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1
Ahmed, Faisal Mahmood. "Estimated Droop Control for Parallel Connected Voltage Source Inverters : Stability Enhancement". Thesis, Karlstads universitet, Avdelningen för fysik och elektroteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-30794.
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Renewable Energy Sources (RES) are considered as the replacement of conventionalenergy sources. These RES can use wind energy, solar light, bio waste and can alsobe in the form of small hydro power units. These RES has very poor power qualityand contains voltage uctuations and variable frequency. These factors make RES astability risk for the main utility grid. As a solution, currently inverters with dierentdesign techniques are being used as an interface between RES and main utility grid. Thecurrent study proposed a new technique "estimated droop control" for inverter design.The conventional droop control technique which was already used in inverter design, hasdiculty in synchronizing parallel connected inverters with dierent droop gains and lineimpedances. The proposed "estimated droop control" does not use any predened droopvalues for inverters and all inverters are responsible for the estimation of their own droopvalues with respect to their output power. Therefore, inverters are not bound to usesame and static droop values which are considered as a vital communication link. Theproposed design methodology has made inverters independent from this only virtual linkof communication due to which the reliability of a system has increased. The proposeddesign technique has given very good results in a simulation run. When the Simulinkmodel was run in parallel connected inverter with dierent line impedances, it was asuccess as both inverters started operating with same droop values as they were sharingan equal load. The most important test was with dierent line impedances because inconventional droop control it is dicult for inverters to keep their synchronism withdierent line impedances and an unequal load sharing make inverters to deviate fromtheir nominal values and to generate dierent tracking signals for each set. This problemhas been successfully solved with estimated droop control as in this method each inverterset its droop gains according to its output power, which helps an inverter to operate atnominal values with dierent droop gains and line impedance.
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Aluru, Radha Krishna. "Voltage Droop Analysis and Mitigation in STTRAM-based Last Level Cache". Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6455.
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Preferred especially for a Last Level Cache (LLC) due to its high retention and tolerance capabilities, Spin-Transfer Torque Random Access Memory (STTRAM) is an emerging and a promising Non-Volatile Memory (NVM) technology. To switch the magnetization of a Magnetic Tunnel Junction (MTJ), the amount of current needed is very high (~100μA per bit). For a full cache line (512-bit) write, this extremely high current results in a voltage droop in the conventional cache architecture. Due to this droop, the write operation fails especially when the farthest bank of the cache is accessed. In this thesis, we perform an analysis of the voltage droop across the STTRAM Last Level cache and then propose a new cache micro-architecture to mitigate the droop problem and make the write operations successful.
Instead of continuously writing the entire cache line (512-bit) in a single bank, the proposed architecture writes 64-bits in multiple physically separated locations across the cache. The voltage droop issue for crossbar memories such as Resistive RAM (ReRAM) has been pointed out but however, similar issue for STTRAM has never been investigated. In this study, we perform voltage droop analysis on the conventional STTRAM LLC while performing write/read operation with a simulation circuit model. Our investigation reveals that this problem exists for the write operation in a STTRAM LLC when we try to access the farthest bank in the cache. We propose a droop-mitigation Architecture which reduces the droop significantly. The effectiveness of this proposed architecture on the cache parameters such as latency and energy are compared with the conventional architecture for against various benchmarks. From the simulation results obtained (both circuit and micro-architectural), compared to the conventional architecture, the proposed architecture incurs 1.95% IPC and 5.21% energy for a 8MB last level cache.
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Butcher, Nicholas David. "Active Paralleling of High Power Voltage Source Inverters". Thesis, University of Canterbury. Electrical and Computer, 2007. http://hdl.handle.net/10092/3430.
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Power electronics are becoming established in ever broadening areas of industry. The transition from previous generation technology is driven by the oportunity for improvements in controllability, efficiency, and longevity. A wide variety of power semiconductors are available, however power handling capacity is still a significant limitation for many applications. An increase in the capacity of a single device is usually accompanied by a drop in switching frequency, and hence achievable system bandwidth. Increased capacity can be attained without this loss in bandwidth by using multiple lower power devices in parallel. Products based on parallel device topologies are already present in the marketplace, however there are many associated complications. The nature of these complications depends on the control method and topology used, but no system combines high performance and high power with high reliability and easy maintainability. This research aims to identify and develop a method that would provide a system of voltage source inverters with a total capacity in excess of 10MVA, with effective control bandwidth comparable to a 100kVA system. Additionally, the method should be equally applicable at still higher power levels in the future with the anticipated development of higher capacity power semiconductors. The primary goal when using paralleled devices is to achieve an even distribution of system load between them, as unbalanced load leads to poor system utilisation. Devices can be paralleled either passively, in which devices are controlled in common and characteristics inherent to the device are relied upon to balance load; or actively, in which devices are individually controlled and monitored to improve load balance. A key component of the thesis is the identification and analysis of the inadequacies inherent to passively paralleled systems. It is the limitations of passive paralleling that provide the motivation to develop an active parallel control mechanism. Following the analysis, an active control algorithm is developed and implemented on a paralleled system. The proposed system topology consists of an array of medium power Voltage Source Inverter (VSI) modules operating in parallel. Each module is controlled semi-independently at a local level, with an inter-module communications network to enable active equalisation of module load, and redundant fault management. An innovative load equalisatiion algorithm is developed and proven, the key feature of which is this inclusion of a synthetic differential resistance between modules within the system. The result is a modular expandable structure offering the potential for very high power capacity combined with quality of response usually only found in low power systems. The system as a whole is extremely reliable as any module can be isolated in the event of a fault without significantly affecting the remainder of the network. Performance results from both simulation and experimentation on a two module small scale prototype are given. Using the developed topology and control method extremely accurate load balancing can be achieved without degradation of the response characteristics. The system is tested up to only 2.4kW in the course of this research, but the correlation with simulation is high and gives confidence that the developed mechanism will allow the 10MV A goal to be achieved. Following the developmental stage of this research the technology has been applied to a commercial system comprising parallel structures of up to 8 modules with a total power handling capacity of 1MVA with no deterioration in performance. 2MVA systems are deliverable with the current technology without any changes, and higher power levels are expected to be easily achieved.
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Nord, Thomas. "Voltage Stability in an Electric Propulsion System for Ships". Thesis, KTH, Elektriska energisystem, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118932.
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This Master of Science thesis was written based on the shipbuilder Kockums AB feasibility study regarding the development of an All- Electric Ship for the Swedish Navy. The thesis was aiming at addressing voltage stability issues in a dc system fed by PWM rectifiers operating in parallel when supplying constant power loads. A basic computer model was developed for investigating the influence from various parameters on the system. It was shown that the voltage stability is dependent upon the ability to store energy in large capacitors. It was also shown that a voltage droop must be implemented maintaining load sharing within acceptable limits. Different cases of operation were modelled, faults were discussed, and the principal behaviour of the system during a short-circuit was investigated. It was shown that the short-circuit current is much more limited in this type of system in comparison to an ac system. It was concluded that more research and development regarding the components of the system must be performed.
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Chen, Fang. "Control of DC Power Distribution Systems and Low-Voltage Grid-Interface Converter Design". Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77532.
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DC power distribution has gained popularity in sustainable buildings, renewable energy utilization, transportation electrification and high-efficiency data centers. This dissertation focuses on two aspects of facilitating the application of dc systems: (a) system-level control to improve load sharing, voltage regulation and efficiency; (b) design of a high-efficiency interface converter to connect dc microgrids with the existing low-voltage ac distributions, with a special focus on common-mode (CM) voltage attenuation.
Droop control has been used in dc microgrids to share loads among multiple sources. However, line resistance and sensor discrepancy deteriorate the performance. The quantitative relation between the droop voltage range and the load sharing accuracy is derived to help create droop design guidelines. DC system designers can use the guidelines to choose the minimum droop voltage range and guarantee that the sharing error is within a defined range even under the worst cases.
A nonlinear droop method is proposed to improve the performance of droop control. The droop resistance is a function of the output current and increases when the output current increases. Experiments demonstrate that the nonlinear droop achieves better load sharing under heavy load and tighter bus voltage regulation. The control needs only local information, so the advantages of droop control are preserved. The output impedances of the droop-controlled power converters are also modeled and measured for the system stability analysis.
Communication-based control is developed to further improve the performance of dc microgrids. A generic dc microgrid is modeled and the static power flow is solved. A secondary control system is presented to achieve the benefits of restored bus voltage, enhanced load sharing and high system efficiency. The considered method only needs the information from its adjacent node; hence system expendability is guaranteed.
A high-efficiency two-stage single-phase ac-dc converter is designed to connect a 380 V bipolar dc microgrid with a 240 V split-phase single-phase ac system. The converter efficiencies using different two-level and three-level topologies with state-of-the-art semiconductor devices are compared, based on which a two-level interleaved topology using silicon carbide (SiC) MOSFETs is chosen. The volt-second applied on each inductive component is analyzed and the interleaving angles are optimized. A 10 kW converter prototype is built and achieves an efficiency higher than 97% for the first time.
An active CM duty cycle injection method is proposed to control the dc and low-frequency CM voltage for grounded systems interconnected with power converters. Experiments with resistive and constant power loads in rectification and regeneration modes validate the performance and stability of the control method. The dc bus voltages are rendered symmetric with respect to ground, and the leakage current is reduced. The control method is generalized to three-phase ac-dc converters for larger power systems.Ph. D.
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Tomaszewski, Michal. "Reactive power management capabilities of Swedish sub-transmission and medium voltage level grid". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240411.
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Rising penetration of renewable energy sources in electric power grids isboth a challenge and an opportunity to optimally utilize the potential of eitherwind or PV energy sources, to stabilize operation of future power systems.Bi-directional ows between distribution and transmission system operatorscause signicant problems with keeping the voltages in the grid within admissiblelimits. This paper contains description of Oland's island mediumandlow-voltage electric power grid, ranging from 0.4 kV to 130 kV in thepurpose of quasi-static analysis of active and reactive power ows in the system.Goal of the analysis is to optimize reactive power exchange at the pointof connection with the mainland grid. In the analyzed grid system, thereis an enormous, 190 % penetration of wind sources. Capacity of the windparks connected to dedicated buses totals to 136.1 MW, that supply up to90.5 MW of load. With industry-wise reactive power capability limits, totalcontribution of wind parks reaches almost 66 MVAr, enabling to compensatedecits and extra surpluses of the reactive power in the grid. Presentedsystem is connected to the mainland's grid through one point of connection,which is simulated as Thevenin equivalent circuit. Main objective of thethesis is to test and analyze viable solutions to minimize reactive power exchangeat the point of connection at Stavlo substation connecting Oland'sand Sweden's electric grid keeping valid all necessary contingencies enforcedby current grid codes applied in Sweden as well as thermal limits of the linesand voltage limits of the system. Furthermore, state of the art of currentreactive power compensation methodologies and most promising techniquesto eciently and eectively control reactive power ow are outlined. Droopcontrol methodologies, with focus on global and local objectives, and smartgrid solutions opportunities are being tested and modeled by the authors andare comprehensively presented in this paper. Moreover, economic costs ofcontrol methods are compared. Analysis of active power losses in the systemas well as cost of implementation of alternative solutions is presented, wheremost nancially viable solutions are outlined, giving brief outlook into futureperspectives and challenges of electric power systems. It is shown that controllabilityof reactive power support by wind turbine generators can enhanceoperation of electric power grids, by keeping the reactive power ow minimizedat the boundary between grids of distribution and transmission systemoperators. Furthermore, results indicate that extra reactive power supportby wind turbine generators can lead to diminishment of active power losses inthe system. Presented system is being modeled in the PSS/E software dedicatedfor power system engineers with use of Python programming languages.Analysis of data was done either in Python or R related environments. Thesiswas written with cooperation between KTH and E.On Energidistribution AB.Hogre genomslagskraft av förnyelsebara energikällor i elnäteten är bådeen utmaning och möjlighet för att optimalt kunna utnyttja potentialen av vindkraft och PV källor, med avseende på att stabilisera driften av framtida elkraftsystem. Tvåvägsflöden mellan distributionoch transmissionsoperatörer orsakar betydande problem att hålla spänningen i nätet inom tillåtna gränsvärden.Denna uppsats innehåller en beskrivning av Ö lands mellanoch lågspänningsnät,på 0.4 kV till 130 kV i syftet att utföra en kvasistatisk analys av aktiva och reaktiva effektflöden i systemet. Målet med analysen är att optimera det reaktiva effektutbytet i kopplingspunkten med fastlandets nät. I det analyserade systemet, finns det en enorm potential på 190% genomslagskraft av vindkraft. Kapaciteten på vindkraftsparker kopplade till medtagna samlingsskenor i systemet uppgår till 136,1 MW, som tillgodoser upp till 90.5 MW last. Med industrimässigt begränsad reaktiv effektkapabilitet, uppgår vindkraftsparkernas bidrag till nästan 66 MVAr, vilken möjliggör kompensation för underskott och överskott av reaktiv effekt i nätet. Det presenterade systemet är kopplat till fastlandet genom en kopplingspunkt, där fastlandet är simulerat som en Thevenin ekvivalent. Huvudsakliga målet med denna uppsats är att testa och analysera gångbara lösningar för att minimera det reaktiva effektutbytet vid kopplingspunkten i Stävlö, som kopplar ihop Ö land med resterande nät i Sverige, samtidigt som alla nödvändiga villkor enligt nuvarande nätkoder i Sverige bibehålls, liksom termiska gränser för ledningarna och spanningsgränser för systemet. Ytterligare beskrivs den bästa tillgängliga tekniken som finns idag för reaktiv effektkompensation, och de mest lovande teknikerna för att effektivt och verkningsfullt kontrollera reaktiva effektflöden. Droop-kontroll-metodologier, med fokus på globala och lokala tillämpningar, och smarta nät-möjligheter testas och modelleras av författarna och presenterar djupgående i detta arbete. Dessutom jämförs ekonomiska kostnader för olika kontrollmetoder. Analyser av aktiva effektförluster i systemet samt kostnader för implementation av alternativa lösningar presenteras, där de flesta gångbara losningar behandlas, och ger en överskådlig bild av framtida perspektiv och utmaningar i elkraftsystemet. Det visas att vindturbiners kontroll av reaktiv effekt, kan förbättra driften av elnäten, genom att minimera det reaktiva effektflödesutbytet i gränsen mellan distributionoch transmissionsoperatörers nät. Ytterligare pekar resultat på att extra understöd av reaktiv effekt från vindturbiner kan leda till förminskning av aktiva förluster i systemet. Det presenterade systemet modelleras i mjukvaruprogrammet PSS/E dedikerat för elkraftsingenjörer med hjälp av Python. Analys av data gjordes antingen i Pythoneller R-relaterade miljöer. Detta arbete har gjorts tillsam-mans med KTH och E.ON Energidistribution AB.
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Samadi, Afshin. "Large Scale Solar Power Integration in Distribution Grids : PV Modelling, Voltage Support and Aggregation Studies". Doctoral thesis, KTH, Elektriska energisystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154602.
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Long term supporting schemes for photovoltaic (PV) system installation have led to accommodating large numbers of PV systems within load pockets in distribution grids. High penetrations of PV systems can cause new technical challenges, such as voltage rise due to reverse power flow during light load and high PV generation conditions. Therefore, new strategies are required to address the associated challenges. Moreover, due to these changes in distribution grids, a different response behavior of the distribution grid on the transmission side can be expected. Hence, a new equivalent model of distribution grids with high penetration of PV systems is needed to be addressed for future power system studies. The thesis contributions lie in three parts. The first part of the thesis copes with the PV modelling. A non-proprietary PV model of a three-phase, single stage PV system is developed in PSCAD/EMTDC and PowerFactory. Three different reactive power regulation strategies are incorporated into the models and their behavior are investigated in both simulation platforms using a distribution system with PV systems. In the second part of the thesis, the voltage rise problem is remedied by use of reactive power. On the other hand, considering large numbers of PV systems in grids, unnecessary reactive power consumption by PV systems first increases total line losses, and second it may also jeopardize the stability of the network in the case of contingencies in conventional power plants, which supply reactive power. Thus, this thesis investigates and develops the novel schemes to reduce reactive power flows while still keeping voltage within designated limits via three different approaches: decentralized voltage control to the pre-defined set-points developing a coordinated active power dependent (APD) voltage regulation Q(P)using local signals developing a multi-objective coordinated droop-based voltage (DBV) regulation Q(V) using local signals In the third part of the thesis, furthermore, a gray-box load modeling is used to develop a new static equivalent model of a complex distribution grid with large numbers of PV systems embedded with voltage support schemes. In the proposed model, variations of voltage at the connection point simulate variations of the model’s active and reactive power. This model can simply be integrated intoload-flow programs and replace the complex distribution grid, while still keepingthe overall accuracy high. The thesis results, in conclusion, demonstrate: i) using rms-based simulations in PowerFactory can provide us with quite similar results using the time domain instantaneous values in PSCAD platform; ii) decentralized voltage control to specific set-points through the PV systems in the distribution grid is fundamentally impossible dueto the high level voltage control interaction and directionality among the PV systems; iii) the proposed APD method can regulate the voltage under the steady-state voltagelimit and consume less total reactive power in contrast to the standard characteristicCosφ(P)proposed by German Grid Codes; iv) the proposed optimized DBV method can directly address voltage and successfully regulate it to the upper steady-state voltage limit by causing minimum reactive power consumption as well as line losses; v) it is beneficial to address PV systems as a separate entity in the equivalencing of distribution grids with high density of PV systems.The Doctoral Degrees issued upon completion of the programme are issued by Comillas Pontifical University, Delft University of Technology and KTH Royal Institute of Technology. The invested degrees are official in Spain, the Netherlands and Sweden, respectively. QC 20141028
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Mohd, Daut Mohamad Hazwan. "Pico-grid : multiple multitype energy harvesting system". Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289426.
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This thesis focuses on the development of a low power energy harvesting system specifically targeted for wireless sensor nodes (WSN) and wireless body area network (WBAN) applications. The idea for the system is derived from the operation of a micro-grid and therefore is termed as a pico-grid and it is capable of simultaneously delivering power from multiple and multitype energy harvesters to the load at the same time, through the proposed parallel load sharing mechanism achieved by a voltage droop control method. Solar panels and thermoelectric generator (TEG) are demonstrated as the main energy harvesters for the system. Since the magnitude of the output power of the harvesters is time-varying, the droop gain in the droop feedback circuitry should be designed to be dynamic and self-adjusted according to this variation. This ensures that the maximum power is capable to be delivered to the load at all times. To achieve this, the droop gain is integrated with a light dependent resistor (LDR) and thermistor whose resistance varies with the magnitude of the source of energy for the solar panel and TEG, respectively. The experimental results demonstrate a successful variation droop mechanism and all connected sources are able to share equal load demands between them, with a maximum load sharing error of 5 %. The same mechanism is also demonstrated to work for maximum power point tracking (MPPT) functionality. This concept can potentially be extended to any other types of energy harvester. The integration of energy storage elements becomes a necessity in the pico-grid, in order to support the intermittent and sporadic nature of the output power for the harvesters. A rechargeable battery and supercapacitor are integrated in the system, and each is accurately designed to be charged when the loading in the system is low and discharged when the loading in the system is high. The dc bus voltage which indicates the magnitude of the loading in the system is utilised as the signal for the desired mode of operation. The constructed system demonstrates a successful operation of charging and discharging at specific levels of loading in the system. The system is then integrated and the first wearable prototype of the pico-grid is built and tested. A successful operation of the prototype is demonstrated and the load demand is shared equally between the source converters and energy storage. Furthermore, the pico-grid is shown to possess an inherent plug-and-play capability for the source and load converters. Few recommendations are presented in order to further improve the feasibility and reliability of the prototype for real world applications. Next, due to the opportunity of working with a new semiconductor compound and accessibility to the fabrication facilities, a ZnON thin film diode is fabricated and intended to be implemented as a flexible rectifier circuit. The fabrication process can be done at low temperature, hence opening up the possibility of depositing the device on a flexible substrate. From the temperature dependent I-V measurements, a novel method of extracting important parameters such as ideality factor, barrier height, and series resistance of the diode based on a curve fitting method is proposed. It is determined that the ideality factor of the fabricated diode is high (> 2 at RT), due to the existence of other transport mechanism apart from thermionic emission that dominates the conduction process at lower temperature. It is concluded that the high series resistance of the fabricated diode (3.8 kΩ at RT) would mainly hinder the performance of the diode in a rectifier circuit.
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Ferreira, Rodrigo Arruda Felício. "Controle de microrredes CC baseado em droop adaptativo de tensão – simulação em tempo real com control-hardware-in-loop". Universidade Federal de Juiz de Fora (UFJF), 2015. https://repositorio.ufjf.br/jspui/handle/ufjf/4173.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Este trabalho apresenta um estudo sobre alguns dos aspectos relacionados às microrredes em corrente contínua, uma alternativa para utilização de fontes renováveis de energia em sistemas de geração distribuída. Considerando que a manutenção da tensão no barramento principal das microrredes, no qual as fontes e as cargas são conectadas, é uma das questões mais importantes para a operação de modo satisfatório destes sistemas, um sistema de controle descentralizado de tensão integrando técnicas de controle por droop de tensão e de controle por modos deslizantes é proposto. Uma microrrede CC de 10 kW conectada à rede CA e composta por arranjos fotovoltaicos e bancos de baterias, dimensionada para atender uma parcela das cargas eletrônicas e de iluminação do Instituto Federal de Educação, Ciência e Tecnologia – Campus Juiz de Fora, é modelada e simulada em tempo real utilizando o conceito de simulação CHIL. Resultados experimentais utilizando controladores externos como dispositivos em teste são utilizados para analisar o comportamento do sistema em diferentes condições e para validação da metodologia proposta. Além disso, é apresentado um estudo das técnicas de análise de estabilidade de tensão para sistemas em corrente contínua. Por fim, é apresentada uma metodologia baseada em síntese de elementos reativos utilizando conversores estáticos para estabilização ativa de sistemas CC simplificados, contendo uma fonte e uma carga do tipo potência constante.
This work presents aspects related to DC microgrids, an alternative way of using renewable energy sources in a decentralized fashion. Whereas the maintenance of the microgrid main bus voltage, in which the sources and loads are connected, is one of the most important issues for the satisfactory operation of these systems, a novel methodology for regulating DC bus voltage integrating voltage droop control and sliding mode control techniques is proposed. A grid-connected 10 kW DC microgrid containing photovoltaic arrays and a battery bank, sized to meet a portion of electronic and lighting loads of the Federal Institute of Education, Science and Technology - Campus Juiz de Fora, is modeled and simulated in real time using the concept of CHIL simulation. Experimental results using external controllers as hardware under test are used to analyze system behavior under different conditions and to validate the proposed methodology. Furthermore, a study regarding voltage stability analysis techniques applied to DC systems is presented. Finally, a methodology based on synthesis of reactive elements using static converters for active stabilization of simplified CC systems, containing one source and one constant power load, is presented.
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Tazay, Ahmad F. "Smart Inverter Control and Operation for Distributed Energy Resources". Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/7097.
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The motivation of this research is to carry out the control and operation of smart inverters and voltage source converters (VSC) for distributed energy resources (DERs) such as photovoltaic (PV), battery, and plug-in hybrid electric vehicles (PHEV). The main contribution of the research includes solving a couple of issues for smart grids by controlling and implementing multifunctions of VSC and smart inverter as well as improving the operational scheme of the microgrid. The work is mainly focused on controlling and operating of smart inverter since it promises a new technology for the future microgrid. Two major applications of the smart inverter will be investigated in this work based on the connection modes: microgrid at grid-tied mode and autonomous mode.
\indent In grid-tied connection, the smart inverter and VSC are used to integrate DER such as Photovoltaic (PV) and battery to provide suitable power to the system by controlling the supplied real and reactive power. The role of a smart inverter at autonomous mode includes supplying a sufficient voltage and frequency, mitigate abnormal condition of the load as well as equally sharing the total load's power. However, the operational control of the microgrid still has a major issue on the operation of the microgrid. The dissertation is divided into two main sections which are:
1- Low-level control of a single smart Inverter.
2- High-level control of the microgrid.
The first part investigates a comprehensive research for a smart inverter and VSC technology at the two major connections of the microgrid. This involves controlling and modeling single smart inverter and VSC to solve specific issues of microgrid as well as improve the operation of the system. The research provides developed features for smart inverter comparing with a conventional voltage sourced converter (VSC). The two main connections for a microgrid have been deeply investigated to analyze a better way to develop and improve the operational procedure of the microgrid as well as solve specific issues of connecting the microgrid to the system.
A detailed procedure for controlling VSC and designing an optimal operation of the controller is also covered in the first part of the dissertation. This section provides an optimal operation for controlling motor drive and demonstrates issues when motor load exists at an autonomous microgrid. It also provides a solution for specific issues at operating a microgrid at autonomous mode as well as improving the structural design for the grid-tied microgrid. The solution for autonomous microgrid includes changing the operational state of the switching pattern of the smart inverter to solve the issue of a common mode voltage (CMV) that appears across the motor load. It also solves the issue of power supplying to large loads, such as induction motors. The last section of the low-level section involves an improvement of the performance and operation of the PV charging station for a plug-in hybrid electric vehicle (PHEV) at grid-tied mode. This section provides a novel structure and smart controller for PV charging station using three-phase hybrid boost converter topology. It also provides a form of applications of a multifunction smart inverter using PV charging station.
The second part of the research is focusing on improving the performance of the microgrid by integrating several smart inverters to form a microgrid. It investigates the issue of connecting DER units with the microgrid at real applications. One of the common issues of the microgrid is the circulating current which is caused by poor reactive power sharing accuracy. When more than two DER units are connected in parallel, a microgrid is forming be generating required power for the load. When the microgrid is operated at autonomous mode, all DER units participate in generating voltage and frequency as well as share the load's power. This section provides a smart and novel controlling technique to solve the issue of unequal power sharing. The feature of the smart inverter is realized by the communication link between smart inverters and the main operator. The analysis and derivation of the problem are presented in this section.
The dissertation has led to two accepted conference papers, one accepted transaction IEEE manuscript, and one submitted IET transaction manuscript. The future work aims to improve the current work by investigating the performance of the smart inverter at real applications.
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Madduri, Sailaja. "MNoC a network on chip for monitors /". Connect to this title, 2008. http://scholarworks.umass.edu/theses/215/.
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Ziouani, Islam. "Commande hiérarchique optimisé pour les générateurs distribuées dans les microréseaux intelligents". Thesis, CY Cergy Paris Université, 2020. http://www.theses.fr/2020CYUN1083.
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Ce travail porte sur le développement d'un schéma de commande optimisé pour la gestion de la puissance générée par les générateurs distribués hétérogènes et les sources d'énergie renouvelable constituant un microrésau intelligent.Un microrésau est un système énergétique distribué associant des sources d'énergie renouvelables et des générateurs distribués, ainsi que des charges locales. Il peut échanger de l'électricité avec le réseau électrique et peut fonctionner de manière autonome.L'utilisation idéale d'un microrésau consiste à alimenter des régions ou des sites éloignés dans l'incapacité d'accéder au réseau public. En outre, les exploitants d’entreprises s’intéressent davantage à l’utilisation des microréseaux pour la production d’électricité, en raison de leur durabilité, de leur fiabilité et de leur rentabilité.Les générateurs distribués tels que les dispositifs de stockage d'énergie et les générateurs diesel sont des générations contrôlables qui peuvent ajuster leur puissance de sortie en fonction des besoins de la charge, tandis que les sources d'énergie renouvelable telles que les éoliennes et les panneaux photovoltaïques sont des générations non contrôlables qui exploitent leur puissance maximale.En ce sens, nous avons proposé une solution basée sur une approche hiérarchique composée de trois niveaux : interne, primaire et secondaire. Cette solution est capable de contrôler les générateurs distribués dans un microréseau pour alimenter les consommateurs locaux sans aucune interruption et pour échanger une puissance avec le réseau électrique tout en exploitant au maximum l’énergie renouvelables.La commande interne est responsable de la régulation de la tension de sortie de chaque générateur distribué, basée sur une commande en cascade et un contrôleur à résonance proportionnelle. La commande primaire génère la tension de référence de la commande interne dont le rôle principal est de coordonner les générateurs distribués de manière décentralisée afin de partager la demande de puissance active et de puissance réactive entre eux. La commande secondaire compense l'écart de tension par rapport aux valeurs nominales et synchronise la tension du microréseau avec le réseau principal pour une transition en douceurThis work focuses on the development of an optimized control scheme for managing the power generated by heterogeneous distributed generators (DGs) and renewable energy sources (RESs) that constituting a smart microgrid.A microgrid is a distributed energy system that gathering a combination of renewable energy sources and distributed generators, as well as local loads. It can exchange power with the utility grid, and it can operate autonomously. The ideal use of a microgrid is to supply remote regions or locations that are unable to access the public grid. Moreover, utility operators become more interested in using microgrids for producing electricity due to their sustainability, reliability, and cost-effective.The DGs such as energy storage devices and diesel generators are dispatchable generations that can adjust their output power according to the load needs, whereas, the RESs such as wind turbines and photovoltaic panels are non-dispatchable generations which are used to exploit their maximum power.In this sense, we have proposed a solution based on the hierarchical approach that consists of three levels, inner, primary and secondary. This solution is able to control DGs in a hybrid microgrid for supplying continuously the local consumers without any interruption and for exchanging a smooth power with the utility grid while exploiting the maximum power from the renewables.The inner control is responsible to regulate the output voltage of each distributed generator which is based on cascaded control and Proportional-resonant controller.The primary control generates the reference voltage of the inner control which its principal role is to coordinate the distributed generators in a decentralized manner to share the active and the reactive power demand among them.The secondary control compensates the voltage deviation toward the nominal values as well as it synchronizes the microgrid voltage with the main grid for a smooth transition
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Ahmadi, Seyedhesam y Mehrdad Bahmani. "Reglering av effektflöde i HVDC-system genom centraliserad och distribuerad spänningskontroll i realtid". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254267.
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“High voltage direct current” (HVDC) teknologi har blivit allt viktigare teknik för att integrera förnybara energikällor i elnätet. För att styra ett sådant elsystem på bästa möjliga sätt krävs optimala kontrollstatergier både för omvandlarna och nätet. Så syftet med detta projekt är att undersöka hur olika regleringsmetoder, såsom centraliseradoch distribuerad spänningskontroll, kan påverka driften i ett 4-terminal HVDC-system. Ett optimalt effektflöde uppstår i systemet endast när likspänningen inte avviker från sitt börvärde och det uppnås genom att ha aktiv effekt regulator i varje nod i nätet. Olika scenarier som ändring av effektens börvärde och omvandlaravbrott har simulerats med hjälp av HIL-processen i realtid. Simuleringarna hjälper till att analysera hur väl dem implementerade regleringsmetoder i nodernas regulatorer hantera dessa förändringar. Resultatet ger bevis på att både centraliseradoch distruebued metoden har positiva och negativa aspekter. Fördelen med centraliserade metoden är att den ger en väldefinierad operationspunkt men den hanterar den inte svåra transienter (tex. avbrott) vilket distribuerade metoden gör.
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Johansson, Henrik y Lucas Tunelid. "Operation and Control of HVDC Grids". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293882.
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In order to meet the increasing demand ofenergy in today’s society while at the same time minimizing theenvironmental impact, renewable energy sources will be requiredto be integrated into the existing energy mix. Technologicaladvances in high voltage direct current (HVDC) grids playa crucial role in making this possible. Therefore the purposeof this project has been to validate the properties of basiccontrol strategies in terms of how they respond to four differentsimulation cases. All simulations have been conducted on asimplified version of the CIGR ́E B4 test grid, consisting offour monopolar HVDC converters. After analyzing the resultsobtained from each control strategy it became evident thatprovided if the benefits of the redundancy introduced by amulti-terminal grid are to be fully utilized, a distributed voltagecontrol should be used. Moreover, after substituting one ofthe four internal controllers with an external one, it becameclear that simply deciding the droop constants based on resultsfrom the simulation model wouldn’t be sufficient for real worldapplications.För att möta det ökande energibehovet i dagens samhälle, samtidigt som energiproduktionens miljöpåverkan ska minimeras, krävs det att förnyelsebara energikällor integreras i den existerande energimixen. Tekniska framsteg inom högspända likströmsnät (HVDC) spelar en avgörande roll i att göra detta möjligt. Därför har syftet med detta projekt varit att validera egenskaperna hos grundläggande kontrollstrategier efter hur dem reagerar på fyra olika simuleringsfall. Alla simuleringar har genomförts på en förenklad version av CIGRE´ B4 testsystem, bestående av fyra monopolära HVDC omriktare. Efter att analyserat de erhållna resultaten från varje kontrollstrategi blev det uppenbart att om fördelarna med multiterminala elnät skulle uppnås, bör en distribuerad spänningskontroll användas. Dessutom, efter att ha bytt ut en av dem fyra interna kontrollerna med en extern, visade det sig att endast bestämma droppkonstanterna baserat på resultat från simuleringsmodellen inte är tillräckligt för verkliga applikationer.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
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Denis, Guillaume. "Les nouvelles stratégies de contrôle d’onduleurs pour un système électrique 100% interfacé par électronique de puissance". Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0020/document.
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Dans un contexte de développement des énergies renouvelables et des liaisons HVDC dans les systèmes électriques, les travaux présentés s’attachent au fonctionnement technique de tels systèmes. La génération éolienne, photovoltaïque et les liaisons HVDC sont interfacées par dispositifs d’électronique de puissance au réseau de transport électrique. Dès lors, serait-il envisageable d’alimenter la demande électrique uniquement via des sources électriques interfacées par des convertisseurs statiques ?Le pilotage du système électrique par électronique de puissance constitue un changement radical du fonctionnement dynamique des réseaux. La traditionnelle stratégie de commande « grid-following » des onduleurs a montré ses limites lorsque la pénétration de ces dispositifs devient importante. Elle doit être révisée au profit de stratégies dîtes « parallel grid-forming ».Dans cette thèse, les besoins fondamentaux du système électrique sont d’abord analysés pour définir les exigences de la stratégie « parallel grid-forming », ainsi que les défis associés. Selon ces spécifications, une méthode de synchronisation de sources « grid-forming » est ensuite proposée ainsi qu’un contrôle de tension, adapté aux limitations physiques des convertisseurs de tension PWM. La stabilité de la solution est discutée pour différentes configuration de réseau. Enfin, une stratégie de limitation du courant a été spécifiquement développée pour palier la sensibilité des VSC aux sur courants, lors d’évènements réseaux éprouvant. Les idées développées sur un convertisseur unique sont appliquées à petits réseaux afin d’extraire des interprétations physiques depuis des simulations temporellesIn the context of renewable energy and HVDC links development in power systems, the present work concerns the technical operations of such systems. As wind power, solar photovoltaics and HVDC links are interfaced to the transmission grid with power-electronics, can the system be operated in the extreme case where the load is fed only through static converters?Driving a power system only based on power electronic interfaced generation is a tremendous change of the power system paradigm that must be clearly understood by transmission grid operators. The traditional “grid-feeding” control strategy of inverters exhibits a stability limit when their proportion becomes too important. The inverter control strategy must be turned into a “parallel grid-forming” strategy.This thesis first analyses the power system needs, proposes the requirements for “parallel grid-forming” converters and describes the associated challenges. Accordingly, the thesis gives a method for designing a stable autonomous synchronization controls so that grid-forming sources can operate in parallel with a good level of reliability. Then, a method is proposed to design a voltage control for a grid-forming PWM source taking into account the limited dynamic of large converters. The robustness of the solution is discussed for different configuration of the grid topology. A current limiting strategy is presented to solve the current sensitivity issue of grid-forming converters, subject to different stressing events of the transmission grid. The ideas developed on a single converter are then applied on small grids with a limited number of converters to allow a physical interpretation on the simulation results
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Carter-Brown, Clinton Geoffrey. "Voltage drop apportionment in Eskom's distribution networks". Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5258.
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Shinoda, Kosei. "Contrôle et opération des réseaux HVDC multi-terminaux à base de convertisseurs MMC". Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0017.
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Cette thèse porte sur la commande de réseaux multi-terminaux à courant continu (MTDC) basés sur des convertisseurs multiniveaux modulaires (MMCs).Tout d’abord, notre attention se focalise sur l'énergie stockée en interne dans le MMC qui constitue un degré de liberté additionnel apporté par sa topologie complexe. Afin d’en tirer le meilleur parti, les limites de l’énergie interne sont formulées mathématiquement.Afin de maîtriser la dynamique de la tension DC, l’utilisation de ce nouveau degré de liberté s’avère d’une grande importance. Par conséquent, une nouvelle de stratégie de commande, nommée «Virtual Capacitor Control», est proposée. Cette nouvelle méthode de contrôle permet au MMC de se comporter comme s’il possédait un condensateur de taille réglable aux bornes, contribuant ainsi à l’atténuation des fluctuations de la tension DC.Enfin, la portée de l’étude est étendue au réseau MTDC. L'un des défis majeurs pour un tel système est de faire face à une perte soudaine d'une station de convertisseur qui peut entraîner une grande variation de la tension du système. A cet effet, la méthode de statisme de tension est la plus couramment utilisée. Cependant, l'analyse montre que l'action de contrôle souhaitée risque de ne pas être réalisée lorsque la marge disponible de réserve de puissance du convertisseur est insuffisante. Nous proposons donc une nouvelle structure de contrôle de la tension qui permet de fournir différentes actions en fonction du signe de l'écart de la tension suite à une perturbation, associée à un algorithme qui détermine les paramètres de statisme en tenant compte du point de fonctionnement et de la réserve disponible à chaque stationThe scope of this thesis includes control and management of the Modular Multilevel Converter (MMC)-based Multi-Terminal Direct Current (MTDC).At first, our focus is paid on the internally stored energy, which is the important additional degree of freedom brought by the complex topology of MMC. In order to draw out the utmost of this additional degree of freedom, an in-depth analysis of the limits of this internally stored energy is carried out, and they are mathematically formulated.Then, this degree of freedom of the MMC is used to provide a completely new solution to improve the DC voltage dynamics. A novel control strategy, named Virtual Capacitor Control, is proposed. Under this control, the MMC behaves as if there were a physical capacitor whose size is adjustable. Thus, it is possible to virtually increase the equivalent capacitance of the DC grid to mitigate the DC voltage fluctuations in MTDC systems.Finally, the scope is extended to MMC-based MTDC grid. One of the crucial challenges for such system is to cope with a sudden loss of a converter station which may lead to a great variation of the system voltage. The voltage droop method is commonly used for this purpose. The analysis shows that the desired control action may not be exerted when the available headroom of the converter stations are insufficient. We thus propose a novel voltage droop control structure which permits to provide different actions depending on the sign of DC voltage deviation caused by the disturbance of system voltage as well as an algorithm that determines the droop parameters taking into account the operating point and the available headroom of each station
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Rincon-Mora, Gabriel Alfonso. "Current efficient, low voltage, low drop-out regulators". Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/13359.
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Palma, David João Nunes. "Design of future distribution grids". Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/11110.
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Dissertação para obtenção do Grau de Mestre em
Engenharia Electrotécnica e de ComputadoresThis work presents the concept of voltage control in power distribution systems with distributed generation and electric vehicles penetration. The impact of DG and EV in the voltage supply is investigated. DG provides more power into the system, which can cause the inversion of the load flow and an increase in the voltage supply when the demand is low. EVs on the other hand are additional load in distribution systems, increasing power demand and voltage drop. Both might be a cause of voltage problems in the power supply, when no voltage control is applied. Devices such as the tap-changer transformer or the voltage regulator which were not essential in the past are now important solutions to solve voltage variation issues. In this work, several different solutions for voltage control are analyzed, both technically and economically. Overall, the results show that different strategies have different outcomes, and some solutions provide better voltage control than others. In order to have a proper solution for a system, when choosing a control strategy, it is necessary to always take into account the cable ampacity, the technical limits of each device and the costs associated with it.
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Gaeb, Jassim Abdulah. "Control of reactive compensation on transmission systems". Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236704.
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Mehryoon, Shah M. "Analysis and Comparison of Power Loss and Voltage Drop of 15 kV and 20 kV Medium Voltage Levels in the North Substation of the Kabul Power Distribution System by CYMDIST". Ohio University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1258137124.
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Milliken, Robert Jon. "A capacitor-less low drop-out voltage regulator with fast transient response". Texas A&M University, 2005. http://hdl.handle.net/1969.1/3275.
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Power management has had an ever increasing role in the present electronic industry.
Battery powered and handheld applications require power management techniques to extend the
life of the battery and consequently the operation life of the device. Most systems incorporate
several voltage regulators which supply various subsystems and provide isolation among such
subsystems. Low dropout (LDO) voltage regulators are generally used to supply low voltage,
low noise analog circuitry. Each LDO regulator demands a large external capacitor, in the range
of a few microfarads, to perform. These external capacitors occupy valuable board space,
increase the IC pin count, and prohibit system-on-chip (SoC) solutions.
The presented research provides a solution to the present bulky external capacitor LDO
voltage regulators with a capacitor-less LDO architecture. The large external capacitor was
completely removed and replaced with a reasonable 100pF internal output capacitor, allowing
for greater power system integration for SoC applications. A new compensation scheme is
presented that provides both a fast transient response and full range ac stability from a 0mA to
50mA load current. A 50mA, 2.8V, capacitor-less LDO voltage regulator was fabricated in a
TSMC 0.35um CMOS technology, consuming only 65uA of ground current with a dropout
voltage of 200mV.
Experimental results show that the proposed capacitor-less LDO voltage regulator exceeds
the current published works in both transient response and ac stability. The architecture is also
less sensitive to process variation and loading conditions. Thus, the presented capacitor-less
LDO voltage regulator is suitable for SoC solutions.
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Johari, Pritesh N. "Distributed Decap-Padded Standard Cell based On-Chip Voltage Drop Compensation Framework". University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1235504983.
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Ng, Hoi Sum. "Petri nets for fault diagnosis and distribution automation". Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366530.
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Larsson, Niclas. "Spänningsfall i 200 V 400 Hz system". Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105189.
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Målet med examensarbetet har varit att ta fram teoretiskt underlag och en beräkningsmodell. Detta ska beskriva hur kabeltyp, kabellängd, kabelarea samt effektfaktor påverkar spänningsfallet över ett 400 Hz ledningssystem. Mätningar har utförts på två olika kablar som används i det aktuella systemet. En av kablarna var symmetriskt uppbyggd med 7 ledare, där respektive fas bestod av två ledare förskjutna 180° från varandra runt nolledaren. För att åstadkomma 115/200V 400 Hz, användes en 90 kVA frekvensomformare. Belastningen som användes var en resistiv, induktiv samt en kapacitiv belastning. Med den resistiva belastningen justerades effekten för att ställa in den effektfaktor som önskades under mätningarna. Detta var inte möjligt med den induktiva eller den kapacitiva belastningen, då de inte kunde regleras steglöst. Beräkningsmodellen jämfördes sedan med mätningarna av spänningsfallet. Den visade sig ge en bra uppskattning av de uppmätta värdena för att kunna användas i Saabs fortsatta arbete. Vidare ges förslag på hur de distorsioner som uppstår, i samband med komplexa laster, kan minskas. Detta för att klara de standardiserade mått på elkvaliteten som ställs i de gällande standarderna MIL-STD-704E och ISO 6858-1982 (E). Beräkningsmodellen och dess beräkningar presenteras dock inte i denna rapport, då det av Saab AB är sekretessbelagda.The goal with this bachelor thesis has been to present theoretical material and a calculation model. This is to be used to explain how cable type, cable length, cable area affects the voltage drop in a 400 Hz power system. Measurements have been made on two different cables that are being used in the current system. One of the cables was built symmetrically built with 7-conduktors, where each phase consisted of two conductors shifted 180° from each other around the neutral conductor. To establish the system voltage 115/200 V 400 Hz, a 90 kVA frequency converter was used. The load that was used under the measurements was a resistive, inductive and a capacitive load-equipment. With the resistive load active power is adjusted to obtain the proper power factor for different measurements. This was not an option with the inductive or the capacitive load-equipment since they could not be regulated with a rheostat as the resistive load. The calculation model was compared with the measured results of the voltage drop. It was proven that it approximated the voltage drop good enough to be used in Saabs future work. Furthermore, suggestions are made of how to minimize the distortions that are developed by complex loads, to clear the demands on power quality presented by the standards MIL-STD-704E and ISO 6858-1982 (E).
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Harizi, Hedi [Verfasser]. "Full Chip Dynamic Voltage Drop Analysis Using Automated Abstractions of Cell and Block Properties / Hedi Harizi". München : Verlag Dr. Hut, 2010. http://d-nb.info/1009095439/34.
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Jolly, Mohanjit Singh. "A voltage drop study in a megawatt level quasi-steady magnetoplasma dynamic thruster via probe diagnostics". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/46420.
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Buono, Benedetto. "Simulation and Characterization of Silicon Carbide Power Bipolar Junction Transistors". Doctoral thesis, KTH, Integrerade komponenter och kretsar, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95320.
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The superior characteristics of silicon carbide, compared with silicon, have suggested considering this material for the next generation of power semiconductor devices. Among the different power switches, the bipolar junction transistor (BJT) can provide a very low forward voltage drop, a high current capability and a fast switching speed. However, in order to compete on the market, it is crucial to a have high current gain and a breakdown voltage close to ideal. Moreover, the absence of conductivity modulation and long-term stability has to be solved. In this thesis, these topics are investigated comparing simulations and measurements. Initially, an efficient etched JTE has been simulated and fabricated. In agreement with the simulations, the fabricated diodes exhibit the highest BV of around 4.3 kV when a two-zone JTE is implemented. Furthermore, the simulations and measurements demonstrate a good agreement between the electric field distribution inside the device and the optical luminescence measured at breakdown. Additionally, an accurate model to simulate the forward characteristics of 4H-SiC BJTs is presented. In order to validate the model, the simulated current gains are compared with measurements at different temperatures and different base-emitter geometries. Moreover, the simulations and measurements of the on-resistance are compared at different base currents and different temperatures. This comparison, coupled with a detailed analysis of the carrier concentration inside the BJT, indicates that internal forward biasing of the base-collector junction limits the BJT to operate at high current density and low forward voltage drop simultaneously. In agreement with the measurements, a design with a highly-doped extrinsic base is proposed to alleviate this problem. In addition to the static characteristics, the comparison of measured and simulated switching waveforms demonstrates that the SiC BJT can provide fast switching speed when it acts as a unipolar device. This is crucial to have low power losses during transient. Finally, the long-term stability is investigated. It is observed that the electrical stress of the base-emitter diode produces current gain degradation; however, the degradation mechanisms are still unclear. In fact, the analysis of the measured Gummel plot suggests that the reduction of the carrier lifetime in the base-emitter region might be only one of the causes of this degradation. In addition, the current gain degradation due to ionizing radiation is investigated comparing the simulations and measurements. The simulations suggest that the creation of positive charge in the passivation layer can increase the base current; this increase is also observed in the electrical measurements.QC 20120522
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Elrayyah, Ali Y. "Modeling and Control of Microgrid-Connected Photo-Voltaic Sources (MCPV)". University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1384345552.
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Hinde, David Derek. "Corona discharges on the surfaces of high voltage composite insulators". Queensland University of Technology, 2009. http://eprints.qut.edu.au/29320/.
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The degradation of high voltage electrical insulation is a prime factor that can significantly influence the reliability performance and the costs of maintaining high voltage electricity networks. Little information is known about the system of localized degradation from corona discharges on the relatively new silicone rubber sheathed composite insulators that are now being widely used in high voltage applications.
This current work focuses on the fundamental principles of electrical corona discharge phenomena to provide further insights to where damaging surface discharges may localize and examines how these discharges may degrade the silicone rubber material. Although water drop corona has been identified by many authors as a major cause of deterioration of silicone rubber high voltage insulation until now no thorough studies have been made of this phenomenon.
Results from systematic measurements taken using modern digital instrumentation to simultaneously record the discharge current pulses and visible images associated with corona discharges from between metal electrodes, metal electrodes and water drops, and between waters drops on the surface of silicone rubber insulation, using a range of 50 Hz voltages are inter compared. Visual images of wet electrodes show how water drops can play a part in encouraging flashover, and the first reproducible visual images of water drop corona at the triple junction of water air and silicone rubber insulation are presented.
A study of the atomic emission spectra of the corona produced by the discharge from its onset up to and including spark-over, using a high resolution digital spectrometer with a fiber optic probe, provides further understanding of the roles of the active species of atoms and molecules produced by the discharge that may be responsible for not only for chemical changes of insulator surfaces, but may also contribute to the degradation of the metal fittings that support the high voltage insulators.
Examples of real insulators and further work specific to the electrical power industry are discussed. A new design concept to prevent/reduce the damaging effects of water drop corona is also presented.
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Mehryoon, Shah M. "Analysis and comparison of power loss and voltage drop of 15 kV and 20 kV medium voltage levels in the north substation of the Kabul power distrubution system by CYMDIST". Ohio : Ohio University, 2009. http://www.ohiolink.edu/etd/view.cgi?ohiou1258137124.
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Bjurelid, Martin y Emran Murina. "Analys & kartläggning av Uddevalla citys mellanspänningsnät". Thesis, Högskolan Väst, Avdelningen för data-, elektro- och lantmäteriteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-8291.
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Kraven på ett driftsäkert elnät ökar hela tiden i takt med att elanvändning blir allt viktigare i dagens samhälle. Luftledningar byts ut med markkabel och möjlighet till reservmatningar samt bra elkvalitet är av hög prioritering. Skicket på elnätets utrustning försämras med åren och kommer med tiden behöva bytas ut. Med uppdrag från Uddevalla Energi AB har siffror tagits fram berörande spänningsfall, kapacitiv jordfelsström och belastningar vid normaldrift och reservmatning, samt ålder och typ på kablar i Uddevalla citys mellanspänningsnät. Den här rapporten presenterar dessa resultat och ger några förslag på ändringar om så krävs. Även en del om planerade framtida utbyggnationer tas upp och hur dessa påverkar nätet. För att få fram resultaten används Uddevalla Energis program för nätberäkning, "DpPower". Beräkningarna visade att vid normaldrift var alla värden godkända enligt tumregler som Uddevalla Energi följer. Vid reservmatning däremot var vissa linjer överbelastade, analysen visar dock tillgängliga lösningar. Ålder och status på kablar i nätet varierar stort vilket gör det svårt att specificera hur ombyggnationer ska ske. Hänsyn bör istället tas till överbelastningar.The demand of reliable power distribution is increasing as the usage of power is increasing in the society of today. Overhead lines are replaced by underground cables, availability to reserve power supply and power quality is of high priority. The condition of the equipment deteriorates over the years and will eventually have to be replaced. By request from Uddevalla Energi, values have been provided concerning voltage drop, capacitive ground fault current and loads during normal operation and standby power supply. The types and ages of cables in Uddevalla City’s high-voltage network has also been looked at. This report presents these results and gives some suggestions for modifications if required. Planned future deployments are looked over and how these may affect the network. To obtain these results the network calculating program "DpPower" was used. The calculations presented shows that in normal operation all values are approved within the company standards that Uddevalla Energi follows. For the reserve supply however, some lines are overloaded. The analysis shows possible solutions for these issues. Age and status of cables in the network varies widely, making it difficult to specify how redevelopments should take place. Instead the overloads should be given more consideration.
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Ochoa, Pizzali Luis Fernando. "Desempenho de redes de distribuição com geradores distribuídos /". Ilha Solteira : [s.n.], 2006. http://hdl.handle.net/11449/100362.
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Orientador: Antonio Padilha FeltrinBanca: Rubén Augusto Romero Lázaro
Banca: Dionízio Paschoareli Júnior
Banca: Gareth Harrison
Banca: Carmen Lucia Tancredo Borges
Resumo: Neste trabalho, é apresentada uma análise em regime permanente que considera a avaliação de impactos técnicos tais como perdas elétricas, queda de tensão e níveis de curto-circuito, entre outros; utilizando dados de demanda e geração variáveis no tempo ao longo de um horizonte determinado. O objetivo é encontrar um conjunto de arranjos da GD (configurações) que levem ao melhor desempenho da rede de distribuição analisada, minimizando ou maximizando cada aspecto técnico segundo o interesse da empresa de distribuição. Dada a natureza combinatória deste problema, que requer uma ferramenta de otimização capaz de manipular múltiplos objetivos, os impactos técnicos serão avaliados simultaneamente utilizando uma metodologia baseada no conceito do Non-dominated Sorting Genetic Algorithm (NSGA), conduzindo a soluções mais reais e diversificadas para a tomada de decisões, conhecidas como soluções ótimas de Pareto.
Abstract: In this work a steady-state analysis considering the assessment of technical impacts such as losses, voltage drop and short-circuit levels, among others; utilizing time-variant loads and generation within a specified horizon. The objective is to find a set of configurations that lead to the best performance of the distribution network under analysis, minimizing or maximizing each technical aspect according to the utility's concerns. Given the combinatorial nature of this problem, which requires an optimization tool able to handle multiple objectives, technical impacts will be assessed simultaneously through a methodology based on the non-dominated sorting genetic algorithm (NSGA). This approach leads to a more realistic and diversified set of solutions for taking decisions, known as Pareto-optimal solutions.
Doutor
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Ochoa, Pizzali Luis Fernando [UNESP]. "Desempenho de redes de distribuição com geradores distribuídos". Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/100362.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Ensino Pesquisa e Extensão de Ilha Solteira (FEPISA)
Neste trabalho, é apresentada uma análise em regime permanente que considera a avaliação de impactos técnicos tais como perdas elétricas, queda de tensão e níveis de curto-circuito, entre outros; utilizando dados de demanda e geração variáveis no tempo ao longo de um horizonte determinado. O objetivo é encontrar um conjunto de arranjos da GD (configurações) que levem ao melhor desempenho da rede de distribuição analisada, minimizando ou maximizando cada aspecto técnico segundo o interesse da empresa de distribuição. Dada a natureza combinatória deste problema, que requer uma ferramenta de otimização capaz de manipular múltiplos objetivos, os impactos técnicos serão avaliados simultaneamente utilizando uma metodologia baseada no conceito do Non-dominated Sorting Genetic Algorithm (NSGA), conduzindo a soluções mais reais e diversificadas para a tomada de decisões, conhecidas como soluções ótimas de Pareto.
In this work a steady-state analysis considering the assessment of technical impacts such as losses, voltage drop and short-circuit levels, among others; utilizing time-variant loads and generation within a specified horizon. The objective is to find a set of configurations that lead to the best performance of the distribution network under analysis, minimizing or maximizing each technical aspect according to the utility's concerns. Given the combinatorial nature of this problem, which requires an optimization tool able to handle multiple objectives, technical impacts will be assessed simultaneously through a methodology based on the non-dominated sorting genetic algorithm (NSGA). This approach leads to a more realistic and diversified set of solutions for taking decisions, known as Pareto-optimal solutions.
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Lee, Hyung-Seok. "Fabrication and Characterization of Silicon Carbide Power Bipolar Junction Transistors". Doctoral thesis, Stockholm : Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4623.
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Oliveira, Janaina Prieto de. "Eficiência da crescente estimulação elétrica de média voltagem em meias carcaças Bos taurus indicus no final do abate na qualidade do contrafilé durante a maturação". Botucatu, 2020. http://hdl.handle.net/11449/192905.
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Orientador: Roberto de Oliveira RoçaResumo: Esse estudo objetivou avaliar a eficiência de estímulos elétricos com tensões crescentes durante a estimulação de meias carcaças no final do abate na qualidade do contrafilé até 28 dias de maturação. Metade das meias carcaças esquerdas de 40 novilhos Nelore (Bos taurus indicus), não castrados, com predomínio de cobertura de gordura mediana, foram submetidas ao Protocolo A (20, 40, 60 e 80 VRMS) e a outra metade foi submetida ao Protocolo B (50 VRMS). Ambos os protocolos com 12,5 Hz durante 52 segundos. As respectivas meias carcaças direitas não foram estimuladas (Controle A e Controle B). O pH e a temperatura das meias carcaças foram monitorados durante as 40 horas de resfriamento (1, 3, 6, 9, 12, 24 e 40 horas) e os respectivos contrafilés foram maturados por 2, 7, 14, 21 e 28 dias post-mortem. As duas combinações de estimulação elétrica de média voltagem aceleraram a taxa de declínio do pH (refletido na temperatura e no tempo que o pH cai para 6), resultando em valores médios para força de cisalhamento de 4,66 kgf pra o Protocolo A e 4,62 kg para o Protocolo B com diferença entre seus controles os quais apresentaram 5,36 kg e 5,29 kg respectivamente, mantendo essa característica durante a maturação. O comprimento dos sarcômeros não foi diferente (P>0,05) entre os protocolos e seus controles. O uso da estimulação elétrica com tensões crescentes não resultou em melhores características qualitativas da carne em relação a estimulação elétrica de tensão contínua. A força da esti... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This study was aimed to evaluate the efficiency of electrical stimulation with increasing voltage during the stimulation of bovine half carcasses on the quality of 28 days aged strip loins. Half of the left half carcasses from 40 Nellore steers (Bos taurus indicus), intact, from the same feedlot, with median fat coverage, were submitted to Protocol A (20, 40, 60 and 80 VRMS) and the other half to Protocol B (50 VRMS). Both protocols with 12.5 Hz for 52 seconds. The respective right half carcasses were not stimulated (Control A and Control B). The pH and temperature were monitored during 40 hours of cooling (1, 3, 6, 9, 12, 24 and 40 hours) and the strip loins were aged for 2, 7, 14, 21, and 28 days post-mortem. Both combinations of medium voltage electrical stimulation accelerated the pH decline rate (reflected in temperature and the time that pH drop to 6), resulting in lower values for shear force 4.66 kgf for Protocol A, and 4.62 for Protocol B, with 5.36 kgf and 5,29 kgf for its respectively controls, maintaining this characteristic during aging time. The length of the sarcomere was not different (P>0.05) between the protocols and their controls. The use of an electrical stimulation with increasing tensions did not result in better qualitative characteristics of the meat in comparison to the continuous tension electrical stimulation. The strength of the electrical stimulation, the visual contractions, and the pH difference area (∆pH) did not have a proportional effect on ... (Complete abstract click electronic access below)
Mestre
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Lu, Jingjing. "Caractérisation du comportement du plasma dans un disjoncteur basse tension par le développement d'un outil numérique et d'expériences associées". Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30154.
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Les processus liés à la segmentation de l'arc et à la quantification des chutes de tension additionnelles sont les phénomènes prépondérants à la compréhension et à l'optimisation des Disjoncteurs Basse Tension (DBT). Le but de nos travaux est d'appréhender leurs comportements par l'expérience et leurs représentations par l'outil numérique. Pour cela une modélisation magnétohydrodynamique tridimensionnelle (3D) est réalisée sur une géométrie simplifiée de DBT. Les développements sont basés sur le code commercial Ansys @Fluent agrémenté d'UDF (User Define Functions). Afin d'étudier et d'isoler les mécanismes, les travaux expérimentaux et numériques sont réalisés sur une maquette simplifiée constituée de deux électrodes en parallèle et de la présence optionnelle de séparateurs. Numériquement la tension additionnelle, provenant de la présence des gaines aux interfaces plasma/matériau, est prise en compte par une méthode approchée basée sur la caractéristique théorique d'une variation de la tension en fonction de la densité de courant. Cette résistivité additionnelle permet une représentation du passage du courant vers les matériaux et du retard à la commutation sur le séparateur en fonction de la chute de tension. Les travaux ont été menés entre deux rails en utilisant un et deux séparateurs. Côté expérimental, le comportement de l'arc est caractérisé par des mesures électriques (Tension, courant) et par des acquisitions de la caméra rapide. L'amorçage de l'arc est initié par un fil fusible en cuivre de 0.1 mm. La géométrie étudiée peut être plus ou moins fermée à ses extrémités afin de mettre en évidence les effets des forces de pression et/ou des forces de Lorentz. Une bonne analogie de la description du comportement de l'arc est retrouvée entre les résultats du modèle et les résultats expérimentaux. Cependant les conditions initiales du modèle s'avèrent prépondérantes et dans les mêmes temps délicats à déterminerThe arc splitting process and the quantification of additional voltage drops are the major phenomena to understand and to optimize the Low Voltage Circuit Breaker (LVCB). The aim of our work is to understand their behavior through experiments and then their representation by our model. Therefore, a three-dimensional (3D) magnetohydrodynamic modeling is carried out on a simplified LVCB geometry. The developments are based on the commercial code Ansys @Fluent with UDF (User Define Functions). The plasma is described by fluid equations and a finite volume method. To study and isolate the mechanisms, the experimental and numerical work were realized on a simplified geometry, composed by two parallel electrodes with or without splitter plates. Numerically, the additional voltage resulting from the sheaths at the plasma/material interfaces, is considered by an approximate method based on the theoretical characteristic of voltage variation, as the function of current density. This additional resistivity allows to present the current flow in the materials and create some delay at the switching during the splitting process. Further to the experiments, the arc behavior is characterized by electrical measurements (Voltage, current) and by high-speed camera. The arc ignition is realized by a copper fuse of 0.1 mm. The geometry can be more or less closed at its both extremities in order to highlight the effects of pressure force and/or Lorentz force. The description of arc behavior was found similar between the simulation and experiments results. However, the initial conditions of our model proved to be preponderate while at the same time, the conditions remained delicate to determine
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Svoboda, Ondřej. "Návrh elektrizace jednokolejné trati". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-400599.
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The main topic of the thesis is the design of single-track electrification of a direct current system of 3 kV and an alternating current system of 5 kV 50 Hz and then economically evaluate it over a period of 30 years. The work deals with basic traction systems and also deals with the calculation of main parameters of electric trains. The thesis describes in detail the procedure for the design of the electrification of the track and a partial introduction to the simulation programs that were used for energy calculations.
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Ureh, Henry Chigozie. "IMPACTS OF PLUG-IN ELECTRIC VEHICLE ON RESIDENTIAL ELECTRIC DISTRIBUTION SYSTEM USING STOCHASTIC AND SENSITIVITY APPROACH". DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/642.
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Plug-in Electric Vehicles (PEVs) are projected to become a viable means of transportation due to advances in technology and advocates for green and eco-friendly energy solutions. These vehicles are powered partially, or in some cases, solely by the energy stored in their battery packs. The large sizes of these battery packs require large amount of energy to charge, and as the demand for PEV increases, the increase in energy demand needed to recharge these PEV batteries could pose problems to the present electric distribution system. This study examines the potential impacts of PEV on a residential electric distribution system at various penetration levels.
An existing residential distribution network is modeled up to each household service point and various sensitivity scenarios and stochastic patterns of PEV loads are simulated. Impact studies that include voltage drop, service transformers overload, energy loss, and transformer thermal loss-of-life expectancy are analyzed. Results from the study are reported and recommendations to mitigate the impacts are presented.
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Račuch, Marek. "Analýza a návrh náhrady konkrétního venkovního vedení distribuční sítě". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-319302.
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The diploma thesis deals with the issue of the reconstruction of outdoor cables of low voltage distribution network in exchange for the cable line. It analyzes the important factors which are necessary for the preparation of the project documentation for the issue of the territorial consent. The thesis is divided into 4 main chapters. After the first chapter there is introduced chapter 2, which shows the differences between cable and outdoor cables with their advantages and disadvantages. Chapter 3 deals with the guiding principles for low-voltage cable design and the types of equipment needed for the proper operation of a particular distribution network while respecting the requirements of valid PNEs and ČSNs. Chapter 4 explains the chronology of the process leading to the formulation of a basic technical proposal, which is further addressed in Chapter 5, which deals with the complete formulation of the project documentation for the issue of territorial consent.
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Löfgren, Louise. "Elbilsladdnings påverkan på elnätet : Simuleringar av Gävles lokala elnät med olika laddningsmönster". Thesis, Högskolan i Gävle, Energisystem och byggnadsteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-36846.
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Transportsektorn står inför en omställning från förbränningsfordon till eldrivna fordon. Detta är en åtgärd för att minska koldioxidutsläppet inom transportsektorn och därmed reducera klimatpåverkan. Syftet med studien är att undersöka hur en ökad effektanvändning i form av elbilsladdning påverkar Gävles lokala elnät samt hur olika laddtekniker påverkar elnätet. Bakgrunden till studien grundar sig att elnätsföretaget vill öka medvetenheten om hur elnätets beredskap ser ut för en ökad elbilsladdning. Att undersöka elbilsladdningens påverkan på elnätet är av stor nytta för elnätsföretaget, men även andra som undersöker elbilsladdnings påverkan i elnätet kan ha användning för studien. Ämnet elbilsladdning är mycket aktuellt och många studier undersöker olika delar som berör elbilsladdning. Tidigare studier undersöker även olika typer av laddtekniker och hur smart laddning minska påverkan i elnätet. Smart laddning kan anpassa elbilsladdningen genom att styra den efter olika styrsignaler och sammankoppla hela elnätet. Denna studie undersöker delar av Gävles lokala elnät genom att simulera befintliga mätvärden lågspänningsnätet samt olika typer av elbilsladdning. Studien analyserar effektanvändningen av befintliga mätdata samt belastningsström och spänningsfall i elnätet med varierande lastprofiler i fyra olika områden. Resultatet för denna studie visar att elbilsladdning påverkar elnätet, vilket beror på vilken typ av laddteknik som används samt dimensioneringen av elnätet. Studien visar att elanvändningen i området idag har effekttoppar på eftermiddag och kväll när kunderna består av villakunder men att effekttoppen kan vara mitt på dagen där det finns industrier. Med elbilsladdning ökar belastningen samt spänningsfallet i nätet och en del av säkringarna i nätet löser ut. Laddning med 11 kW mellan kl. 16:00-19:00 samt laddning med effektvakt på 13,8 kW ger störst belastning och spänningsfall. Laddning utan styrning är den laddteknik som påverkar elnätet mest men laddning med effektvakt orsakar också problem. Laddning med 5,5 kW mellan kl. 23:00-06:00 samt när endast 50% av alla kunder laddar med 11 kW mellan kl. 16:00-19:00 är de scenarion som påverkar elnätet minst. Laddning med en låg effekt under natten när grundlasten är som lägst är den laddteknik som är mest gynnsam för elnätet. Studien visar även att nätet klarar en högre belastning av elbilsladdning inom en snar framtid om endast en del av kunderna i nätet använder elfordon.The transport sector is facing a transition from combustion engine vehicles to electric vehicles. Through this action the carbon dioxide emissions in the transport sector can be reduced. The purpose of this study is to observe how an increased power use from electric vehicle charging (EVC) affects the local electricity grid in Gävle. The study also addresses how different charging techniques affect the electricity grid. The background of this study is to the increase awareness of the capacity of the electricity grid. There is a need from the electricity grid company to look over the impact on the grid from EVC. This could also be useful for others looking over the impact on the electricity grid from EVC. This is a hot topic and lots of other studies look over the different aspects of EVC. Previous studies also examine different types of charging techniques and how smart charging reduces the negative impact on the electricity grid. Smart charging is a way to adjust the EVC by regulating it after different parameters and connecting the entire electrical grid. This study simulates existing measured values of the low-voltage grid in Gävle and various types of EVC. This study examines the power use of existing measurement data as well as load current and voltage drops in the electricity grid with different load profiles in four different areas. Results from this study shot that EVC affects the electricity grid, to what extent depends on the type of charging technology used and the dimensions of the electricity grid. The study shows that electricity use in the area has power peaks in the afternoon and evening with residential customers, but power peaks tend to be in the middle of the day if there are industries in the area. EVC increase the load on the electricity grid, causes voltage drops and a few fuses in the grid to be triggered. Charging with 11 kW between 16:00-19:00 and charging with a power monitor of 13.8 kW create the greatest voltage drops and highest load on the grid. Charging without means of control affects the electricity grid the most but charging with a power monitor also creates problems. Charging with 5.5 kW between 23:00-06:00 as well as when only 50 % of all customers charge with 11 kW between 16:00-19:00 impacts the grid the least. Charging with low power during the night when the base load is at its lowest is the charging technology that is most favorable for the electricity grid. Results also show that the grid can handle a higher load of EVC in the near future if only some of the customers in the network start using electric vehicles.
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Fiala, Martin. "Elektrické sítě využívající stejnosměrné napětí do 1000 V". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-241980.
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This master´s thesis deals with the proposal of DC low voltage network at a voltage level of 1000 V DC in Praskolesy u Mrakotina village. Direct distribution will be realized only at the terminal, which will power the village. Next part of this thesis is theoretical and its main focus is description of both DC and AC distribution systems. The proposed DC grid will use existing distribution grid. The thesis further describes the problems of long terminals in low voltage distribution systems and electrical installation in buildings. The result of this work is a comparison of the losses between AC and the proposed DC system. The last part deals with economical evaluation and technical solution for the proposed network variant, including their advantages and disadvantages.
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Cederholm, Sebastian y Nizarki Bafrin Hussein. "Elnätets kapacitet för framtida belastningar från elbilar : En känslighetsanalys på ett av Halmstads lokalnät". Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-31173.
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Regeringen har en vision att till 2050 ska Sverige uppnå en fordonsflotta som är fossilfri och för att uppnå den visionen ska el som drivmedel spela en avgörande roll på marknaden. HEM Nät AB är därmed intresserade av hur deras lokalnät i ett valt område kan påverkas när en större andel av hushållen införskaffar elbilar. Längs områdets högspänningsslinga finns nio nätstationer som matar ut effekt till 815 kunder. En känslighetsanalys genomfördes kring det valda lokalnätet med avseende till dess kapacitet idag till framtida belastningar från elbilar. Analysen baserades på fyra olika nätparametrar som möjligen kan riskeras med avseende till elbilars laddsystem: spänningsfall, transformatorbelastning, övertoner och osymmetri. Olika laddeffekter och kopplingssätt har även jämförts bland nätparametrarna för att visa vilken roll de kan ha i framtiden. Spänningsfallet samt transformatorbelastning för de båda effekterna 3,7 kW och 11 kW uppgick mot de satta nätkraven när 40 % respektive 20 % belastning sker i området. Två vetenskapliga metoder användes för att uppskatta övertonerna där ena tog hänsyn till en reduktion av sammanlagrade övertoner och den andra metoden använde en aritmetisk summering av strömövertonerna. Resultatet visade att med varken en inkluderad reduktion eller med den aritmetiska summeringen kommer övertonerna bli ett problem. Med simuleringen av osymmetri nåddes nätkravet när 7 % mer belastning skedde under en och samma fas. Slutligen kom studien fram till att lokalnätet är relativt starkt och kan klara av 322 elbilar vid 3,7 kW och 161 elbilar vid 11 kW.The Swedish government have a vision that up untill 2050 Sweden’s transport system is going to be free of fossil fuels and to achieve this vision, electricity is going to be the main fuel and will play a decisive role in the future transportional market. As a result of this, HEM Nät AB is now interested in knowing how their local electrical grid will be affected by a larger amount of electric vehicles, EVs, charged through households. Along the local grid’s high voltage line there are nine substations, which provide power to 815 customers. A sensitivity analysis was conducted on the local grid to appreciate the available capacity for the future load of EVs. The analysis was based on four different gridparameters, which possibly can affect the set conditions of an electrical grid when an EV is being charged: voltage drop, transformer load, harmonics and dissymmetry. Different chargepowers and wirings have also been compared to see what roles they will have in the future. After the simulations and hand calculations all of the gridparameters exceeded the set conditions. This happened at different percentages of the households, which were charging their vehicles. The voltage drop and transformer load for both of the powers, 3,7 kW and 11 kW exceeded the limitations when 40 % respectively 20 % of the studied are was being loaded. Two scientific methods were used to appreciate the added current harmonics, where the first one regarded a reduction of the summarized value of the current harmonics, where the second did not. The results showed, that either of the methods would indicate a problem on the grid. The simulation of the dissymmetry, the limitation was met after 7 % more load was done under one and the same of the phases. Finally, the study concluded that the local grid is relatively strong and can hold 332 EVs with 3,7 kW and 161 EVs with 11 kW.
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Cathelin, Joël. "Contribution à la commande sans capteur mécanique de la machine synchrone à aimants permanents". Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112349.
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La commande sans capteur mécanique de la machine synchrone à aimants permanents est un sujet largement répandu dont les plus grandes difficultés connues, quel que soit l’observateur utilisé, sont celui du démarrage à vitesse nulle et plus largement de la commande aux basses vitesses, et celui du rejet des fortes perturbations du couple. Afin d’y faire obstacle, diverses adaptations des algorithmes d’observateur ont été proposées afin d’améliorer le comportement de la machine en commande sans capteur. Par ailleurs, il est couramment admis que les déchets de tension produit par l’onduleur sont nuisibles à l’observation de la position, les tensions de référence étant légèrement différentes des tensions appliquées aux enroulements de la machine. Quelques propositions apparaissent dans certaines publications notamment en établissant un algorithme de compensation. C’est ainsi que les travaux de cette thèse portent sur cette thématique, celle d’améliorer la commande sans capteur dans les situations d’observabilité difficile en proposant une solution originale afin de faire correspondre au mieux les tensions appliquées à la machine et les tensions de référence utiles à l’observateur. Les résultats montrent que la solution proposée et largement analysée améliore considérablement le comportement de la machine en commande aux basses vitesses et en rejet de perturbation, tant en régime permanent qu’en régime transitoire ; une analyse de Fourier des courants mesurés atteste l’efficacité de la méthode et une analyse des grandeurs observées par la statistique descriptive met en lumière l’intérêt de l’algorithme. Nous montrons ainsi que la solution proposée permet d’observer la vitesse et la position en deçà de la vitesse mécanique de 15 rad/s alors que la commande est instable en deçà de 20 rad/s quand la solution n’est pas mise en œuvre. Un constat similaire apparaît en rejet de perturbation. D’autres résultats montrent que l’observation à plus basse vitesse est entachée d’une perturbation liée à un couple pulsatoire dont l’origine peut être le couple de détente, lequel n’est pas pris en compte par le modèle de la machineThe sensorless control of the permanent magnet synchronous machine is a subject widely spread. Two great difficulties are known; (i) the start at nil initial speed and more generally the control at very low speed whatever the observer used and (ii) the high torque disturbance rejection. In order to hinder these difficulties numerous modifications of observer algorithms were proposed to improve the performances of the permanent magnet synchronous machine sensorless control. Moreover, we admit commonly that the drop voltages due to the inverter are prejudicial to the position estimated, because the difference between the voltage reference transmitted to the PWM (pulse width modulation) and the motor winding voltage is not negligible at low speed and low load torque. According to the literature, several papers propose some solutions by compensation algorithms and voltage estimator in particular. So, the goal of this thesis is to estimate the winding voltage and to apply the state observer by Extended Kalman Filtering to improve more finely the sensorless control. We propose an original solution to estimate the voltage references which is applied to the observer. Numerous experimental results show the attractive effects in marked contrast to the sensorless control results without estimation of the winding voltages. The results of sensorless control show that the solution proposed which widely analysed improves significantly the estimation errors of the motor running in low speed range and low torque disturbances range. Fourier analyses and statistic data obtained in steady state speed and results during the transient response indicate complementary results and highlight the interest of the estimation algorithm. Our study brings out that the estimation error reduction allows to running the motor at mechanical speed short of 15 rad/s. In the other hand, the system is instable with speed short of 20 rad/s if the voltage references are used by the observer rather than the estimation voltages. The same improvement appears in disturbance rejection. Other results show that the estimated position errors at lower speed increases in spite of the estimation algorithm. In fact, the torque disturbances are dominant at low speed, low load torque and are harmful to control the electromagnetic torque
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Gatu, Andreas y Alexander Svensson. "Justerbar modell av transmissionsledning för elkraftsöverföring". Thesis, KTH, Data- och elektroteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166735.
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Detta examensarbete har utförts på uppdrag av Terco. Tercos PST 2220Transmission Line and Distribution Module fungerar som en fysisk modellav ett verkligt transmissions- eller distributionsnät där fem olika typer av nätmed avseende på längd, spänningsnivå och skenbar effekt är möjliga. Idagfinns ett behov av en modell där användaren kan ställa in dessa parametrarså att modellen mer precist kan spegla vilka egenskaper det specifika nätethar. Här undersöks hur längden och dess inverkan på en ledning kan varierasi en modell.En presentation av hur transmissions- och distributionsnät fungerar ochbeskrivs teoretiskt lägger grunden till den modell och de två approximationersom kan beskriva ett helt näts egenskaper.Då R, L och C komponenterna behöver kunna varieras för att fysisktkunna realisera denna teoretiska modell undersöks vilka metoder som dettakan genomföras på. För detta undersöks två tillvägagångssätt, kaskadkopp-lad pi-modell och variabel aktiv-passiv reaktans.Flera aspekter som utrymme, kostnad och variabilitet gör att varia-bel aktiv-passiv reaktans är att föredra. Dess funktion som en varierbarspänningskälla, uppbyggd av switchar styrda med reglerteknik och puls-breddsmodulering gör att komponenterna R, L och C och dess egenskaperoch inverkan på en transmissionslinje kan åstadkommas. Resultatet är attde nödvändiga R,L,C komponenterna går att variera i storlek för att kunnaingå i en varierbar transmissionsledningsmodell.Resultatet och målen säkerställs med simuleringar där variabel aktiv-passiv reaktans visas kunna vidareutvecklas och praktiskt testas för att mo-dellera transmissions- och distributionsnät med olika längd. Nyckelord. Variabilitet, Inverterare, Impedans, DC-AC, Pulsbreddsmodu-lering, Övertoner, Transmissionsledning, Spänningsfall, Reaktiv effekt.This diploma work has been carried out on behalf of Terco. TercosPST 2220 Transmission Line and Distribution Module works as a physicalmodel of a real transmission and distribution grid where five different typesof networks based on length, voltage and apparent effect are available. Thereis today a need of a model where the user self can adjust these parameters sothat the model more precisely can reflect the characteristics that the specificgrid has. Here it’s investigated how the length and its impact on a line canbe varied in a model.A presentation of how the transmission and distribution grid works andare described theoretically provides the basics for the different models thatcan describe a whole network and its properties.Since the R, L and C components needs to be able to be varied to be ableto physically realize this theoretical model, the different methods that thiscan be realized through are investigated. Two approaches are investigated,the cascaded pi-model and variable active-passive reactance (VAPAR).A number of aspects like space, cost and variability makes the variableactive-passive reactance the most suited solution. Its function as a variablevoltage source, made out of an four switches, operated with control techno-logy and pulse width modulation, makes it possible to imitate R, L and Csproperties and effect on a transmission line. The result is that the necessaryR,L,C components are made adjustable in order to be incorporated in aadjustable transmission lin model.The result and the goal are verified with simulations where variableactive-passive reactance is proved able for further development and practicaltests to model transmission and distribution lines with different length. Keywords. Variability, Inverter, Impedance, DC-AC, Pulse width modula-tion, Harmonics, H-bridge, Transmission line, Voltage drop, Reactive effect.
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Dostál, Lukáš. "Simulace nadproudové spouště jističe". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218784.
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Securing of electrical devices is important not only to protect against destruction under the effects of electric current, but also for protection of people or animals against electric shock. With increasing of living standards goes hand in hand increasing of the electricity consumption. Therefore In the grid of low voltage, there are increasing short-circuit currents. With improving technology is posed considerable demand on the performance, security and switching capacity of circuit breakers. This thesis is oriented on development of thermal and electromagnetic switch of circuit breaker on which is put a big demand in development of new types of circuit breakers. The thesis is interesting because of comprehensive use of circuits’ breakers since it can be used in AC and DC networks with frequency of 50 Hz and 400 Hz.
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LIN, CHUN-CHAN y 林群展. "Applying Programmable Voltage Droop Method in Implementation of Half Bridge Resonant Converter with Redundancy". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/5e5f67.
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碩士聖約翰科技大學
電機工程系碩士在職專班
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This thesis presents an application of 1+1 redundant power supply by using a SRC series type resonant converter for Server system. For the improvement of input power factor (PF), the configuration circuit consists of boost converter for Power Factor Correction (PFC) and operating in Continuous Current Mode (CCM) to achieve a high power factor and low input current harmonic requirement. A half-bridge type of SRC series resonant converter provides a Zero Voltage Switching (ZVS) feature for primary side MOSFET, and Zero Current Switching (ZVS) feature for secondary side rectifiers then reduce switching losses. With the specified resonant tank and component design, the circuit can be achieving a high efficiency converter as its advantage of this topology. Furthermore, this paper provides a simply voltage droop method to implement redundant performance of power supply. For the accuracy concern of Current-sharing for Droop method, it’s presenting an improvement idea of Programmable Voltage Droop method to meet common requirement for Server teams. Keywords: SRC / LLC half-bridge type series resonant converter, Redundant power supply, Zero Voltage Switching / Zero Current Switching technique, Programmable Voltage Droop Method.
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"Hybrid AC-High Voltage DC Grid Stability and Controls". Doctoral diss., 2017. http://hdl.handle.net/2286/R.I.46197.
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abstract: The growth of energy demands in recent years has been increasing faster than the expansion of transmission facility construction. This tendency cooperating with the continuous investing on the renewable energy resources drives the research, development, and construction of HVDC projects to create a more reliable, affordable, and environmentally friendly power grid.
Constructing the hybrid AC-HVDC grid is a significant move in the development of the HVDC techniques; the form of dc system is evolving from the point-to-point stand-alone dc links to the embedded HVDC system and the multi-terminal HVDC (MTDC) system. The MTDC is a solution for the renewable energy interconnections, and the MTDC grids can improve the power system reliability, flexibility in economic dispatches, and converter/cable utilizing efficiencies.
The dissertation reviews the HVDC technologies, discusses the stability issues regarding the ac and HVDC connections, proposes a novel power oscillation control strategy to improve system stability, and develops a nonlinear voltage droop control strategy for the MTDC grid.
To verify the effectiveness the proposed power oscillation control strategy, a long distance paralleled AC-HVDC transmission test system is employed. Based on the PSCAD/EMTDC platform simulation results, the proposed power oscillation control strategy can improve the system dynamic performance and attenuate the power oscillations effectively.
To validate the nonlinear voltage droop control strategy, three droop controls schemes are designed according to the proposed nonlinear voltage droop control design procedures. These control schemes are tested in a hybrid AC-MTDC system. The hybrid AC-MTDC system, which is first proposed in this dissertation, consists of two ac grids, two wind farms and a five-terminal HVDC grid connecting them. Simulation studies are performed in the PSCAD/EMTDC platform. According to the simulation results, all the three design schemes have their unique salient features.Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2017
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Kim, Youngtaek. "Characterization and management of voltage noise in multi-core, multi-threaded processors". Thesis, 2013. http://hdl.handle.net/2152/25185.
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Reliability is one of the important issues of recent microprocessor design. Processors must provide correct behavior as users expect, and must not fail at any time. However, unreliable operation can be caused by excessive supply voltage fluctuations due to an inductive part in a microprocessor power distribution network. This voltage fluctuation issue is referred to as inductive or di/dt noise, and requires thorough analysis and sophisticated design solutions. This dissertation proposes an automated stressmark generation framework to characterize di/dt noise effect, and suggests a practical solution for management of di/dt effects while achieving performance and energy goals. First, the di/dt noise issue is analyzed from theory to a practical view. Inductance is a parasitic part in power distribution network for microprocessor, and its characteristics such as resonant frequencies are reviewed. Then, it is shown that supply voltage fluctuation from resonant behavior is much harmful than single event voltage fluctuations. Voltage fluctuations caused by standard benchmarks such as SPEC CPU2006, PARSEC, Linpack, etc. are studied. Next, an AUtomated DI/dT stressmark generation framework, referred to as AUDIT, is proposed to identify maximum voltage droop in a microprocessor power distribution network. The di/dt stressmark generated from AUDIT framework is an instruction sequence, which draws periodic high and low current pulses that maximize voltage fluctuations including voltage droops. AUDIT uses a Genetic Algorithm in scheduling and optimizing candidate instruction sequences to create a maximum voltage droop. In addition, AUDIT provides with both simulation and hardware measurement methods for finding maximum voltage droops in different design and verification stages of a processor. Failure points in hardware due to voltage droops are analyzed. Finally, a hardware technique, floating-point (FP) issue throttling, is examined, which provides a reduction in worst case voltage droop. This dissertation shows the impact of floating point throttling on voltage droop, and translates this reduction in voltage droop to an increase in operating frequency because additional guardband is no longer required to guard against droops resulting from heavy floating point usage. This dissertation presents two techniques to dynamically determine when to tradeoff FP throughput for reduced voltage margin and increased frequency. These techniques can work in software level without any modification of existing hardware.text
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"Detailed voltage droop analysis of power supply and delivery network for inter- and intra-chip systems: 多核心及多芯片系統的電源傳輸網絡之詳細電壓驟降分析". 2015. http://repository.lib.cuhk.edu.hk/en/item/cuhk-1291601.
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Siu, Wing Oi.Thesis M.Phil. Chinese University of Hong Kong 2015.
Includes bibliographical references (leaves 70-73).
Abstracts also in Chinese.
Title from PDF title page (viewed on 28, October, 2016).
Siu, Wing Oi.