Dissertations / Theses on the topic 'Outpost Inn'

The problem of output regulation deals with asymptotic tracking/rejection of a prescribed reference trajectory/disturbance. The main feature of the output regulation is that references/disturbances to be tracked/rejected belong to a family of trajectories generated as solutions of an autonomous system typically referred to as exosystem. Tackling this problem in context of error feedback leads to solutions that embeds a copy of the exosystem properly updated by means of error measurements. The output regulation problem for linear systems has been fully characterized and solved in the mid seven- ties by Davison, Francis and Wonham and then has been generalized to the non-linear context by Isidori and Byrnes. It is worth noting, however, that most of the frameworks considered so far for output regulation deal with systems and exosytems defined on Euclidean real state space and not much efforts have been done to extend the results of output regulation to systems and exosystems whose states live in more general manifolds. The tools available for solutions of the output regulation problem can’t be extented in a straightforward manner to non-linear systems whose states live in more general manifolds due to some restrictive structural assumption. The present thesis focuses on the problem of output regulation for left invariant systems defined on matrix Lie groups. In this framework we extend the idea of internal model-based control to systems defined on matrix Lie-groups taking advantages of the symmetry and invariant structures of the system considered. In particular we propose a general structure of the regulator for left invariant kinematic systems defined on general matrix Lie-group that solves the output regulation problem. Going further we study the output regulation problem for kinematics systems defined on the special orthogonal group and the special Euclidean group.

The present thesis focuses on the problem of robust output regulation for minimum phase nonlinear systems by means of identification techniques. Given a controlled plant and an exosystem (an autonomous system that generates eventual references or disturbances), the control goal is to design a proper regulator able to process the only measure available, i.e the error/output variable, in order to make it asymptotically vanishing. In this context, such a regulator can be designed following the well known “internal model principle” that states how it is possible to achieve the regulation objective by embedding a replica of the exosystem model in the controller structure. The main problem shows up when the exosystem model is affected by parametric or structural uncertainties, in this case, it is not possible to reproduce the exact behavior of the exogenous system in the regulator and then, it is not possible to achieve the control goal. In this work, the idea is to find a solution to the problem trying to develop a general framework in which coexist both a standard regulator and an estimator able to guarantee (when possible) the best estimate of all uncertainties present in the exosystem in order to give “robustness” to the overall control loop.

The present thesis focuses on the problem of robust output regulation for minimum phase nonlinear systems by means of identification techniques. Given a controlled plant and an exosystem (an autonomous system that generates eventual references or disturbances), the control goal is to design a proper regulator able to process the only measure available, i.e the error/output variable, in order to make it asymptotically vanishing. In this context, such a regulator can be designed following the well known “internal model principle” that states how it is possible to achieve the regulation objective by embedding a replica of the exosystem model in the controller structure. The main problem shows up when the exosystem model is affected by parametric or structural uncertainties, in this case, it is not possible to reproduce the exact behavior of the exogenous system in the regulator and then, it is not possible to achieve the control goal. In this work, the idea is to find a solution to the problem trying to develop a general framework in which coexist both a standard regulator and an estimator able to guarantee (when possible) the best estimate of all uncertainties present in the exosystem in order to give “robustness” to the overall control loop.

The objective of this thesis is twofold: on one hand, the design of nonliner observers, on the other, the design of internal-model regulators to solve the robust output regulation problem. In the observer theory a key role is played by the so called high-gain observers. The purpose of the first part of the thesis is to propose novel techniques which allow to overcome or at least to mitigate some of the main drawbacks characterizing this class of observers. Firstly, we study the possibility of writing an observer for multi-input multi-output observable systems in the original coordinates. Then, we propose a novel class of high-gain observers, denoted as ``low-power'', which allows to overcome numerical problems, to avoid the peaking phenomenon and to improve the sensitivity properties to high-frequency measurement noise. The second part of the thesis addresses the output regulation problem, solved for linear systems during the 70's by Francis and Wonham who coined the celebrated ``internal model principle''. Constructive solutions have also been proposed in the nonlinear framework but under restrictive assumptions that reduce the class of systems to which this methodology can be applied. In this thesis we focus on the output regulation problem in presence of periodic disturbances and we propose a novel approach which allows to consider a broader class of nonlinear systems. With the proposed design the stabilization problem and the regulation problem are substantially decoupled and output regulation is achieved in presence of uncertainties or disturbances, as long as the trajectories of the resulting closed-loop system are bounded.

The objective of this thesis is twofold: on one hand, the design of nonliner observers, on the other, the design of internal-model regulators to solve the robust output regulation problem. In the observer theory a key role is played by the so called high-gain observers. The purpose of the first part of the thesis is to propose novel techniques which allow to overcome or at least to mitigate some of the main drawbacks characterizing this class of observers. Firstly, we study the possibility of writing an observer for multi-input multi-output observable systems in the original coordinates. Then, we propose a novel class of high-gain observers, denoted as ``low-power'', which allows to overcome numerical problems, to avoid the peaking phenomenon and to improve the sensitivity properties to high-frequency measurement noise. The second part of the thesis addresses the output regulation problem, solved for linear systems during the 70's by Francis and Wonham who coined the celebrated ``internal model principle''. Constructive solutions have also been proposed in the nonlinear framework but under restrictive assumptions that reduce the class of systems to which this methodology can be applied. In this thesis we focus on the output regulation problem in presence of periodic disturbances and we propose a novel approach which allows to consider a broader class of nonlinear systems. With the proposed design the stabilization problem and the regulation problem are substantially decoupled and output regulation is achieved in presence of uncertainties or disturbances, as long as the trajectories of the resulting closed-loop system are bounded.

In recent years, radars have been used in many applications such as precision agriculture and advanced driver assistant systems. Optimal techniques for the estimation of the number of targets and of their coordinates require solving multidimensional optimization problems entailing huge computational efforts. This has motivated the development of sub-optimal estimation techniques able to achieve good accuracy at a manageable computational cost. Another technical issue in advanced driver assistant systems is the tracking of multiple targets. Even if various filtering techniques have been developed, new efficient and robust algorithms for target tracking can be devised exploiting a probabilistic approach, based on the use of the factor graph and the sum-product algorithm. The two contributions provided by this dissertation are the investigation of the filtering and smoothing problems from a factor graph perspective and the development of efficient algorithms for two and three-dimensional radar imaging. Concerning the first contribution, a new factor graph for filtering is derived and the sum-product rule is applied to this graphical model; this allows to interpret known algorithms and to develop new filtering techniques. Then, a general method, based on graphical modelling, is proposed to derive filtering algorithms that involve a network of interconnected Bayesian filters. Finally, the proposed graphical approach is exploited to devise a new smoothing algorithm. Numerical results for dynamic systems evidence that our algorithms can achieve a better complexity-accuracy tradeoff and tracking capability than other techniques in the literature. Regarding radar imaging, various algorithms are developed for frequency modulated continuous wave radars; these algorithms rely on novel and efficient methods for the detection and estimation of multiple superimposed tones in noise. The accuracy achieved in the presence of multiple closely spaced targets is assessed on the basis of both synthetically generated data and of the measurements acquired through two commercial multiple-input multiple-output radars.

This thesis work has been motivated by an internal benchmark dealing with the output regulation problem of a nonlinear non-minimum phase system in the case of full-state feedback. The system under consideration structurally suffers from finite escape time, and this condition makes the output regulation problem very hard even for very simple steady-state evolution or exosystem dynamics, such as a simple integrator. This situation leads to studying the approaches developed for controlling Non-minimum phase systems and how they affect feedback performances. Despite a lot of frequency domain results, only a few works have been proposed for describing the performance limitations in a state space system representation. In particular, in our opinion, the most relevant research thread exploits the so-called Inner-Outer Decomposition. Such decomposition allows splitting the Non-minimum phase system under consideration into a cascade of two subsystems: a minimum phase system (the outer) that contains all poles of the original system and an all-pass Non-minimum phase system (the inner) that contains all the unavoidable pathologies of the unstable zero dynamics. Such a cascade decomposition was inspiring to start working on functional observers for linear and nonlinear systems. In particular, the idea of a functional observer is to exploit only the measured signals from the system to asymptotically reconstruct a certain function of the system states, without necessarily reconstructing the whole state vector. The feature of asymptotically reconstructing a certain state functional plays an important role in the design of a feedback controller able to stabilize the Non-minimum phase system.

Output regulation refers to the class of control problems in which some outputs of the controlled system must be steered to some desired references, while maintaining closed-loop stability and in spite of the presence of unmeasured disturbances and model uncertainties. While for linear systems the problem has been elegantly solved in the 70s, output regulation for nonlinear systems is still a challenging research field, and 30 years of active research left open many fundamental problems. In particular, all the regulators proposed so far are limited to very specific classes of nonlinear systems and, even in those cases, they fail in extending in their full generality the celebrated properties of the linear regulator. The aim of this thesis is to make a decisive step towards the systematic extension of the output regulation theory to embrace more general multivariable problems. To this end, we touch here three fundamental pillars of regulation theory: the structure of regulators, the robustness issue, and the adaptation of the control system. Regarding the structural aspects, we pursue here a design paradigm that is complementary to canonical nonlinear regulators and that trades a conceptually more suitable structure with a strong internal intertwining between the different parts of the regulator. For what concerns robustness, we introduce a new framework to characterize robustness of regulators relative to steady-state properties more general than the usual requirement asking a zero asymptotic error. We characterize in this unifying terms a large part of the existing approaches, and we end conjecturing that general nonlinear regulation admits no robust solution. Regarding the evolution of regulators, we propose an adaptive regulation framework in which adaptation is used online to tune the internal models embedded in the control system. Adaptation is cast as a general system identification problem, allowing for different well-known algorithms to be used.

The present thesis is composed of a short introduction aimed at introducing the topic and reviewing the literature and then three empirical articles. In the first paper the eco-efficiency levels of a group of Italian firms operating in 5 industrial sectors are computed using the directional distance function (DDF) framework. Results are analysed in a second stage where the determinants of environmental performances and the regulatory impact are investigated applying a robust econometric technique. Estimates underline that the sector-specific effect on eco-efficiency and on regulatory opportunity costs will disappear when individual characteristics of firms are considered, finally a major difficulty in dealing with environmental constraints emerges for small and medium firms. The second application deals with the scientific production of CNR’s research institutes: they produce a portfolio of products characterised by different scientific profile. The hypothesis is that there are 2 category of scientific outputs: researchers and institutes try to maximize only one of them, but the other cannot be reduced or eliminated. Obtained DDF estimates allow to verify different hypothesis: from the consistency and novelty of results in respect to the standard approach, to the TFP growth trends and concluding with quantification, in term of unpublished scientific papers, of the fund cutting occurred after the 2003 reform. Finally is proposed an efficiency analysis of the chemical industry in Italy and Germany, a mature sector where testing for the validity of Porter’s hypothesis could be particularly interested. Estimations reveal an higher eco-efficiency level for Italian firms also if they are more pollutant in absolute term. TFP growth, that takes into account reduction in emission levels, reveal a more favourable trend for German firms which at the end of period reach an eco-efficiency level similar to their counterparts. Finally the formal test for the Porter’s hypothesis lead to a rejection, revealing the absence of a positive relationship between initial regulatory costs and observed TFP growth rates.

Analysis of the peak-to-peak output current ripple amplitude for multiphase and multilevel inverters is presented in this PhD thesis. The current ripple is calculated on the basis of the alternating voltage component, and peak-to-peak value is defined by the current slopes and application times of the voltage levels in a switching period. Detailed analytical expressions of peak-to-peak current ripple distribution over a fundamental period are given as function of the modulation index. For all the cases, reference is made to centered and symmetrical switching patterns, generated either by carrier-based or space vector PWM. Starting from the definition and the analysis of the output current ripple in three-phase two-level inverters, the theoretical developments have been extended to the case of multiphase inverters, with emphasis on the five- and seven-phase inverters. The instantaneous current ripple is introduced for a generic balanced multiphase loads consisting of series RL impedance and ac back emf (RLE). Simplified and effective expressions to account for the maximum of the output current ripple have been defined. The peak-to-peak current ripple diagrams are presented and discussed. The analysis of the output current ripple has been extended also to multilevel inverters, specifically three-phase three-level inverters. Also in this case, the current ripple analysis is carried out for a balanced three-phase system consisting of series RL impedance and ac back emf (RLE), representing both motor loads and grid-connected applications. The peak-to-peak current ripple diagrams are presented and discussed. In addition, simulation and experimental results are carried out to prove the validity of the analytical developments in all the cases. The cases with different phase numbers and with different number of levels are compared among them, and some useful conclusions have been pointed out. Furthermore, some application examples are given.

Analysis of the peak-to-peak output current ripple amplitude for multiphase and multilevel inverters is presented in this PhD thesis. The current ripple is calculated on the basis of the alternating voltage component, and peak-to-peak value is defined by the current slopes and application times of the voltage levels in a switching period. Detailed analytical expressions of peak-to-peak current ripple distribution over a fundamental period are given as function of the modulation index. For all the cases, reference is made to centered and symmetrical switching patterns, generated either by carrier-based or space vector PWM. Starting from the definition and the analysis of the output current ripple in three-phase two-level inverters, the theoretical developments have been extended to the case of multiphase inverters, with emphasis on the five- and seven-phase inverters. The instantaneous current ripple is introduced for a generic balanced multiphase loads consisting of series RL impedance and ac back emf (RLE). Simplified and effective expressions to account for the maximum of the output current ripple have been defined. The peak-to-peak current ripple diagrams are presented and discussed. The analysis of the output current ripple has been extended also to multilevel inverters, specifically three-phase three-level inverters. Also in this case, the current ripple analysis is carried out for a balanced three-phase system consisting of series RL impedance and ac back emf (RLE), representing both motor loads and grid-connected applications. The peak-to-peak current ripple diagrams are presented and discussed. In addition, simulation and experimental results are carried out to prove the validity of the analytical developments in all the cases. The cases with different phase numbers and with different number of levels are compared among them, and some useful conclusions have been pointed out. Furthermore, some application examples are given.

The research activity object of the present dissertation has been carried out at the Industrial Engeneering Doctoral School (Course of Electric Engeneering) of the University of Padova. The study concerned the electromagnetic systems modelling with regard on active control system analysis for the stabilization of plasma MHD modes in the RFX-mod experiment. Three are the main results of the research activity. The first one is the inclusion of the specific problem in the frame of the Unified Signal Theory, important in order to build a solid theoretical background from which starting developing new control models and techniques. The second one is the production of a mathematical model of the plant based exclusively on experimental measures. This allow the system's structure analysis, the simulation of its dynamic behaviour and the development of innovative control schemes. The third one is the actual production of a new algorithm based on the developed model. The system cosidered in the present study is made up by 192 units, each one including an active coil, its power amplifier, three field sensors (respectively radial, toroidal and poloidal). The active coils and the radial sensors are laid down in a regular manner and in this way they cover exactly the toroidal surfaces they intersects. Both of them form a grid made of 48 poloidal arrays, each one consisting of 4 elements. Metallic structures of different thickness are present in between the active coils and the magnetic field sensors, which are interested by dissipative effects due to the induced currents by the active control system and by the plasma. During a first phase of the research, experimental campaigns have been made in order to measure quantitatively the mutual couplings between saddle coils and the effect of their currents on the magnetic field measured by the radial sensors. Data collected during these campaigns allowed for the mathematical form of the active coils inductance matrix and the mutual inductance between active coils and sensors to be discovered. Due to the presence of the passive structures these matrices are not constant, but variable in the frequency domain. For this reason the campaigns have been carried out studying the behaviour of the couplings at different frequencies. A model of the couplings has then been derived and used in the construction of a bigger model comprehensive of the active coils and power amplifier dynamics. The task has been completed by writing convenient procedures in the Matlabr language, which allowed for an automated processing of the experimental data under some simplifying hypothesis about the number of significative couplings. Later the model has been intensively validated. Tests have been carried out both in open loop and closed loop. The open loop tests have been made by comparing the real and simulated outputs corresponding to the applied voltages and currents. The model was able to reproduce the output quantities with a 5% accuracy, to mimic the real closed loop stability range and has been used with success as a tool to gain insight into marginally stable phenomena. The model analysis evidenced a couple of important facts. The first is that the coupling between active coil and sensor is not so local as expected; this required a great number of couplings to be considered. The second is that the uniformity of the couplings is less than expected. The presence of features, like the inner equatorial gap, ruining the uniformity of the passive structures acts as a limit of the obtainable performance in the present configuration. On the basis of the model a new control algorithm has been designed using the singular value decomposition. Simulation results confirm that this control algorithm is able to compensate the effects of the local features of the passive structures till a limit frequency. Above that frequency the power required for the compensation would exceed the capacity of the amplifiers. Part of the research activity has been carried out in the frame of a collaboration between the Consorzio RFX and the EFDA-JET laboratory of Culham (UK) about the upgrade of the power amplifier of the plasma vertical instability. Here the research has focused on the realisation of part of the software control system of the new resonant amplifier.

This thesis addresses the problem of robustness in control in two main topics: linear output regulation when no knowledge is assumed of the modes of the exosystem, and hybrid gradient-free optimization. A framework is presented for the solution of the first problem, in which asymptotic regulation is achieved in case of a persistence of excitation condition. The stability properties of the closed-loop system are proved under a small-gain argument with no minimum phase assumption. The second part of the thesis addresses, and proposes, a solution to the gradientfree optimization problem, solved by a discrete-time direct search algorithm. The algorithm is shown to convergence to the set of minima of a particular class of non convex functions. It is, then, applied considering it coupled with a continuous-time dynamical system. A hybrid controller is developed in order to guarantee convergence to the set of minima and stability of the interconnection of the two systems. Almost global asymptotic is proven for the proposed hybrid controller. Shown to not be robust to any bounded measurement noise, a robust solution is also proposed. The aim of this thesis is to lay the ground for a solution of the output regulation problem in case the error is unknown, but a proxy optimization function is available. A controller embedding the characteristics of the two proposed approaches, as a main solution to the aforementioned problem, will be the focus of future studies.

In this thesis simple closed-form asymptotic solutions for estimating the output power quality in single-phase cascaded H-bridge multilevel inverters are presented for staircase modulation technique and pulse-width modulation (PWM) technique. The analysis is carried out in the time domain considering the whole harmonic content and being used for an arbitrary inverter level count. In case of the staircase modulation technique, the voltage and current ripple normalized means square (NMS) expressions are obtained in time domain considering the fundamental period. Voltage and current total harmonic distortions (THDs) as a function of the corresponding NMS values are defined as constrained optimization ones. Optimizing the voltage and current THDs determines the voltage and current optimal switching angles over the modulation index range. The current THD is understood as voltage frequency weighted THD that assumes a pure inductive load, but it is practically accurate for inductively dominant RL-loads. The same approach for estimating the current quality is given for a grid-connected inverter. In the case of the PWM technique, the voltage and current THDs are estimated supposing that the ratio between switching and fundamental frequencies is (infinitely) large (asymptotic assumption). The voltage and current ripple normalized mean square (NMS) values are obtained in time domain by double integration of their normalized squared ripples over the switching and fundamental periods. They present piecewise continuously differentiable analytical solutions with only elementary functions and can be understood as the time-domain equivalent of the frequency-domain double Fourier transformation. The direct relation between the voltage and current NMS values and their qualities is presented. Considering the same approach, the current THD evaluation in case of a grid-connected system is presented. Besides analytical developments, simulation and experimental verifications for three-level (one H-bridge), five-level (two cascaded H-bridges) and seven-level (three cascaded H-bridges) single-phase inverters are analysed, presented and compared in details.

AN ABSTRACT OF THE THESIS OF PRASHANTHI BANALA, for the Master of Science degree in ELECTRICAL AND COMPUTER ENGINEERING, presented on 31 October 2011, at Southern Illinois University Carbondale. TITLE: OUTPUT FEEDBACK H-inf CONTROL DESIGN FOR MULTI-AGENT SYSTEMS MAJOR PROFESSOR: Dr. Farzad Pourboghrat In this thesis, the design of distributed control for identical multi-agent systems is considered based on the optimization of H-inf cost function. Identical dynamically coupled but interacting systems (agents) are considered where control action of each agent is based on relative output measurement of their neighboring agents and a subset of their own output. The agents communicate with each other to achieve a common goal. A distributed dynamic output feedback control strategy that satisfies H-inf performance for multi-agent systems is developed and corresponding H-inf performance region is analyzed. An example illustrates the necessary and sufficient condition for dynamic output feedback controller synthesis to obtain desired H-inf performance.

One of the biggest challenge in modern communication systems is to provide a single antenna for different applications. Existing antenna systems are limited to some applications. So it is important to design a single reconfigurable antenna for multiple applications. Five different reconfigurable printed antennas for different applications are designed during the study of this thesis. In the first design an antenna for frequency reconfigurable applications is designed. The electrical length of the conductor is changed using PIN diodes and the resonance of antenna is shifted from 4.27 GHz to 3.56 GHz. Good agreement between simulated and measured results is observed. In the second and third designs, Ultra wideband (UWB) Multiple-Input Multiple-Output (MIMO) antennas with on-demand Wireless Local Area Network (WLAN) rejection are designed. The second design consists of two elements UWB-MIMO antenna and stubs are connected to the ground plane using PIN diodes. These stubs act as a stop-band filter and reject the band at 5.5 GHz center frequency. This design has a compact size of 23 x 39.8 mm2. The third design has almost same features as of second design but it has four elements. These elements are placed orthogonally to each other. The total size of this proposed design is 50 x 39.8 mm2. The ground plane is common and a band-stop design is placed between the ground planes. This band-stop design is connected with the ground plane using PIN diodes. When diodes are biased, the current is travelled to the nearly placed band-stop design and a notch is obtained around 5.5 GHz. In fourth design a reconfigurable array with a sensing circuit is designed. The array consists of four individual reconfigurable patches which are attached to the different conformal surfaces. These patches are reconfigured from 3.15 GHz to 2.43 GHz using PIN diodes. The correct phase at each element is provided using phase shifters. The sensing circuit is designed in such a way that only input voltage is changed to provide the correct phase on the switching frequency. The patterns of the array are recovered on both switching frequencies when array is attached to wedge or cylindrical surface. In the last design a series-fed array is designed. Composite Right/Left Handed Transmission Line (CRLH-TLs) are used instead of traditional meanderline microstrip lines to connect the array elements. These CRLH-TLs provided the zero phase at each connecting element, which resulted in broad side radiation patterns. To reconfigure the antenna to another frequency a small patch and second CRLH-TL is connected between array elements
Una delle sfide più grandi nei moderni sistemi di telecomunicazioni è realizzare una singola antenna idonea all’impiego in differenti ambiti. I sistemi di antenna esistenti infatti sono limitati solo a poche funzionalità. Risulta quindi importante progettare una singola antenna, riconfigurabile per una molteplicità di utilizzi. In questo lavoro di tesi vengono presentate cinque diverse antenne stampate e riconfigurabili. Per primo verrà presentata il design di una antenna riconfigurabile in frequenza; la lunghezza elettrica del radiatore viene cambiata usando dei diodi PIN spostando la frequenza di risonanza da 4.27 GHz a 3.56 GHz. Viene rilevato un buon accordo tra risultati sperimentali e quelli simulati. Nel secondo e nel terzo design vengono implementate antenne UWB-MIMO con capacità di rigettare a comando la banda di funzionamento WLAN. Nel dettaglio, il secondo design d’antenna consiste di due radiatori UWB-MIMO impiegati assieme a degli stub che sono connessi al piano di massa tramite diodi PIN. Gli stubs si comportano come filtri elimina-banda che inibiscono la radiazione intorno ai 5.5 GHz. Il design realizzato risulta molto compatto misurando solo 23x39.8 mm2. Il terzo design di antenna ha quasi le stesse caratteristiche del precedente ma è formato da quattro elementi: questi sono posizionati ortogonalmente l’uno all’altro. L’ingombro complessivo risulta di 50x39.8 mm2. Il piano di massa è condiviso ed una struttura elimina-banda è posta tra i radiatori. Tale struttura è connessa con il piano di massa tramite dei diodi PIN. Quando i diodi sono polarizzati la corrente la attraversa portando alla formazione di un notch nell’intorno dei 5.5GHz. Nel quarto design viene presentata una schiera di antenne riconfigurabile comandata da un sensore. La schiera è formata da quattro antenne patch riconfigurabili che sono posizionate su diverse superfici conformi. Le antenne patch sono rese riconfigurabili con l’uso di diodi PIN per operare a 3.15 Ghz o 2.43 GHz. La fase di cui necessita ciascun radiatore per compensare la deformazione della superficie viene fornita da dei variatori di fase. Tali variatori di fase sono realizzati in modo tale che necessitano solo di una tensione di pilotaggio in ingresso; il diagramma di radiazione della schiera viene ricomposto ad entrambe le frequenze di funzionamento quando la superficie inizialmente piana viene piegata ad angolo o circolarmente. Nell’ultimo design viene presentata una schiera di antenne alimentate in serie tramite linee CRLH che vengono impiegate al posto di linee a microstriscia tradizionali. Questo permette di fornire uno shift di fase nullo a ciascun elemento radiante della schiera in modo da ottenere una modo di radiazione trasversale. Per riconfigurare la schiera ad operare ad una frequenza diversa una piccola patch ed una seconda linea di trasmissione CRLH viene connessa tra gli elementi radianti

This PhD work has been carried out at the Legnaro National Laboratories (LNL), one of the four national labs of the National Institute for Nuclear Physics (INFN). The mission of LNL is to perform research in the field of nuclear physics and nuclear astrophysics together with emerging technologies. Technological research and innovation are the key to promote excellence in science, to excite competitive industries and to establish a better society. The research activities concerning electronics and computer science are an essential base to develop the control system of the Selective Production of Exotic Species (SPES) project. Nowadays, SPES is the most important project commissioned at LNL and represents the future of the Lab. It is a second generation Isotope Separation On-Line (ISOL) radioactive ion beam facility intended for fundamental nuclear physics research as well as experimental applications in different fields of science, such as nuclear medicine; radio-pharmaceutical production for therapy and diagnostic. The design of the SPES control system demands innovative technologies to embed the control of several appliances with different requirements and performing different tasks spanning from data sharing and visualization, data acquisition and storage, networking, security and surveillance operations, beam transport and diagnostic. The real time applications and fast peripherals control commonly found in the distributed control network of particle accelerators are accompanied by the challenge of developing custom embedded systems. In this context, the proposed PhD work describes the design and development of a multi-purpose Input Output Controller (IOC) board capable of embedding the control of typical accelerator instrumentation involved in the automatic beam transport system foreseen for the SPES project. The idea behind this work is to extend the control reach to the single device level without losing in modularity and standardization. The outcome of the research work is a general purpose embedded computer that will be the base for standardizing the hardware layer of the frontend computers in the SPES distributed control system. The IOC board is a Computer-on-Module (COM) carrier board designed to host any COM Express type 6 module and is equipped with a Field Programmable Gate Array (FPGA) and user application specific I/O connection solutions not found in a desktop pc. All the generic pc functionalities are readily available in off-the-shelf modules and the result is a custom motherboard that bridges the gap between custom developments and commercial personal computers. The end user can deal with a general-purpose pc with a high level of hardware abstraction besides being able to exploit the on-board FPGA potentialities in terms of fast peripherals control and real time digital data processing. This document opens with an introductory chapter about the SPES project and its control system architecture and technology before to describe the IOC board design, prototyping, and characterization. The thesis ends describing the installation in the field of the IOC board which is the core of the new diagnostics data readout and signal processing system. The results of the tests performed under real beam conditions prove that the new hardware extends the current sensitivity to the pA range, addressing the SPES requirements, and prove that the IOC board is a reliable solution to standardize the control of several appliances in the SPES accelerators complex where it will be embedded into physical equipment, or in their proximity, and will control and monitor their operation replacing the legacy VME technology. The installation in the field of the IOC board represents a great personal reward and crowns these years of busy time during which I turned what was just an idea in 2014, into a working embedded computer today.
Questo lavoro di dottorato è stato svolto presso ai Laboratori Nazionali di Legnaro (LNL), uno dei quattro laboratori nazionali dell’Istituto Nazionale di Fisica Nucleare. La missione principale dei LNL è la ricerca di base nella fisica e astrofisica nucleare, sostenuta da un’importante ricerca relativa alle tecnologie emergenti. Le attività di ricerca nell’ambito dell’elettronica e dell’informatica sono essenziali per lo sviluppo del sistema di controllo del progetto SPES (produzione selettiva di specie esotiche). SPES è il progetto piú importante e rappresenta il futuro dei laboratori di Legnaro. Si tratta di una infrastruttura di tipo ISOL (separazione di isotopi in linea), di seconda generazione, il cui obiettivo è quello di generare e accelerare un fascio di ioni radioattivi dedicato alla ricerca nel campo della fisica nucleare, astrofisica nucleare, e ad applicazioni sperimentali in diversi campi della scienza come la produzione di particolari radionuclidi per la medicina nucleare che saranno utili per la diagnosi e la cura di patologie oncologiche. Il progetto del sistema di controllo di SPES sarà basato su tecnologie innovative che consentiranno di monitorare e controllare dispositivi tra loro molto diversi e che eseguono funzioni differenti che vanno dall’acquisizione e visualizzazione dei dati, condivisione dei dati in rete, memorizzazione delle informazioni, operazioni di sorveglianza, diagnostiche e trasporto del fascio. In questo contesto, il dottorato di ricerca proposto descrive il progetto e la realizzazione di una scheda elettronica di controllo (IOC) multifunzione capace di controllare quasi tutte le apparecchiature coinvolte nel trasporto del fascio di ioni radioattivi. L’idea di base di questo lavoro è quella di estendere il controllo a livello di singola apparecchiatura o piccoli gruppi di dispositivi senza rinunciare alla modularità e alla standardizzazione dell’elettronica. Il risultato del lavoro di dottorato è un computer embedded multifunzione progettato con tecnologie all’avanguardia che diventerà lo standard, a livello hardware, su cui si baserà il sistema di controllo distribuito di SPES. Questo controllore multifunzione integra tutte le funzionalità di un computer commerciale e in aggiunta è equipaggiato con un dispositivo programmabile sul campo (FPGA) e alcune periferiche non standard dedicate ad applicazioni di controllo specifiche. L’utente finale potrà sfruttare questa scheda elettronica come un qualunque pc commerciale, oppure, potrà sfruttare le potenzialità della FPGA per le elaborazioni digitali dei dati in tempo reale, per il trasferimento dei dati ad alta velocità su fibra ottica, per chiudere anelli di controllo a larga banda e per avere tempi di risposta agli stimoli in ingresso dal campo deterministici e molto brevi. Il documento apre con una introduzione sul progetto SPES prima di descrivere la progettazione, prototipizzazione e validazione della scheda IOC dando particolare risalto alle attività in cui il mio contributo è stato fondamentale. La tesi si chiude descrivendo l’integrazione della scheda IOC nel sistema di diagnostiche di fascio di SPES. Le misure del profilo di fascio eseguite sul campo e l’estensione della sensibilità di corrente a pochi pA confermano che la scheda elettronica progettata è una soluzione affidabile per standardizzare, a livello hardware, il controllo di diverse apparecchiature nel complesso degli acceleratori del progetto SPES. Questa scheda sostituirà la tecnologia VME in diverse applicazioni e sarà la base su cui implementare un sistema di trasporto di fascio automatico e di qualità, fondamentale per il successo delle attività di ricerca ai LNL. L’installazione in campo della scheda elettronica rappresenta una soddisfazione personale enorme e corona questi anni di duro lavoro durante ai quali ho trasformato quella che nel 2014 era solo un’idea, in un computer embedded pienamente funzionante.

The main topic of this thesis is the study of the interaction of agents interconnected in a large-scale network. In the thesis, three complementary problems have been afforded: Analysis of Consensus Networks, Synthesis of Higher Order Consensus Networks, and Application of Synchronization algorithms
Questa tesi di dottorato e incentrata sullo studio dell'interazione di agenti interconnessi in rete. In questa tesi vengono affrontati tre problemi complementari l'un l'altro: Analisi di reti di consenso, Sintesi di reti di consenso di ordine superiore, e Applicazione di algoritmi di sincronizzazione

Scopo di questa tesi è sviluppare un nuovo approccio al problema dell’ inseguimento quasi perfetto di una traiettoria desiderata. Il nuovo metodo può essere annoverato nel contesto dell’inversione stabile del modello e supera le principali limitazioni teoriche pratiche che pesantemente penalizzano i metodi classici. L’uscita desiderata da inseguire e la corrispondente traiettoria d’ingresso sono partizionate nelle componenti transitorie e di regime. Una volta che la traiettoria d’uscita desiderata è stata specificata, il corrispondente ingresso transitorio è calcolato con un procedimento di "pseudoinversione". Esso consiste nella approssimazione ai minimi quadrati della soluzione dell’equazione integrale di Fredholm che corrisponde alla forma esplicita della risposta forzata in uscita. L’ingresso di regime permanente è calcolato analiticamente utilizzando la risposta a regime permanente. I principali vantaggi della tecnica di pseudoinversione sono: la sua generalità non richiede procedure "ad hoc" dipendenti da particolari condizioni del processo da controllare, non è necessaria alcuna preattuazione, può essere applicata a sistemi non iperbolici, il progettista è svincolato dal difficile compito di scegliere a priori una traiettoria d’uscita transitoria desiderata realmente appropriata, il metodo può essere applicato sia a processi a tempo continuo che a tempo discreto con piccole modifiche, può essere applicato anche nei casi d’incertezza sulle condizioni iniziali e sui parametri e nel caso di sistemi stocastici.
The purpose of this thesis is to propose a new general method to obtain a uniformly bounded feedforward input driving a linear system with the purpose of attaining an almost exact output tracking. The new approach can be counted into the model stable inversion framework and it overcomes some theoretical and practical limitations which heavily affect the classical methods. The basic idea consists in partitioning the desired output and the corresponding input trajectories into the transient and steady state components. The transient part of the input is assumed to be given by a piece-wise polynomial function. Once the desired output trajectory has been specified it is possible to compute the unknown transient input as the approximate least-squares solution of the Fredholm’s integral equation corresponding to the explicit formula of the output forced response. The steady state input is analytically computed exploiting classical results on steady-state response. The main advantages of the resulting pseudo inversion technique are: its generality does not require "ad hoc" procedures depending on the particular plant to be controlled, no preactuation is needed, both non hyperbolic and near non hyperbolic systems can be dealt with, the designer can be released from the difficult task of "a priori" choosing a really appropriate, desired, transient output trajectory, the method can be applied both to continuous and discrete-time plants with minor modifications, arbitrary (possibly uncertain) initial conditions, uncertain parameters and stochastic systems can be also considered.

Space mission design is a complex discipline. Several research studies are currently investigating how to ameliorate the process. Since the decision taken during the early phases of the project are those which affect the most the final solution of a system in terms of architecture, configuration, and cost, more efforts are sunk in these stages for not jeopardizing the entire product life-cycle stages. As the stakeholders and the other actors involved in the design process should face low levels of knowledge associated to the system in the conceptual stages, the decision-making process is intrinsically affected by uncertain results. Each choice made in this risky scenario affects the next design iterations, therefore a suitable design approach is needed. Several methodologies have been proposed by both academia and industry in the field of System Engineering (SE). The current trend is to adopt a Model Based System Engineering (MBSE) approach coupled with Concurrent Engineering (CE) paradigms. The model-based methodology overcomes the weaknesses of a document-based one, aggregating all the relevant information and engineering data into a system model, which evolves as the real system throughout all the product life-cycle phases. The systematic CE approach is able to involve several experts in a multidisciplinary working context, where data, ideas, and solutions are shared at the same time using a common platform. Both the approaches help to shorten time and cost of the overall design process and prevent possible mistakes which could worsen the final solution if not identified earlier enough, thus maximizing the efficiency of each design session. However, negotiations still result to be as one of the most complicated and frustrating part of the whole design process. Moreover, the recent space exploration scenarios proposed by national agencies are characterized by multiple actors of different extractions, but commonly participating into shaping future goals. The broader is the international cooperation framework, the more complex will be to design a space mission, especially considering the negotiation goals to be handled by the different experts involved. The present Ph.D. thesis is aiming to cast some lights on the integration of Virtual Reality (VR) within the standard design tools to assist the space mission design process. The creation of a virtual model for simulating different features of a system allows to analyse aspects which may be overlooked, especially in the early design phases, such as ergonomics, operations, and training. The intuitive interaction with human senses and the immersion into a 3D Virtual Environment (VE) guarantee fundamental improvements and evaluation of different solutions that are updated in real-time, benefitting the entire design process, especially the early phases. The visualization of different system features at a single glance permits direct data and information exchange, enabling more direct communications among the design team. The possibility to use a distributed and shared architecture, implemented into a standard Concurrent Design Facility (CDF) setup, enhances in-depth analysis even in the product development phase. This unique VE can simulate functional and physical behaviours of the virtual replica, helping to optimize future space systems. To test the VR-based methodology, a first proof of concept has been generated following the recent incremental and evolutionary architecture strategy of considering the Moon as the next step for the human exploration of Mars and the Solar System. According the exploration roadmaps, a permanent surface base is envisioned as an efficient test-bed for assessing critical technologies to be used for future deep-space endeavours. A preliminary mission scenario has been generated which targets to settle the outpost at the lunar south pole. The peculiar environment conditions make the area rich in volatiles to examine and exploit, especially considering the permanently shadowed regions that are supposed to contain icy water deposits, which are of paramount importance for human missions. A closed-loop power system, comprising solar panels, batteries, fuel cells, electrolysers, has been sized according the settlement power needs. This research work presents an integrated simulation case study that has been run using a VE to arrive at a preliminary estimate of the performance of both the power system and the VR tool. Virtues and vices of the proposed VR-based methodology have been listed together with possible future improvements for this research field.

Increasing demands on reliability for safety critical systems such as aircraft or spacecraft require robust control and fault diagnosis capabilities as these systems are potentially subjected to unexpected anomalies and faults in actuators, input-output sensors, components, or subsystems. Consequently, fault diagnosis capabilities and requirements for aerospace applications have recently been receiving a great deal of attention in the research community. A fault diagnosis system needs to detect and isolate the presence and location of the faults, on the basis also of the control system architectures. Development of appropriate techniques and solutions for these tasks are known as the fault detection and isolation (FDI) problem. Several procedures for sensor FDI applied to a nonlinear simulated model of a commercial aircraft, in the presence of wind gust disturbances and measurement errors, are presented in this thesis. The main contributions of this work are related to the design and the optimisation of two FDI schemes based on a linear polynomial method (PM) and the nonlinear geometric approach (NLGA). In the NLGA framework, two further FDI techniques are developed; the first one relies on adaptive filters (NLGA–AF), whilst the second one exploits particle filters (NLGA–PF). The suggested design approaches leads to dynamic filters, the so–called residual generators, that achieve both disturbance decoupling and robustness properties with respect to modelling errors and noise. Moreover, the obtained results highlight a good trade-off between solution complexity and achieved performances. The FDI strategies are applied to the aircraft model in flight conditions characterised by tight–coupled longitudinal and lateral dynamics. The robustness and the reliability properties of the residual generators related to the considered FDI techniques are investigated and verified by simulating a general aircraft reference trajectory. Extensive simulations exploiting the Monte–Carlo analysis tool are also used for assessing the overall performance capabilities of the developed FDI schemes in the presence of both measurement and modelling errors. Comparisons with other disturbance–decoupling methods for FDI based on neural networks (NN) and unknown input Kalman filter (UIKF) are finally reported.

The thesis deals with the development of a new hysteresis model and the design of observers for systems with non-monotonic nonlinearities and for a clas of two-degre-of-fredom Euler- Lagrange systems (2-DOF robot). Hysteresis modeling is useful to design new smart-materials based devices, as Nitinol stent of comon use nowadays in many surgical aplications, and to improve the control of hysteretic actuators. The new model, named generalized constructive model, is able reproduce a wider clas of hysteresis nonlinearities than some of the most known models as the Clasical Preisach, the Nonlinear Preisach and the Prandtl-Ishlinski (PI) models, describing a larger number of materials. The new model is developed by an algorithm that makes use of hysteresis minor lop chords, minor lops arisen from reversal branches up to n-order. This aproach that does not make use of analytic functions, adjusting their parameters fit experimental measurements, alows to relax the hysteresis properties of equal minor lops and equal vertical chords, required by the Clasical and the Nonlinear Preisach models, buthat do not hold for a number of smart materials. Four version of the model have ben described analyzed and new les constraining properties have ben introduced to state the representation theorems of the model. The price to be paid for such wider aplicability and precision are the greater experimental measurements that ned to be colected. By mean of numerical simulations acuracy new model is compared with respecto the Clasical, Nonlinear and PI models, showing higher precision, even in the case of the experimental hysteresis temperature versus electrical resistivity of the Nitinol wire shape memory aloy. Numerical solutions for the model implementation and a rate-dependent version, for hystereses that depend also by the input rate, are proposed. To complete first part of the thesis, an academic example of a two link planarobot, which motors have ben idealy substituted by shape memory aloy actuators, show the importance of the hysteresis modeling to control such actuators. The second part of the thesis deals with reduced order observer design for nonlinear systems. observer design is derived aplying the Imersion and Invariance (I&I) technique, recently introduced in literature. This technique alows to estimate a subset of the system variables overcoming isues arisen by high gain aproaches. The design requires solution of partial diferential equations (PDEs) joined to the estimation eror definition and dynamics. This technique, asumed that solutions PDEs are obtained, is more general and alow to cope with systems for which other clasic aproaches, as the ones based on the pasivity of the estimation eror system and circle criteria based, fail for conservativenes. Then, it has ben defined a global observer for a clas of systems with non-monotonic nonlinearities, and in particular for clas of Euler-Lagrange systems with tre like mechanical configurations (robots), achieving global convergence of thestimation eror. A separation principle for the later systems is proposed with computed torque and nonlinear PD-like terms controlaw by mean of Lyapunov-based tols. Numerical simulationshown the performances of the proposed observer and the output fedback design.

Massive Multiple-Input-Multiple-Output (MIMO) is a recent technlogy that will be exploited for 5G and beyond-5G wireless network due to the constraints given by the future wireless networks, such as low latency and high spectral efficiency. In this thesis, MIMO systems have been taken into account in order to study two different network architectures. The former is called Cell-Free (CF), and it has been studied at millimeter Wave (mmWave) and microwave frequencies, and the latter is called Distributed Multiple Input Multiple Output (D-MIMO) for factory automation. The first chapter of this thesis gives an overview of massive MIMO, so why there is the need to exploit this technology and gives some mathematical concept. In the second chapter the CF at mmwave frequencies has been studied. The CF is a recent network architecture, in order to alleviate the cell-edge problem and thus increase the system performance of unlucky users that happen to be located very far from their serving Access Point (AP). In this architecture a large number of distributed APs, connected to a central processing unit (CPU), simultaneously and jointly serve a much smaller number of mobile Station (MS) or users. Both APs and users are equipped with multiple antennas. Then, it has been analyzed an architecture that generalizes the CF, the so called User-centric (UC), where each AP has to serve only a limited number of users. A power control algorithm has been introduced by resorting a method called successive lower bound maximization, aimed at maximizing the sum-rate and the energy efficiency. At mmwave, a lot of antennas can be employed, this means that there is the need of using hybrid architecture at each AP in order to reduce complexity and cost by using a small number of radio frequency (RF) chains. With CF or UC, channel estimation and beamforming are locally evaluated, reducing the traffic load on the backhaul network. So, a comparison between a fully digital (FD) and hybrid (HY) architecture will be shown. What it is possible to anticipate is that the FD architecture provides better performances than the hybrid one. In the numerical results, the performances in term of energy efficiency and sum-rate on Downlink and Uplink, with uniform and optimal power allocation and with a fully digital and hybrid architectures will be addressed. Then, this thesis also focuses on the comparison between D-MIMO and CF architectures for factory automation, at microwave frequencies. In this case, communications between actuators (ACs) and APs inside an industrial scenario is considered by adopting those different communication systems. Then, different transmission modes are taken into account, Joint transmission joint transmission (JT), Cell-Free transmission (CFT), single AP transmission (SAT), and User-centric transmission (UCT). In SAT mode each AC is served by only one AP. Even for this scenario a power control rule has been taken into account. In the end, in numerical section, it has been shown the performances in terms of SINR and achievable rate, evaluated with the finite block length capacity (FBLC) formula, when different transmission modes and beamformers are employed, and moreover the improvement given by the use of a power control.

Il controllo di sistemi meccanici è attualmente uno tra i più attivi settori di ricerca, a causa delle diverse applicazioni di sistemi meccanici nella vita reale. Gli ultimi decenni hanno visto un accresciuto interesse nel controllo di sistemi meccanici sottoattuati. Questi sistemi sono caratterizzati dal possedere più gradi di libertà che attuatori, vale a dire, uno o più gradi di libertà non sono attuati. Questa classe di sistemi meccanici è molto rappresentata nella vita reale. Esempi ne sono navi, veicoli spaziali, veicoli sottomarini, elicotteri, automobili, robot mobili, robot spaziali e manipolatori sottoattuati. Questa tesi si concentra su differenti generalizzazioni di alcuni risultati esistenti sul controllo di questa classe di sistemi, presenti nel lavoro di A. Tornambè, R. Ortega e J. W. Grizzle, con i quali ho collaborato nei tre anni del dottorato. Questi risultati sono stati ottenuti usando due diversi approcci: quello basato sulla passività e quello geometrico. Tre classi di problemi vengono trattate: 1. Disaccoppiamento ingresso-uscita per sistemi meccanici lineari sottoattuati; 2. Stabilizzazione asintotica di equilibri arbitrari in sistemi meccanici non lineari sottoattuati; 3. Stabilizzazione esponenziale di orbite periodiche in sistemi meccanici non lineari sottoattuati soggetti a impatti, con applicazioni alla robotica bipede.
Control of mechanical systems is currently among one of the most active fields of research, due to the diverse applications of mechanical systems in real life. The last decades have shown an increasing interest in the control of underactuated mechanical systems. These systems are characterized by the fact of possessing more degrees of freedom than actuators, i.e., one or more degrees of freedom are unactuated. This class of mechanical systems are abundant in real life; examples of such systems include surface vessels, spacecraft, underwater vehicles, helicopters, road vehicles, mobile robots, space robots and underactuated manipulators. The thesis focuses on different generalizations of some of the existing results on the control of this class of systems, given in the existing work of A. Tornamb, R. Ortega and J. W. Grizzle, who I collaborated with during the last three years. They have been attained by using techniques borrowed from two different approaches: the passivity-based and the geometric ones. Three classes of problems are dealt with, namely: 1. Input-output decoupling for linear underactuated mechanical systems; 2. asymptotic stabilization of arbitrary equilibria in nonlinear mechanical systems with underactuation degree one 3. exponential stabilization of periodic orbits in nonlinear underactuated mechanical systems with impulse effects, with applications to biped robot locomotion

Energy production and consumption contribute to 76% of the European greenhouse gas (GHG) emissions in 2018, and 90% of global GHG emissions with land use, land use change and forestation (LULUCF) in the same year. By applying energy efficiency (EE) and renewable energy (RE) technologies, the GHG emission intensity of the energy sector reduced by 1.3% in 2018 compared to the previous year. The current climate change policy aims at decarbonization, sustainable environment, economic prosperity and social equity. It requires the deep decarbonisation of the economies, meaning that the energy and power systems as well as other emission intensive sectors need to transform into zero-emission ones. It also requires the minimization of the environmental impacts while ensuring the economic development and meeting the need of the population growth. This thesis quantifies and evaluates the life cycle environmental impacts with focus on GHG emissions of the power sector, as consequences of changes in the environmental policy. Specifically, the thesis will answer five research questions: 1. What are climate change and energy/ power development policies in Italy? 2. What are changes in the energy/ power systems as consequences of energy climate policies? 3. What are the methods and approach for quantifying and evaluating life cycle environmental impacts as consequences of changes? 4. What are the life cycle environmental impacts of the Italian energy/ power system, with focus on GHG emissions, as consequences of changes in environmental and power policies? 5. The interactions between the energy climate policies and the environmental impacts/ GHG emissions of the Italian power system? The thesis is structured into six chapters, including two chapters of introduction and conclusion, and four chapters of answering five above-mentioned research questions. Chapter 2 provides the answers for two questions (Question 1 and Question 2) on climate and energy policies and changes in the Italian energy/power system due to climate and energy policies. Climate change and energy/ power development policy in Italy is presented in five main documents: FIT for 55, Integrated national energy and climate plan (NECP), national energy strategy (SEN), national energy efficiency action plan (PAEE), and national renewable energy action plan (NREAP). The four national documents set out the targets for EE and RE. Specifically, the targets of energy savings by 2030 include 43% reduction in primary energy consumption, 0.8% reduction in annually final energy consumption without transportation sector and 10 MTOE final energy consumption reduction. For RE, by 2030, the target is 28% ~ 30% of share of RE in total energy consumption, 55% of RE share in electricity consumption and 21% ~ 22% of RE share in transportation sector. It is expected that the electricity generation technology mix will change in order to meet the requirement on RE and EE targets set out in the Italian energy and climate policies. In this thesis, the energy scenarios called National Trend Italia (NT Italia) will be used. The NT Italia was developed by Terna and Snam, for the horizon years 2025, 2030 and 2040, using modelling tools for electricity demand, gas demand and market simulation. In these scenarios, the installed capacity of electricity by natural gas, which is slightly increased by 2040. The installed capacity of coal-based electricity and other fossil fuels-based electricity reduce from 7GW currently to 2GW by 2025, and will not change then. The scenarios also see a constant growth of electricity by RE, reaching 64 GW for solar and 25 GW for wind power (including 4.2 GW offshore) by 2040, while the installed capacity of hydropower and other renewable electricity will be stable. Chapter 3 and Chapter 4 of this thesis will deal with the research question 3, in which Chapter 3 is about the methodology and Chapter 4 focuses on the applied framework. In Chapter 3, the state of the art of consequential life cycle assessment (C-LCA) in the energy and power sectors has been reviewed. The review was conducted on 43 case studies of C-LCA in energy sector and 31 C-LCA papers in power sector. It was identified that economic models are frequently applied in combination with life cycle assessment (LCA) to conduct a C-LCA study in energy and power sectors. The identified economic models include equilibrium (partial and general equilibrium), input-output, and dynamic (agent based and system dynamic) models. Out of these, the equilibrium model is the most widely used, showing some strengths in availability of data and energy system modelling tools. The input-output model allows for describing both direct and indirect effects due to changes in the energy sector, by using publicly available data. The dynamic model is less frequently applied due to its limitation in availability of data and modelling tools, but has recently attracted more attention due to the ability in modelling quantitative and qualitative indicators of sustainability. The review indicates that the most suitable approach to conduct the study is combining one or several economic models and LCA to assess the consequential life cycle impacts of the power system. As each economic model has their own strengths and limitations, the choice of the applied models in combination with LCA largely depends on the goal of the study, the nature of the changes due to market mechanisms, economic or social origins, and the availability of data. In Chapter 4, a framework of combining Input Output Analysis (IOA) and process-based LCA for conducting the study was proposed. Moreover, this chapter provides detailed information on data collected for the model. There are several weighting points for proposing this framework. Firstly, the goal of the study is to assessing the consequential life cycle impacts of energy/ power systems. It requires the comprehensive overview of all economic sectors, as energy is connected all economic activities. The comprehensiveness will be ensured by applying IOA. At the same time, the process-based LCA will provide the detail of a sector/ a product system, which is normally a limitation of economic-wide tool such as IOA. Secondly, the change in the power system originates from economic activities (supply and demand of energy) as well as the environmental requirement to GHG emission reduction and zero carbon emissions. This change can be well modelled with an economic analysis tool (IOA) in combination with an environmental management tool (processed-based LCA). Finally, data for these tools is publicly available. The IOA depends on the input output tables (IOT), which is published every five years by the Italian Statistics (Istat). Data on energy sector is collected from Energy Balance Table, published annually by Ministry of Economic Development, the data from Terna and Snam, the database of the International Energy Agency (IEA), International Renewable Energy Agency (IRENA) and European Commission. Data on environmental aspects includes the National Accounting Matrix with Environmental Accounts (NAMEA), being collected from Istat. Data for process-based LCA is taken from ecoInvent 3. Some global database for IOA are available such as World Input Output Database (WIOD), EXIOBASE, and ect. Followings is the general framework for combining IOA and processed-based LCA to conduct a C-LCA. Consequential life cycle impact is the subtraction of the life cycle impact ‘after change’ and the life cycle impact ‘before change’. The life cycle impact ‘before change’ is quantified by applying IOA. The life cycle impact ‘after change’ depends on the change of pollutant amount, technological coefficient and the final demand due to the inclusion of renewable energy into the Italian energy system. In this thesis, multiregional input output (MRIO), a variant of IOA is used to cover several regions or countries. The application of hybrid MRIO and process-based LCA (hereinafter being called as H-MRIO) is described as followings: • First, two types of data, including MRIO and hybridization data are collected. MRIO data such as the Italian and multiregional IOTs and air emissions accounts are collected from Istat and EXIOBASE. Hybridization data is collected from Italian power/energy suppliers for power development scenarios, and from the ecoinvent database for direct air emissions of power generation technologies • From MRIO data, the MRIO model with two regions of Italy and Rest of the World (RoW) and 36 economic sectors will be constructed. • In combination with the power development scenarios, the Italian electricity sector is disaggregated into seven power generation technologies, for both intermediate flow matrices and final demand vectors in Italian IOT. Similarly, in the environmental burden matrices, the air emissions of electricity sector are disaggregated into those of seven power generation technologies, with data taken from ecoinvent. At this time, the H-MRIO model composes of 42 sectors (36 economic sectors - 1 electricity sector + 7 power technologies). • The model is calculated with historical data of 2010 and 2017 (reference scenario) and replicated for the future scenarios of 2025, 2030 and 2040. Chapter 5 focuses on applying the proposed H-MRIO framework on the Italian context, to obtained the answers for the last two research questions (Question 4 and 5). The total GHG emissions to meet global final demand in 2017 calculated in the study is at 47.69 GtCO2e, which is slightly higher than the global GHG emissions estimated by Climate Watch, at 47 GtCO2e excluding Land use change and forestation (LUCF). The difference in the obtained results of this model and other models is caused by the difference in scope of air emissions being studied. This model quantified actual anthropogenic emissions of CO2, CH4 and N2O, excluding emissions from LULUCF and biomass burning as a fuel. Meanwhile the Climate Watch’s model takes into account all GHGs (CO2, CH4, N2O, and F-gases such as HFCs, PFCs, and SF6), excluding LUCF. This causes a difference of around 1 GtCO2eq of F-gases and 2.8 Gt CO2eq of CH4. The exclusions of emissions from land use (mostly CH4), biogenic CO2 and F-gases in this model leads to an insignificant difference of around 0.69 GtCO2e (less than 1.5%). In order to look into details of the sources of the change in the air emission, a decomposition analysis has been conducted. With the change in final demand and electricity sector composition of Italy, consumption-based GHG emissions appear to decrease in the period 2010-2040. Specifically, due to changes in production structure, emission coefficients, and final demand, the annual CO2 emission reduction embodied in production activities during the period 2017- 2025 will be up to 7.1 MtCO2, which makes up 57.1 MtCO2 emission reduction in the whole period. The increased final demand of Italy causes an annual increase of 4.8 MtCO2. While the change in production structure, including electricity sector and corresponding change in other economic sectors, helps to reduce 6.1 MtCO2 annually. The change in emission flow coefficients brings an annual reduction credit of about 5.8 MtCO2. During the period of 2025-2030 and 2030-2040, the annual change in emission reduction will be much smaller, at 2.3 MtCO2 and 33.9 ktCO2 respectively. Due to the change in power supply technologies and power consumption, the future air emissions dramatically reduce in electricity sector. Most of the emissions of the domestic electricity production come from fossil fuel based electricity, e.g. electricity by coal and natural gas. A smaller part comes from other renewable electricity, including geothermal and biomass based electricity. The productions of solar and wind power do not generate any air-borne emission, and that of hydropower emits an amount of N2O. The reduction in electricity from fossil fuels such as coal and natural gas help to reduce the emissions of the domestic electricity production nearly four times from 97.5 MtCO2 in 2017 to 25.9 MtCO2 by 2040. Besides, the CO2 emission of final consumption of electricity is 34.9 MtCO2 in 2017, which reduces by more than half, at 13.7 MtCO2 by 2040. The CO2 emission of final electricity consumption is divided among technologies by their production structure. As it can be observed, low-carbon technologies such as solar and wind power technologies contribute to emissions, because of the manufacturing of their infrastructures. The emissions of final electricity consumption are smaller than that of domestic electricity production, as they are shared by other economic sectors as intermediates for production activities. The changes in electricity consumption induce changes in other economic sectors, which are clearly shown in coke and petroleum, pharmaceuticals, water transportation, education, and healthcare, either increase or decrease their emissions. Particularly, electricity sector accounts for 11.6% of the total CO2 emissions in 2017, which reduces to 5.9% by 2040. The CO2 emission shares of some other economic sectors also decrease during the period 2017-2040, such as construction and healthcare (reducing around 1 percent point). Meanwhile, the CO2 emission shares of some sectors increases, such as food and beverage (increasing less than 1 percent point). It should be noted that the CO2 emission contributions of these sectors to the national final consumption emissions do not show the correspondingly absolute increase (or decrease). Instead, they relatively present the changes in the identified ‘hotspot’ sectors over years. The absolute values of the CO2 emissions decrease in all economic sectors between 2017 and 2040. The decrease is clearly presented in economic sectors such as construction, decreasing from 20.99 MtCO2 in 2017 to 13.4 MtCO2 by 2040, at about 0.33 MtCO2 annually; or food and beverage, decreasing from 15 MtCO2 to 12.5 MtCO2, or 0.1 MtCO2 annually; or healthcare, decreasing from 17.7 MtCO2 to 11.43 MtCO2 or 0.27 MtCO2 annually in the same period. Five economic sectors holding larges shares out of total CO2 emission of final consumption includes: wholesale and retail, healthcare, food and beverage, electricity and construction (‘hotspot’ sectors). In 2017, wholesale and retail contribute to more than 12% of the total CO2 emission of the Italian final consumption. The four remaining sectors account for an average CO2 emission, from 6% to 10% of the total CO2 emissions. By 2040, the shares of emissions of these sectors remain in the same range. This emission pattern suggests that between 2017 and 2040, in order to reduce the national CO2 emissions, effort should be focused on these ‘hotspot’ sectors. Besides, the different contributions of domestic and import emissions to the total emissions suggest that Italy should have proper strategies to reduce its emissions in term of geographical effort. CO2 emissions of Italian trade partners for food and beverage, health, construction, and wholesale and retail should be taken into account because their emissions largely depends on import. The effort should be taken either to reduce their trade partners’ emission intensity, or to move away from trade partners that having high emission intensities. Meanwhile equal effort should be shared between local manufacturers and trade partners being relevant to renewable power technologies such as solar, wind and other renewable.
Energy production and consumption contribute to 76% of the European greenhouse gas (GHG) emissions in 2018, and 90% of global GHG emissions with land use, land use change and forestation (LULUCF) in the same year. By applying energy efficiency (EE) and renewable energy (RE) technologies, the GHG emission intensity of the energy sector reduced by 1.3% in 2018 compared to the previous year. The current climate change policy aims at decarbonization, sustainable environment, economic prosperity and social equity. It requires the deep decarbonisation of the economies, meaning that the energy and power systems as well as other emission intensive sectors need to transform into zero-emission ones. It also requires the minimization of the environmental impacts while ensuring the economic development and meeting the need of the population growth. This thesis quantifies and evaluates the life cycle environmental impacts with focus on GHG emissions of the power sector, as consequences of changes in the environmental policy. Specifically, the thesis will answer five research questions: 1. What are climate change and energy/ power development policies in Italy? 2. What are changes in the energy/ power systems as consequences of energy climate policies? 3. What are the methods and approach for quantifying and evaluating life cycle environmental impacts as consequences of changes? 4. What are the life cycle environmental impacts of the Italian energy/ power system, with focus on GHG emissions, as consequences of changes in environmental and power policies? 5. The interactions between the energy climate policies and the environmental impacts/ GHG emissions of the Italian power system? The thesis is structured into six chapters, including two chapters of introduction and conclusion, and four chapters of answering five above-mentioned research questions. Chapter 2 provides the answers for two questions (Question 1 and Question 2) on climate and energy policies and changes in the Italian energy/power system due to climate and energy policies. Climate change and energy/ power development policy in Italy is presented in five main documents: FIT for 55, Integrated national energy and climate plan (NECP), national energy strategy (SEN), national energy efficiency action plan (PAEE), and national renewable energy action plan (NREAP). The four national documents set out the targets for EE and RE. Specifically, the targets of energy savings by 2030 include 43% reduction in primary energy consumption, 0.8% reduction in annually final energy consumption without transportation sector and 10 MTOE final energy consumption reduction. For RE, by 2030, the target is 28% ~ 30% of share of RE in total energy consumption, 55% of RE share in electricity consumption and 21% ~ 22% of RE share in transportation sector. It is expected that the electricity generation technology mix will change in order to meet the requirement on RE and EE targets set out in the Italian energy and climate policies. In this thesis, the energy scenarios called National Trend Italia (NT Italia) will be used. The NT Italia was developed by Terna and Snam, for the horizon years 2025, 2030 and 2040, using modelling tools for electricity demand, gas demand and market simulation. In these scenarios, the installed capacity of electricity by natural gas, which is slightly increased by 2040. The installed capacity of coal-based electricity and other fossil fuels-based electricity reduce from 7GW currently to 2GW by 2025, and will not change then. The scenarios also see a constant growth of electricity by RE, reaching 64 GW for solar and 25 GW for wind power (including 4.2 GW offshore) by 2040, while the installed capacity of hydropower and other renewable electricity will be stable. Chapter 3 and Chapter 4 of this thesis will deal with the research question 3, in which Chapter 3 is about the methodology and Chapter 4 focuses on the applied framework. In Chapter 3, the state of the art of consequential life cycle assessment (C-LCA) in the energy and power sectors has been reviewed. The review was conducted on 43 case studies of C-LCA in energy sector and 31 C-LCA papers in power sector. It was identified that economic models are frequently applied in combination with life cycle assessment (LCA) to conduct a C-LCA study in energy and power sectors. The identified economic models include equilibrium (partial and general equilibrium), input-output, and dynamic (agent based and system dynamic) models. Out of these, the equilibrium model is the most widely used, showing some strengths in availability of data and energy system modelling tools. The input-output model allows for describing both direct and indirect effects due to changes in the energy sector, by using publicly available data. The dynamic model is less frequently applied due to its limitation in availability of data and modelling tools, but has recently attracted more attention due to the ability in modelling quantitative and qualitative indicators of sustainability. The review indicates that the most suitable approach to conduct the study is combining one or several economic models and LCA to assess the consequential life cycle impacts of the power system. As each economic model has their own strengths and limitations, the choice of the applied models in combination with LCA largely depends on the goal of the study, the nature of the changes due to market mechanisms, economic or social origins, and the availability of data. In Chapter 4, a framework of combining Input Output Analysis (IOA) and process-based LCA for conducting the study was proposed. Moreover, this chapter provides detailed information on data collected for the model. There are several weighting points for proposing this framework. Firstly, the goal of the study is to assessing the consequential life cycle impacts of energy/ power systems. It requires the comprehensive overview of all economic sectors, as energy is connected all economic activities. The comprehensiveness will be ensured by applying IOA. At the same time, the process-based LCA will provide the detail of a sector/ a product system, which is normally a limitation of economic-wide tool such as IOA. Secondly, the change in the power system originates from economic activities (supply and demand of energy) as well as the environmental requirement to GHG emission reduction and zero carbon emissions. This change can be well modelled with an economic analysis tool (IOA) in combination with an environmental management tool (processed-based LCA). Finally, data for these tools is publicly available. The IOA depends on the input output tables (IOT), which is published every five years by the Italian Statistics (Istat). Data on energy sector is collected from Energy Balance Table, published annually by Ministry of Economic Development, the data from Terna and Snam, the database of the International Energy Agency (IEA), International Renewable Energy Agency (IRENA) and European Commission. Data on environmental aspects includes the National Accounting Matrix with Environmental Accounts (NAMEA), being collected from Istat. Data for process-based LCA is taken from ecoInvent 3. Some global database for IOA are available such as World Input Output Database (WIOD), EXIOBASE, and ect. Followings is the general framework for combining IOA and processed-based LCA to conduct a C-LCA. Consequential life cycle impact is the subtraction of the life cycle impact ‘after change’ and the life cycle impact ‘before change’. The life cycle impact ‘before change’ is quantified by applying IOA. The life cycle impact ‘after change’ depends on the change of pollutant amount, technological coefficient and the final demand due to the inclusion of renewable energy into the Italian energy system. In this thesis, multiregional input output (MRIO), a variant of IOA is used to cover several regions or countries. The application of hybrid MRIO and process-based LCA (hereinafter being called as H-MRIO) is described as followings: • First, two types of data, including MRIO and hybridization data are collected. MRIO data such as the Italian and multiregional IOTs and air emissions accounts are collected from Istat and EXIOBASE. Hybridization data is collected from Italian power/energy suppliers for power development scenarios, and from the ecoinvent database for direct air emissions of power generation technologies • From MRIO data, the MRIO model with two regions of Italy and Rest of the World (RoW) and 36 economic sectors will be constructed. • In combination with the power development scenarios, the Italian electricity sector is disaggregated into seven power generation technologies, for both intermediate flow matrices and final demand vectors in Italian IOT. Similarly, in the environmental burden matrices, the air emissions of electricity sector are disaggregated into those of seven power generation technologies, with data taken from ecoinvent. At this time, the H-MRIO model composes of 42 sectors (36 economic sectors - 1 electricity sector + 7 power technologies). • The model is calculated with historical data of 2010 and 2017 (reference scenario) and replicated for the future scenarios of 2025, 2030 and 2040. Chapter 5 focuses on applying the proposed H-MRIO framework on the Italian context, to obtained the answers for the last two research questions (Question 4 and 5). The total GHG emissions to meet global final demand in 2017 calculated in the study is at 47.69 GtCO2e, which is slightly higher than the global GHG emissions estimated by Climate Watch, at 47 GtCO2e excluding Land use change and forestation (LUCF). The difference in the obtained results of this model and other models is caused by the difference in scope of air emissions being studied. This model quantified actual anthropogenic emissions of CO2, CH4 and N2O, excluding emissions from LULUCF and biomass burning as a fuel. Meanwhile the Climate Watch’s model takes into account all GHGs (CO2, CH4, N2O, and F-gases such as HFCs, PFCs, and SF6), excluding LUCF. This causes a difference of around 1 GtCO2eq of F-gases and 2.8 Gt CO2eq of CH4. The exclusions of emissions from land use (mostly CH4), biogenic CO2 and F-gases in this model leads to an insignificant difference of around 0.69 GtCO2e (less than 1.5%). In order to look into details of the sources of the change in the air emission, a decomposition analysis has been conducted. With the change in final demand and electricity sector composition of Italy, consumption-based GHG emissions appear to decrease in the period 2010-2040. Specifically, due to changes in production structure, emission coefficients, and final demand, the annual CO2 emission reduction embodied in production activities during the period 2017- 2025 will be up to 7.1 MtCO2, which makes up 57.1 MtCO2 emission reduction in the whole period. The increased final demand of Italy causes an annual increase of 4.8 MtCO2. While the change in production structure, including electricity sector and corresponding change in other economic sectors, helps to reduce 6.1 MtCO2 annually. The change in emission flow coefficients brings an annual reduction credit of about 5.8 MtCO2. During the period of 2025-2030 and 2030-2040, the annual change in emission reduction will be much smaller, at 2.3 MtCO2 and 33.9 ktCO2 respectively. Due to the change in power supply technologies and power consumption, the future air emissions dramatically reduce in electricity sector. Most of the emissions of the domestic electricity production come from fossil fuel based electricity, e.g. electricity by coal and natural gas. A smaller part comes from other renewable electricity, including geothermal and biomass based electricity. The productions of solar and wind power do not generate any air-borne emission, and that of hydropower emits an amount of N2O. The reduction in electricity from fossil fuels such as coal and natural gas help to reduce the emissions of the domestic electricity production nearly four times from 97.5 MtCO2 in 2017 to 25.9 MtCO2 by 2040. Besides, the CO2 emission of final consumption of electricity is 34.9 MtCO2 in 2017, which reduces by more than half, at 13.7 MtCO2 by 2040. The CO2 emission of final electricity consumption is divided among technologies by their production structure. As it can be observed, low-carbon technologies such as solar and wind power technologies contribute to emissions, because of the manufacturing of their infrastructures. The emissions of final electricity consumption are smaller than that of domestic electricity production, as they are shared by other economic sectors as intermediates for production activities. The changes in electricity consumption induce changes in other economic sectors, which are clearly shown in coke and petroleum, pharmaceuticals, water transportation, education, and healthcare, either increase or decrease their emissions. Particularly, electricity sector accounts for 11.6% of the total CO2 emissions in 2017, which reduces to 5.9% by 2040. The CO2 emission shares of some other economic sectors also decrease during the period 2017-2040, such as construction and healthcare (reducing around 1 percent point). Meanwhile, the CO2 emission shares of some sectors increases, such as food and beverage (increasing less than 1 percent point). It should be noted that the CO2 emission contributions of these sectors to the national final consumption emissions do not show the correspondingly absolute increase (or decrease). Instead, they relatively present the changes in the identified ‘hotspot’ sectors over years. The absolute values of the CO2 emissions decrease in all economic sectors between 2017 and 2040. The decrease is clearly presented in economic sectors such as construction, decreasing from 20.99 MtCO2 in 2017 to 13.4 MtCO2 by 2040, at about 0.33 MtCO2 annually; or food and beverage, decreasing from 15 MtCO2 to 12.5 MtCO2, or 0.1 MtCO2 annually; or healthcare, decreasing from 17.7 MtCO2 to 11.43 MtCO2 or 0.27 MtCO2 annually in the same period. Five economic sectors holding larges shares out of total CO2 emission of final consumption includes: wholesale and retail, healthcare, food and beverage, electricity and construction (‘hotspot’ sectors). In 2017, wholesale and retail contribute to more than 12% of the total CO2 emission of the Italian final consumption. The four remaining sectors account for an average CO2 emission, from 6% to 10% of the total CO2 emissions. By 2040, the shares of emissions of these sectors remain in the same range. This emission pattern suggests that between 2017 and 2040, in order to reduce the national CO2 emissions, effort should be focused on these ‘hotspot’ sectors. Besides, the different contributions of domestic and import emissions to the total emissions suggest that Italy should have proper strategies to reduce its emissions in term of geographical effort. CO2 emissions of Italian trade partners for food and beverage, health, construction, and wholesale and retail should be taken into account because their emissions largely depends on import. The effort should be taken either to reduce their trade partners’ emission intensity, or to move away from trade partners that having high emission intensities. Meanwhile equal effort should be shared between local manufacturers and trade partners being relevant to renewable power technologies such as solar, wind and other renewable.

To cope with the pressure of climate change and depletion of fossil fuels, distributed power generation based on sustainable and green resources, such as photovoltaic and wind, have been exploited over the past decades. High penetration of renewable energy sources challenges the normal operation of traditional power grids, due to their characteristics of intermittence and uncertainty. To address this issue, an effective way is to aggregate distributed generators, energy storage systems, and customer loads together, as a single entity, that is, the so-called microgrids. Every microgrid is a fully dispatchable unit for grid operators, relieving the strains brought by renewable energy sources. Also, microgrids are able to provide reliable power for customer loads by supporting autonomous operation. Distributed energy resources are linked to microgrids by means of power electronic converters. As most of resources and future appliances are DC in nature, DC microgrids are more appealing than their AC counterparts. They can potentially achieve higher energy conversion efficiency and lower system costs, mainly by minimizing the number of DC-AC and AC-DC power conversion stages. Droop control is a common decentralized solution to implement primary level control. With the droop control method, DC bus voltage is employed to convey the loading condition of DC microgrids, and load power can be automatically allocated among parallel resource converters. This dissertation focuses on performance improvement of droop-controlled converters, mainly in the following three aspects: i) reduction of DC bus capacitance while maintaining tight DC bus voltage regulation; ii) suppression of second-order harmonic current flowing into distributed energy resources; iii) smooth transfer from power flow control to droop control, allowing DC microgrids to seamlessly disconnect from upstream grids. The first aspect: one of the constrains to reduce DC bus capacitance is the voltage surges and sags during load changes. From this point of view, resistive output impedance is a better design option than non-resistive output impedance for resource converters. This is because, given a certain output voltage tolerance band, resistive output impedance allows larger voltage dynamic variations, so that smaller output capacitance can be used. A systematical design approach, including the selection criteria of output capacitance and the design of droop coefficient, is proposed, covering both non-isolated (buck, boost, etc.) and isolated (dual active bridge) DC-DC converters. Following this design method, resistive output impedance can be effectively obtained. On the other hand, hysteresis control is another way to further reduce output capacitance, since it features faster dynamic response than classical PID control. Herein, hysteresis controller is implemented on digital signal processors instead of field programmable gate arrays. The implementation details, including the generation of driving signals for power switches and the effect of non-negligible computation time, are presented. The second aspect: second-order harmonic power is an unavoidable issue in DC microgrids with single-phase inverters/rectifiers. Since droop-controlled converters usually show low output impedance at twice the line frequency, second-order harmonic power can flow into resource sides of converters. In some application like fuel cells, such harmonic current ripples can shorten device lifetime. To prevent the diffusion of second-order harmonic power, this dissertation studies the adoption of notch filter and resonant regulator in control loops. Although these two methods could mitigate second-order harmonic current, they deteriorate the stability performance of converters. In such a case, modified notch filter and modified resonant regulator are proposed to overcome the shortcoming of the traditional schemes. A comparative study is carried out to highlight the advantages of the proposed filter and regulator. The third aspect: there are two limitations of the traditional droop control: one limitation is that the output power of droop-controlled converters is determined by load condition, and the other one is that the power sharing performance of droop control degrades with the presence of interconnecting cable impedance. To enhance the power flexibility and accuracy, a power-based droop controller, which unifies power flow control and droop control, is proposed for resource converters. When grid-interfacing converters impose the DC bus voltage, resource converters could operate with power flow control. When grid-interfacing converters fail, resource converters could work with droop control to stabilize the system. Importantly, the switch from power flow control to droop control can be automatically accomplished without communication or detection schemes. The operation principle, the design criteria, and the power sharing performance of the proposed controller are analyzed comprehensively. All of the above-mentioned proposals are verified by relevant experimental results performing on different laboratory-scale DC microgrid prototypes.

La tesi presenta recenti sviluppi nel progetto di leggi di controllo non lineari per motori ad induzione e generatori sincroni: tecniche di controllo robuste, adattative, in retroazione dallo stato o dall'uscita sono utilizzate per tali sistemi elettromeccanici descritti da equazioni differenziali ordinarie, deterministiche e ¯nito-dimensionali e possibilmente caratterizzati da incertezze come parametri non noti (costanti o tempovarianti). I motori ad induzione, che, grazie alla loro più semplice struttura, sono più affidabili e meno costosi di quelli a magneti permanenti, a riluttanza variabile e in corrente continua, sono difficili da controllare per diverse ragioni: le dinamiche sono intrinsecamente non lineari e multivariabile (due ingressi di controllo e due uscite da controllare) ; non tutte le variabili di stato e non tutte le uscite da controllare possono essere disponibili per la retroazione; sono presenti parametri critici incerti, come la coppia di carico, tipicamente non nota in tutti i motori elettrici e la resistenza rotorica, che può variare fino al 100 % durante il funzionamento a causa del riscaldamento del rotore. La disponibilità di potenti DSP a basso costo e i progressi nell'elettronica di potenza hanno reso algoritmi complessi implementabili anche per motori ad induzione di media e piccola taglia, che, in tal modo, sono effettivamente in grado di sostituire i motori elettrici usati, ammesso che siano garantite alte prestazioni dinamiche ed elevata e±cienza: ciò ha motivato intensi sforzi di ricerca nel progetto di controllori non lineari per motori ad induzione. In modo analogo, la stabilizzazione transitoria e la regolazione della tensione per sistemi di potenza sono problemi di controllo classicamente di±cili: tutti i modelli dinamici che sono stati proposti per una singola macchina connessa a un in ¯ n ite bu s mostrano una intrinseca natura non lineare e, di conseguenza, diversi punti di equilibrio stabili e instabili. Primi studi miravano alla determinazione di regioni di stabilità delle condizioni operative desiderate, via funzioni di Lyapunov, cosi da studiare l'effetto delle improvvise perturbazioni meccaniche e elettriche che possono destabilizzare il sistema e forzare il singolo generatore ad essere disconnesso dalla rete. Il problema consiste dunque nel mantenere la velocità del generatore prossima alla velocità sincrona quando perturbazioni occorrono (stabilizzazione transitoria) e regolare la tensione di uscita al corrispondente valore di riferimento nel caso di perturbazioni costanti e permanenti (regolazione della tensione in uscita). A tal riguardo, i controllori lineari realmente impiegati, progettati sulla base di approssimazioni lineari attorno alle condizioni operative, non sono in grado di sostenere le forti perturbazioni che tipicamente occorrono nei sistemi di potenza: controllori non lineari sono di conseguenza richiesti. La tesi è suddivisa in due parti: la prima parte (motore ad induzione) è formata dai capitoli 2, 3 e 4, mentre la seconda parte (generatore sincrono) consiste dei capitoli 5 e 6. I capitoli 2 e 3 affrontano il problema del controllo di motori ad induzione senza sensore di velocità: l'esistenza di uno schema di controllo globale è esplorata nel capitolo 2 mentre una legge di controllo non lineare adattativa è progettata nel capitolo 3. Il capitolo 4 è dedicato al progetto di un controllore non lineare per motori ad induzione sen so rless: uno schema di controllo in retroazione dall'uscita è proposto. I capitoli 5 e 6 concernono il problema del controllo di un generatore sincrono con incertezze nei parametri: nel capitolo 5, un controllore non lineare robusto adattativo è presentato per la stabilizzazione transitoria, mentre il capitolo 6 propone una legge di controllo non lineare robusta adattativa che garantisce sia stabilizzazione transitoria che regolazione della tensione in uscita.
The thesis incorporates recent advances in the design of nonlinear control laws for induction motors and synchronous generators: robust, adaptive, state or output feedback control techniques are used for both these electro-mechanical systems which are modelled by ¯nite dimensional, deterministic ordinary differential equations and are possibly affected by uncertainties, such as unknown constant and time-varying parameters. Induction motors, which, due to their simpler construction, are more reliable and less expensive than those permanent magnet, switched reluctance and d.c. motors are di±cult to control for several reasons: their dynamics are intrinsically nonlinear and multivariable (two control inputs and two outputs to be controlled); not all of the state variables and not all of the outputs to be controlled may be available for feedback; there are critical uncertain parameters such as load torque, which is typically unknown in all electrical drives, and rotor resistance, which, due to rotor heating, may vary up to 100% during operations. The availability of low cost powerful digital signal processors and advances in power electronics made complex algorithms implementable even for medium- and small-size induction motors, which, in this way, could replace currently used motors provided that high dynamic tracking performance along with highpower efficiency are achieved: this is what motivated intense research efforts in induction motor control design. In analogous way, transient stabilization and voltage regulation for power systems are classically difficult control problems: all the dynamic models which have been developed for a single machine connected to an in¯nite bus show an intrinsic nonlinear nature and, consequently, there are several stable and unstable equilibrium points. Early studies aimed at determining the stability regions of desired operating conditions by means of Lyapunov functions in order to study the effect of perturbations. In fact, sudden mechanical and electrical perturbations may drive the system outside its stability region and force the generator to be disconnected from the network. The transient stabilization and voltage regulation problem consists in the design of an excitation control which keeps the generator speed close to the synchronous speed when perturbations occur (transient stabilization) and regulates the output voltage to the corresponding reference value in the case of permanent constant perturbations (voltage regulation). To this purpose, linear controllers are actually employed which are designed on the basis of linear approximations around operating conditions: only small perturbations and deviations from operating conditions can be handled. It is clear that nonlinear controllers are required to handle the large perturbations that typically occur in power systems. The thesis is divided into two parts: Part I (induction motor) consists of Chapters 2, 3 and 4 while Part II (synchronous generator) consists of Chapters 5 and 6. Chapters 2 and 3 address the problem of controlling a speed-sensorless induction motor: the existence of a global controller is explored in Chapter 2, while a nonlinear adaptive control scheme is developed in Chapter 3. Chapter 4 is devoted to nonlinear control design for a sensorless induction motor: an output feedback control algorithm is proposed. Chapters 5 and 6 address the problem of controlling a synchronous generator with parameter uncertainty: a nonlinear robust adaptive transient stabilizing control is presented in Chapter 5, while Chapter 6 proposes a nonlinear robust adaptive transient stabilizing and output regulating control algorithm.

This thesis focuses on the valuation of real options when there is flexibility given by the choice between two risky outputs. We develop models to value these rainbow options and to determine optimal operating and investment policies. These models are studied in the context of commodity applications because output flexibility is particularly relevant in volatile commodity markets. We provide insights into the behaviour and sensitivities of option values and operating policies and discuss implications for decision-making.In the early stages of real options theory, research centred on basic options with closed-form solutions, modelling single uncertainty in most cases. The challenge is now to incorporate more complexities in the models in order to further bridge the gap between theoretical models and reality, thereby promoting the widespread application of real options theory in corporate finance. The new option models developed in this thesis are organised in three self-contained research papers to address specific research problems. The first research paper studies an asset with flexibility to continuously choose the best of two risky commodity outputs by switching between them. We develop quasi-analytical and numerical lattice solutions for this real option model, taking into account operating and switching costs. An empirical application to a flexible fertilizer plant shows that the value of flexibility between the two outputs, ammonia and urea, exceeds the required additional investment cost (given the parameter values) despite the high correlation between the commodities. Implications are derived for investors and policy makers. The real asset value is mainly driven by non-stationary commodity prices in combination with constant operating costs. In the second research paper, we study an asset with flexibility to continuously choose the best of two co-integrated commodities. The uncertainty in two commodity prices is reduced to only one source of uncertainty by modelling the spread, which is mean-reverting in the case of co-integration. Our quasi-analytical solution distinguishes between different risk and discount factors which are shown to be particularly relevant in the context of mean-reversion. In an empirical application, a polyethylene plant is valued and it is found that the value of flexibility is reduced by strong mean-reversion in the spread between the commodities. Hence, operating flexibility is higher when the commodities are less co-integrated. In the third research paper, we develop real option models to value European sequential rainbow options, first on the best of two correlated stochastic assets and then on the spread between two stochastic co-integrated assets. We present finite difference and Monte Carlo simulation results for both, and additionally a closed-form solution for the latter. Interestingly, the sequential option value is negatively correlated with the volatility of one of the two assets in the special case when the volatility of that asset is low and the option is in-the-money. Also, the sequential option on the mean-reverting spread does not necessarily increase in value with a longer time to maturity.

Circadian rhythms exist in almost all of living species, and they occupy an important role in daily biological activities of these species. This thesis deals with reduction of measurements in circadian models, and recovery of circadian phases. Two mathematical models of circadian rhythms are considered, with a 3rd order model for Neurospora, and a 7th order model for Mammals. The reduction of measurements of circadian models is shown by the proposals of observer designs to the two mathematical models of circadian rhythms. Both mathematical models contain strong nonlinearities, which make the observer design challenging. Two observer designs, reduced-order and one-sided Lipschitz, are applied to the circadian models to tackle the nonlinearities. Reduced-order observer design is based on a state transformation to make certain nonlinearities have no impact on the observer errors, and the design of one-sided Lipschitz observer is based on systems with one-sided Lipschitz nonlinearities. Both observer designs are based on the existing methods in literature. The existing method of reduced-order observer has been applied to a class of multi-output nonlinear systems. A new reduced-order observer design which extends the existing one in literature is presented in this thesis. In this new reduced-order observer method, the observer error dynamics can be designed by choosing the observer gain, unlike the existing one, of which the observer error dynamics depend on the invariant zeros under certain input-output map. The recovery of circadian phases is carried out to provide a solution to phase shifts occurred in circadian disorders. The restoration of circadian phases is performed by the synchronizations of trajectories of a controlled model with trajectories of a reference model. The reference model and the controlled model have phase differences, and both these models are based on a given 3rd order model of Neurospora circadian rhythms. The phase differences are reflected by different initial conditions, and by parameter uncertainty. The synchronizations of the two models are performed by using back-stepping method for the case of different initial conditions, and by using adaptive back-stepping method for the remaining case. Several simulation studies of the proposed observer designs and the proposed schemes of synchronizations are carried out with the results shown in this thesis.

During the course of the last decade successive governments in the UK have placed young people’s aspirations at the core of their attempts to address poor outcomes within the education system and the labour market. An area-based approach to policy has come to the fore which links ‘low aspirations’ with particular community- and neighbourhood-level factors, in particular area-level deprivation. This area-based focus on the determinants of aspirations has faced intensifying critique from the academic research base. Responding to this policy and research debate, this thesis examines whether, and how, young people’s occupational aspirations are shaped by the areas they live in. The thesis is based on a mixed methods research design and has two sections: an extensive phase and an intensive phase. The extensive phase of the research consists of logistic regression analysis of data from the Understanding Society Youth Questionnaire, and considers whether the types of occupations young people aspire to vary between different types of area. The intensive phase of the research consists of phenomenographic analysis of semi-structured interviews conducted with young people in a deprived, outer-urban neighbourhood in Manchester, and considers how young people’s subjective orientations towards the area they live in produce different forms of aspiration. The thesis finds compelling evidence that young people’s occupational aspirations are shaped by the areas they live in, but does not corroborate the claim at the core of current government policy, that aspirations are lower in more deprived areas. The extensive phase of the research instead identifies area type, rather than deprivation, as the primary area-level factor shaping young people’s aspirations, with young people from particular inner city area types almost five times as likely as their peers from deprived outer-urban areas to aspire to ‘higher’ professional, managerial and technical occupations. Meanwhile, the intensive phase of the research finds evidence that experiences of neighbourhood and family life in an area of concentrated deprivation can lead young people to adopt particular forms of aspiration that require lower levels of skill and further training, but on closer examination of the motivations for these forms of aspiration, finds little evidence that these aspirations are straightforwardly ‘low’. Above all, the research demonstrates that young people produce multiple different senses of place, and myriad forms of aspiration, from within the same deprived spatial context: they do not simply reproduce what they see around them when imagining their futures. While there is compelling evidence that young people’s occupational aspirations are shaped by the areas they live in, these area effects demand more nuanced research alongside policy approaches that are more receptive to young people’s constructions of place.

Ian Pearce (1921 - 2012) was an iconic figure within the Australian jazz scene, and pioneer of traditional jazz performance practice in Tasmania. His development and approach to the assimilation of traditional jazz practices provide a model for solving the problems arising from artistic isolation, and underpin the development of his unique creative voice. This research project takes Ian Pearce’s contribution as a case study, analysing his development and improvisational modalities, in order to uncover a method of interpretation and reinterpretation of traditional jazz within the context of Tasmanian jazz heritage, that in turn has enhanced my own performance practice. This project documents processes of experiential learning through performance based on a folio of original work including commercial releases The Last Sheiks (2013) and Post Matinée (2016), and two live concert recordings. The accompanying exegesis contextualizes this research conducted through performance, adopting an auto-ethnographic approach for critical reflection on the work in the folio. It also includes a body of transcriptions of Pearce’s work that provides a unique contribution to the understanding of the musical language of a key figure within Australian jazz; an area of academic study that has thus far been under-represented.

La simbiosi industriale è un utile approccio per supportare lo sviluppo sostenibile. Valorizzando scarti prodotti da un processo produttivo come input per altri processi, le imprese possono mitigare l’impatto ambientale dei propri processi produttivi e ridurre i costi di produzione, incrementando così la propria competitività. Questa tesi si focalizza sulle self-organized industrial symbiosis networks, reti di imprese che scambiano rifiuti tra di loro. Queste reti emergono dal basso in maniera spontanea, come risultato di un processo di auto-organizzazione delle imprese coinvolte. Nonostante la letteratura scientifica riconosca le self-organized industrial symbiosis networks come uno strumento promettente, queste reti sono attualmente sottosviluppate in termini di applicazioni pratiche comparate con le opportunità teoriche. Questo aspetto limita fortemente l’efficacia dell’approccio di simbiosi industriale nell’affrontare le sfide dello sviluppo sostenibile. Lo scopo di questa tesi è supportare lo sviluppo delle self-organized industrial symbiosis networks analizzando due aspetti che, pur essendo diversi, presentano una forte interrelazione: l’emergenza spontanea di queste reti e la loro sostenibilità nel lungo periodo. La prima parte della tesi affronta due barriere che frenano l’emergenza spontanea delle self-organized industrial symbiosis networks. Nonostante queste barriere siano riconosciute dalla letteratura scientifica, nessuna soluzione è stata finora fornita. In particolare, ho formalizzato tutti i modelli di business che le imprese possono adottare per implementare l’approccio di simbiosi industriale e ho discusso i possibili scenari di business che possono nascere dalla collaborazione tra imprese diverse, ciascuna della quali orientata al proprio modello di business. Inoltre, ho progettato un meccanismo contrattuale per allineare gli incentivi tra le imprese, ripartendo in maniera equa i benefici economici creati dagli scambi simbiotici, testandone poi l’efficacia tramite simulazione ad agenti. La seconda parte della tesi è orientata a sviluppare un quadro concettuale riguardo alla sostenibilità delle self-organized industrial symbiosis networks nel lungo periodo, validandolo mediante simulazione ad agenti. Prendendo spunto dalla letteratura in campo ecologico, ho supposto che la sostenibilità delle self-organized industrial symbiosis networks nel lungo periodo possa essere massimizzata quando i network simbiotici sono caratterizzati da un bilanciamento ottimale tra due proprietà: efficienza nello scambio dei rifiuti e resilienza alle perturbazioni. In primis, ho investigato separatamente efficienza e resilienza dei network simbiotici e ho poi validato il mio quadro concettuale. La tesi è organizzata come segue. Il Capitolo 1 discute lo stato dell’arte riguardo alla simbiosi industriale e alle industrial symbiosis networks attraverso una review critica della letteratura. Inoltre, nel capitolo sono esposte le motivazioni dello studio, le specifiche domande di ricerca e le metodologie adottate. Il Capitolo 2 analizza i modelli di business che supportano la simbiosi industriale mentre il Capitolo 3 è focalizzato ai meccanismi contrattuali in grado di garantire un corretto allineamento degli incentivi tra le imprese. Il Capitolo 4 e il Capitolo 5 investigano rispettivamente le proprietà di efficienza e resilienza dei network simbiotici. Il Capitolo 6 investiga l’effetto combinato di queste proprietà sulla sostenibilità delle industrial symbiosis networks. Infine, sono esposte le conclusioni del mio lavoro.
Industrial symbiosis is a useful approach to support the sustainable development. In fact, by exchanging wastes for inputs, firms can mitigate the environmental impact of their production processes and reduce production costs, thereby increasing their competitiveness. This thesis focuses on self-organized industrial symbiosis networks, networks of firms exchanging wastes for inputs which emerge from the bottom, as the result of a self-organized process undertaken by the involved firms. Despite the literature recognizes self-organized industrial symbiosis networks as a promising tool, these networks are currently underdeveloped in terms of practical applications compared to theoretical opportunities. Such an issue strongly limits the efficacy of the industrial symbiosis approach in tackling the challenges of sustainable development. The aim of this thesis is to support the development of self-organized industrial symbiosis networks by addressing two different but related issues: the emergence and sustainability over the long period of these networks. The first part of the thesis is aimed to investigate two barriers hampering the spontaneous emergence of self-organized industrial symbiosis networks, recognized by the literature but unsolved so far. In particular, I formalized all the business models that firms can adopt to implement the industrial symbiosis approach and discussed the possible business scenarios arising from the cooperation among firms, each of them adopting its own business model. Furthermore, I designed a contractual mechanism to align the incentives among firms, fairly sharing the economic benefits stemming from the symbiotic exchanges, and tested its efficacy by adopting the agent-based simulation approach. The second part of this thesis is aimed to develop a theoretical framework for the sustainability of industrial symbiosis networks over the long period and validate it by agent-based simulations. By taking contribution from the ecological literature, sustainability of self-organized industrial symbiosis networks over the long period is supposed to be maximized when symbiotic networks are characterized by an optimal balance between two features: efficiency of waste exchanges and resilience to perturbations. Firstly, I separately investigated efficiency and resilience of industrial symbiosis networks and then I validated my theoretical framework. The thesis is organized as follows. Chapter 1 discusses the state-of-the-art about industrial symbiosis and industrial symbiosis networks through a critical review of the literature. Moreover, the motivation of this study, the specific research questions, and the adopted methodologies are presented. Chapter 2 addresses business models supporting the industrial symbiosis approach whereas Chapter 3 is focused on the contractual mechanisms aligning the incentives among firms. Chapter 4 and Chapter 5 are devoted to investigate the features of efficiency and resilience in the industrial symbiosis field, respectively. Chapter 6 investigates the effect of these features on the sustainability of industrial symbiosis networks. Finally, conclusions are provided.