This thesis studies residential dc distribution system with primary focus on point-of-load (POL) converters. The growing number of inherently dc loads, increasing penetration of distributed energy resources (DERs) and advancements in power electronic converters are some of the reasons to reconsider the existing residential ac distribution system. A dc distribution system can achieve higher efficiency by eliminating the ac-dc rectifiers and power factor correction stages currently used in most domestic electronic appliances. In this thesis, 380V is identified as a suitable voltage level for the main dc bus. Safety issues are discussed and common domestic loads are characterized. Two common converter topologies – buck and flyback converters are suggested as POL converters for heating and LED lighting loads respectively. State-feedback control is designed and implemented for buck converter and current mode control of flyback converter is implemented. A 500W POL buck converter using state-feedback with integral control is designed and tested for heating load applications. Finally a small dc distribution system is simulated using the converter models. The response of the system is stable under load and line changes. / text

This thesis presents a novel Zero Voltage Switching (ZVS) approach in a grid connected single-stage flyback inverter without using any additional auxiliary circuits. The soft-switching of the primary switch is achieved by allowing negative current from the grid-side through bidirectional switches placed on the secondary side of the transformer. Basically, the negative current discharges the MOSFET’s output capacitor thereby allowing turn-on of the primary switch under zero voltage. In order to optimize the amount of reactive current required to achieve ZVS a variable frequency control scheme is implemented over the line cycle. In addition, the bi-directional switches on the secondary side of the transformer have ZVS during the turn-on times. Therefore, the switching losses of the bi-directional switches are negligible. A 250W prototype has been implemented in order to validate the proposed scheme. Experimental results confirm the feasibility and superior performance of the converter compared to the conventional flyback inverter. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2012-07-06 16:24:13.385

Η παρούσα διπλωματική εργασία ασχολείται με τη μελέτη και την κατασκευή μιας νέας τοπολογίας για τη διασύνδεση ενός φωτοβολταϊκού πλαισίου με το δίκτυο χαμηλής τάσης. Η διάταξη που επιλέχτηκε αποτελεί το πρώτο στάδιο ενός μετατροπέα δύο βαθμίδων που χρησιμοποιείται για την αντιστροφή της τάσης του φωτοβολταϊκού πλαισίου και τη σύνδεση αυτού με το δίκτυο. Η βασική λειτουργία της διάταξης είναι η ανύψωση και σταθεροποίηση της τάσης εισόδου στα επίπεδα των 400 V. Η επιλογή της τοπολογίας στηρίχτηκε στον απλό σχεδιασμό, το υψηλό κέρδος τάσης και την ύπαρξη ενός μόνο διακοπτικού στοιχείου. Το κύκλωμα που μελετήθηκε είναι ένας μετατροπέας Boost σε συνδυασμό με ένα μετατροπέα Flyback με δυο δευτερεύοντα τυλίγματα. Πιο συγκεκριμένα, το πηνίο του μετατροπέα Boost αντικαθίσταται από το πρωτεύον τύλιγμα του Μ/Σ Flyback, ενώ τα δύο δευτερεύοντα μεταφέρουν τη μαγνητική ενέργεια στην έξοδο με σκοπό την επιπλέον ενίσχυση της τάσης εξόδου που προσφέρει ο Boost. Η κατασκευή του μετατροπέα και του κυκλώματος ελέγχου πραγματοποιήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας. Τα πειραματικά αποτελέσματα επιβεβαίωσαν τη θεωρητική ανάλυση που έγινε και την ορθή λειτουργία του κυκλώματός μας. Ο μετατροπέας επιτυγχάνει υψηλά κέρδη τάσης (μέχρι και 20 φορές), ενώ ο βαθμός απόδοσης κρίνεται αρκετά ικανοποιητικός για επίπεδα ισχύος μέχρι 150 W, αφού μετρήθηκε πάνω από 85%. Ως προέκταση της κατασκευής, θα μπορούσε να υλοποιηθεί βρόχος ανάδρασης με σκοπό τη σταθεροποίηση της τάσης εξόδου στα 400 V καθώς και M.P.P.T. έλεγχος για τη βέλτιστης λειτουργίας της Φ/Β γεννήτριας εισόδου. / --

Orientador: Jose Antenor Pomilio / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T08:24:07Z (GMT). No. of bitstreams: 1 Ortenzi_Gustavo_M.pdf: 4885292 bytes, checksum: 8a23d8845eaad19c72fe6f84e13af963 (MD5) Previous issue date: 2009 / Resumo: Descreve-se neste trabalho o desenvolvimento de uma fonte de alimentação chaveada para utilização em eletrodomésticos, capaz de entregar três saídas com níveis de tensão e potência diferentes, com uma mínima troca de componentes entre as três versões. Na primeira parte do trabalho é apresentada a aplicação da fonte e suas necessidades, seguido das especificações e da escolha da topologia e do modo de operação. Dando continuidade no desenvolvimento do projeto da fonte, apresenta-se a metodologia de cálculo adotada para o dimensionamento dos componentes a serem utilizados. Uma vez com os componentes dimensionados, apresenta-se a seleção dos componentes visando a estratégia de escalabilidade. Finalizando o dimensionamento dos componentes, apresenta-se o esquemático da fonte de alimentação e os componentes que são modificados de acordo com a versão em questão. A seguir, apresentam-se os resultados obtidos dos testes de regulação cruzada das saídas, as principais formas de onda de corrente e tensão do conversor, o rendimento das três versões considerando diferentes tensões de entrada de rede e a resposta a transiente. Fechando os resultados práticos, apresentam-se os ensaios de desenvolvimento de EMC/EMI, mostrando os resultados iniciais, as modificações implementadas e as soluções adotadas. No último capítulo apresenta-se as conclusões e as perspectivas de continuidade de desenvolvimento deste trabalho. / Abstract: This work describes the development of a switch mode power supply to be used at home appliances, capable to deliver three outputs with voltage and power different levels, changing a minimum number of components between them. At the first part of the work is presented the application of the power supply and its needs, followed by the specifications and choose of the topology and the operation mode. Continuing the design of the power supply's project, it is presented the methodology adopted to calculate and select the components to be used. With the components selected, it is presented the components selection criteria looking the scalability strategy. Ending the component's calculation and selection, the power supply schematic and the components that change according to the used version are shown. After the design, experimental results of the output cross regulation, main waveforms of voltage and current, efficiency and transient response of the three versions considering different AC Mains voltages are shown. Closing the experimental results, the EMI/EMC tests are presented, presenting the preliminary results, followed by the adopted modifications and solutions. The last chapter presents the conclusions and the perspectives of new developments of this work. / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

A DC to AC inverter can be classified in different topologies; some of these topologies are three level and multilevel inverter. Both types have some advantages and disadvantages. Three level inverters can be applied for low power applications because it is cheaper and has less semiconductor losses at high switching frequencies with poor total harmonic distortion (THD). Multilevel inverters (MLI) can be applied for higher power applications with less THD. However, the MLI has more cost and conductive power losses in comparison with three level inverters. In order to overcome the limitations of three and multilevel topologies, this thesis presents a new controlling topology of multilevel DC/AC inverters. The proposed multilevel inverter topology is based on a current source inverter, which consists of a buck/boost, boost and flyback converters, and an H-bridge inverter. The output voltage of the inverter is shaped through the control of just one main semiconductor switch. This new topology offers almost step-less output voltage without the need for multi DC source or several capacitor banks as in the case of other multilevel inverter topologies. The efficiency of the proposed topology is higher than other inverter topologies for medium power applications (2-10 kW). The proposed topology also generates smaller Total Harmonic Distortion (THD) compared to other inverter topologies. The two main key aspects of the proposed circuit is to keep the switching losses as low as possible and this is achieved through the control of a single switch at relatively low frequency and also to generate an improved AC Voltage waveform without the need for any filtering devices. The output frequency and voltage of the proposed circuit can be easily controlled according to the load requirements. The proposed inverter topology is ideal for the connection of renewable energy; this is due to its flexibility in varying its output voltage without the need of fixed turns-ratio transformers used in existing DC/AC inverter topologies. The harmonic contents of the output of this proposed topology can be controlled without the need of any filter. The simulation and practical implementation of the proposed circuits are presented. The practical and simulation results show excellent correlation.

The DC House project relies primarily on renewable energy sources to provide DC power to the various loads of the house. However, not all renewable sources are capable of providing power at all times of the day. A back-up energy source in the form of a battery storage system must be available to meet the electrical needs of the house. A bi-directional flyback power converter was initially designed to allow a battery to charge from as well as discharge to the 48V bus line of the DC House. The design provided a 35W prototype to demonstrate the converter’s feasibility. Further improvements to increase power output through changes in design as well as improving the control scheme of the bi-directional converter were conducted. Results allowed an increase of output power to 48W with efficiency at 82% for both charging and discharging. The improvements to the control scheme allowed for better management of charging and discharging cycles of the battery.

The thesis deals with the design and construction of a switching power supply with output voltage adjustable from 0 to 1200 V and rated power of 120 W, which will be used to replace the existing high voltage power supply for the irreversible electroporation (IRE) device developed at UVEE FEEC BUT. The thesis focuses on a basic description of the IRE device, a description of usable converter topologies and a selection of the best topology for the required purpose. The selection of the control circuit concept and its design are also integral parts of the thesis. The final part of the thesis contains the assembly of the power supply and the measurement verifying its function.

The aim of this thesis is to design a step-up DC/AC converter, an inverter from 12 V to 120 Vrms, with a sinus output signal. The converter should deliver a continuous performance of 300 W and a double peak power output of 600 W. The supposed usage of this inverter would be as a back-up power source for the circulatory pump of the central heating in the case of power outage. The inverter is consisting of a T-type power section.

Theoretical part of this thesis describes LEDs and other circuitry used for LED light design. LED light is designed, manufactured and put into operation. This thesis examines possibilities of measuring exterior light and its key parameters. The device uses two sets of LEDs – warm white and cold white to create light with parameters dependent on exterior light. LEDs are driven by constant current sources that are designed, manufactured and examined in this thesis. The device is microprocessor-controlled, which allows to switch between multiple modes of operation. Flyback SMPS is used to power the microcontroller.

This master's thesis describes the development of switching power supply with planar transformer. Deals with selection of a suitable integrated circuit together with the topology, a purchase of prototype for the reference measurements and debugging its own power supply. Further design and implementation of planar transformer and in the final implementation, debugging, and measurment's its own prototype. Power supply was fully functional and reached the expected parameters.