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

Numerical investigation of three types of space and time fractional Bloch-Torrey equations in 2D

Recently, the fractional Bloch-Torrey model has been used to study anomalous diffusion in the human brain. In this paper, we consider three types of space and time fractional Bloch-Torrey equations in two dimensions: Model-1 with the Riesz fractional derivative; Model-2 with the one-dimensional fractional Laplacian operator; and Model-3 with the two-dimensional fractional Laplacian operator. Firstly, we propose a spatially second-order accurate implicit numerical method for Model-1 whereby we discretize the Riesz fractional derivative using a fractional centered difference. We consider a finite domain where the time and space derivatives are replaced by the Caputo and the sequential Riesz fractional derivatives, respectively. Secondly, we utilize the matrix transfer technique for solving Model-2 and Model-3. Finally, some numerical results are given to show the behaviours of these three models especially on varying domain sizes with zero Dirichlet boundary conditions

Necrotizing pneumonia due to clonally diverse Staphylococcus aureus strains producing Panton-Valentine leukocidin: the Czech experience

SUMMARY A prospective study (2007)(2008)(2009)(2010)(2011)(2012)(2013) was undertaken to investigate clinical features and prognostic factors of necrotizing pneumonia caused by Staphylococcus aureus producing Panton-Valentine leukocidin (PVL) in the Czech Republic. Twelve cases of necrotizing pneumonia were detected in 12 patients (median age 25 years) without severe underlying disease. Eight cases occurred in December and January and the accumulation of cases in the winter months preceding the influenza season was statistically significant (P < 0·001). The course of pneumonia was very rapid, leading to early sepsis and/or septic shock in all but one patient. Seven patients died and mortality was fourfold higher in those patients presenting with primary pneumonia than with pneumonia complicating other staphylococcal/pyogenic infection elsewhere in the body. The S. aureus isolates displayed considerable genetic variability and were assigned to five lineages CC8 (n = 3), CC15 (n = 2), CC30 (n = 2), CC80 (n = 1), and CC121 (n = 3) and one was a singleton of ST154 (n = 1), all were reported to be associated with community-acquired infection. Four strains were methicillin resistant. The high case-fatality rate can only be reduced by improving the speed of diagnosis and a rapid test to detect S. aureus in the airways is needed