• Proceedings of the KIEE Conference
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• summer
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• pp.301-303
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• 2004

This paper presents an islanding detection algorithm based on the second harmonic. When the DG(distributed Generator) was connected with utility supply, for maintenance and repair of equipment, an islanding occurred. So islanding detection algorithm must be developed for safety of human. Although the DG generating power is similar to power consumption. the proposed algorithm can detect the islanding condition very successfully.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.11
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• pp.27-36
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• 2013

Islanding in a gird connected inverter of wind power generation system may influence a bad effect on equipments or yield safety hazards on grid so it should be detected rapidly and exactly. A passive method to detect islanding is comparatively simpler than an active method but suffers from non detection zone (NDZ). On the other hand, the active method can significantly reduce NDZ by injecting a disturbance into inverter output. To improve the reliability of islanding detection, this paper proposes a hybrid anti-islanding detection method combining the conventional passive method as well as the active method based on novel harmonic injection method using fourier transform. The proposed scheme is fast to detect islanding when NDZ does not exist because it has the nature of passive method. Under NDZ, the active method can detect occurrence of islanding reliably. The effectiveness and validity of the proposed scheme is proved through comparative simulations.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.250-254
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• 2007

As photovoltaic(PV) power generation systems become more common, it will be necessary to investigate islanding detection method for PV systems. Islanding of PV systems can cause a variety of problems and must be prevented. However, if the real and reactive powers of the load and PV system are closely matched, islanding detection by passive methods becomes difficult. Also, most active methods lose effectiveness when there are several PV systems feeding the same island. The active frequency drift positive feedback method(AFDPF) enables islanding detection by forcing the frequency of the voltage in the island to drift up or down. In this paper the research for the minimum value of chopping fraction gain applied digital phase-locked-loop (DPLL) to AFDPF considering output power quality and islanding prevention performance are performed by simulation and experiment according to IEEE Std 929-2000 islanding test.

• Journal of Power Electronics
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• v.16 no.2
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• pp.760-768
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• 2016

Three-phase grid-connected inverters are widely applied in the fields of new energy power generation, electric vehicles and so on. Islanding detection is necessary to ensure the stability and safety of such systems. In this paper, feature recognition technology is applied and a novel islanding detection method is proposed. It can identify the features of inverter systems. The theoretical values of these features are defined as codebooks. The difference between the actual value of a feature and the codebook is defined as the quantizing distortion. When islanding happens, the sum of the quantizing distortions exceeds the threshold value. Thus, islanding can be detected. The non-detection zone can be avoided by choosing reasonable features. To accelerate the speed of detection and to avoid miscalculation, an active islanding detection method based on feature recognition technology is given. Compared to the active frequency or phase drift methods, the proposed active method can reduce the distortion of grid-current when the inverter works normally. The principles of the islanding detection method based on the feature recognition technology and the improved active method are both analyzed in detail. An 18 kVA DSP-based three-phase inverter with the SVPWM control strategy has been established and tested. Simulation and experimental results verify the theoretical analysis.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1918-1927
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• 2016

This paper proposes active frequency drift (AFD) as an anti-islanding method applied to micro-inverters with uncontrollable reactive power. When using ordinary inverter topologies, such as full bridge inverters in photovoltaic systems, the islanding phenomenon can be detected with reactive power-based methods, such as reactive power variation. However, when the inverter topology cannot control the reactive power, conventional anti-islanding methods with reactive power cannot be utilized. In this work, the topology used in this paper cannot control the reactive power. Thus, an anti-islanding method that can be used in topologies that cannot control the reactive power is proposed. The conventional anti-islanding method of the topology that cannot control reactive power is introduced and analyzed. Unlike the conventional AFD method, the proposed method extends a zero current interval every predetermined cycle. The proposed method offers certain advantages over conventional AFD methods, such as total harmonic distortion. The proposed method is validated through simulation and experiment.

• Journal of the Korean Solar Energy Society
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• v.27 no.2
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• pp.37-44
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• 2007

As photovoltaic(PV) power generation system becomes more common, it will be necessary to investigate islanding detection method for PV systems. Islanding of PV systems can cause a variety of problems and must be prevented. However, if the real and reactive power of the load and PV system are closely matched, islanding detection by Passive methods becomes difficult. Also, most active methods lose effectiveness when there are several PV systems feeding the same island. The active frequency drift positive feedback method(AFDPF) enables islanding detection by forcing the frequency of the voltage in the island to drift up or down. In this paper the research for the minimum value of chopping fraction gain applied digital phase-locked-loop (DPLL) to AFDPF considering output power quality and islanding prevention performance are performed by simulation and experiment according to IEEE Std 929-2000 islanding test.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.312-319
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• 2014

When distributed generation such as a wind power system is connected to the grid, it should meet grid requirements like IEEE Std. 1547, which regulates the anti-islanding method. Since the islanding may cause damage on electrical equipments or safety hazards for utility line worker, a distributed generation should detect it as soon as possible. This paper proposes a hybrid anti-islanding method coupled with the active and passive detection methods. To enhance the harmonic extraction capability for an active harmonic injection method, cascaded second-order band-pass filter and signal processing scheme are employed. Simulation and experiments are carried out under the islanding test condition specified in IEEE Std. 1547. Passive over/under voltage and over/under frequency methods are combined with the active method to improve the detection speed under certain condition. The simulation and experimental results are presented to verify that the proposed hybrid anti-islanding method can effectively detect the islanding.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.206-207
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• 2007

Islanding is the electrical phenomenon in a part of a power network disconnected from the utility, where the loads are entirely supplied by PV systems, and where the voltage and frequency are maintained around nominal values. But islanding may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards[4]. Therefore, islanding must be detected and stopped. The existing anti-islanding methods have NDZ(None-detection Zone) or power quality degradation. But PV-AF power generation system has the function of not only shunt active filter but also anti-islanding method without NDZ. In this paper, It is proved that PV-AF system has originally the function of anti-islanding without not only NDZ and but current distortion

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.410-416
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• 2022

A grid-connected inverter with critical loads uses mode transfer control to supply stable voltage to the load. An islanding detection method should also be used to quickly detect the grid fault and disconnect the inverter from the grid. However using the existing islanding detection method to detect islanding is difficult due to the small fluctuation of the voltage and frequency of the point of common coupling. This study proposes a reactive power P&O islanding detection method by using the positive feedback technique. The proposed method always injects a small variation of reactive power. When a grid fault occurs, the injected reactive power accelerates the reactive power injection reference. As a result, the reactive power reference value and the sensed reactive power become mismatched, and islanding is detected. Reducing the amount of real-time injected reactive power results in high efficiency and power factor. The simulation and experimental results of a 3 kW single-phase inverter are provided to verify the proposed islanding detection method.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.299-301
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• 2009

In this paper, a novel anti-islanding method of DC-AC single phase inverter is proposed. The inverter injects a little harmonic current with the output current of a PCS(Power Conditioning System). When the islanding condition is occurred, the voltage harmonic components appear on the output voltage of the PCS due to the injection of a little harmonic current. So, the PCS detects the voltage harmonic components using the Goertzel algorithm, and then the PCS decides that the islanding condition is occurred. When the PCS recognizes the islanding condition, the PCS are stopped. The proposed a novel anti-islanding method is analyzed, and its validity is proven through simulation.