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Publications

Publications by Manuel Matos

2001

An analytical methodology for the dependability evaluation of non-Markovian systems with multiple components

Authors
Faria, JA; Matos, MA;

Publication
RELIABILITY ENGINEERING & SYSTEM SAFETY

Abstract
Very often, in dependability evaluation, the systems under study are assumed to have a Markovian behavior. This assumption highly simplifies the calculations, but introduces significant errors when the systems contain deterministic or quasi-deterministic processes, as it often happens with industrial systems. Existing methodologies for non-Markovian systems, such as device stage method [1], the supplementary variables method or the imbedded Markov chain method [2] do not provide an effective solution to deal with this class of systems, since their usage is restricted to relatively simple and small systems. This paper presents an analytical methodology for the dependability evaluation of non-Markovian discrete state systems, containing both stochastic and deterministic processes, along with an associated systematic resolution procedure suitable for numerical processing. The methodology was initially developed in the context of a research work [3] addressing the dependability modeling, analysis and evaluation of large industrial information systems. This paper, extends the application domain to the evaluation of reliability oriented indexes and to the assessment of multiple components systems. Examples will be provided throughout the paper, in order to illustrate the fundamental concepts of the methodology, and to demonstrate its practical usefulness.

2012

Evaluating the Interest in Installing Microgrid Solutions

Authors
Vasiljevska, J; Lopes, JP; Matos, MA;

Publication
Electricity Journal

Abstract
A decision-making approach based on multi-criteria techniques can help to make the massive deployment of the microgrid concept a viable solution, potentially leading to proper incentive mechanisms for distribution system operators, microgeneration owners and loads. © 2012 Elsevier Inc.

2006

Optimal design of work-in-process buffers

Authors
Faria, J; Matos, M; Nunes, E;

Publication
INTERNATIONAL JOURNAL OF PRODUCTION ECONOMICS

Abstract
When customers demand for very short lead-times and for a strict respect of the delivery schedules, it becomes difficult to avoid the existence of relatively large work-in-process buffers. As the buffers will also increase dramatically the production costs, their design (location and capacity) should be carefully analyzed and optimized, a task that becomes rather complex for large production systems. This paper firstly introduces a series of fundamental concepts related to the reliability of production systems. Then, the rationale of an analysis method oriented to this class of systems will be presented, together with its two main components, the modelling framework and the evaluation algorithm. The method allows analysing several issues of the design and operation of the production systems, namely the redundancy of equipment, the layout of the cells and the maintenance policies. To illustrate its practical usefulness and enlighten the kind of results that the method can provide, a numerical example concerning the design of work-in-process buffers of a just-in-time manufacturing system will be presented in the final part of the paper.

2012

Evaluating the impacts of the multi-microgrid concept using multicriteria decision aid

Authors
Vasiljevska, J; Pecas Lopes, JAP; Matos, MA;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
Exploiting the benefit that one can get from large scale integration of microgeneration (mu G) requires the adoption of different control strategies at different distribution network levels. In that sense, MicroGrid (MG) and Multi MicroGrids (MMG) concepts may be seen as a way to facilitate integration of higher levels of mu G into the system. This paper describes new control and management functionalities used to take profit from the presence of microgeneration and active loads under MG and MMG concepts. MultiCriteria Decision Aid (MCDA) techniques are used to capture decision maker's preferences in evaluating the impact of MG and MMG concepts deployment and help selecting the best development strategy.

2012

A new clustering algorithm for load profiling based on billing data

Authors
Fidalgo, JN; Matos, MA; Ribeiro, L;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
In open energy markets, the settlement process between distribution operators and traders is made on an hourly (or 15 min) basis, while LV consumers' billing data continues to result from monthly energy bills. In order to reconcile these two different realities, load profiling is used as a means to redistribute the consumed energy of each trader's portfolio by hourly intervals, according to recorded consumption patterns. This paper presents a new clustering approach to derive typical load diagrams that can be used in the process. The algorithm uses real load diagrams obtained in measurement campaigns to define classes (in the billing information space) that maximize the compactness of the diagrams in each class. The methodology was developed in a project with EDP Distribution (the Portuguese distribution system operator) and the result was approved by the Regulatory Authority that adopted the proposed profiles for market use.

2009

Avoided losses on LV networks as a result of microgeneration

Authors
Costa, PM; Matos, MA;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
In the scope of the discussions about microgeneration (and microgrids), the avoided electrical losses are often pointed out as an important value to be credited to those entities. Therefore, methods to assess the impact of microgeneration on losses must be developed in order to support the definition of a suitable regulatory framework for the economic integration of microgeneration on distribution networks. This paper presents an analytical method to quantify the value of avoided losses that microgeneration may produce on LV networks. Intervals of expected avoided losses are used to account for the variation of avoided losses due to the number, size and location of microgenerators, as well as for the kind of load distribution on LV networks.

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