• 전력전자학회논문지
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• 제24권2호
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• pp.105-110
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• 2019

This study proposed a reactive power variation (RPV) method equipped with positive feedback (PF) for detecting the islanding operation of distributed generation systems. The proposed RPV consists of the constant reactive power component and a certain reactive power term and uses the frequency deviation between the rated and the measured frequencies. The constant reactive power is injected from distributed generation system and power factor is to 0.9975 in grid-connected operation. PF is activated from generation of the frequency deviation and the injected reactive power is continuously increased due to PF when islanding occurs. Consequently, the increasing reactive power causes the point of common coupling frequency to deviate from the maximum/minimum threshold level. Performance of the proposed RPV is verified in a 1.7 kW T-type inverter, and the detection times are 53 and 150 ms.

• 전자공학회논문지 IE
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• 제43권2호
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• pp.63-69
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• 2006

계통연계형 태양광발전 시스템(PV PCS : Photovoltaic Power Conditioning Systems)의 단독운전은 다양한 문제들을 야기 할 수 있으며, 따라서 이는 반드시 방지되어야 한다. 실제로는 단독운전이 발생할 확률이 매우 낮지만, PV PCS가 공급하는 유 무효 전력이 부하가 요구하는 유 무효 전력과 거의 일치한다면, 수동적인 방법만으로는 단독운전 검출이 힘들게 된다. AFD(Active Frequency Drift) 기법은 주파수 바이어스 방법이라고 일컬어지는 방법으로, 단독운전 상태에서 계통과 연결된 노드전압의 주파수를 강제로 빠르게 또는 느리게 하여 단독운전을 검출하는 방법이다. 본 논문에서는 최근에 들어서 PV PCS의 능동적 단독운전 검출방법으로 많이 사용되는 AFD 기법의 불검출영역을 널리 사용되는 시뮬레이션 툴(PSIM)을 사용하여 분석하였다.

• 전기학회논문지
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• 제62권12호
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• pp.1792-1797
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• 2013

Recently, due to the excessive use of fossil fuels, many studies about the fossil fuels such as solar and fuel cell energy source are progressing. Fuel cell system has high energy conversion efficiency. Also, fuel cell system is environmentally friendly system because the carbon emission is almost not occur. Therefore, the fuel cell system is considered as the core technology of in the fields of the future energy and environmental. Fuel cell system has an effect on distribution power system because another power source of other than large power plants. So, fuel cell system can be reason of power quality in the power system. In this paper, we constructed the system for an assessment on Islanding. The system is composed with power source, Impedance coordination load and linear load, fuel cell system. we are performed assessment on voltage and power quality in customer and the distributed power system during the Islanding of residential fuel cell system. In addition, no change in the impedance of power system, we made a islanding condition only using the actual load, As a variation of generation and load current under islanding, an analysis results based on assessment system showed that the power qualities of distribution system became more aggravation as effect of voltage sag and voltage swell phenomena.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.525-526
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• 2006

Recently, much research has been done and many improvements have been developed for islanding protection of distributed generation(DG). Anti-islanding protection for DG must be act very quickly to prevent equipment damage at the time of disconnection and for the safety of maintenance and repair personnel. DG-based detection methods have included both passive and active types, and now research has shifted towards new anti-islanding detection methods that make up for the defects of the previous types. Because differences occur between the utility grid and the DG when connecting and disconnecting depending on the phase difference, voltage, current, relative capacity of electric power, and system operation characteristics, voltage phase angle is an important consideration. In this paper, we simulated islanded operation characteristics comparing phase difference of DG and the connected utility grid, and analyzed various parameters (real power, reactive power, RMS voltage, RMS current, power factor angle, and frequency) by varying the DG's voltage phase angle. Using this information, we propose a suitable DG voltage phase angle for enhanced passive islanding detection techniques.

• Journal of Power Electronics
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• 제16권2호
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• pp.704-716
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• 2016

Small distributed generation units are usually connected to the main electric grid through single-phase voltage source inverters. Grid operating conditions such as voltage and frequency are not constant and can fluctuate within the range values established by international standards. Furthermore, the requirements in terms of power factor correction, total harmonic distortion, and reliability are getting tighter day by day. As a result, the implementation of reliable and efficient control algorithms, which are able to adjust their control parameters in response to changeable grid operating conditions, is essential. This paper investigates the configuration topology and control algorithm of a single-phase inverter with the purpose of achieving high performance in terms of efficiency as well as total harmonic distortion of the output current. Accordingly, a Second Order Generalized Integrator with a suitable Phase Locked Loop (SOGI-PLL) is the basis of the proposed current and voltage regulation. Some practical issues related to the control algorithm are addressed, and a solution for the control architecture is proposed, based on resonant controllers that are continuously tuned on the basis of the actual grid frequency. Further, intentional islanding operation is investigated and a possible procedure for switching from grid-tied to islanding operation and vice-versa is proposed.

• 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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1477-1479
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• 2004

Increasing numbers of photovoltaic arrays are being connected to the power utility through the power conditioning systems (PCS). This has raised potential problems of network protection. If, due to the action of the PCS, the local network voltage and frequency remain within regulatory limits when the utility is disconnected, then islanding is said to occur. In this paper, the representative methods to prevent the islanding are described and a PSIM-based model and analysis of the reactive power variation (RPV) method are presented. A novel phase detector using the all-pass filter and digital phase locked loop (DPLL) is proposed especially for the single-phase PCS. Finally, this paper provides the simulation and experimental results with a single-phase 3kW prototype PCS. Islanding test method of IEEE Std. 929-2000 was performed for verification.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.440-442
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• 1995

In a recently as renewable energy source photovoltaic(PV) system using solar energy has been very widely researched because of its pollution-free and infinity. Especially many researches are intensively focused on small scale utility interactive PV system which can use dead space and easily make power stabilized from unstable natural energy source. In this system one of the most important matters is islanding protection. Islanding phenomenon appears when power failure occurs. For the safety of utility interactive PV system must has the function of not only system protection but also detection of islanding. This paper describes parallel operating alghorithm using reactive power variation method and twin peak band pass filter. This alghorithm is verified useful by simulation.

• 한국태양에너지학회 논문집
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• 제39권4호
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• pp.69-77
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• 2019

Among the main functions of the grid-connected photovoltaic (PV) system, the anti-islanding operation function is a very important problem. Recently, due to the improvement in power generation efficiency and the maintenance advantages in PV system, the use of string inverter has increased so that the possibility of islanding operation has been raised. Generally, when a power system faults, the PV inverter must be disconnected from power system within 10 cycles by the anti-islanding operation function. However, in the real-time of power system, the output power of the PV system within 10cycles is effected. In this paper, we analyzed the effect of grid-connected PV system on power quality in a short time within 10 cycles on fault case of power system using the Matlab Simulink program.

• 한국가스학회지
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• 제22권5호
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• pp.124-132
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• 2018

파리협정의 체결로 신 재생에너지 보급이 활발해지고 있다. 국내의 경우 공공건물 중심으로 신 재재생에너지 보급 정책이 진행되고 있으며, 건물 내에 설치가 비교적 수월한 연료전지 시스템의 보급이 확대될 전망이여서 계통연계형 연료전지 전력변환장치의 단독운전방지 평가 연구가 중요하다. 본 연구에서는 연료전지 전력변환장치의 국내 인증기준 KGS AB934 PC53이 해외 규격과 부합하는지 검토해보고 계통연계 시 중요한 안전성능인 단독운전방지 평가에 대해 분석하였다. 또한, 병렬로 연결된 두 대의 전력변환장치의 단독운전방지 평가를 위한 시작품을 제작하고 실증 평가를 통해 여러 대의 연료전지 시스템이 설치되고 있는 상황에 맞는 안전성능 확보 방안을 연구하였다.