Full- & Reduced-Order State-Space Modeling of Wind Turbine Systems with Permanent-Magnet Synchronous Generator

Wind energy is an integral part of nowadays energy supply and one of the fastest growing sources of electricity in the world today. Accurate models for wind energy conversion systems (WECSs) are of key interest for the analysis and control design of present and future energy systems. Existing control-oriented WECSs models are subject to unstructured simplifications, which have not been discussed in literature so far. Thus, this technical note presents are thorough derivation of a physical state-space model for permanent magnet synchronous generator WECSs. The physical model considers all dynamic effects that significantly influence the system's power output, including the switching of the power electronics. Alternatively, the model is formulated in the $(a,b,c)$- and $(d,q)$-reference frame. Secondly, a complete control and operation management system for the wind regimes II and III and the transition between the regimes is presented. The control takes practical effects such as input saturation and integral windup into account. Thirdly, by a structured model reduction procedure, two state-space models of WECS with reduced complexity are derived: a non-switching model and a non-switching reduced-order model. The validity of the models is illustrated and compared through a numerical simulation study.Comment: 23 pages, 11 figure

Quantum spin models with electrons in Penning traps

We propose a scheme to engineer an effective spin Hamiltonian starting from a system of electrons confined in micro-Penning traps. By means of appropriate sequences of electromagnetic pulses, alternated to periods of free evolution, we control the shape and strength of the spin-spin interaction. Moreover, we can modify the effective magnetic field experienced by the particle spin. This procedure enables us to reproduce notable quantum spin systems, such as Ising and XY models. Thanks to its scalability, our scheme can be applied to a fairly large number of trapped particles within the reach of near future technology.Comment: 22 pages, 1 figure, added minor changes and typos, accepted for publication in PR

L'emigració de Barcelona 1988-1992: causes i característiques. El mercat de l'habitatge com a factor incentivador de l'emigració

Estudi realitzat per a l’Ajuntament de Barcelona entre 1988-1992.Estudi de les característiques socio-econòmiques, els motius de marxa i les àrees de destí més freqüents, dels emigrants barcelonins més recents (entre 1988-1992), evidenciar la incidència de l' habitatge en aquest canvi de residència i especialment la inadequació de l' oferta d' habitatge de Barcelona a un ampli segment de la demanda, en contraposició a l'oferta dels municipis de l'entorn que és més adequada a les necessitats dels emigrants. Aquests són entre d'altres, els objectius principals de l'estudi que aquí es presenta, realitzat en el marc del Centre de política del Sol i Valoracions de la universitat Politècnica de Catalunya per encàrrec de l’Àrea d'Economia i Empreses de l'Ajuntament de Barcelona.Preprin

Layer by layer generation of cluster states

Cluster states can be used to perform measurement-based quantum computation. The cluster state is a useful resource, because once it has been generated only local operations and measurements are needed to perform universal quantum computation. In this paper, we explore techniques for quickly and deterministically building a cluster state. In particular we consider generating cluster states on a qubus quantum computer, a computational architecture which uses a continuous variable ancilla to generate interactions between qubits. We explore several techniques for building the cluster, with the number of operations required depending on whether we allow the ability to destroy previously created controlled-phase links between qubits. In the case where we can not destroy these links, we show how to create an n x m cluster using just 3nm -2n -3m/2 + 3 operations. This gives more than a factor of 2 saving over a naive method. Further savings can be obtained if we include the ability to destroy links, in which case we only need (8nm-4n-4m-8)/3 operations. Unfortunately the latter scheme is more complicated so choosing the correct order to interact the qubits is considerably more difficult. A half way scheme, that keeps a modular generation but saves additional operations over never destroying links requires only 3nm-2n-2m+4 operations. The first scheme and the last scheme are the most practical for building a cluster state because they split up the generation into the repetition of simple sections.Comment: 16 pages, 11 figure

Using Quantum Computers for Quantum Simulation

Numerical simulation of quantum systems is crucial to further our understanding of natural phenomena. Many systems of key interest and importance, in areas such as superconducting materials and quantum chemistry, are thought to be described by models which we cannot solve with sufficient accuracy, neither analytically nor numerically with classical computers. Using a quantum computer to simulate such quantum systems has been viewed as a key application of quantum computation from the very beginning of the field in the 1980s. Moreover, useful results beyond the reach of classical computation are expected to be accessible with fewer than a hundred qubits, making quantum simulation potentially one of the earliest practical applications of quantum computers. In this paper we survey the theoretical and experimental development of quantum simulation using quantum computers, from the first ideas to the intense research efforts currently underway.Comment: 43 pages, 136 references, review article, v2 major revisions in response to referee comments, v3 significant revisions, identical to published version apart from format, ArXiv version has table of contents and references in alphabetical orde

Stretching short biopolymers by fields and forces

We study the mechanical properties of semiflexible polymers when the contour length of the polymer is comparable to its persistence length. We compute the exact average end-to-end distance and shape of the polymer for different boundary conditions, and show that boundary effects can lead to significant deviations from the well-known long-polymer results. We also consider the case of stretching a uniformly charged biopolymer by an electric field, for which we compute the average extension and the average shape, which is shown to be trumpetlike. Our results also apply to long biopolymers when thermal fluctuations have been smoothed out by a large applied field or force.Comment: 10 pages, 7 figure