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Publications

2019

A cluster-based optimization approach to support the participation of an aggregator of a larger number of prosumers in the day-ahead energy market

Authors
Iria, J; Soares, F;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
Optimizing the participation of a large number of prosumers in the electricity markets is a challenging problem, especially for portfolios with thousands or millions of flexible resources. To address this problem, this paper proposes a cluster-based optimization approach to support an aggregator in the definition of demand and supply bids for the day-ahead energy market. This approach consists of two steps. In the first step, the aggregated flexibility of the entire portfolio is computed by a centroid-based clustering algorithm. In the second step, the supply and demand bids are defined by an optimization model that can assume the form of a deterministic or a two-stage stochastic problem. A case study of 10,000 prosumers from the Iberian market is used to evaluate and compare the performance of the bidding optimization models with and without pre-clustering. The numerical results show that the optimized bidding strategies outperform an inflexible strategy by more than 20% of cost savings. The centroid-based clustering algorithm reduces effectively the execution times of the bidding optimization problems, without affecting the quality of the energy bids.

2019

Simultaneous lotsizing and scheduling considering secondary resources: a general model, literature review and classification

Authors
Woerbelauer, M; Meyr, H; Almada Lobo, B;

Publication
OR SPECTRUM

Abstract
Typical simultaneous lotsizing and scheduling models consider the limited capacity of the production system by respecting a maximum time the respective machines or production lines can be available. Further limitations of the production quantities can arise by the scarce availability of, e.g., setup tools, setup operators or raw materials which thus cannot be neglected in optimization models. In the literature on simultaneous lotsizing and scheduling, these production factors are called secondary resources. This paper provides a structured overview of the literature on simultaneous lotsizing and scheduling involving secondary resources. The proposed classification yields for the first time a unified view of scarce production factors. The insights about different types of secondary resources help to develop a new model formulation generalizing and extending the currently used approaches that are specific for some settings. Some illustrative examples demonstrate the functional principle and flexibility of this new formulation which can thus be used for a wide range of applications.

2019

Optimal Spinning Reserve Allocation in Presence of Electrical Storage and Renewable Energy Sources

Authors
Javadi, MS; Lotfi, M; Gough, M; Nezhad, AE; Santos, SF; Catalao, JPS;

Publication
2019 IEEE INTERNATIONAL CONFERENCE ON ENVIRONMENT AND ELECTRICAL ENGINEERING AND 2019 IEEE INDUSTRIAL AND COMMERCIAL POWER SYSTEMS EUROPE (EEEIC / I&CPS EUROPE)

Abstract
This paper investigates the optimal allocation of Spinning Reserve (SR) for power systems in the presence of Renewable Energy Sources (RES) and Electrical Energy Storage (EES) devices. This is done in order to reduce the system's dependency on thermal generation units and the decrease total daily operational cost. A Security Constrained Unit Commitment (SCUC) model for a typical power system was used, which includes thermal and renewable generation units and EES devices in the form of batteries. In the proposed model, the hourly operation strategy is determined by adopting a predetermined level of SR. In order to optimize SR requirements, the Independent System Operator (ISO) runs the SCUC problem and determines the minimum SR that should be provided by generation units and EES devices. The simulation results illustrate that by optimizing the operation of batteries, the ISO can effectively reduce the required capacity of thermal units. Therefore, optimal SR allocation under RES uncertainty is determined in this study.

2019

Multi-Agent Deep Reinforcement Learning with Emergent Communication

Authors
Simoes, D; Lau, N; Reis, LP;

Publication
2019 INTERNATIONAL JOINT CONFERENCE ON NEURAL NETWORKS (IJCNN)

Abstract
When compared with their single-agent counterpart, multi-agent systems have an additional set of challenges for reinforcement learning algorithms, including increased complexity, non-stationary environments, credit assignment, partial observability, and achieving coordination. Deep reinforcement learning has been shown to achieve successful policies through implicit coordination, but does not handle partial-observability. This paper describes a deep reinforcement learning algorithm, based on multi-agent actor-critic, that simultaneously learns action policies for each agent, and communication protocols that compensate for partial-observability and help enforce coordination. We also research the effects of noisy communication, where messages can be late, lost, noisy, or jumbled, and how that affects the learned policies. We show how agents are able to learn both high-level policies and complex communication protocols for several different partially-observable environments. We also show how our proposal outperforms other state-of-the-art algorithms that don't take advantage of communication, even with noisy communication channels.

2019

Limits in categories of Vietoris coalgebras

Authors
Hofmann, D; Neves, R; Nora, P;

Publication
MATHEMATICAL STRUCTURES IN COMPUTER SCIENCE

Abstract
Motivated by the need to reason about hybrid systems, we study limits in categories of coalgebras whose underlying functor is a Vietoris polynomial one - intuitively, the topological analogue of a Kripke polynomial functor. Among other results, we prove that every Vietoris polynomial functor admits a final coalgebra if it respects certain conditions concerning separation axioms and compactness. When the functor is restricted to some of the categories induced by these conditions, the resulting categories of coalgebras are even complete. As a practical application, we use these developments in the specification and analysis of non-deterministic hybrid systems, in particular to obtain suitable notions of stability and behaviour.

2019

Predictive Industrial Maintenance with a Viable Systems Model and Maintenance 4.0 [Mantenimiento industrial predictivo con un modelo de sistemas viables y mantenimiento 4.0]

Authors
Camara, RA; Mamede, HS; Santos, VDD;

Publication
2019 8th International Conference on Software Process Improvement, CIMPS 2019 - Applications in Software Engineering

Abstract
In face of the continuously growing process of the fourth industrial revolution, the industries are forced to innovate their industrial manufacturing process to remain competitive and active in the market, perfecting the manufacturing process through new interconnected and autonomous technologies. Since time reduction, quality enhancement and cost reduction for manufacturing of industrial products are the major catalysts of a successful company for the current Era called Maintenance 4.0, this paper proposes to illustrate an Information Systems Architecture where, using the Viable Systems Model, it is possible to perform automatic adjustments in the subsystems related to Cyber-Physical Systems and Manufacturing Execution Systems (MES) within the Digital Manufacturing model and, in addition, to mitigate machine failures through predictive analyzes of massive volumes of data using algorithms with intelligent functions and Data Mining (DM) in order to automatically stabilize the entire system chain quickly and efficiently. © 2019 IEEE.

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