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71.
Equivalent model of multi-type distributed generators under faults with fast-iterative calculation method based on improved PSO algorithm
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Puyu Wang Jinyuan Song Fangyu Liang Fang Shi Xiangping Kong Guangen Xie Xiao-Ping Zhang Xinxin Gu 《电力系统保护与控制》2021,6(3):371-382
There are various types of distributed generators (DGs) with diferent grid integration strategies. The transient char?
acteristics of the fault currents provided by the DGs are diferent to those of conventional synchronous generators. In
this paper, a distribution network with multi-type DGs is investigated, including consideration of DG low-voltage ride
through (LVRT). The fault current characteristics of two typical DGs, i.e. an inverter-interfaced distributed generator
(IIDG) and a doubly-fed induction generator (DFIG), are analyzed, considering the specifc operation modes. Based on
analysis of the fault characteristics, an equivalent model of the multi-type DGs under symmetrical/asymmetrical fault
conditions is established. A fast-iterative fault calculation method for enhancing the calculation efciency while avoid?
ing local convergence is then proposed using an improved particle swarm optimization (PSO) algorithm. A simula?
tion system of the distribution network with multi-type DGs is established in PSCAD/EMTDC. The simulation results
validate the high accuracy and calculation efciency of the proposed calculation method of the fault components.
This can assist in the settings of the protection threshold. 相似文献
72.
73.
Lei Ma Hongxia Lv Haonan Yu Lingtong Kong Rongyue Zhang Xiaoyan Guo Haibo Jin Guangxiang He Xiaoyan Liu 《中国化学工程学报》2021,33(5):286-296
A series of high oil-absorption resins with low cross-linking degree were synthesized by suspension polymerization using stearyl methacrylate(SMA), 2-Ethylhexyl methacrylate(EHMA), and styrene(St) as monomers.Response surface methodology(RSM) with central composite design(CCD) was also applied to determine the optimal parameters that are mainly known to affect their synthesis. Thus, the effects of the monomer mass ratio(EHMA:SMA), the rigid monomer(St) dosage, the porous agent(acetone) dosage, and their pairwise interaction on the resin's oil-absorption capacity were analyzed, highlighting PSES-R_2 as the resin with the optimum performance. The pure oil-absorption rates of PSES-R2 for gasoline, diesel, and kerosene were 11.19 g·g~(-1),16.25 g·g~(-1), and 14.84 g·g~(-1), respectively, while the oil removal rates from oily wastewater were 98.82%,65.11%, and 99.63%, respectively. 相似文献
74.
Shu Yan Fanyong Zhang Xue Feng Jian Kong Bo Wang Jinlong Yang 《International Journal of Applied Ceramic Technology》2021,18(3):817-829
A hierarchical porous cenosphere/geopolymer composite foam (FHCs/KGP) was fabricated by the simultaneous incorporation of O2 pore from hydrogen peroxide and cenosphere filler addition. Effects of both H2O2 content and high-temperature treatment on the microstructure, porosity and strength of porous FHCs/KGP foams were investigated systematically. The obtained FHCs/KGP foams showed typical amorphous structure and desirable porosity from 65 to 82%. The composites could crystallize in situ to FHCs/leucite foams above 1000℃. Compression strength of the FHCs/leucite foams showed a maximum value of 5 ± 0.3 MPa when treated at 1000°C. The improvement of mechanical properties for the composite foams was attributed to crack deflection, fractured microspheres and the good bond between the FHCs and matrix. This study could open opportunities to employ cellular foams as alternatives in structure and filtration applications. 相似文献
75.
Dongmei Hu Jin Du Guosheng Su Zhenyun Lu Chongyan Zhang Xiangmin Kong Chonghai Xu 《International Journal of Applied Ceramic Technology》2021,18(4):1222-1234
The hardness and toughness of regenerated cemented carbides, in general, are contradictory. Therefore, it is critical to explore regenerated cemented carbides with both high hardness and high toughness. In this study, regenerated WC-8-wt% Co cemented carbide with SiC nanowhisker were prepared by low-pressure sintering. The influence of SiCw contents on the microstructure and mechanical properties of regenerated WC-8-wt% Co cemented carbide was investigated. The results indicated that the hardness, density, flexural strength, and fracture toughness of regenerated cemented carbide first increased and then decreased with the addition of SiCw. The Vickers hardness, density, flexural strength, and fracture toughness could reach 1575 HV, 14.6 g/cm3, 2204 MPa, 16.85 MPa·m1/2, respectively, with SiCw content 0.5 wt%, which were increased by 14.4%, 0.7%, 12.2%, and 17.3%, respectively, when compared with the regenerated cemented carbide without SiCw. The lowest friction coefficient and the best wear resistance could be also reached when 0.5-wt% SiCw was added. The fracture mechanism of the regenerated cemented carbide contained both transgranular and intergranular fracture through the microscopic observation of fracture surface via scanning electron microscope. 相似文献
76.
Qiu Caihao Su Yishi Yang Jingyu Chen Boyang Kong Lingti Ouyang Qiubao Zhang Di 《Metallurgical and Materials Transactions A》2022,53(4):1308-1321
Metallurgical and Materials Transactions A - Precipitates including Al3Li, Al3Zr and core–shell structured Al3Li (Al3Zr) produce significant strengthening effects in Al-Li alloys by means of... 相似文献
78.
79.
The mechanism of color reversion in soybean salad oil 总被引:5,自引:0,他引:5
Ming-Tain Lai Woan-Meei Lin Yan-Hwa Chu Shih-Ling Y. Chen Kwan-Shean Kong Chieh-Wu Chen 《Journal of the American Oil Chemists' Society》1989,66(4):565-571
An enzymatic reaction might be the major cause of color reversion in soybean oil. During the soybean flaking process, enzymatic
reactions take place to convertγ-tocopherol to 5-(tocopheryloxy)-γ-tocopherol (γ-TED), and then further convertγ-TED to the precursors which are the cause of color reversion. The variations ofγ-tocopherol andγ-TED contents in soybean oil are accompanied by an inverse change in the precursors’ concentration. Therefore, the contents
ofγ-tocopherol orγ-TED in crude soybean oil could be used as an index for predicting the color quality (color reversion) of soybean salad oil.
Almost all the precursors (such as tocored) were converted to color-reverted substances under catalysis after bleaching treatment,
and they were converted back to the precursors during deodorization. Those precursors might be gradually reconverted into
the color reverted substances during storage to cause the color reversion in soybean salad oil. 相似文献
80.
In this paper, we have proposed a pentadiagonal alternating-direction-implicit (Penta-ADI) finite-difference time-domain (FDTD) method for the two-dimensional Schrödinger equation. Through the separation of complex wave function into real and imaginary parts, a pentadiagonal system of equations for the ADI method is obtained, which results in our Penta-ADI method. The Penta-ADI method is further simplified into pentadiagonal fundamental ADI (Penta-FADI) method, which has matrix-operator-free right-hand-sides (RHS), leading to the simplest and most concise update equations. As the Penta-FADI method involves five stencils in the left-hand-sides (LHS) of the pentadiagonal update equations, special treatments that are required for the implementation of the Dirichlet’s boundary conditions will be discussed. Using the Penta-FADI method, a significantly higher efficiency gain can be achieved over the conventional Tri-ADI method, which involves a tridiagonal system of equations. 相似文献