• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.351-352
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• 2016

Since anti-islanding scheme of grid-connected inverter is a key function of standards compliance, unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, many anti-islanding schemes have been researched, however, existing anti-islanding schemes show poor power quality and non-detection zone issues. Besides, most of them have problems which deteriorate performance of islanding detection under parallel-operation. Therefore, this paper proposes a new anti-islanding scheme that has both negligible power quality degradation, no non-detection zone and precise islanding detection under parallel-operation. Finally, both simulation and experimental results validate the proposed scheme.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.247-254
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• 2015

Unintentional islanding results in safety hazards, power quality degradation, and many other issues. Thus, islanding detection of grid-connected distributed generation system is a key function for standards compliance. Many anti-islanding schemes are currently being studied; however, existing anti-islanding schemes used in inverters have power quality degradation and non-detection zone issues. Therefore, this paper analyzes existing anti-islanding schemes by using frequency drift in accordance with both islanding detection performance and power quality. This paper also proposes a new anti-islanding scheme by using frequency drift. Both simulation and experimental results show that the proposed scheme has negligible power quality degradation and no non-detection zones compared with other existing schemes.

• Journal of the Korean Solar Energy Society
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• v.35 no.2
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• pp.11-19
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• 2015

Islanding is a phenomenon that EPS(Electric Power System) is continuously energized by PV PCS(Photovoltaic Power Conditioning System) even when EPS is isolated from the grid. Unintentional islanding will result in safety hazard, power quality degradation and many other issues. So, islanding protection of grid-connected PV PCS is a key function for standards compliance. Nowadays, many anti-islanding schemes are researched. But existing anti-islanding schemes used in PV PCS have power quality degradation and non-detection zone issues. This paper analyses not only detection performance of existed anti-islanding schemes using active frequency drift but also THD of PCS output current according to each value disturbance for anti-islanding. In addition, the lowest value of disturbance in each scheme was tabulated under guarantee of anti-islanding condition.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.283-289
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• 2016

Islanding protection of a grid-connected photovoltaic (PV) inverter is a key function for standards compliance. Unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, many anti-islanding schemes have been examined. However, existing anti-islanding schemes have poor power quality and non-detection zone issues. Moreover, most schemes have problems that deteriorate the performance of islanding detection under parallel operation. Therefore, this paper proposes a novel anti-islanding scheme that has negligible power quality degradation and has no non-detection zone and islanding detection under a parallel operation. Both simulation and experimental results validate the proposed scheme.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.540-549
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• 2015

Unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, the islanding detection of a power conditioning system of a distributed generation, such as a grid-connected photovoltaic inverter, is a key function for standard compliance. Currently, many anti-islanding schemes have been examined, but existing anti-islanding schemes have poor power quality and non-detection zone issues. Therefore, this study analyzes the non-detection zone in a more deliberate manner than the existing analysis of the non-detection zone and proposes a new anti-islanding scheme, which has negligible power quality degradation and no non-detection zone. Simulation and experimental results validate that the proposed scheme shows much better performance than other existing schemes.

• Journal of the Korean Solar Energy Society
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• v.37 no.3
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• pp.13-22
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• 2017

Anti-islanding scheme of grid-connected inverter is a key function of standards compliance, since unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, many anti-islanding schemes have been researched, however, most of them have problems, which deteriorate performance of islanding detection under parallel-operation. Therefore, this paper proves the reason of problems and proposes a new anti-islanding scheme that has precise islanding detection under parallel-operation in single-phase and three-phase system. Finally, both simulation and experimental result validate the proposed scheme.

• 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.

• Journal of Power Electronics
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• v.7 no.1
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• pp.64-71
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• 2007

This paper proposes a novel active frequency drift (AFD) method to improve the islanding detection performance with minimum current harmonics. To detect the islanding phenomenon of grid-connected photovoltaic (PV) inverters concerning the safety hazards and possible damage to other electric equipment, anti-islanding methods have been described. The AFD method that uses 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 method is inefficient and causes difficulty in designing the appropriate cf value to meet the limit of harmonics. In this paper, the periodic chopping fraction based on a novel 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 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 better performance of islanding detection compared with the conventional AFD method.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.6
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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.

• 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.