• KIEE International Transactions on Power Engineering
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• v.5A no.2
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• pp.103-108
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• 2005

Catastrophic failures in power systems are rare but not uncommon events. Protection systems play an important role in the progression of events during a catastrophic failure. This paper will examine some of the historical records, and suggest possible improvements to protection systems which can have a positive impact on power system performance during catastrophic failures.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.9
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• pp.1096-1102
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• 1999

This paper discusses the evaluation of interconnection capacity of small cogeneration(SCOGN) systems to the power distribution systems from the viewpoint of voltage regulation. Power utilities are required to keep the customers' voltage profile over a feeder close to the rated value under all load conditions. However, it is expected that the interconnection of SCOGNs to the power distribution systems impacts on the existing voltage regulation method and customers' voltage variations. Therefore, SCOGNs should be integrated to the automated power distribution systems to prevent interconnection problems and supply high quality electricity to the customers. For these reasons, we should proceed with the evaluation of interconnection capacity of SCOGNs to the power distribution systems. However, it is generally impossible to perform actual testing on the power distribution systems, and standardized methodologies and guidelines are not developed to evaluate it. The criterion indexes for voltage regulation and variations are presented in order to evaluate the interconnection capacity of SCOGNs to the power distribution systems. In addition, the evaluation methodology of interconnection capacity of SCOGNs for power distribution systems is presented. It is expected that the resulted of this paper are useful for power system planners to determine the interconnection capacity of SCOGNs and dispersed storage and generation (DSG) systems to the power distribution systems.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.322-323
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• 2010

본 논문은 2MW급 풍력시스템의 이중여자유도형 발전기(DFIG)를 제어하기 위한 PCS의 전력변환장치와 주변장치 및 제어기술에 대해서 기술한다. 최근 국내 뿐만 아니라 해외 전력회사에서는 계통전원 사고 시 풍력시스템이 계통연계를 유지하면서 계통의 전력품질에 기여할 수 있는 기능(FRT)을 요구하고 있다. FRT기능 구현을 위한 H/W와 제어 시퀀스를 소개한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2185-2191
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• 2009

Wind power and photovoltaic(PV) generation systems are the fastest growing sources of renewable energy. The nonlinear devices, such as power electronic converter or inverter, of wind power and PV generation systems are the source of harmonics in power systems. The harmonic-related problems can have significant detrimental effects in the power system, such as capacitor heating, data communication interference, rotating equipment heating, transformer heating, relay misoperation and switchgear failure. There is a greater need for harmonic analysis that can properly maintain the power quality. By measuring harmonics of existing wind power and PV generation systems as harmonics modeling, the studies were made to see the harmonic impact of grid-connected wind power and PV generation systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.4
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• pp.244-258
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• 2019

The reliability of power electronic systems becomes increasingly important, as power electronic systems have gradually gained an essential status in a wide range of industrial applications. Accordingly, recent research has made an effort to improve the reliability of power electronic systems to comply with stringent constraints on safety, cost, and availability. The condition monitoring of power electronic components is one of the main topics in the research area of the reliability of power electronic systems. In this paper, condition-monitoring methods of reliability-critical components in power electronic systems are discussed to provide the current state of knowledge by organizing and evaluating current representative literature.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.2
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• pp.111-119
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• 2019

In this study, constant power generation (CPG) algorithms are introduced for whole range power point tracking in photovoltaic systems. Currently, maximum power point tracking (MPPT) algorithm is widely used for high-power photovoltaic systems. However, MPPT algorithm cannot flexibly control such systems according to changing grid conditions. Maintaining grid stability has become important as the capacity of grid-connected photovoltaic systems is increased. CPG algorithms are required to generate the desired power depending on grid conditions. A grid-connected photovoltaic system is configured, and CPG algorithms are implemented. The performances of the implemented algorithms are compared and analyzed by experimental results.

• Progress in Superconductivity and Cryogenics
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• v.7 no.2
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• pp.47-51
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• 2005

This paper is for studying the feasibility of SFCL application for the interconnection operation of 154kV power systems under 345kV S/S in Korean power system. All Korean 154kV power systems are constructed as loop systems in downtown. However, the present 154kV systems are operated with separated systems around 345kV S/S because of fault current and overload problems. In this study, we investigate the structure and operation of 154kV power system in Seoul and study the feasibility of interconnection operation of 154kV systems under 345kV systmes by applying SFCLs to 154kV bus-tie.

• Journal of Power Electronics
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• v.9 no.2
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• pp.320-333
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• 2009

A Photovoltaic (PV) system's power output varies with the change of climate. Frequency deviations, tie line voltage swings are caused by the varying PV power when large PV power from several PV systems is fed in the utility. In this paper, to overcome these problems, a simple coordinated control method for smoothing the variations of combined PV power from multiple PV systems is proposed. Here, output power command is formed in two steps: central and local. Fuzzy control is used to produce the central smoothing output power command considering insolation, variance of insolation and absolute average of frequency deviation. In local step, a simple coordination is kept between the central power command and the local power commands by producing a common tuning factor. Power converters are used to achieve the same output power as local command power employing PI control law for each of the PV generation systems. The proposed method is compared with the method where conventional Maximum Power Point Tracking (MPPT) control is used for each of the PV systems. Simulation results show that the proposed method is effective for smoothing the output power variations and feasible to reduce the frequency deviations of the power utility.

• KIEE International Transactions on Power Engineering
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• v.4A no.2
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• pp.91-99
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• 2004

This paper illustrates a tie line constrained equivalent assisting generator (TEA G) model considering forced outage rates of transmission systems for reliability evaluation of interconnected power systems. Interconnections between power systems can provide improved levels of reliability. It is expected that the TEAG model developed in this paper will prove useful in the solution to problems related to the effect of transmission system uncertainties in the reliability evaluation of interconnected power systems. The characteristics and concept of this TEAG considering transmission systems are described in detail by sample studies on a simple test system.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.278-279
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• 2010

본 논문은 태양광 인버터에 배터리 저장 장치가 포함된 ES(Energy Storage)용 태양광 발전시스템에 관한 내용이다. 배터리에 에너지를 충/방전시키기 위한 절연형 양방향 컨버터를 제안 하였으며, 태양광 발전시스템과 에너지 저장 시스템과의 운전 알고리즘에 대해 제안하고자 한다.