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The Arraiolos – Portugal – Moderate-Sized 2018 (M = 4.9) earthquake of January 15 and aftershocks: preliminary results

Publication . Borges, José; Caldeira, Bento; Fontiela, João; Custódio, Susana; Dias, Nuno; Waschilala, Piedade; Oliveira, Rui; Vales, Dina; Bezzeghoud, Mourad; Araújo, Alexandre; Carrilho, Fernando; Corela, Carlos; Rio, Inês; Vaz, José; Matias, Luís

On 15 January 2018 at 11:51 UTC, an earthquake of 4.9 ML occurred in the Northeast of Arraiolos region near Aldeia da Serra village. The hypocentral location, determined by Instituto Português do Mar e da Atmosfera (IPMA), has coordinates 38.79 N, 7.93 W at 11 km depth. The focal mechanisms determined by P-wave first motion polarities and waveforms inversion indicate a dominance of strike-slip events with nodal plans near NS (left lateral) and EW (right lateral) directions. Due to the lower magnitude, the earthquake didn’t cause damage but was widely felt in the Centre and South of Portugal mainland. In the vicinity of the epicentre, at the Aldeia da Serra village, it reached a maximum intensity VI, having been felt with intensity IV/V in the city of Évora, about 20 km from the epicentre. The event was also felt with intensity III in Lisbon at more than 100 km from the epicentre. This event caused alarm in the population that haven’t felt an earthquake for several decades. It also raised the media attention with many reports and interviews on TV and newspapers. The main ear thquake was immediatel y followed by a sequence of aftershocks of which the largest one, with ML=3.1, occurred the 1st February, fifteen days after the main shock and was largely felt by the population in the region of Arraiolos.

2018-09Conference object

Open access

Darrieus-type vertical axis rotary-wings with a new design approach grounded in double-multiple streamtube performance prediction model

Publication . Batista, Nelson; Melicio, Rui; Mendes, Victor

Exploitation of wind energy with vertical axis rotary-wing has advantage over horizontal axis rotary-wing in areas where the wind is turbulent and unstable, i.e., with fast changes either in direction or velocity as normal happens in urban areas. The Darrieus-type vertical axis rotary-wing is experiencing a growth in interest for development and installation due to a growing interest in decentralizing energy conversion. This growth is expected to be in further augment in what concerns the way of the future, i.e., the smart grid environment. A problem linked with this Darrieus-type rotary-wing is the complexity in the performance prediction study, since the blades move around the rotor in 360 degrees. An approach to the double-multiple streamtube performance prediction model for the vertical axis rotary-wing is offered in this paper, offering a flexible adapted tool when the airfoils lift and drag data are not available, or when more complex blade profiles of rotary-wings are in development. A new Darrieus-type vertical axis rotary-wing design is carried out with the approach offered, allowing for a self-start capable blade profile, having an adequate performance at high tip speed ratios. Several field tests are offered providing validation to the self-start, low noise and stable performance of the new rotary-wing design. Also, a modeling, control and simulation of grid integration are presented.

2018Journal article

Open access

Adaptive and predictive controllers applied to onshore wind energy conversion system

Publication . Viveiros, Carla; Melicio, Rui; Mendes, Victor; Igreja, José

This paper presents a simulation of onshore energy conversion system connected to the electric grid and under an event-based supervisor control based on deterministic version of a finite state machine. The onshore 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. First, mathematical models of a variable speed wind turbine with pitch control are studied, followed by the study of different controller types such as adaptive controllers and predictive controllers. The study of an event-based supervisor based on finite state machines is also studied. The control and supervision strategy proposed for the onshore energy conversion system is based on a hierarchical structure with two levels, execution level where the adaptive and predictive controllers are included, and the supervision level where the event-based supervisor is included. The objective is to control the electric output power around the reference power and also to analyze the operational states according to the wind speed. The studied mathematical models are integrated into computer simulations for the onshore energy conversion system and the obtained numerical results allow for the performance assessment of the system connected to the electric grid. A comparison of the onshore energy conversion system performance without or with the supervisor is carried out to access the influence of the control and supervision strategy on the performance.

2018Journal article

Open access

Decision making for sustainable aggregation of clean energy in day-ahead market: uncertainty and risk

Publication . Gomes, Isaías; Melicio, Rui; Mendes, Victor; Pousinho, H. M. I.

This paper addresses a strategy for decision-making of sustainable aggregation for clean energy participating in a day-ahead electricity market. The clean energy consists of wind turbines, photovoltaic arrays and energy storage, contributing to a better resilience of the system. The power delivered by a wind turbine or by a photovoltaic array is most certainly in deviation from the value associated with the bid accepted at a closing of a day-ahead electricity market. The deviation is due to the unpredicted variable nature of the respective sources of energy, leading to uncertainty and may imply a risk of loss of profit. So, uncertainty must be considered, and the addressed strategy considers uncertainty by scenarios of historical data and risk by the conditional value at risk. The strategy is a unified approach based on a risk-constrained and a two-stage stochastic optimization problem rewritten as a mixed-integer linear programming problem. A case study is presented to illustrate the main result and drive conclusions.

2019-04Journal article

Restricted access

Comparison of offshore and onshore wind systems with MPC five-level converter under 3Energy 4.0

Publication . Seixas, Mafalda; Melício, R; Mendes, Victor

This paper is about offshore/onshore wind systems under energy 4.0. A consideration is taken to account for the action of the floating motion given by the stiffness torque acting on the drive-train. The drive-train incorporates the dynamics of the floating platform and tower, resulting from the motion of the surface due to the marine wave perturbation. The performance of the multiple point clamped five-level converter is considered mainly from electrical power perspective. The simulation considers a blade pitch control fault causing an instantaneous cutoff on the capture of the wind energy to unveil the impact on the systems performance. Particularly, the fault influence on the behavior of the voltages in the capacitor banks is mitigated by selection of the suitable vectors. The multiple point clamped five-level converter with the conveniently proposed control strategy is able to recover normal operation after fault clearing.

2018-08-09Journal article

Restricted access