柔性直流配电技术的发展与现状

本文通过与交流配电网的对比,结合高压直流输电技术的发展,分析了柔性直流配电网的技术优势,并进一步对目前柔性直流配电研究中诸如电压等级、拓扑结构、关键设备、控制保护等关键技术进行了分析,结合中国目前已有的典型示范工程,对柔性直流配电技术的研究现状、重点方向进行了介绍。     

湖北电网2021年220 kV及以上电压等级继电保护设备运行情况分析

继电保护作为电力系统的第一道防线,是电力系统的重要组成部分。着重对2021年湖北电网保护装置微机化、国产化、设备运行年限、保护正确动作率、继电保护设备缺陷异常情况等方面作了细化分析,全面总结了2021年湖北电网220 kV及以上系统继电保护装置规模和运行情况,对近3年来220 kV及以上继电保护有关指标的变化趋势进行了深入分析。     

变比测试仪在电容式电压互感器测试中的使用及问题处理

电压互感器变比的准确与否直接影响电量计量及保护的准确性,而电容式电压互感器在变电系统设备的测量、保护中有着广泛的使用.介绍了三相变比组别测试仪在测试电容式电压互感器中的应用,阐述了在现场测量中出现的问题和解决方法.     

Upconversion of Er^3＋ Ions in LiKGdF5 ： Er^3＋ , Dy^3＋ Single Crystal Produced by Infrared and Green Laser

The upconversion fluorescence of Er^3＋ ions in LiKGdF5 ： Er^3＋, Dy^3＋ single crystal was studied under 785, 514.5, and 980 nm laser excitation. With the laser excitation set at 785 nm, strong green （centered at 543 nm） upconversion emissions, as well as weak red （651 nm）, violet （406 nm）, and blue （470 nm） upconversion emissions were obtained. With 514.5 nm laser excitation, violet （406 nm） and blue （470 nm） upconversion emissions were observed. Under 980 nm laser excitation, strong green （543 nm） and weak red （651） emissions were also obtained. The laser power dependence of the upconverted emissions was investigated to understand the upconversion mechanism. The excited state absorption （ESA） and the energy transfer （ET） processes were discussed as the possible mechanisms for all upconversion emissions.     

逆变器并联系统直流环流瞬时抑制策略

为有效减小逆变器并联系统中直流环流的危害,通过对直流环流进行分析,提出了一种基于改进重复控制的直流环流瞬时抑制策略。该策略将重复控制的补偿周期设为载波周期,以解决传统重复控制动态响应特性差的问题。逆变器输出电压直流分量具有波动性,因此以载波周期为单位对其进行计算,并将计算结果作为反馈与比例积分(PI)控制一起调整正弦脉冲宽度调制(SPWM)占空比,以实现对逆变器并联系统直流环流的瞬时抑制。模拟并联系统半波负载突变实验表明,在加载半波负载前后,逆变器输出电压直流分量可以分别被抑制到0.02%～0.03%和0.04%～0.05%,补偿延时可控制在40 ms以内。实验结果表明,提出的策略能够有效提高逆变器输出电压直流分量的补偿精度和并联系统直流环流抑制的动态响应特性。     

Synthesis and luminescent properties of Pr-doped Lu3Al5O12 translucent ceramic

Lutetium aluminum garnet (LuAG) precursors doped with different Pr3+ concentration (0.25at.%, 0.5at.%, 1.0at.%, 3.0at.%, 5.0at.%) were synthesized via a co-precipitation method using ammonium hydrogen carbonate as precipitant. The phase evolution and mor-phology of the precursor were characterized with X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The resultant LuAG:Pr3+ powder was sintered into translucent ceramic without any additives in vacuum at 1150℃ and then in nitrogen atmosphere at 1700℃. Photohiminescence spectra of LuAG:Pr3+ powder and ceramic were measured at room temperature in vacuum ultraviolet (VUV) and ultraviolet (VU) region. For the 5d-4f transition of Pr3+ ions, dominant emission of ceramic samples peaking round 311 nm had higher lumines-cence intensity. And the host absorption in ceramic samples was not as intensive as that in powder samples. The luminescent intensity of LuAG:Pr3+ varied with the Pr3+ contents and the quenching concentration was about 1.0at.% for ceramic and 3.0at.% for powder, which was much higher than 0.24at.% for LuAG:Pr3+ single crystals. This phenomenon showed that the ceramic had some superiority over single crystals.     

面向问题的CL排版语言及其实现

CL(Computer Laser的缩写)语言是用于中文书报排版的专用语言。本文介绍了CL语言的特点及其编译程序结构。CL编译程序具有自动换行、自动换页、处理表格等较强的功能,它的分层的模块结构给编制与调试这一大型程序带来方便。本文还简略地从用户观点介绍了经过软件改造后的计算机-激光汉字编辑排版系统。     

低温固相合成牙用白榴石

以钾长石、碳酸钾等为主要原料,固相合成白榴石晶体.通过实验发现提高配方中碱性氧化物K2O的含量,减低酸性氧化物SiO2的含量可以显著减低白榴石的合成温度.实验表明按照白榴石的化学组成进行配比时,配方在1100℃就完全转化成白榴石,比传统白榴石的转化温度减低了约100℃,其在1100℃下合成时热膨胀系数为27.9×10-6/K(30-700℃),平均晶粒尺寸为15μm.     

利用三维矢量线条实现版画设计

设计了一种粗细变化的三维矢量线条,赋予了线条灵活的变化,可以改变局部的线宽、线条局部的走向和扭曲度等,并利用矢量线条的粗细变化来体现图像的灰度层次,从而达到模拟传统版画的效果;同时,给出了一种由曲线混合生成一定数目线距均匀曲线组的方法。