The utilization of renewable energy resources such as wind and solar energy for electric power supply has received considerable attention in recent years due to adverse environmental impacts and fuel cost escalation associated with conventional generation. At the present time, wind and/or solar energy sources are utilized to generate electric power in many applications. Wind and solar energy will become important sources for power generation in the future because of their environmental, social and economic benefits, together with public support and government incentives. <p>The wind and sunlight are, however, unstable and variable energy sources, and behave far differently than conventional sources. Energy storage systems are, therefore, often required to smooth the fluctuating nature of the energy conversion system especially in small isolated applications. The research work presented in this thesis is focused on the development and application of reliability and economic benefits assessment associated with incorporating wind energy, solar energy and energy storage in power generating systems. A probabilistic approach using sequential Monte Carlo simulation was employed in this research and a number of analyses were conducted with regards to the adequacy and economic assessment of generation systems containing wind energy, solar energy and energy storage. The evaluation models and techniques incorporate risk index distributions and different operating strategies associated with diesel generation in small isolated systems. Deterministic and probabilistic techniques are combined in this thesis using a system well-being approach to provide useful adequacy indices for small isolated systems that include renewable energy and energy storage. The concepts presented and examples illustrated in this thesis will help power system planners and utility managers to assess the reliability and economic benefits of utilizing wind energy conversion systems, solar energy conversion systems and energy storage in electric power systems and provide useful input to the managerial decision process.

The utilization of renewable energy resources such as wind and solar energy for electric power supply has received considerable attention in recent years due to adverse environmental impacts and fuel cost escalation associated with conventional generation. At the present time, wind and/or solar energy sources are utilized to generate electric power in many applications. Wind and solar energy will become important sources for power generation in the future because of their environmental, social and economic benefits, together with public support and government incentives. <p>The wind and sunlight are, however, unstable and variable energy sources, and behave far differently than conventional sources. Energy storage systems are, therefore, often required to smooth the fluctuating nature of the energy conversion system especially in small isolated applications. The research work presented in this thesis is focused on the development and application of reliability and economic benefits assessment associated with incorporating wind energy, solar energy and energy storage in power generating systems. A probabilistic approach using sequential Monte Carlo simulation was employed in this research and a number of analyses were conducted with regards to the adequacy and economic assessment of generation systems containing wind energy, solar energy and energy storage. The evaluation models and techniques incorporate risk index distributions and different operating strategies associated with diesel generation in small isolated systems. Deterministic and probabilistic techniques are combined in this thesis using a system well-being approach to provide useful adequacy indices for small isolated systems that include renewable energy and energy storage. The concepts presented and examples illustrated in this thesis will help power system planners and utility managers to assess the reliability and economic benefits of utilizing wind energy conversion systems, solar energy conversion systems and energy storage in electric power systems and provide useful input to the managerial decision process.

In recent years, smart gird has received much attention, and many researchers have devoted to home area network (HAN) to improve the efficiency of grid. This thesis proposes a bidirectional isolated DC-DC converter (Dual Active Bridge, DAB) with phase shift control to implement the concept of HAN. Li+Fe battery is used as storage device of the converter, and a bidirectional communication between Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW) and Digital Signal Processor (DSP) is realized by CAN-bus. By setting the current command given by LabVIEW system, the converter is able to charge the Li+Fe battery with constant current and constant voltage method as well as discharge the Li+Fe battery with constant current. Operation principle of the converter and the associated loss are presented.

This thesis presents a novel aspect and polarization invariant electromagnetic target recognition technique in resonance region based on use of MUSIC algorithm for the extraction of natural-resonance related target features. In the suggested method, the feature patterns called &ldquo / MUSIC Spectrum Matrices (MSMs)&rdquo / are constructed for each candidate target at each reference aspect angle using targets&rsquo / scattered data at different late-time intervals. These individual MSMs correspond to maps of targets&rsquo / natural-resonance related power distributions. All these patterns are first used to obtain optimal late-time interval for classifier design and a &ldquo / Fused MUSIC Spectrum Matrix (FMSM)&rdquo / is generated over this interval for each target by superposing MSMs. The resulting FMSMs include more complete information for target resonances and are almost insensitive to aspect and polarization. In case of multiple target recognition, the relative locations of a multi-target group and separation distance between targets are also important factors. Therefore, MSM features are computed for each multi-target group at each &ldquo / reference aspect/topology&rdquo / combination to determine the optimum late-time interval. The FMSM feature of a given multi-target group is obtained by the superposition of all these aspect and topology dependent MSMs. In both single and multiple target recognition cases, the resulting FMSM power patterns are main target features of the designed classifier to be used during real-time decisions. At decision phase, the unknown test target is classified either as one of the candidate targets or as an alien target by comparing correlation coefficients computed between MSM of test signal and FMSM of each candidate target.

In this thesis a multifunctional DC/DC converter board will be developed for utilization as an educational experiment set in the switched-mode power conversion laboratory of power electronic courses. The board has a generic power-pole structure allowing for easy configuration of various power converter topologies and includes buck, boost, buck-boost, flyback, and forward converter topologies. All the converters can be operated in the open-loop control mode with a switching frequency range of 30-100 kHz and a maximum output power of 20 W. Also the buck converter can be operated in voltage mode control and the buck-boost converter can be operated in peak-current-mode control for the purpose of demonstrating the closed loop control performance of DC/DC converters. The designed board allows for experimentation on the DC/DC converters to observe the macroscopic (steadystate/ dynamic, PWM cycle and low frequency) and microscopic (switching dynamic) behavior of the converters. In the experiments both such characteristics can be clearly observed such that students at basic learning level (involving only the macroscopic behavior), and students at advanced learning level (additionally involving the parasitic effects) can benefit from the experiments. The thesis reviews the switch mode conversion principles, gives the board design and proceeds with the experiments illustrating the capabilities of the experimental system.

Lightning is a natural phenomenon involving transient high current discharge in the atmosphere. Cloud-to-ground lightning, wherein the discharge occurs between the cloud and the ground is quite hazardous to systems on the ground. Apart from threat to life, the devastating effects of lightning can be mainly of thermal, mechanical and electromagnetic origin. Many a times, thermal and electromagnetic effects are of main concern. A direct hit, wherein the system under consideration becomes a part of the lightning path, could be quite catastrophic to many vulnerable systems like oil rigs, chemical factories, missile/satellite launch pads. From the safety and operational point of view, lightning is of serious concern for electrical systems including transmission lines and substations, nuclear power stations, telecommunication station and data banks. Lightning cannot be avoided, however, by employing a suitable Lightning Protection System (LPS), adequate protection against a direct hit can be provided to ground based systems. A typical lightning protection system involves: 1) Air termination network, which is responsible for stroke interception, 2) Down conductor system, which provides to the stroke current a minimal impedance path to the ground and 3) Earth termination network, for safe dissipation of current into the ground. Similarly, for the indirect effects, which are basically of electromagnetic origin, suitable protection can be designed. The key factors in a protective action involve interception of the dangerous strokes, minimization of the consequential potential rise on down conductors, as well as, at earth termination and keeping the field in the protective volume within an acceptable level. The last aspect can be generally categorized into secondary level protection. For critical systems, the lightning protection system is generally isolated from it. In such designs, potential rise on LPS governs the physical isolation required between the protected and protection system. For a given level of bypass strokes, cost of the LPS increases with the amount of physical separation employed. All most all of the earlier works have concentrated on lightning surge response of power transmission line towers. Apart from their relatively moderate heights, the intention was to arrive at a model, which can be incorporated in circuit simulation software like EMTP. Consequently, they envisage or approximate the mode of propagation to be TEM. In reality, for down conductors of height greater than say 30 m, only TM mode prevails during the initial critical time period. Hence the earlier models cannot be extended to general lightning protection schemes and for down conductor of larger lengths. Only limited literature seems to be available on the characteristics of general down conductor configurations. The problem in hand is very important and some serious research efforts are very much essential. In view of the above, the present work aims to evaluate the rise in potential as well as current injected into the soil at the base for: (i) practical range of down conductor configurations involving single down conductor (with height exceeding 30 m) and (ii) pertinent values of stroke current parameters. The protection schemes considered are isolated vertical down conductor, isolated tower (both square and triangular cross-section) and, tower with insulated lightning mast carrying ground wires. The parameters under consideration are: (i) height and cross section for the down conductor, (ii) clearance between the down conductor and the protected system, (iii) channel geometry, wherein only inclination is to be considered, (iv) velocity of current along the channel and (v) wave shape and rise time for the stroke current. For the evaluation of lightning surge response of transmission line towers, many theoretical and experimental approaches are found in the literature. However, works considering the TM mode of current propagation is relatively limited. In that both experimental and theoretical approaches have been adopted. Theoretical approach invariably adopted numerical field computation in frequency domain using Numerical Electromagnetic code (NEC-2). Fourier Transform techniques are employed to extract the time domain quantities. This approach is very economical, free from experimental errors and least time consuming. Hence it is selected for the present work. However, there are certain limitations in this approach. In NEC simulation, there is a restriction on the size and the arrangement of individual elements. Therefore, although fairly complex tower structures can be simulated, some simplification in the geometry is unavoidable. Such an approximation has been reported to cause insignificant error. NEC is not accurate for calculations in low frequency regime. But in the present work, the initial time regime is of concern wherein the high frequency components dominate. Therefore the above said limitation is not of any serious concern. In order to validate the approach, potential rise is computed for 120 m tall cylindrical down conductor and tower. Results are compared favorably with earlier works, which are based on potential lead wire method. A careful re-look into the ’potential rise’ on the down conductors reveal several things. The electric field in the region between the protection system and protected system is the root cause for the breakdown/flashover. For a given geometry, the integral of the electric field along the shortest path between the two systems must be representing the overall stress on the air gap. Further, for the later time periods, this integral coincides with the well-known quasi-static potential. All the available data and models for breakdown of long air gaps are basically in terms of this quasi-static potential. In view of this, the above path integral is defined as ’equivalent potential rise’ (which will be hereafter termed as ’potential rise’), and taken as the index for surge response. Further, observation of the computed spatio-temporal radial electric field around the down conductor reveals some additional features, which are not common in the quasi-static regime. Electric field reverses its polarity in space, which is due to the opposite current flowing in the lightning channel. Therefore, ’potential rise’, which is taken as the representative for the dielectric stress on the air, should not be evaluated for larger distances. Considering this and noting that the protected system generally lies well within a distance of 50% of the H, height of the down conductor, potential rise is evaluated by integrating electric field within this distance (12.5%H, 25%H, 50%H). Three heights (100%H, 75%H, 50%H) are considered for the evaluation of the potential. The influences of various down conductor and lightning channel parameters are analyzed. Finally vertical channel with full velocity for current propagation is arrived for the investigations. Also, the influence of neighboring conducting objects is briefly studied. It is argued that it needs to be ignored for the general study. Analysis is carried out for a range of down conductor configurations of heights ranging from 45 m to 120 m. Cylindrical down conductor is selected for the detailed study on the overall characteristics and its dependency on pertinent parameters. The characteristics of potential rise are found to be significantly different from that given by the commonly employed uniform transmission line model. In the regime of very fast front currents, down conductor of comparable heights have comparable potential rise. For the larger time to crest, behavior tends more to wards that for quasi-static regime. The dependency of the potential rise on radius of the down conductor seems to be logarithmic in nature. Surge response of isolated towers of both square and triangular cross sections is studied for heights ranging from 45 m to 120 m. The overall characteristics are found to be similar to cylindrical down conductor. Dispersive propagation is found to exist on towers. As a result, the base currents are slightly lower and potential rise exhibits less oscillations. Data curves on potential rise at three different heights and for three different spatial extents are generated for the range of down conductor heights with rise time of the stroke current as the variable. Several interesting observations have been made. Next the investigation is taken up for the insulated mast scheme. The parameters of the study are taken as the number of ground wires, grounding location of ground wires and length of the insulation cylinder. Potential across the insulation, tower base currents, and ground wire end currents are deduced. The basic characteristics of the potential rise are shown to be quite similar to that for the transmission line. For fast front currents the temporal variation is bipolar with a smooth decay. In other words, oscillations are sustained for considerably longer duration. Voltage stress across the insulation surface for one ground wire design is found to be higher by 1.4 - 2.4 times than that for isolated tower. The highest amplification of the ground end current, which occurs for fast front currents, is about 1.8 times. Potential difference across the insulation for two-ground wire design is higher by a factor of 1.3 - 1.85 than that for isolated tower. For the design with four ground wires, potential across the insulation is comparable with that for the tower. However, the mechanical strength of the insulating support should also be considered in the selection of number of ground wires. There exists, especially for fast front strokes, significant induction to the supporting tower. The height of the insulation seems to possess no appreciable influence on the potential rise and base currents. Several issues need to be considered before selecting this design. The contribution made by the present work can be summarized as follows. It basically deals with lightning surge response of isolated down conductors of height in the range 45 - 120 m. The configurations considered are, cylindrical down conductor, tower with both square and triangular cross section and insulated mast scheme. It makes a careful study on the ’potential rise’ on down conductors and a suitable definition for the same is proposed. Basic characteristics of potential rise and ground end currents are studied for the above-mentioned designs. Their salient features are enumerated. For the towers, design data curves are provided for relevant range of stroke current rise time. The issues that need to be considered in the insulated mast scheme are discussed along with the data on potential rise and base currents. The findings of this work are believed to be very useful for the design of lightning protection scheme involving isolated down conductor. Further the results are useful in analyzing the consequential lightning generated threat of being close to tall towers.

Η αυξητική ορμόνη (GH) παίζει ιδιαίτερα σημαντικό ρόλο, καθώς προάγει κυρίως τη μεταγεννητική κατά μήκος αύξηση, και ελέγχει το μεταβολισμό των λιπιδίων και των υδατανθράκων, τη σύνθεση των πρωτεϊνών και τη διέγερση του ανοσοποιητικού συστήματος. Η ανεπάρκεια GH (GHD) διαγιγνώσκεται είτε με παθολογικές συγκεντρώσεις της GH στον ορό μετά από πρόκληση με φαρμακολογικούς παράγοντες που διεγείρουν την έκκριση της (κλασσική GHD), είτε με φυσιολογικές προκλητές δοκιμασίες αλλά παθολογικό 24ωρο εκκριτικό ρυθμό της GH (GH νευροεκκριτική δυσλειτουργία, GHND). Οι GHD και GHND ασθενείς έχουν σοβαρή καθυστέρηση αύξησης και ανταποκρίνονται καλά στην εξωγενή θεραπεία με hGH. Κοντό ανάστημα που σχετίζεται με ανεπάρκεια αυξητικής ορμόνης (GHD) μπορεί να είναι σποραδικού τύπου και ιδιοπαθής, αλλά στο 5-30% των περιπτώσεων υπάρχει προσβεβλημένος πρώτου βαθμού συγγενής, που υποδηλώνει γενετική αιτιολογία. Μεταλλάξεις του γονιδίου της GH (GH1) ευθύνονται για την εκδήλωση οικογενούς μεμονωμένης ανεπάρκειας GH (IGHD). Ο εγγύς υποκινητής του GH1 γονιδίου παρουσιάζει υψηλού βαθμού πολυμορφισμό, με τουλάχιστον 16 αναγνωρισμένους πολυμορφισμούς (SNPs) σε έκταση 535 βάσεων, που εκδηλώνονται σε σύνολο 40 απλότυπων, κάποιοι από τους οποίους επηρεάζουν την έκφραση της GH. Σκοπός της παρούσας εργασίας ήταν η ανεύρεση αλλαγών στην αλληλουχία του GH1 γονιδίου της αυξητικής ορμόνης (GH) και του εγγύς υποκινητή του σε ασθενείς με οικογενή μεμονωμένη ανεπάρκεια GH (IGHD), αλλά και η ανάλυση του τρόπου κληρονομικότητας αυτών των αλλαγών. Μελετήθηκαν 33 IGHD ασθενείς (29 GHD και 4 GHND), τα μέλη των οικογενειών τους (22 οικογένειες) και 31 μάρτυρες. Απομονώθηκε γονιδιωματικό DNA από λεμφοκύτταρα περιφερικού αίματος και πραγματοποιήθηκε πολλαπλασιασμός του GH1 γονιδίου και του υποκινητή του με την αλυσιδωτή αντίδραση πολυμεράσης (PCR). Τα δείγματα αλληλουχήθηκαν και προσδιορίστηκαν αλλαγές της αλληλουχίας με βάση την NCBI, blast- Μ28466.1-βάση δεδομένων. Στους ασθενείς μετρήθηκαν τα επίπεδα IGF-1, τα επίπεδα των άλλων ορμονών του πρόσθιου λοβού του αδένα της υπόφυσης, η μέγιστη τιμή GH μετά από προκλητές δοκιμασίες με κλονιδίνη και L-Dopa, και στους 4 GHND ασθενείς πραγματοποιήθηκε 24ωρη καταγραφή της αυθόρμητης έκκρισης της GH. Οι πολυμορφισμοί (SNPs) που ανιχνεύθηκαν στο GH1 γονίδιο και τον υποκινητή του σε ασθενείς και μάρτυρες, ελέγχθηκαν για τη συχνότητα των γονοτύπων τους, και συσχετίστηκαν με κλινικοεργαστηριακά χαρακτηριστικά, ενώ ο δυνητικός λειτουργικός ρόλος των μεταλλάξεων ελέγχθηκε με λογισμικά προγράμματα. Η αλληλούχιση του GH1 γονιδίου και του υποκινητή του ανέδειξε 18 γνωστούς από τη βιβλιογραφία SNPs στον υπό μελέτη πληθυσμό και τρεις νέες (novel) μεταλλάξεις στις 3 από τις 22 οικογένειες. Ανάλυση με το λογισμικό πρόγραμμα MatΙinspector των 2 ετερόζυγων σημειακών μεταλλάξεων που εντοπίστηκαν στον GH1 υποκινητή, -485G>C and -400G>A, αποκάλυψε θέση πρόσδεσης για τον μεταγραφικό παράγοντα E-twenty six-1 (ETS-1). Ανάλυση της τρίτης ετερόζυγης μετάλλαξης (G>A) στη θέση +300 του εσωνίου 1 του GH1 γονιδίου με τα λογισμικά ESEfinder3 και ASSP αποκάλυψε τη δημιουργία μιας κρυφής θέση ματίσματος και διάσπαση της περιοχής ματίσματος εξωνίου (ESE) ενός ψευδοεξωνίου, μειώνοντας τον αριθμό προσδενόμενων πρωτεϊνών πλούσιων σε σερίνη-αργινίνη (SR). Η στατιστική ανάλυση των συχνοτήτων των γονοτύπων στους πολυμορφισμούς υψηλής συχνότητας, και η συσχέτιση τους με παραμέτρους που σχετίζονται με την αύξηση, την έκκριση της GH, αλλά και την ανταπόκριση στην hGH αγωγή, έδειξε ότι οι GHD ασθενείς πιθανόν να εμφανίζουν διαφορετική μεταγραφική δραστηριότητα στο GH1 γονίδιο λόγω των θέσεων -278, -57 του υποκινητή, -6 της 5΄ UTR περιοχής και της θέσης +1169 του γονιδίου, που έρχεται σύμφωνο και με άλλες μελέτες, αλλά και της θέσης -31, που αναφέρεται για πρώτη φορά. Αυτοί οι πολυμορφισμοί συσχετίστηκαν με μειωμένα επίπεδα IGF-1. Από την άλλη, οι SNPs που αναγνωρίσθηκαν στους GHND ασθενείς, παρόλο που είναι παρόμοιοι με αυτούς των GHD ασθενών, συσχετίστηκαν με παραμέτρους αύξησης και όχι με τα επίπεδα IGF-1. Οι 18 πολυμορφισμοί και οι 3 μεταλλάξεις που εντοπίστηκαν στους GHD και GHND ασθενείς φαίνεται να συμβάλουν μερικώς και μεμονωμένα ή συνεργικά στη μεταγραφή του GH1 γονιδίου και συνεπώς στην έκκριση της GH, ενώ η διαφορετική συμμετοχή των SNPs στους GHD και GHND ασθενείς πιθανόν αντανακλά και τη διαφορετική εκδήλωση της νόσου. Η κατανόηση της φαινοτυπικής ποικιλότητας των ασθενών με IGHD και των γενετικών αιτιών μπορεί να βοηθήσει στη κατανόηση των μηχανισμών που ενέχονται στον έλεγχο της αύξησης, αλλά και στη βελτίωση της παρακολούθησης και της θεραπείας των ασθενών. / Growth hormone (GH) plays a pivotal role in a number of physiological processes by promoting postnatal longitudinal body growth, lipid and carbohydrate metabolism, protein biosynthesis and activation of the immune system. GH deficiency (GHD) is diagnosed either by subnormal levels of serum GH during two hGH stimulation tests by pharmacological agents that physiologically stimulate GH secretion (classic form of GHD), or normal serum GH levels, but subnormal 24hr GH profile (Neurosecretory GH deficiency, GHND). Children with GHD and GHND have severe growth retardation and respond to exogenous human GH (hGH) therapy with significant catch-up growth. Short stature associated with isolated GH deficiency (GHD) is both sporadic and idiopathic, but between 5 and 30% have an affected first degree relative consistent with a genetic etiology. Mutations identified on the GH gene (GH1) associate with the manifestation of familial isolated GH deficiency (IGHD). The proximal promoter region of GH1 exerts a highly polymorphic region, with at least 16 single nucleotide polymorphisms (SNPs) identified over a region of 535bp, manifested by a total of 40 haplotypes, some of which affect the GH1 expression. The aim of this study was to identify possible changes in the sequence of the GH1 gene of growth hormone (GH) and its promoter region in patients with familial isolated GH deficiency (IGHD), together with the analysis of the inheritance pattern of such genetic changes. 33 IGHD patients (29 GHD and 4 GHND), their 1st degree relatives (22 families) and 31 controls were investigated. Genomic DNA was extracted from the lymphocytes of the subjects peripheral blood and the GH1 gene was amplified by the Polymerase Chain Reaction (PCR). The samples were sequenced and the changes were identified according to the sequence M28466.1 of the NCBI blast database. The levels of IGF-1 and other hormones of the pituitary were measured in the patients and the highest level of GH during the clonidine and L-Dopa hGH stimulation test were recorded, whereas in the 4 GHND patients a spontaneous 24hr GH profile was conducted. The sequencing results were analyzed for the frequencies of the genotypes of the identified SNPs and for any possible correlations with the clinical or biochemical characteristics of the patients and the controls. Additionally, the possible functional role of the found mutations was assessed using specific programs. The sequencing of GH1 and its promoter revealed 18 SNPs in the whole sample and 3 novel mutations in 3 of the 22 investigated families. Analysis with MatInspector of the 2 heterozygous nucleotide mutations located at the promoter regions -485GC and -400GA, respectively, revealed a binding sequence for the transcription factor E-twenty six-1 (ETS-1). Analysis of the third heterozygous mutation (GA) at the +300 region of intron 1 with ESEfinder3 και ASSP revealed a cryptic splicing position and disruption of the exon splicing enhancement (ESE) region by reducing the binding affinity of serine-arginine proteins (SRs). The frequency and correlation analysis showed that the GHD patients possible exert differential transcriptional activity at the GH1 gene via the SNPs at positions -278, -57 of the promoter, -6 of 5΄ UTR region, +1169 of intron 4, which is in accordance to previous studies, and also the newly reported SNP at -31 region. These SNPs associated also with decreased IGF-1 levels. On the other hand, the SNPs identified in the GHND patients, although similar to the GHD patients, correlated with several growth parameters, irrespective to the IGF-1 levels. The 18 SNPs and 3 mutations identified in the sample seem to contribute partially and individually or in synergy to the transcriptional regulation of GH1 in the GHD and GHND patients. The SNPs contribution is differentially exerted in the GHD patients, when compared to the GHND patients and this possibly reflects the different expression of the disease. The investigation of phenotypic variance in IGHD patients and their genetic predisposition can potentially improve our perception of the underlying mechanisms of growth and offer valuable information for the better therapeutic management of IGHD patients.

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