Η παρούσα διδακτορική διατριβή αναφέρεται σε οικιακά Φ/Β συστήματα συνδεδεμένα στο δίκτυο χαμηλής τάσης, τα οποία αξιοποιούν την τεχνολογία των Φ/Β Πλαισίων Εναλλασσομένου Ρεύματος (Φ/Β Πλαίσια Ε.Ρ. – AC-PV Modules). Πρόκειται για Φ/Β διατάξεις μικρής ισχύος (έως 300W), οι οποίες δημιουργούνται από την ενσωμάτωση ενός μόνο Φ/Β πλαισίου και ενός μετατροπέα (ενός η πολλών σταδίων) συνεχούς τάσης σε μονοφασική εναλλασσόμενη τάση, σε μια αυτοτελή ηλεκτρονική διάταξη. Για το λόγο αυτό ονομάζονται και Φ/Β πλαίσια με ενσωματωμένο μετατροπέα (Module Integrated Converters, MIC). Στα συστήματα αυτά οι απαιτήσεις για επίτευξη υψηλού βαθμού απόδοσης, για την καλύτερη εκμετάλλευση της παρεχόμενης ηλιακής ενέργειας, καθώς και ρεύματος ημιτονοειδούς μορφής στην έξοδο είναι αδιαμφισβήτητες. Βασικός σκοπός της παρούσας διατριβής είναι η συμβολή της στον τομέα των Φ/Β μονάδων διεσπαρμένης παραγωγής και επικεντρώνεται στην ενδελεχή ανάλυση, στη βελτιστοποίηση της λειτουργικής συμπεριφοράς, στον υπολογισμό των απωλειών στα στοιχεία του μετατροπέα, στην παραμετροποίηση και τελικά στο βέλτιστο σχεδιασμό ενός αντιστροφέα ρεύματος τύπου Flybcak (Flyback Current Source Inverter – Flyback CSI). Οι κύριοι στόχοι που έπρεπε να εκπληρωθούν για την ολοκλήρωση της παρούσας διατριβής ήταν:  Η ενδελεχής ανάλυση της λειτουργίας του αντιστροφέα για δύο διαφορετικές στρατηγικές ελέγχου που εφαρμόζονται σε αυτόν.  Ο κατά το δυνατόν ακριβέστερος υπολογισμός των απωλειών στα στοιχεία του Flyback CSI, καθώς και η παραμετροποίηση των σχέσεων αυτών.  Ο βέλτιστος σχεδιασμός του Flyback CSI, ο οποίος βασίζεται στη διατύπωση της μεγιστοποίησης του σταθμισμένου βαθμού απόδοσης ως πρόβλημα βελτιστοποίησης.  Η υλοποίηση του ελέγχου της λειτουργίας του μετατροπέα μέσω ψηφιακού μικροελεγκτή, καταργώντας τον ήδη υφιστάμενο αναλογικό έλεγχο. Αρχικά η μελέτη επικεντρώνεται σε μία πρώτη τεχνική ελέγχου, η οποία ωθεί τον μετατροπέα να λειτουργεί στην περιοχή της ασυνεχούς αγωγής (Discontinuous Conduction Mode, DCM). Στη συνέχεια προτείνεται μία δεύτερη τεχνική ελέγχου η οποία, αφ' ενός μεν αναγκάζει το μετατροπέα να λειτουργεί στο όριο συνεχούς και ασυνεχούς αγωγής (Boundary between Continuous and Discontinuous Conduction Mode, BCM), αφ' ετέρου δε παρέχει καθαρά ημιτονοειδές ρεύμα στην έξοδο. Με την προτεινόμενη νέα τεχνική ελέγχου, που ονομάσθηκε i-BCM (improved BCM) και αποτελεί βελτίωση της υπάρχουσας στη βιβλιογραφία τεχνικής ελέγχου BCM, βελτιώνεται σημαντικά ο συντελεστής ισχύος στην έξοδο του αντιστροφέα, παρέχοντας στο δίκτυο καθαρά ημιτονοειδές ρεύμα. Οι δύο διαφορετικές στρατηγικές ελέγχου διαμορφώνουν διαφορετικές κυκλωματικές συνθήκες. Για τις δύο περιπτώσεις αναπτύσσονται αναλυτικές εκφράσεις τόσο για τη μέση, όσο και για την ενεργό τιμή των ρευμάτων που διαρρέουν όλα τα στοιχεία του μετατροπέα (ημιαγωγικά στοιχεία, Μ/Σ κλπ). Επιπρόσθετα, εξάγονται κριτήρια για τα ασφαλή όρια λειτουργίας του μετατροπέα με γνώμονα την καταπόνηση των ημιαγωγικών στοιχείων ισχύος από υψηλές τιμές τάσης και ρεύματος. Ιδιαίτερο βάρος δίνεται στον υπολογισμό της διακύμανσης της τάσης του πυκνωτή του φίλτρου εξόδου, η οποία αναπτύσσεται και πάνω στα ημιαγωγικά στοιχεία του μετατροπέα, επηρεάζοντας την επιλογή τους. Στην συνέχεια, προσδιορίζονται μέσω αναλυτικών μαθηματικών σχέσεων οι απώλειες αγωγής και οι διακοπτικές απώλειες των ημιαγωγικών στοιχείων και προσεγγίζονται, με ιδιαίτερη λεπτομέρεια, οι απώλειες του μετασχηματιστή (τυλιγμάτων και πυρήνα) και για τις δύο προαναφερθείσες στρατηγικές ελέγχου, δεδομένου ότι η διακοπτική συχνότητα λειτουργίας του μετατροπέα είναι υψηλή. Για το λόγο αυτό απαιτείται εις βάθος μελέτη της υπάρχουσας βιβλιογραφίας, επιλογή ή επινόηση των κατάλληλων μοντέλων απωλειών σε ένα Μ/Σ (πυρήνα και χαλκού) και προσήκουσα προσαρμογή αυτών στις κυκλωματικές συνθήκες του αντιστροφέα Flyback. Παράλληλα με την ανάλυση των απωλειών πραγματοποιείται και η παραμετροποίηση του συστήματος. Η διαδικασία αυτή στηρίζεται στη διαχείριση των εξισώσεων κατά τέτοιο τρόπο ώστε να προσδιορίζονται όλες οι μεταβλητές και οι σταθερές του μετατροπέα, καθώς και οι παράμετροι από τις οποίες εξαρτώνται οι απώλειες, με τον απλούστερο δυνατό τρόπο. Συνεπώς, έχει δοθεί ιδιαίτερη έμφαση στην διαχείριση των αναλυτικών σχέσεων ώστε οι απώλειες, χωρίς έκπτωση στην ακρίβεια, να εξαρτώνται από τον ελάχιστο δυνατό αριθμό παραμέτρων. Με αυτό τον τρόπο η μελέτη είναι πλήρης αλλά περιορίζεται η πολυπλοκότητα, με αποτέλεσμα να προκύπτουν μόνο τέσσερις ανεξάρτητες σχεδιαστικές μεταβλητές. Στο επόμενο στάδιο, πραγματοποιείται ο βέλτιστος σχεδιασμός του Flyback CSI, ο οποίος βασίζεται στη διατύπωση της μεγιστοποίησης του σταθμισμένου βαθμού απόδοσης ως πρόβλημα βελτιστοποίησης. Αυτό, πρακτικά, σημαίνει τον προσδιορισμό της αντικειμενικής συνάρτησης (objective ή cost function), των σχεδιαστικών μεταβλητών και σταθερών, των περιοριστικών συνθηκών και τον ορισμό του πεδίου τιμών αυτών. Ο σταθμισμένος βαθμός απόδοσης αποτελεί την αντικειμενική συνάρτηση, ενώ οι προδιαγραφές εισόδου και εξόδου του μετατροπέα αποτελούν τις σχεδιαστικές σταθερές.. Με τη χρήση μίας στοχαστικής μεθόδου βελτιστοποίησης, η οποία αναδείχτηκε ως η πιο κατάλληλη έπειτα από εκτεταμένη βιβλιογραφική αναζήτηση, προσδιορίζονται οι τιμές των τεσσάρων σχεδιαστικών μεταβλητών και επιτυγχάνεται ο μέγιστος δυνατός σταθμισμένος βαθμός απόδοσης. Η επίτευξη του στόχου ολοκληρώνεται με την ανάπτυξη ενός νέου επαναληπτικού αλγορίθμου, με τον οποίο, βάσει των εξισώσεων των απωλειών, επιτυγχάνεται ο βέλτιστος σχεδιασμός του Flyback CSI και για τις δύο διαφορετικές τεχνικές ελέγχου. Επιπροσθέτως, υλοποιείται ο έλεγχος της λειτουργίας του μετατροπέα μέσω ψηφιακού μικροελεγκτή, καταργώντας τον ήδη υφιστάμενο αναλογικό έλεγχο. Η αλλαγή της φιλοσοφίας υλοποίησης του ελέγχου προσφέρει μεγαλύτερη ευελιξία και ανεξάντλητες δυνατότητες στην κατάστρωση και υιοθέτηση διαφορετικών στρατηγικών ελέγχου. Ιδιαίτερα, κατά τη λειτουργία στο όριο μεταξύ συνεχούς και ασυνεχούς αγωγής (i-BCM), με κατάλληλο προγραμματισμό του μικροελεγκτή εξαλείφεται η ανάγκη για μέτρηση των ρευμάτων στα τυλίγματα του μετασχηματιστή. Ο μικροελεγκτής που χρησιμοποιείται είναι ο dspic30F4011 της εταιρείας Microchip ο οποίος διαθέτει μεγάλη υπολογιστική ικανότητα και μία πληθώρα περιφερειακών που επιτρέπουν αυτοματοποίηση κάποιων λειτουργιών, όπως η διαδικασία σύνδεσης και αποσύνδεσης με το δίκτυο και η δυνατότητα ενσωμάτωσης της μονάδας ανίχνευσης του μέγιστου σημείου ισχύος (M.P.P.T) της Φ/Β γεννήτριας στην ίδια ψηφιακή μονάδα. Τέλος, υλοποιήθηκαν εργαστηριακά πρωτότυπα με βάση τις βέλτιστες παραμέτρους που υπολογίσθηκαν σε κάθε περίπτωση σύμφωνα την προτεινόμενη μέθοδο βελτιστοποίησης και ακολούθησε πειραματική επιβεβαίωση με χρήση ενός αναλυτή ισχύος υψηλής ακρίβειας, για την επιβεβαίωση των θεωρητικών προσεγγίσεων. Επιπλέον, μελετήθηκε η ευεργετική επίδραση της συνδυαστικής χρήσης των δύο τεχνικών ελέγχου στην πυκνότητα ισχύος / This thesis pertains to domestic on-grid PV systems that utilize the AC-PV Modules technology. These low power PV topologies (up to 300W) are implemented by integrating one PV Module and a single phase inverter (one or multi stage), in one independent electronic apparatus. For this reason they are called Module Integrated Converters (MIC). The most important requirements for these systems are the higher possible efficiency - in order to take advantage of the supplied solar energy – and the pure sinusoidal output current. The main purpose of this thesis is to contribute to the field of the dispersed PV power generation. Thus, it focuses on the thorough analysis, the behaviour optimization, the components losses estimation, the parameterization and finally the optimal design of Flyback current source inverter (Flyback CSI). The main objectives fulfilled in this thesis are: • The detailed analysis of the inverter behaviour for two different semiconductor control strategies. • The precise losses calculation of all the components of the Flyback CSI. • The optimal design of the Flyback CSI, which is based on maximizing the weighted efficiency. • The implementation of the semiconductor control via a digital microcontroller, eliminating the existing analogue control. Initially, the study focuses on a first control technique that forces the inverter to function in Discontinuous Conduction Mode (DCM). On the other hand, a second control technique that forces the inverter to function on the Boundary between Continuous and Discontinuous Mode (BCM) is proposed. This new control technique is named i-BCM (improved BCM) and it is an improved version of the BCM control technique found in the literature. This new control scheme significantly improves the power factor of the inverter output. The inverter injects pure sinusoidal current to the grid. The two different control strategies form different circuit conditions. Analytical expressions for the average and the rms value of the current, flowing through the components (semiconductors, transformers e.t.c), for both cases are developed. In addition, new operating boundaries of the semiconductors for the safe operation of the inverter based on the analysis of the voltage and current that stresses the semiconductors, are proposed. Special attention is given on the calculation of the voltage deviation on the output filter capacitor. This voltage deviation is caused by the switching operation of the inverter and affects the selection of the semiconductors and the voltage level that can handle. Furthermore, the conduction losses and the switching losses of the semiconductors are determined through analytical, mathematical equations. Because of the inverter high switching frequency, the transformer losses (copper and core), are calculated with special attention to detail. For this reason, an in depth examination of the existing literature takes place that leads to the selection of the appropriate core and copper loss models. The models are adequately adjusted to the circuit conditions of the Flyback inverter topology. The system is parameterized along with the losses analysis. All the equations are manipulated in such a way that simplifies the determination of all the variables and all the constants of the inverter and the loss dependent parameters. Consequently, special emphasis is given to the manipulation of the analytical equations, without affecting the accuracy, in order to express the losses using the minimum number of independent variables. Therefore, the study is complete but the complexity is eliminated and the independent design variables are only four. The optimization problem is the maximization of the weighted efficiency. The optimal design of the Flyback CSI is implemented based on this formulation. As a next step, the objective (or cost) function, the design variables and constants, the constraints and their range need to be defined. The weighted efficiency is the objective function whereas the input and the output specifications of the inverter are the design constants. After an extensive literature research, a stochastic optimization method is chosen as the most appropriate to determine the values of the four design variables in order to achieve the highest weighted efficiency. A new iterative algorithm, which uses the losses equations, is developed to achieve the optimal design of the Flyback CSI for both control strategies. Moreover, the control of the inverter is implemented via a digital microcontroller, eliminating the existing analogue control. This changes the way of controlling the inverter and offers flexibility and limitless possibilities in implementing and adopting various control strategies. Specifically, under the i-BCM control scheme, the need for measuring the current of the transformer windings is eliminated by using an appropriate algorithm. The microcontroller used in this research is dspic30F4011 developed by Microchip. Its good computational capacity and the variety of peripherals enable the automation of some functions such as connection and disconnection from the grid and the integration of the maximum power point tracking (M.P.P.T.) on the same digital unit. Finally, laboratory prototypes are implemented, based on the optimal parameters calculated for every case, using the proposed optimization method. The experimental procedure confirmed the theoretical approximations. A high precision power analyser was used. Furthermore, the beneficial effect of the combined use of the two control power techniques on the power density is also studied.

Made available in DSpace on 2014-06-11T19:30:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-11-06Bitstream added on 2014-06-13T19:00:48Z : No. of bitstreams: 1 garbelini_e_dr_ilha.pdf: 758680 bytes, checksum: 9f08146d542679d2c1da479912ffd576 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O fluxo de carga convencional é considerado inadequado para a obtenção do ponto de máximo carregamento devido a singularidade da matriz Jacobiana. Os métodos da continuação são ferramentas eficientes para a solução deste tipo de problema, e diferentes parametrizações são utilizadas para evitar a singularidade da matriz. Neste trabalho apresentase uma técnica de parametrização geométrica que possibilita o traçado completo das curvas PV sem os problemas de mal condicionamento. A técnica proposta associa a robustez com a simplicidade e a facilidade de compreensão. A singularidade da matriz Jacobiana é eliminada pela adição da equação de uma reta que passa por um ponto no plano formado pelas variáveis perdas de potência ativa totais e o fator de carregamento, dois parâmetros físicos de fácil compreensão. A técnica, aplicada aos sistemas do IEEE (14, 30, 57, 118 e 300 barras) e ao sistema brasileiro sul-sudeste (638 e 787 barras), mostra que as características do fluxo de carga não só são preservadas, mas também melhoradas. Diversos testes são realizados para proporcionar a comparação do desempenho do esquema de parametrização proposto para o método do fluxo de carga continuado. / The conventional Newton’s method has been considered inadequate to obtain the maximum loading point of power systems due to the Jacobian matrix singularity. Continuation methods are efficient tools for solving this kind of problem, and different parameterizations are used to avoid the matrix singularity. This paper presents a new geometric parameterization scheme that allows the complete tracing of the PV curves without ill-conditioning problems. The proposed technique associates the robustness to the simplicity and easy understanding. The Jacobian matrix singularity is overcome by the addition of a line equation, which passes through a point in the plane, determined by the real power losses and loading factor variables, two parameters with clear physical meaning. The application of this new technique to the IEEE systems (14, 30, 57, 118 and 300 buses) and to the Brazilian systems south-southeast (638 and 787 buses) shows that the characteristics of the conventional Newton’s method are not only preserved but also improved. Several tests are carried out to compare the performance of the proposed parameterization scheme for the continuation power flow method.

Thin film coatings of ZnO, TiO2, CeOX and BiOX have been deposited on soda lime silica glass through spray pyrolysis. The effects on the optical properties of the coated glass, as well as the possible impacts on the life expectancy and energy efficiency of PV-modules have been studied. ZnO and TiO2 coatings both reduced the transmission of UV radiation of wavelengths destructive to PV-modules. Therefore, both have the potential to increase the life expectancy of PV-modules if used on cover glass. The ZnO thin film also showed an increase in photoluminescence at 377 nm when radiated with UV radiation of 325 nm while TiO2 reduced the photoluminescence. ZnO coatings on the cover glass have the potential to increase the efficiency of PV-modules in addition to UV protection. No CeOX or BiOX films were found to be deposited with the method used. The ZnO and TiO2 coated samples showed a decrease in transmission of light, due to increased reflection and possibly scattering. This needs to be addressed if these kinds of coatings are going to be beneficial for Si PV-modules.

Sammanfattning Mer än en fjärdedel av Indiens befolkning motsvarande 311 miljoner människor saknar elanslutning. Det allra flesta av dem bor i fattigar landsbygden. Indien är även en av dem största producenterna av lök i världen där staten Maharashtra står för 30 % och distriktet Nashik för 60 %. Gällande förvaringen av lök på landsbygden i Nashik, i området Sinnar, är det ett problem. Under perioder med hög temperatur och hög luftfuktighet i distriktet ruttnar lökarna som förvaras som resultat kan inte bönderna sälja sina lökar på marknaden och allt slängs. Med hjälp av den icke-statliga organisationen Yuva Mitra i Indien och Mälardalens Högskola har detta arbete kunnat utföras till följd att hjälpa bönderna. Syftet med detta arbete har varit att komma med ett förbättringsförslag av nuvarande förvaringslager till lökarna. Främst att bönderna ska kunna bevara sina lökar i gott skick och öka deras livslängd så att dem kan användas och säljas till marknaden framöver. Fältstudier gjordes i Sinnar under två månader där det ingick intervjuer med bönder, producentföretag, chefer på ” National bank for agriculture and rural development” (NABARD) och kyl företag i både Sverige och Indien. Observationer gjordes också på tre olika förvaringslagrar och andra jordbruksfält i både byn Vadangali och Wadgaon. Beräkningar på en kyleffekt gjordes i Sverige med hjälp av en beräkningsmall, för kylbehovsberäkning av kyllager, och med hjälp av litteraturstudier. Programmet PVsyst användes för att beräkna hur stort ett solcellssystem krävs för att driva en kompressorkylmaskin. Revit användes för ritning av en exempel modell på ett kyllager med bestämt material och mått. Ekonomisk utvärdering utfördes för att se investeringskostnaden och återbetalningstiden. Ett förvaringslager i byn Vadangali valdes för detta arbete som utpunkt för förbättring. Lagret har en area på 105 m2, volym på 420 m3 och rymmer maximalt 50 ton lök. Förvaringstiden är på 8 månader mellan mars och oktober månad. Materialet som används idag är av lokalnivå, trä längder, plåt och stålgaller, lagret är sponsrat av regeringen och kostade cirka 35 500 kr. Arbetet inkluderade utformandet av ett kyllager med en kompressorkylmaskin driven av ett fristående solcellssystem. Det föreslagna kyllagret har samma area som det nuvarande, dock en annan volym på 525 m3, och är dessutom utformat för att klara av en inomhustemperatur på 0°C. Detta kräver en kyleffekt av 20 kW samt en soleffekt av 18,48 kW med arean 153 m2 på solpanelen som skall placeras på marken med hjälp av en ställning. Solpanelens ska även placeras med en riktning mod syd och ha en vinkel på 20 grader för att uppnå maximal effekt. Två resultat åstadkoms av detta arbete varav ena är ett självbyggt kyllager med ett solcellssystem, och den andra en prefabricerad kyllager med ett kylaggregat med samma solcellssystem. Som slutsats av detta arbete är bästa lösningen med lägst investeringskostnad och återbetalningstid en prefabricerad kyllager med kylaggregat och ett solcellssystem som ska driva kompressorn med elenergi. Den totala investeringskostnaden med bidrag och lån från NABARD för ett sådant system kommer att kosta 240 633 kr vilket motsvarar en återbetalningstid på 4 år. Nyckelord: Kyllager, solcellssystem, solenergi, kompressorkylmaskin, Yuva Mitra, lök, producentföretag, landsbygdsutveckling, jordbruk, förvaringslager / Abstract India is one of the largest producers of onion in the world, which means that there is a great demand of storage facilities for the harvested onions. Indian onion farmers usually don’t use cold storage for their onions because of lack of electricity in the rural areas. During periods of high temperature and high humidity large quantities of stored onions rot. This results in much of the produce being wasted as the rotten onions cannot be sold to the market. This is a serious problem to the farmers in Nashik, situated in a block called Sinnar. The non-government organization Yuva Mitra in Nashik is supporting farmers to improve their storage of onions. Malardalens University has been asked to assist the NGO with this, therefore this work has been carried out to investigate how to improve the cooling of harvested onions, in order to improve the situation for the onion farmers. The aim of the study was to investigate cost- and energy effective solutions to provide electricity to the farmers, using solar power, allowing the farmers to build a cold storage. The purpose of this work has been to present a suggestion for improvement of an existing warehouse that currently is used by the onion farmers in Nashik. The main purpose is to provide a solution to the farmers that allows them to preserve their onions in good condition and increase the onions lifetime so that more onions can be sold to the market. Field studies were made in Sinnar, including interviews with farmers, the producer companies, managers at "National Bank for Agriculture and Rural Development" (NABARD) and cooling companies in both Sweden and India. Calculations of cooling effect were made in Sweden using a calculation template, for cooling calculations of cold storage, and with the help of literature. The solar program, PVsyst, was used to calculate how big a PV system has to be to operate a compressor chiller. The Revit program was used to draw a model example of a cold storage with selected materials and dimensions. An economic evaluation was conducted to determine the investment cost and payback period. The suggested cold storage has the same area as the current storage facility of ​​105 m2, but a larger volume of 525 m3. The suggested storage can accommodate a maximum of 50 tons of onions. It is designed to hold an indoor temperature of 0°C, which requires a cooling capacity of 20 kW and solar power of 18,48 kW with a solar panel area of ​​153 m2 to be placed with a position on the ground facing south at an angel of 20 degrees. The results show that the total investment with grants and loans from NABARD for such a system will be 240 633 SEK, which corresponds to a payback period of 4 years. The best solution with the lowest investment cost and with the lowest payback period is a prefabricated warehouses, which has chillers and a solar system to drive the compressor with electrical energy. Keywords:    cooling storage, PV-system, solar energy, compressor chiller, Yuva Mitra, onion, Producer Company, rural development, agriculture, warehouse

Dissertation (DTech(Electrical Engineering))--Cape Peninsula University of Technology, 2012 / The confluence of the limited resources of fossil fuels (e.g. coal, oil and natural gas), environmental degradations leading to climate change, security of supplies and fossil fuels high costs have demanded a tremendous efforts on humanity to seek for a sustainable and unlimited natural energy sources. Amongst these renewable energy sources stands out solar energy because of its ubiquitousness. Solar energy is converted to DC electricity by the photovoltaic effect. Photovoltaic (PV) power systems installed in commercial and industrial buildings are a good example of distributed power generation. Here the energy consumption and production match and thus electricity taken from the grid during daytime peak hours can be reduced. This is beneficial as the transmission losses in the grid are avoided and also transmission need is reduced. The cost effectiveness of a solar energy system has hindered its wide adoption and deployment in terms of the initial capital cost even though it has a zero energy cost and very minimal operating and maintenance costs. Different governments have instituted many financial incentives for fast adoption of PV systems for both residential and commercial applications. However, all these incentives are not sustainable in the longer term forecast. For PV system to attain grid parity requires more than unsustainable approach of many governments providing time limited subsidies. The technical solution to the problem is to reduce the overall system cost through technical innovations. One such method is the adoption of transformerless inverter technology as the grid interface system. Transformerless inverter topology provides galvanic isolation through innovative inverter topology and switching strategies that eliminates problems created by not employing the service of transformer.

Resumo: O brócolis (Brassica oleracea var. italica) é uma espécie exigente em nutrientes, destacando-se os elementos nitrogênio e potássio, que são exigidos em maiores quantidades pelas plantas, podendo influenciar na produção, qualidade e também na severidade de diversas doenças. Com o objetivo de estudar os efeitos desses elementos na severidade da podridão negra, causado por Xanthomonas campestris pv. Campestri (Xcc) e a sua influência na produção de brócolis tipo inflorescência única, foi realizado o experimento no Departamento de Produção Vegetal/Horticultura da FCA/UNESP - Botucatu. O delineamento utilizado foi em parcela subdividida com fatorial na subparcela, em blocos casualisados com quatro repetições. Na parcela avaliou-se a influência da inoculação (plantas não inoculadas e inoculadas com Xcc) e na subparcela avaliou-se o fatorial 4 x 4, doses de potássio (0, 275, 550 e 825 kg ha-1) e nitrogênio (0, 150, 300 e 450 kg ha-1). O híbrido de brócolis utilizado foi o BRO68 (Rogers). A semeadura foi realizada em 18/02/2004 e as plântulas foram transplantadas aos 33 dias após semeadura (DAS) em vasos de dez litros, sob ambiente protegido. Realizou-se a inoculação pelo método de palito (64 DAS) e as colheitas foram realizadas de 28/05/2004 a 12/06/2004 (99 aos 114 DAS). As adubações foram realizadas no plantio, pela incorporação ao solo de 45% da dose de potássio e 10% da dose de nitrogênio de cada tratamento e em cobertura, aplicados via fertirrigação (55% do potássio e 90% do nitrogênio). Foram avaliadas a severidade da Xcc através do PANC (porcentagem da altura necrosada do caule) e porcentagem das folhas retidas nas plantas (FR), produção e diâmetro das cabeças, teores de macronutrientes, no momento da inoculação e na colheita...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Broccoli is one vegetable specie that demand fertilizers, mainly nitrogen and potassium are required in higher quantity, which can have influence in yields, quality and severity level of diseases. Evaluated the influence of nitrogen and potassium fertilizations in black rot (Xanthomonas campestris pv. campestris) severity and broccoli yields, in the Departamento de Produção Vegetal/Horticultura - FCA/UNESP - Botucatu country, São Paulo State, Brazil. The experimental design was split plot with factorial in plot, in randomized blocks with four replicants. In the plot was evaluated the influence of inoculation (plant no inoculated or inoculated with Xcc (Xanthomonas campestris v. campestris) with four replications, considering potassium rates (0, 275, 550 and 825 kg ha-1) and nitrogen rates (0, 150, 300 and 450 kg ha-1). Hybrid BRO 68 (Rogers) was seeded in 18/02/2004 and transplanted in 33 days after seeding (DAS) for pot with 10 liters of capacity in plastic house conditions. The Xcc inoculation was made using "toothpick" methods (64 DAS) and the harvesting occurs in 28/05/2004 to 12/06/2004 (99 to 114 DAS). Incorporated in soil before planting with 45% potassium rate and 10% nitrogen rate of each treatment, and after planting fertilization was in fertirrigation system (55% potassium and 90% nitrogen). The severity of Xcc was evaluated with a PANC (percentage of necrosed height of the stem) method and the percentage of leaf kept in plants, the broccoli yield and the diameter of head, macronutrients ratios, was assessment during inoculations and the harvesting. The results showed that interactions among of three factors did not have significance for neither characteristics, potassium x nitrogen fertilizers interactions was significance to yield, head diameter, and PANC and macronutrients ratios (N, P, K, Ca and Mg)...(Complete abstract click electronic access below) / Orientador: Rumy Goto / Coorientador: Antonio Carlos Maringoni / Banca: Roberto Lyra Villas Bôas / Banca: Marcia de Moraes Echer / Banca: Rômulo Fujito Kobori / Banca: Margarida Fumiko Ito / Doutor

A indução de resistência envolve a ativação de mecanismos de defesa latentes existentes nas plantas em resposta ao tratamento com agentes bióticos ou abióticos. As plantas apresentam sistema de defesa induzível, com a finalidade de economizar energia. Desse modo, a resistência induzida em condições naturais representará custo apenas na presença do patógeno. Porém, plantas que investem seus recursos para se defenderem na ausência de patógenos arcarão com custos que refletirão na produtividade, uma vez que as alterações metabólicas que levam a resistência apresentam custo adaptativo associado, o qual pode pesar mais do que o benefício. O efeito negativo na produtividade ocorre principalmente onde indutores químicos são utilizados repetidas vezes ou em doses mais elevadas. Assim, em alguns casos podemos estar caminhando sobre uma estreita linha entre custo e benefício, onde a cura pode ser tão ruim quanto a própria doença. Neste trabalho foram conduzidos experimentos objetivando verificar alterações bioquímicas e fisiológicas, correlacionando-as com parâmetros de produção do feijoeiro entre a indução mediada por acibenzolar-S-metil (ASM), indutor químico, e, a mediada por Bacillus cereus, indutor biológico, antes da chegada do patógeno. Para tanto, foram avaliados plantas de feijão, induzidas por esses dois indutores e desafiadas com Xanthomonas axonopodis pv. phaseoli, para constatar a ocorrência do fenômeno da indução de resistência. Na ausência do patógeno, foram avaliados os parâmetros fisiológicos respiração e fotossíntese, determinada a atividade de enzimas envolvidas no processo de defesa como peroxidase, quitinase, β-1,3-glucanase, fenilalanina amônia-liase e polifenoloxidase e a atividade de enzimas envolvidas no catabolismo como proteases, a síntese de compostos do metabolismo secundário como fenóis totais e lignina, a síntese de compostos do metabolismo primário como proteínas e açúcares redutores. Também se avaliou o crescimento das plantas, a produtividade e parâmetros de produção e alguns parâmetros de qualidade dos grãos. Observou-se a ocorrência da indução de resistência em função da aplicação dos dois indutores utilizados, porém para o indutor ASM a indução de resistência estava associada a aumentos na atividade de peroxidase, quitinase, β-1,3-glucanase e proteases, aumento da síntese de lignina e redução no teor de fenóis, aumentos no teor de proteínas solúveis e de açúcares redutores nas folhas, redução do crescimento e da produtividade, aumento do teor de proteína dos grãos e redução do teor de amido nestes. Já o B. cereus apenas ocasionou aumento na atividade de peroxidase de forma atenuada e tendeu a aumentar a atividade de proteases, e reduzir o teor de proteínas nas folhas sem interferir no crescimento ou na produtividade, mas reduziu o teor de proteína dos grãos, mas aumentou o teor de amido nestes. Portanto, o indutor B. cereus , aparentemente alterou muito pouco o metabolismo do feijoeiro, sem interferir na produtividade e melhorando a qualidade da produção, enquanto que o indutor abiótico ASM alterou muito mais seu metabolismo, gerando um custo metabólico e redirecionando os fotoassimilados para investir em defesas, a custo da redução da produtividade. / The induction of systemic resistance involves the activation of latent resistance mechanisms in plants against pathogens in response to the treatment with biotic or abiotic agents. The plants present latent defense system that can be activated with the goal of saving energy. Thus, the induced resistance under natural conditions will represent cost only in the pathogen presence. In this way, plants that invest their resources to defend themselves in the absence of the pathogen will pay off with costs that will reflect in productivity, since the metabolic changes that led to resistance have associated fitness cost which could outweigh the benefit. The negative effects on plant productivity usually occur when chemical inducers are used repeatedly or in higher doses, mainly in the absence of the pathogen. Thus, we can say that in some cases we can be walking on a fine line between cost and benefit, where the cure may be as bad as the disease itself. In this work, experiments were carry out to verify biochemical and physiologic alterations, correlating them with production parameters of bean plants treated with acibenzolar-S-methyl (ASM), chemical inducer, or Bacillus cereus , biological inducer, before the pathogen arrival. Initially, bean plants were evaluated for induced resistance against Xanthomonas axonopodis pv. phaseoli when treated with the two inducers. In the absence of the pathogen, it was evaluated the physiological parameters respiration and photosynthesis and the activity of enzymes involved in the defense as peroxidase, chitinase, β-1,3-glucanase, phenylalanine ammonia-lyase and polifenoloxidase and activity of enzymes involved in the catabolism as proteases, and the synthesis of compounds of the secondary metabolism as phenols and lignin, and the synthesis of compounds of the primary metabolism as proteins and sugars. The growth of the plants was evaluated as well as their productivity and production parameters. Some quality parameters of the grains were also evaluated. The occurrence of the resistance induced in the bean plants against the pathogens was observed for the two inducers. However, for the ASM the resistance induced was associated to increases in peroxidase, chitinase and β-1,3-glucanase activities, increase in the protease activity, increase in lignin synthesis and reduction in the phenol content, increase in soluble proteins and sugar content in the leaves, reduction of the growth and productivity, increasing the protein and reducing the starch content of the grains. The B. cereus only increased peroxidase activity in a lower way and showed a tendency to increase protease activity, and to reduce the protein content in the leaves without interfering in the growth or in the productivity, but it reduced the protein content and it increased the starch content of the grains. Therefore, the biotic inducer, B. cereus altered a minimum the metabolism of the bean plant, without interfering in the productivity and improving the quality of the production, while the abiotic inducer ASM altered its metabolism, generating a metabolic cost and consuming the plant photosyntathes to invest in defenses, causing a reduction in the productivity.

This thesis is about Photovoltaic (PV) cells and its stresses in various directions by calculating the power generated using solar cells under different conditions to improve its efficiency. Our research studies found that using multi-junction cells with larger substrates can increase the efficiency to some extent which in practice is limited to 43 percent. The experiment was conducted using ten solar cells each with an area of 20.9〖cm〗 ^2, where each cell gives 0.5 V and 0.4 A and a 1.25 Ω resistor was used. The cells were connected in series. Once, the PV cells were fixed horizontally and the other time tested in tilted position under same outdoor condition. The purpose of testing PV cells was to investigate the efficiency under above mentioned conditions. The data collected from the readings was used in calculation, and we have obtained from the calculations that horizontally fixed cells gave 4.8 percent efficiency whereas tilted cells gave 6.6 percent efficiency. Hence, the ratio showed that fixed cells produced 37.5 percent more power compared to horizontally fixed cells. Our other experiment consisted of testing PV cells under different temperature conditions that was done using a freezer and an oven for temperature variation and a tungsten bulb was used as a light source. The purpose of performing this experiment was to investigate how the efficiency of PV cells is affected under extreme conditions. Part of our thesis was also including studies and analysis of produced energy by the solar panel installed on the roof of “BTH” building in Karlskrona, Sweden. The data consisted of energy produced from February up to August 2014. The investigation also included finding the highest produced energy during these months. We have found that the highest energy was generated on the 1st of July which was 12.86 kWh. Furthermore, we went deep into investigation of the 1st of July to know exactly which hour of that day the highest energy was produced. The data showed that the highest produced energy was at 12:19 and 13:19 which was 2.03 kWh. / Ramzi: +46723231353, +966561993488 Zain:

The effect of rotation on the stability of multiple jets in planetary atmospheres is system- atically investigated. Typically in Jovian planetary atmospheres, multiple zonal jets have been observed and their morphology has been systematically studied. The formation of jets has always been viewed as a nonlinear problem where most work has followed from the ideas of potential vorticity (PV) homogenization or turbulent mixing on a β-plane. In our present work, we have aimed to look at the linear stability of multiple jets in a geophysical fluid, and hope to add further insight into the observed jet profiles in β-plane turbulence. In addition, we also study the evolution and life-cycle of these jets as they interact with each other in a non linear fashion. We begin with the linear stability of the \Bickley jet" using the linearized shallow water quasigeostrophic (QG) equations. We have included a finite deformation radius in our calculations to partially mimic the effects of compressibility. A family of synthetically generated velocity profiles with east-west jets are then studied. In particular, a variety of flow configurations with two jets have been considered with a parameter sweep across jet separation, relative jet strength and thickness. As a broad observation, it is noted that an asymmetric east-west jet profile with a stronger and sharper eastward jet is the most stable of all the profiles considered, and a finite deformation radius further stabilizes such profiles. More realistic jet profiles have also been considered and the role of a finite deformation radius in stabilizing such jets is elucidated. We also examined the nonlinear evolution of multiple jets in a periodic domain and in a channel geometry, as we undertake freely decaying long time simulations of the governing QG equation. As per the \Selective Decay" principle we observe that arbitrary initial conditions approach the flow configuration of the prescribed \suitable end states". In addition, we have shown how a finite deformation length scale modifies these \suitable end states". As a broad observation, we have noted that a linearly unstable jet flow configuration, in the presence of β, breaks down into turbulence and reforms into a more asymmetric jet profile with a stronger and sharper eastward jet. The inclusion of a finite deformation length scale in our calculations, is observed to suppress such jet formation. Similar numerical experiments have been performed in a channel and the results have been compared. Chiefly, for the end states, the nature of the observed jet asymmetry is reversed, i.e., the westward jets are observed to be stronger in a channel.

La lumière du soleil est un bon candidat comme source propre et abondante d'énergie renouvelable. Cette source d'énergie écocompatible peut être exploitée pour répondre aux besoins croissants en énergie du monde. Plusieurs générations de cellules photovoltaïques ont été utilisées pour convertir directement la lumière solaire en énergie électrique. La troisième génération de type multijonction des cellules photovoltaïques est caractérisée par un niveau d'efficacité plus élevé que celui de tous les autres types de cellules photovoltaïques. Des dispositifs optiques, tels que des concentrateurs optiques, des séparateurs optiques et des dispositifs optiques réalisant simultanément la séparation du spectre et la concentration du faisceau ont été utilisés dans des systèmes de cellules solaires. Récemment, les Eléments Optiques Diffractifs (EOD) font l'objet d'un intérêt soutenu en vue de leur utilisation dans la conception de systèmes optiques appliqués aux cellules photovoltaïques. Cette thèse est consacrée à la conception d'un EOD qui peut réaliser simultanément la séparation du spectre et la concentration du faisceau pour des cellules photovoltaïques de type multijonction latéral ou similaire. Les EOD qui ont été conçus ont une structure sous-longueur d'onde et fonctionnent en espace lointain pour implanter la double fonction séparation du spectre et concentration du faisceau. Pour cette raison, des outils de simulation ont été développés pour simuler le comportement du champ magnétique à l'intérieur de l'EOD à structure sous-longueur d'onde. De plus, un propagateur hybride rigoureux a aussi été développé, il est basé sur les deux théories de la diffraction, à savoir la théorie scalaire et la théorie rigoureuse. La méthode FDTD (Finite Difference Time Domain) ou méthode de différences finies dans le domaine temporel a été utilisée pour modéliser la propagation du champ magnétique en champ proche c'est-à-dire à l'intérieur et autour de l'EOD. La méthode ASM (Angular Spectrum Method) ou méthode à spectre angulaire a été utilisée pour modéliser de façon rigoureuse la propagation libre en champ lointain. Deux EOD différents ont été développés permettant d'implanter les fonctions souhaitées (séparation du spectre et concentration du faisceau) ; il s'agit d'une part d'un composant diffractif intitulé G-Fresnel (Grating and Fresnel lens) qui combine un réseau avec une lentille de Fresnel et d'autre part d'une lentille hors-axe. Les composants proposés réalisent la séparation du spectre en deux bandes pour une plage visible-proche infrarouge du spectre solaire. Ces deux bandes peuvent être absorbées et converties en énergie électrique par deux cellules photovoltaïques différentes et disposées latéralement par rapport à l'axe du système. Ces dispositifs permettent d'obtenir un faible facteur de concentration et une efficacité de diffraction théorique d'environ 70 % pour les deux bandes séparées. Grâce à une distance de focalisation faible, ces composants peuvent être intégrés dans des systèmes compacts de cellules solaires. La validation expérimentale du prototype fabriqué montre une bonne correspondance entre les performances expérimentales et le modèle théorique / Sunlight represents a good candidate for an abundant and clean source of renewable energy. This environmentally friendly energy source can be exploited to provide an answer to the increasing requirement of energy from the world. Several generations of photovoltaic cells have been successively used to convert sunlight directly into electrical energy. Third generation multijunction PV cells are characterized by the highest level of efficiency between all types of PV cells. Optical devices have been used in solar cell systems such as optical concentrators, optical splitters, and hybrid optical devices that achieve Spectrum Splitting and Beam Concentration (SSBC) simultaneously. Recently, diffractive optical elements (DOE’s) have attracted more attention for their smart use it in the design of optical devices for PV cells applications.This thesis was allocated to design a DOE that can achieve the SSBC functions for the benefit of the lateral multijunction PV cells or similar. The desired design DOE's have a subwavelength structure and operate in the far field to implement the target functions (i.e. SSBC). Therefore, some modelling tools have been developed which can be used to simulate the electromagnetic field behavior inside a specific DOE structure, in the range of subwavelength features. Furthermore, a rigorous hybrid propagator is developed that is based on both major diffraction theories (i.e. rigorous and scalar diffraction theory). The FDTD method was used to model the propagation of the electromagnetic field in the near field, i.e. inside and around a DOE, and the ASM method was used to model rigorously propagation in the free space far field.The proposed device required to implement the intended functions is based on two different DOE’s components; a G-Fresnel (i.e. Grating and Fresnel lens), and an off-axis lens. The proposed devices achieve the spectrum splitting for a Vis-NIR range of the solar spectrum into two bands. These two bands can be absorbed and converted into electrical energy by two different PV cells, which are laterally arranged. These devices are able to implement a low concentration factor of “concentrator PV cell systems”. These devices also allow achieving theoretically around 70 % of optical diffraction efficiency for the both separated bands. The impact distance is very small for the devices proposed, which allows the possibility to integrate these devices into compact solar cell systems. The experimental validation of the fabricated prototype appears to provide a good matching of the experimental performance with the theoretical model.