Coalition Formation Algorithm of Prosumers in a Smart Grid Environment

In a smart grid environment, we study coalition formation of prosumers that aim at entering the energy market. It is paramount for the grid operation that the energy producers are able to sustain the grid demand in terms of stability and minimum production requirement. We design an algorithm that seeks to form coalitions that will meet both of these requirements: a minimum energy level for the coalitions and a steady production level which leads to finding uncorrelated sources of energy to form a coalition. We propose an algorithm that uses graph tools such as correlation graphs or clique percolation to form coalitions that meet such complex constraints. We validate the algorithm against a random procedure and show that, it not only performs better in term of social welfare for the power grid, but also that it is more robust against unforeseen production variations due to changing weather conditions for instance.Comment: 6 pages, 4 figures, 1 table. submited to ICC 201

Nilearn for new use cases: Scaling up computational and community efforts

Introduction Nilearn (https://nilearn.github.io) is a well-established Python package that provides statistical and machine learning tools for fast and easy analysis of brain images with instructive documentation and a friendly community. This focus has led to its current position as a crucial part of the neuroimaging community’s open-source software ecosystem, supporting efficient and reproducible science [1]. It has been continuously developed over the past 10 years, currently with 900 stars, 500 forks, and 176 contributors on GitHub. Nilearn leverages and builds upon other central Python machine learning packages, such as Scikit-Learn [2], that are extensively used, tested, and optimized by a large scientific and industrial community. In recent years, efforts in Nilearn have been focused on meeting evolving community needs by increasing General Linear Model (GLM) support, interfacing with initiatives like fMRIPrep and BIDS, and improving the user documentation. Here we report on progress regarding our current priorities. Methods Nilearn is developed to be accessible and easy-to-use for researchers and the open-source community. It features user-focused documentation that includes a user guide and an example gallery as well as comprehensive contribution guidelines. Nilearn is also presented in tutorials and workshops throughout the year including the Montreal Artificial Intelligence and Neuroscience (MAIN) Educational Workshop, the OHBM Brainhack event, and for the Chinese Open Science Network. The community is encouraged to ask questions, report bugs, make suggestions for improvements or new features, and make direct contributions to the source code. We use the platforms Neurostars, GitHub, and Discord to interact with contributors and users on a daily basis. Nilearn adheres to best practices in software development including using version control, unit testing, and requiring multiple reviews of contributions. We also have a continuous integration infrastructure set up to automate many aspects of our development process and make sure our code is continuously tested and up-to-date. Results Nilearn supports methods such as image manipulation and processing, decoding, functional connectivity analysis, GLM, multivariate pattern analysis, along with plotting volumetric and surface data. In the latest release, cluster-level and TFCE-based family-wise error rate (FWER) control have been added to support the mass univariate and GLM analysis modules, expanding from the already implemented voxel-level correction method (see Fig1). Optimizing Nilearn’s maskers is also underway such as the recently added classes for handling multi-subject 4D image data. These also provide the option to use parallelization to speed up computation. In addition, Nilearn has introduced a new theme to update the documentation making the website more readable and accessible (https://nilearn.github.io/). This change also sets the stage for further improvement and modernisation of several aspects of the documentation, like the user guide. Development on Nilearn’s interfaces module added a new function to write BIDS-compatible model results to disk. This and further development of the BIDS interface will facilitate interaction with other relevant community tools such as FitLins [3]. Finally, several surface plotting enhancements are in progress including improving the API for background maps (see Fig2). Conclusion Nilearn is extensively used by researchers of the neuroimaging community due to its implementations of well-founded methods and visualization tools which are often essential in brain imaging research for quality control and communicating results. Recent work has highlighted areas where more active work is needed to scale the project both technically and socially, including: working with large datasets, better supporting analyses on the cortical surface, and advancing standard practice in neuroimaging statistics through active community outreach. References [1] Poldrack, R., Gorgolewski, K., Varoquaux, G. (2019). Computational and Informatic Advances for Reproducible Data Analysis in Neuroimaging Annual Review of Biomedical Data Science 2(1), 119-138. https://dx.doi.org/10.1146/annurev-biodatasci-072018-021237 [2] Pedregosa, F., Varoquaux, G., Gramfort, A., Michel, V., Thirion, B., Grisel, O., Blondel, M., Prettenhofer, P., Weiss, R., Dubourg, V., Vanderplas, J., Passos, A., Cournapeau, D., Brucher, M., Perrot, M., Duchesnay, E. (2011). Scikit-learn: Machine Learning in Python, Journal of Machine Learning Research, 12, 2825-2830. [3] Markiewicz, C. J., De La Vega, A., Wagner, A., Halchenko, Y. O., Finc, K., Ciric, R., Goncalves, M., Nielson, D. M., Kent, J. D., Lee, J. A., Bansal, S., Poldrack, R. A., Gorgolewski, K. J. (2022). poldracklab/fitlins: 0.11.0 (0.11.0). Zenodo. https://doi.org/10.5281/zenodo.7217447This poster was presented at OHBM 2023

Modéliser et optimiser un réseau électrique distribué : une approche des systèmes complexes des "prosumers" dans le smart grid

This thesis is devoted to the study of agents called prosumers because they can, from renewable, both produce and consume electricity. If their production exceeds their own needs, they are looking to sell their surplus on electricity markets. We propose to model these prosumers from meteorological data, which has allowed us to highlight non trivial spatial and temporal correlations. This is of great importance for aggregators that form portfolios of equipments to sell services to the network operator. As an aggregator is bound by a contract with the operator, it can be subject to penalties if it does not fulfill its role. We show that these correlations impact the stability of aggregates, and therefore the risk taken by the aggregators. We propose an algorithm minimizing the risk of the aggregations, while maximizing the expected gain. The placement of storage devices in a network where generators and loads are stochastic and not fixed is complex. We propose to answer this question with control theory. We model the electrical system as a network of coupled oscillators, whose phase angles dynamics is an approximation of the actual dynamics of the system. The goal is to find the subset of nodes in the graph that, during a disturbance of the system, allows returning to equilibrium if the right signals are injected and this with a minimum energy. We propose an algorithm to find a near optimal placement to minimize the average energy controlCette thèse est consacrée à l'étude d’agents appelés prosumers parce qu’ils peuvent, à partir d’énergies renouvelables, à la fois produire et consommer de l’électricité. Si leurs productions excèdent leurs propres besoins, ceux-ci cherchent à vendre leur surplus sur des marchés de l’électricité. Nous proposons de modéliser ces prosumers à partir de données météorologiques, ce qui nous a permit de mettre en évidence des corrélations spatio-temporelles non triviales, d'une grande importance pour les agrégateurs qui forment des portefeuilles d’équipements afin de vendre des services à l'opérateur du réseau. Comme un agrégateur est lié par un contrat avec l'opérateur, il peut faire l'objet de sanctions s’il ne remplit pas son rôle. Nous montrons que ces corrélations impactent la stabilité des agrégats, et donc le risque encouru par les agrégateurs. Nous proposons un algorithme minimisant le risque d'un ensemble d’agrégations, tout en maximisant le gain attendu. La mise en place de dispositifs de stockage dans un réseau où les générateurs et les charges sont dynamiques et stochastiques est complexe. Nous proposons de répondre à cette question grâce à la théorie du contrôle. Nous modélisons le système électrique par un réseau d'oscillateurs couplés, dont la dynamique des angles de phase est une approximation de la dynamique réelle du système. Le but est de trouver le sous-ensemble des nœuds du graphe qui, lors d'une perturbation du système, permet le retour à l'équilibre si les bons signaux sont injectés, et ceci avec une énergie minimum. Nous proposons un algorithme pour trouver un placement proche de l'optimum permettant de minimiser l'énergie moyenne de contrôl

Les théories de la demande de raccordement téléphonique

Revue économique ECONOMETRIC MODELS OF TELECOMMUNICATIONS FIRMS : A SURVEY ferenc Kiss, bernard lefebvke The 15-year history of aggregate econometric models of American and Canadian télécommunications firms is outlined. Nearly forty models of AT&T and Bell Canada are examined in some détail. The survey concludes that thé econometric models succeeded in producing robust empirical évidence on fundamental économie characteristics of télécommunications firms, such as those associated with factor demand, factor substitution, économies of scale and technological changes. Attention is drawn to thé économie similarities of AT&T and Bell Canada. The most impor­tant failure of thé surveyed econometric models is identified as their inability to quantify various forms of internai économies. Expected directions of future research are described. THE THEORETICAL APPROACH TO PRICING AND COST ALLOCATION FOR TELECOMMUNICATION SERVICES david encaoua., michel moreaux This paper reviews some économie principles concerning pricing policy and cost allocating methods in télécommunications. It focuses on thé links between sustai-nable market priée equilibria and public pricing rules. The first part is devoted to questions of allocative efficiency and equity. Allocative efficiency is investigated under thé second best analysis framework, while equity is related to thé search af some cross subsidy free priées. Average cost pricing rules in thé case of multi-product activities are also investigated. The second part is devoted to properties of non uniform priées and gives some numerical simulations of welfare gains associated to différent pricing rules. TELEPHONE ACCESS AND USAGE : JOINT MODELIZATION AND OPTIMAL PRICING nicolas curien An integrated micro-économie modelization is developped, in order to discuss thé main characteristics of téléphone demand and to dérive optimal pricing rules. Téléphone demand is described as a joint demand for two commodities : (i) optional usage (made possible by access to thé network), and (ii) actual usage. It is shown that expectations of future usage do influence individual décisions of access and network equilibrium. Revenues of thé télécommunication firm and user's surplus are calculated at equilibrium, disclosing thé positive externality which is brought to thé existing subscribers when a new one is connected. There also exists a usage externality due to thé utility yielded by incoming téléphone calls. Making simple assumptions on network costs, thé impact of thé access and usage externalities on optimal pricing is discussed : first and second best priées are successively examined and compared to thé priées which would be set by a profit maximizing unregulated monopoly. 550Les théories de la demande de raccordement téléphonique L'article consiste en une discussion de modèles élaborés dans les années 1970 pour rendre compte de la diffusion du service téléphonique. Ces modèles font jouer un rôle essentiel à l'externalité positive de consommation qui est associée à la croissance d'un réseau de communication : le réseau étant d'autant plus utile qu'il est plus étendu, il croît par effet « boule de neige », attirant en son sein des individus dont le revenu est de plus en plus faible. L'étude dynamique et statique de ce processus de diffusion montre l'existence d'un nombre impair de tailles d'équilibre pour le parc téléphonique, alternativement stables et instables. Les différents modèles originellement apparus dans la littérature sont d'abord commentés en détail, puis on développe à partir de cette matière les fondements micro-économiques d'une théorie intégrée de la demande d'accès à un réseau de télécommunication.Curien Nicolas, Gensollen Michel. Les théories de la demande de raccordement téléphonique. In: Revue économique, volume 38, n°2, 1987. pp. 203-256

De la théorie des structures industrielles à l'économie des réseaux de télécommunication

From the theory of industry structure to the economics of telecommunication networks The theoretical notions of efficiency, contestability, and sustainability of an industry structure are recalled. The application of the latter concepts is then discussed. It is argued that the cost function which is relevant to the analysis of the industry and the one which can be derived from econometrics are generally different. Moreover, as will be emphasized, the cost function is influenced by the structure of the industry through changes in technology and priees of inputs. Rather than a global study of the cost function, our analysis is an attempt to understanding in depth the economies of the network. The classical distinction between local and toll services does not prove to be very useful and will be replaced by the one between two fundamental functions in the network : circuit routing through trans­mission facilities, and traffic routing through switching equipments. On the basis of the economie characteristics of these two functions, it is prescribed that deregulation in France should only extend to traffic routing and should preserve the trans­mission network as a whole, i.e. trunk circuits as well as local loops : restricting the scope of monopoly to local operations only, as in the United States, would indeed cause a costly loss of scale economies and lead to a socially intolerable deavaraging of access charges.De la théorie des structures industrielles à l'économie des réseaux de télécommunication Après un rappel des notions d'efficacité, de contestabilité et de soutenabilité d'une configuration de marché, l'article propose une critique de l'application de ces concepts. En effet, la fonction de coût qui sert à la discussion de la structure d'une industrie, et celle obtenue par un éventuel ajustement économétrique, n'ont pas en général la même définition. De plus, l'influence de la structure du marché sur les coûts, à travers le progrès technique et les prix des facteurs de production, doit faire l'objet d'une analyse particulière. A l'analyse globale d'une fonction de coût des télécommunications, on préférera une réflexion plus précise sur l'économie des réseaux. Celle-ci conduira à substituer, à la distinction entre réseaux locaux et interurbains, l'articulation entre le transport des informations (transmission) et leur acheminement (commutation). Les caractéristiques économiques de ces deux fonctions mènent à proposer, en cas de déréglementation, une certaine ouverture à la concurrence pour les services d'acheminement, et la protection du monopole de la transmission dans son ensemble (transmission interurbaine et distribution locale) : limiter l'extension du monopole aux seuls réseaux locaux de distribution, comme aux États-Unis, serait en effet coûteux en termes de perte d'économies d'échelle, et aboutirait à une dépéréquation socialement insupportable des tarifs d'accès..Curien Nicolas, Gensollen Michel. De la théorie des structures industrielles à l'économie des réseaux de télécommunication. In: Revue économique, volume 38, n°2, 1987. pp. 521-578

The opening-up of networks: planning or competition in the telecommunication industry and other public utilities

The present progress in information processing technology is having a drastic impact on the telecommunications industry: the switching of traffic in the network, which so far has been handled by the monopolies in charge of the infrastructures, is more and more directly operated by business customers and vendors of the so-called value-added services. A similar evolution can be observed in most networks: new firms operate as intermediaries between the end-users and the transmission or distribution facilities; they provide tailored services to the customers and set up discriminatory prices. Such a deregulation process accentuates the breaking-down of many public networks into two components: on the one hand, the network made up of the infrastructures, on the other hand, the command networks which monitor the former and use it as a support in the provision of differentiated services. Whereas the network of infrastructures is a natural monopoly, which should, however, be disciplined through the threat of potential competition, the command networks are likely to be offered on a competitive market; the latter should nevertheless be organized, if not planned, because of externalities such as security and compatibility.Le développement actuel des techniques de traitement de l'information bouleverse l'économie des réseaux de télécommunications: la commutation du trafic, jusqu'ici assurée par les monopoles gestionnaires des infrastructures, est de plus en plus directement mise en oeuvre par les clients professionnels et par certaines firmes intermédiaires offrant des services dits à valeur ajoutée. Une évolution analogue marque d'ailleurs la plupart des réseaux: des entreprises s'interposent entre les clients finals et les équipements de distribution ou de transport, en fournissant des services sur mesure et en pratiquant une tarification discriminante. Au sein de chaque réseau public, cette déréglementation souligne la séparation entre deux composantes: d'une pan, le réseau des infrastructures; d'autre pan, les réseaux de commande qui pilotent le premier afin d'en optimiser le fonctionnement et d'en faire le support de services différenciés. Alors que le réseau des infrastructures forme un monopole naturel dont il convient cependant d'animer la gestion par la menace d'une concurrence potentielle, les réseaux de commande ont vocation à être fournis sur un marché concurrentiel, qui doit toutefois être organisé, sinon planifié, en raison ďexternalités de sécurité et d'interopérabilité.Curien Nicolas, Gensollen Michel. The opening-up of networks: planning or competition in the telecommunication industry and other public utilities. In: Flux, n°1, 1990. pp. 21-42

La communication dans un groupe de travail : l'analyse du fonctionnement interactif et le marché des téléconférences

Gensollen Michel, Curien Nicolas. La communication dans un groupe de travail : l'analyse du fonctionnement interactif et le marché des téléconférences. In: Réseaux, volume 3, n°10, 1985. Téléconférence. pp. 39-74