Control of Dispersed Generation to Regulate Distribution and Support Transmission Voltages

in Proc. IEEE PES 2013 PowerTech Conference (in press)

This paper presents an on-line centralized controller based on Model Predictive Control concepts to regulate distribution network voltages, and possibly support transmission network. It computes and ... [more ▼]

This paper presents an on-line centralized controller based on Model Predictive Control concepts to regulate distribution network voltages, and possibly support transmission network. It computes and applies a sequence of changes of the distributed generators power outputs to progressively meet a set of operation constraints at distribution, and possibly transmission level. An 11-kV, 75-bus test system with 22 distributed generators is used to illustrate the performance of the proposed controller when transmission system support is requested. Comparisons with single-step open-loop control are also provided. [less ▲]

Dynamic Simulations of Combined Transmission and Distribution Systems using Decomposition and Localization

in Proc. IEEE PES 2013 PowerTech Conference (in press)

Simulating a power system with both transmission and distribution networks modeled is a challenging task. On the one hand, it is difficult to set up equivalents restituting the dynamic behavior of ... [more ▼]

Simulating a power system with both transmission and distribution networks modeled is a challenging task. On the one hand, it is difficult to set up equivalents restituting the dynamic behavior of aggregated loads and distributed generation units. On the other hand, representing all distribution networks in detail is computationally very demanding. In this paper, the combination of a domain-decomposition approach with the exploitation of the localized nature of power system responses to disturbances is proposed. Distribution networks marginally participating to the system dynamics are automatically replaced by simple models, while the others are simulated with full detail, thereby preserving simulation accuracy. [less ▲]

Semantic Annotation of GPS Traces: Activity Type Inference

in Transportation Research Record: Journal of the Transportation Research Board (in press)

Due to the rapid development of technology, larger data sets concerning activity travel behavior become available. These data sets often lack semantic interpretation. This implies that annotation in terms ... [more ▼]

Due to the rapid development of technology, larger data sets concerning activity travel behavior become available. These data sets often lack semantic interpretation. This implies that annotation in terms of activity type and transportation mode is necessary. This paper aims to infer activity types from GPS traces by developing a decision tree-based model. The model only considers activity start times and activity durations. Based on the decision tree classification, a probability distribution and a point prediction model were constructed. The probability matrix describes the probability of each activity type for each class (i.e. combination of activity start time and activity duration). In each class, the point prediction model selects the activity type that has the highest probability. Two types of data were collected in 2006 and 2007 in Flanders, Belgium, i.e. activity travel data and GPS data. The optimal classification tree constructed comprises 18 leaves. Consequently, 18 if-then rules were derived. An accuracy of 74% was achieved when training the tree. The accuracy of the model for the validation set, i.e. 72.5%, shows that overfitting is minimal. When applying the model to the test set, the accuracy was almost 76%. The models indicate the importance of time information in the semantic enrichment process. This study contributes to future data collection in that it enables researchers to directly infer activity types from activity start time and duration information obtained from GPS data. Because no location information is needed, this research can be easily and readily implemented to millions of individual agents. [less ▲]

Accelerated and Localized Newton Schemes for Faster Dynamic Simulation of Large Power Systems

in IEEE Transactions on Power Systems (in press)

This paper proposes two methods to speed up the demanding time-domain simulations of large power system models. First, the sparse linear system to solve at each Newton iteration is decomposed according to ... [more ▼]

This paper proposes two methods to speed up the demanding time-domain simulations of large power system models. First, the sparse linear system to solve at each Newton iteration is decomposed according to its bordered block diagonal structure, in order to solve only those parts that need to be solved, and update only sub-matrices of the Jacobian that need to be updated. This brings computational savings without degradation of accuracy. Next, the Jacobian structure is further exploited to localize the system response, i.e. involve only the components identified as active, with an acceptable and controllable decrease in accuracy. The accuracy and computational savings are assessed on a large-scale test system. [less ▲]

Mobiles oui, migrants non ? Jeunes marocains qui bougent

in Exploration De La Mobilité Autour De La Méditerranée (in press)

Les récits ethnographiques et les réflexions que je vais présenter dans cet article sont issus d’une recherche menée dans les villes marocaines de Khouribga et de Rabat entre 2007 et 2008. L’étude ... [more ▼]

Les récits ethnographiques et les réflexions que je vais présenter dans cet article sont issus d’une recherche menée dans les villes marocaines de Khouribga et de Rabat entre 2007 et 2008. L’étude concerne la mobilité d’un groupe de jeunes « khouribgii » inscrits dans des projets migratoires vers l’Italie ainsi que les actions et les discours de certains organismes humanitaires (internationaux et locaux) s’occupant de thématiques liées à la migration. L’utilisation d’une distinction terminologique adoptée ici entre mobilité d’une part et migration d’autre part, a été choisi pour représenter une différenciation opérée entre l’expérience faite de la mobilité par ces jeunes à travers leur préparation à la migration, et le blâme et l’entrave à l’action de migrer opérée dans les discours et par les actions des ONG. D’un côté nous avons donc une mobilité qui s’exerce dans l’imaginaire de ces jeunes, tout comme dans des pratiques concrètes mises en place pour réaliser le projet migratoire (qui comportent l’apprentissage d’instruments utiles à l’affronter, tels que la langue italienne ou la capacité de mouvement à travers l’appareil législatif international et national qui régisse la migration) ; une mobilité qui s’exerce également dans la participation aux réseaux migratoires familiaux ; et de l’autre côté, une migration dissuadée par les programmes humanitaires ou sociaux. Ces derniers consentent une mobilité qui puisse s’accomplir dans un rapprochement « virtuel » au pays de destination, à travers notamment des cours de « culture italienne », mais en détournant la définition des parcours migratoires personnels et en les insérant dans la rhétorique de la « migration intelligente », c’est-à-dire en demandant que, s’ils arrivent à être réalisés, ils soient utiles au « développement » de la communauté locale d’origine. A travers l’analyse de ces aspects, cet article vise donc à démontrer la réalité des déplacements des jeunes interviewés, malgré leur permanence sur le territoire marocain, la concrétisation de leur aspiration de migration dans l’expérience de la mobilité, en remettant donc en cause la frontière entre les deux concepts définis ci-dessus. [less ▲]

Review of physicochemical processes involved in agrochemical spray retention

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (in press)

This review provides a broad view of the processes and parameters involved in applying agrochemicals to the leaves of field crops. Treatment efficiency is assessed using macroscopic and microscopic ... [more ▼]

This review provides a broad view of the processes and parameters involved in applying agrochemicals to the leaves of field crops. Treatment efficiency is assessed using macroscopic and microscopic approaches to investigate spray retention. With the macroscopic approach, aspects related to spray coarseness, carrier volume, leaf wettability, plant architecture, crop density and additives are addressed. Comparative studies have highlighted the wide variability in spray retention as a function of these parameters. They have failed, however, to describe the underlying physical relationships clearly enough to generalize the results. These relationships are better investigated using a microscopic approach, where drop impact behavior is established in relation to target surface and fluid properties. The wetting regime (either Wenzel or Cassie-Baxter) depends on the leaf surface microscopic roughness ratio (r) and chemical nature, fluid dynamic surface tension and drop impact energy. Adhesion, rebound and disintegration have been observed successively with increasing drop impact energy. Transitions between impact outcomes are influenced by fluid rheology and the dynamic surface tension of the fluid. The effect of surface orientation remains poorly explored, but it seems to have a limited influence on retention. Recent fundamental studies on superhydrophobicity and wetting should help practitioners in their search for an ever more rational application of agrochemicals. They could also drive the development of new systematic retention testing methods. [less ▲]

Un dernier Poe

in Alcools. Actes du XVIe colloque des Invalides (2013, November)

Simulation of a cold climate heat pump furnished with a scroll compressor with multiple injection lines

in Proceedings of the International Conference on Compressors and their Systems 2013 (2013, September)

A detailed scroll compressor simulation has been developed as described in a companion paper. In this work, the compressor simulation code is used to investigate vapor injection in scroll compressors for ... [more ▼]

A detailed scroll compressor simulation has been developed as described in a companion paper. In this work, the compressor simulation code is used to investigate vapor injection in scroll compressors for cold climate heat pumps. The required analysis is developed for vapor injection in scroll compressors with one or two injection lines. The improvement in heat pump efficiency at a -20 C evaporation temperature with one injection line is as much as 10% while with two injection lines the increase in efficiency can be as much as 16% [less ▲]

The global grid

in Renewable Energy : An International Journal (2013), 57

This paper puts forward the vision that a natural future stage of the electricity network could be a grid spanning the whole planet and connecting most of the large power plants in the world: this is the ... [more ▼]

This paper puts forward the vision that a natural future stage of the electricity network could be a grid spanning the whole planet and connecting most of the large power plants in the world: this is the “Global Grid”. The main driving force behind the Global Grid will be the harvesting of remote renewable sources, and its key infrastructure element will be the high capacity long transmission lines. Wind farms and solar power plants will supply load centers with green power over long distances. This paper focuses on the introduction of the concept, showing that a globally interconnected network can be technologically feasible and economically competitive. We further highlight the multiple opportunities emerging from a global electricity network such as smoothing the renewable energy supply and electricity demand, reducing the need for bulk storage, and reducing the volatility of the energy prices. We also discuss possible investment mechanisms and operating schemes. Among others, we envision in such a system a global power market and the establishment of two new coordinating bodies, the “Global Regulator” and the “Global System Operator”. [less ▲]

An Energy-Based Variational Model of Ferromagnetic Hysteresis for Finite Element Computations

in Journal of Computational & Applied Mathematics (2013), 246

This paper proposes a macroscopic model for ferromagnetic hysteresis that is well-suited for finite element implementation. The model is readily vectorial and relies on a consistent thermodynamic ... [more ▼]

This paper proposes a macroscopic model for ferromagnetic hysteresis that is well-suited for finite element implementation. The model is readily vectorial and relies on a consistent thermodynamic formulation. In particular, the stored magnetic energy and the dissipated energy are known at all times, and not solely after the completion of closed hysteresis loops as is usually the case. The obtained incremental formulation is variationally consistent, i.e., all internal variables follow from the minimization of a thermodynamic potential. [less ▲]