High gain non-isolated DC-DC converter topologies for energy conversion systems

PhD ThesisEmerging applications driven by low voltage level power sources, such as photovoltaics, batteries and fuel cells require static power converters for appropriate energy conversion and conditioning to supply the requirements of the load system. Increasingly, for applications such as grid connected inverters, uninterruptible power supplies (UPS), and electric vehicles (EV), the performance of a high efficiency high static gain power converter is of critical importance to the overall system. Theoretically, the conventional boost and buck-boost converters are the simplest non-isolated topologies for voltage step-up. However, these converters typically operate under extreme duty ratio, and severe output diode reverse recovery related losses to achieve high voltage gain. This thesis presents derivation, analysis and design issues of advanced high step-up topologies with coupled inductor and voltage gain extension cell. The proposed innovative solution can achieve significant performance improvement compared to the recently proposed state of the art topologies. Two unique topologies employing coupled inductor and voltage gain extension cell are proposed. Power converters utilising coupled inductors traditionally require a clamp circuit to limit the switch voltage excursion. Firstly, a simple low-cost, high step-up converters employing active and passive clamp scheme is proposed. Performance comparison of the clamps circuits shows that the active clamp solution can achieve higher efficiency over the passive solution. Secondly, the primary detriment of increasing the power level of a coupled inductor based converters is high current ripple due to coupled inductor operation. It is normal to interleaved DC-DC converters to share the input current, minimize the current ripple and increase the power density. This thesis presents an input parallel output series converter integrating coupled inductors and switched capacitor demonstrating high static gain. Steady state analysis of the converter is presented to determine the power flow equations. Dynamic analysis is performed to design a closed loop controller to regulate the output voltage of the interleaved converter. The design procedure of the high step-up converters is explained, simulation and experimental results of the laboratory prototypes are presented. The experimental results obtained via a 250 W single phase converter and that of a 500 W interleaved converter prototypes; validate both the theory and operational characteristics of each power converter.Petroleum Technology Development Fund (PTDF) Nigeri

Design and implementation of multi-port DC-DC converters for electrical power systems

The thesis proposes developing, analysing, and verifying these DC-DC converters to improve the current state-of-the-art topology. Four new DC-DC converters for applications like light emitting diode, lighting microgrids DC, PV applications, and electric vehicles are as follows. In this study, the two-input converter is presented. The two-input converter that has been proposed serves as the interface between the two input sources and load. Using two switches and two diodes, the proposed converter minimises switching losses and contains eight components in total, making it compact and low volume. As a result, the highest average efficiency is 92.5%, and the lowest is 89.6%. In this research, the new three-port converter that has been proposed serves as the interface between the input source, a battery, and a load. In addition, the converter is suitable for use in standalone systems or satellite applications. A low-volume converter is designed with three switches and two diodes, thereby minimizing switching losses and ten components in total. Regarding efficiency, the highest average is 92.5%, and the lowest is 90.9%. Also, this study proposes a single-switch high-step-up converter for LED drivers and PV applications. A further benefit of the proposed converter over conventional classical converters is that it utilises only one active switch. These results align with simulation results, and its gain is 6.8 times greater than classical converters. Furthermore, stress across switches and diodes is smaller than the output voltage, approximately 50%. Semiconductor losses were limited with a low duty cycle of 0.7. This makes the highest average efficiency 95% and the lowest 93.9%. The new four-port converter is presented for applications such as microgrid structures and electric vehicles. As part of the integrated converter, two or three converters are combined by sharing some components, such as switches, inductors, and capacitors, to form a single integrated converter. As a result of the four-port converter proposed, battery power can be managed, and output voltage can be regulated simultaneously

Estudo de estruturas de reatores eletrônicos para LEDs de iluminação

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2010.Este trabalho tem como objetivo específico estudar estruturas de reatores eletrônicos para LEDs de iluminação. Primeiramente são avaliadas as propriedades elétricas, ópticas e térmicas dos LEDs de potência. É apresentado um modelo elétrico simplificado para simulação e considerada a influência da temperatura da junção nos LEDs, nas suas características ópticas e elétricas. Também é proposto um método de estimação da temperatura da junção para os LEDs de potência. A seguir, são analisadas as características necessárias para as fontes de alimentação dos LEDs de potência, e a influência do tipo de modulação utilizada para modificar a sua intensidade luminosa. São propostos conversores CC-CC auto-oscilantes para os LEDs de potência e uma técnica para equalização de corrente em vetores de LEDs. A aplicabilidade dos conversores CC-CC básicos também é analisada. Além disso, é avaliada a aplicação dos conversores série ressonantes nos LEDs de potência. O modelo elétrico simplificado foi utilizado para a análise e para o dimensionamento do conversor série ressonante. Também é ponderada a inserção de um capacitor de filtro em paralelo com os LEDs, bem como a operação do conversor sem o capacitor eletrolítico do barramento de corrente contínua. Os conversores série ressonantes auto-oscilantes e a integração de estágios para correção do fator de potência são avaliados. Resultados experimentais dos protótipos são obtidos, analisados e discutidos para validação das metodologias aplicadas.This work aims to study specific topologies of electronic drives for lighting LEDs. Firstly it is considered the electrical, optical and thermal properties, of power LEDs. Following, it is presented a simplified LED electrical model for simulation, and it is analyzed the influence of the LED junction temperature in its optical and electrical characteristics. It is also proposed a method for estimating junction temperature for power LEDs. In the sequence, the characteristics required to power supplies for LED, and the influence of the modulation strategy used to change the light intensity of power LEDs are analyzed. DC-DC self-oscillating converters for power LEDs are proposed. The applicability of basic DC-DC converters is analyzed. Moreover, the application of series resonant converters in power LEDs is presented. The simplified LED electric model was used for the analysis and for the design of series resonant converters. It is also analyzed the insertion of a filter capacitor in parallel with the LEDs, as well as the converter operation without the DC bus electrolytic capacitor. The self-oscillating series resonant converters and integration stages for power factor correction are analyzed. Experimental results of the prototypes are obtained, analyzed and discussed to validate the proposed methodologies

Power Quality

Electrical power is becoming one of the most dominant factors in our society. Power generation, transmission, distribution and usage are undergoing signifi cant changes that will aff ect the electrical quality and performance needs of our 21st century industry. One major aspect of electrical power is its quality and stability – or so called Power Quality. The view on Power Quality did change over the past few years. It seems that Power Quality is becoming a more important term in the academic world dealing with electrical power, and it is becoming more visible in all areas of commerce and industry, because of the ever increasing industry automation using sensitive electrical equipment on one hand and due to the dramatic change of our global electrical infrastructure on the other. For the past century, grid stability was maintained with a limited amount of major generators that have a large amount of rotational inertia. And the rate of change of phase angle is slow. Unfortunately, this does not work anymore with renewable energy sources adding their share to the grid like wind turbines or PV modules. Although the basic idea to use renewable energies is great and will be our path into the next century, it comes with a curse for the power grid as power fl ow stability will suff er. It is not only the source side that is about to change. We have also seen signifi cant changes on the load side as well. Industry is using machines and electrical products such as AC drives or PLCs that are sensitive to the slightest change of power quality, and we at home use more and more electrical products with switching power supplies or starting to plug in our electric cars to charge batt eries. In addition, many of us have begun installing our own distributed generation systems on our rooft ops using the latest solar panels. So we did look for a way to address this severe impact on our distribution network. To match supply and demand, we are about to create a new, intelligent and self-healing electric power infrastructure. The Smart Grid. The basic idea is to maintain the necessary balance between generators and loads on a grid. In other words, to make sure we have a good grid balance at all times. But the key question that you should ask yourself is: Does it also improve Power Quality? Probably not! Further on, the way how Power Quality is measured is going to be changed. Traditionally, each country had its own Power Quality standards and defi ned its own power quality instrument requirements. But more and more international harmonization efforts can be seen. Such as IEC 61000-4-30, which is an excellent standard that ensures that all compliant power quality instruments, regardless of manufacturer, will produce of measurement instruments so that they can also be used in volume applications and even directly embedded into sensitive loads. But work still has to be done. We still use Power Quality standards that have been writt en decades ago and don’t match today’s technology any more, such as fl icker standards that use parameters that have been defi ned by the behavior of 60-watt incandescent light bulbs, which are becoming extinct. Almost all experts are in agreement - although we will see an improvement in metering and control of the power fl ow, Power Quality will suff er. This book will give an overview of how power quality might impact our lives today and tomorrow, introduce new ways to monitor power quality and inform us about interesting possibilities to mitigate power quality problems. Regardless of any enhancements of the power grid, “Power Quality is just compatibility” like my good old friend and teacher Alex McEachern used to say. Power Quality will always remain an economic compromise between supply and load. The power available on the grid must be suffi ciently clean for the loads to operate correctly, and the loads must be suffi ciently strong to tolerate normal disturbances on the grid

Design and Control of Power Converters 2019

In this book, 20 papers focused on different fields of power electronics are gathered. Approximately half of the papers are focused on different control issues and techniques, ranging from the computer-aided design of digital compensators to more specific approaches such as fuzzy or sliding control techniques. The rest of the papers are focused on the design of novel topologies. The fields in which these controls and topologies are applied are varied: MMCs, photovoltaic systems, supercapacitors and traction systems, LEDs, wireless power transfer, etc

Conversores CC-CC não-isolados com alta taxa de conversão baseados no empilhamento de topologias convencionais

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2020.Esta tese tem como objetivo contribuir no estudo de novas topologias de conversores CC-CC não-isolados abaixadores com alta taxa de conversão. As topologias propostas são geradas a partir do empilhamento de estruturas convencionais e podem ser empregadas em aplicações em que elevados níveis de tensão estão envolvidos. As principais características das topologias propostas são a possibilidade de modularidade da estrutura, balanceamento natural das tensões nos capacitores e reduzidos esforços de tensão nos dispositivos semicondutores, permitindo o uso de interruptores e diodos da baixa tensão. Os conversores propostos também podem ser utilizadas como barramento CC proporcionando um ou mais níveis de tensão de saída, onde diferentes cargas podem ser conectadas em um ou mais capacitores da pilha. Dois tipos de estruturas são estudadas neste trabalho: conversores CC-CC baseados no empilhamento de topologias não-isoladas convencionais e conversores CC-CC baseados no empilhamento de topologias isoladas. Uma análise teórica generalizada com ganho estático, esforços de tensão e corrente nos principais componentes, análise do fluxo de potência e rendimento é apresentada para todas as topologias propostas. Com o objetivo de avaliar o desempenho e validar a análise teórica generalizada, protótipos para os dois tipos de estruturas com 250 W e 4 kW de potência de saída e tensão de entrada de 1200 V foram construídos e testados experimentalmente. Os resultados experimentais obtidos corroboram com a análise teórica e demonstram a viabilidade dos conversores propostos.Abstract: This thesis aims to contribute to the study of new topologies of step-down nonisolated dc-dc converters with high conversion ratio. The proposed topologies are generatedfrom the stacking of conventional structures and they can be employed in applicationswhere high levels of voltage are involved. The main features of the proposed topologies arethe possibility of modularity, natural voltage balance across the capacitors and reducedvoltage stresses on the semiconductor devices, allowing the use of low voltage switchesand diodes. The proposed converters can also be used as dc bus, providing one or severaloutput voltage levels, where different loads can be connected to one or more capacitorsof the stack. Two types of structures are studied in this work: dc-dc converters based onstacking of conventional non-isolated topologies and dc-dc converters based on stackingof conventional isolated topologies. A generalized theoretical analysis with static gain,voltage and current stresses on the main components, power flow analysis and efficiency ispresented for all the proposed topologies. In order to evaluate performance and validatethe theoretical analysis, prototypes for the two types of structures with 250 W and 4kW of output power and 1200 V input voltage were built and tested experimentally. Theexperimental results obtained corroborate the theoretical analysis and they demonstratethe feasibility of the proposed converters