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Growing number of wind turbines is changing electricity generation profile all over the world. This brings challenges for power system operation, which was designed and developed around conventional power plants with directly coupled synchronous generators. In result, safety and stability of the electrical network with high wind energy penetration might be compromised. For this reason transmission...
This paper explores different strategies to set the reference current of a STATCOM under unbalanced grid voltage conditions. The aim of the proposed control strategies is to provide a set of reactive current references to be injected by the STATCOM under unbalanced grid faults. Their performance, as well as their grid support capability will be evaluated by means of simulations. Finally, the experimental...
This paper addresses the optimal controller problem for a linear system over linear observations with respect to different Bolza-Meyer criteria, where 1) the integral control and state energy terms are quadratic and the non-integral term is of the first degree or 2) the control energy term is quadratic and the state energy terms are of the first degree. The optimal solutions are obtained as sliding...
In wireless multihop networks, techniques such as multipath, local retransmissions and network coding have been successfully used to increase throughput and reduce losses. However, while these techniques improve forwarding performance for UDP, they often introduce side effects such as packet reordering and delay that heavily affect TCP traffic. In this paper we introduce CoMP, a network coding multipath...
In recent years there has been renewed interest in the problem of transferring bulk data (terabytes) utilizing commercial ISPs. The need to transfer bulk data arises in various scientific and industrial applications. Today, this data is moved using postal service in conjunction with hard drives and DVDs or special high performance dedicated networks. The key insight underlying the recent work was...
This paper describes a methodology based on combining TLS and close range photogrammetry aimed at generating the geometry of 3-D surfaces as well as 3D real textured models and map products for further study. Also, a spatial information system based on spherical photograph is presented that allows performing virtual tours as well as geo-referencing graphical or numerical data derived from the TLS...
The present invention further includes a method for substantially lattice matching single-crystal III-V semiconductor layers by including boron in the chemical structure of active cells layers in multi-junction solar. Solar photovoltaic devices, i.e., solar cells, are devices capable of converting solar radiation into usable electrical energy. The energy conversion occurs as the photovoltaic-effect...
The Internet is witnessing explosive growth in traffic due to bulk content transfers, such as multimedia and software downloads, and online sharing of personal, commercial, and scientific data. Yet bulk data transfers remain very expensive and inefficient. As a result, huge amounts of digital data continue to be delivered outside of the Internet using hard drives, optical media or tapes. Meanwhile,...
This paper presents a new methodology for Youla-Kučera parameter synthesis using invariant sets techniques. For a linear discrete-time system affected by perturbations and constraints and with the state derived by means of an observer, the proposed method gives the best Youla parameter in terms of finding the maximal invariant ellipsoid satisfying the constraints. As a result of this technique that...
Agile software projects have considerable freedom in shaping their emerging project management practices, and there are established ways to do that, e.g., with process retrospectives. The practices may change due to many reasons, such as (i) changes to critical system or process properties, (ii) process context, (iii) process capability maturity, etc. Maturity is not the only reason and a suitable...
In this paper, a robustified control technique is applied to a production-inventory system. A linear model is considered for the demand/inventory system with a variable dead-time and a variable yield. The inventory is firstly controlled with a MPC (model predictive control) law designed for some nominal values of the delay and yield. Using a Youla parameter-based procedure, this initial controller...
We propose a simple but flexible method for solving the generalized vector-valued TV (VTV) functional, which includes both the ??2-VTV and ??1-VTV regularizations as special cases, to address the problems of deconvolution and denoising of vector-valued (e.g. color) images with Gaussian or salt-and-pepper noise. This algorithm is the vectorial extension of the Iteratively Reweighted Norm (IRN) algorithm...
Current control based on hysteresis algorithms are widely used in different applications, such as motion control, active filtering or active/reactive power delivery control in distributed generation systems. The hysteresis current control provides to the system a fast and robust dynamic response, and requires a simple implementation in standard digital signal platforms. On the other hand, the main...
Partial shadowing of photovoltaic systems can over-proportionally reduce the energy yield and lead to early ageing and failure of the shadowed cells. Large area shadows are relatively easy to detect due to the eminent power reduction and decrease of fill factor. However, small area partial shadows in a larger system do not have a very obvious effect on the output power or fill factor of the PV array...
The classical control techniques for regulating the active and reactive power delivery in doubly fed induction generators (DFIG), for wind power applications, are normally based on voltage oriented control (VOC) strategies. Among these algorithms, those that work in a synchronous reference frame, attached to the magnetic flux vector, became very popular. In spite of the good behaviour of such algorithms...
A model predictive control strategy for a high-power, grid connected 3-level neutral clamped point converter is presented. Power losses constraints set a limit on commutation losses so reduced switching frequency is required, thus producing low frequency current harmonics. To reduce these harmonics an LCL filter is used. The proposed control strategy allows control of the active and reactive power...
High penetration of photovoltaic (PV) inverters in low voltage (LV) distribution network challenges the voltage stability due to interaction between multiple inverters and grid. As the main objective is to provide more power injection from VSC-based PV inverters, grid stability, reliability and power quality must be maintained or improved by adding cooperative control features to the grid-connected...
This paper examines how to apply simulated annealing to a map seeking circuit (MSC) when the circuit is formulated as a gradient ascent optimization problem. This modification is performed on a map seeking circuit solving the three dimensional model correspondence problem. It is shown that when the input image is partially occluded and covered by random edges, then the MSC can converge incorrectly...
This paper introduces a Combinatory Optimization Problem (COP) which captures the performance in cooperation of a P2P Streaming Network, considered at the buffer level. A new family of strategies of cooperation is defined, which represents the order of query of pieces in a communication between peers. We define a measure of quality for each strategy, based on the most shocking video streaming parameters,...
Large and distant offshore wind power plants can be efficiently connected to the onshore power grid network using VSC-HVDC (Voltage Source Converter based HVDC) transmission. Chopper controlled resistors can be used to limit the DC line over-voltage when there is a fault on the onshore AC grid and power transfer to the grid is obstructed. Considering the development of full scale converter based wind...
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