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Publications

Publications by CPES

2006

Integrated reliability management in industrial production systems

Authors
Faria, JA; Matos, MA; Nunes, EM;

Publication
Safety and Reliability for Managing Risk, Vols 1-3

Abstract
The paper presents a methodology for the analysis of just-in-time production systems that are expected to deliver a fixed quantity of parts to its customers on a periodical basis, and whose equipment is submitted to random failure and repair processes. The methodology is based on the determination of the density function of T-H, the cumulated halting time of the production system between deliveries. The paper firstly shows how this function can be obtained from the internal structure of the system and individual equipment failure processes. Then, it shows how the reliability of the deliveries, and several production costs, e.g., extra work, delivery failures penalties, loss of sales profit, and safety stocks, may be assessed using this function. The practical application and usefulness of the methodology is illustrated in the final part of the paper for a typical production system of the automotive industry.

2006

A model to remarry the active/reactive power dispatches in competitive environment and active/reactive marginal prices computation

Authors
Gomes, MH; Saraiva, JT;

Publication
2006 IEEE/PES TRANSMISSION & DISTRIBUTION CONFERENCE & EXPOSITION: LATIN AMERICA, VOLS 1-3

Abstract
This paper describes a mathematical formulation for the active/reactive dispatch in electricity markets, including a number of issues present in market models used in several countries. Traditional market approaches are implemented considering a sequence of activities namely in terms of active power dispatch and ancillary services. However, these two problems are coupled in the sense that dispatching reactive power is not independent from the active power scheduling of generators. The proposed model admits that it is known the purely economic pool dispatch together with bilateral contracts and then it aims at dispatching reactive resources considering voltage and branch limit constraints and constraints reflecting the alternator capability curve. As a sub-result, this formulation also outputs nodal active and reactive marginal prices that can be useful to build tariff schemes. Finally, the paper includes a case study based on the IEEE 30 bus/41 branch system to illustrate the obtained results and their interest for electricity markets.

2006

A fuzzy decision model for the active and reactive dispatch in market environment

Authors
Gomes, MH; Saraiva, JT;

Publication
2006 9th International Conference on Probabilistic Methods Applied to Power Systems, PMAPS

Abstract
This paper presents a mathematical formulation for the active/reactive dispatch in electricity markets, recognizing that the typical sequential activities organized in terms of pool markets and the dispatch of ancillary services may lead to economic inefficiencies or technical difficulties. The developed model admits that it is known the purely economic pool dispatch and then it aims at dispatching reactive resources considering voltage and branch limit constraints and constraints reflecting the alternator capability curve. We also admitted that some constraints have a soft nature and used a symmetrical fuzzy decision formulation to model this aspect within an SLP based algorithm. Finally, the paper includes a case study based on the IEEE 24 bus/38 branch system to illustrate the results obtained with the developed approach. © Copyright KTH 2006.

2006

A fuzzy decision model for the active and reactive dispatch in market environment

Authors
Gornes, MH; Saraiva, JT;

Publication
2006 International Conference on Probabilistic Methods Applied to Power Systems, Vols 1 and 2

Abstract
This paper presents a mathematical formulation for the active/reactive dispatch in electricity markets, recognizing that the typical sequential activities organized in terms of pool markets and the dispatch of ancillary services may lead to economic inefficiencies or technical difficulties. The developed model admits that it is known the purely economic pool dispatch and then it aims at dispatching reactive resources considering voltage and branch limit constraints and constraints reflecting the alternator capability curve. We also admitted that some constraints have a soft nature and used a symmetrical fuzzy decision formulation to model this aspect within an SLP based algorithm. Finally, the paper includes a case study based on the IEEE 24 bus/38 branch system to illustrate the results obtained with the developed approach.

2006

Defining control strategies for microgrids islanded operation

Authors
Lopes, JAP; Moreira, CL; Madureira, AG;

Publication
IEEE TRANSACTIONS ON POWER SYSTEMS

Abstract
This paper describes and evaluates the feasibility of control strategies to be adopted for the operation of a microgrid when it becomes isolated. Normally, the microgrid operates in interconnected mode with the medium voltage network; however, scheduled or forced isolation can take place. In such conditions, the microgrid must have the ability to operate stably and autonomously. An evaluation of the need of storage devices and load shedding strategies is included in this paper.

2006

Optimum generation control in wind parks when carrying out system operator requests

Authors
de Almeida, RG; Castronuovo, ED; Lopes, JAP;

Publication
IEEE TRANSACTIONS ON POWER SYSTEMS

Abstract
This paper proposes an optimized dispatch control strategy for active and reactive powers delivered by a doubly fed induction generator in a wind park. In this control approach, wind turbines are supposed to operate over a deloaded maximum power extraction curve and with respond to a supervisory wind farm control after a request from a system operator for adjusting the outputs of the wind park. The definition of the active and reactive powers operating points, for each wind turbine, is defined from an optimization algorithm that uses the primal-dual predictor corrector interior point method. The control strategy used at the wind generator level exploits a combination of pitch control and control of the static converters to adjust the rotor speed for the required operation points. A small wind park is used to illustrate the effectiveness of the developed approach.

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