基于智能软开关的三相不平衡配电网动态重构策略

针对单相分布式电源（DG）的接入会加剧配电网不平衡程度、增大网络损耗,且在严重不平衡时影响系统安全运行的问题,提出计及智能软开关（SOP）的三相不平衡配电网动态重构策略。首先,构建考虑SOP和DG电流不平衡度约束的三相不平衡配电网动态重构模型;然后,针对模型的非凸性将原模型转化为混合整数线性规划模型;最后,对改进的IEEE34节点配电网和某地78节点实际配电网进行算例分析,结果表明所提模型和策略可在保证配电网的安全运行的同时提升配电网的经济效益。     

一种新型MMC并联双端口子模块及其三阶段故障电流阻断机理

为使模块化多电平换流器(modular multilevel converter,?MMC)具备直流故障自清除能力和电容电压均衡能力,提出了一种新型并联双端口子模块：钳位双全桥子模块(clamp double full bridge submodule,?CD-FBSM)。该子模块器件成本和运行损耗较低,正常工作时相邻子模块之间具有多种协同运行模式,通过特有的并联模式可提高电容电压均衡度。故障闭锁时,模块内部电容并联、模块之间电容串联且反向接入电路,能够可靠阻断故障电流并均衡电容电压,有利于系统快速重启。此外,提出了三阶段故障电流阻断机理分析方法,对CD-FBSM的故障电流阻断过程进行了研究。通过Matlab/Simulink的仿真结果表明,所提子模块电容电压均衡度较高,可快速阻断故障电流,且故障电流阻断过程与理论分析一致。     

基于空充暂态电流的线路保护CT极性校验方法

线路保护电流互感器(current transformer, CT)二次采样回路接线正确是保护正确动作的前提。针对线路投运启动过程中保护CT极性校验困难的问题,首先分析了在有限负荷和无负荷下利用线路稳态电流进行极性校验的边界限制条件。进而针对不满足限制条件下无负荷极性校验困难的问题,提出了一种基于空充暂态电流的线路保护CT极性校验方法。该方法先利用幅值较大的本端暂态电流对三相CT相对极性进行初判,再通过线路本端暂态电流和测量电压基于线路结构计算对端暂态电流来实现本端保护CT极性错误相识别,CT极性正确时对端计算电流理论上为零,CT极性错误时会呈现较大的幅值。该方法有效解决了传统极性校验方法在负荷不足时无法校验的问题。仿真和录波验证了该方法的有效性,并已纳入工程应用方案。     

基于I-DPWM的三电平中点钳位光伏逆变器漏电流抑制方法

对于三电平中点钳位光伏逆变器,基于断续脉宽调制(discontinuous pulse width modulation, DPWM)并通过选择特定矢量进行钳位控制的方法,存在矢量分解计算时间长、注入共模电压分量和漏电流过大等不足。对此,提出了一种基于I-DPWM的三电平中点钳位光伏逆变器漏电流抑制方法。通过计算各类DPWM等效调制波来解析注入的低频共模电压分量。针对低频共模电压分量最小的DPWM1,在低频共模电压不连续点注入新的零序分量,通过减小低频共模电压来抑制漏电流幅值。同时,采用载波实现DPWM,免去了复杂的矢量运算。最后,在Matlab/Simulink平台建立了20 kW三电平中点钳位光伏逆变器的仿真模型,同时结合所设计的125 W实验样机验证了所提方法的有效性。     

基于空间矢量复合判断指标的变电站动力电缆漏电检测算法

为提高变电站长段动力电缆漏电监测水平,提出了一种基于空间矢量复合判据的变电站长段动力电缆漏电检测算法。首先对现有方法中无法检测三相漏电故障的问题进行了分析。然后,引入空间矢量的概念,将剩余电流数据转换为空间矢量圆,提出了剩余电流差流、A相漏电流以及空间矢量圆半径变化率3个漏电状态判断指标。并建立了针对电缆不平衡漏电及三相漏电故障的类型判断机制,实现了对长段动力电缆漏电状态及类型的准确检测。最后,通过仿真及江苏电网某500 kV变电站实际数据对所提方法的有效性与优越性进行验证。结果表明,该方法能够准确实现对不平衡漏电故障、故障演变过程以及三相漏电故障的判断,丰富了电缆漏电故障的诊断信息,有效提高了对变电站漏电问题的分析处理效率。     

Probing into Reverse Bias Dark Current in Perovskite Photodiodes: Critical Role of Surface Defects

Minimizing reverse bias dark current density (J_dark) while retaining high external quantum efficiency is crucial for promising applications of perovskite photodiodes, and it remains challenging to elucidate the ultimate origin of J_dark. It is demonstrated in this study that the surface defects induced by iodine vacancies are the main cause of J_dark in perovskite photodiodes. In a targeted way, the surface defects are thoroughly passivated through a simple treatment with butylamine hydroiodide to form ultrathin 2D perovskite on its 3D bulk. In the passivated perovskite photodiodes, J_dark as low as 3.78 × 10^-10 A cm^-2 at -0.1 V is achieved, and the photoresponse is also enhanced, especially at low light intensities. A combination of the two improvements realizes high specific detectivity up to 1.46 × 10¹² Jones in the devices. It is clarified that the trap states induced by the surface defects can not only raise the generation-recombination current density associated with the Shockley–Read–Hall mechanisms in the dark (increasing J_dark), but also provide additional carrier recombination paths under light illumination (decreasing photocurrent). The critical role of surface defects on J_dark of perovskite photodiodes suggests that making trap-free perovskite thin films, for example, by fine preparation and/or surface engineering, is a top priority for high-performance perovskite photodiodes.     

Surface Growth of Boron Nitride Nanotubes through Boron Source Design

Boron nitride nanotubes (BNNTs) are promising materials due to their unique physical and chemical properties. Fabrication technologies based on gas-phase reactions reduce the control and collection efficiency of BNNTs due to reactant and product dispersion within the reaction vessel. A surface growth method that allows for controllable growth of BNNTs in certain regions using a preburied boron source is introduced. This work leverages the high solubility of boron in metals to create a boronized layer on the surface which serves as the boron source to confine the growth of BNNTs. Dense and uniform BNNTs are obtained after loading catalysts onto the boronized substrate and annealing under ammonia. Confirmatory experiments demonstrate that the boride layer provides boron for BNNTs growth. Furthermore, the patterned growth of BNNTs is realized by patterning the boronizing region, demonstrating the controllability of this method. In addition, the Ni substrate with BNNTs growth exhibits better performance in corrosion resistance and thermal conductivity than pure Ni. This study introduces an alternative strategy for the surface growth of BNNTs based on boron source design, which offers new possibilities for the controllable preparation of BNNTs for various applications.     

面向同步辐射光源图像的可并行智能压缩方法

在建的高能同步辐射光源预计会产生海量原始数据,其中硬X射线实验线站产生的图像数据占比最高且具有高分辨率和高帧率的特点,亟需有效的无损压缩方法缓解存储和传输压力,然而现有通用无损压缩方法对该类图像压缩效果不佳,基于深度学习的无损压缩方法又耗时较长。结合同步辐射光源图像的特点,提出一种在保证图像压缩比前提下的可并行智能无损图像压缩方法。通过参数自适应的可逆分区量化方法,大幅缩小图像经过时间差分后的像素值分布范围,能够节省20%以上的存储空间。将以CNN为基础架构的时空学习网络C-Zip作为概率预测器,同时以数据集为单位过拟合训练模型进一步优化图像压缩比。针对压缩过程中耗时较长的算术编码过程,利用概率距离量化代替算术编码,结合深度学习进行无损编码,增加编码过程的并行度。实验结果表明,该方法的图像压缩比相比于PNG、FLIF等传统图像无损压缩方法提升了0.23~0.58,对于同步辐射光源图像具有更好的压缩效果。     

CuI Encapsulated within Single-Walled Carbon Nanotube Networks with High Current Carrying Capacity and Excellent Conductivity

High current carrying capacity and high conductivity are two important indicators for materials used in microscale electronics and inverters. However, it is challenging to obtain high conductivity and high current carrying capacity at the same time since high conductivity requires a weakly bonded system to provide free electrons, while high current carrying capacity requires a strongly bonded system. In this paper, CuI@SWCNT networks by filling the single-walled carbon nanotubes (SWCNTs) with CuI is ingeniously prepared. CuI@SWCNT shows good stability due to the confinement protection of SWCNTs. Through the host-guest hybridization, CuI@SWCNT networks exhibit a current carrying capacity of 2.04 × 10⁷ A cm⁻² and a conductivity of 31.67 kS m⁻¹. Their current carrying capacity and conductivity are significantly improved compared with SWCNT. The Kelvin probe force microscopy measurements show a drop of surface potential energy after SWCNT filled with CuI, indicating that the CuI guest molecules regulate the position of the Fermi level of SWCNTs, increasing carrier concentration, achieving high conductivity and high current carrying capacity. This study offers ideas and solutions for the regulation of high-performance carbon tube networks, which hold great promise for future applications in carbon-based electronic devices.     

多机制优化的模拟试验台数据流实时迁移研究

航空发动机高空模拟试验作为检验航空发动机性能的重要手段,其试验流程中采集的各传感器测点数据极为重要与珍贵。为了使数据信息的展示更为直观并且更深入挖掘数据潜在的价值,提出基于多框架集成的航空发动机高空模拟试验台数据流实时迁移及可视化技术。首先,利用MyBatis-Plus自动视图层构建可视化技术将存储于底层历史数据库中的信息直观地展示于Vue框架的浏览器端表结构空间中,方便试验员查看分析;然后利用基于GateWay限流机制的JDBC接口融合全量/增量和基于负载均衡机制的MyBatis框架融合多线程并行传输流的数据流迁移技术,将历史数据库中可供后续算法分析利用的重要数据信息同步至本地数据库中;最后,利用Vue框架的数据流前端监控界面,验证数据可视化展示的直观性、完整性、有效性和数据流同步的实时性。