A Guide to Solar Power Forecasting using ARMA Models

We describe a simple and succinct methodology to develop hourly auto-regressive moving average (ARMA) models to forecast power output from a photovoltaic solar generator. We illustrate how to build an ARMA model, to use statistical tests to validate it, and construct hourly samples. The resulting model inherits nice properties for embedding it into more sophisticated operation and planning models, while at the same time showing relatively good accuracy. Additionally, it represents a good forecasting tool for sample generation for stochastic energy optimization models

Vibration-Based structural health monitoring using piezoelectric transducers and parametric t-SNE

In this paper, we evaluate the performance of the so-called parametric t-distributed stochastic neighbor embedding (P-t-SNE), comparing it to the performance of the t-SNE, the non-parametric version. The methodology used in this study is introduced for the detection and classification of structural changes in the field of structural health monitoring. This method is based on the combination of principal component analysis (PCA) and P-t-SNE, and it is applied to an experimental case study of an aluminum plate with four piezoelectric transducers. The basic steps of the detection and classification process are: (i) the raw data are scaled using mean-centered group scaling and then PCA is applied to reduce its dimensionality; (ii) P-t-SNE is applied to represent the scaled and reduced data as 2-dimensional points, defining a cluster for each structural state; and (iii) the current structure to be diagnosed is associated with a cluster employing two strategies: (a) majority voting; and (b) the sum of the inverse distances. The results in the frequency domain manifest the strong performance of P-t-SNE, which is comparable to the performance of t-SNE but outperforms t-SNE in terms of computational cost and runtime. When the method is based on P-t-SNE, the overall accuracy fluctuates between 99.5% and 99.75%.Peer ReviewedPostprint (published version

Linear Battery Models for Power Systems Analysis

Mathematical models are just models. The desire to describe battery energy storage system (BESS) operation using computationally tractable model formulations has motivated a long-standing discussion in both the scientific and industrial communities. Linear BESS models are the most widely used so far. However, finding suitable linear BESS models has been controversial. This paper focuses on the description of linear BESS models. Four linear BESS formulations are presented, among the most popularly used. A new formulation is also proposed. The 5 BESS models are tested in 100 random BESS and 1.450 random samples of daily profiles of renewable generation. Two classical problems of power systems, namely, the set-point tracking problem and the transmission expansion planning problem, are selected for numerical analysis. Five thousand simulations are used to draw a better interpretation of each linear formulation presented and showcase specific challenges of BESS models. Practical recommendations are provided based on the findings.Comment: Power Systems Computation Conference (PSCC) 202

Prediction of turbulent reactive flows by means of numerical simulations applied to anaerobic digesters

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Priority Lists for Power System Investments: Locating Phasor Measurement Units

Power systems incrementally and continuously upgrade their components, such as transmission lines, reactive capacitors, or generating units. Decision-making tools often support the selection of the best set of components to upgrade. Optimization models are often used to support decision making at a given point in time. After certain time intervals, re-optimization is performed to find new components to add. In this paper, we propose a decision-making framework for incrementally updating power system components. This is an alternative approach to the classical sequential re-optimization decision making for an investment problem with modeled budget constraints. Our approach provides a priority list as a solution with a list of new components to upgrade. We show that i) our framework is consistent with the evolution of power system upgrades, and ii) in particular circumstances, both frameworks provide the same solution if the problem satisfies submodularity property. We have selected the problem of phasor measurement unit localization and compared the solution with the classical sequential re-optimization framework. For this particular problem, we show that the two approaches provide close results, while only our proposed algorithm is applicable in practice. The cases of 14 and 118 IEEE buses are used to illustrate the proposed methodology

The many faces of VIP in neuroimmunology: a cytokine rather a neuropeptide?

10 pages, 3 figures.-- PMID: 15333575 [PubMed].Neuroimmunomodulation has experienced an explosive growth not only in basic research, but expanding to the point that prospective clinical research could be now a reality. A crucial factor for the functioning of this intimate bidirectional network was the demonstration that the immune and neuroendocrine systems speak a mutual biochemical language. This implies 1) production of neuroendocrine hormones and neuropeptides by immune cells and of cytokines by neuroendocrine cells; 2) evidence for shared receptors on cells of the immune and neuroendocrine systems; 3) effect of neuroendocrine mediators on immune functions; and 4) effect of cytokines on the neuroendocrine system. This reduces traditional differences between neurotransmitters, hormones, and immune mediators and raises the following question: what can we now regard as immune or neuroendocrine? Vasoactive intestinal peptide (VIP) is one example of this paradigm. VIP has traditionally been classified as a neuropeptide/neurotransmitter based in its capacity to mediate and regulate neuronal functions. Recent work has demonstrated that VIP is produced by T cells, especially Th2 cells, and that through specific receptors it exerts immunological functions typically ascribed to Th2 cytokines in nervous and immune systems. Here, we postulate that instead of a neuropeptide, VIP could be fully considered a type 2 cytokine with a key role in neuroimmunology.This study was supported by extramural grants from the Instituto de Salud Carlos III, Fondo de Investigacion Sanitaria, Spanish Ministry of Health (PI 030359 to D.P and PI 030526 to M.D.), from La Caixa Foundation (NE-03-009 to M.D) and from the European Union 6th Framework Grants Program (FP6-006380 to D.P).Peer reviewe