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排序方式: 共有315条查询结果,搜索用时 13 毫秒
1.
This paper presents a fast distance relay for series compensated transmission lines based on the R–L differential-equation algorithm using the theory of equal transfer process of transmission lines. The measuring distances based on the proposed algorithm can fast approach the actual value of fault distance when a fault occurs in front of the series capacitor. When a fault occurs behind of the series capacitor, the fault loop, including the series capacitor, does not match the R–L transmission line model, so the measuring distances fluctuate severely. Based on this, the relative position of the fault with respect to the series capacitor can be judged effectively according to the fluctuation range of the measuring distances, and the accurate fault location can be obtained fast. A variety of PSCAD/EMTDC simulation tests show that the new relay has fast operating speed and high accuracy when applied to the long series compensated transmission lines. 相似文献
2.
《Journal of power sources》2006,160(1):657-661
The cathode-active materials, layered Li[Ni0.333Co0.333Mn0.293Al0.04]O2−zFz (0 ≤ z ≤ 0.1), were synthesized from a sol–gel precursor at 900 °C in air. The influence of Al–F co-substitution on the structural and electrochemical properties of the as-prepared samples was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical experiments. The results showed that Li[Ni0.333Co0.333Mn0.293Al0.04]O2−zFz has a typical hexagonal structure with a single phase, the particle sizes of the samples tended to increase with increasing fluorine content. It has been found that Li[Ni0.333Co0.333Mn0.293Al0.04]O1.95F0.05 showed an improved cathodic behavior and discharge capacity retention compared to the undoped samples in the voltage range of 3.0–4.3 V. The electrodes prepared from Li[Ni0.333Co0.333Mn0.293Al0.04]O1.95F0.05 delivered an initial discharge capacity of 158 mAh−1 g and an initial coulombic efficiency is 91.3%, and the capacity retention at the 20th cycle was 94.9%. Though the F-doped samples had lower initial capacities, they showed better cycle performances compared with F-free samples. Therefore, this is a promising material for a lithium-ion battery. 相似文献
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为满足太阳能无人机对长航时飞行和高载重能力的需求,研究能源系统的储能均衡控制问题.通过将太阳能无人机中每个由光伏-储能-输出单元组成的发电节点作为一个智能体,设计基于多智能体的分布式控制器并给出满足系统约束的控制算法,实现储能单元荷电状态的一致性.分别针对连续系统模型和离散系统模型给出分布式控制协议,并通过理论分析说明连续和离散的控制协议均可实现控制目标.通过搭建半实物平台进行实测验证,采用光伏模拟器和电子负载模拟能源系统运行的外部环境,以18650锂离子电池作为储能单元,实验结果表明,分布式协同控制协议能够有效地解决光伏功率不均及电池参数差异导致的不均衡问题,使系统的充放电深度得以有效提升. 相似文献
6.
The study of the thermal behavior of power modules has become a necessity regarding the known rapid development in modern power electronics, and the prediction of temperature variation has generally been performed using transient thermal equivalent circuits. In this paper we have developed a simplified analytical thermal model of a power hybrid module. This analytical method is used to evaluate the thermal parameters of a device. The model takes into account the thermal mutual influence between the different module chips based on the analytical method. The thermal interaction between components is dependent on the boundary condition, the dissipated power value in the different components and the number of operating chips constituting the module. This effect is modelled as a source energy and a thermal resistance simply computed tanks to reasonably low measurement applied on the module. The derived thermal models offer an excellent trade-off between accuracy, efficiency and CPU-cost. 相似文献
7.
《Carbon》2014
Reduced GO in confined space of silica gel nanopores doped with sulfur shows high catalytic activity for oxygen reduction reaction (ORR) in alkaline medium and exhibits a superior tolerance to the presence of methanol. Even though the partially reduced GO with hydroquinone structures is a good catalysts for ORR, it shows instability in KOH. The good performance of S-doped material is linked to the coexistence of sulfur and oxygen on the surface in equal atomic quantities and a unique porosity being the replica of the silica pores. The former leads to the positive charge on the carbon atoms, which are the reaction sites. Hydrophobicity of the surface and small pores enhance adsorption of O2. 相似文献
8.
《International Journal of Hydrogen Energy》2022,47(6):4062-4074
In this work, coupling effects of water content, temperature, oxygen density, and polytetrafluoroethylene (PTFE) loading on oxygen transport through an ionomer thin film on a platinum surface in a catalyst layer of a proton exchange membrane (PEM) fuel cell are investigated using molecular dynamics approach. Taguchi orthogonal algorithm is employed to comprehensively analyze the coupling effects in a limited number of cases. It is found that the effect of operation temperature is the weakest among the four factors, which has the smallest effect index 14.4. Coupling effects including the PTFE loadings on the oxygen transfer through the ionomer thin film is uncovered. Less PTFE loadings should be beneficial for the oxygen transfer. The chemical potential gradient is considered as the major driven force for the oxygen transport through the ionomer thin film, and oxygen density is the dominating factor, significantly affecting the chemical potential in the thin film. 相似文献
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《Ceramics International》2016,42(13):14587-14594
A facile chemical deposition method has been adopted to prepare cerium fluoride (CeF3) surface modified LiNi1/3Co1/3Mn1/3O2 as cathode material for lithium-ion batteries. Structure analyses reveal that the surface of LiNi1/3Co1/3Mn1/3O2 particles is uniformly coated by CeF3. Electrochemical tests indicate that the optimal CeF3 content is 1 wt%. The 1 wt% CeF3-coated LiNi1/3Co1/3Mn1/3O2 can deliver a discharge capacity of 107.1 mA h g−1 even at 5 C rate, while the pristine does only 57.3 mA h g−1. Compared to the pristine, the 1 wt% CeF3-coated LiNi1/3Co1/3Mn1/3O2 exhibits the greatly enhanced capacity and cycling stability in the voltage range of 3.0–4.5 V, which suggests that the CeF3 coating has the positive effect on the high-voltage application of LiNi1/3Co1/3Mn1/3O2. According to the analyses from electrochemical impedance spectra, enhanced electrochemical performance is mainly because the stable CeF3 coating layer can prevent the HF-containing electrolyte from continuously attacking the LiNi1/3Co1/3Mn1/3O2 cathode and retard the passivating layer growth on the cathode. 相似文献