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Chakhchoukh Y.,TU Darmstadt | Panciatici P.,French Electricity Transmission Network | Mili L.,Virginia Polytechnic Institute and State University
IEEE Transactions on Power Systems | Year: 2011

In this paper, the stochastic characteristics of the electric consumption in France are analyzed. It is shown that the load time series exhibit lasting abrupt changes in the stochastic pattern, termed breaks. The goal is to propose an efficient and robust load forecasting method for prediction up to a day-ahead. To this end, two new robust procedures for outlier identification and suppression are developed. They are termed the multivariate ratio-of-medians-based estimator (RME) and the multivariate minimum-Hellinger- distance-based estimator (MHDE). The performance of the proposed methods has been evaluated on the French electric load time series in terms of execution times, ability to detect and suppress outliers, and forecasting accuracy. Their performances are compared with those of the robust methods proposed in the literature to estimate the parameters of SARIMA models and of the multiplicative double seasonal exponential smoothing. A new robust version of the latter is proposed as well. It is found that the RME approach outperforms all the other methods for normal days and presents several interesting properties such as good robustness, fast execution, simplicity, and easy online implementation. Finally, to deal with heteroscedasticity, we propose a simple novel multivariate modeling that improves the quality of the forecast. © 2011 IEEE.

Bontemps S.,French Electricity Transmission Network | Bontemps S.,National Polytechnic Institute of Toulouse | Vendier L.,French Electricity Transmission Network | Vendier L.,National Polytechnic Institute of Toulouse | And 2 more authors.
Journal of the American Chemical Society | Year: 2014

Functionalization of CO2 is a challenging goal and precedents exist for the generation of HCOOH, CO, CH3OH, and CH4 in mild conditions. In this series, CH2O, a very reactive molecule, remains an elementary C1 building block to be observed. Herein we report the direct observation of free formaldehyde from the borane reduction of CO2 catalyzed by a polyhydride ruthenium complex. Guided by mechanistic studies, we disclose the selective trapping of formaldehyde by in situ condensation with a primary amine into the corresponding imine in very mild conditions. Subsequent hydrolysis into amine and a formalin solution demonstrates for the first time that CO2 can be used as a C 1 feedstock to produce formaldehyde. © 2014 American Chemical Society.

Doquet M.,French Electricity Transmission Network
IEEE Transactions on Power Systems | Year: 2015

In development studies carried out on large power systems, a need may arise for a reduction in which whole regions are seen as the nodes of a simplified graph whose edges replace the inter-regional links. The property required from this kind of backbone representation may be that reduced load flows stay close to their physical counterpart on the full grid. In the dc approximation, such a model can consist of a set of impedances attached to each edge, along with a flow characterizing a particular state of the system. The identification of the model accommodating best a large sample of flows, representative of all of their possible diversity, is a nonconvex problem for which two partially convex reformulations are proposed. Simple ad hoc algorithms are introduced as a way to find approximate solutions satisfying first-order optimality conditions. © 2014 IEEE.

Petitet M.,French Electricity Transmission Network
International Conference on the European Energy Market, EEM | Year: 2016

This article deals with the effect of risk aversion on the temporal evolution of electricity generation mix and its consequences for market design. Risk aversion of private investors may have significant effects on their decision especially in the current context of limited economic growth. To analyze this issue, a representation of risk aversion through an exponential utility function is proposed within a simulation tool belonging to System Dynamics. The model is used to test the evolution of installed capacity in a context of stable electricity demand and exogenous entry of wind power under three different market designs (energy-only market with price cap; energy-only market with scarcity pricing and capped energy market plus a capacity mechanism) and for different levels of risk aversion. The results highlight that there are more endogenous closures of power plants when risk aversion increases. The results also emphasize that taking risk aversion can significantly change the comparison of market designs. © 2016 IEEE.

Cazacliu B.,French Electricity Transmission Network | Ventura A.,French Electricity Transmission Network
Journal of Cleaner Production | Year: 2010

Current environmental and economical circumstances accelerate the developments of new concrete constituents. Whereas the process technology impacts the mix-design strategy, it seems obvious that manufacturing process is prone to evolutions. This article presents a method to compare environmental and economical consequences of different technological solutions on the basis of the influence on the cement consumption needed for a given concrete performance. Case study is the choice of dry batch or central mixed concrete production systems for a ready mixed concrete production. The theoretical difference in cement consumption is estimated by considering that the water content fluctuation is by far the dominant factor governing the truck to truck variation. The addition of a mixer is effectively found to contribute to cement reduction. Environmental comparison is performed using an EADT indicator (Environmental Amortization Duration Time) defined in the article, and testing various environmental data. The EADT for energy consumption, released CO 2 and particles are found below 6 years, in the whole range of tested environmental data for an annual production of 40,000 m3 yr -1, with 2 m3 mixer for the central mixed concrete plant. The NOx and SO2 EADT results are found sensitive to the releases of the steel plant. The financial amortization duration time corresponding to the purchase of a mixer, is found less than 2 years. Although the chosen application case is simplified, these results encourage further research. © 2010 Elsevier Ltd. All rights reserved.

Faller P.,French Electricity Transmission Network | Hureau C.,National Polytechnic Institute of Toulouse | Berthoumieu O.,National Polytechnic Institute of Toulouse
Inorganic Chemistry | Year: 2013

Aggregation of amyloid-β (Aβ) by self-assembly into oligomers or amyloids is a central event in Alzheimer's disease. Coordination of transition-metal ions, mainly copper and zinc, to Aβ occurs in vivo and modulates the aggregation process. A survey of the impact of CuII and ZnII on the aggregation of Aβ reveals some general trends: (i) ZnII and CuII at high micromolar concentrations and/or in a large superstoichiometric ratio compared to Aβ have a tendency to promote amorphous aggregations (precipitation) over the ordered formation of fibrillar amyloids by self-assembly; (ii) metal ions affect the kinetics of Aβ aggregations, with the most significant impact on the nucleation phase; (iii) the impact is metal-specific; (iv) CuII and ZnII affect the concentrations and/or the types of aggregation intermediates formed; (v) the binding of metal ions changes both the structure and the charge of Aβ. The decrease in the overall charge at physiological pH increases the overall driving force for aggregation but may favor more precipitation over fibrillation, whereas the induced structural changes seem more relevant for the amyloid formation. © 2013 American Chemical Society.

French Electricity Transmission Network | Date: 2012-10-30

A method for monitoring a high-voltage electric-current transmission line includes: determining (100) the ampacity (A) of the high-voltage line from a distribution temperature, conduction parameters and meteorological parameters; measuring (202) the current strength effectively transmitted by the high-voltage line using at least one sensor; and monitoring (204), by a monitoring device connected to the sensor, an excess of ampacity (A) by the current strength measured. The determining (100) of the ampacity (A) includes: selecting (108, 110, 112, 114, 116) a value of this ampacity (A) by optimizing a probability of exceeding the distribution temperature, with this probability defined based on a joint probability model (P) of operating current strength and temperature that depends on meteorological parameters; and recording (118) the selected ampacity value in a storage unit of the monitoring device.

Saad H.,Ecole Polytechnique de Montréal | Guillaud X.,École Centrale Lille | Mahseredjian J.,Ecole Polytechnique de Montréal | Dennetiere S.,French Electricity Transmission Network | Nguefeu S.,French Electricity Transmission Network
IEEE Transactions on Power Delivery | Year: 2015

A modular multilevel converter control system, based on converter energy storage, is proposed in this paper for two different control modes: active power and dc voltage. The proposed control system decouples the submodule (SM) capacitor voltages from the dc bus voltage. One of the practical applications is the management of active redundant SMs. A practical HVDC system with 401-level MMCs, including 10% redundancy in MMC SMs, is used for validating and demonstrating the advantages of the proposed control system. This paper also presents a novel capacitor voltage balancing control based on $\max$-$\min$ functions. It is used to drastically reduce the number of switchings for each SM and enhances computational efficiency. © 1986-2012 IEEE.

Peralta J.,Ecole Polytechnique de Montréal | Saad H.,Ecole Polytechnique de Montréal | Dennetiere S.,French Electricity Transmission Network | Mahseredjian J.,Ecole Polytechnique de Montréal | Nguefeu S.,French Electricity Transmission Network
IEEE Transactions on Power Delivery | Year: 2012

Voltage-source-converter (VSC) technologies present a bright opportunity in a variety of fields within the power system industry. New modular multilevel converters (MMCs) are expected to supersede two- and three-level VSC-based technologies for HVDC applications due to their recognized advantages in terms of scalability, performance, and efficiency. The computational burden introduced by detailed modeling of MMC-HVDC systems in electromagnetic-transients (EMT)-type programs complicates the study of transients especially when these systems are integrated into a large network. This paper presents a novel average-value model (AVM) for efficient and accurate representation of a detailed MMC-HVDC system. It also develops a detailed 401-level MMC-HVDC model for validating the AVM and studies the performance of both models when integrated into a large 400-kV transmission system in Europe. The results show that the AVM is significantly more efficient while maintaining its accuracy for the dynamic response of the overall system. © 2012 IEEE.

Capitanescu F.,University of Liège | Fliscounakis S.,French Electricity Transmission Network | Panciatici P.,French Electricity Transmission Network | Wehenkel L.,University of Liège
IEEE Transactions on Power Systems | Year: 2012

This paper deals with day-ahead power systems security planning under uncertainties by posing an optimization problem over a set of power injection scenarios that could show up the next day and modeling the next day's real-time control strategies aiming at ensuring security with respect to contingencies by a combination of preventive and corrective controls. We seek to determine whether and which day-ahead decisions must be taken so that, for scenarios over the next day, there still exists an acceptable combination of preventive and corrective controls ensuring system security for any postulated contingency. We formulate this task as a three-stage feasibility checking problem, where the first stage corresponds to day-ahead decisions, the second stage to preventive control actions, and the third stage to corrective post-contingency controls. We propose a solution approach based on the problem decomposition into successive optimal power flow (OPF) and security-constrained optimal power flow (SCOPF) problems of a special type. Our approach is illustrated on the Nordic32 system and on a 1203-bus model of a real-life system. © 1969-2012 IEEE.

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