Blade pitch control malfunction simulation in a wind energy conversion system with MPC five-level converter

This paper is on a wind energy conversion system simulation of a transient analysis due to a blade pitch control malfunction. The aim of the transient analysis is the study of the behavior of a back-to-back multiple point clamped five-level full-power converter implemented in a wind energy conversion system equipped with a permanent magnet synchronous generator. An alternate current link connects the system to the grid. The drive train is modeled by a three-mass model in order to simulate the dynamic effect of the wind on the tower. The control strategy is based on fractional-order control. Unbalance voltages in the DC-link capacitors are lessen due to the control strategy, balancing the capacitor banks voltages by a selection of the output voltage vectors. Simulation studies are carried out to evaluate not only the system behavior, but also the quality of the energy injected into the electric grid.

Effects of pitch area-restrictions on tactical behavior, physical and physiological performances in soccer large-sided games

The aim of this study was to identify how pitch area-restrictions affects the tactical behavior, physical and physiological performances of players during soccer large-sided games. A 10 vs. 9 large-sided game was performed under three experimental conditions: (i) restricted-spacing, the pitch was divided into specific areas where players were assigned and they should not leave it; (ii) contiguous-spacing, the pitch was divided into specific areas where the players were only allowed to move to a neighboring one; (iii) free-spacing, the players had no restrictions in space occupation. The positional data were used to compute players’ spatial exploration index and also the distance, coefficient of variation, approximate entropy and frequency of near-in-phase displacements synchronization of players’ dyads formed by the outfield teammates. Players’ physical and physiological performances were assessed by the distance covered at different speed categories, game pace and heart rate. Most likely higher values were found in players’ spatial exploration index under free-spacing conditions. The synchronization between dyads’ displacements showed higher values for contiguous-spacing and free-spacing conditions. In contrast, for the jogging and running intensity zones, restricted-spacing demanded a moderate effect and most likely decrease compared to other scenarios (~20-50% to jogging and ~60-90% to running). Overall, the effects of limiting players’ spatial exploration greatly impaired the co-adaptation between teammates’ positioning while decreasing the physical and physiological performances. These results allow for a better understanding of players’ decision-making process according to specific task rules and can be relevant to enrich practice task design, such that coaches acknowledge the differential effect by using specific pitch-position areas restrictions.

Alexander Scriabin: the definition of a new sound space in the crisis of tonality

This dissertation describes the new compositional system introduced by Scriabin in 1909– 1910, focusing on Feuillet d’Album op. 58, Poème op. 59, nº1, Prélude op. 59, nº2 and Promethée op. 60. Based upon exhaustive pitch and formal analysis the present study (a) claims the inexistence of non-functional pitches in all analysed works, (b) shows that transpositional procedures have structural consequences on the “basic chord”, and (c) for the first time advances an explanation on the intrinsic relation between the sonata form and the slow Luce line in Promethée op. 60; RESUMO: Sob o título de “Alexander Scriabin: a definição dum novo espaço sonoro na crise da Tonalidade”, a presente tese descreve o novo sistema compositivo introduzido por Scriabin em 1909– 1910, tomando como ponto de partida o estudo de Feuillet d’Album op. 58, Poème op. 59, nº1, Prélude op. 59, nº2 e Promethée op. 60. Baseando-se numa análise exaustiva das alturas e da forma, este estudo (a) conclui pela inexistência de alturas não funcionais em qualquer das obras analisadas, (b) mostra que os procedimentos transpositivos têm consequências estruturais no “acorde básico”, e (c) pela primeira vez explica a estrutura formal de Promethée op. 60 a partir da relação intrínseca entre a sua forma sonata e a linha lenta de Luce.

Control and Supervision of Wind Energy Conversion Systems

This paper is about a PhD thesis and includes the study and analysis of the performance of an onshore wind energy conversion system. First, mathematical models of a variable speed wind turbine with pitch control are studied, followed by the study of different controller types such as integer-order controllers, fractional-order controllers, fuzzy logic controllers, adaptive controllers and predictive controllers and the study of a supervisor based on finite state machines is also studied. The controllers are included in the lower level of a hierarchical structure composed by two levels whose objective is to control the electric output power around the rated power. The supervisor included at the higher level is based on finite state machines whose objective is to analyze the operational states according to the wind speed. The studied mathematical models are integrated into computer simulations for the wind energy conversion system and the obtained numerical results allow for the performance assessment of the system connected to the electric grid. The wind energy conversion system is composed by a variable speed wind turbine, a mechanical transmission system described by a two mass drive train, a gearbox, a doubly fed induction generator rotor and by a two level converter.

Os tímpanos como instrumento solista no contexto da percussão de altura definida

Com este projecto pretende-se abordar uma vertente no estudo dos Tímpanos que, ao longo da sua história, tem sido marginal, relativamente à sua utilização "normal" de instrumento de orquestra - A utilização de Tímpanos como instrumento solista, especialmente na situação de solista não concertista. Para a persecução deste objectivo será traçada a trajectória evolutiva do instrumento ao longo da História da Música, tanto do ponto de vista das suas características de construção como da sua utilização pelos compositores ao longo do tempo. Não pode, por isso, deixar de ser feita uma abordagem da utilização dos Tímpanos em Orquestra, pois foi a utilização orquestral o "motor" da evolução do instrumento. Em complemento ao atrás enunciado, será igualmente desenvolvido o tema das preocupações de respeito pelo contexto histórico aplicado ao caso específico dos Tímpanos. Será igualmente feita uma tentativa de identificação de existência de exemplares antigos em Bandas de Música amadoras, através da realização de um inquérito. Por fim será traçado o quadro geral da utilização dos Tímpanos em Portugal nos dias de hoje. Atenção especial será dada a composições onde o objecto de estudo deste projecto está, mais directamente, em evidência. É este o caso de Marche (1685) dos irmãos Philidor, de um conjunto de Concertos e Sinfonias para múltiplos Tímpanos do final do século XVIII e das Eight Pieces for Four Timpani (1950/1966) de Elliott Carter. No caso da Marche será feita uma pequena análise e realizada uma edição moderna. No caso das peças para Tímpanos de Elliott Carter, será analisada com mais profundidade a peça Moto Perpetuo. Até ao final do século XVIII os Tímpanos foram, quase exclusivamente, os únicos instrumentos de Percussão usados na Música Erudita Ocidental. A partir do século XIX a secção da Percussão foi enriquecida com inúmeros novos elementos. Entre eles, novos instrumentos de Percussão de altura definida a que os Tímpanos pertencem. Será, tal como para os Tímpanos, traçado o seu trajecto de evolução e assim será completado o quadro actual da Percussão de altura definida. O Recital concretiza os principais pontos explorados no trabalho escrito, através da apresentação de um conjunto de obras apresentadas por ordem cronológica: -Marche de André e Jacques Philidor (1685) - Eight Pieces for Four Timpani de Elliott Carter (1950/1966) (March, Saeta, Moto Perpetuo, Recitative) - Concerto pour Percussion et Orquestre de André Jolivet (1958) (andamentos I, II e III) - OMAR Due pezzi per Vibrafono de Franco Donatoni (1985) ABSTRACT: Investigate the marginal use of the Timpani as a solo instrument is the main object of this study. ln order to achieve this main goal, we will point out the evolution of the instrument along Music History. We will focus both: the main characteristics of its construction and the way they have been used by composers. Bearing these facts in mind, we will also center our attention on the way that Timpani have been used at Orchestras, which had certainly leaded to the development of the instrument we are studying. At the same time, we will study historical respect and performance, by contextualizing the different historical periods of Timpani. It is also important to have information about the quantity of Timpani used at amateur musical bands in Portugal, mainly in what concerns ancient instruments. These elements will allow us to draw a general idea about the way Timpani are used in Portugal. ln order to have concrete examples of the Timpani as a solo instrument, we will analyze the following compositions: Marche de Timba/les (1685) by André and Jacques Philidor; The ensemble of Concerts and Symphonies for multiple Timpani from the end of the XVIIIth century; The Eight Pieces for Four Timpani (1950/1966) by Elliott Carter. Bearing in mind that other Defined Pitch Percussion Instruments have emerged at the beginning of the XIXth century, we will also study the evolution of those instruments. The Recital will materialize the main aspects we have focused at our written work and already mentioned above. The presentation will follow a chronological sequence as indicated: Marche de Timballes by André and Jacques Philidor (1685) Eight Pieces for Four Timpani by Elliott Carter (1950/1966) (March, Saeta, Moto Perpetuo, Recitative) - Concerto pour Percussion et Orquestre by André Jolivet (1958) (Movements I, II, III) Omar Due Pezzi per Vibrafono by Franco Donatoni (1985)