• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.218-220
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• 2003

본 논문에서는 UPFC(Unified Power Flow Controller)의 전력조류해석을 위해 직병렬컨버터를 두개의 전압원으로 등가화한 직병렬전압원 모델을 제시한다. 이 모델은 추가된 모선의 전압과 직병렬전압원의 전압을 추가하여 전력조류를 계산하므로, 선로에 흐르는 유무효전력조류를 직접 제어할 수 있다. 전력조류 변화에 따른 직병렬전압원의 전압크기 및 위상각이 변화됨을 확인하였고, UPFC 설치모선의 전압을 제어할 수 있음을 보여 직병렬전압원 모델이 실계통에 적용할 수 있음을 보였다.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.450-452
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• 2006

한전 전력연구원은 1990년대부터 FACTS(유연송전시스템 : Flexible AC Transmission System)을 연구해 온 이래 80MVA UPFC(종합조류제어기 : Unified Power Flow Controller)를 2003. 5월 신강진전력소관내 강진변전소에 준공하였다. 효성과 지멘스의 기술제휴를 통해 개발된 강진변전소 UPFC를 통해 FACTS 엔지니어링, 제어 알고리즘 및 유지보수 기술이 확보되었다. 초창기 안정화운전 기간동안 제어핵심기술과 일부예비품의 미확보가 가용율(Availability)에 큰 영향을 미쳤으나, 현재 강진 UPFC는 안정적으로 운전되고 있다. 본 논문에서는 그 동안의 강진 UPFC의 고장내용을 종합분석하고, 가용율을 정리하였다.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.305-307
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• 2003

This paper presents an apparent impedance calculation procedure for distance relaying of transmission line involving FACTS (Flexible AC Transmission System) devices, particularly the UPFC (Unified Power Flow Controller), between Kangjin and Jangheung in Korea. With the changes of UPFC's parameters, the measurement and protective range (trip boundaries) of the adaptive distance relay can also be changed. So, it is the most important part in the field of system protection to analyze the operating characteristic of relaying system. The presence of UPFC significantly affects the trip boundaries which are also adversely affected by fault resistance combined with remote end infeed. This paper presents the apparent impedance calculations and the distance relay setting characteristics for faults involving the UPFC in the KEPCO system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.7
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• pp.281-289
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• 2006

Advanced controllers among Flexible AC Transmission System(FACTS) devices employ self-commutated switching converters, VSI (Voltage Sourced Inverters), as the synchronous voltage source. Such controllers are SSSC (Static Synchronous Series Compensator), STATCOM (Static Synchronous Compensator) and UPFC (Unified Power Flow Controller). UPFC is series-shunt combined controller. Its series and shunt inverters can be modeled as SSSC and STATCOM but the dependant relation between the inverters is very complex. For that reason, the complexity makes it difficult to develop the UPFC model by simply combining the SSSC and STATOM models when we apply the model for conventional power system dynamic simulation algorithm. Therefore, we need each relevant models of VSI type FACTS devices for power system analysis. This paper proposes a modeling approach which can be applied to modeling of VSI type FACTS devices. The proposed method using Newton-type current injection method can be used to make UPFC, SSSC, and STATCOM models. The proposed models are used for 2-area test system simulation, and the results verify their effectiveness.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.259-262
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• 2001

본 논문은 2003년 한전 실계통(154kV 강진 S/S)에 적용예정인 80MVA UPFC(Unified Power Flow Controller)시스템의 동적특성을 EMTDC/PSCAD를 이용하여 분석한 결과이다. UPFC는 FACTS 기기중 전압, 임피던스, 위상각등 전력전송 제어를 위한 송전선로의 모든 파라미터를 동시에 독립적으로 제어 할 수 있는 FACTS기기[1]로서, 미국 Inez S/S, Marcy S/S에 이어 강진 S/S에 80MVA 용량의 UPFC가 실계통 적용될 예정이다. 본 논문은 과도현상 해석 프로그램인 PSCAD/EMTDC를 이용하여 80MVA UPFC 제어기와 적용 대상 계통인 강진 S/S 인근 계통을 모델링하고 상정사고에 대한 UPFC 제어효과 분석에 대하여 기술하였다. 적용된 EMTDC UPFC모델은 실제 80MVA UPFC 기기에 채용된 전력회로, 제어기, 보호시스템과 동일하게 모델링하였으며 적용 대상계통은 PSS/E 해석결과와 동일하도록 강진 S/S인근 계통을 축약 등가화한 계통모델을 사용하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.5
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• pp.391-395
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• 2008

KEPCO 80MVA UPFC has been operated in Gangjin Substation since May 2003. This UPFC is composed of 40MVA shunt inverter and 40MVA series inverter, and developed in technical cooperation between Hyosung and Siemens. KEPCO has tried to localize UPFC control technique after its installation and developed GTO Thyristor Valve Test Equipment for annual maintenance test. The development of this equipment make it possible to process GTO Thyristor module test automatically and manage historic data systematically, which could improve UPFC reliability.

• KIEE International Transactions on Power Engineering
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• v.5A no.3
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• pp.244-251
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• 2005

Power transfer capability has been recently highlighted as a key issue in many utilities. It is determined by the thermal stability, dynamic stability and voltage stability limits of generation and transmission systems. In particular, voltage stability affects power transfer capability to a great extent in many power systems. This paper presents a tool for determining total transfer capability from a static voltage stability viewpoint using IPLAN, which is a high level language used with the PSS/E program. The tool was developed so as to analyze static voltage stability and to determine the total transfer capability between different areas from a static voltage stability viewpoint by tracing stationary behaviors of power systems. A unified power flow controller (UPFC) is applied for enhancing total transfer capability between different areas from the viewpoint of static voltage stability. Evaluation of the total transfer capability of a practical KEPCO power system is performed from the point of view of static voltage stability, and the effect of enhancing the total transfer capability by UPFC is analyzed.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.528-530
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• 2003

UPFC Pilot plant project의 결과물로써 설계, 제작된 80MVA급 UPFC(Unified Power Flow Controller)는 현재 강진변전소 강진-장홍 154kV 선로에 설치되어 commissioning 시험을 완료하고 시험 운전되고 있다. UPFC는 기존에 수동적으로 제어하였던 선로의 전압, 임피던스 및 위상각을 능동적으로 제어함으로써 전력공급의 신뢰성 및 유연성을 높일 수 있다. 이러한 기능을 갖는 UPFC의 시험 운전을 통하여 UPFC의 기기자체의 성능을 검증하고 기기의 운전 영역의 변화가 인근의 계통에 미치는 영향에 대하여 조사하였다.

• Transactions on Electrical and Electronic Materials
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• v.17 no.1
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• pp.1-6
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• 2016

Ensuring the secure operation of power systems has become an important and critical matter during the present time, along with the development of large, complex and load-increasing systems. Security constraints such as the thermal limits of transmission lines and bus-voltage limits must be satisfied under all of a system’s operational conditions. An alternative solution to improve the security of a power system is the employment of Flexible Alternating-Current Transmission Systems (FACTS). FACTS devices can reduce the flows of heavily loaded lines, maintain the bus voltages at desired levels, and improve the stability of a power network. The Unified Power Flow Controller (UPFC) is a versatile FACTS device that can independently or simultaneously control the active power, the reactive power and the bus voltage; however, to achieve such functionality, it is very important to determine the optimal location of the UPFC device, with the appropriate parameter setting, in the power system. In this paper, a genetic algorithm (GA) method is applied to determine the optimal location of the UPFC device in a network for the enhancement of the power-system loadability and the minimization of the active power loss in the transmission line. To verify our approach, simulations were performed on the IEEE 14 Bus, 30 Bus, and 57 Bus test systems. The proposed work was implemented in the MATLAB platform.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.488-489
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• 2008

Based on the fact that renewable energies such as photovoltaic, wind power, etc. are increasingly used in distribution systems recently which affects overvoltage, this paper implements an unified power flow controller(UPFC) to compensate voltage swell. The implemented scheme employs an ac chopper and a low-pass filter along with a series transformer. The ac chopper converts the amplitude of the voltage down to the nominal value. The low pass filter makes the rough waveform of the output voltage of the ac chopper due to switching smoothly by eliminating harmonics. To verify the effectiveness of the implemented UPFC, the results by Electro-Magnetic Transients Program(EMTP) are presented for various overvoltage cases.