A novel single phase rectification technique with a new architecture and control scheme is proposed. The new rectifier consists of switched capacitor branch in parallel with the diode bridge rectifier. The switched capacitor branch includes a capacitor and a bidirectional switch arranged in series so the switch can control the charging and discharging of the capacitor. The control strategy is carefully designed to ensure the output voltage of the rectifier is above a chosen threshold level and to maintain high input power factor with reduced line current harmonics. Circuit configuration, design parameters, principles of operation and the mathematical analysis are presented. The new architecture provides a reduction in the size of the DC side capacitor. This reduction can be as low as less than 10% of the size of the typical smoothing capacitor in the conventional single phase rectifier. The proposed concept is verified by the experimental results over a range of case studies. A novel buck-boost DC-DC converter architecture is also proposed. This converter utilises the close inversely-coupled inductors topology in both its conversion stages (buck and boost). The new converter aims to reduce the switching noise that usually accompanies the buck and boost circuits. This can be done by maintaining a continuous flow of current in both converter stages which results in a large reduction in the back e.m.f induced in the main inductor and thus reduces the switching noise. The new converter architecture also provides a unique design of the passive clamped circuit. This circuit is used to recycle the leakage energies of the coupled inductors which results in an efficiency improvement of the converter and to limit the voltage stress on the power switches. Circuit con figuration, principles of operation and the transfer function are presented. The proposed concept is verified by the experimental and the simulated results of a range of case studies. The highest achieved efficiency observed in the experiments was 97:7%.

Κατά τη μελέτη ηλεκτρικών μεγεθών υπό μη ημιτονοειδείς συνθήκες ιδιαίτερο αντικείμενο μελέτης αποτελούν τα φαινόμενα που σχετίζονται με την ισχύ. Οι γνωστές προσεγγίσεις για την ισχύ σε ημιτονοειδείς καταστάσεις δεν επαρκούν και είναι εσφαλμένες. Η παρουσία ανώτερων αρμονικών, καθώς και επίσης η ασυμμετρία τάσεων και ρευμάτων μας οδηγούν σε μία διαφορετική προσέγγιση της ηλεκτρικής ισχύος. Είναι φανερό λοιπόν γιατί έχει προκύψει η ανάγκη να ορισθούν ορθά οι συνιστώσες ισχύος ώστε να: 1) Περιγράψουμε τα φυσικά φαινόμενα ισχύος και τις ιδιότητες των κυκλωμάτων παρουσία αρμονικών 2) Αντισταθμίσουμε κάποιες συνιστώσες ώστε να επιτύχουμε διόρθωση του συντελεστή ισχύος 3) Μετρηθούν κάποιες ποσότητες για τη διαμόρφωση κατάλληλου τιμολογίου ηλεκτρικής ενέργειας 4) Καθορισθούν δείκτες για την επίπτωση αρμονικών στον εξοπλισμό Η παρούσα διπλωματική εργασία ασχολείται με τα άνωθεν και περιλαμβάνει τα ακόλουθα κεφάλαια: Το κεφάλαιο 1 αποτελεί μια γενική εισαγωγή του θέματος που πραγματεύεται η παρούσα διπλωματική εργασία Το κεφάλαιο 2 ασχολείται με τη παρουσία αρμονικών στα συστήματα ηλεκτρικής ενέργειας Το κεφάλαιο 3 και 4 ασχολείται με την ισχύ σε ημιτονοειδή και μη ημιτονοειδή μονοφασικά κυκλώματα αντιστοίχως Τα κεφάλαια 5 έως 10 παρουσιάζουν τις κυριότερες θεωρίες ισχύος σε μονοφασικά συστήματα παρουσία αρμονικών Συγκεκριμένα, το κεφάλαιο 5 ασχολείται με τη μέθοδο BUDEANU, το κεφάλαιο 6 με τη μέθοδο FRYZE, το κεφάλαιο 7 με τη μέθοδο SHEPHERD-ZAKIKHANI, το κεφάλαιο 8 με τη μέθοδο CZARNECKI, το κεφάλαιο 9 με τη μέθοδο IEEE και τέλος το κεφάλαιο 10 με τη μέθοδο της ΓΕΩΜΕΤΡΙΚΗΣ ΑΛΓΕΒΡΑΣ Τέλος, το κεφάλαιο 11 παρουσιάζει τα συμπεράσματα που προκύπτουν από τη παρούσα διπλωματική εργασία / When studying electrical quantities under nonsinusoidal conditions are particularly studied the phenomena related to the force. Major approaches to power in sinusoidal conditions are inadequate and incorrect. The presence of higher harmonics and also the asymmetry of voltages and currents lead us to a different approach of power. It is obvious, then, why the need has arisen to define correctly the power components to: 1) Describe physical phenomena and power properties of circuits in the presence of harmonics 2) Offsetting components to achieve power factor correction 3) Measure some quantities to formulate appropriate energy tariff 4) Determine the impact indicators for harmonic equipment This thesis addresses the above and includes the following chapters: Chapter 1 provides a general introduction to the topic discussed in this thesis Chapter 2 deals with the presence of harmonics in power systems Chapter 3 and 4 deal with the power in sinusoidal and non-sinusoidal single-phase circuits respectively Chapters 5 to 10 are the main theories of power in single-phase systems in the presence of harmonics Specifically, Chapter 5 deals with the method BUDEANU, Chapter 6 deals with the method FRYZE, chapter 7 deals with SHEPHERD-ZAKIKHANI, Chapter 8 deals with method CZARNECKI, Chapter 9 deals with method IEEE and finally Chapter 10 deals with method of GEOMETRIC ALGEVRA Finally, Chapter 11 presents the conclusions from this thesis

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho apresenta o estudo, desenvolvimento e aplicação de novas técnicas de controle aos sistemas de geração de energia fotovoltaica, conectados à rede elétrica monofásica, visando a melhoria da eficiência destes sistemas em relação aos métodos de controle tipicamente utilizados. O trabalho é dividido em duas partes principais, as quais estão relacionadas ao rastreamento do ponto de máxima potência (Maximum Power Point Tracking – MPPT) e, depois, ao controlador interno dos conversores boost-quadrático – lado dos painéis fotovoltaicos – assim como aos controladores do inversor de tensão, no lado da rede elétrica monofásica. A primeira parte do trabalho consiste no desenvolvimento de um algoritmo de meta heurística para o MPPT, o qual é baseado no método do recozimento simulado (Simulated Annealing - SA) e tem como objetivo a determinação do ponto de máximo global, buscando soluções fora de uma vizinhança próxima, de modo a evitar o atracamento em máximos locais da curva de potência de saída do arranjo de painéis fotovoltaicos, melhorando, assim, o aproveitamento da energia em situações de sombreamento parcial. A segunda parte do trabalho apresenta o projeto de controladores baseados no modelo interno (Internal Model Control – IMC) com 1 grau de liberdade (1 Degree of Freedom – 1 DOF) aplicados, primeiramente, ao conversor CC-CC Boost Quadrático, utilizado para o MPPT, e, posteriormente, a um inversor de tensão com filtro LCL, conectado à rede elétrica monofásica, operando no modo de injeção de corrente. É apresentada a modelagem matemática de ambos os conversores e analisada a compensação da realimentação interna ao sistema do inversor de tensão, correspondente ao desacoplamento da tensão da rede, através da estratégia de alimentação à frente (Feedforward). Visando-se uma base de comparação, para a análise de desempenho do conversor IMC – 1DOF, também é aplicado ao sistema de injeção de corrente, o controlador Proporcional-Ressonante (P+Res). São apresentados resultados de simulação computacional e experimentais de ambos os 8 controladores, os quais permitem verificar o desempenho do sistema em situação de rede fraca e carga local não-linear. / This paper presents the study, development and application of new control techniques for photovoltaic power generation systems, connected to single-phase power grid in order to improve the efficiency of these systems in relation to control methods typically used. The work is divided into two main parts, which are related to tracking the maximum power point (Maximum Power Point Tracking - MPPT) and then the internal controller of boost quadratic converters - side of the photovoltaic panels - as well as the controllers the voltage inverter, the side of the single-phase mains. The first part of the work is the development of a heuristic goal algorithm for MPPT, which is based on the method of simulated annealing (Simulated Annealing - SA) and aims at determining the overall maximum point, seeking out solutions in a close vicinity, so as to prevent the docking local maxima in the curve of power output of the photovoltaic array, thereby improving the utilization of energy in partial shading situations. The second part presents the design of controllers based on internal model (Internal Model Control - IMC) with 1 degree of freedom (1 Degree of Freedom - 1 DOF) applied, first, the DC-DC Boost Quadratic converter, used for MPPT, and thereafter, a voltage inverter with LCL filter connected to the single phase power supply operating in current injection mode. A mathematical modeling of both converters and analyzed the compensation of internal feedback to the voltage inverter system corresponding to the disconnection of the mains voltage through the power strategy a head (feedforward). A basis of comparison for the performance analysis of IMC-1DOF converter is aiming at, is also applied to the current injection system, Proportional-Resonant Controller (P + Res). They are presented computer simulation and experimental results of both controllers, which allow you to check the system performance in low and non-linear local load network situation. / Tese (Doutorado)