几种特殊输电方式的分析比较和展望

除交流输电和传统高压直流输电(HVDC)以外,在某些特定情况下需要采用特殊的输电方式,主要包括轻型HVDC(HVDC Light)、分频输电(FFTS)、多相输电(MPTS)、微波输电、激光输电等。为充分发挥上述各种输电方式的独特优势,综合分析比较了它们的原理、特点、优势、难点及当前研究发展情况,指出各自的适用领域,展望它们的发展前景。其中,FFTS和MPTS从属于交流输电方式,主要应用于长距离大容量输电,轻型HVDC、微波输电和激光输电从属于直流输电方式,主要应用于特殊场合输电,而轻型HVDC已有较成熟的工业应用线路,且其交直流转换技术的发展可作为MTE和激光输电的技术基础,因此轻型HVDC的研究和发展具有重要的意义。

新型输变电技术研究综述

综述了国内外学术界和工程界在新型输变电技术领域的研究和发展状况。通过对各种新型输变电技术特点的阐述和分析,总结了它们各自的特点和发展前景,并着重介绍了多项输电和四相输电技术的起源和发展,初步探讨了其在我国的应用前景。

Effect of Arc Energy on Morphology and Microstructure of Laser-MIG Hybrid Welded Joints of Invar Alloy

Laser-MIG hybrid welding experiments of 7 mm thick Invar alloy are carried out.The macro appearance of joints is observed and the influence of arc energy on the cross-section morphology is analyzed.The distribution of temperature field is simulated to explain the relationship between heat effect and microstructure.Besides,the average grain size of weld under different arc energies is quantitatively studied.The results indicate that welded joints with uniformity and good formation are obtained.The weld width and the weld seam area increase and the depth to width ratio decreases with the increase of arc heat input.The transition of columnar crystals to equiaxed crystals is observed from the fusion line to the weld center.It is found that the higher the arc energy,the coarser the columnar crystal.

Multielectrode Semiconductor Lasers

Multielectrode semiconductor lasers are studied via the ray method.The expression of the output photon number of N -electrode semiconductor lasers has been derived for the first time.When N =1 or 2,the expression of the output photon number fits in that of one-electrode (general) or two-electrode semiconductor lasers perfectly.