Fault Tolerant DC–DC Converters at Homes and Offices

The emergence of direct current (DC) microgrids within the context of residential buildings and offices brings in a whole new paradigm in energy distribution. As a result, a set of technical challenges arise, concerning the adoption of efficient, cost-effective, and reliable DC-compatible power conditioning solutions, suitable to interface DC microgrids and energy consuming elements. This thesis encompasses the development of DC–DC power conversion solutions, featuring improved availability and efficiency, suitable to meet the requirements of a comprehensive set of end-uses commonly found in homes and offices. Based on the energy consumption profiles and requirements of the typical elements found at homes and offices, three distinctive groups are established: light-emitting diode (LED) lighting, electric vehicle (EV) charging, and general appliances. For each group, a careful evaluation of the criteria to fulfil is performed, based on which at least one DC–DC power converter is selected and investigated. Totally, a set of five DC–DC converter topologies are addressed in this work, being specific aspects related to fault diagnosis and/or fault tolerance analysed with particular detail in two of them. Firstly, mathematical models are described for LED devices and EV batteries, for the development of a theoretical analysis of the systems’ operation through computational simulations. Based on a compilation of requirements to account for in each end-use (LED lighting, EV charging, and general appliances), brief design considerations are drawn for each converter topology, regarding their architecture and control strategy. Aiming a detailed understanding of the two DC–DC power conversion systems subjected to thorough evaluation in this work – interleaved boost converter and fault-tolerant single-inductor multiple-output (SIMO) converter – under both normal and abnormal conditions, the operation of the systems is evaluated in the presence of open-circuit (OC) faults. Parameters of interest are monitored and evaluated to understand how the failures impact the operation of the entire system. At this stage, valuable information is obtained for the development of fault diagnosis strategies. Taking profit of the data collected in the analysis, a novel fault diagnostic strategy is presented, targeting interleaved DC–DC boost converters for general appliances. Ease of implementation, fast diagnostic and robustness against false alarms distinguish the proposed approach over the state-of-the-art. Its effectiveness is confirmed through a set of operation scenarios, implemented in both simulation environment and experimental context. Finally, an extensive set of reconfiguration strategies is presented and evaluated, aiming to grant fault tolerance capability to the multiple DC–DC converter topologies under analysis. A hybrid reconfiguration approach is developed for the interleaved boost converter. It is demonstrated that the combination of reconfiguration strategies promotes remarkable improvements on the post-fault operation of the converter. In addition, an alternative SIMO converter architecture, featuring inherent tolerance against OC faults, is presented and described. To exploit the OC fault tolerance capability of the fault-tolerant SIMO converter, a converter topology targeted at residential LED lighting systems, two alternative reconfiguration strategies are presented and evaluated in detail. Results obtained from computational simulations and experimental tests confirm the effectiveness of the approaches. To further improve the fault-tolerant SIMO converter with regards to its robustness against sensor faults, while simplifying its hardware architecture, a sensorless current control strategy is presented. The proposed control strategy is evaluated resorting to computational simulations.O surgimento de micro-redes em corrente contínua (CC) em edifícios residenciais e de escritórios estabelece um novo paradigma no domínio da distribuição de energia. Como consequência disso, surge uma panóplia de desafios técnicos ligados à adopção de soluções de conversão de energia, compatíveis com CC, que demonstrem ser eficientes, rentáveis e fiáveis, capazes de estabelecer a interface entre micro-redes em CC e as cargas alimentadas por esse sistema de energia. Até aos dias de hoje, os conversores CC–CC têm vindo a ser maioritariamente utilizados em aplicações de nicho, que geralmente envolvem níveis de potência reduzidos. Porém, as perspectivas futuras apontam para a adopção, em larga escala, destas tecnologias de conversão de energia, também em equipamentos eléctricos residenciais e de escritórios. Tal como qualquer outra tecnologia de conversão electrónica de potência, os conversores CC–CC podem ver o seu funcionamento afectado por falhas que degradam o seu bom funcionamento, sendo que essas falhas acabam por afectar não apenas os conversores em si, mas também as cargas que alimentam, limitando assim o tempo de vida útil do conjunto conversor + carga. Desta forma, é fulcral localizar a origem da falha, para que possam ser adoptadas acções correctivas, capazes de limitar as consequências nefastas associadas à falha. Para responder a este desafio, esta tese contempla o desenvolvimento de soluções de conversão de energia CC–CC altamente eficientes e fiáveis, capazes de responder a requisitos impostos por um conjunto alargado de equipamentos frequentemente encontrados em habitações e escritórios. Com base nos perfis de consumo de energia eléctrica e nos requisitos impostos pelas cargas tipicamente utilizadas em habitações e escritórios, são estabelecidos três grupos distintos: iluminação através de díodos emissores de luz, carregamento de veículo eléctrico (VE) e aparelhos eléctricos em geral. Para cada grupo, é efectuada uma avaliação cuidadosa dos critérios a respeitar, sendo com base nesses critérios que será escolhida e investigada pelo menos uma topologia de conversor CC–CC. No total, são abordadas cinco topologias de conversores CC–CC distintas, sendo que os aspectos ligados ao diagnóstico de avarias e/ou tolerância a falhas são analisados com particular detalhe em duas dessas topologias. Inicialmente, são estabelecidos modelos matemáticos descritivos do comportamento das principais cargas consideradas no estudo – díodos emissores de luz e baterias de VEs – visando a análise teórica do funcionamento dos sistemas em estudo, suportada por simulações computacionais. Com base numa compilação de requisitos a ter em conta em cada aplicação – iluminação através de díodos emissores de luz, carregamento de veículo eléctrico (VE) e aparelhos eléctricos em geral – são estabelecidas considerações ligadas à escolha de cada topologia de conversor não isolado, no que respeita à sua arquitectura e estratégia de controlo. Visando o conhecimento aprofundado das duas topologias de conversor CC–CC alvo de particular enfoque neste trabalho – conversor entrelaçado elevador e conversor de entrada única e múltiplas saídas, tolerante a falhas – quer em funcionamento normal, quer em funcionamento em modo de falha, é avaliado o funcionamento de ambas as topologias na presença de falhas de circuito aberto nos semicondutores activos. Para o efeito, são monitorizados e analisados parâmetros úteis à percepção da forma como os modos de falha avaliados neste trabalho impactam o funcionamento de todo o sistema. Nesta fase, é obtida informação fundamental ao desenvolvimento de estratégias de diagnóstico de avarias, particularmente indicadas para avarias de circuito aberto nos semicondutores activos dos conversores em estudo. Com base na informação recolhida anteriormente, é apresentada uma nova estratégia de diagnóstico de avarias direccionada a conversores CC–CC elevadores entrelaçados utilizados em aparelhos eléctricos, em geral. Facilidade de implementação, rapidez e robustez contra falsos positivos são algumas das características que distinguem a estratégia proposta em relação ao estado da arte. A sua efectividade é confirmada com recurso a uma multiplicidade de cenários de funcionamento, implementados quer em ambiente de simulação, quer em contexto experimental. Por fim, é apresentada e avaliada uma gama alargada de estratégias de reconfiguração, que visam assegurar a tolerância a falhas das diversas topologias de conversores CC–CC em estudo. É desenvolvida uma estratégia de reconfiguração híbrida, direccionada ao conversor entrelaçado elevador, que combina múltiplas medidas de reconfiguração mais simples num único procedimento. Demonstra-se que a combinação de múltiplas estratégias de reconfiguração introduz melhorias substanciais no funcionamento do conversor ao longo do período pós-falha, ao mesmo tempo que assegura a manutenção da qualidade da energia à entrada e saída do conversor reconfigurado. Noutra frente, é apresentada e descrita uma arquitectura alternativa do conversor de entrada única e múltiplas saídas, com tolerância a falhas de circuito aberto. Através da configuração proposta, é possível manter o fornecimento de energia eléctrica a todas as saídas do conversor. Para tirar máximo proveito da tolerância a falhas do conversor de entrada única e múltiplas saídas, uma topologia de conversor indicada para sistemas residenciais de iluminação baseados em díodos emissores de luz, são apresentadas e avaliadas duas estratégias de reconfiguração do conversor, exclusivamente baseadas na adaptação do controlo aplicado ao conversor. Os resultados de simulação computacional e os resultados experimentais obtidos confirmam a efectividade das abordagens adoptadas, através da melhoria da qualidade da energia eléctrica fornecida às diversas saídas do conversor. São assim asseguradas condições essenciais ao funcionamento ininterrupto e estável dos sistemas de iluminação, já que a qualidade da energia eléctrica fornecida aos sistemas de iluminação tem impacto directo na qualidade da luz produzida. Por fim, e para aprimorar o conversor de entrada única e múltiplas saídas tolerante a falhas, no que respeita à sua robustez contra falhas em sensores, é apresentada uma estratégia de controlo de corrente que evita o recurso excessivo a sensores e, ao mesmo tempo, simplifica a estrutura de controlo do conversor. A estratégia apresentada é avaliada através de simulações computacionais. A abordagem apresentada assume vantagens em múltiplos domínios, sendo de destacar vantagens como a melhoria da fiabilidade de todo o sistema de iluminação (conversor + carga), os ganhos atingidos ao nível do rendimento, a redução do custo de implementação da solução, ou a simplificação da estrutura de controlo.This work was supported by the Portuguese Foundation for Science and Technology (FCT) under grant number SFRH/BD/131002/2017, co-funded by the Ministry of Science, Technology and Higher Education (MCTES), by the European Social Fund (FSE) through the ‘Programa Operacional Regional Centro’ (POR-Centro), and by the Human Capital Operational Programme (POCH)

Battery-sourced switched-inductor multiple-output CMOS power-supply systems

Wireless microsystems add intelligence to larger systems by sensing, processing and transmitting information which can ultimately save energy and resources. Each function has their own power profile and supply level to maximize performance and save energy since they are powered by a small battery. Also, due to its small size, the battery has limited energy and therefore the power-supply system cannot consume much power. Switched-inductor converters are efficient across wide operating conditions but one fundamental challenge is integration because miniaturized dc-dc converters cannot afford to accommodate more than one off-chip power inductor. The objective of this research is to explore, develop, analyze, prototype, test, and evaluate how one switched inductor can derive power from a small battery to supply, regulate, and respond to several independent outputs reliably and accurately. Managing and stabilizing the feedback loops that supply several outputs at different voltages under diverse and dynamic loading conditions with one CMOS chip and one inductor is also challenging. Plus, since a single inductor cannot supply all outputs at once, steady-state ripples and load dumps produce cross-regulation effects that are difficult to manage and suppress. Additionally, as the battery depletes the power-supply system must be able to regulate both buck and boost voltages. The presented system can efficiently generate buck and boost voltages with the fastest response time while having a low silicon area consumption per output in a low-cost technology which can reduce the overall size and cost of the system.Ph.D

An Analysis of Non-Isolated DC-DC Converter Topologies with Energy Transfer Media

As miniaturized mobile devices with various functionalities are highly desired, the current requirement for loading blocks is gradually increasing. Accordingly, the efficiency of the power converter that supports the current to the loading bocks is a critical specification to prolong the battery time. Unfortunately, when using a small inductor for the miniaturization of mobile devices, the efficiency of the power converter is limited due to a large parasitic DC resistance (R-DCR) of the inductor. To achieve high power efficiency, this paper proposes an energy transfer media (ETM) that can make a switched inductor capacitor (SIC) converter easier to design, maintaining the advantages of both a conventional switched capacitor (SC) converter and a switched inductive (SI) converter. This paper shows various examples of SIC converters as buck, boost, and buck-boost topologies by simply cascading the ETM with conventional non-isolated converter topologies without requiring a sophisticated controller. The topologies with the ETM offer a major advantage compared to the conventional topologies by reducing the inductor current, resulting in low conduction loss dissipated at R-DCR. Additionally, the proposed topologies have a secondary benefit of a small output voltage ripple owing to the continuous current delivered to the load. Extensions to a multi-phase converter and single-inductor multiple-output converter are also discussed. Furthermore, a detailed theoretical analysis of the total conduction loss and the inductor current reduction is presented. Finally, the proposed topologies were simulated in PSIM, and the simulation results are discussed and compared with conventional non-isolated converter topologies

Mixed-source charger-supply CMOS IC

The proposed research objective is to develop, test, and evaluate a mixer and charger-supply CMOS IC that derives and mixes energy and power from mixed sources to accurately supply a miniaturized system. Since the energy-dense source stores more energy than the power-dense source while the latter supplies more power than the former, the proposed research aims to develop an IC that automatically selects how much and from which source to draw power to maximize lifetime per unit volume. Today, the state of the art lacks the intelligence and capability to select the most appropriate source from which to extract power to supply the time-varying needs of a small system. As such, the underlying objective and benefit of this research is to reduce the size of a complete electronic system so that wireless sensors and biomedical implants, for example, as a whole, perform well, operate for extended periods, and integrate into tiny spaces.Ph.D

Design and analysis of a novel multi-input multi-output high voltage DC transformer model

a novel Multi-Input Multi-Output (MIMO) step-up DC transformer for applications in high voltage renewable energy sources is designed and presente

A Novel Boost Converter Based LED Driver Chip Targeting Mobile Applications

abstract: A novel integrated constant current LED driver design on a single chip is developed in this dissertation. The entire design consists of two sections. The first section is a DC-DC switching regulator (boost regulator) as the frontend power supply; the second section is the constant current LED driver system. In the first section, a pulse width modulated (PWM) peak current mode boost regulator is utilized. The overall boost regulator system and its related sub-cells are explained. Among them, an original error amplifier design, a current sensing circuit and slope compensation circuit are presented. In the second section – the focus of this dissertation – a highly accurate constant current LED driver system design is unveiled. The detailed description of this highly accurate LED driver system and its related sub-cells are presented. A hybrid PWM and linear current modulation scheme to adjust the LED driver output currents is explained. The novel design ideas to improve the LED current accuracy and channel-to-channel output current mismatch are also explained in detail. These ideas include a novel LED driver system architecture utilizing 1) a dynamic current mirror structure and 2) a closed loop structure to keep the feedback loop of the LED driver active all the time during both PWM on-duty and PWM off-duty periods. Inside the LED driver structure, the driving amplifier with a novel slew rate enhancement circuit to dramatically accelerate its response time is also presented.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Efficient power management circuits for energy harvesting applications

Low power IoT devices are growing in numbers and by 2020 there will be more than 25 Billion of those in areas such as wearables, smart homes, remote surveillance, transportation and industrial systems, including many others. Many IoT electronics either will operate from stand-alone energy supply (e.g., battery) or be self-powered by harvesting from ambient energy sources or have both options. Harvesting sustainable energy from ambient environment plays significant role in extending the operation lifetime of these devices and hence, lower the maintenance cost of the system, which in turn help make them integral to simpler systems. Both for battery-powered and harvesting capable systems, efficient power delivery unit remains an essential component for maximizing energy efficiency. The goal of this research is to investigate the challenges of energy delivery for low power electronics considering both energy harvesting as well as battery-powered conditions and to address those challenges. Different challenges of energy harvesting from low voltage energy sources based on the limitations of the sources, the type of the regulator used and the pattern of the load demands have been investigated. Different aspects of the each challenges are further investigated to seek optimized solutions for both load specific and generalized applications. A voltage boost mechanism is chosen as the primary mechanism to investigate and to addressing those challenges, befitting the need for low power applications which often rely on battery voltage or on low voltage energy harvesting sources. Additionally, a multiple output buck regulator is also discussed. The challenges analyzed include very low voltage start up issues for an inductive boost regulator, cascading of boost regulator stages, and reduction of the number of external component through reusing those. Design techniques for very high conversion ratio, bias current reduction with autonomous bias gating, battery-less cold start, component and power stage multiplexing for reconfigurable and multi-domain regulators are presented. Measurement results from several silicon prototypes are also presented.Ph.D

Multiport Converter Topologies for Distributed Energy System Applications

In the midst of a present-day global energy renaissance, power electronics has evolved into a top-tier technology discriminator in distributed energy resource (DER) systems. Faced with the formidable task of integrating various types of DER technologies into singular systems, there is a growing appetite for multiport converter (MPC) design. In response, three unique DER MPC topologies are presented: the power sharing converter (PSC), the multi-level nine switch converter (ML9SC), and the modular fuel cell hybrid energy storage (MFC+HES) converter. First, low-voltage and medium-voltage PSC architectures are shown to decouple series-connected source currents and enable independent control. Multidimensional modeling and analysis is then discussed. Next, three system designs are discussed: single-zone, dual-zone, and multi-zone. Each implements PSC technology and high-frequency isolated full-bridge converters to interface multiple fuel cell sources to a medium voltage grid via a single multilevel neutral point clamped inverter interface. A 1-MW simulation and a reduced-scale hardware prototype offer collaborative insight into the inherit benefits of the proposed PSC systems: increased output power, operational flexibility, thermal balancing, source availability, and cost-effectiveness. Secondly, the ML9SC is presented as a component-minimized multi-port converter with low cost, high efficiency, high power quality, and low noise. The multiport characteristic of the ML9SC can be effectively employed in uninterruptible power systems, six-phase wind generators, and doubly-fed induction wind generators. Next, operating constraints and modulation index limits are analyzed at different operating conditions. Loss breakdown is analyzed and compared with the conventional back-to-back multi-level converter. Finally, simulation results are included as proof of concept. Lastly, the proposed MFC+HES converter integrates energy-dense MFC technology with power-dense storage technology. System modularization and hybridization are discussed initially, followed by a selection between supercapacitors and lithium-ion batteries (LIBs). Next, system topology and design is discussed, and the MFC and LIBs are electrically modeled such that Middlebrook’s Extra Element Theorem can mitigate unwanted system resonance and optimize system design. Simulation and hardware results for a 100W MFC+HES system realizes a 300% boost current response capability as well as the following system benefits: limp-home capability, evenly distributed heat/aging, and maximized output power