Optimal power flow for hybrid AC/DC grids

En aquest projecte es desenvolupa un model de Flux de Potència Òptim (OPF - Optimal Power Flow) aplicat a xarxes híbrides AC/DC. Per fer-ho, primerament s'haurà de modelitzar la xarxa, distingint el sistema AC, el sistema HVDC i les estacions convertidores que els interconnecten. A partir de la formulació extreta de la modelització, es podrà definir el model d'optimització OPF. Per tal de comprovar el correcte funcionament del model OPF desenvolupat, es portarà a terme l'anàlisi d'un sistema test conformat per una xarxa híbrida.En este proyecto se desarrolla un modelo de Flujo de Potencia Óptimo (OPF - Optimal Power Flow) aplicado a redes híbridas AC/DC. Para ello, primeramente deberá modelizarse la red, distinguiendo el sistema AC, el sistema HVDC y las estaciones convertidoras que los interconectan. A partir de la formulación extraída de la modelización, podrá definirse el modelo de optimización OPF. Para comprobar el correcto funcionamiento del modelo OPF desarrollado, se llevará a cabo el análisis de un sistema test conformado por una red híbrida.In this thesis, an OPF calculation model applied to AC/DC hybrid grids is presented, with the aim of developing an extension of MatPower that allows this type of calculation. With this tool, the OPF is studied for a test system defined by a hybrid grid. First, an introduction to HVDC transmission systems is given. After this, the modelling of hybrid AC/DC grids is developed, adding converters and HVDC lines to the model for AC. Then, the OPF mathematical model is defined, whose objective function, variables and constraints associated with the hybrid AC/DC model are presented. From here, the test system to be studied is introduced and results are shown from the developed MatPower extension. These results allow comparing different scenarios for the test system, each one having an HVDC system with different levels of meshing.Outgoin

Machine Learning Techniques for Electrical Validation Enhancement Processes

Post-Silicon system margin validation consumes a significant amount of time and resources. To overcome this, a reduced validation plan for derivative products has previously been used. However, a certain amount of validation is still needed to avoid escapes, which is prone to subjective bias by the validation engineer comparing a reduced set of derivative validation data against the base product data. Machine Learning techniques allow, to perform automatic decisions and predictions based on already available historical data. In this work, we present an efficient methodology implemented with Machine Learning to make an automatic risk assessment decision and eye margin estimation measurements for derivative products, considering a large set of parameters obtained from the base product. The proposed methodology yields a high performance on the risk assessment decision and the estimation by regression, which translates into a significant reduction in time, effort, and resources

MODEL ORDER REDUCTION OF NONLINEAR DYNAMIC SYSTEMS USING MULTIPLE PROJECTION BASES AND OPTIMIZED STATE-SPACE SAMPLING

Model order reduction (MOR) is a very powerful technique that is used to deal with the increasing complexity of dynamic systems. It is a mature and well understood field of study that has been applied to large linear dynamic systems with great success. However, the continued scaling of integrated micro-systems, the use of new technologies, and aggressive mixed-signal design has forced designers to consider nonlinear effects for more accurate model representations. This has created the need for a methodology to generate compact models from nonlinear systems of high dimensionality, since only such a solution will give an accurate description for current and future complex systems.The goal of this research is to develop a methodology for the model order reduction of large multidimensional nonlinear systems. To address a broad range of nonlinear systems, which makes the task of generalizing a reduction technique difficult, we use the concept of transforming the nonlinear representation into a composite structure of well defined basic functions from multiple projection bases.We build upon the concept of a training phase from the trajectory piecewise-linear (TPWL) methodology as a practical strategy to reduce the state exploration required for a large nonlinear system. We improve upon this methodology in two important ways: First, with a new strategy for the use of multiple projection bases in the reduction process and their coalescence into a unified base that better captures the behavior of the overall system; and second, with a novel strategy for the optimization of the state locations chosen during training. This optimization technique is based on using the Hessian of the system as an error bound metric.Finally, in order to treat the overall linear/nonlinear reduction task, we introduce a hierarchical approach using a block projection base. These three strategies together offer us a new perspective to the problem of model order reduction of nonlinear systems and the tracking or preservation of physical parameters in the final compact model

Virtual metrology for semiconductor manufacturing applications

Per essere competitive nel mercato, le industrie di semiconduttori devono poter raggiungere elevati standard di produzione a un prezzo ragionevole. Per motivi legati tanto ai costi quanto ai tempi di esecuzione, una strategia di controllo della qualità che preveda la misurazione completa del prodotto non è attuabile; i test sono eettuati su un ristretto campione dei dati originali. Il traguardo del presente lavoro di Tesi è lo studio e l'implementazione, attraverso metodologie di modellistica tipo non lineare, di un algoritmo di metrologia virtuale (Virtual Metrology) d'ausilio al controllo di processo nella produzione di semiconduttori. Infatti, la conoscenza di una stima delle misure non realmente eseguite (misure virtuali) può rappresentare un primo passo verso la costruzione di sistemi di controllo di processo e controllo della qualità sempre più ranati ed ecienti. Da un punto di vista operativo, l'obiettivo è fornire la più accurata stima possibile delle dimensioni critiche a monte della fase di etching, a partire dai dati disponibili (includendo misurazioni da fasi di litograa e deposizione e dati di processo - ove disponibili). Le tecniche statistiche allo stato dell'arte analizzate in questo lavoro comprendono: - multilayer feedforward networks; Confronto e validazione degli algoritmi presi in esame sono stati possibili grazie ai data-set forniti da un'industria manifatturiera di semiconduttori. In conclusione, questo lavoro di Tesi rappresenta un primo passo verso la creazione di un sistema di controllo di processo e controllo della qualità evoluto e essibile, che abbia il ne ultimo di migliorare la qualità della produzione.ope

Computer Science Research Institute 2005 annual report of activities.

This report summarizes the activities of the Computer Science Research Institute (CSRI) at Sandia National Laboratories during the period January 1, 2005 to December 31, 2005. During this period, the CSRI hosted 182 visitors representing 83 universities, companies and laboratories. Of these, 60 were summer students or faculty. The CSRI partially sponsored 2 workshops and also organized and was the primary host for 3 workshops. These 3 CSRI sponsored workshops had 105 participants, 78 from universities, companies and laboratories, and 27 from Sandia. Finally, the CSRI sponsored 12 long-term collaborative research projects and 3 Sabbaticals

Application of effective medium theory to the analysis of integrated circuit interconnects

The design and physical verification of contemporary integrated circuits is a challenging task due to their complexity. System-in-Package is an example of generally congested electronic components and interconnects which in the initial design process rely on computationally intensive electromagnetic simulations. Hence the available computer memory capacity and computational speed become meaningful limitations. An alternative method which allows the designer to overcome or reduce the limits is desired. This work represents the first demonstration of the application of effective medium theory to the analysis of those segments of the entire integrated system where the interconnect networks are more dense. The presented approach takes advantage of the deep subwavelength characteristic of interconnect structures. In order to achieve the aim of defining the homogeneous equivalent for the interconnect grating structure a few steps were followed towards proving the homogenisation concept and finally presenting it by an analytical formulation. A set of parameters (metal fill factor, aspect ratio, dielectric background and period-to-wavelength ratio) with values related to typical design rules were considered. Relating these parameters allows the empirical models to be defined. In order to show the relationship between existing effective medium theories and those developed in this Thesis, the presented empirical models are defined in terms of the Maxwell-Garnett mixing rule with an additional scaling factor. The distribution of the scaling factor was analysed in terms of the calculated reflection and transmission coefficients of the homogenised structures that are equivalent to a given grating geometry. Finally the scaling factor, for each empirical model, was expressed by an analytical formula and the models validated by their application to the numerical analysis of grating structures. The numerical validation was carried out by comparing the reflection and transmission coefficients obtained for the detailed and homogenised structures. In order to ensure the empirical models can be broadly employed, the performance of the model in the presence of non-normally incident plane wave was evaluated. For the range of angles ±30º the model is accurate to 5%. The impact of the shape of the grating, specifically the case of a tapered profile, typical of actual fabricated interconnects was also considered, with sidewall tapers of up to 5º giving the same error not higher than 5%. Experimental validation of the application of the homogenisation concept to the analysis of interconnects is desired for two main applications: for the reflectivity estimation of a whole chip in a System-in-Package and for the performance estimation of interconnects on lower metal layers in an interconnect stack. For the first, free-space measurements are taken of a grating plate with copper rods aligned in parallel illuminated by a plane wave in the X-band (8.2-12.4 GHz). For the second, S-parameters are measured for microstrip waveguides with a number of metal rods embedded in the substrate between the signal line and ground plane. The good agreement with the simulations validates the homogenisation approach for the analysis of interconnects

An investigation into adaptive power reduction techniques for neural hardware

In light of the growing applicability of Artificial Neural Network (ANN) in the signal processing field [1] and the present thrust of the semiconductor industry towards lowpower SOCs for mobile devices [2], the power consumption of ANN hardware has become a very important implementation issue. Adaptability is a powerful and useful feature of neural networks. All current approaches for low-power ANN hardware techniques are ‘non-adaptive’ with respect to the power consumption of the network (i.e. power-reduction is not an objective of the adaptation/learning process). In the research work presented in this thesis, investigations on possible adaptive power reduction techniques have been carried out, which attempt to exploit the adaptability of neural networks in order to reduce the power consumption. Three separate approaches for such adaptive power reduction are proposed: adaptation of size, adaptation of network weights and adaptation of calculation precision. Initial case studies exhibit promising results with significantpower reduction