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- 저자 : Xueguang Zhang (검색결과 6 건)
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Improved Grid Voltage Control Strategy for Wind Farms with DFIGs Connected to Distribution Networks
Zhang, Xueguang,Pan, Weiming,Liu, Yicheng,Xu, Dianguo The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.3
This paper presents an improved grid voltage control strategy for wind farms with doubly-fed induction generators (DFIGs) connected to distribution networks based on an analysis of the operation limits of DFIG systems. A modified reactive power limit calculation method in different operation states is proposed and a reactive power control strategy during grid voltage dips/rises is further discussed. A control strategy for compensating unbalanced grid voltage, based on DFIG systems, by injecting negative sequence current into the grid through the grid side converter (GSC) is proposed. In addition, the negative current limit of the GSC is discussed. The distribution principle of the negative sequence current among the different DFIG systems in a wind farm is also introduced. The validity of the proposed voltage control strategy is demonstrated by Matlab/Simulink simulations. It is shown that the stability of a wind farm and the power grid can be improved with the proposed strategy.
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Improved Grid Voltage Control Strategy for Wind Farms with DFIGs Connected to Distribution Networks
Xueguang Zhang,Weiming Pan,Yicheng Liu,Dianguo Xu 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.3
This paper presents an improved grid voltage control strategy for wind farms with doubly-fed induction generators (DFIGs) connected to distribution networks based on an analysis of the operation limits of DFIG systems. A modified reactive power limit calculation method in different operation states is proposed and a reactive power control strategy during grid voltage dips/rises is further discussed. A control strategy for compensating unbalanced grid voltage, based on DFIG systems, by injecting negative sequence current into the grid through the grid side converter (GSC) is proposed. In addition, the negative current limit of the GSC is discussed. The distribution principle of the negative sequence current among the different DFIG systems in a wind farm is also introduced. The validity of the proposed voltage control strategy is demonstrated by Matlab/Simulink simulations. It is shown that the stability of a wind farm and the power grid can be improved with the proposed strategy.
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An Improved Control Strategy Based on Unified Impedance Model of DFIG under Weak Grid
Yage Zhang,Xueguang Zhang,Ran Fang,Dianguo Xu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposes a grid voltage disturbance compensation control to improve the stability of the DFIG system under weak grid condition. A detailed impedance model of the DFIG system is developed in the d-q frame. Based on the proposed model, the relationship between the outputs of the controllers and the grid voltage disturbance at PCC can be obtained. Then, the compensation control of the grid voltage disturbance are integrated to the current control loops of RSC and GSC to improve the stability of the DFIG system connected to the weak grid. In this paper, the effective of the proposed compensation control is proved through the GNC, which illustrates that the compensation control implemented in RSC and GSC simultaneously has a better ability to maintain the stability of the DFIG system under weak grid condition than the only one side used. The simulation results verify the analysis.
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Sida Fu,Xueguang Zhang,Dianguo Xu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
The three-phase grid-connected converter control system and the grid impedance are coupled with each other under weak grid conditions, which brings in negative influence on the system. In this paper, the impedance model of a three-phase grid-connected converter including current loop, PLL and DC voltage loop is established in d-q frame. The influence of PLL and DC voltage loop proportional coefficient on system stability is analyzed. According to the transfer relationship of each variable in the impedance model, the PCC voltage perturbation paths to the PLL and DC voltage loop are analyzed respectively. On the basis of voltage perturbation paths, a compensation control strategy is proposed. The impedance analysis results show that the proposed method can effectively improve the system stability under weak. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed method.
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Expanded Android Application for Openflow-based Visual Interface in Software-Defined Network
Xuejun Tao,Xueguang Yuan,Yan Hong,Yang’ An Zhang 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.6
In the past year, the northbound interface application has become a hot topic in the Software-Defined Network technology. It offers an opening method and makes people able to develop own business application upper the SDN. In this paper, we propose and evaluate a visual plane based on android phone application to present an explicit watch of the state and working performance of the Openflow-based underlying network topology in Software-Defined Network. The impacts of the designing architecture are evaluated in the form of software simulation and actual operating effects of the android application that we have designed. Through the interface opened by the floodlight controller to the upper business application, we are aimed at making it able to call the underlying network resources and inquiry its status information conveniently. So this paper wants to achieve the unified dispatching by elaborated methods and transplants the idea to the android application. By the way of the software programming, we could make the android phone to probe the southbound network resources through the northbound interface whose connotation we will expand. Between the northbound interface and the android application, we introduce a data center and select the mysql database to implement its function. Through the technology framework we built, we are able to use an android phone to access the status of the underlying devices and monitor the software defined network better aiming at providing better service. And we judge its function from the perspective of overall feasibility and stability not only through the system performance but also sound experiment effects. Finally, we can use any android phone to view about the topology of the network effectively and simply.
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Yang Lu,Shuxin Liu,Shujia Zhang,Guangyan Cai,Hongwei Jiang,Huabin Su,Xiaofan Li,Quan Hong,Xueguang Zhang,Xiangmei Chen 한국분자세포생물학회 2011 Molecules and cells Vol.31 No.3
Tissue inhibitor of metalloproteinase-1 (TIMP-1) plays various roles in cell growth in different cell types. However, few studies have focused on TIMP-1’s effect on fibroblast cells. In this study, we investigated the effects of TIMP-1 overexpression on NIH3T3 fibroblast proliferation and potential transduction signaling pathways involved. Overexpression of TIMP-1, by transfection of the pLenti6/ V5-DESTTIMP-1 plasmid, significantly promoted NIH3T3 proliferation as determined by the BrdU array. Neither 5 nor 15 nM GM6001 (matrix metalloproteinase system inhibitor) affected NIH3T3 proliferation, but 45 nM GM6001 inhibited proliferation. TIMP-1 overexpression activated the p-Akt pathway, but not the p-ERK or p-p38 pathway. In TIMP-1-transfected cells, cyclinD1 was upregulated and p21CIP1 and p27^(KIP1) were downregulated, which promoted cell entry into the S and G2/M phases. The PI3-K inhibitor LY294002 abolished the TIMP-1-induced effects. Overexpression of intracellular TIMP-1 stimulated NIH3T3 fibroblast proliferation in a matrix metalloproteinase (MMP)-independent manner by activating the p-Akt pathway and related cell cycle progression.
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