550 research outputs found
Surface-wave solitons on the interface between a linear medium and a nonlocal nonlinear medium
We address the properties of surface-wave solitons on the interface between a
semi-infinite homogeneous linear medium and a semi-infinite homogeneous
nonlinear nonlocal medium. The stability, energy flow and FWHM of the surface
wave solitons can be affected by the degree of nonlocality of the nonlinear
medium. We find that the refractive index difference affects the power
distribution of the surface solitons in two media. We show that the different
boundary values at the interface can lead to the different peak position of the
surface solitons, but it can not influence the solitons stability with a
certain degree of nonlocality.Comment: 8 pages, 14 figures, 15 references, and so o
Optimization of Battery Energy Storage to Improve Power System Oscillation Damping
A placement problem for multiple Battery Energy Storage System (BESS) units
is formulated towards power system transient voltage stability enhancement in
this paper. The problem is solved by the Cross-Entropy (CE) optimization
method. A simulation-based approach is adopted to incorporate higher-order
dynamics and nonlinearities of generators and loads. The objective is to
maximize the voltage stability index, which is setup based on certain
grid-codes. Formulations of the optimization problem are then discussed.
Finally, the proposed approach is implemented in MATLAB/DIgSILENT and tested on
the New England 39-Bus system. Results indicate that installing BESS units at
the optimized location can alleviate transient voltage instability issue
compared with the original system with no BESS. The CE placement algorithm is
also compared with the classic PSO (Particle Swarm Optimization) method, and
its superiority is demonstrated in terms of a faster convergence rate with
matched solution qualities.Comment: This paper has been accepted by IEEE Transactions on Sustainable
Energy and now still in online-publication phase, IEEE Transactions on
Sustainable Energy. 201
The convergence of subspace trust region methods
AbstractThe trust region method is an effective approach for solving optimization problems due to its robustness and strong convergence. However, the subproblem in the trust region method is difficult or time-consuming to solve in practical computation, especially in large-scale problems. In this paper we consider a new class of trust region methods, specifically subspace trust region methods. The subproblem in these methods has an adequate initial trust region radius and can be solved in a simple subspace. It is easier to solve than the original subproblem because the dimension of the subproblem in the subspace is reduced substantially. We investigate the global convergence and convergence rate of these methods
Trends in Research on Electrochemical Oxidation
This paper presented a detailed chronological survey of scientific output related to electrochemical oxidation in SCI categories of “environmental sciences, environmental engineering and water re-sources” from 1975 to 2012. Publications were analyzed by distribution of the number of publications and times cited, source categories, source journals, author keywords, KeyWords Plus, and the most cited publications in these years. It was concluded that Pt, boron-doped diamond, TiO2 were currently and would continue to be the predominant focused electrode materials at least over the next decade. And the foci of studied pollutants in the electrochemical oxidation were mainly concentrated in dyes and phenols popularly existing in the practical wastewaters. What’s more, electrochemical degradation, wastewater treatment, electrochemical determination and fuel cell would be the key research topics currently and recently. Fenton, photocatalysis and coagulation were the most-frequent combination technology with electrochemical oxidation based on the bibliometric results. Contribution of Croatian chemists to the field is mentioned
Submodular Load Clustering with Robust Principal Component Analysis
Traditional load analysis is facing challenges with the new electricity usage
patterns due to demand response as well as increasing deployment of distributed
generations, including photovoltaics (PV), electric vehicles (EV), and energy
storage systems (ESS). At the transmission system, despite of irregular load
behaviors at different areas, highly aggregated load shapes still share similar
characteristics. Load clustering is to discover such intrinsic patterns and
provide useful information to other load applications, such as load forecasting
and load modeling. This paper proposes an efficient submodular load clustering
method for transmission-level load areas. Robust principal component analysis
(R-PCA) firstly decomposes the annual load profiles into low-rank components
and sparse components to extract key features. A novel submodular cluster
center selection technique is then applied to determine the optimal cluster
centers through constructed similarity graph. Following the selection results,
load areas are efficiently assigned to different clusters for further load
analysis and applications. Numerical results obtained from PJM load demonstrate
the effectiveness of the proposed approach.Comment: Accepted by 2019 IEEE PES General Meeting, Atlanta, G
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