the effectiveness of the proposed control method.

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Dynamic Characteristic Analysis of Novel Unified Power Flow Controller Using 3-Level Half-Bridge Inverter Modules (3-레벨 반브리지 인버터로 구성된 새로운 UPFC의 동특성 분석)

  • Baek, Seung-Taek;Soh, Yong-Chul;Han, Byung-Moon
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.53 no.3
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    • pp.116-121
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    • 2004
  • This paper proposes a novel UPFC based on 3-level Half-bridge modules, isolated through single-phase multi-winding transformers. The dynamic performance of proposed system was analyzed by simulation with EMTDC, assuming that the UPFC is connected with the 138-kV transmission line of one-machine-infinite-bus power system. The proposed system can be directly connected to the transmission line without series injection transformers. It has flexibility in expanding the operation voltage by increasing the number of 3-level Half-bridge modules.

Fault Diagnosis of Oil-filled Power Transformer using DGA and Intelligent Probability Model (유중가스 분석법과 지능형 확률모델을 이용한 유입변압기 고장진단)

  • Lim, Jae-Yoon;Lee, Dae-Jong;Ji, Pyeong-Shik
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.65 no.3
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    • pp.188-193
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    • 2016
  • It has been proven that the dissolved gas analysis (DGA) is the most effective and convenient method to diagnose the transformers. The DGA is a simple, inexpensive, and non intrusive technique. Among the various diagnosis methods, IEC 60599 has been widely used in transformer in service. But this method cannot offer accurate diagnosis for all the faults. This paper proposes a fault diagnosis method of oil-filled power transformers using DGA and Intelligent Probability Model. To demonstrate the validity of the proposed method, experiment is performed and its results are illustrated.

A Technical Trend on UHF Techniques for On-Line PD Monitoring and Site Testing for Transformer (전력용 변압기의 온라인 PD 모니터링과 시험을 위한 UHF 기술 동향)

  • Kim, Byung-Woo;Kim, Yun-Seok;Kim, Chang-Bok;Cho, Soo-Young;Choi, Young-Il;Choi, Yong-Sung;Lee, Kyung-Sup
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.1972-1973
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    • 2007
  • A field-oriented UHF system for on-line PD monitoring of transformers is designed, which has been installed inside the oil tank of a transformer. This system has successfully captured long intermittent discharge signals that hadn't been detected through conventional techniques, and solved the problem successfully. The results demonstrate that UHF technique has great advantages for on-line PD monitoring of transformers. By adopting the peak detection technique, it becomes easy and effective for the transplantation of the phase-resolved pattern recognition technique from conventional method to UHF method, and then to realize continuous on-line monitoring, source characterization and trending analysis.

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Cascade 3-Phase IHCML Inverter using maximal distension vector control (최근접 벡터 제어기법을 이용한 Cascade 3상 IHCML 인버터)

  • Song, Sung-Geun;Park, Sung-Jun;Nam, Hae-Kon
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.187-189
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    • 2007
  • In this paper, the cascade 3-phase IHMCL inverter using two low frequency transformers is proposed. The proposed inverter is constructed by connecting a 3-phase IHCML inverter. the cascade 3-phase IHCML inverter has several advantages. One advantage is that only one input power source is required because of using transformers to isolate. Another advantage is that the switching frequency of the high power switches is almost fundamental frequency of reference and the other the switching frequency of the low power switches is higher. It can be known that cascade 3 phase IHCML inverter has the excellent efficiency and the outstanding electric quality. lastly, we tested the 5kW cascade 3-phase IHCML inverter to clarify the proposed electric circuit and reasonableness of control signal for the proposed inverter.

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A Study on Design and Analysis of Piezoelectric Transformer for Resonance Mode (공진모드의 변화에 따른 압전변압기의 특성에 관한 연구)

  • 정현호;이상기;박태곤;김명호;이원재
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.432-435
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    • 2000
  • This paper present a new sort of multilayer piezoelectric ceramic transformer for the application to AC-adapters. This piezoelectric transformers operate in the second and third length extensional vibration mode. And the output performance of two types of piezoelectric transformers are compared by ANSYS, which is one of the FEM analysis program. As a result the minimum displacement was occurred at the two points in second length extensional vibration mode and three point in third length extensional vibration mode. One is the middle of input and the other is middle of output parts. And output voltage was inversely decreased by increasing number of output layers. Also The third mode type is shown higher power transition ratio than the second mode type.

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Assessment of Insulation Condition in Large Transformers (대형변압기 절연상태 평가)

  • Kim, Hee-Dong;Kong, Tae-Sik;Lee, Young-Jun;Park, Jae-Jun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07a
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    • pp.499-502
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    • 2004
  • In order to detect of insulation problems an early, transformer has to be performed the several tests. The ac current and tan6 of transformer winding insulation were investigated by Schering bridge. Partial discharge(PD) tests are used to evaluate the insulation condition of transformer. The moisture content measurement was conducted using RVM(recovery voltage meter). The RVM test can show that the problem is affecting the paper insulation of transformer. The value of moisture content was 2.3% in main transformer. The insulations of four transformers were judged to be in good condition.

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The Loss Calculation of Eddy Current of the Tank and Winding Supports in Transformers by the Leakage Flux (누설자속에 의한 대용량 변압기의 권선지지구조 및 외함의 와전류손실 계산에 관한 연구)

  • Heo, Woo-Heng;Lee, Dong-Yeup;Kim, Gyu-Tak
    • Proceedings of the KIEE Conference
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    • 2005.07b
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    • pp.948-950
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    • 2005
  • This paper compared the test data with the loss when a conductor is exposed to the magnetic fieldof reactors after generating external magnetic field in specimen by means of an air core reactor model and the calculation of loss came from a tying the combination of FEM and integral method. It was applied to the loss measurement of transformers due to leakage flux.

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Phase-Shift Triple Full-Bridge ZVZCS Converter with All Soft Switched Devices

  • Zhu, Junjie;Qian, Qinsong;Lu, Shengli;Sun, Weifeng
    • Journal of Power Electronics
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    • v.19 no.6
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    • pp.1337-1350
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    • 2019
  • This paper proposes a Phase-Shift Triple Full-Bridge (PSTB) Zero-Voltage Zero-Current-Switching (ZVZCS) converter with a high switching frequency and high efficiency. In the proposed converter, all three bridge legs are shared leading-legs, and all three transformers work in the Discontinuous Conduction Mode (DCM). Thus, all of the switches and diodes in the PSTB ZVZCS can be soft switched. Moreover, since all of the transformers can pass energy from the primary-side to the secondary-side when their primary-side currents are not zero, there is no circulating current. As a result, the PSTB ZVZCS converter can achieve a high efficiency at high operating frequencies. A theoretical analysis and the characteristics of the proposed converter are presented and verified on a 1MHz 200~300V/24V 1.2kW hardware prototype. The proposed converter can reach a peak efficiency of 96.6%.

A case study of condition monitoring for mold transformers on urban railway transit (도시철도용 몰드변압기 상태감시를 위한 사례조사 연구)

  • Kim, Do-Yoon;Jung, Ho-Sung;Park, Young;Han, Seok-Youn;Lee, Sang-Bin
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.235-240
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    • 2008
  • Since urban railway transit is one of the most essential transportation systems, its power facilities must ensure high reliability and safety. Currently, urban railway operating organizations perform TBM (Time Based Maintenance) on power facilities. However, in order to improve management efficiency and system safety, CBM (Condition Based Maintenance) is preferred. Among various power facilities, mold transformers has been chosen as the object of study since it is widely used for the purpose of minimizing volume and weight, and due to safety against fire. In this paper, various transformer failure cases due to electric, thermal, mechanical and environmental factors have been collected and analyzed. In addition, investigation on national and international condition based maintenance cases and the characteristics of sensors widely used for transformer monitoring has been performed to suggest the optimal condition based maintenance technique for urban railway systems.

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