2008
Autores
Lopes, FP; Oliveira, PS; Reis, LP; Araujo, RE;
Publicação
2008 INTERNATIONAL SYMPOSIUM ON POWER ELECTRONICS, ELECTRICAL DRIVES, AUTOMATION AND MOTION, VOLS 1-3
Abstract
Nowadays the education on electrical engineering, in European countries, is facing on one side a high demand for engineers coming from industry and on the other hand a reduced interest from younger generation, whose interest is highly polarised by information and communication technologies. A permanent-magnet synchronous motor (PMSM) controller for an electric wheelchair demo track has been set up, in order to reinforce the demonstrative aspects of modern technology as a contribution to the motivation of students for the industrial electronics world. The motors are controlled at different operating conditions by means of a current control law using a low cost microcontroller board. The prototype has been designed specifically to meet the requirement of low cost and it contains all of the active functions required to implement the control of the electric wheelchair. The resulting prototype has a very low cost compared to commercial "black-box" modules. This prototype allows a first approach between a real technical system and power electronics, increasing the student's motivation for the power electronics area and to significantly enhance their skills to measure and interpret measurements and comparing those to theoretical predictions.
2008
Autores
Araujo, RE; Ribeiro, G; de Castro, RP; Oliveira, HS;
Publicação
IECON 2008: 34TH ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY, VOLS 1-5, PROCEEDINGS
Abstract
Battery-powered electric vehicle appear to be one of the viable solutions for the growing concerns for environmental protection and the fast rate of depletion of world fuel oil supply. This type of vehicle can become a viable alternative to the internal combustion engine only if they are able to meet certain reliability, safety, performance, and cost criteria. In addition, this type of electrical vehicles have serious disadvantages because of the limitation on cruising range imposed by weight, capacity of the electric accumulators and long recharging time. Improvement of efficiency of induction motor traction drives is an important issue in pure electric vehicles to improve the running distance on one charge. In this paper, the authors evaluate a loss-minimization algorithm (LMA) by considering their influence on the performance of the vehicle. The evaluation of the proposed LMA is demonstrated experimentally under different operating conditions of the vehicle.
2008
Autores
Azevedo, F; Vale, ZA;
Publicação
2008 5TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ELECTRICITY MARKET, VOLS 1 AND 2
Abstract
Short-term risk management is highly dependent on long-term contractual decisions previously established; risk aversion factor of the agent and short-term price forecast accuracy. Trying to give answers to that problem, this paper provides a different approach for short-term risk management on electricity markets. Based on long-term contractual decisions and making use of a price range forecast method developed by the authors, the short-term risk management tool presented here has as main concern to find the optimal spot market strategies that a producer should have for a specific day in function of his risk aversion factor, with the objective to maximize the profits and simultaneously to practice the hedge against price market volatility. Due to the complexity of the optimization problem, the authors make use of Particle Swarm Optimization (PSO) to find the optimal solution. Results from realistic data, namely from OMEL electricity market, are presented and discussed in detail.
2008
Autores
Campos, FA; Villar, J; Barquin, J; Ruiperez, J;
Publicação
ENGINEERING OPTIMIZATION
Abstract
Game theory has traditionally used real-valued utility functions in decision-making problems. However, the real information available to assess these utility functions is normally uncertain, suggesting the use of uncertainty distributions for a more realistic modelling. In this sense, utilities results or pay-offs have been normally modelled with probability distributions, assuming random uncertainty. However, when statistical information is unavailable, probability may not be the most adequate paradigm, and can lead to very large execution times when some real complex problems are addressed. In this article possibility distributions are used to model the uncertainty of utility functions when the strategies are probability distributions (mixed strategies) over a set of original and discrete strategies (pure strategies). Two dual approaches to solve the resulting non-cooperative fuzzy games are proposed: modelling players' risk aversion, and thus providing realistic conservative strategies. Two examples show the robustness of the strategies obtained with the proposed approaches.
2008
Autores
Campos, FA; Villar, J; Barquin, J; Reneses, J;
Publicação
IET GENERATION TRANSMISSION & DISTRIBUTION
Abstract
It is widely known and accepted that Nash equilibrium suitably models agents' behavior in electricity markets, since it is coherent with the common sense of their simultaneous profits maximisation. In the literature, these approaches are usually addressed using deterministic representations, despite the fact that electricity markets are highly conditioned by the uncertainty in demand or in agents' bidding strategies. Only some equilibrium-modelling approaches under uncertainty can be found in the literature, most of them using probability distributions. However, probability approaches may lead to very complex formulations and generally require restrictive assumptions (such as normality or independence) that can hardly be verified in real complex problems. A conjectured-price-response equilibrium model that uses LR-possibility distributions to represent the uncertainty of the residual demand curves faced by the participant agents is proposed. Modelling the risk-aversion attitudes of the agents, the resulting possibilistic equilibrium is transformed into a simplified deterministic one, which is solved with a new globally convergent algorithm for variational inequalities problems. Some interesting results for a real-size electricity system show the robustness of this new approach when compared with other risk-neutral approaches.
2008
Autores
Oliveira, F; Madureira, A; Donsión, MP;
Publicação
Renewable Energy and Power Quality Journal
Abstract
Most of the Power Quality surveys in industrialized countries are performed according to the parameters defined in the EN50160 standard, which sets one-week measurement periods with ten-minute sampling time for most power quality disturbances such as flicker and harmonics. Both the sampling periods and the measurement period have a great influence on the significance of the values obtained as well as on the conclusions taken. In this paper, an attempt is made to compare the values obtained with different sample frequencies and time windows, working on instantaneous flicker (Ifl) values for a wind turbine over three weeks.
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