• Title/Summary/Keyword: reactive capability limitation

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Analysis of Reactive Power Capability for Salient Synchronous Generators, and its Application to Primary Restorative Systems (돌극형 동기 발전기의 무효전력 공급 한계 해석 및 우선공급계통에의 적용)

  • Lee, H.J.;Park, S.M.
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.1
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    • pp.14-17
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    • 2007
  • Power system restoration following a massive blackout starts with re-energizing primary restorative transmission systems at first. The comparison of the TLCC(transmission line charging capacity) and the RPC(reactive power capability) of related black-start generator should be considered in this stage because overvoltage can be caused by self-excitation at the generator when the RPC is smaller than the TLCC. The RPC can be decided by two criteria. One is stator end core heating, and the other is steady state stability. RPC in steady state stability area has been found based on a synchronous reactance Xd. This paper presents RPC limit of salient pole machine which is different from that of non-salient pole machine in steady state stability area and shows derivation process about that.

Analysis Of The Primary Restorative Transmission System To Prevent Self-excitation (자기여자(Self-Excitation) 방지를 고려한 시송전 선로에 관한 연구)

  • Lee, Hung-Jae;Kim, Sang-Seop;Park, Sung-Min;Hwang, Bong-Hwan;Lee, Nam-Ho
    • Proceedings of the KIEE Conference
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    • 2002.07a
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    • pp.44-46
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    • 2002
  • Service restoration following a complete or partial collapse starts with reenergize a transmission line from black-start generators. Voltage problems can arise by Ferranti effect as unloaded transmission line is reenergized. This paper presents analytical results on the primary restorative transmission system focused on the voltage problem during the early restoration process. Methodologies to handle load pick-up compensating Ferranti effect. and terminal voltage and reactive capability limitation of black-start generators about self-excitation are presented. An algorithm for static analysis about these methodologies is developed, and EMTDC simulation for verifying the efficiency of the algorithm is performed.

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Development of the Primary Restorative Transmission System Analyser to Restore Massive Blackout (광역정전 복구를 위한 시송전 계통 분석시스템 개발)

  • Lee, Nam-Ho;Song, In-Jun;Kim, Kyeong-Ho;Ghoo, Jin-Boo
    • Proceedings of the KIEE Conference
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    • 2002.11b
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    • pp.161-163
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    • 2002
  • Service restoration following a complete or partial collapse starts with reenergizing a transmission line from black-start generators. Voltage problems can arise from Ferranti effect as unloaded transmission line is reenergized. This Paper presents system analyser to develop for verifying the primary restorative transmission system. The algorithm which has been used in the analyser is to handle load pick-up compensating Ferranti effect. and terminal voltage and reactive capability limitation of black-start generators about self-excitation.

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Control Strategy Compensating for Unbalanced Grid Voltage Through Negative Sequence Current Injection in PMSG Wind Turbines

  • Kang, Jayoon;Park, Yonggyun;Suh, Yongsug;Jung, Byoungchang;Oh, Juhwan;Kim, Jeongjoong;Choi, Youngjoon
    • Proceedings of the KIPE Conference
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    • 2013.07a
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    • pp.244-245
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    • 2013
  • This paper proposes a control algorithm for permanent magnet synchronous generator with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage offshore wind power system under unbalanced grid conditions. The proposed control algorithm particularly compensates for the unbalanced grid voltage at the point of common coupling in a collector bus of offshore wind power system. This control algorithm has been formulated based on the symmetrical components in positive and negative rotating synchronous reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power are described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of ac input current is injected to the point of common coupling in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm makes it possible to provide a balanced voltage at the point of common coupling resulting in the generated power of high quality from offshore wind power system under unbalanced network conditions.

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Primary Restorative Transmission Line Selection for Myanmar's Electric Power System

  • Kim, Yong-Hak;Song, In-Jun;Jang, Byung-Tae;An, Yong-Ho
    • Journal of Electrical Engineering and Technology
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    • v.5 no.2
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    • pp.191-196
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    • 2010
  • Power system restoration following a massive or complete blackout starts with energizing the primary restorative transmission system. During this primary restoration process, unexpected overvoltage may happen due to nonlinear interaction between the unloaded transformer and the transmission system. In the case of the Myanmar electric power system, there are so many wide outage experiences, including complete blackout cases, caused by 230kV line faults and so on. Consequently, Myanmar's system operators have been well trained to deal with wide blackouts. Howver, system blackout restoration has been conducted by relying on the experience of only a few specialists. So, more scientific analysis is required to meet the requirements necessary to ensure fast and reliable system restoration. This paper presents analytical results on the primary restorative transmission system of Myanmar, focusing on the problems during the early restoration process. Methodologies are presented that handle load pick-up, terminal voltage and the reactive capability limitation of black-start generators to compensate the Ferranti effect. Static and dynamic simulation with the PSSolution and EMTDC programs respectively for the six cases are performed in order to select the primary restorative transmission lines.

Compensation of Unbalanced PCC Voltage in an Off-shore Wind Farm of PMSG Type Turbines (해상풍력단지에서의 PMSG 풍력발전기를 활용한 계통연계점 불평형 전원 보상)

  • Kang, Ja-Yoon;Han, Dae-Su;Suh, Yong-Sug;Jung, Byoung-Chang;Kim, Jeong-Joong;Park, Jong-Hyung;Choi, Young-Joon
    • The Transactions of the Korean Institute of Power Electronics
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    • v.20 no.1
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    • pp.1-10
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    • 2015
  • This paper proposes a control algorithm for permanent magnet synchronous generators with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage off-shore wind power system under unbalanced grid conditions. Specifically, the proposed control algorithm compensates for unbalanced grid voltage at the PCC (Point of Common Coupling) in a collector bus of an off-shore wind power system. This control algorithm has been formulated based on symmetrical components in positive and negative synchronous rotating reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power is described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of AC input current is injected into the PCC in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm enables the provision of balanced voltage at the PCC resulting in the high quality generated power from off-shore wind power systems under unbalanced network conditions.

Real-Time Spacer Etch-End Point Detection (SE-EPD) for Self-aligned Double Patterning (SADP) Process

  • Han, Ah-Reum;Lee, Ho-Jae;Lee, Jun-Yong;Hong, Sang-Jeen
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.436-437
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    • 2012
  • Double patterning technology (DPT) has been suggested as a promising candidates of the next generation lithography technology in FLASH and DRAM manufacturing in sub-40nm technology node. DPT enables to overcome the physical limitation of optical lithography, and it is expected to be continued as long as e-beam lithography takes place in manufacturing. Several different processes for DPT are currently available in practice, and they are litho-litho-etch (LLE), litho-etch-litho-etch (LELE), litho-freeze-litho-etch (LFLE), and self-aligned double patterning (SADP) [1]. The self-aligned approach is regarded as more suitable for mass production, but it requires precise control of sidewall space etch profile for the exact definition of hard mask layer. In this paper, we propose etch end point detection (EPD) in spacer etching to precisely control sidewall profile in SADP. Conventional etch EPD notify the end point after or on-set of a layer being etched is removed, but the EPD in spacer etch should land-off exactly after surface removal while the spacer is still remained. Precise control of real-time in-situ EPD may help to control the size of spacer to realize desired pattern geometry. To demonstrate the capability of spacer-etch EPD, we fabricated metal line structure on silicon dioxide layer and spacer deposition layer with silicon nitride. While blanket etch of the spacer layer takes place in inductively coupled plasma-reactive ion etching (ICP-RIE), in-situ monitoring of plasma chemistry is performed using optical emission spectroscopy (OES), and the acquired data is stored in a local computer. Through offline analysis of the acquired OES data with respect to etch gas and by-product chemistry, a representative EPD time traces signal is derived. We found that the SE-EPD is useful for precise control of spacer etching in DPT, and we are continuously developing real-time SE-EPD methodology employing cumulative sum (CUSUM) control chart [2].

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Compensation of Unbalanced PCC Voltage in Off-shore Wind Farms of PMSG Type Turbine

  • Kang, Jayoon;Han, Daesu;Suh, Yongsug;Jung, Byoungchang;Kim, Jeongjoong;Park, Jonghyung;Choi, Youngjoon
    • Proceedings of the KIPE Conference
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    • 2014.07a
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    • pp.215-216
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    • 2014
  • This paper proposes a control algorithm for permanent magnet synchronous generator with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage offshore wind power system under unbalanced grid conditions. The proposed control algorithm particularly compensates for the unbalanced grid voltage at the point of common coupling in a collector bus of offshore wind power system. This control algorithm has been formulated based on the symmetrical components in positive and negative rotating synchronous reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power are described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of ac input current is injected to the point of common coupling in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm makes it possible to provide a balanced voltage at the point of common coupling resulting in the generated power of high quality from offshore wind power system under unbalanced network conditions.

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