Comparison of different repetitive control architectures: synthesis and comparison. Application to VSI Converters

Repetitive control is one of the most used control approaches to deal with periodic references/disturbances. It owes its properties to the inclusion of an internal model in the controller that corresponds to a periodic signal generator. However, there exist many different ways to include this internal model. This work presents a description of the different schemes by means of which repetitive control can be implemented. A complete analytic analysis and comparison is performed together with controller synthesis guidance. The voltage source inverter controller experimental results are included to illustrative conceptual developmentsPeer ReviewedPostprint (published version

Robust H8 design for resonant control in a CVCF inverter application over load uncertainties

CVCF (constant voltage, constant frequency) inverters are electronic devices used to supply AC loads from DC storage elements such as batteries or photovoltaic cells. These devices are used to feed different kinds of loads; this uncertainty requires that the controller fulfills robust stability conditions while keeping required performance. To address this, a robust H8 design is proposed based on resonant control to track a pure sinusoidal voltage signal and to reject the most common harmonic signals in a wide range of loads. The design is based on the definition of performance bounds in error signal and weighting functions for covering most uncertainty ranges in loads. Experimentally, the H8 controller achieves high-quality output voltage signal with a total harmonic distortion less than 2%Peer ReviewedPostprint (published version

An adaptive disturbance rejection control scheme for voltage regulation in DC micro-grids

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Uncertain generation by renewable sources and load variations have resulted in adding energy storage systems in the grid to maintain grid parameters (voltage, frequency) within prescribed limits. The disturbances being non-deterministic in nature, the voltage regulation control by the storage systems relies mostly on dual loop architecture with an outer voltage and inner current loop. Improvement in controller dynamics can be achieved through feed forward of disturbance profile but at expense of additional sensors and communication in the grid. This work explores the application of an adaptive disturbance rejection control scheme for disturbance estimation (without using additional sensors) employing an extended state and proportional integral observer (PI+ESO). The proposed observer aim to achieve robust disturbance estimation under grid parameter uncertainty. The effectiveness of the proposed scheme over the conventional one will be put forward through H8 and H2 norm analysis of the system. The design and simulation results of the proposed scheme will be presented in this work.Peer ReviewedPostprint (author's final draft

Notas sobre novos desafios da cooperação judiciária internacional em matéria penal

Este artigo enuncia alguns desafios da cooperação internacional em matéria penal de uma perspectiva de obtenção e valoração da prova. São identificados desafios decorrentes da actuação de novos actores institucionais, em particular a Procuradoria Europeia e o Tribunal de Justiça da União Europeia, bem como ao nível da intervenção de actores privados. São ainda tratados desafios em matéria de valoração da prova transfronteiriça. O artigo chama a atenção para a necessidade de intervenção legislativa, sobretudo a nível interno em Portugal, no âmbito da articulação dos novos instrumentos do direito da União Europeia com o direito interno, e termina deixando referidos possíveis futuros paradigmas na obtenção de prova transfronteiriça, lançando o repto para que a intervenção nesta matéria seja ponderada cautelosamente e procure fazer face às insuficiências presentes, quer da perspectiva da defesa, quer da efectividade das investigações transfronteiriças.This article sets out some challenges of international cooperation in criminal matters from a perspective of the gathering and use and assessment of evidence. Challenges arising from the actions of new institutional actors, in particular the European Public Prosecutor' s Office and the Court of Justice of the European Union, as well as the intervention of private actors are identified. Challenges in the use and assessment of cross-border evidence are also addressed. The article draws attention to the need for legislative intervention, particularly within Portugal, in the context of the articulation of the new instruments of European Union law with national law, and ends by referring to possible future paradigms in obtaining cross-border evidence, calling upon intervention in this area to be carefully considered and to address the shortcomings present both from the point of view of the defense and of the effectiveness of cross-border investigations

Theoretical Model to Analyze the Influence of Outsourcing on Industrial Business Value Creation

This paper focuses on the discussion concerning the way how outsourcing decisions, regarding one or more of the companies’ functions, can positively affect the internal value creation process and, thus, business performance, in both quantitative and qualitative terms. Based on the existing literature about Outsourcing a theoretical model was conceptualized to analyze and evaluate the influence of outsourcing on industrial and business value creation. The investigation process involved the collection of data through a questionnaire, applied to a representative set of SME’s from the Portuguese economic fabric – resorting. The main conclusions to be taken from this research are: (i) that outsourcing does present a verifiable set of statistically relevant direct and indirect effects upon the internal value creation process and, moreover, (ii) that outsourcing does generate a positive, and statistically relevant, indirect effect on business performance, through the internal value creation process.info:eu-repo/semantics/publishedVersio

Advances and trends for the development of ambient-assisted living platforms

Ambient Assisted Living (AAL) and Ambient Intelligence (AmI) try to achieve a future where technology surrounds the users and helps them in their daily lives. In this sense, the urgent need of solutions to cover the rapid increase of the elderly population with chronic diseases led to the increase of projects related with AAL and AmI. During the latest years, several projects have been proposed to tackle different medical problems, some building devices and others services. This paper presents iGenda and its evolution, the UserAccess, with the main objective of developing an AAL platform. It features an analysis of the latest developments and points future directions for the work. These projects display the importance of the interoperability of the platforms, demonstrating a case study for AAL development.This work has been supported by FCT – Fundação para a Ciência eTecnologia within the Project Scope: UID/CEC/00319/2013 and COMPETE: POCI-01-0145-FEDER007043. A. Costa thanks the Fundação para a Ciência e a Tecnologia (FCT) the post-doc scholarship with the ref. SFRH/BPD/102696/2014. This work is also partially supported by the MINECO/FEDER TIN2015-65515-C41-R.info:eu-repo/semantics/publishedVersio

Testing the Significance of the Linear Regression Coefficients: Exploring Some Estimators for the Autocorrelation Function

This work addresses the problem of testing the significance of the slope of a linear trend with and without an eventual seasonal effect. It is assumed that the error term follows an AR(1), and that the autoregressive parameter is unknown. The autoregressive parameter is obtained through some competing estimators, namely, a parametric version, a modified Kendall’s correlation coefficient, and another non-parametric counter part developed earlier in the context of the state space models. The accuracy of the estimation of this parameter is also analyzed. The performance of the tests considering the three estimators simultaneously is compared through a Monte Carlo simulation study under different assumptions. The study is extended in order to compare the slopes of two or more periods in the same time series