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1
Qureshi, Fassahat Ullah. "Fast frequency response services for low inertia power systems". Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/20764.
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Power systems in the world are undergoing a major transformation due to the displacement of conventional synchronous generators (SGs) and increasing penetration of non-synchronous renewable energy sources (NS-RES) in the electricity grids. A computationally efficient analytical tool incorporating FFR services to determine the frequency performance of a low synchronous inertia power system is a major contribution of this thesis. First, we study the impact of high penetration of NS-RES on the frequency stability of the electricity grids. Second, we study the impact of reduced synchronous inertia on the power system stability of the electricity grid. Third, we study the frequency stability of a low inertia power system by means of the time domain simulations. We considered the impact of different grid topologies on the frequency performance of the system because frequency dynamics are also affected by grid topology in a power system. Furthermore, we developed a wind-based FFR service and used that service to improve the frequency stability of a low inertia power system. Finally, we developed a computationally efficient analytical tool incorporating FFR services to improve the frequency stability of a low inertia power system by avoiding computationally expensive simulations. The tool identifies the locations in a low inertia power system that are highly sensitive to the disturbance by computing rate of change of frequency (RoCoF) sensitivities with respect to synchronous inertia for the placement of FFR services in those locations. Hence in this thesis, we have presented both simulation-based and system-theoretic approaches to improve the frequency stability of the FGs by using FFR services that will help policymakers to determine and improve the frequency performance of a low inertia power system.
2
Niemelä, Elvira y Lucas Wallhager. "Fast Power Support of Electrical Batteries in Future Low Inertia Power Systems". Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281935.
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To create more sustainable power systems, as well as achieve environmental goals, further integration of Renewable Energy Sources (RES) is essential. However, this may result in a power system more vulnerable to disturbances, since RES do not contribute to the system’s inertia. A power system’s ability to counteract disturbances is highly dependant on inertia. This is because the power system uses the kinetic energy of rotating machines, i.e. inertia, to restore the power balance after a disturbance. This causes a deviation of the system’s frequency, which must be contained within certain limits or, in the worst case scenario, a blackout could follow. Frequency Containment Reserves (FCR) stabilizes the frequency first dozens of seconds after a disturbance, therefore, it is the inertia that plays the major role in controlling the initial frequency deviation. One possibility to counter disturbances in a power system with less inertia is to use electrical batteries as fast power support, by injecting power into the system when needed. This project aims to investigate the dynamics of the FCR as well as the possibility to use batteries as fast power support. Different parameters of the batteries are also analyzed. The project is conducted through a case study of a power system model in Simulink and Matlab. Additional aspects, such as sustainability, cost-effectiveness, and future research, are discussed.För att skapa mer hållbara kraftsystem, men även uppnå miljömål, är fortsatt integrering av förnyelsebara energikällor viktigt. Dock kan detta resultera i ett kraftsystem som är mer sårbart mot störningar, då förnyelsebara energikällor inte bidrar till systemets svängmassa. Ett kraftsystems förmåga att möta störningar är direkt relaterad till svängmassan i systemet. Detta är på grund av att systemet använder kinetisk energi från roterande maskiner, deras svängmassa, för att återställa balans mellan produktion och konsumtion efter en störning. Dock orsakar detta en avvikelse hos systemets frekvens, som måste hållas inom vissa gränser, annars kan det i värsta fall leda till strömavbrott. Primärreglering stabiliserar frekvensen först dussin sekunder efter en störning, därför är det svängmassan som spelar den avgörande rollen för att kontollera den initiella avvikelsen. En möjlig lösning för att möta störningar i ett kraftsystem med mindre svängmassa är att använda elektriska batterier som snabbt kraftstöd, genom att tillföra effekt till systemet vid behov. Detta projekt syftar till att undersöka dynamiken hos primärregleringen men även huruvida batterier kan användas som snabbt kraftstöd. Olika parametrar hos batterierna analyseras även. Projektet görs genom en fallstudie av en model av ett kraftsystem i Simulink och Matlab. Andra aspekter, så som hållbarhet, kostnadseffektivitet samt framtida forskning diskuteras.
3
Alahmad, Bashar. "The role of location of low inertia in power systems". Thesis, Uppsala universitet, Institutionen för elektroteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444863.
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The plans to reduce the energy-related greenhouse gas emissions stimulate the deployment of electronically interfaced renewable resources. The increased penetration of such intermittent sources together with phasing conventional power plants out and the installation of High Voltage Direct Current (HVDC) links for long-distance more efficient transmission, reduces the stored inertia in any electrical grid. This leads to a more vulnerable power system and increases the significance of studying the corresponding stability aspects. Decreasing the inertial response of a power system deteriorates the quality of both frequency and rotor-angle stability which are the dynamics of interest in this study. The thesis explores the role of the location of low inertia on varying the power system’s dynamics. This is to be conducted in isolation of all other factors that could affect the study outcomes, such as dealing with the same system’s inertia value upon lowering the inertia in different locations. To accomplish this objective, it is essential to analyze the inertia distribution of the examined power system following the alterations of inertia reduction location. Accordingly, an inherently previous work methodology, that estimates the relative distance of the system’s components to Center Of Inertia (COI), is utilized throughout this study. Both frequency response and small-signal stability are analyzed in light of the inertia distribution results. The thesis examines two different power systems, a small two-area model and a bigger more realistic power system. The former model, known as Kundur model, helps in building a conceptual process to apply the methodology and to benchmark the dynamics of interest. While the latter is a reduced model of the Swedish transmission grid, known as Nordic 32 model. Different scenarios of low inertia are considered to capture the current trend of integrating more Renewable Energy Sources (RES) and phasing out more conventional plants. DIgSILENT Powerfactory is the weapon of choice in this study. It is utilized to assess both the frequency stability by performing electromechanical transients’ simulations, and small-signal stability following modal analysis simulations. Results show that the alterations of low inertia location are associated with variations in Instantaneous Frequency Deviation (IFD), Rate Of Change Of Frequency (ROCOF) and the damping ratio of the most critical inter-area oscillation mode. These variations have different levels of significance. Variations of the latter two metrics have the most considerable effects from the stability’s perspective. They can be utilized to prioritize the phasing out process of the conventional power plants, and to choose one of the scenarios of a specific low inertia location over the others. This helps in fulfilling proper long-term planning and short-term operation from the system operator’s perspective.
4
MOSCA, CARMELO. "Methodologies for Frequency Stability Assessment in Low Inertia Power Systems". Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2895393.
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Schmitt, Andreas Joachim. "Power System Parameter Estimation for Enhanced Grid Stability Assessment in Systems with Renewable Energy Sources". Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/83459.
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The modern day power grid is a highly complex system; as such, maintaining stable operations of the grid relies on many factors. Additionally, the increased usage of renewable energy sources significantly complicates matters. Attempts to assess the current stability of the grid make use of several key parameters, however obtaining these parameters to make an assessment has its own challenges. Due to the limited number of measurements and the unavailability of information, it is often difficult to accurately know the current value of these parameters needed for stability assessment. This work attempts to estimate three of these parameters: the Inertia, Topology, and Voltage Phasors. Without these parameters, it is no longer possible to determine the current stability of the grid. Through the use of machine learning, empirical studies, and mathematical optimization it is possible to estimate these three parameters when previously this was not the case. These three methodologies perform estimations through measurement-based approaches. This allows for the obtaining of these parameters without required system knowledge, while improving results when systems information is known.Ph. D.
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Dalal, Milap. "Low noise, low power interface circuits and systems for high frequency resonant micro-gyroscopes". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44861.
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Today's state-of-the-art rate vibratory gyroscopes use a large proof mass that vibrates at a low resonance frequency (3-30 kHz), a condition that creates a performance tradeoff in which the gyroscope can either offer large bandwidth or high resolution, but not both. This tradeoff led to the development of the capacitive bulk acoustic wave (BAW) silicon disk gyroscope, a new class of micromachined rate vibratory gyroscopes operating in the frequency range of 1-10MHz with high device bandwidth and shock/vibration tolerance. By scaling the frequency, BAW gyroscopes can provide low mechanical noise without sacrificing the high bandwidth performance needed for most commercial applications. The drive loop of the BAW gyroscope can also be exploited as a timing device that can be integrated in existing commercial systems to provide competitive clock performance to the state-of-the-art using less area and power.
This dissertation discusses the design and implementation of a CMOS ASIC architecture that interfaces with a high-Q, wide-bandwidth BAW gyroscope and the challenges associated with optimizing the noise performance to achieve navigation-grade levels of sensitivity as the frequency is scaled into the MHz regime. Mathematical models are derived to describe the operation of the sensor and are used to generate equivalent electrical circuit models of the gyroscope. A design strategy is then outlined for the ASIC to optimize the drive loop and sense channel for power and noise, and steps toward reducing this noise as the system is pushed to navigation-grade performance are presented that maintain optimum system power consumption.
After analyzing the BAW gyroscope and identifying a strategy for developing the drive and sense interface circuitry, a complete fully-differential ASIC is designed in 0.18μm CMOS to interface with a bulk acoustic wave (BAW) disk gyroscope. As an oscillator, the gyroscope provides an uncompensated clock signal at ~9.64 MHz with a temperature sensitivity of -27 ppm/°C and phase noise of -104 dBc at 1 kHz from carrier. When the complete ASIC is interfaced with the gyroscope, the sensor shows a measured rate sensitivity of 1.15 mV/o/s with an open-loop bandwidth of 280 Hz and a bias instability of 0.095 o/s, suitable for the rate-grade performance commonly required for commercial and consumer electronics applications. The system is recorded to have a total power of 1.6 mW and a total area of 0.64 mm2.
Following the design of the interface ASIC, this dissertation investigates in further detail the requirements for designing and optimizing charge pumps for capacitive MEMS devices. Basic charge pump design is outlined, followed by an overview of techniques that can be used to generate larger polarization voltages from the ASIC. Lastly, an alternate measurement technique for measuring the rotation rate of the gyroscope is discussed. This technique is based on the phase-shift modulation of the gyroscope output signal when the device is driven with two orthogonal signal inputs and can be easily modified to provide either linear scale factor measurement or a linear calibration curve that can be used to track and adjust the variation of the sensor scale factor over time.
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Zhang, Shengqi. "Investigating the impacts of renewable energy generators and energy storage systems on power system frequency response". Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/94463/1/Shengqi_Zhang_Thesis.pdf.
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High level of intermittent renewable generation such as PV plants and wind farms will require distributed storage systems to meet the power system frequency operation standards. This thesis proposes a rule-based controller to co-ordinate the renewables and distributed energy storage system for improving frequency response.
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Kelada, Fadi Sameh Aziz. "Étude des dynamiques et de la stabilité des réseaux électriques faible inertie avec une forte pénétration de ressources renouvelables". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALT065.
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Les systèmes électriques évoluent de manière significative en raison de facteurs économiques, géopolitiques et environnementaux, notamment l'intégration croissante de sources d'énergie renouvelable (RES) interfacées par des convertisseurs électroniques de puissance, connus sous le nom de ressources basées sur des onduleurs (IBR). Ce passage de systèmes dominés par des machines synchrones (SM) à des systèmes dominés par des IBR introduit des défis tels que la réduction de l'inertie, l'intermittence et les problèmes de stabilité. Les techniques traditionnelles d'analyse et de modélisation de la stabilité, qui supposent des dynamiques plus lentes inhérentes aux SM, sont inadéquates pour les dynamiques rapides des IBR. La dominance émergente des IBR nécessite le développement de modèles détaillés de transitoires électromagnétiques (EMT), qui sont intensifs en calcul mais essentiels pour capturer les dynamiques rapides des systèmes électriques modernes. Les cadres de classification de la stabilité existants, historiquement basés sur des systèmes dominés par les SM, sont en cours de révision pour incorporer les influences des IBR, introduisant de nouvelles catégories de stabilité comme la stabilité pilotée par convertisseur (CDS). Ce travail explore de nouvelles perspectives sur les interactions entre les SM, les dynamiques des unités IBR et les dynamiques des réseaux, qui ont été négligées dans la littérature. Il fournit un cadre complet qui est open-source et adaptable pour des topologies de systèmes électriques génériques, permettant des résultats et des analyses évolutifs. De plus, le cadre proposé est utilisé pour déterminer les allocations optimales d'inertie virtuelle et d'amortissement dans les systèmes électriques à faible inertie afin d'améliorer les métriques de stabilité de la fréquencePower systems are evolving significantly due to economic, geopolitical, and environmental factors, notably the increasing integration of Renewable Energy Sources (RES) interfaced through power electronic converters, known as Inverter-Based Resources (IBR). This shift from synchronous machine (SM)-dominated systems to IBR-dominated systems introduces challenges such as reduced inertia, intermittency, and stability issues. Traditional stability analysis and modeling techniques, which assume slower dynamics inherent in SMs, are inadequate for the fast dynamics of IBRs. The emerging dominance of IBRs necessitates the development of detailed Electromagnetic Transient (EMT) models, which are computationally intensive but essential for capturing the fast dynamics of modern power systems. Existing stability classification frameworks, historically based on SM-dominated systems, are being revised to incorporate IBR influences, introducing new stability categories like Converter-Driven Stability (CDS). This work investigates novel insights into the interactions between SMs, IBR unit dynamics, and network dynamics that have been overlooked in the literature. It provides a comprehensive framework that is open-source and adaptable for generic power system topologies, allowing for scalable results and analyses. Furthermore, the proposed framework is utilized to determine optimal allocations of virtual inertia and damping in low inertia power systems to enhance frequency stability metrics
9
El-Damak, Dina Reda. "Power management circuits for ultra-low power systems". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99821.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 137-145).
Power management circuits perform a wide range of vital tasks for electronic systems including DC-DC conversion, energy harvesting, battery charging and protection as well as dynamic voltage scaling. The impact of the efficiency of the power management circuits is highly profound for ultra-low power systems such as implantable, ingestible or wearable devices. Typically the size of the system for such applications does not allow the integration of a large energy storage device. Therefore, extreme energy efficiency of the power management circuits is critical for extended operation time. In addition, flexibility and small form factor are desirable to conform to the human body and reduce the system's over all size. Thus, this thesis presents highly efficient and miniature power converters for multiple applications using architecture and circuit level optimization as well as emerging technologies. The first part presents a power management IC (PMIC) featuring an integrated reconfigurable switched capacitor DC-DC converter using on-chip ferroelectric caps in 130 nm CMOS process. Digital pulse frequency modulation and gain selection circuits allow for efficient output voltage regulation. The converter utilizes four gain settings (1, 2/3, 1/2, 1/3) to support an output voltage of 0.4 V to 1.1 V from 1.5 V input while delivering load current of 20 [mu]A to 1 mA. The PMIC occupies 0.366 mm² and achieves a peak efficiency of 93% including the control circuit overhead at a load current of 500 [mu]A. The second part presents a solar energy harvesting system with 3.2 nW overall quiescent power. The chip integrates self-startup, battery management, supplies 1 V regulated rail with a single inductor and supports power range of 10 nW to 1 [mu]W. The control circuit is designed in an asynchronous fashion that scales the effective switching frequency of the converter with the level of the power transferred. The ontime of the converter switches adapts dynamically to the input and output voltages for peak-current control and zero-current switching. The system has been implemented in 180 nm CMOS process. For input power of 500 nW, the proposed system achieves an efficiency of 82%, including the control circuit overhead, while charging a battery at 3 V from 0.5 V input. The third part focuses on developing an energy harvesting system for an ingestible device using gastric acid. An integrated switched capacitor DC-DC converter is designed to efficiently power sensors and RF transmitter with a 2.5 V regulated voltage rail. A reconfigurable Dickson topology with four gain settings (3, 4, 6, 10) is used to support a wide input voltage range from 0.3 V to 1.1 V. The converter is designed in 65 nm CMOS process and achieves a peak efficiency of 80% in simulation for output power of 2 [mu]W. The last part focuses on flexible circuit design using Molybdenum Disulfide (MoS₂), one of the emerging 2D materials. A computer-aided design flow is developed for MoS₂-based circuits supporting device modeling, circuit simulation and parametric cell-based layout - which paves the road for the realization of large-scale flexible MoS₂ systems.
by Dina Reda El-Damak.
Ph. D.
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Maalouf, Divine. "Contribution to nonlinear adaptive control of low inertia underwater robots". Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20196/document.
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L'utilisation des véhicules sous-marins (ROV, AUV, gliders) s'est considérablement accrue ces dernières décennies, aussi bien dans le domaine de l'offshore ou de l'océanographie, que pour des applications militaires. Dans cette thèse, nous abordons le problème particulier de la commande des véhicules sous-marins à faible inertie et fort rapport puissance/inertie. Ces derniers constituent des systèmes fortement non linéaires, dont la dynamique est susceptible de varier au cours du temps (charge embarquée, caractéristiques des propulseurs, variation de salinité...) et qui sont très sensibles aux perturbations environnementales (chocs, traction sur l'ombilical...). Afin d'assurer des performances de suivi de trajectoire satisfaisantes, il est nécessaire d'avoir recours à une commande adaptative qui compense les incertitudes ou les variations des paramètres du modèle dynamique, mais également qui rejette les perturbations, telles que les chocs. A cette fin, nous proposons dans ce manuscrit, l'étude théorique et la validation expérimentale de plusieurs lois de commande pour véhicules sous-marins. Nous analysons tout d'abord des approches classiques dans ce domaine (commande PID et commande par retour d'état non linéaire), puis nous les comparons avec deux autres architectures de commande. La première est la commande adaptative L1 non linéaire, introduite en 2010 notamment pour la commande des véhicules aériens, et implémentée pour la première fois sur un véhicule sous-marin. Le découplage entre adaptation et robustesse permet l'utilisation de très grands gains d'adaptation (et donc une convergence plus rapide des paramètres estimés, sans aucune connaissance a priori), sans pour autant dégrader la stabilité. La seconde méthode, que nous proposons et qui constitue l'apport principal de cette thèse, est une évolution de la commande L1, permettant d'en améliorer les performances lors du suivi d'une trajectoire variable. Nous présentons une analyse de stabilité de cette commande, ainsi que sa comparaison expérimentale avec les autres lois de commande (commande PID, commande adaptative par retour d'état non linéaire et commande adaptative L1 standard). Ces expérimentations ont été réalisées sur un mini-ROV et plusieurs scenarii ont été étudiés, permettant ainsi d'évaluer, pour chaque loi, sa robustesse et son aptitude à rejeter les perturbationsUnderwater vehicles have gained an increased interest in the last decades given the multiple tasks they can accomplish in various fields, ranging from scientific to industrial and military applications. In this thesis, we are particularly interested in the category of vehicles having a high power to weight ratio. Different challenges in autonomous control of such highly unstable systems arise from the inherent nonlinearities and the time varyingbehavior of their dynamics. These challenges can be increased by the low inertia of this class of vehicles combined with their powerful actuation. A self tuning controller is therefore required in order to avoid any performance degradation during a specific mission. The closed-loop system is expected to compensate for different kinds of disturbances or changes in the model parameters. To solve this problem, we propose in this work the design,analysis and experimental validation of different control schemes on an underwater vehicle. Classical methods are initially proposed, namely the PID controller and the nonlinear adaptive state feedback (NASF) one, followed by two more advanced schemes based on the recently developed L1 adaptive controller. This last method stands out among the other developed ones in its particular architecture where robustness and adaptation are decoupled. In this thesis, the original L1 adaptive controller has been designed and successfullyvalidated then an extended version of it is proposed in order to deal with the observed time lags occurring in presence of a varying reference trajectory. The stability of this latter controller is then analysed and real-time experimental results for different operating conditions are presented and discussed for each proposed controller, assessing their performance and robustness
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Chen, Mingdeng. "Low-voltage, low-power circuits for data communication systems". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1585.
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There are growing industrial demands for low-voltage supply and low-power consumption circuits and systems. This is especially true for very high integration level and very large scale integrated (VLSI) mixed-signal chips and system-on-a-chip. It is mainly due to the limited power dissipation within a small area and the costs related to the packaging and thermal management. In this research work, two low-voltage, low-power integrated circuits used for data communication systems are introduced. The first one is a high performance continuous-time linear phase filter with automatic frequency tuning. The filter can be used in hard disk driver systems and wired communication systems such as 1000Base-T transceivers. A pseudo-differential operational transconductance amplifier (OTA) based on transistors operating in triode region is used to achieve a large linear signal swing with low-voltage supplies. A common-mode (CM) control circuit that combines common-mode feedback (CMFB), common-mode feedforward (CMFF), and adaptive-bias has been proposed. With a 2.3V single supply, the filters total harmonic distortion is less than 44dB for a 2VPP differential input, which is due to the well controlled CM behavior. The ratio of the root mean square value of the ac signal to the power supply voltage is around 31%, which is much better than previous realizations. The second integrated circuit includes two LVDS drivers used for high-speed point-to-point links. By removing the stacked switches used in the conventional structures, both LVDS drivers can operate with ultra low-voltage supplies. Although the Double Current Sources (DCS) LVDS driver draws twice minimum static current as required by the signal swing, it is quite simple and achieves very high speed operation. The Switchable Current Sources (SCS) LVDS driver, by dynamically switching the current sources, draws minimum static current and reduces the power consumption by 60% compared to the previously reported LVDS drivers. Both LVDS drivers are compliant to the standards and operate at data rates up to gigabits-per-second.
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Choi, Kyu-Won. "Hierarchical power optimization for ultra low-power digital systems". Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180111/unrestricted/choi%5Fkyu-won%5F200312%5Fphd.pdf.
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Rakhshani, Elyas. "Analysis and control of multi–area HVDC interconnected power systems by using virtual inertia". Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404614.
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Virtual inertia is known as an inevitable part of the modern power systems. Recent trend of research is oriented in different methods of emulating virtual inertia in different part of the systems. This dissertation is focused on modelling, analysing and application of virtual inertia concept in frequency control and Automatic Generation Control (AGC) issue in high level control AC/DC interconnected power systems. Since the virtual inertia is provided by advanced control concepts of power electronic based components, the HVDC links are the main focus of this dissertation for emulating inertia.
AGC in a multi-area power system during load and resource variation is known as a very important mechanism that could facilitate various tasks like: frequency restoration, tie-line power control between authority areas and economic dispatch of generation units. The AGC concept is known as higher level control at the transmission level. This higher level control will generate the set-points for all the local components, like generators or power converter stations, which are under control by their local controllers.
In this thesis two different methods for emulating virtual inertia are proposed and introduced in AGC modelling and control of AC/DC interconnected power systems.
The first method which is one of the common methods for emulating inertia in various filed of applications, is derivative control technique. In this thesis, derivative control technique is used for higher level application of inertia emulation. This
method of inertia emulation is developed for two-area AGC system which is connected by parallel AC/DC transmission lines. Based on the proposed technique, the dynamic effect of inertia emulated for frequency and active power control of interconnected systems are evaluated. The effects of frequency measurements delay and Phase Locked Loop (PLL) effects are also considered by introducing a second-order function. Simulations performed by Matlab software demonstrate how virtual inertia emulation can effectively improve the performance of the power system. A detailed eigenvalue and sensitivity analyses have been also performed to support the positive effects of the proposed method.
Since the first method is based on derivation for grid frequency, the measurement of frequency is very important and application of different method for frequency measurements like PLL will bring some limitations for this method. Therefore, as an ultimate solution, the second method for virtual inertia emulation is introduced in this thesis. The second method is based on Virtual Synchronous Power (VSP) concept. The concept of VSP to simulate the dynamic effects of inertia emulations by HVDC links for higher level control applications is introduced and reflected in the multi-area AGC model. By using this proposed combination in AGC model, the dynamic performance of the systems shows a significant improvement. The active power loop control on VSP based HVDC link has second-order characteristic which make a simultaneous enabling of damping and inertia emulations into the system. Trajectory sensitivities and eigenvalue analyses are used to analyse the effects of VSP on the system stability. The effectiveness of proposed concept on dynamic improvements is tested through Matlab simulation of multi-area test system.
Finally, it became clear that virtual inertia will add additional degree of freedom to the system dynamics which makes a considerable improvement in first overshoot in addition to damping characteristics of HVDC links. Comparing the results of these two different methods of inertia emulation shows that VSP technique has better performance with several advantages for emulating the inertia. In the VSP technique, PLL and frequency estimation are not required. Also considering the fact that simultaneous damping and inertia could be emulated, a powerful method based on VSP for improving the system dynamics during the contingencies is proposed.El concepto de inercia virtual se está convirtiendo en una parte imprescindible de los sistemas de energía modernos y en la actualidad hay diferentes líneas de investigación orientadas a estudiar diferentes métodos de emulación de inercia virtual en diferentes partes del sistema.Esta tesis doctoral se centra en el modelado, análisis y aplicación del concepto de inercia virtual en el control de frecuencia y en el control automático de generación (AGC), los cuales son elementos clave en el control de alto nivel de los sistemas eléctricos interconectados AC / DC.Dada la evolución tanto en las topologías, como en las prestaciones de control de los convertidores electrónicos de potencia, los enlaces HVDC y el control a alto nivel de los dispositivos implicados para emular inercia constituirán el foco principal de esta tesis doctoral.El AGC es un mecanismo muy útil en un sistema de potencia multi-zona durante, sobre todo cuando hay variaciones en la carga o en la generación, ya que puede facilitar diversas tareas como: la restauración de frecuencia, control de potencia de líneas de enlace entre las áreas y el despacho económico de los sistemas de generación. En este contexto en AGC, dada su condición de control a alto nivel, generará las consignas para todos los elementos locales, tales como generadores o estaciones de conversión de energía, que están bajo el control de sus controladores locales.En esta tesis se proponen dos métodos diferentes para emular inercia virtual, los cuales se introducirán, se modelarán y se aplicarán al control de sistemas de potencia AC / DC interconectados. El primer método, que es uno de los métodos más comunes para la emulación de inercia en otras aplicaciones, es la técnica del control derivativo. En esta tesis, esta técnica se utiliza para llevar a cabo la emulación de inercia a alto nivel. Éste método de emulación de inercia se ha desarrollado para un sistema AGC de dos área que está interconectado mediante líneas de transmisión de CA / CC en paralelo. Sobre la base de la técnica propuesta, el efecto dinámico de la inercia emulada sobre el control de frecuencia y potencia activa será formulado y evaluado. Los efectos del retardo mediciones de frecuencia y los efectos del bucle de sincronización (PLL) también se consideran en el análisis y posterior ensayo. Las simulaciones llevadas a cabo demostrarán cómo la emulación de inercia virtual puede mejorar efectivamente el rendimiento del sistema de potencia.Dado que el primer método se basa en la derivación de la frecuencia de red, la medición de la frecuencia es muy importante y la aplicación de los métodos de medida de la misma, como las PLL, conlleva algunas limitaciones en la aplicación y respuesta del mismo. Por lo tanto, como una solución definitiva, se introduce el segundo método para la emulación de inercia virtual en esta tesis. El segundo método se basa en el concepto de energía síncrona virtual (VSP). El concepto de VSP, el cual permite simular los efectos dinámicos de las emulaciones de inercia por enlaces HVDC, se presentará y aplicará en sistemas de control de alto nivel, aplicándolo finalmente en el modelo AGC multi-zona. Tal y como se demostrará, mediante el uso de esta combinación propuesta en el modelo de AGC, el comportamiento dinámico de los sistemas muestra una mejora significativa. El control de bucle de potencia activa en el enlace HVDC basado en el VSP tiene una característica de segundo orden que genera una respuesta instantánea y permite controlar la amortiguación y la inercia en el sistema. La eficacia de concepto propuesto en las mejoras dinámicas se probará en plataformas de simulación que representarán un sistema multi-zona. Por último, se demostrará que la inercia virtual añade un grado de libertad adicional a la dinámica del sistema, lo cual ayuda a controlar el sobre pico así como el amortiguamiento en los transitorios en los enlaces HVDC.
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Ciotirca, Lavinia-Elena. "System design of a low-power three-axis underdamped MEMS accelerometer with simultaneous electrostatic damping control". Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/17939/7/CIOTIRCA_L.pdf.
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Recently, consumer electronics industry has known a spectacular growth that would have not been possible without pushing the integration barrier further and further. Micro Electro Mechanical Systems (MEMS) inertial sensors (e.g. accelerometers, gyroscopes) provide high performance, low power, low die cost solutions and are, nowadays, embedded in most consumer applications. In addition, the sensors fusion has become a new trend and combo sensors are gaining growing popularity since the co-integration of a three-axis MEMS accelerometer and a three-axis MEMS gyroscope provides complete navigation information. The resulting device is an Inertial measurement unit (IMU) able to sense multiple Degrees of Freedom (DoF). Nevertheless, the performances of the accelerometers and the gyroscopes are conditioned by the MEMS cavity pressure: the accelerometer is usually a damped system functioning under an atmospheric pressure while the gyroscope is a highly resonant system. Thus, to conceive a combo sensor, aunique low cavity pressure is required. The integration of both transducers within the same low pressure cavity necessitates a method to control and reduce the ringing phenomena by increasing the damping factor of the MEMS accelerometer. Consequently, the aim of the thesis is the design of an analog front-end interface able to sense and control an underdamped three-axis MEMSaccelerometer. This work proposes a novel closed-loop accelerometer interface achieving low power consumption The design challenge consists in finding a trade-off between the sampling frequency, the settling time and the circuit complexity since the sensor excitation plates are multiplexed between the measurement and the damping phases. In this context, a patenteddamping sequence (simultaneous damping) has been conceived to improve the damping efficiency over the state of the art approach performances (successive damping). To investigate the feasibility of the novel electrostatic damping control architecture, several mathematical models have been developed and the settling time method is used to assess the damping efficiency. Moreover, a new method that uses the multirate signal processing theory and allows the system stability study has been developed. This very method is used to conclude on the loop stability for a certain sampling frequency and loop gain value. Next, a 0.18μm CMOS implementation of the entire accelerometer signal chain is designed and validated.
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Rajagopal, Mohan Kumar. "Ultra low power wearable sleep diagnostic systems". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/38556.
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Sleep disorders are studied using sleep study systems called Polysomnography that records several biophysical parameters during sleep. However, these are bulky and are typically located in a medical facility where patient monitoring is costly and quite inefficient. Home-based portable systems solve these problems to an extent but they record only a minimal number of channels due to limited battery life. To surmount this, wearable sleep system are desired which need to be unobtrusive and have long battery life. In this thesis, a novel sleep system architecture is presented that enables the design of an ultra low power sleep diagnostic system. This architecture is capable of extending the recording time to 120 hours in a wearable system which is an order of magnitude improvement over commercial wearable systems that record for about 12 hours. This architecture has in effect reduced the average power consumption of 5-6 mW per channel to less than 500 uW per channel. This has been achieved by eliminating sampled data architecture, reducing the wireless transmission rate and by moving the sleep scoring to the sensors. Further, ultra low power instrumentation amplifiers have been designed to operate in weak inversion region to support this architecture. A 40 dB chopper-stabilised low power instrumentation amplifiers to process EEG were designed and tested to operate from 1.0 V consuming just 3.1 uW for peak mode operation with DC servo loop. A 50 dB non-EEG amplifier continuous-time bandpass amplifier with a consumption of 400 nW was also fabricated and tested. Both the amplifiers achieved a high CMRR and impedance that are critical for wearable systems. Combining these amplifiers with the novel architecture enables the design of an ultra low power sleep recording system. This reduces the size of the battery required and hence enables a truly wearable system.
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Goodman, James R. (James Ross). "Low power scalable encryption for wireless systems". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10646.
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Orfanidis, Charalampos. "Robustness in low power wide area networks". Licentiate thesis, Uppsala universitet, Avdelningen för datorteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-351481.
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During the past few years we have witnessed an emergence of Wide Area Networks in the Internet of Things area. There are several new technologies like LoRa, Wi-SUN, Sigfox, that offer long range communication and low power for low-bitrate applications. These new technologies enable new application scenarios, such as smart cities, smart agriculture, and many more. However, when these networks co-exist in the same frequency band, they may cause problems to each other since they are heterogeneous and independent. Therefore it is very likely to have frame collisions between the different networks. In this thesis we first explore how tolerant these networks are to Cross Technology Interference (CTI). CTI can be described as the interference from heterogeneous wireless technologies that share the same frequency band and is able to affect the robustness and reliability of the network. In particular, we select two of them, LoRa and Wi-SUN and carry out a series of experiments with real hardware using several configurations. In this way, we quantify the tolerance of cross technology interference of each network against the other as well as which configuration settings are important. The next thing we explored is how well channel sensing mechanisms can detect the other network technologies and how they can be improved. For exploring these aspects, we used the default Clear Channel Assessment (CCA) mechanism of Wi-SUN against LoRa interference and we evaluated how accurate it is. We also improved this mechanism in order to have higher accuracy detection against LoRa interference. Finally, we propose an architecture for WSNs which will enable flexible reconfiguration of the nodes. The idea is based on Software Defined Network (SDN) principles and could help on our case by reconfiguring a node in order to mitigate the cross-technology interference from other networks.
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Kaps, Jens-Peter E. "Cryptography for ultra-low power devices". Link to electronic dissertation, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-050406-152129/.
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Zou, Xiaolan. "Frequency and Damping Characteristics of Generators in Power Systems". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/81937.
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A power system stability is essential for maintaining the power system oscillation frequency within a small and acceptable interval around its nominal frequency. Hence, it is necessary to study and control the frequency for stable operation of a power system by knowing the characteristics within a power system. One approach is to understand the effectiveness of frequency and damping characteristics of generators in power systems. Hence, the simulation analysis of IEEE 118-bus power system is used for this study. The analysis includes theoretical analysis with a mathematical approach and simulation studies of swing equation to determine the characteristics of damped single-machine infinite bus, which is represented as a generator connects to a large network system with a small signal disturbance by line losses. Additionally, mathematical derivation of Prony analysis is presented in order to estimate the frequency and damping ratio of the simulation results. In the end, the results demonstrate that the frequency and damping characteristics of generators are highly dependent on the system inertia constant. Therefore, the higher inertia constant is a critical factor to ensure the system is more stable.Master of Science
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Pagone, Emanuele. "Advanced low carbon power systems - the advanced zero emissions power plant". Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/8293.
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The global warming issue is becoming more and more important in the public opinion, because its effects on everyday life of the entire mankind are starting to become appreciable. On the next (2009) December will be held in Copenhagen the fifteenth United Nations Climate Change Conference which is expected to be crucial for the future choices to deal with the anthropogenic greenhouse gases issue.
The power generation sector is one of the most important contributors to the emissions of greenhouse gases (of which the carbon dioxide is the main anthropogenic example), and it is facing in the last decades a problem that will exacerbate surely the already alarming effect on the global warming: the rapid increase of the world power demand.
For these reasons the carbon capture topic is gaining nowadays a lot of attention, especially in the industrial sector, since it will be a strategic field for the power generation in the short-medium term. In fact, it is really likely that will be introduced soon a so-called “cap and trade” system, with the trading of pollution licences related to the CO2 emissions, as the USA president Obama has recently proposed to the Congress. This option would turn out in a completely new scenario in the power generation sector with novel, cleaner concepts being economically more attractive than the conventional ones.
This project investigates the performance of a novel thermodynamic cycle with carbon capture, called Advanced Zero Emissions Power plant (AZEP), which has been analysed in the open literature just partially and superficially up to now. Since this project is part of a bigger one in which several carbon capture novel cycles options will be compared, the main objective is to provide a flexible, modular, modern computational tool, called eAZEP, developed from scratch. The second objective is the evaluation of the four main layouts of the AZEP concept as a stand alone power plant, assessing their inclination to be included in an unfired combined cycle featured with an Heat Recovery Steam Generator (HRSG). A final, third objective is the development of a routine for the off-design performance calculation to be included in on old pre-existing computational tool.
The original contribution of this work to the knowledge on the topic comprises
1. the conception of two new layouts for the AZEP cycle (the Post Expan-sion Heat exchanger layouts);
2. the performance evaluation of the long term potential for the power plant;
3. a sensitivity analysis of the thermodynamic concept.
The best suitable arrangements of the plant layout are identified together with the main parameters which influence their performance, both for the combined cycle perspective implementation and for the stand alone option.
Thanks to the flexibility of eAZEP will be easy to consider, in a future work, a pretty wide number of alternative concepts and investigate more cycle parameters in order to broaden the conclusions obtained in this work. Moreover the combined cycle off-design new routine must be debugged and validated.
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Park, Byeong-Ha. "A low-voltage, low-power, CMOS 900MHZ frequency synthesizer". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/16686.
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Westman, Martin y Ellen Nordén. "Modeling and comparative analysis of different grid-forming converter control concepts for very low inertia systems". Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414402.
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As renewable power from DC sources are constantly increasing their power generation share compared to the high inertia generators that provide robustness to the grid, the overall stability of the grid decreases. Grid forming converter could be the solution to this problem. This thesis includes a pre-study of grid forming control methods, implementation of the most promising and relevant methods in a generic PSCAD modeling environment for comparative analysis and for establishing pros and cons. Lastly, studying the system impact of each grid forming control method through small-signal stability and fault analysis. Four methods of grid forming were implemented and evaluated during the course of the thesis, which were: Droop control, Virtual Synchronous Generator control, Power Synchronization control and Synchronous Power control. All methods fulfilled the criteria for successful implementation with good results. For further developments, we would recommend Synchronous Power control and Virtual Synchronous Generator control for their development potential and operational width.
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Oberle, Michael. "Low power systems-on-chip for biomedical applications /". [S.l.] : [s.n.], 2002. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14509.
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Neagu, Mădălin. "Self-healing and secure low-power memory systems". Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/460893.
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The main objective of this thesis is to bring new contributions to the self-healing and secure systems domain. In particular, to develop a self-healing technique for memory systems and to increase security of memory systems, techniques which favor low-power consumption. In order to achieve the main objective, three major research objectives were proposed: design of an error detection and correction scheme for errors that occur in memory systems and integrate them in a memory system, design techniques to increase the security and data privacy of memory systems against different types of attacks and to combine the previous two into a single solution, in order to achieve a self-healing and secure low-power memory system. The low-power aspect of the proposed solutions and techniques is evaluated during design stage and afterwards through simulation. Also, the architectures are evaluated from several other points of view, such as error detecting and correcting performance, area and delay overhead, and security efficiency.
The first chapter contains a short introduction of the domain and subject of the thesis, current state of the art in this domain, proposed objectives and thesis organization.
The second chapter contains a unidirectional error detecting, correcting and localization scheme, which is used for the self-healing technique. The chapter begins with an introduction and motivation about error detecting and correcting codes and
their usage in memory systems and continues with a theoretical background. The chapter continues with the design of the proposed codes, which are explained in detail and illustrated through several figures. Then, they are analyzed from the following points of view: coding scheme, error localization, error correction and error escapes. For the latter three, metrics are defined, in order to evaluate the codes. Afterwards, the implementation of the proposed codes is exposed in several figures. Also, the usage of the codes is explained, as well as DRAM repair strategies. In the end of this chapter, the efficiency of the proposed codes is evaluated and exemplified. The evaluation process contains other metrics: speed and delay, area overhead, power consumption and code redundancy.
Chapter 3 contains a proposed scheme to increase security in memory systems against cold-boot attacks. The technique uses data scrambling, hence the chapter begins with a short theoretical background and a review of data scrambling methods. It continues with the proposed solution, which is based on using unique scrambling vectors in an interleaved way, and theoretical
performance and efficiency. The chapter ends with evaluation and experimental results for the proposed methodology.
Evaluations of area overhead, power consumption and access time are performed in the CACTI simulation tool and on a FPGA development board.
Chapter 4 approaches specific types of threats that can prevail in memory systems: simple and differential power or electromagnetic analysis attacks (SPEMA and DPEMA). The chapter begins with short introduction and motivation sections, and
continues with a theoretical background about possible threats. In the following section, SPEMA and DPEMA are explained and discussed in detail. Afterwards, the proposed solutions for mitigating SPEMA and DPEMA are exhibited, and ends with
evaluation and experimental results. An information leakage function is defined and used in evaluating the security efficiency of the solutions. The implementation costs are assessed with the use of the CACTI simulation tool, with respect to area and delay overhead, and power consumption.
The final chapter, 5, contains the conclusions of the work, scientific contributions and future research directions.
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Keeli, Anupama. "Low frequency transmission for remote power generating systems". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41190.
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The goal of this Masters Thesis research is to evaluate alternative transmission systems from remote wind farms to the main grid using low-frequency AC technology. Low frequency means a frequency lower than nominal frequency (60/50Hz). The low-frequency AC network can be connected to the power grid at major substations via cyclo-converters that provide a low-cost interconnection and synchronization with the main grid. Cyclo-converter technology is utilized to minimize costs which result in systems of 20/16.66 Hz (for 60/50Hz systems respectively). Low frequency transmission has the potential to provide an attractive solution in terms of economics and technical merits.
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Deo, Sonali. "Mesh Networking in Low Power Location Systems (Swarm)". Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-204558.
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Today, Internet of Things (IoT) is the driving force in making operations and processes smart. Indoor localization is such an application of IoT that has proven the potential of location awareness in countless scenarios, from mines to industries to even people. nanotron Technologies GmbH, based in Berlin, is one of the pioneers in low power location systems. nanotron's embedded location platform delivers location-awareness for safety and productivity solutions across industrial and consumer markets. The platform consists of chips, modules and software that enable precise real-time positioning and concurrent wireless communication. The ubiquitous proliferation of interoperable platforms is creating the locationaware Internet of Things. One of their product families is swarm. A swarm is a group of independent radios or nodes which facilitates the nodes to communicate with their immediate neighboring nodes to get each other’s positions. This position information is collected by one of the nodes (called gateway) and delivered to the host controller. However, the nodes need to be in range to communicate. The company wants to improve the range of communication and for that purpose; I am implementing a routing protocol with some additional changes for swarm, to allow out-of-range nodes to communicate via intermediate neighbors. This is called mesh networking which would result in so-called ‘mesh’ of nodes and would increase the range of swarm operation that could be beneficial in achieving uniform connectivity throughout large spaces without needing excessive number of gateways. This is of high importance because a node acting as gateway should be ‘awake’ all the time so that it can collect data efficiently, while the other nodes can beon power saving mode. Mesh networking will allow data collection even with fewer such gateways thereby being energy efficient while facilitating larger range of communication. This was made possible by adding the feature of allowing nodes to store messages for their neighbors in case they are asleep and wake up for the neighbors to transmit data. It is done using a schedule that is built and updated in addition to the routing protocol. The purpose of this thesis is to justify the implemented mesh routing protocol for swarm among all the other routing protocols available. It also focuses on the modifications and improvements that were devised to make the protocol tailored for how swarm works and to support Message Queuing Telemetry Transport (MQTT) on top of it, at a later stage. MQTT is a lightweight messaging protocol that provides resource-constrained network clients with a simple way to distribute information. It uses a publish/subscribe communication pattern and is used for machine-to-machine (M2M) communication and plays an important role in the Internet of Things. The implemented routing protocol also takes into consideration, the sleeping nodes, route maintenance through advertisements, hierarchical nature of mesh to make data collection more efficient, message formats keeping in mind the memory shortage, etc. The document gives a thorough overview of concepts, design implementation, improvements and tests to prove the importance of mesh networking in existing swarm.
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Eliasson, Jens. "Low-power design methodologies for embedded internet systems". Doctoral thesis, Luleå : Department of Computer Science and Electrical Engineering, Luleå University of Technology, 2008. http://epubl.ltu.se/1402-1544/2008/13/.
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TIWARI, ANURAG. "LOW POWER FPGA DESIGN TECHNIQUES FOR EMBEDDED SYSTEMS". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1109352677.
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Curto, Diogo Micael Repas. "Low-power, highly reliable IR range detection systems". Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/18663.
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Engenharia Eletrónica e TelecomunicaçõesA e ciência energética e cada vez mais uma preocupação de engenheiros e da população em geral. Em sistemas alimentados a baterias, esta preocupação torna-se mais evidente quando as pessoas interagem com estes diariamente. É então frustrante quando a uma bateria descarregada impossibilita a utilização destes sistemas. Um caso particular de sistemas que muitas vezes são alimentados por baterias são as torneiras automáticas. Estes sistemas necessitam de constante manutenção, quer devido a descarga das baterias, quer devido a falhas na deteção de presença. O princípio de funcionamento destes sistemas baseia-se essencialmente numa deteção por infravermelhos com recurso a um pequeno circuito de ativação de uma electro-válvula. Nesta dissertação foi proposta uma implementação semelhante com algumas alterações. Utilizaram-se técnicas de baixo consumo, algoritmos de deteção por infravermelhos e ainda recolha de energia para aumentar a duração da bateria. Ao usar um microcontrolador para executar as tarefas requeridas, foi adicionada ao sistema alguma inteligência. Foi ainda estudada a possibilidade de tornar o sistema completamente autónomo em termos de geração e consumo de energia. Embora a auto-su ciência não tenha sido alcançada, foram obtidos resultados importantes que poderão contribuir para melhorar o desempenho dos sistemas deste género.
Energy consumption is one of the major concerns amongst engineers and general population. In battery powered systems, when people interact with them in a daily basis, this concern is even more evident. It is frustrating when a depleted battery makes impossible its normal use. A particular case of a battery powered system is the automatic faucet. These need constant maintenance to replace dead batteries and even due to failures in presence detection. The working principle of these systems is essentially based in an infrared detection followed by a activation circuit of an electro-valve. In this dissertation a similar, with some changes, implementation was proposed. The use low-power techniques, infrared detection algorithms and energy harvesting to increase battery duration. By using a microcontroller to perform the required operations, some intelligence was given to the system. It was also veri ed the possibility to make the system self sustainable in therms of energy consumption and harvesting. Although self-sustainability was not achieved, several important results were obtained which can contribute to improve the performance of similar systems.
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Zamolo, Giovanni. "Architecture Designfor Compressed Sensing-Based Low Power Systems". Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-205031.
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In the Internet of Things scenario, a desirable feature of wireless sensors is the energy autonomy. However, the transmitter stage needs a great amount of energy to modulate and transmit the interested information. The power consumption can be improved using data compression algorithms: thereby, the total amount of the transmitted data is reduced, at expense of computational complexity. Alternatively, the recent compressed sensing technique can be applied on sparse signal instances, that is when most of the entries of the signal are zero or negligible in a fixed representation. Compressed sensing acquires directly the compressed information using nonadaptive measurements and it reconstructs the signal using non-linear algorithms. Each measurement contains information of the whole signal within a frame having a fixed length. As a result, the front-end architecture complexity is decreased at expense of the reconstruction. Moreover, thanks to the compressed sensing schemes, the sampling frequency can be far lower than the conventional Nyquist rate.This thesis investigates the applicability and the advantages of this technique for the electrocardiogram signal acquisition and for the ultra-wideband receiver; indeed, both signals can be considered sparse. The focus is on the reduction of the CS measurements for the impact on the hardware requirements. The optimal design parameters are defined for the CS-based systems, leading to a reduction of power consumption.During the simulations, a noisy electrocardiogram signal is acquired and reconstructed using different setups. More interest is made on the sparsity representation, the sampling frequency, and the compressed sensing frame length. The results show clearly that the signal is more sparse when it is represented using a Biorsplines wavelet function. Moreover, a trade-off between the sampling frequency and the signal length is needed and the performance is strongly influenced by the heart rate. It is convenient to use low sampling frequency, and high frame length: a valid performance is obtained using 350 Hz as sampling rate and frames of 1024 samples.Ultra-wideband technology is suitable for Internet of Things applications because the transmitter is easier to implement and it consumes less power if compared to the traditional narrow band transmitters. However, in fully digital receivers, the required Nyquist rate is high. In the ultra-wideband scenario, compressed sensing is an attractive solution in the receiver side for the capability of recovering the signal from a small number of measurements using sub-Nyquist sampling rate: using a parallel receiver the sampling rate can be one hundred times lower than the Nyquist one. Models of the ultra-wideband transmitter and receiver are developed and simulations are performed in different noisy scenarios. Therefore, practical design parameters are investigated, including the pulse bandwidth and the compressed sensing frame length. From the results, the 3.1 10.6 GHz band allows better performance. Moreover, this thesis suggests using short compressed sensing frame length in order to reduce the total amount of needed measurements.The thesis has been developed during an European exchange program in Stockholm, Sweden, at KTH, Royal Institute of Technology.Nello scenario dell’Internet of Things, una caratteristica auspicabile per i sensori wireless è l’autonomia energetica. Tuttavia, il trasmettitore richiede una considerevole quantità di energia per modulare e trasmettere l’informazione di interesse. Il consumo di potenza può essere ridotto utilizzando algoritmi di compressione dati: in tal modo, la quantità finale di dati trasmessi è ridotta a discapito però di una maggiore complessità computazionale. In alternativa, la recente tecnica del compressed sensing può essere applicata nel caso di segnali sparsi, ovvero nel caso in cui un segnale presenti per lo più valori nulli o trascurabili se rappresentato in una certa base. Tramite compressed sensing, viene acquisito il segnale già in forma compressa attraverso un certo numero di misure effettuate sul segnale diviso in frame di lunghezza prefissata; la ricostruzione avviene utilizzando algoritmi non lineari. Come risultato, l’architettura del front-end viene semplificata a discapito della ricostruzione. Inoltre, tramite gli schemi a compressed sensing, la frequenza di campionamento può essere molto minore di quella convenzionale, pari ad almeno due volte la banda del segnale.In questa tesi viene studiata l’applicabilità e i vantaggi di questa tecnica nel caso di acquisizione dei segnali elettrocardiogramma ed ultra-wideband, che possono essere entrambi considerati sparsi. L’interesse è nel ridurre il numero totale di misure in quanto influisce sui requisiti hardware. I parametri di progetto ottimali vengono quindi definiti per i due sistemi.Durante le simulazioni, un elettrocardiogramma rumoroso viene acquisito e successivamente ricostruito utilizzando diversi possibili setup. Particolare attenzione viene posta alla rappresentazione sparsa del segnale, alla frequenza di campionamento, e alla lunghezza del compressed sensing frame. I risultati mostrano chiaramente che il segnale ha una rappresentazione maggiormente sparsa se decomposto da una funzione wavelet Biorsplines. Inoltre, la frequenza cardiaca influenza le performance e pertanto un trade-off tra frequenza di campionamento e lunghezza del segnale risulta necessario. Risulta conveniente utilizzare basse frequenze di campionamento e frame lunghi, quali 350 Hz e 1024 campioni.La tecnologia ultra-wideband permette la produzione di trasmettitori più semplici e di minor consumo rispetto ai tradizionali sistemi a banda stretta, trovando quindi ottima applicazione nell’Internet of Things. Tuttavia, la necessaria frequenza di campionamento risulta essere troppo elevata nel caso di ricevitori completamente digitali. Invece, un ricevitore basato sul compressed sensing permette di ricostruire interamente il segnale a partire da un basso numero di misure effettuate a frequenza di campionamento inferiore, anche di cento volte. Sono stati per tanto sviluppati modelli del trasmettitore e del ricevitore mentre le simulazioni sono state svolte in vari scenari di rumore. I parametri di progetto studiati sono la larghezza di banda dell’impulso trasmesso e la dimensione del compressed sensing frame. Dai risultati, l’impulso con banda compresa fra i 3.1 e i 10.6 GHz è risultato essere il più indicato. Inoltre si consiglia di utilizzare un frame il più corto possibile al fine di ridurre il numero di misure.La tesi è stata sviluppata durante un programma di scambio Europeo a Stoccolma, Svezia, presso KTH, Royal Institute of Technology.
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Cottini, Nicola. "Ultra-Low-Power Vision Systems for Wireless Applications". Doctoral thesis, Università degli studi di Trento, 2012. https://hdl.handle.net/11572/367662.
Texto completoResumen
Custom CMOS vision sensors could offer large opportunities for ultra-low power applications, introducing novel visual computation paradigms, aimed at closing the large gap between vision technology and energy-autonomous sensory systems. Energy-aware vision could offer new opportunities to all those applications, such as security, safety, environmental monitoring and many others, where communication infrastructures and power supply are not available or too expensive to be provided.
This thesis aims at demonstrating this concept, exploiting the potential of an energy-aware vision sensor, developed at FBK, that extracts the spatial contrast and delivers compressed data. As a case study, a custom stereo-vision algorithm has been developed, taking advantage of the sensor characteristics, targeted to a lower complexity and reduced memory with respect to a standard stereo-vision processing. Under specific conditions, the proposed approach has proven to be very promising, although much work has still to be done both at sensor and at processing levels.The last part of this thesis is focused on the improvement of the custom sensor. A novel vision sensor architecture has been developed, which is based on a proprietary algorithm, developed by a partner of FBK and targeted to surveillance applications. The algorithm is based on adaptive temporal contrast extraction and is very suitable to be implemented at chip level. Although the output of the algorithm has strong similarities with the spatial contrast vision sensor, it relies on temporal contrast rather than spatial one, which is much more robust for event detection applications. A first prototype of ultra-low power adaptive temporal contrast vision sensor has been developed and tested.
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Cottini, Nicola. "Ultra-Low-Power Vision Systems for Wireless Applications". Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/778/1/PhDThesisCottini.pdf.
Texto completoResumen
Custom CMOS vision sensors could offer large opportunities for ultra-low power applications, introducing novel visual computation paradigms, aimed at closing the large gap between vision technology and energy-autonomous sensory systems. Energy-aware vision could offer new opportunities to all those applications, such as security, safety, environmental monitoring and many others, where communication infrastructures and power supply are not available or too expensive to be provided.
This thesis aims at demonstrating this concept, exploiting the potential of an energy-aware vision sensor, developed at FBK, that extracts the spatial contrast and delivers compressed data. As a case study, a custom stereo-vision algorithm has been developed, taking advantage of the sensor characteristics, targeted to a lower complexity and reduced memory with respect to a standard stereo-vision processing. Under specific conditions, the proposed approach has proven to be very promising, although much work has still to be done both at sensor and at processing levels.The last part of this thesis is focused on the improvement of the custom sensor. A novel vision sensor architecture has been developed, which is based on a proprietary algorithm, developed by a partner of FBK and targeted to surveillance applications. The algorithm is based on adaptive temporal contrast extraction and is very suitable to be implemented at chip level. Although the output of the algorithm has strong similarities with the spatial contrast vision sensor, it relies on temporal contrast rather than spatial one, which is much more robust for event detection applications. A first prototype of ultra-low power adaptive temporal contrast vision sensor has been developed and tested.
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Wang, Yan. "Low power design for wireless communication system /". View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20WANG.
Texto completoResumen
Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 171-179). Also available in electronic version. Access restricted to campus users.
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Barbosa, Peter Mantovanelli. "Three-Phase Power Factor Correction Circuits for Low-Cost Distributed Power Systems". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/28651.
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Front-end converters with power factor correction (PFC) capability are widely used in distributed power systems (DPSs). Most of the front-end converters are implemented using a two-stage approach, which consists of a PFC stage followed by a DC/DC converter. The purpose of the front-end converter is to regulate the DC output voltage, supply all the load converters connected to the distributed bus, guarantee current sharing, and charge a bank of batteries to provide backup energy when the power grid breaks down.
One of the main concerns of the power supply industry is to obtain a front-end converter with a low-cost PFC stage, while still complying with required harmonic standards, especially for high-power three-phase applications. Having this statement in mind, the main objective of this dissertation is to study front-end converters for DPS applications with PFC to meet harmonic standards, while still maintaining low cost and performance indices.
To realize the many aforementioned objectives, this dissertation is divided into two main parts: (1) two-stage front-end converters suitable for telecom applications, and (2) single-stage low-cost AC/DC converters suitable for mainframe computers and server applications. The use of discontinuous conduction mode (DCM) boost rectifiers is extensively explored to achieve simplicity, while reducing the cost for DPS applications. Interleaving of DCM boost rectifiers is also explored as an alternative approach to further reduce the system cost by reducing the filtering requirements. All the solutions discussed are implemented for 3kW applications, while 6kW is obtained by interleaving two converters.Ph. D.
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Häggblom, Johan y Jonathan Jerner. "Photovoltaic Power Production and Energy Storage Systems in Low-Voltage Power Grids". Thesis, Linköpings universitet, Fordonssystem, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-156875.
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In recent years, photovoltaic (PV) power production have seen an increase and the PV power systems are often located in the distribution grids close to the consumers. Since the distributions grids rarely are designed for power production, investigation of its effects is needed. It is seen in this thesis that PV power production will cause voltages to rise, potentially to levels exceeding the limits that grid owners have to abide by. A model of a distribution grid is developed in MathWorks MATLAB. The model contains a transformer, cables, households, energy storage systems (ESS:s) and photovoltaic power systems. The system is simulated by implementing a numerical Forward Backward Sweep Method, solving for powers, currents and voltages in the grid. PV power systems are added in different configurations along with different configurations of ESS:s. The results are analysed, primarily concerning voltages and voltage limits. It is concluded that addition of PV power production in the distribution grid affects voltages, more or less depending on where in the grid the systems are placed and what peak power they have. It is also concluded that having energy storage systems in the grid, changing the power factor of the inverter for the PV systems or lowering the transformer secondary-side voltage can bring the voltages down.På senare tid har det skett en ökning i antalet solcellsanläggningar som installeras i elnätet och dessa är ofta placerade i distributionsnäten nära hushållen. Eftersom distributionsnäten sällan är dimensionerade för produktion så behöver man utreda effekten av det. I det här arbetet visas det att solcellsproduktion kommer att öka spänningen i elnätet, potentiellt så mycket att de gränser elnätsägarna måste hålla nätet inom överstigs. En modell över lågspänningsnätet skapas i MathWorks MATLAB. Modellen innehåller transformator, kablar, hushåll, energilager och solcellsanläggningar. Systemet simuleras med hjälp av en numerisk Forward Backward Sweep-lösare som beräknar effekter, strömmar och spänningar i elnätet. Solcellanläggningarna placeras ut i elnätet i olika konfigurationer tillsammans med olika konfigurationer av energilager. Resultaten från simuleringarna analyseras främst med avseende på spänningen i elnätet utifrån dess gränser. De slutsatser som dras i arbetet är att solcellsproduktion kommer att påverka spänningen, mycket beroende på var i elnätet anläggningarna placeras och storleken hos dem. Det visas också att energilager, justering av effektfaktor hos solcellsanläggningarna eller en spänningssänkning på transformatorns lågspänningssida kan få ner spänningen i elnätet.
LiTH-ISY-EX--19/5194--SE
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Larsson, Anders. "On high-frequency distortion in low-voltage power systems". Doctoral thesis, Luleå tekniska universitet, Energivetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26658.
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Power quality is a subject that has received a lot of attention during the last 10 to 20 years, both in industry and in academia. Power quality concerns interaction between the power grid and its customers and between the power grid and equipment connected to it, reflected in voltages and currents. Research and other developments in this area have to a great extent concentrated on relatively slow and low-frequency phenomena, with the main emphasis being on voltage dips (reductions in voltage magnitude with duration between about 50 ms and several seconds) and low-frequency harmonics (waveform distortion by frequency components up to about 2 kHz). These phenomena are reasonably well understood and several standards cover the area. For higher-frequency phenomena, above 2 kHz, there is no such general understanding, nor is there anything close to a complete set of standards covering this area. Modern energy efficient equipment connected to the grid, like fluorescent lamps but also solar panels, often uses switching technology, with switching frequencies that can range from a couple of kHz up to several hundreds of kHz. The grid is also used for communication of e.g. meter readings, system controls etc. This so-called power-line communication is using the same frequency range. The main frequency range of interest for this thesis has been the range from 2 to 150 kHz. There are two completely different measurement methods covering this frequency range: time-domain based and frequency-domain based. Time domain based measurements are used throughout the thesis. This gives an opportunity to choose between different analysing tools where among others the joint time-frequency domain has shown to be a useful tool for describing waveform distortion in our frequency range of interest. The majority of the measurements presented in this thesis have been directed towards fluorescent light powered by high frequency ballasts. This type of load has been, due to stringent harmonic limits, one of the first to use a more advanced switching technology called active power factor correction. This technique is also getting more frequently used in other small-power equipment, like computers. Installations of lights in stores etc. normally contain a large number of ballast connected together and the interaction is of importance, for example for setting emission and immunity standards. The measurements on ballasts presented in this work have shown that distortion in the frequency rage 2-150 kHz comes in three types: narrowband distortion; wideband distortion; and recurrent oscillations. The recurrent oscillations are a new type of powerquality disturbance that had not been recognized as such before. The measurements further have shown that the three types of distortion spread in a completely different way from the individual devices to the grid. This knowledge is essential for the setting of emission requirements on energy-efficient equipment.Godkänd; 2011; 20110216 (andlar); DISPUTATION Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Anders Larsson Ämnesområde: Energiteknik/Energy Engineering Avhandling: On High-Frequency Distortion in Low-Voltage Power Systems Opponent: Adj. professor Lars Gertmar, Institutionen för industriell elektroteknik och automation, Lunds universitet Ordförande: Professor Math Bollen, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Onsdag den 23 mars 2011, kl 10.00 Plats: Hörsal A, Campus Skellefteå, Luleå tekniska universitet
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Arfin, Scott K. (Scott Kenneth). "Low power circuits and systems for wireless neural stimulation". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65999.
Texto completoResumen
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 155-161).
Electrical stimulation of tissues is an increasingly valuable tool for treating a variety of disorders, with applications including cardiac pacemakers, cochlear implants, visual prostheses, deep brain stimulators, spinal cord stimulators, and muscle stimulators. Brain implants for paralysis treatments are increasingly providing sensory feedback via neural stimulation. Within the field of neuroscience, the perturbation of neuronal circuits wirelessly in untethered, freely-behaving animals is of particular importance. In implantable systems, power consumption is often the limiting factor in determining battery or power coil size, cost, and level of tissue heating, with stimulation circuitry typically dominating the power budget of the entire implant. Thus, there is strong motivation to improve the energy efficiency of implantable electrical stimulators. In this thesis, I present two examples of low-power tissue stimulators. The first type is a wireless, low-power neural stimulation system for use in freely behaving animals. The system consists of an external transmitter and a miniature, implantable wireless receiver-and-stimulator utilizing a custom integrated chip built in a standard 0.5 ptm CMOS process. Low power design permits 12 days of continuous experimentation from a 5 mAh battery, extended by an automatic sleep mode that reduces standby power consumption by 2.5x. To test this device, bipolar stimulating electrodes were implanted into the songbird motor nucleus HVC of zebra finches. Single-neuron recordings revealed that wireless stimulation of HVC led to a strong increase of spiking activity in its downstream target, the robust nucleus of the arcopallium (RA). When this device was used to deliver biphasic pulses of current randomly during singing, singing activity was prematurely terminated in all birds tested. The second stimulator I present is a novel, energy-efficient electrode stimulator with feedback current regulation. This stimulator uses inductive storage and recycling of energy based on a dynamic power supply to drive an electrode in an adiabatic fashion such that energy consumption is minimized. Since there are no explicit current sources or current limiters, wasteful energy dissipation across such elements is naturally avoided. The stimulator also utilizes a shunt current-sensor to monitor and regulate the current through the electrode via feedback, thus enabling flexible and safe stimulation. The dynamic power supply allows efficient transfer of energy both to and from the electrode, and is based on a DC-DC converter topology that is used in a bidirectional fashion. In an exemplary electrode implementation, I show how the stimulator combines the efficiency of voltage control and the safety and accuracy of current control in a single low-power integrated-circuit built in a standard 0.35 pm CMOS process. I also perform a theoretical analysis of the energy efficiency that is in accord with experimental measurements. In its current proof-of-concept implementation, this stimulator achieves a 2x-3x reduction in energy consumption as compared to a conventional current-source-based stimulator operating from a fixed power supply.
by Scott Kenneth Arfin.
Ph.D.
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He, Qing Ph D. Massachusetts Institute of Technology. "An architecture for low-power voice-command recognition systems". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105574.
Texto completoResumen
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 149-157).
The advancements in fields such as machine-learning have allowed for a growing number of applications seeking to exploit learning methods. Many such applications involve complex algorithms working over high-dimensional features and are implemented in large scale systems where power and other resources are abundant. With emerging interest in embedded applications, nano-scale systems, and mobile devices, which are power and computation constrained, there is a rising need to find simple, low-power solutions for common applications such as voice activation. This thesis develops an ultra-low-power system architecture for voice-command recognition applications. It optimizes system resources by exploiting compact representations of the signal features and extracting them with efficient analog front-ends. The front-end performs feature pre-selection such that only a subset of all available features are chosen and extracted. Two variations of front-end feature extraction design are developed, for the applications of text-dependent speaker-verification and user-independent command recognition, respectively. For speaker-verification, the features are selected with knowledge of the speaker's fundamental frequency and are adapted based on the noise spectrum. The back-end algorithm, supporting adaptive feature selection, is a weighted dynamic time warping algorithm that removes signal misalignments and mitigates speech rate variations while preserving the signal envelope. In the case of user-independent command recognition, a universal set of features are selected without using speaker-specific information. The back-end classifier is enabled by a novel multi-band deep neural network model that processes only the selected features at each decision. In experiments, the proposed systems achieve improved accuracy with noise robustness using significantly less power consumption and computation than existing systems. Components of the front- and back-ends have been implemented in hardware, and the end-to-end system power consumption is kept under a few hundred [mu]Ws.
by Qing He.
Ph. D.
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Weatherall, James Neil. "An embedded ubiquitous control architecture for low power systems". Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620632.
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Bles, Christopher Kenneth. "Vertically integrated modules for low power embedded sensor systems". College Park, Md.: University of Maryland, 2006. http://hdl.handle.net/1903/3945.
Texto completoResumen
Thesis (M.S.) -- University of Maryland, College Park, 2006.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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CICCIA, SIMONE. "Reconfigurable Antenna Systems: Platform implementation and low-power matters". Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2696507.
Texto completoResumen
Antennas are a necessary and often critical component of all wireless systems, of which they share the ever-increasing complexity and the challenges of present and emerging trends. 5G, massive low-orbit satellite architectures (e.g. OneWeb), industry 4.0, Internet of Things (IoT), satcom on-the-move, Advanced Driver Assistance Systems (ADAS) and Autonomous Vehicles, all call for highly flexible systems, and antenna reconfigurability is an enabling part of these advances. The terminal segment is particularly crucial in this sense, encompassing both very compact antennas or low-profile antennas, all with various adaptability/reconfigurability requirements. This thesis work has dealt with hardware implementation issues of Radio Frequency (RF) antenna reconfigurability, and in particular with low-power General Purpose Platforms (GPP); the work has encompassed Software Defined Radio (SDR) implementation, as well as embedded low-power platforms (in particular on STM32 Nucleo family of micro-controller). The hardware-software platform work has been complemented with design and fabrication of reconfigurable antennas in standard technology, and the resulting systems tested. The selected antenna technology was antenna array with continuously steerable beam, controlled by voltage-driven phase shifting circuits. Applications included notably Wireless Sensor Network (WSN) deployed in the Italian scientific mission in Antarctica, in a traffic-monitoring case study (EU H2020 project), and into an innovative Global Navigation Satellite Systems (GNSS) antenna concept (patent application submitted). The SDR implementation focused on a low-cost and low-power Software-defined radio open-source platform with IEEE 802.11 a/g/p wireless communication capability. In a second embodiment, the flexibility of the SDR paradigm has been traded off to avoid the power consumption associated to the relevant operating system. Application field of reconfigurable antenna is, however, not limited to a better management of the energy consumption. The analysis has also been extended to satellites positioning application. A novel beamforming method has presented demonstrating improvements in the quality of signals received from satellites. Regarding those who deal with positioning algorithms, this advancement help improving precision on the estimated position.
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Erbes, Andreja. "MEMS resonators for low power wireless communications and timing applications". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708912.
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Wilson, John Martin. "A low power HF communication system". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/a-low-power-hf-communication-system(d62d1ee1-d71f-48d2-a139-6d01265fa53d).html.
Texto completoResumen
The HF band of radio frequencies, from 3-30 MHz, is unique in its property that it is refracted by the ionosphere. This property allows long distance radio telecommunications around the world without requiring infrastructure. High frequency (HF) communication has been largely superseded by satellite and cellular technologies for day-to-day communications, due to the tight bandwidth constraints and technical difficulties inherent in using it. However there is still a need for HF communications devices where existing infrastructure is not available, such as in remote or polar locations, or in emergency situations due to natural disasters. This research is aimed at the development of an asymmetric HF communications link, with a battery-powered remote unit that transmits a small amount of data to a mains-powered base station. New technologies are identified and evaluated for use in the link, with the aim of reducing the power requirements of the remote unit. Error correction techniques are investigated. Low-density parity check (LDPC) codes, which are powerful codes used for forward error correction, are suggested for use in the link. Quasi-cyclic LDPC codes allow the low-power transmitter unit to use a computationally simple encoder based on feedback shift registers for generating the LDPC block codes cheaply. Semi-blind LDPC turbo equalisation is a powerful technique that can be used at the base station which utilises the structure of the LDPC code to encode the data stream. This equalises a received signal with a minimal amount of training data required, reducing the duty cycle of the remote unit. Hybrid automatic repeat request (HARQ) techniques are also investigated, which increase the throughput of a link when data repeats are required. A novel HARQ techniquewas created and proven to increase throughput in links with noise. As the proposed system may be deployed in remote locations, or locations where it might be difficult or undesirable to erect a proper HF antenna, a selection of buried antennas are characterised. A design for a remote unit is suggested. This unit was manufactured and used to test the capability of inexpensive, low power hardware to implement the proposed remote unit algorithms.
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Deiss, Armin Georg. "A low power 200MHz receiver for wireless hearing aid systems /". Zürich : [s.n.], 2002. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14532.
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Halvorsrød, Thomas Moe. "On Low Power, Analog Modules for Medical Ultrasound Imaging Systems". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11204.
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Abdulghani, Amir M. "Compressive sensing theory for low power wireless EEG communication systems". Thesis, Imperial College London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540629.
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Erdogan, Ahmet Teyfik. "Low power FIR filter implementations for VLSI-based DSP systems". Thesis, Cardiff University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312049.
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Eljamaly, Omar. "Low-power wireless body area sensor network communication sub-systems". Thesis, University of Surrey, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479515.
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Noraky, James. "Algorithms and systems for low power time-of-flight imaging". Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127029.
Texto completoResumen
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 151-158).
Depth sensing is useful for many emerging applications that range from augmented reality to robotic navigation. Time-of-flight (ToF) cameras are appealing depth sensors because they obtain dense depth maps with minimal latency. However, for mobile and embedded devices, ToF cameras, which obtain depth by emitting light and estimating its roundtrip time, can be power-hungry and limit the battery life of the underlying device. To reduce the power for depth sensing, we present algorithms to address two scenarios. For applications where RGB images are concurrently collected, we present algorithms that reduce the usage of the ToF camera and estimate new depth maps without illuminating the scene. We exploit the fact that many applications operate in nearly rigid environments, and our algorithms use the sparse correspondences across the consecutive RGB images to estimate the rigid motion and use it to obtain new depth maps.
Our techniques can reduce the usage of the ToF camera by up to 85%, while still estimating new depth maps within 1% of the ground truth for rigid scenes and 1.74% for dynamic ones. When only the data from a ToF camera is used, we propose algorithms that reduce the overall amount of light that the ToF camera emits to obtain accurate depth maps. Our techniques use the rigid motions in the scene, which can be estimated using the infrared images that a ToF camera obtains, to temporally mitigate the impact of noise. We show that our approaches can reduce the amount of emitted light by up to 81% and the mean relative error of the depth maps by up to 64%. Our algorithms are all computationally efficient and can obtain dense depth maps at up to real-time on standard and embedded computing platforms.
Compared to applications that just use the ToF camera and incur the cost of higher sensor power and to those that estimate depth entirely using RGB images, which are inaccurate and have high latency, our algorithms enable energy-efficient, accurate, and low latency depth sensing for many emerging applications.
by James Noraky.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Hasan, Md Raqibul. "Memristor Based Low Power High Throughput Circuits and Systems Design". University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1459522347.
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