Papers by Author: Lin Zhang

Abstract: SVG can compensate reactive power deficiency, suppress harmonics, improve three-phase imbalance and power quality more flexibly. There are very few small volume SVG products available for low voltage distribution network in the past. The generic SVG products are very expansive, thus not suitable for low voltage distribution network. Therefore, it is an urgent task to design a new generation distribution network SVG product that offers good value for money. This paper studied a SVG digital controller based on TMS320F28335 DSP chip. The fast and powerful computing and parallel operation capability of TMS320F28335 can satisfy the real-time, multifunction and multiple objective coordination control of SVG. Applied the instantaneous reactive power theory and adopted current direct control mode, an enhanced filtering algorithm to filter instantaneous sampling value is proposed. Automatic bi-directional compensation control strategy effectively reduced voltage variation at the user side. Its effectiveness is verified by an engineering project.

Abstract: The Al-Mg-B polycrystalline bodies were prepared using vacuum hot-pressing sinter method by pure Al, Mg and B powders. Process parameters and constitution variation were investigated to obtain compact Al-Mg-B sintered body with high mechanical properties. Al-13%Mg-72.7%B(weight ratio) sintered body prepared under 1600°C, 30MPa for 1 hour in vacuum was proved to be optimum, which bending strength was 156MPa and Vickers hardness was 2220. X-ray diffraction (XRD), Micron Probe Micro-analyzer (EPMA) were employed to analyse the ultimate phases. The results showed that the matrix phases were metal borides including AlB12, MgB6 and AlMgB14, while Al2O3 and MgAl2O4 phases existed which connected or filled in the matrix grains to promote the compactness degree, where oxygen introduced from impurities in raw materials. A portion of Mg in AlMgB14 combined with oxygen during heating to 1600°C which helped to form MgAl2O4 and AlB12 in the end.

Abstract: Nanostructured Lanthanum hexaboride (LaB6) powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectra (XPS). The average size of LaB6 nanoparticles is about 35nm, which are well crystallized with ball or ellipsoid with inconspicuous corners and covered by a 3-5nm thick amorphous layer containing oxygen and carbon. The absorption of LaB6 nanoparticles in visible and near infrared spectrum (NIR) was measured and compared with micron scale particles. The surface plasmon responance (SPR) of nanoparticles was very efficient at NIR blocking, which almost covered the whole NIR region. The influence of nanoparticles concentration on spectrum absorption was comparatively evident. Meanwhile, micron particles almost haven’t NIR blocking function.

Abstract: The Al2O3-TiC/Al composites were prepared by injecting CO2 gas into Ti contained Al-Si alloy melts. The microstructure of the composites was examined by XRD, SEM and TEM. It was indicated that both Al2O3 and TiC particles can be formed by the in situ reaction of CO2 with Ti and Al in the melten alloys. The Al2O3 and TiC particles in size of 0.3~1.5μm distributed uniformly in the matrix. The volume fraction of the particles is mainly depend upon the time of CO2 injection.The tensile strength at room temperature of the composites can reach 346.08MPa and the hardness is 149.6MPa HBS, repectively, which are higher than those of the matrix alloy.

Abstract: Based on the CaCO3-B4C-C system to prepare calcium hexaboride (CaB6) powder, the influence of B4C size on the CaB6 powder was investigated in this paper, in which micro-sized B4C in various size and nano-sized CaCO3 were as main raw materials. XRD and SEM were used to characterize the phase pattern, size and morphology of CaB6 powder particles respectively. Laser particle size analyzer was employed to determine the size distribution of CaB6 particles. It was found that the size of B4C had a dominant effect on the size and distribution of CaB6 powder particles. When B4C particles were much coarser than CaCO3, the CaB6 synthesized appeared as aggregates which size relied on B4C, however, the size of every CaB6 particle was determined by CaCO3. When B4C particles size was fine to several microns, the CaB6 particles synthesized were dispersive and the size of them has great relation to B4C. Synthesis models were also established to describe various reaction processes.