Global ETD Search

111	Photovoltaic Power Production and Energy Storage Systems in Low-Voltage Power Grids / Solcellsproduktion och energilagringssystem i lågspänningselnät Häggblom, Johan, Jerner, Jonathan January 2019 (has links) In recent years, photovoltaic (PV) power production have seen an increase and the PV power systems are often located in the distribution grids close to the consumers. Since the distributions grids rarely are designed for power production, investigation of its effects is needed. It is seen in this thesis that PV power production will cause voltages to rise, potentially to levels exceeding the limits that grid owners have to abide by. A model of a distribution grid is developed in MathWorks MATLAB. The model contains a transformer, cables, households, energy storage systems (ESS:s) and photovoltaic power systems. The system is simulated by implementing a numerical Forward Backward Sweep Method, solving for powers, currents and voltages in the grid. PV power systems are added in different configurations along with different configurations of ESS:s. The results are analysed, primarily concerning voltages and voltage limits. It is concluded that addition of PV power production in the distribution grid affects voltages, more or less depending on where in the grid the systems are placed and what peak power they have. It is also concluded that having energy storage systems in the grid, changing the power factor of the inverter for the PV systems or lowering the transformer secondary-side voltage can bring the voltages down. / På senare tid har det skett en ökning i antalet solcellsanläggningar som installeras i elnätet och dessa är ofta placerade i distributionsnäten nära hushållen. Eftersom distributionsnäten sällan är dimensionerade för produktion så behöver man utreda effekten av det. I det här arbetet visas det att solcellsproduktion kommer att öka spänningen i elnätet, potentiellt så mycket att de gränser elnätsägarna måste hålla nätet inom överstigs. En modell över lågspänningsnätet skapas i MathWorks MATLAB. Modellen innehåller transformator, kablar, hushåll, energilager och solcellsanläggningar. Systemet simuleras med hjälp av en numerisk Forward Backward Sweep-lösare som beräknar effekter, strömmar och spänningar i elnätet. Solcellanläggningarna placeras ut i elnätet i olika konfigurationer tillsammans med olika konfigurationer av energilager. Resultaten från simuleringarna analyseras främst med avseende på spänningen i elnätet utifrån dess gränser. De slutsatser som dras i arbetet är att solcellsproduktion kommer att påverka spänningen, mycket beroende på var i elnätet anläggningarna placeras och storleken hos dem. Det visas också att energilager, justering av effektfaktor hos solcellsanläggningarna eller en spänningssänkning på transformatorns lågspänningssida kan få ner spänningen i elnätet. / <p>LiTH-ISY-EX--19/5194--SE</p> electric power power flow analysis radial distribution system low-voltage power grid forward backward sweep method photovoltaic power systems energy storage systems power factor elkraft effektflödesanalys radiella distributionsnät lågspänningselnät forward backward sweep-metod solcellsanläggningar energilagringssystem effektfaktor Annan elektroteknik och elektronik
112	Anpassning av småskaliga vattenkraftverk för ö-drift av lokalt elnät / Adapting small hydropower plants for frequency control of power grids in island mode Fredriksson, Jonatan January 2019 (has links) This master thesis examines technical requirements for small hydro power plants (HPP) to operate proximate parts of the power grid in island mode. The work examines how small hydropower can be modified and complemented with additional technologies to achieve sufficient frequency control capabilities. A case study was performed within the concession area of power grid operator Ålem Energy. One of the HPPs, located in Skälleryd, is owned by Ålem Energy and became the focal point of the study. Relevant parts of the concession area were surveyed for properties such as system inertia, electric load and available power. Furthermore, a model of Kaplan turbine 1 in Skälleryd HPP was created with the purpose of studying the benefits of bypassing regulation control from the wicket gates directly to the runner. The method was tested in an off-grid islanding test. Frequency control of the turbine was tested powering electric heaters and, using a new method, controlling a virtual power grid. Finally, a theory was developed to estimate the transient disturbance resilience (TDR) of a power grid. The theory was applied to the HPP in Skälleryd to suggest modifications for the plant to achieve sufficient islanding capabilities. The survey of the power system revealed a promising potential for the HPPs to operate in island mode, especially at later stages when the grid spans several HPPs for more system inertia. The available power from the HPPs was however strongly seasonal which imposes flexibility on a future plan of action for engaging the grid in island mode. The method of controlling the turbine power from the runner proved to have several difficulties. Firstly, the current hydraulics system was not able to freely control the runner as the hydrodynamic forces on the runner blades were too large. Secondly, the method was found to be unstable due to inherent amplification of speed deviations. Furthermore, the low inertia at Skälleryd is likely detrimental to the lone frequency control of the turbine. Therefore other methods for improving frequency control were suggested. The developed theory for TDR was used to create charts describing the TDR for various combinations of system inertia and regulation speed. By studying the proprieties of Skälleryd HPP in the charts the necessary modifications could be rationally chosen. A frequency regulating dummy load was found to be the simplest option. A control scheme was suggested with the dummy load performing primary frequency control and the turbines at Skälleryd performing secondary control, restoring the dummy load to its nominal state. small hydropower hydropower Kaplan turbine transient disturbance resilliance power grid island islanding adapting island mode frequency control dummy load Kaplan Kaplanturbin elnät ö-nät ö-drift vattenkraft småskaliga vattenkraftverk transient störningstålighet indexprov kombineringsprov lokalt elnät Energy Systems Energisystem Energy Engineering Energiteknik
113	Приступи развоју базe података Општег информационог модела за електроенергетске мреже / Pristupi razvoju baze podataka Opšteg informacionog modela za elektroenergetske mreže / Approaches for Developing a Database for Common Information Model of Power Grids Dević Saša 01 March 2019 (has links) <p>Општи информациони модел (CIM) користи се за опис електроенергетске мреже и за размену података између оператера преносних електроенергетских система. Како је модел постајао све заступљенији, појавила се потреба за његовим складиштењем. У раду је развијен методолошки приступ за развој базе података која би подржала релативно једноставно складиштење и рад са инстанцама CIM модела, које описују тренутно, активно стање у систему. Такође, омогућено је и праћење претходних, историјских стања CIM инстанци, као и њихова рестаурација у жељено стање. Очекује се да предложени приступ олакша увођење CIM модела у различита, наменска програмска решења.</p> / <p>Opšti informacioni model (CIM) koristi se za opis elektroenergetske mreže i za razmenu podataka između operatera prenosnih elektroenergetskih sistema. Kako je model postajao sve zastupljeniji, pojavila se potreba za njegovim skladištenjem. U radu je razvijen metodološki pristup za razvoj baze podataka koja bi podržala relativno jednostavno skladištenje i rad sa instancama CIM modela, koje opisuju trenutno, aktivno stanje u sistemu. Takođe, omogućeno je i praćenje prethodnih, istorijskih stanja CIM instanci, kao i njihova restauracija u željeno stanje. Očekuje se da predloženi pristup olakša uvođenje CIM modela u različita, namenska programska rešenja.</p> / <p>Common Information Model (CIM) is used for describing power grid networks<br />and data exchange among transmission system operators (TSO). As the<br />model became widely used, there was a need to store such model. In this<br />thesis we present a methodological approach to development of a database<br />that supports relatively easy storing and managing CIM instances, which<br />describe current, active state of the system. Also, tracking changes and<br />restoring CIM instances to its previous states are supported. We expect that<br />such methodological approach would ease the implementation of CIM model<br />in various, domain specific software solutions.</p>
114	Modeling and Analysis of Large-Scale On-Chip Interconnects Feng, Zhuo 2009 December 1900 (has links) As IC technologies scale to the nanometer regime, efficient and accurate modeling and analysis of VLSI systems with billions of transistors and interconnects becomes increasingly critical and difficult. VLSI systems impacted by the increasingly high dimensional process-voltage-temperature (PVT) variations demand much more modeling and analysis efforts than ever before, while the analysis of large scale on-chip interconnects that requires solving tens of millions of unknowns imposes great challenges in computer aided design areas. This dissertation presents new methodologies for addressing the above two important challenging issues for large scale on-chip interconnect modeling and analysis: In the past, the standard statistical circuit modeling techniques usually employ principal component analysis (PCA) and its variants to reduce the parameter dimensionality. Although widely adopted, these techniques can be very limited since parameter dimension reduction is achieved by merely considering the statistical distributions of the controlling parameters but neglecting the important correspondence between these parameters and the circuit performances (responses) under modeling. This dissertation presents a variety of performance-oriented parameter dimension reduction methods that can lead to more than one order of magnitude parameter reduction for a variety of VLSI circuit modeling and analysis problems. The sheer size of present day power/ground distribution networks makes their analysis and verification tasks extremely runtime and memory inefficient, and at the same time, limits the extent to which these networks can be optimized. Given today?s commodity graphics processing units (GPUs) that can deliver more than 500 GFlops (Flops: floating point operations per second). computing power and 100GB/s memory bandwidth, which are more than 10X greater than offered by modern day general-purpose quad-core microprocessors, it is very desirable to convert the impressive GPU computing power to usable design automation tools for VLSI verification. In this dissertation, for the first time, we show how to exploit recent massively parallel single-instruction multiple-thread (SIMT) based graphics processing unit (GPU) platforms to tackle power grid analysis with very promising performance. Our GPU based network analyzer is capable of solving tens of millions of power grid nodes in just a few seconds. Additionally, with the above GPU based simulation framework, more challenging three-dimensional full-chip thermal analysis can be solved in a much more efficient way than ever before.
115	Modélisation haute fréquence des convertisseurs d'énergie : application à l'étude des émissions conduites vers le réseau / High frequency modeling of power converters : application to the study of conducted emissions toward the power grid Moreau, Maxime 07 December 2009 (has links) Ces travaux de recherche portent sur la problématique CEM (Compatibilité Electromagnétique) en électronique de puissance. Cette étude s'intéresse particulièrement à la modélisation HF (haute fréquence) des convertisseurs d'énergie dans le but d'étudier la propagation des perturbations conduites vers le réseau avec ou sans l’utilisation du RSIL (Réseau Stabilisateur d'Impédance de Ligne). Une première partie présente les outils de modélisation des sources de perturbation dans les convertisseurs statiques.La seconde partie est consacrée à la modélisation HF d'un système d'entraînement à vitesse variable. L'onduleur de tension triphasé est représenté par trois générateurs équivalents afin de reconstituer le découpage des tensions de sortie. Un modèle HF du câble blindé de 4 conducteurs tenant compte de la dissymétrie est ensuite proposé. Les résultats de simulation ont été validés par des relevés expérimentaux. La comparaison montre qu'il est possible de modéliser correctement le comportement HF du dispositif jusqu'à 20MHz.Une troisième partie porte sur la propagation des perturbations conduites vers le réseau sans RSIL. Il a fallu pour cela déterminer et modéliser l'impédance du réseau. L'influence du pont redresseur à diodes sur la propagation des perturbations de mode commun a ensuite été étudiée. Les résultats de simulation montrent que l'impact de ces perturbations sur la tension réseau est prépondérant lorsque le pont redresseur est à l'état bloqué. Les résultats expérimentaux ont permis de valider cette étude. Ce travail se termine par une étude préliminaire sur l'association de deux convertisseurs connectés localement à une même source d'énergie / These research works focus on EMC (Electromagnetic Compatibility) in power electronics systems. Specifically, the study focuses on HF (high frequency) modeling of the power converters in order to study the conducted emissions toward the power grids with or without the use of an LISN (Line Impedance Stabilisation Network). The first part presents the modeling tools of the electromagnetic emissions sources in power converters.The second part describes the HF modeling method of an adjustable speed drive (ASD) that will be used to estimate the conducted emissions. In a first part, a behavioural model of PWM inverter is proposed as an EMI noise source. Then, a model of the shielded 4-wire energy cable that taking into account of the dissymmetry structure is proposed and validated in the frequency domain for two different lengths. The comparison of measurement and simulation results of conducted emissions (with LISN) shows the good compromise between the simulation duration and accuracy of the results.A third part is dedicated to the propagation of conducted emissions toward the power grid without using a LISN. The first stage consists in proposing a model impedance of the network impedance. The influence of the bridge rectifier diodes on the propagation paths of common mode disturbances has been studied in the second step. The simulation results show that the impact of these disturbances on the network voltage is more important when the bridge rectifier is normally off-state. The experimental results have validated this study. This work concludes with a preliminary study on the association of two converters connected locally to a single energy source Compatibilité électromagnétique Convertisseurs d'énergie Couplage parasite Modélisation haute fréquence Impédance haute fréquence du réseau Analyse temps/fréquence Electromagnetic compatibility Power converter Parasitic coupling Conducted electromagnetic interferences High frequency modelisation High frequency impedance power grid Time domain/frequency domain analysis
116	Operation of Three Phase Four Wire Grid Connected VSI Under Non-Ideal Conditions Ghoshal, Anirban January 2013 (has links) (PDF) The necessity to incorporate renewable energy systems into existing electric power grid and need of efficient utilization of electrical energy are growing every day. A shunt connected Voltage Source Inverter(VSI) capable of bidirectional power flow and fast control has become one of the building block to address such requirements. However with growing number of grid connected VSI, new requirements related to harmonic injection, higher overall efficiency and better performances during short term grid disturbances have emerged as challenges. For this purpose a grid connected three phase four wire VSI with LCL filter can be considered as a general module to study different control approaches and system behavior under ideal and non-ideal grid conditions. This work focuses on achieving enhanced performance by analyzing effect of non-ideal conditions on system level and relating it to individual control blocks. In this work a phase locked loop structure has been proposed which is capable of extracting positive sequence fundamental phase information under non-ideal grid conditions. It can also be used in a single phase system without any structural modification. The current control for the three phase four wire VSI system has been implemented using Proportional Resonant (PR) controller in a per phase basis in stationary reference frame. A simplified controller design procedure based on asymptotic representation of the system transfer function is proposed. Using this method expressions for controller gains can be derived. A common mode model of the inverter system has been derived for low frequencies. Using this model a controller is designed to mitigate DC bus imbalance caused by sensor and ADC channel offsets. A multi-rate approach for digital implementation of PR controller with low resource consumption, that is suitable for an FPGA like digital controller ,is proposed. This multi-rate method can maintain resonance frequency accuracy even at low sampling frequency and can easily be frequency adaptive. Anti-wind up methods for PI controller have been studied to find suitable anti-wind up methods for PR controller. The tracking anti-wind up method is shown to be suitable for use with a PR controller. The effectiveness of this method under sudden disconnection and reconnection of VSI from grid is experimentally verified. A resonant integrator based second order filter is shown to be useful for active damping of LCL filter resonance with a wide range of grid inductance variation. The proposed method utilizes the LCL filter capacitor voltage to estimate resonance frequency current. Suitability of fundamental current PR controller for active damping alone, and with the proposed method show the superiority of the proposed method especially for low switching frequencies. Design oriented analysis of the above topics are included in the thesis. The theoretical understandings developed have been verified through experiments in the laboratory and can be readily implemented in industrial power electronic systems. Voltage Source Inverters Grid Connected Voltage Source Inverters Phase Locked Loop (PLL) Proportional Resonant Controller LCL Filters LCL Resonance Proportional Resonant Controller Electric Power Grid Power Electronic Converters Power Electronics Renewable Energy Sources Grid connected VSI Filter Resonance Electrical Engineering
117	Vliv decentrálních zdrojů na provozování distribuční soustavy 110 kV E.ON / The impact of distributed generation on 110 kV distribution system E.ON Hajdú, Lukáš January 2011 (has links) This Master´s thesis deals with problematics related to the connection of new decentralized power sources into electrical power grid. Due to advantageous legislative support of these new, especially photovoltaic power sources, a massive amount of these sources have been connected into the power grid between years 2009 and 2010. For theoretical understanding of processes during a steady-state, the initial parts of this paper are focused on a procedure which solves steady-state on every power line mentioned. When we speak of decentralized power sources connection, it is necessary to mention the connected legislative. National distribution grid operators in collaboration with national regulatory commission have decided on a legislative document Rules of distribution grid operation, which puts a set of demands and requirements on applicants wishing to connect a new power source to the grid. The text of this thesis is focused mainly on demands required after the latest change in 1/2010. Practical part of this work deals with verification of new power source influence on a related power grid and meeting the legislatively required demands. The most important demands are voltage change due to new power source operation and its transfer to other voltage levels, higher harmonics injection, power output fluctuation and last, not least, changes in load flow directions. For reasons previously mentioned an analysis is made and possibilities of reducing or removing of these influences are introduced. To achieve these goals, two computer programs, Siemens Sinaut Spectrum and NetCalc are used.
118	Systém řízení báze dat v operační paměti / In-Memory Database Management System Pehal, Petr January 2013 (has links) The focus of this thesis is a proprietary database interface for management tables in memory. At the beginning, there is given a short introduction to the databases. Then the concept of in-memory database systems is presented. Also the main advantages and disadvantages of this solution are discussed. The theoretical introduction is ended by brief overview of existing systems. After that the basic information about energetic management system RIS are presented together with system's in-memory database interface. Further the work aims at the specification and design of required modifications and extensions of the interface. Then the implementation details and tests results are presented. In conclusion the results are summarized and future development is discussed.
119	Designing Electric Vehicle Charging Station Information Algvere, Caroline January 2020 (has links) The electric vehicle industry is under rapid development and the fleet of chargeable cars in society is increasing fast. As a result, a high demand for public chargers has emerged. Simultaneous to the expansion of the electric vehicle fleet and charging infrastructure the power grid is occasionally highly strained. Additionally, factors like cities expanding and the digitization of society also have a large effect on the power grid. This master's thesis investigates the characteristics of electric vehicle users and presents a prototype of an information display for electric vehicle charging stations. The design is is based on the user studies and founded in theory about sustainable user behaviour with the goal of encouraging behaviours that minimize the strain on the local power grid of Uppsala. It concerns the research topic of how to design for sustainable behaviour and address research questions of how to design electric vehicle charging station information to communicate multiple charging alternatives to a broad variety of users. The work reveals that electric vehicle users suffer from the charging infrastructure being underdeveloped, feel frustration towards payment solutions available and lack information regarding electric vehicle use. Also, electric vehicle user's common passion for tech and environmental consciousness are revealed in the study. These facts are used as the foundation for the mobile application design prototype suggested. Electric Vehicle EV Charging Station Information Charging Infrastructure Power Grid Behaviour-Guiding Technology Persuasive Design Designing for Sustainable Behaviour Qualitative Research Thematic Analysis Human-Computer Interaction HCI User-Centered Design UCD User Experience design UX-Design Computer and Information Sciences Data- och informationsvetenskap
120	Utvecklingen av marknadsvärdet för svenska frekvenshållningsreserver 2024–2030 : En prognos för utvecklingen av marknadsvärdet för frekvenshållningsreserverna FCR-N, FCR-D upp och FCR-D ned på den svenska balansmarknaden mellan 2024 och 2030 / The Development of the Market Value of Swedish Frequency Containment Reserves 2024–2030 : A forecast for the development of the market value for the frequency containment reserves FCR-N, FCR-D up and FCR-D down in the Swedish balancing market between 2024 and 2030 Ludvig, Aldén, Gustav, Espefält, Gabriel, Gabro January 2024 (has links) I takt med en ökad andel variabel förnybar elproduktion i Sveriges energimix blir elnätets flexibilitet allt viktigare för att upprätthålla en stabil elförsörjning. Detta arbete undersöker framtida prognoser för priser och volymer på de svenska frekvenshållningsreserverna FCR-N, FCR-D upp och FCR-D ned fram till år 2030. Prognoser för sådan utveckling är viktiga för elmarknadens aktörer och deras beslut att investera i flexibilitetsresurser. SARIMAX-modeller utvecklades baserade på historisk data och antaganden om framtida utvecklingar, vilka i sin tur grundades på en intervju med en branschexpert samt aktuella kartläggningar och rapporter. Resultaten visar på en markant nedåtgående pristrend. För FCR-N prognostiseras priserna sjunka med 367 % från 2024 till 2030, från 29 euro/MW till 5 euro/MW. FCR-D upp förväntas följa en liknande trend med ett prisfall på 325 %, från 20 euro/MW år 2024 till 4 euro/MW år 2030. Den kraftigaste prisnedgången prognostiseras för FCR-D ned, där priserna beräknas rasa med över 1900 % under samma period - från 61 euro/MW år 2024 till endast 3 euro/MW år 2030. Vad gäller volymer visar prognoserna på en relativt stabil utveckling kring upphandlingsplanerna, med en viss ökning för FCR-D ned på 44 % från 2024 till 2030. Den pågående etableringen av batterilager förutses ha stor påverkan genom att öka konkurrensen och pressa priserna nedåt. De låga prisnivåerna 2030 kan dock göra det utmanande att motivera investeringar enbart baserat på intäkter från FCR-marknader. Vidare diskuteras modellernas begränsningar samt behovet av framtida forskning kring batteriteknik, råvaruaspekter och avancerade simuleringsmodeller för att bättre förstå marknadsdynamiken. / As the share of variable renewable electricity production increases in Sweden's energy mix, the flexibility of the power grid becomes increasingly important to maintain a stable electricity supply. This study aims to forecast prices and volumes of the Swedish frequency containment reserves FCR-N, FCR-D up, and FCR-D down until 2030. Forecasts of such developments are important for electricity market participants and their decisions to invest in flexibility resources. SARIMAX models were developed based on historical data and assumptions about future developments, which in turn were based on an interview with an industry expert as well as current reports. The results indicate a significant downward price trend. For FCR-N, prices are forecasted to decrease by 367% from 2024 to 2030, dropping from 29 euros/MW to 5 euros/MW. FCR-D up is expected to follow a similar trend with a 325% price drop, from 20 euros/MW in 2024 to 4 euros/MW in 2030. The sharpest price decline is forecasted for FCR-D down, where prices are estimated to plummet by over 1900% during the same period - from 61 euros/MW in 2024 to only 3 euros/MW in 2030. Regarding volumes, the forecasts show a relatively stable development around the procurement plans, with a certain increase for FCR-D down by 44% from 2024 to 2030. The ongoing establishment of battery storage is expected to have a major impact by increasing competition and putting downward pressure on prices. However, the low price levels in 2030 may make it challenging to justify investments based solely on revenues from FCR markets. Furthermore, the limitations of the models are discussed, as well as the need for future research on battery technology, raw material aspects, and advanced simulation models to better understand market dynamics. FCR frequency containment reserves FCR-N FCR-D up FCR-D down upregulation downregulation variable renewable energy VRE power grid power system flexibility electricity supply stable forecast electricity market SARIMAX time series modeling data price volume market value energy storage battery storage battery park batteries competition time series flexibility resource flexibility service risk system effect future scenarios scenario balancing market volume development investment decisions scenario analysis uncertainty management sensitivity analysis competitive situation commodity prices technology development policy impact capacity expansion profitability calculations risk management FCR frekvenshållningsreserver FCR-N FCR-D upp FCR-D ned uppreglering nedreglering variabel förnybar energiproduktion VRE elnät kraftsystem flexibilitet elförsörjning stabil prognos elmarknad SARIMAX tidsseriemodellering data pris volym marknadsvärde energilagring batterilager batteripark batterier konkurrens tidsserie flexibilitetsresurs flexibilitetstjänst risk systemeffekt framtidsscenarier scenario balansmarknad volymutveckling investeringsbeslut scenarioanalys osäkerhetshantering känslighetsanalys konkurrenssituation råvarupriser teknologiutveckling policypåverkan kapacitetsutbyggnad lönsamhetsberäkningar riskhantering Energy Systems Energisystem

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