Control of Variable Speed Wind Turbines with Doubly Fed Asynchronous Generators for Stand-Alone Applications

This paper addresses the design and implementation of a novel control of a variable speed wind turbine with doubly fed induction generator for stand-alone applications. In opposition to grid-tied applications, in stand-alone systems the voltage and frequency must be generated by the doubly fed induction generator. Therefore, a voltage and frequency controller is required for supplying the load at constant voltage and frequency. This controller is implemented by orientation of the generator stator flux vector along a synchronous reference axis. In this way, constant voltage and frequency is obtained and the generator will supply the active and reactive power demanded by the load, while the wind turbine will be responsible for achieving power balance in the system. Then, power control is assumed by the pitch actuator controlling the rotational speed of the wind turbine for power balancing. A load shedding mechanism is needed if the load power exceeds the maximum available wind power. Detailed simulation results are presented and discussed to demonstrate the capabilities and contributions of the proposed control scheme.This work has been supported by the I+D program for Research Groups of the Autonomous Community of Madrid under ref. S2013/ICE-2933.PublicadoPublicad

Modeling and Control of LCC Rectifiers for Offshore Wind Farms Connected by HVDC Links

This paper presents a voltage and frequency control (VFC) and an average-value model (AVM) of a line-commutated converter for a rectifier station in an offshore wind farm (OWF) connected by a high-voltage direct current link. A capacitor bank is placed at the AC terminals of the rectifier station to perform VFC within the OWF. The proposed model uses the active and reactive power generated by the OWF as inputs, while the state variables are the voltage magnitude and phase angle at the capacitor bank bus. The proposed VFC is based on the orientation of the voltage vector at the capacitor bank bus toward a synchronous reference axis. It is then demonstrated that frequency control is achieved by regulating the reactive power balance at the capacitor bank bus, while voltage control is carried out by regulating the active power balance. Moreover, it is demonstrated that in a diode rectifier, although voltage cannot be controlled as in a thyristor rectifier, it is bounded within acceptable limits. In addition, small-signal study is performed to facilitate controller design and system stability analysis. VFC and the accuracy of the proposed AVM are validated by simulation, using both the proposed AVM and a detailed switching model

Coordinated control system between grid-vsc and a dc microgrid with hybrid energy storage system

Direct current microgrids (DCMGs) are currently presented as an alternative solution for small systems that feed sensitive electrical loads into DC. According to the scientific literature, DCMG maintains good voltage regulation. However, when the system is in islanded mode, very pronounced voltage variations are presented, compromising the system"s ability to achieve reliable and stable energy management. Therefore, the authors propose a solution, connecting the electrical network through a grid-tied voltage source converter (GVSC) in order to reduce voltage variations. A coordinated control strategy between the DCMG and GVSC is proposed to regulate the DC voltage and find a stable power flow between the various active elements, which feed the load. The results show that the control strategy between the GVSC and DCMG, when tested under different disturbances, improves the performance of the system, making it more reliable and stable. Furthermore, the GVSC supports the AC voltage at the point of common coupling (PCC) without reducing the operating capacity of the DCMG and without exceeding even its most restrictive limit. All simulations were carried out in MATLAB 2020

El humor y el discurso humoristico en la novela "Dios se ha ido" de Javier García Sánchez

L'objectif de ce mémoire est d'analyser les différents éléments humoristiques présents dans le roman Dios se lia ido de Javier Garcia Sánchez. Cette œuvre allie la tristesse et l'humour dans des réflexions sur la vie, la solitude, le sexe et le jeu d'échecs dans la vie quotidienne d'un homme solitaire dans la quarantaine, qui devient l'univers exclusif du lecteur. On explore et critique l'évolution de la société espagnole contemporaine qui commence avec la transition démocratique à l'aide, entre autres, du grotesque, des jeux de mots, de la parodie et de l'ironie. On aborde également d'autres thèmes sociaux du point de vue d'un homme ordinaire avec ses préjugés et ses fausses interprétations. Dans ce roman, l'humour possède une fonction récréative mais il mène également à une réflexion sur les valeurs et la vie à une époque de scepticisme et de décadence

Enzymatic responses against anthracene are compromised in Yellow band-diseased tissues of the reef building species Orbicella faveolata

<p>Presented at the 37th scientific meeting of the association of marine laboratories of the Caribbean</p

Caribbean yellow band disease compromises the activity of catalase and glutathione S-transferase in the reef-building coral Orbicella faveolata exposed to anthracene

Fig. 1. Mean specific activity of catalase in healthy and Caribbean yellow band disease (CYBD)-affected corals exposed to 4 anthracene concentrations. ( * ) Differences between the conditions with p < 0.05 for pairwise comparisons. Error bars are SD.<div><br></div><div>Fig. 2. Mean specific activity of glutathione S-transferase in healthy and Caribbean yellow band disease (CYBD)- affected corals exposed to 4 anthracene concentrations. (*) Differences between the conditions with p < 0.05 for pair-wise comparisons. Error bars are SD</div><div><br></div><div>Fig. 3. Specific mean activity of glutathione peroxidase in healthy and Caribbean yellow band disease (CYBD)-affected corals exposed to 4 anthracene concentrations. Error bars are SD</div><div><br></div

Identification of strengths and weaknesses of cooperative efforts within the wider Caribbean using a network approach

Dataset associated to Ramírez-Ramírez RD, Montilla LM, Cavada-Blanco F and Croquer A. Identification of strengths and weaknesses of cooperative efforts within the wider Caribbean using a collaboration network approach [version 1; not peer reviewed]. F1000Research 2016, 5:799 (poster) (doi: 10.7490/f1000research.1111809.1