• 한국태양에너지학회 논문집
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• 제29권6호
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• pp.75-80
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• 2009

Recently, as the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, these have raised potential problems of network protection on electrical power system. One of the numerous problems is an Islanding phenomenon. In this paper, active frequency drift (AFD) method, one of the anti-islanding methods which is analyzed by current magnitude compensation and calculation of RMS value of the output power is proposed and verified by simulation.

• 전력전자학회논문지
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• 제17권6호
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• pp.546-552
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• 2012

This paper presents an active anti-islanding detection method using negative sequence voltage injection to the grid through a three-phase photovoltaic inverters. Because islanding operation mode can cause a variety of problems, the islanding detection of grid-connected photovoltaic inverter is the mandatory feature. The islanding mode is detected by measuring the magnitude of negative sequence impedance calculated by the negative sequence voltage and current at the point of common coupling. Simulation and experimental test are performed to verify the effectiveness of the proposed method which can detect the islanding mode in the specified time. The test has been done in accordance with the condition on IEEE Std 929-2000.

• 전력전자학회논문지
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• 제12권1호
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• pp.37-49
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• 2007

계통연계형 PV 시스템의 중요한 보호기능인 단독운전 검출기능은 시스템의 안전성 및 전기적 안정성 측면에서 매우 중요하다. 단독운전 검출기법으로는 크게 수동적 방식과 능동적 방식으로 분류되는 다양한 기법들이 있다. 본 연구에서는 IEEE 929-2000에서 제시하는 단독운전 시험조건 하에서 현재 널리 사용되는 능동적 방식 중 무효전력 변동 방식(RPV method)과 능동적 주파수 변동 방식(AFD method)을 채용한 시스템의 연계점에서 주파수 변동 특성을 해석하였다. 그리고 해석결과를 바탕으로 RPV 방식 및 AFD 방식의 설계법을 제시하였다. EMTP를 이용한 시스템 시뮬레이션을 통하여 제안된 해석 및 설계법의 타당성 및 유효성을 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.203-206
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• 2004

An islanding occurs when the utility grid is removed but distributed sources continuo to operate and provide power to local loads and grid. This can cause a significant risk to safety and equipment. This report present a novel anti-islanding method to prevent an islanding phenomenon. The proposed method changes the reactive power of the load. Therefore the phase difference between output voltage and current is periodically changed within decided value. When the utility-grid is removed, the frequency of output voltage and current will increase or decrease. And the proposed system will detect the change of frequency and shut down the distributed source. While the conventional methods have some difficulties in detecting particular islanding condition such as a small change in loading, the proposed method can detect most conditions. The performance was verified through experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.271-273
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• 2005

Islanding of PV systems occurs when the utility grid is removed but local sources continue to operate and provide power to local loads. Islanding is one of the serious problems in an electric power system connected with dispersed power sources. Also, this can present safety hazards and the possibility of damage to other electric equipments. If the real and reactive power of RLC load and PV system are closely matched, islanding phenomena can't be detected by the passive methods. Several active methods were proposed to detect islanding phenomena. The most effective method is SFS method which was suggested by Sandia National Laboratory. In this paper, a new anti-islanding algorithm is proposed and its validity is verified through simulation and experimental results for utility interconnection of PV system.

• 전력전자학회논문지
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• 제8권2호
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• pp.199-210
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• 2003

본 논문에서는 계통연계형 태양광발전시스템의 고립운전방지를 위한 새로운 고리운전 검출기법을 연구한다. 이를 위하여 계통연계형 태양광발전시스템 및 고립운전시의 특성에 대하여 기술하였다. 또한 고립운전의 검출특성을 향상시키기 위한 새로운 검출기법을 제시하고 해석하였으며 검출시험을 위한 부하조건 선정을 위한 부하임피던스 곡선을 해석적으로 유포하였다 ACSL 시뮬레이션 및 실험을 통하여 제시한 고립운전 검출기법 및 해석결과를 검증하였다.

• 전력전자학회논문지
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• 제15권3호
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• pp.179-187
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• 2010

본 논문에서는 무효전력변동기법을 사용하여 단독운전을 검출을 하기 위해서 선행되어야 하는 주파수 검출 방법 중에서 개선된 이산푸리에변환(Discrete Fourier Transform; DFT), 즉 Goertzel 알고리즘을 이용한 단독운전 검출기법을 제안한다. 실제 태양광 발전 시스템의 설치를 위해서는 전기사고나 시스템에 악영향을 유발하는 단독운전 검출기법의 연구가 선행되어야 한다. 적용하는 주파수 검출방법은 Goertzel 알고리즘을 이용한 기법으로 기존의 영점검출기법과 가상의 2상 PLL(Phase Locked Loop)에 비하여 외란의 영향에 강인하며 빠른 검출이 가능하다. 시뮬레이션 및 실험을 통하여 기존의 주파수검출기법인 영점검출기법과 가상의 2상 PLL을 이용한 주파수 검출과 제안하는 알고리즘을 비교하고 그의 우수성을 검증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 추계학술대회 논문집
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• pp.64-67
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• 2008

To detect islanding mode when the grid is being tripped is a major safety issue in the Utility Interactive Distributed Generation (UIDG) system. In this paper, analytical design method is suggested for AFD & RPV method under IEEE929-2000 recommended islanding test condition. We have discussed that there is a same point. we injected reactive component of the current by AFD & RPV methods, but the current reference generated is other waveform. Possible if amount of reactive components in this methods are same each method, there is happened same rates frequency variation. To verify the validity of the analytical comparison, this paper presents simulation and experimental results from single phase, 3[kW] inverter for the transformerless UIDG system.

• 한국태양에너지학회 논문집
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• 제28권2호
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• pp.64-69
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• 2008

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, these have raised potential problems of network protection on electrical power system. One of the numerous problems is an Islanding phenomenon. There has been an argument that it may be a non-issue in practice because the probability of islanding is extremely low. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an islanding can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficiently to cause a trip, plus the time required to execute a trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. Third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an islanding. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. Therefore the verification of anti-islanding performance is strongly needed. In this paper, improved RPV method is proposed through considering power quality and anti-islanding capacity of grid-connected single-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"). And the simulation results are verified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1705-1707
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• 2005

This paper proposes a novel active frequency drift(AFD) method for the islanding prevention of grid-connected photovoltaic inverter. To detect the islanding phenomenon of grid-connected photovoltaic(PV) inverters concerning about the safety hazards and the damage to other electric equipments, many kinds of anti-islanding methods have been presented. Among them, AFD method using chopping fraction(cf) enables the islanding detection to drift up(or down) the frequency of the voltage during the islanding situation. However, the performance of the conventional AFD methods, which have a certain value of cf only, is inefficient and difficult to design the appropriate cf value analytically to meet the limit of harmonics. In this paper, the periodic chopping fraction based on an AFD method is proposed. This proposed method shows the analytical design value of cf to meet the test procedure of IEEE Std. 929-2000 with the power quality and islanding detection time. To verify the validation of the proposed method, the islanding test results are presented. It is confirmed that the proposed method has not only less harmonic distortion but also good performance of islanding detection compare with the conventional AFD method.