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Liu J.,Shaanxi Electrical Power Research Institute | Huang W.,Xian University of Science and Technology
Dianwang Jishu/Power System Technology | Year: 2015

To offer reasonable foundation for the planning of grid-connection of distributed photovoltaic (PV) generations, the mathematical models for voltage deviation and voltage fluctuation caused by various distributions of loads and PV generations are established. Taking the maximum upper deviation of voltage and the maximum voltage fluctuation caused by distributed PV generations and the maximum lower voltage deviation caused by the load only when the PV generation does not exist as constraints, the capacity range of allowed grid-connected distributed PV generations, by which the demand on voltage quality can be met under six distribution conditions of load and distributed PV generations along the feeder, is derived. Taking typical parameters of urban distribution network and those of rural distribution network for example, the proposed method is analyzed and illustrated, results of the analysis show that the proposed method is feasible, and using the proposed method the allowed grid-connected capacity range of distributed PV generations can be determined. ©, 2015, Power System Technology Press. All right reserved. Source


Chen X.,Hohai University | Chen K.,Nanjing Pengtu Power Supply Co., Ltd | Liu J.,Shaanxi Electrical Power Research Institute | Ding X.,China Electric Power Research Institute | Yu K.,Hohai University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

The energy balance mode in the distribution network is changed after the distributed generation, microgrid, energy storing device and charge-discharge device of electric vehicles are inserted in the grid. To promote the development of the smart grid, the objectives and devices for the intelligent dispatch of the distribution network are presented following an analysis of the characteristic of the distribution network and its dispatching and control. A multi-dimensional and multi-stage progressive intelligent dispatching mode for the distribution network based on the interaction between the network, power supply and loads are proposed to achieve the goal of efficient operation of the distribution network. And the functional structure of intelligent dispatching of the distribution network is provided. The key techniques to be solved are presented to complete the intelligent dispatching system of the distribution network. The developing tendency for the intelligent dispatching of the distribution network is explored and the research direction summed up. © 2012 State Grid Electric Power Research Institute Press. Source


Wang J.,Xian University of Science and Technology | Feng L.,Xian University of Science and Technology | Feng Y.,Xian University of Science and Technology | Yan A.,Shaanxi Electrical Power Research Institute | Ma X.,Northwestern University
Polymer - Plastics Technology and Engineering | Year: 2012

Five kinds of organic rectorite (OREC)-reinforced Epoxy Resin (EP) composites (OREC/EP) were prepared by using different ORECs as modifiers. The curing process of EP, the functional groups of OREC and its interlayer distance (d-spacing) are demonstrated by Fourier Transform Infrared Radiation (FTIR) and XRD (X-Ray Diffraction). The morphologies of OREC/EP composites and the dispersion of OREC in the cured EP matrix were investigated using XRD and scanning electron microscopy (SEM). The mechanical properties, thermal deformed temperature (HDT), hot-wet resistance, alkali resistance and water adsorption of the resulting OREC/EP composites were evaluated. It is found that the addition of OREC can improve the comprehensive properties of EP. The maximum mechanical properties of OREC/EP can be obtained by OREC3/EMI-2, 4/E-51 due to the high stiffness and uniform dispersion of OREC in matrixes. The most desirable properties of OREC/EP composites were obtained with impact strength of 9.5 kJ/m2, bent strength of 86 KPa and HDT of 182°C, all of which is improved by 8.0%, 8.9% and 28.2% than those of pure EP, respectively. © 2012 Copyright Taylor and Francis Group, LLC. Source


Liu J.,Shaanxi Electrical Power Research Institute | Si Y.,Xian University of Technology
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

To help better evaluate the safety and utilization of distribution networks, a linear programming-based approach to obtaining the maximum utilization ratio of distribution systems with arbitrary topologies and capacities is put forward. A series of safety indices considering load variation are proposed, including the real-time utilization ratio, real-time shortage ratio, averaged utilization ratio, averaged shortage ratio, N-1 criterion meeting to duration ratio, N-1 criterion meeting, N-1 criterion meeting risk, and regulating ratio of N-1 criterion meeting critical load. The steps of evaluation are suggested. Several examples are given to illustrate typical applications of the approaches proposed showing that it is feasible and can provide more information to planning, operation and engineering of distribution systems. It is also shown that the indices of utilization and extent for meeting N-1 criterion can be improved by optimizing the allocation of the sectionalizing switches on the feeders. © 2011 State Grid Electric Power Research Institute Press. Source


Liu J.,Shaanxi Electrical Power Research Institute | Lin T.,State Grid Corporation of China | Tong X.,Xian University of Technology | Li L.,State Grid Corporation of China | Zhang Z.,Shaanxi Electrical Power Research Institute
Dianwang Jishu/Power System Technology | Year: 2013

To address the challenge due to connecting distributed photovoltaic (PV) generation to distribution network, based on the circuit topology of grid-connecting inverter of PV generation and its control strategy the simulation analysis on variation of output current characteristics of grid-connecting inverter under three-phase short-circuit fault and interphase short-circuit fault occurred in distribution network as well as that under different output of distributed PV generation are performed; meanwhile, the simulation analysis on variation of output current characteristics of grid-connecting inverter under open-circuit of insulated gate bipolar transistor (IGBT) device of the inverter and single-phase disconnection fault occurred in AC side are carried out. All simulation results show that whether three-phase fault or interphase fault occurs in distribution network, the short-circuit current output by grid-connecting inverter does not exceed 1.5 times of its rated current, and the approaches to cope with fault occurred in the inverter itself are put forward. Source

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