一种适用于配电网的新分布式潮流控制器拓扑

常规分布式潮流控制器(DPFC)需通过3次谐波电流以实现串联侧与系统的有功功率交换,串联侧所在支路首末端分别需△/YN、YN/△联结型变压器,因此在配电网中的安装地点受到一定限制.为此该文提出一种适用于配电网的新DPFC(NDPFC)拓扑;分析NDPFC工作原理,应用配电网典型系统验证其潮流调节范围与调控特性;此外,研...     

Spinel CoFe2O4 /carbon nanotube composites as efficient bifunctional electrocatalysts for oxygen reduction and oxygen evolution reaction

In the development of fuel cells, it is the key to large-scale commercialization of fuel cells to rationally design and synthesize efficient and non-noble metals-based bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this paper, spinel CoFe₂O₄/carbon nanotube composites (CoFe₂O₄/CNTs/FA) were synthesized by solvothermal and calcination method. XRD, TEM, XPS and BET characterizations indicate that the addition of complexing agent fumaric acid can improve the crystal growth kinetics and morphology of CoFe₂O₄/CNTs nanohybirds. The as-synthesized CoFe₂O₄/CNTs/FA pyrolyzed at 500 °C have an outstanding bifunctional catalytic activity for ORR and OER with the potential of 1.62V (vs. RHE) at a current density of 10 mA/cm² and half-wave potential E_1/2 = 0.808V (vs. RHE) in alkaline electrolyte, respectively. It is obviously better than unloaded CoFe₂O₄ nanoparticles and commercial CNTs. CoFe₂O₄/CNTs/FA also exhibit better methanol tolerance ability and durability than commercial Pt/C and RuO₂ catalyst. This investigation broadens an idea of simple compounding of spinel with carbon-based materials to improve electrochemical properties.     

Characterizing bubble behavior in a pseudo-2D fluidized bed of wet particles

By applying digital image analysis on the bubble characteristics in a two dimensional wet-particle fluidized-bed, we report two-stage evolution of bubble characteristics with increasing liquid content. In the first stage, bubble number and uniformity of bubble fraction increase, while bubble average diameter and aspect ratio decrease. In the second stage, these characteristics shift toward an opposite direction. This two-stage evolution of bubble characteristics are analogous to that of reducing particle size in dry-particle fluidization, and the fluidizing properties of particles shifts from Geldart Group B to Group A and then to Group C. Furthermore, liquid addition causes a continuous decrease of bubble fraction and bubble flow rate. This is different from dry-particle fluidization, in which reducing particle size causes an increase trend. An explanation for this difference is that liquid addition increases the equivalent size of agglomerates in wet-particle fluidization, which is opposite to the effect of reducing particle size.     

河道一维非恒定流数值模拟深化研究

传统的河道一维非恒定流数值计算一般采用特征线法和以Preissmann方法为代表的有限差分法.特征线法计算精度比较高,但受时间步长的限制,用于河道一维非恒定流计算时计算效率却不太高.而Preissmann方法相比特征线法计算效率有所提高,但在求解过程中特征量的守恒性却没有做出相应要求.为了兼顾数值计算的效率和特征量的守恒,建立了基于有限体积法的河道一维非恒定流数值计算方法,并分别选取淮河干流洪水和史灌河洪水进行了验证计算,验证计算成果表明所采用的方法特征量守恒性较好,洪峰水位计算值与实测值吻合也较好,可用于河道一维非恒定流计算.     

交错并联磁集成开关电感高增益Boost变换器

为了提高Boost变换器电压增益、减小支路电感电流纹波、减弱开关管电压应力、减小变换器体积,提出了一种新型带有开关电感及开关电容的交错并联磁集成Boost变换器.相对于传统交错并联Boost变换器而言,利用2个开关电感单元代替储能电感,2个电容及4个二极管构成开关电容,对所提出的拓扑进行理论分析、仿真及实验验证.结果表...     

铅酸蓄电池化成策略和实践

以降低铅酸电池化成能耗为出发点,对电池相关信息进行分析,提出了降低化成充电量的策略,并进行了实践.结果显示12 V 20 Ah电池充电量降低24 Ah,相对原工艺降低13.56％.实践证明,优化后化成策略可以有效降低铅酸蓄电池化成的能耗,降低企业生产成本.     

特高压与超高压交流输电技术节能降耗比较研究

随着特高压交流技术的成熟应用,在面对主网架加强优化问题时,1000 kV与500 kV交流方案的综合比选显得尤为重要.为了获得经济最优,需对比特高压与超高压交流输电技术的节能降耗水平,因此针对1000 kV和500 kV交流输电技术,分析了交流输电损耗的构成、基本原理和计算方法,然后分别计算特高压交流与超高压交流的线路损耗、变压器损耗和站用电并折算成损耗率,从而分析1000 kV和500 kV交流输电技术节能降耗水平.     

Effect of microstructure inhomogeneity on hydrogen embrittlement susceptibility of X80 welding HAZ under pressurized gaseous hydrogen

Hydrogen embrittlement (HE) of high-grade pipeline welded joint is a threat to hydrogen gas transport. In this research, slow strain rate tension (SSRT) tests in high-pressure hydrogen gas, combined with hydrogen permeation tests and microstructure analysis were conducted on X80 steel, intercritical heated-affected zone (ICHAZ), fine-grained heat-affected zone (FGHAZ) and coarse-grained heat-affected zone (CGHAZ). The change of HE susceptibility from high to low was CGHAZ, FGHAZ, ICHAZ, and base metal. Microstructure was the important factor influencing hydrogen permeation and susceptibility to HE. Susceptibility to HE was increased in the order of “fine-grained massive ferrite (MF) and acicular ferrite (AF)”, “fine-grained granular bainite (GB) and MF”, “coarse-grained GB and bainite ferrite (BF) embedded with martensite-austenite (M-A) constitute”. The fine-grained MF and AF in base metal with lower hydrogen diffusivity can impede the embrittlement behaviour, while the coarse-grained GB and BF with higher hydrogen diffusivity in CGHAZ increased its susceptibility to HE.     

半绝缘衬底上Si掺杂InP的纳米孔腐蚀与电学性质研究

利用MOCVD在InP半绝缘衬底上生长N型InP,在KOH溶液中电化学腐蚀形成纳米多孔结构的。通过实验证实在半绝缘衬底上的InP纳米孔腐蚀具有可行性,并且得到了腐蚀质量较好、图形清晰、结构规整的纳米孔材料。在对其进行霍尔测试,得到了腐蚀孔对于n型InP材料表面电学性质的改变,实现了低掺杂浓度(10~(18)cm~(-3))的InP通过表面纳米孔腐蚀的方式提高载流子浓度,改善n型InP层表面电学性能。