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Dissertations / Theses on the topic 'Power Electronics and energy conversion'
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1
Ghosh, Suvradip. "Energy and data conversion circuits for low power sensory systems." Thesis, University of Missouri - Kansas City, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3610195.
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This dissertation focuses on the problem of increasing the lifetime of wireless sensors. This problem is addressed from two different angles: energy harvesting and data compression. Energy harvesting enables a sensor to extract energy from its environment and use it to power itself or recharge its batteries. Data compression, on the other hand, allows a sensor to save energy by reducing the radio transmission bandwidth.
This dissertation proposes a fractal-based photodiode fabricated on standard CMOS process as an energy harvesting device with increased efficiency. Experiments show that, the fractal based photodiodes are 6% more efficient compared to the conventional square shaped photodiode. The fractal shape photodiode has more perimeter-to-area ratio which increases the lateral response, improving its efficiency.
With increased efficiency, more current is generated but the open-circuit voltage still remains low (0.3V–0.45V depending on illumination condition). These voltages have to be boosted up to higher values if they are going to be used to power up any sensory circuit or recharge a battery. We propose a switched-inductor DC-DC converter to boost the low voltage of the photodiodes to higher voltages. The proposed circuit uses two on-chip switches and two off-chip Components: an inductor and a capacitor. Experiments show a voltage up to 2.81V can be generated from a single photodiode of 1mm2 area. The voltage booster circuit achieved a conversion efficiency of 59%.
Data compression was also explored in an effort to reduce energy consumption during radio transmission. An analog-to-digital converter (ADC), which can jointly perform the tasks of digital conversion and entropy encoding, has also been proposed in this dissertation. The joint data conversion/compression help savings in area and power resources, making it suitable for on-sensor compression. The proposed converter combines a cyclic converter architecture and Golomb-Rice entropy encoder. The converter hardware design is based on current-mode circuits and it was fabricated on a 0.5 μm CMOS process and tested. Experiment results show a lossless compression ratio of 1.52 and a near-lossless compression of 5.2 can be achieved for 32 × 32 pixel image.
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Chen, Zhe. "Advanced wind energy convertors using electronic power conversion." Thesis, Durham University, 1997. http://etheses.dur.ac.uk/1632/.
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Baltierrez, Jason. "Multiple Input, Single Output DC-DC Conversion Stage for DC House." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2028.
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n this thesis project, a proposed architecture for the multiple input, single output conversion stage for the DC House was designed, simulated, and tested. This architecture allows for multiple different input sources to be used to create a single higher power output source. The design uses a DC-DC boost converter with a parallelable output which has been demonstrated to allow increased total output power as a function of the number of input sources available. The parallelable output has been shown to distribute load amongst the input sources relatively closely to optimize the system. This approach is also desirable since it allows for flexibility in multiple configurations it can be used in. The design was tested using hardware and data results show the performance met and exceeded the needs of the DC House project. Data was taken for configuration with 1, 2, 3, and 4 input sources providing greater than 600W of total output power at an efficiency of greater than 92%. This architecture demonstrates the possibility of expanding the total available power for a single output in proportion to the number of available input sources.
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Todeschini, Grazia. "Wind Energy Conversion Systems based on DFIG Technology used as Active Filters: Steady-State and Transient Analysis." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/97.
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This thesis deals with the performance of a Wind Energy Conversion System operating as a power generator and Active Filter simultaneously. As a power generator, the Wind Energy Conversion System converts wind energy into electric energy; as an Active Filter, it sinks the harmonic currents injected by Non-Linear Loads connected at the same feeder. Three control systems are developed to ensure the described operation; a specific study regarding the compensation of the triplen harmonics is carried out; Doubly-Fed Induction Generator derating is defined; and an engineering economic analysis is performed to determine the profitability of the proposed operation. The Wind Energy Conversion System performance as generator and Active Filter has been studied for steady-state analysis, fast transients and low transients. It is concluded that the proposed control systems allow operating the Wind Energy Conversion System as power generator and harmonic compensator both during steady state and transient operation; the described operation causes power loss increase and voltage distortion that determine the choice of the component and require system derating.
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Esmaili, Gholamreza. "Application of advanced power electronics in renewable energy sources and hybrid generating systems." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1141850833.
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Elamalayil, Soman Deepak. "Multilevel Power Converters with Smart Control for Wave Energy Conversion." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-332730.
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The main focus of this thesis is on the power electronic converter system challenges associated with the grid integration of variable-renewable-energy (VRE) sources like wave, marine current, tidal, wind, solar etc. Wave energy conversion with grid integration is used as the key reference, considering its high energy potential to support the future clean energy requirements and due the availability of a test facility at Uppsala University. The emphasis is on the DC-link power conditioning and grid coupling of direct driven wave energy converters (DDWECs). The DDWEC reflects the random nature of its input energy to its output voltage wave shape. Thereby, it demands for intelligent power conversion techniques to facilitate the grid connection. One option is to improve and adapt an already existing, simple and reliable multilevel power converter technology, using smart control strategies. The proposed WECs to grid interconnection system consists of uncontrolled three-phase rectifiers, three-level boost converter(TLBC) or three-level buck-boost converter (TLBBC) and a three-level neutral point clamped (TLNPC) inverter. A new method for pulse delay control for the active balancing of DC-link capacitor voltages by using TLBC/TLBBC is presented. Duty-ratio and pulse delay control methods are combined for obtaining better voltage regulation at the DC-link and for achieving higher controllability range. The classic voltage balancing problem of the NPC inverter input, is solved efficiently using the above technique. A synchronous current compensator is used for the NPC inverter based grid coupling. Various results from both simulation and hardware testing show that the required power conditioning and power flow control can be obtained from the proposed multilevel multistage converter system. The entire control strategies are implemented in Xilinx Virtex 5 FPGA, inside National Instruments’ CompactRIO system using LabVIEW. A contour based dead-time harmonic analysis method for TLNPC and the possibilities of having various interconnection strategies of WEC-rectifier units to complement the power converter efforts for stabilizing the DC-link, are also presented. An advanced future AC2AC direct power converter system based on Modular multilevel converter (MMC) structure developed at Siemens AG is presented briefly to demonstrate the future trends in this area.
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Rahimi, Arian. "Design And Implementation Of Low Power Interface Electronics For Vibration-based Electromagnetic Energy Harvesters." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613820/index.pdf.
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For many years batteries have been used as the main power sources for portable electronic devices. However, the rate of scaling in integrated circuits and micro-electro-mechanical systems (MEMS) has been much higher than that of the batteries technology. Therefore, a need to replace these temporary energy reservoirs with small sized continuously charged energy supply units has emerged. These units, named as energy harvesters, use several types of ambient energy sources such as heat, light, and vibration to provide energy to intelligent systems such as sensor nodes. Among the available types, vibration based electromagnetic (EM) energy harvesters are particularly interesting because of their simple structure and suitability for operation at low frequency values (<10 Hz), where most vibrations exits. However, since the generated EM power and voltage is relatively low at low frequencies, high performance interface electronics is required for efficiently transferring the generated power from the harvester to the load to be supplied. The aim of this study is to design low power and efficient interface electronics to convert the low voltage and low power generated signals of the EM energy harvesters to DC to be usable by a real application. The most critical part of such interface electronics is the AC/DC converter, since all the other blocks such as DC/DC converters, power managements units, etc. rely on the rectified voltage generated by this block. Due to this, several state-of-the-art rectifier structures suitable for energy harvesting applications have been studied. Most of the previously proposed rectifiers have low conversion efficiency due to the high voltage drop across the utilized diodes. In this study, two rectifier structures are proposed: one is a new passive rectifier using the Boot Strapping technique for reducing the diode turn-on voltage values
the other structure is a comparator-based ultra low power active rectifier. The proposed structures and some of the previously reported designs have been implemented in X-FAB 0.35 µ
m standard CMOS process. The autonomous energy harvesting systems are then realized by integrating the developed ASICs and the previously proposed EM energy harvester modules developed in our research group, and these systems have been characterized under different electromechanical excitation conditions. In this thesis, five different systems utilizing different circuits and energy harvesting modules have been presented. Among these, the system utilizing the novel Boot Strap Rectifier is implemented within a volume of 21 cm3, and delivers 1.6 V, 80 µ
A (128 µ
W) DC power to a load at a vibration frequency of only 2 Hz and 72 mg peak acceleration. The maximum overall power density of the system operating at 2 Hz is 6.1 µ
W/cm3, which is the highest reported value in the literature at this operation frequency. Also, the operation of a commercially available temperature sensor using the provided power of the energy harvester has been shown. Another system utilizing the comparator-based active rectifier implemented with a volume of 16 cm3, has a dual rail output and is able to drive a 1.46 V, 37 µ
A load with a maximum power density of 6.03 µ
W/cm3, operating at 8 Hz. Furthermore, a signal conditioning system for EM energy harvesting has also been designed and simulated in TSMC 90 nm CMOS process. The proposed ASIC includes a highly efficient AC-DC converter as well as a power processing unit which steps up and regulates the converted DC voltages using an on-chip DC/DC converter and a sub-threshold voltage regulator with an ultra low power management unit. The total power consumption on the totally passive IC is less than 5 µ
W, which makes it suitable for next generation MEMS-based EM energy harvesters. In the frame of this study, high efficiency CMOS rectifier ICs have been designed and tested together with several vibration based EM energy harvester modules. The results show that the best efficiency and power density values have been achieved with the proposed energy harvesting systems, within the low frequency range, to the best of our knowledge. It is also shown that further improvement of the results is possible with the utilization of a more advanced CMOS technology.
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Liddle, Marshall. "Towards a better wind power map of Nevada." abstract and full text PDF (free order & download UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453599.
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Davenport, Tattiana Karina Coleman. "Three-Phase Generation Using Reactive Networks." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1345.
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Household appliances utilize single-phase motors to perform everyday jobs whether it is to run a fan in an air conditioner or the compressor in a refrigerator. With the movement of the world going “green” and trying to make everything more efficient, it is a logical step to start with the items that we use every day. This can be done by replacing single-phase motors with three-phase motors in household appliances. Three-phase motors are 14% more efficient than single-phase motors when running at full load and typically cost less over a large range of sizes [1]. One major downside of incorporating three-phase motors in household appliance is that three-phase power is not readily available in homes. With the motor replacement, a single to three-phase converter is necessary to convert the single-phase wall power into the required three-phase input of the motor. One option is active conversion, which uses switches and introduces different stages that produce power loss [2]. An alternative solution is passive conversion that utilizes the resistances within the motor windings along with additional capacitors and inductors, which in theory are lossless. This study focuses on three different single to three-phase passive converters to run both wye and delta-connected three-phase induction motors, and a possible third winding configuration that utilizes one of the three converters. There will be an emphasis on proving the equivalency of two converters, one proposed by Stuart Marinus and Michel Malengret [11] and the other by Otto Smith [12]. Sensitivity analysis is performed to study the effects of variation of torque and converter component tolerances on the system.
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Samir, Karmacharya. "Modelling and control of micro-combined heat and power (CHP) to optimise energy conversion and support power distribution networks." Thesis, Northumbria University, 2013. http://nrl.northumbria.ac.uk/21424/.
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Climate change and continuously increasing energy prices have driven the need for low carbon and renewable energy technologies from different sectors, including the domestic sector, by installing higher energy efficiency technologies. One of these technologies is the Stirling engine based micro-combined heat and power (CHP) which has the potential to achieve lower overall carbon emissions by generating both heat and electricity locally. Its successful implementation to meet the energy demands (thermal and electrical) throughout the year depends on several factors such as the size and type of building and demand profiles. In addition, the deployment of large number of micro-CHPs may have significant impact on the performance of the power distribution networks.
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Filho, Esio Eloi dos Santos. "Conversor CA-CC com capacitor comutado com alto fator de potÃncia para o acionamento de LEDs de potÃncia." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15719.
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FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgicoEste trabalho apresenta o estudo e desenvolvimento de um conversor com capacitor comutado para o acionamento de diodos emissores de luz (LED) de potÃncia, alimentado a partir da rede elÃtrica de baixa tensÃo. Diferente dos conversores tradicionais de corrente contÃnua, a corrente direcionada aos LEDs à fornecida por meio de capacitores comutados. O conversor proposto ainda difere dos conversores convencionais baseados no capacitor comutado, pois utiliza uma indutÃncia para evitar o carregamento e o descarregamento forÃado dos capacitores comutados, reduzindo os picos de corrente e a emissÃo eletromagnÃtica do circuito. O conversor proposto apresenta correÃÃo do fator de potÃncia inerente e pode proporcionar isolaÃÃo atravÃs de capacitores. TambÃm se propÃe a utilizaÃÃo de duas topologias de filtro LC sintonizado (filtro LC paralelo e LC sÃrie) para reduzir a ondulaÃÃo da corrente de saÃda do conversor, evitando a utilizaÃÃo de capacitores eletrolÃticos. Um estudo teÃrico do conversor proposto à realizado atravÃs das anÃlises qualitativa e quantitativa, nas quais sÃo determinados os esforÃos de tensÃo e corrente nos principais componentes e tambÃm as perdas nos componentes do conversor. Um protÃtipo de laboratÃrio de 51 W com tensÃo de entrada eficaz de 220 V à projetado e testado experimentalmente. Os resultados de simulaÃÃo e experimentais sÃo apresentados e discutidos, demostrando a viabilidade tÃcnica do conversor proposto. Para a condiÃÃo de carga nominal o conversor apresenta rendimento de 75,3% e fator de potÃncia de entrada de 0,996, respeitando os limites de emissÃo de harmÃnicos determinados pela norma IEC 61000-3-2. Com a aplicaÃÃo do filtro LC paralelo, conectado em sÃrie com os LEDs, obtÃm-se ondulaÃÃo de corrente de saÃda de aproximadamente 68%, sendo essa topologia a que apresenta melhor desempenho, entre os filtros testados, estando apta a substituir o capacitor eletrolÃtico de saÃda.
This work presents a study and development of a switched capacitor-based converter to drive high power light emitting diodes (LEDs) fed from the main grid. Unlike to conventional constant current dc drivers, the current through LEDs is provided by a switched capacitor. The proposed converter approach differs from the traditional switched-capacitor-based one, because it uses an inductance to avoid the forced charging and discharging operation, reducing current spikes and EMI in the circuit. The proposed converter provides inherent power factor correction and it can provide isolation by capacitors. It is also proposed the use of two tuned LC filter topologies (parallel LC filter and series LC filter) to reduce the output current ripple, avoiding the use of large electrolytic capacitors. A theoretical analysis of the proposed converter is performed via quantitative and qualitative analysis, which determines the voltage and current efforts in main components and also losses in the converter. A 51 W, 220 V RMS laboratory prototype is designed and tested experimentally. Simulation and experimental results are presented and discussed demonstrating the technical feasibility of the proposed converter. At rated load, the converter features an efficiency of 75.3% and an input power factor of 0.996, while respecting emission limits of harmonics determined by IEC 61000-3-2. For the application of the parallel LC filter, connected in series with LED array, it is obtained output current ripple of approximately 68%. This topology presented better performance, between tested topologies, being able to replace the output electrolytic capacitor.
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Wang, Tian Xiang. "Study of the integration method on the control of wind power system." Thesis, University of Macau, 2009. http://umaclib3.umac.mo/record=b2144085.
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Adamson, Jesse Timothy. "Pulse Density Modulated Soft Switching Cycloconverter." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/315.
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Single stage cycloconverters generally incorporate hard switching at turn on and soft switching at turn off. This hard switching at turn on combined with the slow switching speeds of thyristors (the switch of choice for standard cycloconverters) limits their use to lower frequency applications.
This thesis explores the analysis and design of a pulse density modulated (PDM), soft switching cycloconverter. Unlike standard cycloconverters, the controller in this converter does not adjust thyristor firing angles. It lets only complete half cycles of the input waveform through to the output. This allows and requires a much greater frequency step down from the input to the output. The advantages, shortcomings and tradeoffs of this topology are explored as this converter is designed, built and tested.
The resulting cycloconverter has many deficiencies, but proves the concept of the PDM soft switching technique. Cases for further improvement and study are outlined. In the end, this converter shows much promise for applications requiring a high step down in frequency, as well as where the lower electromagnetic interference (EMI) of soft switching may be beneficial.
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Nathan, Kumaran Saenthan. "A novel DC-DC converter for photovoltaic applications." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288881.
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Growing concerns about climate change have led to the world experiencing an unprecedented push towards renewable energy. Economic drivers and government policies mean that small, distributed forms of generation, like solar photovoltaics, will play a large role in our transition to a clean energy future. In this thesis, a novel DC-DC converter known as the Coupled Inductors Combined Cuk-SEPIC' (CI-CCS) converter is explored, which is particularly attractive for these photovoltaic applications. A topological modification is investigated which provides several benefits, including increased power density, efficiency, and operational advantages for solar energy conversion. The converter, which is based on the combination of the Cuk and SEPIC converters, provides a bipolar output (i.e. both positive and negative voltages). This converter also offers both step-up and step-down capabilities with a continuous input current, and uses only a single, ground-referenced switching device. A significant enhancement to this converter is proposed: magnetic coupling of the converter's three inductors. This can substantially reduce the CI-CCS converter's input current ripple - an important benefit for maximum power point tracking (MPPT) in photovoltaic applications. The effect of this coupling is examined theoretically, and optimisations are performed - both analytically and in simulations - to inform the design of a 4 kW prototype CI-CCS converter, switched at a high frequency (100 kHz) with a silicon carbide (SiC) MOSFET. Simulation and experimental results are then presented to demonstrate the CI-CCS converter's operation and highlight the benefits of coupling its inductors. An efficiency analysis is also undertaken and its sources of losses are quantified. The converter is subsequently integrated into a domestic photovoltaic system to provide a practical demonstration of its suitability for such applications. MPPT is integrated into the CI-CCS DC-DC converter, and a combined half bridge/T-type converter is developed and paired with the CI-CCS converter to form an entirely transformerless single-phase solar energy conversion system. The combination of the CI-CCS converter's bipolar DC output with the combined half bridge/T-type converter's bipolar DC input allows grounding at both the photovoltaic panels and the AC grid's neutral point. This eliminates high frequency common mode voltages from the PV array, which in turn prevents leakage currents. The entire system can be operated in grid-connected mode - where the objective is to maximise power extracted from the photovoltaic system, and is demonstrated in stand-alone mode - where the objective is to match solar generation with the load's power demands.
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Rizet, Corentin. "Amélioration du rendement des alimentations sans interruption." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00651973.
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Les Alimentations Sans Interruption sont utilisées pour assurer la qualité et la continuité de l'énergie fournie aux charges sensibles. Basées sur deux conversions d'énergie électrique, ces alimentations supportent en permanence la puissance de la charge, rendant crucial leur rendement. Cette thèse a exploré différentes voies d'amélioration du rendement du commutateur assurant la conversion : le choix des composants semi-conducteurs, celui de la structure de conversion et du mode de fonctionnement. Le filtrage a été pris en compte sans faire l'objet d'investigations poussées. La méthode d'estimation du rendement, exploitant des données des constructeurs, a permis de quantifier l'impact et les limites de chaque voie explorée. Plusieurs structures de conversion multi-niveaux en commutation douce ont été développées, utilisant un pôle résonant. Enfin, plusieurs expérimentations ont validé les modèles utilisés, le concept du pôle résonant et la réalisation d'un prototype fonctionnel de 125 kVA.
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Gonzalez, Ander. "Integration of photovoltaic sources and battery based storage systems – A DC analysis and distributed maximum power point tracking solution." Doctoral thesis, Universite Libre de Bruxelles, 2019. https://dipot.ulb.ac.be/dspace/bitstream/2013/282059/4/TOC_vf.pdf.
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In this thesis the integration of photovolatic (PV) generation and energy storage into the electrical grid is discussed. Although the studied system is for grid tied applications, here the integration of the PV generation and the energy storage system (ESS) on the DC-side of the system is addressed. The work contained in this thesis focuses on the integration of the DC-working parts before interfacing them with the grid through the use of an inverter and seeks an increasing in the energy that the system can deliver.First, a study of classical systems that present well-differentiated parts is presented: PV generation, a lithium-ion battery based ESS, the utility grid and a residential electricity consumer. PV installations of 3 and 10kWp are considered together with storage capacities ranging from 1 to 9kWh. This yields interesting insights on how the system works based on the timing of the generation and consumption of energy. The results are used to highlight the weaknesses of the selected converter arrangement for the interfacing of the PV source and the ESS. Results show that the system is rather stiff and lacks from conversion efficiency when it needs to work in a wide range of powers, mainly due to low consumer power demand during battery discharge. In this first part of the thesis, three solutions to workaround the efficiency problem are proposed: reducing the difference between the ESS and the DC-bus voltages, using isolated converters to interface the ESS, or adopting a new arrangement of the parts of the system. One of the first two proposed solutions should be adopted if the same system topology is to be kept. These two solutions address the efficiency problem when the ESS is involved in the energy conversion. The third solution is proposed as alternative to the classical systems that use a DC-bus to exchange power with the different parts of the system. The new proposed arrangement features a distributed maximum power point (DMPPT) type system that includes storage at module level. DMPPT systems are able to track the maximum power point (MPPT) of each panel separately by connecting a small power electronic converter (PEC) to each PV panel. They are specially useful when the PV installation receives uneven irradiance, i.e. shadows are present in some of the panels, increasing the annual yield of PV energy from 7 to 30% as reported in the literature. Unfortunately, this kind of systems cannot always handle high irradiance mismatches, and fail to track the maximum power point (MPP) throughout the whole installation in some cases. Including batteries at module level instead of connecting them to the DC-bus, allows for increasing the MPPT range of the system, virtually to any severity of irradiance mismatch (depending on the state of charge (SoC) of the battery pack), as well as adding storage capability to the system. The novel proposed system is able to workaround the problems of using non-isolated converters, achieving PV energy conversion efficiencies from 86% (for at least 10% of the peak power) to 90% and storage charge/discharge efficiencies ranging from 86% to 95%. Besides, it brings the opportunity to exploit the synergies of having storage at module level in systems that combine renewable energies and storage. Moreover, DMPPT systems achieve superior PV generation under partially shaded conditions when compared to classical PV arrays increasing the PV generation when compared to classical or centralized PV installations up to 45% in power as reported in the literature.In the second part of the thesis, the proposed novel DMPPT topology is presented. The whole system is fully designed from scratch, including PECs, sizing of the different parts of the modules, embedded control loops of the modules and supervisory control of the whole system. Finally, the results obtained from running the proposed system are shown and discussed, and suggestions given on how to operate and protect the system. Experimental results are obtained using a 1.5kWp PV power and 1.5kWh capacity test bench built for that purpose.The proposed system is able to generate PV energy, store the energy coming from PV generation and inject the generated and stored energy into the grid. The proposed system extends the MPPT capability of storage-less series-connected DMPPT systems. This is achieved by using the batteries not only to store energy when required, but also to compensate the power mismatch across DMPPT modules of the same string when the output voltage of the modules becomes a limit. It also presents a modular and upgradable approach to PV systems including storage. This modularity also brings fault tolerance, and an ability to continue working after failure of one or more of the DMPPT modules by partially or completely isolating the faulty module (depending on the nature of the fault). Moreover, the addition of the DC-DC converters allows for the use of different PV panels in the system, i.e. from different manufacturers or technologies.In conclusion, the presented system is very flexible, can be designed for a wide range of power levels and energy storage sizes, and presents improved reliability when compared to other series-connected DMPPT systems.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Venturini, William Alegranci. "Fonte ininterrupta de energia trifásica de alto desempenho sem transformador com dupla funcionalidade do estágio de entrada e sistema de controle digital." Universidade Federal de Santa Maria, 2016. http://repositorio.ufsm.br/handle/1/8594.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThis master s thesis proposes a three-phase transformerless double-conversion UPS with digital control system and reduced overall cost. The topology is composed of an input stage, a battery bank, an inverter, an auxiliary circuit and transfer switches. The input stage assumes the three-phase rectifier function with LCL filter in normal operation mode and is responsible for discharge the battery bank in backup mode. This configuration reduces the system cost since an available circuit is used to discharge the battery bank. In conventional double-conversion UPS topologies the input stage remains inactive during the backup mode and an additional circuit is employed for this purpose. The auxiliary circuit is formed by an inductor and a switching leg and is used as a battery charger during normal operation mode and is additionally used to balance the bus capacitors voltages in backup mode. In this configuration, the auxiliary circuit can be designed for only a fraction of the UPS rated power, also providing lower total system cost. Transfer switches change the configuration of the input stage and the auxiliary circuit according to the UPS operating mode. The detailed operation of the topology, modelling, digital control structure, and the results obtained by simulation are showed. Finally a 20 kVA prototype is implemented and experimental results are acquired for the validation of the employed design methodology as well as the proposed circuit functionality.
Esta dissertação de mestrado propõem uma topologia de fonte ininterrupta de energia (UPS - Uninterruptible Power Supplies) trifásica de dupla conversão sem transformador com custo reduzido e sistema de controle digital. A UPS proposta é composta por um estágio de entrada, um banco de baterias, um inversor, um circuito auxiliar e chaves de transferência. O estágio de entrada assume a função de retificador trifásico com filtro LCL em modo normal de operação da UPS e é responsável pela descarga do banco de baterias em modo bateria de operação. Esta configuração reduz o custo do sistema, pois permite que seja aproveitado um circuito disponível e dimensionado para a potência nominal da UPS para a descarga do banco de baterias. Em topologias convencionais de UPSs de dupla conversão o estágio de entrada permanece ocioso durante este modo de operação e um circuito adicional é empregado para este fim. O circuito auxiliar é formado por um indutor e um braço de interruptores e é utilizado como carregador de baterias em modo normal de operação e adicionalmente é utilizado para realizar o equilíbrio das tensões dos capacitores de barramento em modo bateria. Com esta configuração, o circuito auxiliar pode ser dimensionado para apenas uma fração da potência nominal da UPS, propiciando também a redução do custo total do sistema. As chaves de transferência alteram as configurações do estágio de entrada e do circuito auxiliar de acordo com o modo de operação da UPS. É apresentada a operação detalhada da topologia, a modelagem, a estrutura de controle digital utilizada e os resultados obtidos via simulação. Por fim, um protótipo de 20 kVA é implementado e resultados experimentais são adquiridos para a validação da metodologia de projeto empregada bem como da funcionalidade do circuito proposto.
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Guida, Vittorio. "Conception et réalisation d'un convertisseur DC/DC à haut rapport de conversion pour électrolyseurs." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0134.
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Ces dernières années, l’utilisation des électrolyseurs pour produire proprement et efficacement de l’hydrogène à partir de sources d’énergie renouvelables (éolien, solaire) a profité d’un intérêt croissant de la part des chercheurs et également des industriels. De même que les piles à combustible, les électrolyseurs ont besoin de convertisseurs DC/DC. Généralement, les électrolyseurs exigent une faible tension continue afin de produire de l’hydrogène à partir d’eau dé-ionisée, pure ou distillée. Pour cette raison, les convertisseurs DC/DC buck sont généralement utilisés. Pour des applications électrolyseur, les convertisseurs DC/DC doivent répondre à de nombreuses problématiques en termes d’efficacité énergétique, de compacité et de réduction de l’ondulation de courant de sortie. Les ondulations de courant générées par les convertisseurs DC/DC peuvent conduire à des dégradations à long terme sur les électrolyseurs et par conséquent réduire leurs durées de vie. En outre, la disponibilité et la fiabilité des convertisseurs DC/DC restent une préoccupation majeure afin que les systèmes multi-sources puissent garantir un haut niveau d’autonomie. Dans les systèmes multi-sources, le bus DC de gestion des flux d’énergie est généralement une haute tension de quelques centaines de volt. Etant donné que l’électrolyseur doit être alimenté en tension très faible, le convertisseur DC/DC d’interface doit présenter un haut rapport de conversionIn recent years, the use of electrolyzer to produce cleanly and efficiently hydrogen from renewable energy sources (e.g. wind, solar) has gained growing interest from researchers and industrial. Similarly to fuel cells, electrolyzers require power conditioning systems, such as DC/DC converters. Generally, electrolyzers need a very low DC voltage to generate hydrogen from de-ionized, pure or distilled water. For this reason, DC/DC buck converters are generally used. For electrolyzer applications, DC/DC converters must meet several challenging issues in terms of energy efficiency and output current ripple reduction. Generated high-frequency current ripples from DC/DC converter may lead to long-term degradation on electrolyzers. As a result, high-frequency current ripples can shorten the electrolyzer life span. Furthermore, the availability and reliability of DC/DC converters remain a major concern so that stand-alone power supply can guarantee a high-level of autonomy in case of electrical failures. Within the wind-H2 stand-alone power supply, DC bus is generally a high-voltage of a few hundreds of volt. Given that the electrolyzer must be supplied at a very low DC voltage, interface DC/DC converter has to present a high-conversion ratio
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Lopez, Santos Oswaldo. "Contribution to the DC-AC conversion in photovoltaic systems : Module oriented converters." Thesis, Toulouse, INSA, 2015. http://www.theses.fr/2015ISAT0001/document.
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Ces dernières années, un intérêt croissant pour les systèmes électroniques de puissance a été motivé par l'émergence de sources d'énergie distribuées et renouvelables raccordées aux réseaux électriques. Dans ce contexte, la nécessité de topologies de faibles puissances alimentées par quelques modules photovoltaïques, en évitant l'utilisation de transformateurs, a ouvert l'étude de convertisseurs spéciaux et l’étude des stratégies de commande associées afin d’assurer la stabilité, la fiabilité et un rendement élevé du dispositif. Une possible solution est d’utiliser un dispositif générique connu dans la littérature scientifique et commerciale comme « micro-onduleur » ou «convertisseur intégré au module » qui avec le module photovoltaïque définit un produit « plug and play » appelé "module AC".Ce travail est consacré à l'étude d'un micro-onduleur monophasé avec deux étapes sans transformateur raccordée au réseau. La topologie proposée est composé d’un convertisseur DC-DC non isolé élévateur avec un gain quadratique et un onduleur réducteur lié au réseau connectés en cascade. Le convertisseur DC-DC extrait en permanence la puissance maximale du module photovoltaïque malgré les changements dans les conditions environnementales. L'étape DC-AC injecte la puissance extraite par l'étape DC-DC dans le réseau et assure un niveau élevé de qualité de l’énergie. Les efforts de recherche de ce travail sont concentrés sur la mise au point de commandes utilisant comment base, la théorie de contrôle par mode de glissement, qui conduit à une mise en œuvre simple avec une description théorique complète validée á partir de simulations et expérimentations.Après avoir décrit l'état de l’art dans le premier chapitre, le manuscrit est divisé en quatre chapitres, qui sont dédiés respectivement à l’algorithme de recherche du point de puissance maximale (MPPT), á l’étape de conversion DC-DC, á l'étape de conversion DC-AC et finalement au micro-onduleur complet. Un nouvel algorithme de recherche extrémal du point de puissance maximale est développé (SM-ESC). Pour la étape DC-DC, le convertisseur élévateur quadratique avec seulement un interrupteur contrôlé est étudié utilisant le concept de résistance sans perte par mode de glissement (de l’acronyme anglais : Sliding-Mode Loss-Free-Resistor – SM-LFR) afin d’obtenir un gain de tension élevé avec un fonctionnement sûr et compatible avec l’algorithme MPPT. Pour la étape DC-AC, le convertisseur de pont complet est contrôlé comme un onduleur de source de puissance (de l’acronyme anglais : Power Source Inverter - PSI) en utilisant une commande par mode de glissement qui poursuit une référence sinusoïdale de courant de sortie. Cette commande est complétée par une boucle de régulation de la tension du bus DC qui assure une haute qualité d’énergie injectée dans le réseau. Enfin, les trois étapes constitutives sont fusionnées pour obtenir un micro-onduleur complètement contrôlé par la technique de mode de glissement, ce qui constitue le principal résultat et contribution de cette thèseThese last years, a growing interest in power electronic systems has been motivated by the emergence of distributed renewable energy resources and their interconnection with the grid. In this context, the need of low power topologies fed by a few photovoltaic modules avoiding the use of transformers opens the study of special converters and the associated control strategies ensuring stability, reliability and high efficiency. A resulted generic device known in the commercial and scientific literature as “microinverter” or “module integrated converter” performs a plug and play product together with the PV module called an “AC module”.This work is devoted to the study of a transformer-less single-phase double-stage grid-connected microinverter. The proposed topology has a non-isolated high-gain boost type DC-DC converter and a non-isolated buck type DC-AC converter connected in cascade through a DC bus. The DC-DC converter permanently extracts the maximum power of the PV module ensuring at the same time a good performance coping with power changes introduced by the change in the environmental conditions. The DC-AC stage injects the power extracted by the DC-DC stage into the grid ensuring a high level of power quality. The research efforts focus on the involved control functions based on the sliding mode control theory, which leads to a simple implementation with a comprehensive theoretical description validated through simulation and experimental results.After giving the state-of-the-art in the first chapter, the manuscript is divided into four chapters, which are dedicated to the Maximum Power Point Tracking (MPPT), the DC-DC stage and its control, the DC-AC stage and its control and the complete microinverter. A new Extremum Seeking Control (ESC) MPPT algorithm is proposed. The single-switch quadratic boost converter is studied operating as a Loss-Free-Resistor (LFR) obtaining a high DC output voltage level with a safe operation. The full-bridge converter is controlled as a Power Source Inverter (PSI) using a simple sliding-mode based tracking law, regulating the voltage of the DC bus and then ensuring a high power quality level in the grid connection. Finally, the three building blocks are merged to obtain a sliding mode controlled microinverter constituting the main result and contribution of the work
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Arroyo, Emmanuelle. "Récupération d'énergie à partir des vibrations ambiantes : dispositif électromagnétique et circuit électronique d'extraction synchrone." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00768218.
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La récupération d'énergie vise à réaliser des dispositifs électromécaniques de taille centimétrique permettant d'alimenter des systèmes électroniques en puisant de manière opportuniste l'énergie du milieu environnant. Parmi les différentes sources disponibles (solaire,thermique etc.) les vibrations ambiantes sont susceptibles de fournir assez de puissance pour alimenter des microsystèmes autonomes tels que des noeuds de réseaux de capteurs communicants. L'enjeu consiste à concevoir des microgénérateurs effectuant la conversion de cette énergie mécanique ambiante en énergie électrique exploitable de manière optimale.Ces travaux de thèse proposent dans un premier temps un critère d'étude et de comparaison des performances des générateurs de types piézoélectriques ou électromagnétiques, à partir d'un modèle normalisé unifié. Dans un second temps, un circuit non linéaire d'extraction de l'énergie est étudié pour les générateurs électromagnétiques, et ses performances sont discutées en comparaison avec un circuit classique d'extraction de l'énergie. A partir de ces résultats, une nouvelle structure de générateur électromagnétique est conçue, optimisée puis validée expérimentalement.
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Villalva, Marcelo Gradella 1978. "Conversor eletrônico de potência trifásico para sistema fotovoltaico conectado à rede elétrica." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260742.
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Orientador: Ernesto Ruppert FilhoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-17T05:47:06Z (GMT). No. of bitstreams: 1 Villalva_MarceloGradella_D.pdf: 10773240 bytes, checksum: aeccba84d675a257bed00100b3d011cb (MD5) Previous issue date: 2010
Resumo: Este trabalho é uma contribuição ao estudo de conversores eletrônicos para sistemas fotovoltaicos de geração distribuída de energia elétrica. O objetivo principal é apresentar o desenvolvimento e os resultados de um conversor eletrônico trifásico para a conexão de um conjunto de painéis solares fotovoltaicos à rede elétrica de baixa tensão. São apresentados resultados experimentais e estudos teóricos sobre a modelagem e a simulação de dispositivos fotovoltaicos, a regulação da tensão fotovoltaica, o rastreamento da máxima potência e a modelagem e o controle de um conversor eletrônico de dois estágios
Abstract: This work is a contribution to the study of power converters for photovoltaic distributed generation systems. The main objective is to present the development and results of a threephase power converter for a grid-connected photovoltaic plant. The work presents experimental results and theoretical studies on the modeling and simulation of photovoltaic devices, regulation of the photovoltaic voltage, maximum power point tracking, and the modeling and control of a two-stage grid-connected power converter
Doutorado
Energia Eletrica
Doutor em Engenharia Elétrica
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Fu, Hailing. "Rotational energy harvesting for low power electronics." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/59031.
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Energy harvesting is one of the key technologies for the realization of autonomous sensing. The aim of this thesis is to develop low-frequency broadband rotational energy harvesting solutions for self-powered sensing. As an example of rotational energy harvesting, an airflow energy harvester using a miniaturized turbine and piezoelectric transduction was first introduced. Rotation was converted from airflow by the turbine, and a piezoelectric beam was actuated by the turbine rotor using magnetic plucking. Issues, including high cut-in speed and low output power at high rotational frequencies, were discovered. In order to decrease the cut-in speed, a self-regulating mechanism was proposed and integrated. The magnetic plucking strength can be passively adjusted according to the rotational speed. This self-regulating harvester exhibited a lower cut-in speed. In order to understand the limited performance at high rotational frequencies and to optimize the design, a theoretical model was built. Different arrangements were investigated, showing that this harvester is ideal to operate at low excitation frequency far below the piezoelectric beam's resonant frequency. Bistable behaviour was also employed and studied to enhance the energy harvesting capability over a wide bandwidth at low frequency. Then, a complete self-powered condition monitoring system, including a bistable frequency up-converting harvester, a power management circuit and a wireless sensor node, was studied and developed to implement the concept of self-powered sensing. Finally, a fundamental study was conducted for three types of rotational energy harvesters, including electromagnetic, piezoelectric resonant, and piezoelectric non-resonant harvesters. Scaling laws for each type were established to study harvesters' performance for different operating frequencies and device dimensions. This study provides a guideline for selection and design of rotational energy harvesters with specific requirements of device dimension and operating frequency.
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Das, Debosmita. "Advanced power electronics for hybrid energy systems." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1412940298.
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Howard, John N. "Thermophotovoltaic energy conversion in submarine nuclear power plants." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5684.
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Approved for public release; distribution is unlimited.v ABSTRACT Thermophotovoltaic (TPV) cells allow for the direct conversion of infrared (IR) radiation to electricity, similar to when traditional solar cells are exposed to visible light. The objective of this thesis is the development of a computer model of a multijunction TPV cell designed to absorb IR radiation from the primary fluid system of a naval nuclear reactor. This model is then used to determine the feasibility of using this TPV system as a supplemental source of electrical power on a next-generation nuclear submarine. The results of this simulation indicate that the design concept presented in this thesis is a viable option and warrants further consideration and research.
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Rizea, Steven Emanoel. "Optimization of Ocean Thermal Energy Conversion Power Plants." Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5462.
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A proprietary Ocean Thermal Energy Conversion (OTEC) modeling tool, the Makai OTEC Thermodynamic and Economic Model (MOTEM), is leveraged to evaluate the accuracy of finite-time thermodynamic OTEC optimization methods. MOTEM is a full OTEC system simulator capable of evaluating the effects of variation in heat exchanger operating temperatures and seawater flow rates. The evaluation is based on a comparison of the net power output of an OTEC plant with a fixed configuration. Select optimization methods from the literature are shown to produce between 93% and 99% of the maximum possible amount of power, depending on the selection of heat exchanger performance curves. OTEC optimization is found to be dependent on the performance characteristics of the evaporator and condenser used in the plant. Optimization algorithms in the literature do not take heat exchanger performance variation into account, which causes a discrepancy between their predictions and those calculated with MOTEM. A new characteristic metric of OTEC optimization, the ratio of evaporator and condenser overall heat transfer coefficients, is found. The heat transfer ratio is constant for all plant configurations in which the seawater flow rate is optimized for any particular evaporator and condenser operating temperatures. The existence of this ratio implies that a solution for the ideal heat exchanger operating temperatures could be computed based on the ratio of heat exchanger performance curves, and additional research is recommended.ID: 031001365; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: Marcel Ilie.; Title from PDF title page (viewed May 8, 2013).; Thesis (M.S.M.E.)--University of Central Florida, 2012.; Includes bibliographical references (p. 77-78).
M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Mechanical Systems
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McPeake, F. A. "Wave energy conversion using small scale floating devices." Thesis, Queen's University Belfast, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374227.
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Ahmed, Shehab. "Compact harsh environment energy conversion systems." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1289.
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Zhang, Yongzheng. "Doubly-fed induction machine for variable speed energy conversion applications." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114286.
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After decades of development, the wind energy industry is now supplying 10 to 20% of power in electric utilities. At present Doubly-Fed Induction Generators (DFIG) are one of the most widely used generators in wind farms. The research of this thesis advances the methods of controlling DFIGs by presenting: (i)a non-mechanical (sensorless) method of determining accurate rotor speed and rotor position which are essential in implementing decoupled P-Q control; (ii)a method of autonomous frequency control whereby an islanded wind farm does not have to shut down but continues to operate as standby ready to assist the utility grid in fast restoration; (iii) a method of mitigating the problem of power imbalance at the initial period of islanding by using pitch control to spill excess wind power.The thesis also examines what economical adaptation is required to make the Doubly-Fed Induction Generator, which has the advanced controllers designed for wind power application, marketable as Doubly-Fed Induction Motor. Research is based on theoretical analysis, validated by digital simulation. A prototype DFIG 5hp experimental platform, which has been built and tested, provides experimental verification to claims.Après des décennies de développement, l'industrie de l'énergie éolienne fournit maintenant de 10% à 20% de la puissance produite dans les réseaux électriques. Présentement, les alternateurs asynchrones à double alimentation (DFIG) sont parmi les alternateurs les plus utilisés dans les parcs éoliens. La recherche de cette thèse avance les méthodes de contrôle des DFIGs par la présentation : (i)d'une méthode non-mécanique (sans capteur de mesure) afin de déterminer précisément la vitesse et la position du rotor, qui sont essentielles dans l'implémentation de contrôle découplée P-Q; (ii)d'une méthode de contrôle autonome de la fréquence par quoi un parc éolien îloté n'a pas à interrompre sa production mais il peut continuer à fonctionner en attente pour aider le réseau électrique à une restauration rapide. (iii) D'une méthode pour limiter le problème de déséquilibre de puissance au début de l'îlotage en utilisant l'angle d'attaque de l'éolienne pour évacuer l'excédent de la puissance éolienne.Cette thèse examine aussi l'adaptation économique requise pour rendre l'alternateur asynchrone à double alimentation, qui contient les contrôleurs conçus pour l'application éolienne, commercialisable comme moteur asynchrone à double alimentation. La recherche est basée sur l'analyse théorique, validée par simulation digitale. Une plateforme prototype d'un DFIG de 5hp, qui a été construite et testée, fournit la vérification expérimentale des résultats de la recherche.
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Thorburn, Karin. "Electric Energy Conversion Systems : Wave Energy and Hydropower." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7081.
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Trilla, Romero Lluís. "Power converter optimal control for wind energy conversion systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/134602.
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L'energia eòlica ha incrementat la seva presència a molts països i s'espera que tingui encara un pes més gran en la generació elèctrica amb la implantació de la tecnologia eòlica marina. En aquest context el desenvolupament de models dels Sistemes de Generació per Turbina de Vent (SGTV) precisos és important pels operadors de xarxa per tal d'avaluar-ne el comportament. Els codis de xarxa ofereixen un seguit de normes per validar models amb dades obtingudes de proves de camp. A la primera part d'aquesta tesi un model de SGTV amb màquina d'inducció doblement alimentada (DFIG) és validat d'acord amb les normatives espanyola i alemanya. Avui dia molts parc eòlics utilitzen DFIG i, en conseqüència, les dades de camp disponibles son per aquesta tecnologia. Per a la indústria eòlica marina un avanç prometedor son els SGTV amb generadors síncrons d'imants permanents (PMSG). Per aquesta raó la segona part d'aquesta tesi es centra en SGTV basats en PMSG amb convertidor back-to-back de plena potència. Aquest convertidor es pot dividir en dues parts: el costat de xarxa (GSC) que interactua amb la xarxa elèctrica i el costat de màquina (MSC) que controla el generador.
En general, el sistema de control del convertidor recau en els tradicionals controladors PI i, en ocasions, incorpora desacoblaments per reduir les influencies creuades entre les variables. Aquest controlador pot ser sintonitzat i implementat fàcilment donat que la seva estructura és simple, però, no presenta una resposta ideal donat que no aprofita tots els graus de llibertat disponibles en el sistema. És important desenvolupar controladors fiables que puguin oferir una resposta previsible del sistema i proveir robustesa i estabilitat. En especial per zones on la presència eòlica és gran i per parcs eòlics connectats a xarxes dèbils.
En aquest treball es proposa un sistema de control pel convertidor basat en teoria de control H-infinit i en controladors Lineals amb Paràmetres Variants (LPV). La teoria de control òptim proveeix un marc de treball on més opcions es poden tenir en consideració a l'hora de dissenyar el controlador. En concret la teoria de control H-inifinit permet crear controladors multivariables per tal d'obtenir una òptima resposta del sistema, proveir certa robustesa i assegurar l'estabilitat. Amb aquesta tècnica durant la síntesi del controlador el pitjor cas de senyals de pertorbació és contemplat, d'aquesta manera el controlador resultant robustifica l'operació del sistema. Es proposa aquest control per al GSC posant especial èmfasi en obtenir un control de baixa complexitat que mantingui els beneficis d'aplicar la teoria de control òptim i faciliti la seva implementació en computadors industrials. Pel MSC es proposa una estratègia diferent basada en control LPV donat que el punt d'operació del generador canvia constantment. El sistema de control basat en LPV és capaç d'adaptar-se dinàmicament al punt d'operació del sistema, així s'obté en tot moment la resposta definida durant el procés de disseny. Amb aquesta tècnica l'estabilitat del sistema sobre tot el rang d'operació queda garantida i, a més, s'obté una resposta predictible i uniforme. El controlador està dissenyat per tenir una estructura simple, com a resultat s'obté un control que no és computacionalment exigent i es proveeix una solució que pot ser utilitzada amb equips industrials.
S'utilitza una bancada de proves que inclou el PMSG i el convertidor back-to-back per tal d'avaluar experimentalment l'estratègia de control dissenyada al llarg d'aquest treball. L'enfoc orientat a la implementació dels controls proposats facilita el seu ús amb el processador de senyals digitals inclòs a la placa de control de la bancada. Els experiments realitzats verifiquen en un ambient realista els beneficis teòrics i els resultats de simulació obtinguts prèviament. Aquestes proves han ajudat a valorar el funcionament dels controls en un sistema discret i la seva tolerància al soroll de senyals i mesuresWind energy has increased its presence in many countries and it is expected to have even a higher weight in the electrical generation share with the implantation of offshore wind farms. Consequently, the wind energy industry has to take greater responsibility towards the integration and stability of the power grid. In this sense, there are proposed in the present work control systems that aim to improve the response and robustness of the wind energy conversion systems without increasing their complexity in order to facilitate their applicability. In the grid-side converter it is proposed to implement an optimal controller with its design based on H-infinity control theory in order to ensure the stability, obtain an optimal response of the system and also provide robustness. In the machine-side converter the use of a Linear Parameter-Varying controller is selected, this choice provides a controller that dynamically adapts itself to the operating point of the system, in this way the response obtained is always the desired one, the one defined during the design process. Preliminary analysis of the controllers are performed using models validated with field test data obtained from operational wind turbines, the validation process followed the set of rules included in the official regulations of the electric sector or grid codes. In the last stage an experimental test bench has been developed in order to test and evaluate the proposed controllers and verify its correct performance.
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Gong, Qian. "Integrated power conversion circuit for radio frequency energy harvesting." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609873.
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Presby, Andrew L. "Thermophotovoltaic energy conversion in space nuclear reactor power systems." Thesis, Monterey, Calif. : Naval Postgraduate School, 2004. http://edocs.nps.edu/npspubs/scholarly/theses/2004/Dec/04Dec%5FPresby.pdf.
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Thesis (Astronautical Engineer and M. S. in Astronautical Engineering)--Naval Postgraduate School, December 2004.Thesis Advisor(s): Gopinath, Ashok ; Michael, Sherif. "December 2004." Description based on title screen as viewed on March 13, 2009. Includes bibliographical references (p. 123-127). Also available in print.
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Kamanzi, Janvier. "Thermal electric solar power conversion panel development." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2527.
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Thesis (DTech (Engineering))--Cape Peninsula University of Technology, 2017.The world has been experiencing energy-related problems following pressuring energy demands which go along with the global economy growth. These problems can be phrased in three paradoxical statements: Firstly, in spite of a massive and costless solar energy, global unprecedented energy crisis has prevailed, resulting in skyrocketing costs. Secondly, though the sun releases a clean energy, yet conventional plants are mainly being run on unclean energy sources despite their part in the climate changes and global warming. Thirdly, while a negligible percentage of the solar energy is used for power generation purposes, it is not optimally exploited since more than its half is wasted in the form of heat which contributes to lowering efficiency of solar cells and causes their premature degradation and anticipated ageing. The research is geared at addressing the issue related to unsatisfactory efficiencies and anticipated ageing of solar modules. The methodology adopted to achieve the research aim consisted of a literature survey which in turn inspired the devising of a high-efficiency novel thermal electric solar power panel. Through an in-depth overview, the literature survey outlined the rationale of the research interest, factors affecting the performance of PVs as well as existing strategies towards addressing spotted shortcomings. While photovoltaic (PV) panels could be identified as the most reliable platform for sunlight-to-electricity conversion, they exhibit a shortcoming in terms of following the sun so as to maximize exposure to sunlight which negatively affects PVs’ efficiencies in one hand. On the other hand, the inability of solar cells to reflect the unusable heat energy present in the sunlight poses as a lifespan threat. Strategies and techniques in place to track the sun and keep PVs in nominal operational temperatures were therefore reviewed.
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Boström, Cecilia. "Electrical Systems for Wave Energy Conversion." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-140116.
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Wave energy is a renewable energy source with a large potential to contribute to the world's electricity production. There exist several technologies on how to convert the energy in the ocean waves into electric energy. The wave energy converter (WEC) presented in this thesis is based on a linear synchronous generator. The generator is placed on the seabed and driven by a point absorbing buoy on the ocean surface. Instead of having one large unit, several smaller units are interconnected to increase the total installed power. To convert and interconnect the power from the generators, marine substations are used. The marine substations are placed on the seabed and convert the fluctuating AC from the generators into an AC suitable for grid connection. The work presented in the thesis focuses on the first steps in the electric energy conversion, converting the voltage out from the generators into DC, which have an impact on the WEC's ability to absorb and produce power. The purpose has been to investigate how the generator will operate when it is subjected to different load cases and to obtain guidelines on how future systems could be improved. Offshore experiments and simulations have been done on full scale generators connected to four different loads, i.e. one linear resistive load and three different non-linear loads representing different cases for grid connected WECs. The results show that the power can be controlled and optimized by choosing a suitable system for the WEC. It is not obvious which kind of system is the most preferable, since there are many different parameters that have an impact on the system performance, such as the size of the buoy, how the generator is designed, the number of WECs, the highest allowed complexity of the system, costs and so on. Therefore, the design of the electrical system should preferably be carried out in parallel with the design of the WEC in order to achieve an efficient system.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 727
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Michaelides, Alexandros M. "The design of switched reluctance motors for efficient energy conversion." Thesis, University of Warwick, 1994. http://wrap.warwick.ac.uk/36213/.
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A new switched reluctance motor configuration is proposed, in which the windings are arranged to encourage short magnetic flux paths within the motor. Short flux path motor configurations have been modelled extensively using electromagnetic finite element analysis. It is demonstrated that short flux paths significantly reduce the MMF required to establish the B-field pattern in a motor; as a result copper losses are reduced. In addition, hysteresis and eddy current losses are decreased as the volume of iron in which iron losses are generated is reduced. Short flux paths are formed when two adjacent phase windings, configured to give neighbouring stator teeth opposite magnetic polarity, are simultaneously excited. In order to accurately model short flux path machines, a thorough electromagnetic analysis of doubly excited systems is adopted. The proposed modelling theory forms the basis for design considerations that can optimise the performance of the 4-phase and 5-phase switched reluctance motors. The electromagnetic theory of doubly excited systems is used in conjunction with a dynamic simulation program, written in Turbo Pascal, to design a 5-phase switched reluctance motor that exploits the advantages of short flux paths. Test results from the constructed prototype confirm that short flux paths significantly improve the efficiency of the switched reluctance motor. The 5-phase prototype achieves higher efficiency than all known prior art switched reluctance motors and industrial induction machines constructed in the same frame size. At the [1300rpm, 20Nrn] operating point the efficiency of the 5-phase drive was measured to be 87%. The corresponding motor efficiency was in excess of 89.5%.
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Kalpaktsoglou, Dimitrios. "Power factor correction for stand-alone wave energy conversion buoys." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519591.
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Ayeleso, Ayokunle Oluwaseun. "An improved plasma energy conversion system for electric power generation." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2694.
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Thesis (PhD (Electrical Engineering))--Cape Peninsula University of Technology, 2018.The generation of electricity through the conventional conversion system such as thermal and hydroelectric plants may no longer be sufficient to meet the increasing demands and usage. One of the major reasons for shortage supply of electric power is due to the lack of fossil fuel and other conventional resources that are currently being used in Africa. In addition, the conversion process of the conventional system often causes pollution which contributes to global warming. Therefore, there is a need for this research to develop novel and alternative methods of generating electric power. Among these methods is the Magnetohydrodynamics (MHD) conversion system, which is a direct energy conversion system. In this system, plasma or ionised gas is directly converted into electric power with generating efficiency of about 62 %. The conversion process of the MHD system is based on the principle of Faraday’s Law of electromagnetism and fluid dynamics. The focus of the present study is to investigate alternative methods through which an MHD power generator can be coupled to the existing thermal plants in South Africa. In doing so, the thermal cycle efficiency of these conventional plants can be improved. Another goal of this study is to investigate the behaviour of an MHD generator prototype under exposure to plasma through simulation and experimentation in a laboratory setting.
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Kravetz, Fábio Inocêncio. "Conversor SEPIC modificado com acoplamento magnético série e célula multiplicadora de tensão." Universidade Tecnológica Federal do Paraná, 2018. http://repositorio.utfpr.edu.br/jspui/handle/1/3201.
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As fontes renováveis de energia, em especial a energia solar fotovoltaica vem ganhando espaço nos últimos anos devido ao avanço da tecnologia, redução dos custos e redução das fontes não-renováveis. Os painéis fotovoltaicos isoladamente ou para pequenas aplicações geram uma baixa tensão de saída e a adequação dos níveis de tensão fornecidos em sua saída aos requeridos pela concessionária de energia elétrica é um desafio. Neste trabalho é apresentada uma nova estrutura modificada da topologia do conversor SEPIC que usa as técnicas de acoplamento magnético série e células multiplicadoras de tensão em conjunto, afim de obter um elevado ganho de tensão, visando a aplicação em fontes renováveis de energia. Optou-se pela solução não isolada, pois esta apresenta diversas vantagens em relação a solução isolada, como: menor peso, volume, custo e maior eficiência energética devido a menores perdas de potência nos indutores acoplados. Também, a utilização da indutância de dispersão, que é um parâmetro intrínseco de um acoplamento magnético, permite a operação com comutação suave ZCS (ZCS, do inglês Zero Current-Switching) no interruptor, aumentando a eficiência da estrutura com a redução das perdas por comutação. No decorrer do trabalho são realizadas as análises das etapas de operação de diversos conversores a partir do conversor SEPIC modificado, evolui-se pela adição de técnicas elevadoras de tensão até a estrutura proposta neste trabalho. Por fim, é realizado o controle em malha fechada utilizando um controlador PID analógico que fornece uma resposta rápida e consequente correção a possíveis mudanças na variável controlada. Os resultados teóricos e experimentais do conversor proposto são descritos neste trabalho para validar as análises desenvolvidas e demonstrar a eficiência da estrutura. O protótipo é desenvolvido para uma aplicação com potência nominal de 200 W, tensão nominal de saída igual a 450 V e uma tensão de entrada variando entre 20 V e 40 V. O rendimento obtido para o conversor proposto operando na frequência de 35 kHz na potência nominal é de 91,28% e eficiência igual a 89,04% para a potência nominal de 200 W na frequência de 90 kHz.The renewable energy resources, in special the photovoltaic energy has been achieve more space in last years due to technology advances, cost reduction and decrease of the non-renewable energy sources. The photovoltaic panels in isolation or to small applications generate a low output voltage and to comply with of voltage levels provided in panel’s output to those required by electric power concessionaire is a challenge. In this work is presented a new structure modified of the SEPIC converter topology who uses the coupling magnetic series and voltage multiplier cell techniques together, in order to obtain a high voltage gain aiming at application in renewable energy resources. It was has been choosen non-isolated solution, because this present several advantages in relation to the isolated solution, such as: lower weight, volume, cost and high energy efficiency due to smaller power losses in the coupled inductors. The use leakage inductance, who is an intrinsic parameter of the a magnetic coupling, allows soft-switching operation ZCS in switch, increasing the structure’s efficiency with reduction of switching losses. During the work are perform the analysis of the operation steps of several converters as of the modified SEPIC converter and evolves by addition high voltage techniques until the structure proposed in this work. Finally, is performed the closed loop control using the analog PID controller who provides a fast response and consequent correction to possible changes in the controlled variable. The theoretical and experimental results of the proposed converter are described in this work to validate the developed analysis and demonstrate the structure’s efficiency. The prototype is developed to a application with nominal power of 200 W, nominal output voltage equal 450 V and an input voltage varying between 20 V and 40 V. The efficiency obtained to proposed converter operating in frequency of the 35 kHz in nominal power is 91,28% and efficiency equal 89,04% to nominal power in frequency of the 90 kHz.
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Tymerski, Richard P. E. "Topology and analysis in power conversion and inversion." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/77852.
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Basic PWM dc-to-dc converter structure is examined wherein a basic substructure of converters, known as a converter cell, is identified. Converter cells can be used in generation and classification of basic PWM dc-to-dc converters. A large number of new converters are generated.
Converter analysis, whereby the nonlinear response of the system to perturbations in the control or the input, is determined by two different methods.
A classical approach to nonlinear systems analysis is first used wherein the system is represented by a Volterra functional series. The alternative approach presented concentrates on deriving circuit models for the PWM switch. The PWM switch represents the static nonlinear substructure of the vast majority of converter cells. Analysis of converters then proceeds in an analogous fashion to ordinary transistor circuit analysis whereby the nonlinear device is replaced by its circuit model.
Topological considerations of single-phase dc-to-ac inverters are discussed. A number of zero-current switching quasi-resonant inverter topologies are derived. Schemes that permit these topologies to handle reactive loads are identified.Ph. D.
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MacRae, Angus Neil. "Economic and cost engineering aspects of wind energy conversion systems." Thesis, Robert Gordon University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258961.
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Vasconcelos, Araújo Samuel [Verfasser]. "On the Perspectives of Wide-Band Gap Power Devices in Electronic-Based Power Conversion for Renewable Systems / Samuel Vasconcelos Araújo." Kassel : Kassel University Press, 2013. http://d-nb.info/1056974702/34.
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Nsumbu, Cassandra Daviane. "Development of a soft-core based power electronic conversion controller." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/2379.
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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2014.The application of digital control techniques has become dominant in power electronics owing to several advantages they present, when compared to analogue solutions. Their development is based on the use of microprocessors and microcontrollers, such as Application Specific Integrated Circuit (ASIC), Digital signal processors (DSP), Field Programmable Gate Arrays (FPGA), or a combination of these devices. This thesis presents an investigation of a soft-core based FPGA control system as a solution for power electronic applications. The aim was the development and implementation of a conversion controller, which purpose is to supply control inputs in the form of digital Pulse Width Modulation (PWM) signals, to a number of power electronic applications, such as single half and full bridge DC-DC converters, three phase and multicell inverters. The PWM control technique is achieved via their power semiconductor switching devices. These PWM control signals are necessary for the high frequency conversion of an analog input voltage (AC, DC or unregulated) to an analog output voltage of another level (AC or DC). This was intended to be achieved by exploiting and combining the advantages that FPGA and embedded processors provide such as high reconfigurability and multipurpose ability. This controller’s digital outputs, namely PWM switching signals, can be directly delivered to an analog signal amplification circuit to create an adequate voltage level before being processed by the converters’ switches.
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Hostettler, Jacob. "Advanced Control of Permanent Magnet Synchronous Generators for Variable Speed Wind Energy Conversion Systems." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1588620.
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Various environmental and economic factors have lead to increased global investment in alternative energy technologies such as solar and wind power. Although methodologies for synchronous generator control are well researched, wind turbines present control systems challenges not presented by traditional generation. The varying nature of wind makes achieving synchronism with the existing electrical power grid a greater challenge. Departing from early use of induction machines, permanent magnet synchronous generators have become the focus of power systems and control systems research into wind energy systems. This is due to their self excited nature, along with their high power density. The problem of grid synchronism is alleviated through the use of high performance power electronic converters. In achievement of the optimal levels of efficiency, advanced control systems techniques oer promise over more traditional approaches. Research into sliding mode control, and linear matrix inequalities with nite time boundedness and H∞ performance criteria, when applied to the dynamical models of the system, demonstrate the potential of these control methodologies as future avenues for achieving higher levels of performance and eciency in wind energy.
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Xu, Mingzhou. "A study of induction generator performance in a wave energy conversion system." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387930.
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Jovovic, Vladimir. "Engineering of Thermoelectric Materials for Power Generation Applications." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1248125874.
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Mondal, Abrez. "A PMSG-Based Wind Energy Conversion System Assisted by Photovoltaic Power." Thesis, North Dakota State University, 2012. https://hdl.handle.net/10365/26796.
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This work discusses a hybrid power conversion scheme consisting of a permanent magnet synchronous generator (PMSG)-based wind energy system and photovoltaic panels. The two energy sources are integrated with a battery to store extra photovoltaic energy during the day and to meet any additional power requirement in the absence of sunlight. The PV panel is interfaced to the battery through a SEPIC converter for maximum power point tracking. The wind energy from the PMSG is supplied to the battery through a boost converter which regulates the output. The total power obtained from the hybrid system is fed to a three-phase load through an inverter implementing Space-vector pulse-width modulation. The controller modeled in MATLAB/Simulink software is simple and is implemented through real time simulation using dSPACE hardware.NDSU Department of Electrical and Computer Engineering
Graduate School at North Dakota State University
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Maksimcev, Mirko D. "Energy considerations in power system damping by reactorcapacitor switching." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23370.
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Flexible AC transmission systems (FACTS) technology is an emerging new technology which can be efficiently used in power system damping. Objectives of this study are the considerations of the energy flow involved in power system damping by functional switching of series capacitors and/or reactors. The principal questions are how the energy transiently flows through the network and what is its impact on damping of mechanical oscillations.The analytical studies (covered in Chapter 1) reveal that the magnetic and electrostatic energy are constantly stored in the reactive components of the transmission system. The energy stored in a series compensated line is greater than the energy stored in an uncompensated line of equal transmission capability. The transient energy flow caused by characteristic switching in transmission systems is studied analytically in Chapter 2. Switching of an additional line or switching of series capacitors initiates transient charging/discharging of the line towards its new steady-state energy level which is always associated with losses. Power transfer characteristics of the systems which are equivalent in steady-state operation (parallel lines vs. an equivalent series compensated line) have quite different transient power transfer characteristics. These differences are related to different stored energies in such systems. System sources participate in all transient energy flow phenomena.
The impact of series compensation switching upon the mechanical oscillation damping was demonstrated by simulations presented in Chapter 3. Thyristor switched variable series compensation (VSC) is simulated in order to verify the conclusions of the analytical studies regarding the charging/discharging energy of the line.
The switching of reactive power components for the purpose of power system oscillation damping involves significant energy impulses in and out of the machines. Therefore, stability studies have to be performed by simulation which involves detailed representation of electromagnetic phenomena (EMTP for example).
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Zoric, I. "Multiple three-phase induction generators for wind energy conversion systems." Thesis, Liverpool John Moores University, 2018. http://researchonline.ljmu.ac.uk/8387/.
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During the past decade, there has been a considerable increase in the number of published works on multiphase machines and drives. This increased interest has been largely driven by a need for the so-called green energy, i.e. energy generated from renewable sources such as wind, and also an increased emphasis on greener means for transportation. Some of the advantages multiphase machines offer over three-phase counterparts are better fault tolerance, smaller current and power per phase, and higher frequency torque ripple. This thesis examines use of a multiphase induction generator in wind energy conversion systems (WECS). In particular, multiphase generators that comprise multiple 3-phase winding sets, where each winding set is supplied using an independent 3-phase voltage source inverter (VSI), are studied. It is claimed that these topologies offer advantages in cases where a WECS is connected to a multitude of independent ac or dc microgrids, systems where a single high-voltage dc link is needed or where a simple fault tolerance is achieved when a complete winding set is switched off. All of these examples require an arbitrary power or current sharing between winding sets. In order to achieve arbitrary current and power sharing, the control can be implemented using multi stator (MS) variables, so that the flux and torque producing currents of each winding set can be arbitrarily set. As an alternative, this thesis uses vector space decomposition (VSD) to implement the control, while individual winding set flux/torque producing currents are governed by finding the relationships between MS and VSD variables. This approach has all the advantages of both MS and VSD, i.e. access to individual winding set variables of MS and the ability to implement control in the multiple decoupled two dimensional subspaces of VSD, while heavy cross coupling between winding set variables, a weakness of MS, is avoided. Since the goal of the thesis is to present use of multiphase machines in WECS, modelling and simulation of a simple multiphase WECS in back-to-back configuration has been performed at first. All systems relevant to machine control where considered, such as grid and machine side VSIs, grid filter, indirect rotor field oriented control, current control in both flux/torque producing and non-producing subspaces, low order harmonic elimination, maximum power point tracking control, and voltage oriented control of the grid side VSI. Moreover, various WECS supply topologies were considered where developed current and power sharing would be a necessary requirement. Development of the proposed current sharing control commences with an analysis of multiple 3-phase machine modelling in terms of both MS and VSD variables. Since the actual control is implemented using decoupled VSD variables, VSD modelling has been studied in detail, resulting in an algorithm for creation of the VSD matrix applicable to any symmetrical or asymmetrical multiphase machine with single or multiple neutral points. Developed algorithm always decouples the machine into orthogonal two-dimensional subspaces and zero sequence components while making sure that all odd-order harmonics are uniquely mapped. Harmonic mapping analysis is offered as well. Next, relationship between MS and VSD variables has been developed by mapping MS variables into VSD subspaces. Since VSD matrix creation algorithm is valid for any multiphase machine, relationship between MS and VSD variables is applicable to any multiple 3-phase machine regardless of the configuration (symmetrical/asymmetrical), number of neutral points or machine type (synchronous or induction). Established relationship between MS and VSD has been used to implement current sharing control in decoupled VSD subspaces of the machine. It is shown that in order to achieve arbitrary current sharing it is only necessary to impose currents in flux/torque non-producing subspaces. Hence, total machine’s flux and torque are not affected at all. Besides verification by Matlab simulations, two topologies are experimentally investigated, a parallel machine side converter configuration and the case when a single high voltage dc link is created by cascading dc-links of the machine side VSIs. In the first case the ability of arbitrary current sharing between winding sets is validated, while the second tested topology demonstrates use of the developed control for the purpose of voltage balancing of the cascaded dc links.
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Kampfe, Sara Katherine. "Processing and Conversion of Algae to Bioethanol." W&M ScholarWorks, 2010. https://scholarworks.wm.edu/etd/1539626902.
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Yuen, Katarina. "System Perspectives on Hydro-Kinetic Energy Conversion." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-181555.
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Free-flowing water currents such as tides and unregulated water courses could contribute to world electricity production given the emergence of robust technical solutions for extracting the energy. At Uppsala University, a concept for converting the energy in water currents to electricity using a vertical axis turbine with fixed blade-pitch and a direct-drive permanent magnet generator is studied. Technological equipment for extracting energy from water currents can be studied at desktop to some extent, but physical realizations, first in a laboratory setting, and later in a natural aquatic setting, are necessary. For this reason, a laboratory generator has been constructed and evaluated, and an experimental setup comprising turbine, generator and control system has been constructed. The turbine and generator are to be deployed in the Dalälven River in Söderfors, and operated from an on-land control station. The author has worked with constructing and evaluating the low-speed laboratory generator, participated in the design and construction of the Söderfors generator, and designed and constructed the control system for Söderfors. The generator design incorporates a low rotational speed, permanent magnets, and many poles, in order to adapt the generator to the nature of water currents. Simulations and experimental data for the laboratory prototype have been compared and show that the simulation tool used is adequate for design studies of this type of generator. The generator has also been shown to be able to operate with the intended turbine design and range of water velocities. The control system to be used in Söderfors has been tested in a laboratory environment. Simulations of the control system show that it should be able to operate the turbine and generator at the desired rotational speeds in water velocities up to about 1.8 m/s. Simulations of the system have also shown that maximizing system power output may not correspond with maximizing turbine power.