• 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.

• 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.

• 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.

• Animal Bioscience
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• v.35 no.11
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• pp.1733-1743
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• 2022

Objective: This study was aimed to explore the efficacy of combination of endo-xylanase (Xyn) and xylan-debranching enzymes (arabinofuranosidase, Afd and feruloyl esterase, FE) in improving utilization of bran in piglet diet. Methods: In vitro experiments were firstly conducted to examine the enzymological properties of Xyn, Afd, and FE, concurrent with their effect on degradation of arabinoxylan (Abx) in bran. In vivo experiment was then implemented by allocating two hundred and seventy 35-d-old postweaning piglets into 3 groups (6 replicates/group), which received bran-containing diet supplemented with Xyn (1,600 U/kg) or its combination with Afd (0.8 U/kg) and FE (4 U/kg) or without enzyme. Results: Both Xyn, Afd, and FE are relatively stable against the changes in temperature and pH value. Combining Xyn with Afd and FE had a superiority (p<0.05) over Xyn alone and its combination with Afd or FE in promoting (p<0.05) degradation of Abx in different brans. Combined treatment with Xyn, Afd, and FE was more beneficial than Xyn alone to induce increasing trends (p<0.10) of average daily gain, final body weight and feed efficiency of piglets fed bran-containing diet. Moreover, combination of Xyn, Afd, and FE showed advantages (p<0.05) over Xyn alone in causing reductions (p<0.05) in diarrhea rate and cecal pH value, concurrent with increases (p<0.05) in cecal and colonic acetic acid and total volatile fatty acid concentrations, as well as cecal butyric acid concentration of piglets fed bran-containing diet. Conclusion: Combining Xyn with Afd and FE was more beneficial than Xyn alone in promoting degradation of Abx in bran, along with growth performance and intestinal volatile fatty acid profile of piglets received bran-containing diet. Thereby, combination of Xyn, Afd, and FE had a superior efficacy relative to Xyn alone in improving application of cereal bran in piglet diet.

• 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.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.78-81
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• 2008

HDTV로 전환되면서 방송국에서는 4:3의 SDTV와 16:9의 HDTV가 동시 방송되는 과도기를 맞고 있다. 유럽에서 채택한 DTV 표준인 DVB 방식인 경우 MPEG에 화면 비 정보와 AFD 정보를 신호에 실어 수신 장치에서 화변 비 정보를 알 수 있도록 하고 있다. 이 정보를 이용하여 방송에 따라 화면 비를 설정하고 최적의 화면 비율 상태로 시청할 수 있는 모드를 제공하도록 소프트웨어로 구현하고자 한다.

• 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 Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.7 s.110
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• pp.629-637
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• 2006

It is important to design the high-speed communication system in the hostile channel. Due to the frequency diversity, FD-OFDM that can be used for the high-speed communication is more robust to the noise or interference than ordinary OFDM. However, even the FD-OFDM becomes degraded in th ε strong narrow band interference channel. In this paper, we propose an AFD-OFDM system and analyze the communication performances in order to find out the more robust communication system in the hostile channel. So, the AFD-OFDM system can cover the drawback of the FD-OFDM and improve the BER performance than FD-OFDM. From the simulation results, FD-OFDM shows better performance than the ordinary OFDM. Furthermore, AFD-OFDM shows more excellent performance than FD-OFDM in the strong narrow interference channel.