94 research outputs found
Computing an Optimal Control Policy for an Energy Storage
We introduce StoDynProg, a small library created to solve Optimal Control
problems arising in the management of Renewable Power Sources, in particular
when coupled with an Energy Storage System. The library implements generic
Stochastic Dynamic Programming (SDP) numerical methods which can solve a large
class of Dynamic Optimization problems. We demonstrate the library capabilities
with a prototype problem: smoothing the power of an Ocean Wave Energy
Converter. First we use time series analysis to derive a stochastic Markovian
model of this system since it is required by Dynamic Programming. Then, we
briefly describe the "policy iteration" algorithm we have implemented and the
numerical tools being used. We show how the API design of the library is
generic enough to address Dynamic Optimization problems outside the field of
Energy Management. Finally, we solve the power smoothing problem and compare
the optimal control with a simpler heuristic control.Comment: Part of the Proceedings of the 6th European Conference on Python in
Science (EuroSciPy 2013), Pierre de Buyl and Nelle Varoquaux editors, (2014
Contributions à la co-optimisation contrôle-dimensionnement sur cycle de vie sous contrainte réseau des houlogénérateurs directs
The work of this PhD thesis deals with the minimization of the per-kWh cost of direct-drive wave energy converter, crucial to the economic feasibility of this technology. Despite the simplicity of such a chain (that should provide a better reliability compared to indirect chain), the conversion principle uses an oscillating system (a heaving buoy for example) that induces significant power fluctuations on the production. Without precautions, such fluctuations can lead to: a low global efficiency, an accelerated aging of the fragile electrical components and a failure to respect power quality constraints. To solve these issues, we firstly study the optimization of the direct drive wave energy converter control in order to increase the global energy efficiency (from wave to grid), considering conversion losses and the limit s from the sizing of an electrical chain (maximum force and power). The results point out the effect of the prediction horizon or the mechanical energy into the objective function. Production profiles allow the study of the flicker constraint (due to grid voltage fluctuations) linked notably to the grid characteristics at the connection point. Other models have also been developed to quantify the aging of the most fragile and highly stressed components, namely the energy storage system used for power smoothing (with super capacitors or electrochemical batteries Li-ion) and power semiconductors.Finally, these aging models are used to optimize key design parameters using life-cycle analysis. Moreover, the sizing of the storage system is co-optimized with the smoothing management.Les Energies Marines Renouvelables (EMR) se développent aujourd’hui très vite tant au niveau de la recherche amont que de la R&D, et même des premiers démonstrateurs à la mer. Parmi ces EMR, l'énergie des vagues présente un potentiel particulièrement intéressant. Avec une ressource annuelle brute moyenne estimée à 40 kW/m au large de la côte atlantique, le littoral français est plutôt bien exposé. Mais l’exploitation à grande échelle de cette énergie renouvelable ne sera réalisable et pertinente qu'à condition d'une bonne intégration au réseau électrique (qualité) ainsi que d'une gestion et d'un dimensionnement optimisé au sens du coût sur cycle de vie. Une première solution de génération tout électrique pour un houlogénérateur a d’abord été évaluée dans le cadre de la thèse de Marie RUELLAN menée sur le site de Bretagne du laboratoire SATIE (ENS de Cachan). Ces travaux ont mis en évidence le potentiel de viabilité économique de cette chaîne de conversion et ont permis de poser la question du dimensionnement de l’ensemble convertisseur-machine et de soulever les problèmes associés à la qualité de l’énergie produite. Puis une seconde thèse a été menée par Judicaël AUBRY dans la même équipe de recherche. Elle a consisté, entre autres, en l’étude d’une première solution de traitement des fluctuations de la puissance basée sur un système de stockage par supercondensateurs. Une méthodologie de dimensionnement de l’ensemble convertisseur-machine et de gestion de l’énergie stockée fut également élaborée, mais en découplant le dimensionnement et la gestion de la production d’énergie et de ceux de son système de stockage. Le doctorant devra donc : 1. S’approprier les travaux antérieurs réalisés dans le domaine de la récupération de l’énergie des vagues ainsi que les modèles hydrodynamiques et mécaniques réalisés par notre partenaire : le LHEEA de l’Ecole Centrale de Nantes - 2. Résoudre le problème du couplage entre dimensionnement/gestion de la chaîne de conversion et dimensionnement/gestion du système de stockage. 3. Participer à la réalisation d’un banc test à échelle réduite de la chaine électrique et valider expérimentalement les modèles énergétiques du stockage et des convertisseurs statiques associés - 4. Proposer une méthodologie de dimensionnement de la chaine électrique intégrant le stockage et les lois de contrôle préalablement élaborées 5. Déterminer les gains en termes de capacités de stockage obtenus grâce à la mutualisation de la production (parc de machines) et évaluer l’intérêt d’un stockage centralisé - 6. Analyser l’impact sur le réseau d’une production houlogénérée selon divers scenarii, modèles et outils développés par tous les partenaires dans le cadre du projet QUALIPHE. L’exemple traité sera celui de l’Ile d’Yeu (en collaboration avec le SyDEV
Assessment of the Impact of Frequency Containment Control and Synthetic Inertia on Intermittent Energies Generators Integration
International audienceThe increasing power generation out of intermittent renewable energy sources will result in a reduction of the grid stability if no compensatory actions are taken. This issue may lead to future obligations for energy providers. This paper studies the implication of the future obligations for generators in Europe according to the recommendations of ENTSO-E, in particular the obligation for some generators to have a synthetic (or virtual) inertia and a frequency sensitive control. These obligations will be described in details in the paper, in particular their effect on the grid management and stability. The impact of this new actions on the energy production will be discussed. The continental European grid frequency is used as an example
First demonstration of a Compton gamma imager based on silicon photomultipliers
We are developing a rugged and person-transportable Compton gamma imager for
use in security investigations of radioactive materials, and for radiological
incident remediation. The imager is composed of layers of scintillator with
light collection for the forward layers provided by silicon photomultipliers
and for the rear layer by photomultiplier tubes. As a first step, we have
developed a 1/5th-scale demonstration unit of the final imager. We present the
imaging performance of this demonstration unit for Cs-137 at angles of up to 30
degrees off-axis. Results are also presented for Sn-113 and Na-22. This
represents the first demonstration of the use of silicon photomultipliers as an
embedded component for light collection in a Compton gamma imager.Comment: 19 pages, 6 figure
Towards the optimal use of an existing MRE electrical network from an electrothermal perspective
International audienc
Modélisation, Commande et Mise en Oeuvre de deux Ponts Triphasés Back-to-Back avec Contrôle des Flux de Puissance et de la Tension du Bus DC : Application à l'émulation de la chaîne de conversion électrique des houlogénérateurs directs
National audienceCet article présente la modélisation, la simulation et la mise en œuvre expérimentale d’un onduleur triphasé back-to-back avec prise en charge de la gestion des flux de puissances (active et réactive) et de la régulation de la tension du bus DC. La stratégie de commande utilisée offre la possibilité de contrôler indépendamment les puissances active et réactive. Les deux boucles de régulation (courant et tension) sont complètement découplées et indépendantes. L’objectif de ce dispositif est d’émuler le fonctionnement de la chaîne de conversion électrique de houlogénérateurs directs (tels que le SEAREV), avec un pont triphasé contrôlant la génératrice et la récupération d’énergie et l’autre pont injectant l’énergie au réseau. La production résultante est fortement pulsante et à très basse fréquence (moins d’un Hertz). Les résultats de simulation sous Maltab/Simulink ainsi que les résultats expérimentaux obtenus en utilisant des modules d’onduleurs pédagogiques pilotés par des cartes DSP sont présentés
Separated Kaon Electroproduction Cross Section and the Kaon Form Factor from 6 GeV JLab Data
The () reaction was studied as a function of
the Mandelstam variable using data from the E01-004 (FPI-2) and E93-018
experiments that were carried out in Hall C at the 6 GeV Jefferson Lab. The
cross section was fully separated into longitudinal and transverse components,
and two interference terms at four-momentum transfers of 1.00, 1.36 and
2.07 GeV. The kaon form factor was extracted from the longitudinal cross
section using the Regge model by Vanderhaeghen, Guidal, and Laget. The results
establish the method, previously used successfully for pion analyses, for
extracting the kaon form factor. Data from 12 GeV Jefferson Lab experiments are
expected to have sufficient precision to distinguish between theoretical
predictions, for example recent perturbative QCD calculations with modern
parton distribution amplitudes. The leading-twist behavior for light mesons is
predicted to set in for values of between 5-10 GeV, which makes data
in the few GeV regime particularly interesting. The dependence at fixed
and of the longitudinal cross section we extracted seems consistent
with the QCD factorization prediction within the experimental uncertainty
Charged pion form factor between Q^2=0.60 and 2.45 GeV^2. II. Determination of, and results for, the pion form factor
The charged pion form factor, Fpi(Q^2), is an important quantity which can be
used to advance our knowledge of hadronic structure. However, the extraction of
Fpi from data requires a model of the 1H(e,e'pi+)n reaction, and thus is
inherently model dependent. Therefore, a detailed description of the extraction
of the charged pion form factor from electroproduction data obtained recently
at Jefferson Lab is presented, with particular focus given to the dominant
uncertainties in this procedure. Results for Fpi are presented for
Q^2=0.60-2.45 GeV^2. Above Q^2=1.5 GeV^2, the Fpi values are systematically
below the monopole parameterization that describes the low Q^2 data used to
determine the pion charge radius. The pion form factor can be calculated in a
wide variety of theoretical approaches, and the experimental results are
compared to a number of calculations. This comparison is helpful in
understanding the role of soft versus hard contributions to hadronic structure
in the intermediate Q^2 regime.Comment: 18 pages, 11 figure
Charged pion form factor between =0.60 and 2.45 GeV. I. Measurements of the cross section for the H() reaction
Cross sections for the reaction H() were measured in Hall
C at Thomas Jefferson National Accelerator Facility (JLab) using the CEBAF
high-intensity, continous electron beam in order to determine the charged pion
form factor. Data were taken for central four-momentum transfers ranging from
=0.60 to 2.45 GeV at an invariant mass of the virtual photon-nucleon
system of =1.95 and 2.22 GeV. The measured cross sections were separated
into the four structure functions , , , and
. The various parts of the experimental setup and the analysis
steps are described in detail, including the calibrations and systematic
studies, which were needed to obtain high precision results. The different
types of systematic uncertainties are also discussed. The results for the
separated cross sections as a function of the Mandelstam variable at the
different values of are presented. Some global features of the data are
discussed, and the data are compared with the results of some model
calculations for the reaction H().Comment: 26 pages, 23 figure
Separated Response Function Ratios in Exclusive, Forward pi^{+/-} Electroproduction
The study of exclusive electroproduction on the nucleon,
including separation of the various structure functions, is of interest for a
number of reasons. The ratio is
sensitive to isoscalar contamination to the dominant isovector pion exchange
amplitude, which is the basis for the determination of the charged pion form
factor from electroproduction data. A change in the value of
from unity at small , to 1/4 at
large , would suggest a transition from coupling to a (virtual) pion to
coupling to individual quarks. Furthermore, the mentioned ratios may show an
earlier approach to pQCD than the individual cross sections. We have performed
the first complete separation of the four unpolarized electromagnetic structure
functions above the dominant resonances in forward, exclusive
electroproduction on the deuteron at central values of 0.6, 1.0, 1.6
GeV at =1.95 GeV, and GeV at =2.22 GeV. Here, we
present the and cross sections, with emphasis on and , and
compare them with theoretical calculations. Results for the separated ratio
indicate dominance of the pion-pole diagram at low , while results
for are consistent with a transition between pion knockout and quark
knockout mechanisms.Comment: 6 pages, 3 figure
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