Development and characterization of a distributed measurement system for the evaluation of voltage quality in electric power networks

The research activity carried out during the PhD course in Electrical Engineering belongs to the branch of electric and electronic measurements. The main subject of the present thesis is a distributed measurement system to be installed in Medium Voltage power networks, as well as the method developed to analyze data acquired by the measurement system itself and to monitor power quality. In chapter 2 the increasing interest towards power quality in electrical systems is illustrated, by reporting the international research activity inherent to the problem and the relevant standards and guidelines emitted. The aspect of the quality of voltage provided by utilities and influenced by customers in the various points of a network came out only in recent years, in particular as a consequence of the energy market liberalization. Usually, the concept of quality of the delivered energy has been associated mostly to its continuity. Hence the reliability was the main characteristic to be ensured for power systems. Nowadays, the number and duration of interruptions are the “quality indicators” commonly perceived by most customers; for this reason, a short section is dedicated also to network reliability and its regulation. In this contest it should be noted that although the measurement system developed during the research activity belongs to the field of power quality evaluation systems, the information registered in real time by its remote stations can be used to improve the system reliability too. Given the vast scenario of power quality degrading phenomena that usually can occur in distribution networks, the study has been focused on electromagnetic transients affecting line voltages. The outcome of such a study has been the design and realization of a distributed measurement system which continuously monitor the phase signals in different points of a network, detect the occurrence of transients superposed to the fundamental steady state component and register the time of occurrence of such events. The data set is finally used to locate the source of the transient disturbance propagating along the network lines. Most of the oscillatory transients affecting line voltages are due to faults occurring in any point of the distribution system and have to be seen before protection equipment intervention. An important conclusion is that the method can improve the monitored network reliability, since the knowledge of the location of a fault allows the energy manager to reduce as much as possible both the area of the network to be disconnected for protection purposes and the time spent by technical staff to recover the abnormal condition and/or the damage. The part of the thesis presenting the results of such a study and activity is structured as follows: chapter 3 deals with the propagation of electromagnetic transients in power systems by defining characteristics and causes of the phenomena and briefly reporting the theory and approaches used to study transients propagation. Then the state of the art concerning methods to detect and locate faults in distribution networks is presented. Finally the attention is paid on the particular technique adopted for the same purpose during the thesis, and the methods developed on the basis of such approach. Chapter 4 reports the configuration of the distribution networks on which the fault location method has been applied by means of simulations as well as the results obtained case by case. In this way the performance featured by the location procedure firstly in ideal then in realistic operating conditions are tested. In chapter 5 the measurement system designed to implement the transients detection and fault location method is presented. The hardware belonging to the measurement chain of every acquisition channel in remote stations is described. Then, the global measurement system is characterized by considering the non ideal aspects of each device that can concur to the final combined uncertainty on the estimated position of the fault in the network under test. Finally, such parameter is computed according to the Guide to the Expression of Uncertainty in Measurements, by means of a numeric procedure. In the last chapter a device is described that has been designed and realized during the PhD activity aiming at substituting the commercial capacitive voltage divider belonging to the conditioning block of the measurement chain. Such a study has been carried out aiming at providing an alternative to the used transducer that could feature equivalent performance and lower cost. In this way, the economical impact of the investment associated to the whole measurement system would be significantly reduced, making the method application much more feasible.

Studio del comportamento flesso-torsionale di un telaio in materiale composito per vettura sportiva

Lo studio svolto in merito alle tecniche di produzione di componenti strutturali in materiale composito ha permesso il raggiungimento di una precisa consapevolezza dello stato dell’arte del settore, in particolare in riferimento ai processi attualmente utilizzati per l’industrializzazione in media-grande serie. Con l’obiettivo di sintetizzare i principali vantaggi delle tecnologie suddette e permettere la realizzazione di forme più complesse, si è proceduto all’analisi di fattibilità, attraverso uno studio funzionale e una prima progettazione di una tecnologia di produzione per nastratura automatizzata di componenti strutturali in materiale composito. Si è voluto quindi dimostrare la flessibilità e la consistenza del processo disegnando un telaio nastrato in carbonio, intercambiabile al telaio FSAE 2009 in tubolare d’acciaio (stessi punti di attacco motore, punti di attacco telaietto posteriore, attacchi sospensioni anteriori) e che garantisca un sostanziale vantaggio in termini di peso, a pari rigidezza torsionale. La caratterizzazione di tale telaio è stata eseguita mediante l'utilizzo del calcolo strutturale, validato da prove sperimentali.

Produzione automatizzata per nastratura di componenti strutturali in materiale composito

Questa dissertazione tratterà l’argomento dello studio di metodi di progettazione e processi tecnologici innovativi per l’industrializzazione in medio-grande serie di componenti strutturali in materiale composito. L’interesse della ricerca verso questo ambito è suscitato dai notevoli vantaggi che l’utilizzo di materiali dall’alto rapporto prestazioni meccaniche/peso danno nella ricerca di elevate prestazioni in applicazioni sportive e diminuzione dei consumi ed emissioni inquinanti in mezzi di trasporto di grande serie. Lo studio di componenti in materiale composito è caratterizzato dalla peculiarità di non poter disgiungere la progettazione della geometria della parte da quella del materiale e del processo, ed in questo senso nella figura del progettista si vanno a riassumere sinergicamente competenze riguardanti i tre ambiti. Lo scopo di questo lavoro è la proposizione di una metodologia di progettazione e produzione di componenti strutturali che permetta l’utilizzazione ottimale della natura fibrosa del materiale composito sia dal punto di vista del trasferimento dei carichi tra diversi componenti, sia dal punto di vista del processo di laminazione che avviene per nastratura automatizzata. Lo studio è volto a mostrare in quali termini tale tecnologia sia potenzialmente in grado di superare i vincoli di forma ed i limiti di efficienza meccanica delle giunzioni tra le parti e di garantire maggiore produttività e costi inferiori rispetti ai diversi metodi di produzione che rappresentano oggi lo stato dell’arte dell’industrializzazione in medio-grande serie. Particolare attenzione verrà posta sull’utilizzo della tecnologia oggetto di studio per la produzione di telai automobilistici.

Modelling and analysis of networked control strategies in smart power distribution grids: development of co-simulation tools

This thesis is focused on Smart Grid applications in medium voltage distribution networks. For the development of new applications it appears useful the availability of simulation tools able to model dynamic behavior of both the power system and the communication network. Such a co-simulation environment would allow the assessment of the feasibility of using a given network technology to support communication-based Smart Grid control schemes on an existing segment of the electrical grid and to determine the range of control schemes that different communications technologies can support. For this reason, is presented a co-simulation platform that has been built by linking the Electromagnetic Transients Program Simulator (EMTP v3.0) with a Telecommunication Network Simulator (OPNET-Riverbed v18.0). The simulator is used to design and analyze a coordinate use of Distributed Energy Resources (DERs) for the voltage/var control (VVC) in distribution network. This thesis is focused control structure based on the use of phase measurement units (PMUs). In order to limit the required reinforcements of the communication infrastructures currently adopted by Distribution Network Operators (DNOs), the study is focused on leader-less MAS schemes that do not assign special coordinating rules to specific agents. Leader-less MAS are expected to produce more uniform communication traffic than centralized approaches that include a moderator agent. Moreover, leader-less MAS are expected to be less affected by limitations and constraint of some communication links. The developed co-simulator has allowed the definition of specific countermeasures against the limitations of the communication network, with particular reference to the latency and loss and information, for both the case of wired and wireless communication networks. Moreover, the co-simulation platform has bee also coupled with a mobility simulator in order to study specific countermeasures against the negative effects on the medium voltage/current distribution network caused by the concurrent connection of electric vehicles.

Analysis of cumulative effects of multiple stressors on saltmarshes and consideration of management options

Natural systems face pressures exerted by natural physical-chemical forcings and a myriad of co-occurring human stressors that may interact to cause larger than expected effects, thereby presenting a challenge to ecosystem management. This thesis aimed to develop new information that can contribute to reduce the existing knowledge gaps hampering the holistic management of multiple stressors. I undertook a review of the state-of-the-art methods to detect, quantify and predict stressor interactions, identifying techniques that could be applied in this thesis research. Then, I conducted a systematic review of saltmarsh multiple stressor studies in conjunction with a multiple stressor mapping exercise for the study system in order to infer potential important synergistic stressor interactions. This analysis identified key stressors that are affecting the study system, but also pointed to data gaps in terms of driver and pressure data and raised issues for potentially overlooked stressors. Using field mesocosms, I explored how a local stressor (nutrient availability) affects the responses of saltmarsh vegetation to a global stressor (increased inundation) in different soil types. Results indicate that saltmarsh vegetation would be more drastically affected by increased inundation in low than in medium organic matter soils, and especially in estuaries already under high nutrient availability. In another field experiment, I examined the challenges of managing co-occurring and potentially interacting local stressors on saltmarsh vegetation: recreational trampling and smothering by deposition of excess macroalgal wrack due to high nutrient loads. Trampling and wrack prevention had interacting effects, causing non-linear responses of the vegetation to simulated management of these stressors, such that vegetation recovered only in those treatments simulating the combined prevention of both stressors. During this research I detected, using molecular genetic methods, a widespread presence of S. anglica (and to a lesser extent S. townsendii), two previously unrecorded non-native Spartinas in the study areas.