Wind energy harvester interface for sensor nodes

The research topic is developping a power converting interface for the novel FLEHAP wind energy harvester allowing the produced energy to be used for powering small wireless nodes. The harvester\u2019s electrical characteristics were studied and a strategy was developped to control and mainting a maximum power transfer. The electronic power converter interface was designed, containing an AC/DC Buck-Boost converter and controlled with a low power microcontroller. Different prototypes were developped that evolved by reducing the sources of power loss and rendering the system more efficient. The validation of the system was done through simulations in the COSMIC/DITEN lab using generated signals, and then follow-up experiments were conducted with a controllable wind tunnel in the DIFI department University of Genoa. The experiment results proved the functionality of the control algorithm as well as the efficiency that was ramped up by the hardware solutions that were implemented, and generally met the requirement to provide a power source for low-power sensor nodes

Miniaturized Power Electronic Interfaces for Ultra-compact Electromechanical Systems

Advanced and ultra-compact electromechanical (EM) systems, such as kinetic energy harvesting and microrobotic systems are deemed as enabling solutions to provide efficient energy conversion. One of the most critical challenges in such systems is to develop tiny power electronic interfaces (PEIs) capable of addressing power conditioning between EM devices and energy storage units. This dissertation presents technologies and topological solutions toward fabricating miniaturized PEIs to efficiently regulate erratic power/voltage for kinetic energy harvesting and drive high-voltage actuators for microrobotic systems. High-frequency resonant-switching topologies are introduced as power stages of PEIs that allow small footprint of the circuit without suffering from switching losses. Two types of bridgeless resonant ac-dc converters are first introduced and developed to efficiently convert arbitrary input voltages into a regulated dc output voltage. The proposed topologies provide direct ac-dc power conversion with less number of components, in comparison to other resonant topologies. A 5-mm×6-mm, 100-mg, 2-MHz and 650-mW prototype is fabricated for validation of capability of converting very-low ac voltages into a relatively higher voltage. A resonant gate drive circuit is designed and utilized to further reduce gating losses under high-frequency switching and light-load condition. The closed-loop efficiency reaches higher than 70% across wide range of input voltages and output powers. In a multi-channel energy harvesting system, a multi-input bridgeless resonant ac-dc converter is developed to achieve ac-dc conversion, step up voltage and match optimal impedance. Alternating voltage of each energy harvesting channel is stepped up through the switching LC network and then rectified by a freewheeling diode. The optimal electrical impedance can be adjusted through resonance impedance matching and pulse-frequency-modulation (PFM) control. In addition, a six-input standalone prototype is fabricated to address power conditioning for a six-channel wind panel. Furthermore, the concepts of miniaturization are incorporated in the context of microrobots. In a mobile microrobotic system, conventional bulky power supplies and electronics used to drive electroactive polymer (EAP) actuators are not practical as on-board energy sources for microrobots. A bidirectional single-stage resonant dc-dc step-up converter is introduced and developed to efficiently drive high-voltage EAP actuators. The converter utilizes resonant capacitors and a coupled-inductor as a soft-switched LC network to step up low input voltages. The circuit is capable of generating explicit high-voltage actuation signals, with capability of recovering unused energy from EAP actuators. A 4-mm × 8-mm, 100-mg and 600-mW prototype has been designed and fabricated to drive an in-plane gap-closing electrostatic inchworm motor. Experimental validations have been carried out to verify the circuit’s ability to step up voltage from 2 V to 100 V and generate two 1-kHz, 100-V driving voltages at 2-nF capacitive loads

Rectification, amplification and switching capabilities for energy harvesting systems: power management circuit for piezoelectric energy harvester

Dissertação de mestrado em Biomedical EngineeringA new energy mechanism needs to be addressed to overcome the battery dependency, and consequently extend Wireless Sensor Nodes (WSN) lifetime effectively. Energy Harvesting is a promising technology that can fulfill that premise. This work consists of the realization of circuit components employable in a management system for a piezoelectric-based energy harvester, with low power consumption and high efficiency. The implementation of energy harvesting systems is necessary to power-up front-end applications without any battery. The input power and voltage levels generated by the piezoelectric transducer are relatively low, especially in small-scale systems, as such extra care has to be taken in power consumption and efficiency of the circuits. The main contribution of this work is a system capable of amplifying, rectifying and switching the unstable signal from an energy harvester source. The circuit components are designed based on 0.13 Complementary Metal-Oxide-Semiconductor (CMOS) technology. An analog switch, capable of driving the harvesting circuit at a frequency between 1 and 1 , with proper temperature behaviour, is designed and verified. An OFF resistance of 520.6 Ω and isolation of −111.24 , grant excellent isolation to the circuit. The designed voltage amplifier is capable of amplifying a minor signal with a gain of 42.56 , while requiring low power consumption. The output signal is satisfactorily amplified with a reduced offset voltage of 8 . A new architecture of a two-stage active rectifier is proposed. The power conversion efficiency is 40.4%, with a voltage efficiency of up to 90%. Low power consumption of 17.7 is achieved by the rectifier, with the embedded comparator consuming 113.9 . The outcomes validate the circuit’s power demands, which can be used for other similar applications in biomedical, industrial, and commercial fields.Para combater a dependência dos dispositivos eletrónicos relativamente ás baterias é necessário um novo sistema energético, que permita prolongar o tempo de vida útil dos mesmos. Energy Harvesting é uma tecnologia promissora utilizada para alimentar dispositivos sem bateria. Este trabalho consiste na realização de componentes empregáveis num circuito global para extrair energia a partir ds vibrações de um piezoelétricos com baixo consumo de energia e alta eficiência. Os níveis de potência e voltagem gerados pelo transdutor piezoelétrico são relativamente baixos, especialmente em sistemas de pequena escala, por isso requerem cuidado extra relativamente ao consumo de energia e eficiência dos circuitos. A principal contribuição deste trabalho é um sistema apropriado para amplificar, retificar e alternar o sinal instável proveniente de uma fonte de energy harvesting. Os componentes do sistema são implementados com base na tecnologia CMOS com 0.13 . Um interruptor analógico capaz de modelar a frequência do sinal entre 1 e 1 e estável perante variações de temperatura, é implementado. O circuito tem um excelente isolamento de −111.24 , devido a uma resistência OFF de 520.6 Ω. O amplificador implementado é apto a amplificar um pequeno sinal com um ganho de 42.56 e baixo consumo. O sinal de saída é satisfatoriamente amplificado com uma voltagem de offset de 8 . Um retificador ativo de dois estágios com uma nova arquitetura é proposto. A eficiência de conversão de energia atinge os 40.4%, com uma eficiência de voltagem até 90%. O retificador consome pouca energia, apenas 17.7 , incorporando um comparador de 113.9 . Os resultados validam as exigências energéticas do circuito, que pode ser usado para outras aplicações similares no campo biomédico, industrial e comercial

On-chip adaptive power management for WPT-Enabled IoT

Internet of Things (IoT), as broadband network connecting every physical objects, is becoming more widely available in various industrial, medical, home and automotive applications. In such network, the physical devices, vehicles, medical assistance, and home appliances among others are supposed to be embedded by sensors, actuators, radio frequency (RF) antennas, memory, and microprocessors, such that these devices are able to exchange data and connect with other devices in the network. Among other IoT’s pillars, wireless sensor network (WSN) is one of the main parts comprising massive clusters of spatially distributed sensor nodes dedicated for sensing and monitoring environmental conditions. The lifetime of a WSN is greatly dependent on the lifetime of the small sensor nodes, which, in turn, is primarily dependent on energy availability within every sensor node. Predominantly, the main energy source for a sensor node is supplied by a small battery attached to it. In a large WSN with massive number of deployed sensor nodes, it becomes a challenge to replace the batteries of every single sensor node especially for sensor nodes deployed in harsh environments. Consequently, powering the sensor nodes becomes a key limiting issue, which poses important challenges for their practicality and cost. Therefore, in this thesis we propose enabling WSN, as the main pillar of IoT, by means of resonant inductive coupling (RIC) wireless power transfer (WPT). In order to enable efficient energy delivery at higher range, high quality factor RIC-WPT system is required in order to boost the magnetic flux generated at the transmitting coil. However, an adaptive front-end is essential for self-tuning the resonant tank against any mismatch in the components values, distance variation, and interference from close metallic objects. Consequently, the purpose of the thesis is to develop and design an adaptive efficient switch-mode front-end for self-tuning in WPT receivers in multiple receiver system. The thesis start by giving background about the IoT system and the technical bottleneck followed by the problem statement and thesis scope. Then, Chapter 2 provides detailed backgrounds about the RIC-WPT system. Specifically, Chapter 2 analyzes the characteristics of different compensation topologies in RIC-WPT followed by the implications of mistuning on efficiency and power transfer capability. Chapter 3 discusses the concept of switch-mode gyrators as a potential candidate for generic variable reactive element synthesis while different potential applications and design cases are provided. Chapter 4 proposes two different self-tuning control for WPT receivers that utilize switch-mode gyrators as variable reactive element synthesis. The performance aspects of control approaches are discussed and evaluated as well in Chapter 4. The development and exploration of more compact front-end for self-tuned WPT receiver is investigated in Chapter 5 by proposing a phase-controlled switched inductor converter. The operation and design details of different switch-mode phase-controlled topologies are given and evaluated in the same chapter. Finally, Chapter 6 provides the conclusions and highlight the contribution of the thesis, in addition to suggesting the related future research topics.Internet de las cosas (IoT), como red de banda ancha que interconecta cualquier cosa, se está estableciendo como una tecnología valiosa en varias aplicaciones industriales, médicas, domóticas y en el sector del automóvil. En dicha red, los dispositivos físicos, los vehículos, los sistemas de asistencia médica y los electrodomésticos, entre otros, incluyen sensores, actuadores, subsistemas de comunicación, memoria y microprocesadores, de modo que son capaces de intercambiar datos e interconectarse con otros elementos de la red. Entre otros pilares que posibilitan IoT, la red de sensores inalámbricos (WSN), que es una de las partes cruciales del sistema, está formada por un conjunto masivo de nodos de sensado distribuidos espacialmente, y dedicados a sensar y monitorizar las condiciones del contexto de las cosas interconectadas. El tiempo de vida útil de una red WSN depende estrechamente del tiempo de vida de los pequeños nodos sensores, los cuales, a su vez, dependen primordialmente de la disponibilidad de energía en cada nodo sensor. La fuente principal de energía para un nodo sensor suele ser una pequeña batería integrada en él. En una red WSN con muchos nodos y con una alta densidad, es un desafío el reemplazar las baterías de cada nodo sensor, especialmente en entornos hostiles, como puedan ser en escenarios de Industria 4.0. En consecuencia, la alimentación de los nodos sensores constituye uno de los cuellos de botella que limitan un despliegue masivo práctico y de bajo coste. A tenor de estas circunstancias, en esta tesis doctoral se propone habilitar las redes WSN, como pilar principal de sistemas IoT, mediante sistemas de transferencia inalámbrica de energía (WPT) basados en acoplamiento inductivo resonante (RIC). Con objeto de posibilitar el suministro eficiente de energía a mayores distancias, deben aumentarse los factores de calidad de los elementos inductivos resonantes del sistema RIC-WPT, especialmente con el propósito de aumentar el flujo magnético generado por el inductor transmisor de energía y su acoplamiento resonante en recepción. Sin embargo, dotar al cabezal electrónico que gestiona y condicionada el flujo de energía de capacidad adaptativa es esencial para conseguir la autosintonía automática del sistema acoplado y resonante RIC-WPT, que es muy propenso a la desintonía ante desajustes en los parámetros nominales de los componentes, variaciones de distancia entre transmisor y receptores, así como debido a la interferencia de objetos metálicos. Es por tanto el objetivo central de esta tesis doctoral el concebir, proponer, diseñar y validar un sistema de WPT para múltiples receptores que incluya funciones adaptativas de autosintonía mediante circuitos conmutados de alto rendimiento energético, y susceptible de ser integrado en un chip para el condicionamiento de energía en cada receptor de forma miniaturizada y desplegable de forma masiva. La tesis empieza proporcionando una revisión del estado del arte en sistemas de IoT destacando el reto tecnológico de la alimentación energética de los nodos sensores distribuidos y planteando así el foco de la tesis doctoral. El capítulo 2 sigue con una revisión crítica del statu quo de los sistemas de transferencia inalámbrica de energía RIC-WPT. Específicamente, el capítulo 2 analiza las características de diferentes estructuras circuitales de compensación en RIC-WPT seguido de una descripción crítica de las implicaciones de la desintonía en la eficiencia y la capacidad de transferencia energética del sistema. El capítulo 3 propone y explora el concepto de utilizar circuitos conmutados con función de girador como potenciales candidatos para la síntesis de propósito general de elementos reactivos variables sintonizables electrónicamente, incluyendo varias aplicaciones y casos de uso. El capítulo 4 propone dos alternativas para métodos y circuitos de control para la autosintonía de receptores de energíaPostprint (published version

Silicon carbide based DC-DC converters for deployment in hostile environments

PhD ThesisThe development of power modules for deployment in hostile environments, where the elevated ambient temperatures demand high temperature capability of the entire converter system, requires innovative power electronic circuits to meet stringent requirements in terms of efficiency, power-density and reliability. To simultaneously meet these conflicting requirements in extreme environment applications is quite challenging. To realise these power modules, the relevant control circuitry also needs to operate at elevated temperatures. The recent advances in silicon carbide devices has allowed the realisation of not just high frequency, high efficiency power converters, but also the power electronic converters that can operate at elevated temperatures, beyond those possible using conventional silicon-based technology. High power-density power converters are key components for power supply systems in applications where space and weight are critical parameters. The demand for higher power density requires the use of high-frequency DC-DC converters to overcome the increase in size and power losses due to the use of transformers. The increase in converter switching frequency reduces the size of passive components whilst increasing the electromagnetic interference (EMI) emissions. A performance comparison of SiC MOSFETs and JFETs in a high-power DC-DC converter to form part of a single phase PV inverter system is presented. The drive design requirements for optimum performance in the energy conversion system are also detailed. The converter was tested under continuous conduction mode at frequencies up to 250 kHz. The converter power efficiency, switch power loss and temperature measurements are then compared with the ultra-high speed CoolMOS switches and SiC diodes. The high voltage, high frequency and high temperature operation capability of the SiC DUTs are also demonstrated. The all SiC converters showed more stable efficiencies of 95.5% and 96% for the switching frequency range for the SiC MOSFET and JFET, respectively. A comparison of radiated noise showed the highest noise signature for the SiC JFET and lowest for the SiC MOSFET. The negative gate voltage requirement of the SiC MOSFET introduces up to 6 dBμV increase in radiated noise, due to the induced current in the high frequency resonant stray loop in the gate drive negative power plane. ii A gate driver is an essential part of any power electronic circuitry to control the switching of the power semiconductor devices. The desire to place the gate driver physically close to the power switches in the converter, leads to the necessity of a temperature resilient PWM generator to control the power electronics module. At elevated temperatures, the ability to control electrical systems will be a key enabler for future technology enhancements. Here an SiC/SOI-based PWM gate driver is proposed and designed using a current source technique to accomplish variable duty-cycle PWM generation. The ring oscillator and constant current source stages use low power normally-on, epitaxial SiC-JFETs fabricated at Newcastle University. The amplification and control stages use enhancement-mode signal SOI MOSFETs. Both SOI MOSFETs will be replaced by future high current SiC-JFETs with only minor modification to the clamp-stage circuit design. In the proposed design, the duty cycle can be varied from 10% to 90%. The PWM generator is then evaluated in a 200 kHz step-up converter which results in a 91% efficiency at 81% duty cycle. High temperature environments are incompatible with standard battery technologies, and so, energy harvesting is a suitable technology when remote monitoring of these extreme environments is performed through the use of wireless sensor nodes. Energy harvesting devices often produce voltages which are unusable directly by electronic loads and so require power management circuits to convert the electrical output to a level which is usable by monitoring electronics and sensors. Therefore a DC-DC step-up converter that can handle low input voltages is required. The first demonstration of a novel self-starting DC-DC converter is reported, to supply power to a wireless sensor node for deployment in high temperature environments. Utilising SiC devices a novel boost converter topology has been realised which is suitable for boosting a low voltage to a level sufficient to power a sensor node at temperatures up to 300 °C. The converter operates in the boundary between continuous and discontinuous mode of operation and has a VCR of 3 at 300 °C. This topology is able to self start and so requires no external control circuitry, making it ideal for energy harvesting applications, where the energy supply may be intermittent.EPSRC and BAE SYSTEMS through the Dorothy Hodgkin Postgraduate Awar

An ultra-low power voltage regulator system for wireless sensor networks powered by energy harvesting

A DC-DC converter is an important power management module as it converts one DC voltage level to another suitable for powering a desired electronic system. It also stabilizes the output voltage when fluctuations appear in the power supplies. For those wireless sensor networks (WSNs) powered by energy harvesting, the DC-DC converter is usually a linear regulator and it resides at the last stage of the whole energy harvesting system just before the empowering sensor node. Due to the low power densities of energy sources, one may have to limit the quiescent current of the linear regulator in the sub-uA regime. This severe restriction on quiescent current could greatly compromise other performance aspects, especially the transient response. This dissertation reports a voltage regulator system topology which utilizes the sensor node state information to achieve ultra-low power consumption. The regulator system is composed of two regulators with different current driving abilities and quiescent current consumptions. The key idea is to switch between the two regulators depending on the sensor state. Since the "right" regulator is used at the "right" time, the average quiescent current of the regulator system is minimized, and the trade-off between low quiescent current and fast transient response has been eliminated. In order to minimize the average quiescent current of the system, nano-ampere reference current design is studied, and the proposed reference current circuit is shown (theoretically and experimentally) to reduce the supply voltage dependence by 5X. The regulator system has been fabricated and tested using an ON Semiconductor 0.5 μm process. It has been verified through experiments that the proposed system reduces the quiescent current by 3X over the state-of-the-art in the literature; and, more importantly, it achieves low quiescent current, low dropout voltage, and fast transient response with small output voltage variation all at the same time. The thesis further presents data on the application of energy harvesting system deriving energies from various RF signals to power a commercial off-shelf wireless sensor node

Robustness and durability aspects in the design of power management circuits for IoT applications

With the increasing interest in the heterogeneous world of the “Internet of Things” (IoT), new compelling challenges arise in the field of electronic design, especially concerning the development of innovative power management solutions. Being this diffusion a consolidated reality nowadays, emerging needs like lifetime, durability and robustness are becoming the new watchwords for power management, being a common ground which can dramatically improve service life and confidence in these devices. The possibility to design nodes which do not need external power supply is a crucial point in this scenario. Moreover, the development of autonomous nodes which are substantially maintenance free, and which therefore can be placed in unreachable or harsh environments is another enabling aspect for the exploitation of this technology. In this respect, the study of energy harvesting techniques is increasingly earning interest again. Along with efficiency aspects, degradation aspects are the other main research field with respect to lifetime, durability and robustness of IoT devices, especially related to aging mechanisms which are peculiar in power management and power conversion circuits, like for example battery wear during usage or hot-carrier degradation (HCD) in power MOSFETs. In this thesis different aspects related to lifetime, durability and robustness in the field of power management circuits are studied, leading to interesting contributions. Innovative designs of DC/DC power converters are studied and developed, especially related to reliability aspects of the use of electrochemical cells as power sources. Moreover, an advanced IoT node is proposed, based on energy harvesting techniques, which features an intelligent dynamically adaptive power management circuit. As a further contribution, a novel algorithm is proposed, which is able to effectively estimate the efficiency of a DC/DC converter for photovoltaic applications at runtime. Finally, an innovative DC/DC power converter with embedded monitoring of hot-carrier degradation in power MOSFETs is designed

Power quality improvement utilizing photovoltaic generation connected to a weak grid

Microgrid research and development in the past decades have been one of the most popular topics. Similarly, the photovoltaic generation has been surging among renewable generation in the past few years, thanks to the availability, affordability, technology maturity of the PV panels and the PV inverter in the general market. Unfortunately, quite often, the PV installations are connected to weak grids and may have been considered as the culprit of poor power quality affecting other loads in particular sensitive loads connected to the same point of common coupling (PCC). This paper is intended to demystify the renewable generation, and turns the negative perception into positive revelation of the superiority of PV generation to the power quality improvement in a microgrid system. The main objective of this work is to develop a control method for the PV inverter so that the power quality at the PCC will be improved under various disturbances. The method is to control the reactive current based on utilizing the grid current to counteract the negative impact of the disturbances. The proposed control method is verified in PSIM platform. Promising results have been obtaine