The Experts below are selected from a list of 10221 Experts worldwide ranked by ideXlab platform
Ning He - One of the best experts on this subject based on the ideXlab platform.
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an improved islanding detection method for a grid connected inverter with intermittent bilateral reactive Power Variation
IEEE Transactions on Power Electronics, 2013Co-Authors: Jun Zhang, Dehong Xu, Guoqiao Shen, Ye Zhu, Ning HeAbstract:An islanding detection method for a grid-connected inverter incorporating intermittent bilateral (IB) reactive Power Variation (RPV) is described. The inverter output with IB reactive Power enables the detection of an islanding. The RPV range is derived in order to eliminate the nondetection zone. The design scheme of Variation time in the method is obtained by estimating the transient response due to islanding occurrence. In addition, the effect of the proposed detection strategy on Power quality is investigated. The proposed islanding detection method has been experimentally verified on a three-phase grid-connected 6-kW inverter.
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a novel rpv reactive Power Variation anti islanding method based on adapted reactive Power perturbation
Applied Power Electronics Conference, 2012Co-Authors: Dehong Xu, Jun Zhang, Guoqiao Shen, Ning He, Yangfan Zhang, Changsheng HuAbstract:In this paper, a novel intermittent reactive-Power-Variation (RPV) method based on loads’ resonance frequency detection is proposed to reduce the injected reactive Power. The RPV method detects the frequency of point of common coupling (PCC) and outputs the minimum reactive Variation, which perturbs the frequency of PCC to the frequency thresholds decided by the utility standards when the islanding condition happens. Furthermore, the islanding detecting control strategy under unbalanced loads condition is discussed. Compared with the traditional bilateral RPV method, the proposed method only output unilateral RPV in each Variation period and the Variation amplitude of each period is less than 5% of the output active Power $(P)$ , thus the perturbation of reactive Power can be reduced significantly. In addition, experimental results of a three-phase 30-kW inverter are given to verify the proposed method. The proposed method is proved to be capable of islanding detection with balanced loads, motor loads within standard permissible detection times. The application of the proposed method to unbalanced loads is also discussed.
Junxi Wang - One of the best experts on this subject based on the ideXlab platform.
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broadband tunable microwave photonic phase shifter with low rf Power Variation in a high q aln microring
Optics Letters, 2016Co-Authors: Bing Xiong, Jian Wang, Lai Wang, Hongtao Li, Yun Zhang, Junxi WangAbstract:An all-optically tunable microwave photonic phase shifter is demonstrated based on an epitaxial aluminum nitride (AlN) microring with an intrinsic quality factor of 3.2×106. The microring adopts a pedestal structure, which allows overcoupling with 700 nm gap size and facilitates the fabrication process. A phase shift for broadband signals from 4 to 25 GHz is demonstrated by employing the thermo-optic effect and the separate carrier tuning technique. A phase tuning range of 0°–332° is recorded with a 3 dB radio frequency (RF) Power Variation and 48 mW optical Power consumption. In addition, AlN exhibits intrinsic second-order optical nonlinearity. Thus, our work presents a novel platform with a low propagation loss and the capability of electro-optic modulation for applications in integrated microwave photonics.
Gwonjong Yu - One of the best experts on this subject based on the ideXlab platform.
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a high Power quality anti islanding method using effective Power Variation
Solar Energy, 2008Co-Authors: Byunggyu Yu, Mikihiko Matsui, Junghun So, Gwonjong YuAbstract:Islanding phenomenon is undesirable because it leads to a safety hazard to utility service personnel and may cause damage to Power generation and Power supply facilities as a result of unsynchronized re-closure. In order to prevent the phenomenon, various anti-islanding methods have been studied. Until now, frequency or start phase shift methods of inverter current have much attention as active anti-islanding methods, which cause reactive Power Variation to the utility. However, these methods deteriorate usually the Power quality like Power factor or harmonic performance. This paper proposes a high Power quality active anti-islanding method using effective Power Variation, which is implemented by periodically increasing/decreasing Variation of inverter current magnitude. If it causes the large Variation of inverter output voltage after islanding, active frequency drift (AFD) method as a simple anti-islanding method will be injected into the inverter current for a designed period and islanding can be detected. In case of large voltage Variation when the grid is connected, AFD method will be removed after the designed period. Unlike most active anti-islanding method deteriorating Power quality, the proposed method will have high performance of islanding detection and good Power quality. For the verification of the proposed method, simulated results and experimental results in addition to analysis are presented using a 3 kW PV inverter.
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evaluation the non detection zone of anti islanding methods using reactive Power Variation method and active frequency drift method
International Conference on Performance Engineering, 2004Co-Authors: Gwonjong Yu, J H So, Youngseok Jung, Ju Yeop ChoiAbstract:Photovoltaic (PV) system has been increased around the world since PV system is becoming widespread as a clean and gentle energy source for earth. In the future, highdensity grid-connected PV systems will be interconnected with distribution network. As a result, the safety and stability of PV systems at islanding condition have become most important issues. To prevent islanding of PV inverter, several methods of islanding prevention has become widely researched and progressed. And especially, the one of method to detect islanding of PV inverter is existed reactive Power Variation (RPV) method and active frequency drift (AFD) method. However, there are no standardized test procedures for deciding the amount of reactive Power Variation, chopping fraction of output current in these prevention methods. Therefore, this paper proposes the optimal value of reactive Power Variation in RPV method and chopping fraction in AFD method to prevent islanding of PV inverter and is thoroughly investigated via simulation using PSIM.
Jun Zhang - One of the best experts on this subject based on the ideXlab platform.
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an improved islanding detection method for a grid connected inverter with intermittent bilateral reactive Power Variation
IEEE Transactions on Power Electronics, 2013Co-Authors: Jun Zhang, Dehong Xu, Guoqiao Shen, Ye Zhu, Ning HeAbstract:An islanding detection method for a grid-connected inverter incorporating intermittent bilateral (IB) reactive Power Variation (RPV) is described. The inverter output with IB reactive Power enables the detection of an islanding. The RPV range is derived in order to eliminate the nondetection zone. The design scheme of Variation time in the method is obtained by estimating the transient response due to islanding occurrence. In addition, the effect of the proposed detection strategy on Power quality is investigated. The proposed islanding detection method has been experimentally verified on a three-phase grid-connected 6-kW inverter.
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a novel rpv reactive Power Variation anti islanding method based on adapted reactive Power perturbation
Applied Power Electronics Conference, 2012Co-Authors: Dehong Xu, Jun Zhang, Guoqiao Shen, Ning He, Yangfan Zhang, Changsheng HuAbstract:In this paper, a novel intermittent reactive-Power-Variation (RPV) method based on loads’ resonance frequency detection is proposed to reduce the injected reactive Power. The RPV method detects the frequency of point of common coupling (PCC) and outputs the minimum reactive Variation, which perturbs the frequency of PCC to the frequency thresholds decided by the utility standards when the islanding condition happens. Furthermore, the islanding detecting control strategy under unbalanced loads condition is discussed. Compared with the traditional bilateral RPV method, the proposed method only output unilateral RPV in each Variation period and the Variation amplitude of each period is less than 5% of the output active Power $(P)$ , thus the perturbation of reactive Power can be reduced significantly. In addition, experimental results of a three-phase 30-kW inverter are given to verify the proposed method. The proposed method is proved to be capable of islanding detection with balanced loads, motor loads within standard permissible detection times. The application of the proposed method to unbalanced loads is also discussed.
Bing Xiong - One of the best experts on this subject based on the ideXlab platform.
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broadband tunable microwave photonic phase shifter with low rf Power Variation in a high q aln microring
Optics Letters, 2016Co-Authors: Bing Xiong, Jian Wang, Lai Wang, Hongtao Li, Yun Zhang, Junxi WangAbstract:An all-optically tunable microwave photonic phase shifter is demonstrated based on an epitaxial aluminum nitride (AlN) microring with an intrinsic quality factor of 3.2×106. The microring adopts a pedestal structure, which allows overcoupling with 700 nm gap size and facilitates the fabrication process. A phase shift for broadband signals from 4 to 25 GHz is demonstrated by employing the thermo-optic effect and the separate carrier tuning technique. A phase tuning range of 0°–332° is recorded with a 3 dB radio frequency (RF) Power Variation and 48 mW optical Power consumption. In addition, AlN exhibits intrinsic second-order optical nonlinearity. Thus, our work presents a novel platform with a low propagation loss and the capability of electro-optic modulation for applications in integrated microwave photonics.