• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.37-49
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• 2007

To detect islanding mode when the grid is being tripped is a major safety issue in utility interactive PV(UIPV) system. Widely used techniques among various active methods to detect islanding mode are Reactive power variation (RPV)method and Active frequency drift(AFD) method. In this paper, analytical design method is suggested for AFD and RPV method under IEEE recommended islanding test condition. And in order to show the validity of proposed method, EMTP based simulation was done for UIPV system with RPV method and AFD method. Results shows proposed method is very useful.

• Proceedings of the KIPE Conference
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• 2008.10a
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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.

• Journal of the Korean Solar Energy Society
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• v.26 no.4
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• pp.17-23
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• 2006

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 enables the islanding detection to drift up (or down) the frequency of the voltage during the islanding situation. In this paper, injecting the periodic zero current into the basic AFD method is proposed. This proposed method shows the analytical design value of cf to meet the test procedure of IEEE Std. 1547 with various load conditions. Detection of islanding is verified using simulation tool PSIM.

• 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.

• Proceedings of the KIEE Conference
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• 2005.07b
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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.

• Journal of the Korean Solar Energy Society
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• v.26 no.1
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• pp.91-98
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• 2006

Islanding phenomenon of utility-connected photovoltaic power conditioning systems(PV PCS) can cause a variety of problems and must be prevented. If the real and reactive power supplied by PV PCS are closely matched to those of load, islanding detection by passive methods becomes difficult. The active frequency drift(AFD) method, called the frequency bias method, enables islanding detection by forcing the frequency of the voltage in the islanding to drift up or down. In this paper, non-detection zone(NDZ) of AFD is analyzed for the islanding detection method of utility-connected PV PCS by the simulation software tool PSIM.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.2
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• pp.160-167
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• 2009

To detect islanding mode when the grid is being tripped is a major safety issue in the Utility Interactive Photo Voltaic (UIPV) system. In this paper, analytical design method is suggested for AFD & RPV method under IEEE 929-2000 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 UIPV system.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.524-525
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• 2015

본 논문은 계통연계형 소용량 태양광 인버터에 적용된 AFD(Active Frequency Drift) 기반의 단독 운전 검출 기법을 제안한다. 태양광 시스템에 일반적인 인버터 토폴로지를 사용한 경우, 무효전력 주입을 이용하여 단독운전 검출이 가능하다. 하지만 무효전력의 제어가 불가능한 인버터를 사용한 경우에는 기존의 무효전력을 이용하는 단독운전 검출기법을 사용할 수 없다. 무효전력의 제어가 불가능한 인버터 토폴로지에 새로운 스위칭 기법을 적용하면 무효전력을 주입한 효과를 얻을 수 있고, 이를 통해 기존의 AFD 방식을 응용하여 단독운전 검출이 가능한 새로운 검출기법을 제안하였다. 제안하는 검출기법은 기존의 AFD 방식보다 인버터 출력전류의 THD (Total Harmonic Distortion)를 개선할 수 있는 장점이 있다. 제안하는 기법의 성능을 시뮬레이션을 통해 확인하였다.

• 전자공학회논문지 IE
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• v.43 no.2
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• pp.63-69
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• 2006

Islanding phenomenon of utility-connected PV power conditioning systems(PV PCS) can cause a variety of problems and must be prevented. If the real and reactive powers supplied by PV PCS are closely matched to those of load, islanding detection by passive methods becomes difficult. The active frequency drift(AFD) method, called the frequency bias method, enables islanding detection by forcing the frequency of the voltage in the islanding to drift up or down. In this paper, non-detection zone(NDZ) of AFD is analyzed for the islanding detection method of utility-connected PV PCS by simulation tool PSIM.

• 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.