利用有功功率扰动的微网孤岛下垂控制策略

对于孤岛模式运行的微网中的并联逆变器,其功率分配主要受逆变器输出阻抗和输出端与公共连接点之间线路阻抗差异的影响。以感性输出阻抗为例,从逆变器并联的功率传输特性出发,分析了线路阻抗差异对并联逆变器无功功率分配的影响。为了提高无功功率的均分精度,提出了一种改进型下垂控制策略,在有功频率下垂中加入无功功率,利用有功扰动反映无功分配偏差,在无功幅值下垂中加入可调下垂系数,通过消除有功扰动调节下垂系数补偿线路阻抗差异实现稳态时无功均分。仿真和实验验证了改进下垂控制策略的正确性和有效性。     

间隔层保护测控装置防误操作实现方法

间隔层保护测控装置防误操作已成为变电站综合自动化系统的必要功能。文中阐述了一种在监控后台用脚本语言编写五防规则,在间隔层保护测控装置安装脚本引擎,下装五防规则库到装置,从而实现间隔层保护测控装置防误操作的方法。详细描述了脚本语言和脚本编译器的设计方法,在监控后台实现五防规则的编译和安全测试。     

一种七自由度仿人手臂动力学仿真分析

借助于adams动力学仿真工具,分析了一种新研制的七自由度仿人手臂的动力学问题,并以仿人手臂的自运动为例,求出了随动控制下的力矩响应。进而,利用三次样条插值的办法,得出了时间一力矩函数关系式,显然,这为力矩补偿前馈控制模式提供了数学模型。     

垂直布里奇曼法生长的Cd0.8 Mn0.2Te单晶体中Te沉淀相分析

Cd1-xMnxTe（CdMnTe,CMT）是制备光学隔离器、太阳能电池、x射线和γ射线探测器的优选材料。本实验采用垂直布里奇曼（VB）法成功地生长出Cd0.8Mn0.2Te单晶体。用JEM-3010型高分辨透射电子显微镜（HRTEM）观察了CMT晶体中的纳米级Te沉淀。选区电子衍射得到了Te沉淀与CMT基体两相的合成电子衍射图。计算出单斜Te沉淀的晶胞参数为：a=0.31nm,b=0.79nm,c=0.47nm,β=92.71°。确定了Te沉淀和CMT基体的取向关系为（0 31）Te//（202）CMT,[100]Te//[111]CMT。最后,对Te沉淀（缺陷）的形成原因进行了分析。     

Synthesis and electrical field-assisted sintering behaviour of yttria-stabilized tetragonal ZrO<Subscript>2</Subscript> nanopowders by polyacrylamide gel method

The tetragonal ZrO₂ nanopowders stabilized with 3 mol% Y₂O₃ (3YSZ) were synthesized using a polyacrylamide gel method. The mean particle size of the 3YSZ nanopowders was found to decrease with increasing molecular ratio of monomer to the precursor salt. The 3YSZ nanopowders with mean particle size of 12 nm can be densified in 1 h at 800^°C, by the application of a d.c. electrical field. Under a constant d.c. electrical field, the current density through the specimen of 3YSZ rose rapidly when the temperature increased to a certain value. In the sintering process, the current density was restricted when the sharp increase occurred. By limiting current density to different values for one hour, it was found that current density was the most important factor in electrical field-assisted sintering process. The grain size of 3YSZ bulk increased with the enhanced current density. The stable stage of electrical field-assisted sintering process can be explained by Joule heating. Corresponding real temperature of specimens is estimated by applying black body radiation theory.     

Facile synthesis of Au/ZnO nanoparticles and their enhanced photocatalytic activity for hydroxylation of benzene

Au/ZnO nanocomposites have been prepared by a simple chemical method. For the first time, the nanocomposites were directly used as photocatalysts for hydroxylation of aromatic hydrocarbons under UV and visible light irradiation. The results show that the as-prepared photocatalysts display high photocatalytic activity for UV and visible catalytic hydroxylation of benzene. Without the assistance of any solvent or additive, high selectivity and high conversion efficiency were still obtained. Different photocatalytic mechanisms were proposed depending on whether excitation happens on ZnO semiconductor or on the surface plasmon band of Au. The former is Au nanoparticles act as electron buffer due to irradiation by UV light and ZnO nanoparticles as reactive sites for hydroxylation of benzene, the latter is that Au nanoparticles act as light harvesters and inject electrons into ZnO conduction band and as photocatalytic sites under visible light irradiation.     

GITT studies on oxide cathode LiNi1/3Co1/3Mn1/3O2 synthesized by citric acid assisted high-energy ball milling

Layered LiNi_1/3Co_1/3Mn_1/3O₂ was synthesized by a citric acid assisted solid-state method. The structure and electrochemical properties of the LiNi_1/3Co_1/3Mn_1/3O₂ materials were investigated. XRD analysis indicated the as-synthesized LiNi_1/3Co_1/3Mn_1/3O₂ was with the layered α-NaFeO₂ structure. The discharge capacity was about 154 m·Ahg^???1 at 0·1 °C rate in the range of 2·0–4·5 V. The kinetics of the LiNi_1/3Co_1/3Mn_1/3O₂ materials was investigated by the galvanostatic intermittent titration technique (GITT) method. The lithium ion diffusion coefficient of the LiNi_1/3Co_1/3Mn_1/3O₂ was determined in the range of 10^???8??? 10^???9 cm²· s^???1 as a function of voltage of 3·7?4·5 V.