• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.2
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• pp.182-190
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• 2011

This paper proposes a LVRT (Low Voltage Ride Through) control strategy which should be satisfied by grid-connected wind power system when grid faults occur. The LVRT regulation indicates rules or actions which have to be executed according to the voltage dip ratio and the fault duration. Especially the wind power system has to support the grid with specified reactive current to secure the grid stability when voltage reduction ratio is over 10%. The LVRT regulation in this paper is based on the German Grid Code and full-scale variable speed wind power conversion system is considered for LVRT control strategy. The proposed LVRT control strategy satisfies not only LVRT regulation but also makes power balance between wind turbine and power system through additional DC link voltage regulation algorithms. Because it is impossible to control grid side power when the 3-phase to ground fault occurs, the DC link voltage is controlled by a generator side inverter using the DC link voltage control strategy. Through the simulation and experiment result, the proposed LVRT control strategy is evaluated and its effectiveness is verified.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.842-845
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• 2009

본 연구에서는 신 에너지전원(태양광)이 배전계통에 연계되어 운용되는 것을 상정하여, 정상상태와 비상(사고)상태, 전력품질(순시), 스마트배전설비 등에 대한 배전계통의 특성 및 신 에너지전원의 특성을 시험하고 분석할 수 있는 분산전원용 계통연계 시뮬레이터를 제작하고 평가하기 위하여, 배전계통 전용해석 S/W인 PSCAD/EMTDC를 이용하여 사전 시뮬레이션을 수행하여 설계를 수행하고, 시험결과를 분석하였다. 본 연구에서 제작한 시뮬레이터는 배전용변전소(154/22.9KV)의 주변압기와 3상 4선식 22.9KV 고압배전선로의 2개 선로 및 부하를 축약형태(약 1/100)로 모의한 것이지만, 주상변압기(13,200/380/220V) 이하의 저압 배전선로는 실계통과 거의 동일한 상태로 모의한 것이다. 이상의 구성요소 데이터를 산출하기 위하여 PSCAD/EMTDC를 이용하여 사전 시뮬레이션을 수행하여 설계 및 제작을 수행하고 그 효용성을 확인하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.323-329
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• 1998

In this paper, we compose of the utility interactive photovoltaic(PV) generation system with a PWM stepdown chopper and a current source inverter. The stepdown chopper is controlled by the several gate pulses (twice frequency of utility voltage, square pulse and without the chopper) of chopper part to reduce pulsation of DC current and size of DC reactor. PV current only is measured for maximum power point tracking without any influence on the variation of insolation and temperature. Therefore, we can control modulation factor of the chopper to operate at maximum power point of solar cell. And, the utility interactive photovoltaic generation system supplies an AC power to the load and the utility power system.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.204-206
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• 2002

계통연계 풍력발전시스템의 특성을 고찰하기 위해서는 블레이드, wind turbine, 정류기, 인버터 등의 풍력발전시스템의 각 구성요소의 모델링과 적절한 제어 알고리즘에 대한 모의가 요구된다. 본 연구에서는 동기발전기를 풍력발전기로 사용하고 있는 계통연계형 풍력발전시스템의 출력 및 동특성을 모의하기 위한 전류제어형 전압원인버터의 PSCAD/EMTDC 모듈을 제시한다. 풍속의 가변특성에 의해 동기발전기에 들어오는 입력은 변하게 되고, 동기발전기가 동기주파수를 유지할 수 있도록 인버터에서는 이러한 입력과 동일한 출력을 낼 수 있어야 하며, 동시에 계통에서 허용하는 일정 전압과 계통주파수와 동일한 주파수를 갖는 출력을 공급해야 한다. 본 논문에서는 이를 위해 동기발전기의 주파수를 제어하는 전류제어형 전압원인버터 모듈을 소개한다. 모의를 통해 결과를 검증한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3130-3136
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• 2009

This paper deals with the optimal on-line real time voltage regulation methods in power distribution systems interconnected with the Distributed Generation(DG) systems. In order to deliver suitable voltage to as many customers as possible, the optimal sending voltage should be decided by the effective voltage regulation method by using artificial neural networks to consider the rapid load variation and random operation characteristics of DG systems. The results from a case study show that the proposed method can be a practical tool for the voltage regulation in distribution systems including many DG systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.127-133
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• 1999

Ths paper deals with the active and reactive power control of Battery Energy Storage System (BESS) during its interconnection operation to power distribution system When an interconnection operation of BESS to power distribution system, it is well suited for peak load shaving and distribution voltage compensation by controlling the real and reactive power. Equivalent mxiel of the distribution system and the BESS is derived and power flow equations are presented to control the real and reactive power of BESS. In this paper, to control the active and reactive power of BESS, $P-\delta$ and Q-V control method and ntJIrerical description is presented. To verify the proposed control method, using PSCAD/EMTDC program simulates the active and reactive power control of BESS.f BESS.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.396-404
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• 2011

This paper proposes a performance improvement of a grid-connected wind turbine using sliding-mode based direct power control under an unbalanced grid fault. The proposed control method has some advantages for grid connected control. At first, it doesn't need the synchronous phase angle of the grid voltage. It has also fast dynamic characteristics compared with a conventional current controller. In addition, it is suitable for an unbalance compensation control. The effectiveness and robustness of the proposed algorithm are verified by simulations and experiments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2388-2392
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• 2013

Wind generation systems are very different in nature from conventional generation systems. Therefore it is necessary to research dynamic characteristics of wind generation systems connected to a power system. The stability analysis of wind turbine generator is an important issue in the operation of the power system. The result of angular stability of the power system that consists of only synchronous generators is different from that of the power system including wind turbine generators. This is due to the fact that generators connected to wind turbines are generally induction generators. The angular stability assessing synchronization of generators is determined by its corresponding critical clearing time(CCT). Wind turbine models for the analysis of power system are varied and difficult to use, but now these are standardized into four types. In this paper, the analysis of the CCT of the power system connected to wind farm considering the location and capacity is performed by using DFIG(Doubly-Fed induction Generator) wind turbine built-in type3 model in PSS/E-32.

• Journal of Energy Engineering
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• v.12 no.2
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• pp.154-163
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• 2003

Grid connection essentially requires a wind energy conversion system (WECS) to not only supply adequate power responding to constantly varying wind speed but also provide a specified level of voltage magnitude and frequency that is acceptable in the electric power network. To satisfy such requirements, appropriate control schemes of a wind turbine to be connected to the power grid should be employed. This paper presents an output control strategy of a grid-connected wind power generation, which consists of a fixed-pitch wind turbine, a synchronous generator and a AC-DC-AC component with a voltage source inverter built in, and performs modelling and analysis of the strategy using PSCAD/EMTDC, an electromagnetic transient analysis software. Real power output control of the voltage source inverter is implemented to extract the maximum energy from wind speed inputted through wind blades and reactive power control, to keep the terminal voltage of WECS at a specific level. SPWM switching method is used to reduce the harmonics and maintain 60 ㎐ of the output frequency. The wind turbine performance and output corresponding to wind variation and the terminal load change is simulated and analysed.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.27-29
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• 2018

본 논문은 모듈형 멀티레벨 컨버터 기반 특고압 직류 배전망의 수전 계통 사고 대응 기법을 제안한다. 수전 계통의 순간적인 저전압 및 단락 사고 발생 시 전력변환장치는 계통 전압의 정상화를 지원하기 위해 연계를 유지해야 하며 계통 측의 요구에 따라 전압 변동률에 따른 무효 전력을 공급해야 한다. 제안하는 기법은 계통 사고 발생 시 계통 코드에 따라 무효 전류를 공급하여 수전 계통의 전압 레벨 복구를 지원한다. 시뮬레이션을 통해 제안하는 계통 사고 대응 기법의 타당성을 확인한다.