In this thesis it is investigated if it would be technically and economicallypossible to combine wind power and railway feeding. As a case studyBlekinge Kustbana (BKB), a railway section in the south of Sweden ischosen. The thesis includes an extensive power and energy flow analysison the railway section where large-scale wind power production is directlyconnected.When the work of this thesis started it was first of all a three sided convertersolution that should be studied. Where three-sided converter consists of aPWM-converter with the wind power connected to the DC-Iink. But duringthe work it was concluded that this solution is not the best solution for thecase. A better solution is the three-sided transformer, were the wind poweris connected through a third winding to the railway transformer on the 50Hzside.Also different railway feeding systems and their influence on how the windpower can be used are investigated.From the conclusions it can be mentioned that it would be profitable todirectly connect 4.5MW wind power to BKB. / <p>NR 20140805</p>

This thesis has been carried out on behalf of the department of Power Modules at Ericsson. In a telecom system interface A is a physical point between the power supply system and the telecommunication equipment described in a European standard called ETSI EN 300 132-2. This interface is also described in the American standard ATIS-0600315.2007. For board-mounted products, such as DC/DC converters, a well-defined input interface description is lacking. The goal of this thesis was to evaluate if the requirements in the standards ETSI EN 300 132-2 and ATIS-0600315.2007 are viable for the input interface of DC/DC converters. A part of this goal was also to investigate and analyze how the systems, in which the DC/DC converters operate, works. To be able to determine if any of the two standards, ETSI and ATIS, are viable for use for the input interface, both were reviewed and described with focus on voltage levels and transients. In the information gathering phase it became clear that an extended limitation was needed. Therefore, in order to investigate what happens from interface A to the input interface of DC/DC converters, the system used in this thesis is the EBS LOD (Ericsson Blade System – Low Ohmic Distribution). EBS is one of the systems in Core sites. The report describes the construction of EBS where in the PFM (Power Fan Module), backplanes and various boards are important parts. Furthermore some key principles within Core sites, such as HOD (High Ohmic Distribution), LOD, Two-wire system and Three-wire system, are also described in order to explain how the EBS system works. EBS (including PIM (Power Interface Module)) was modeled in OrCad PSpice, with both one board and 26 boards, and was simulated with different transients at an input to the system. The simulation results show that the high voltages never reach the DC/DC converter and that they therefore are well protected from transients in an EBS LOD system. In order to determine whether the standards ETSI and ATIS are viable for the input interface of DC/DC converters, it is concluded that more investigations, tests and simulations are needed. / Detta examensarbete har utförts på uppdrag av avdelningen Power Modules på Ericsson. I ett telekommunikationssystem är gränssnitt A en fysisk punkt mellan kraftsystemet och telekomutrustningen som beskrivs i en europeisk standard som kallas ETSI EN 300 132-2. Detta gränssnitt är också beskrivet i den amerikanska standarden ATIS-0.600.315.2007. För kortmonterade produkter, såsom DC/DC-omvandlare, saknas en beskrivning av ett väldefinierat ingångsgränssnitt. Målet med detta examensarbete var att utvärdera om kraven i standarderna ETSI EN 300 132-2 och ATIS-0.600.315.2007 är applicerbara på ingångsgränssnittet till DC/DC-omvandlare. En del av detta mål var också att utreda och analysera hur systemen, i vilka DC/DC-omvandlare finns, fungerar. För att kunna avgöra om de två standarderna ETSI och ATIS var applicerbara, granskades de och beskrevs med fokus på spänningsnivåer och transienter. I informationsinsamlingsfasen stod det klart att en utökad avgränsning behövdes. Slutsatsen av denna begränsning var att systemet som skulle användas i detta examensarbete var EBS LOD (Ericsson Blade System – Low Ohmic Distribution), för att undersöka vad som händer från gränssnittet A till ingångsgränssnittet av DC/DC omvandlare. EBS är ett av systemen inom Core sites. I rapporten beskrivs konstruktionen av EBS där PFM (Power Fan Module), backplan och olika kort anges som viktiga delar. Dessutom beskrivs några viktiga principer inom Core sites, såsom HOD (High Ohmic Distribution), LOD, Två-ledar-system och Tre-ledar-system. EBS (inklusive PIM (Power Interface Module)) modellerades i OrCad Pspice, med både ett kort och 26 kort, och simulerades med olika transienter på en av ingångarna till systemet. Simuleringsresultaten visar att de höga spänningarna aldrig når DC/DC-omvandlaren och att dessa alltså är väl skyddade mot transienter i ett EBS LOD system. För att kunna avgöra om standarderna ETSI och ATIS är applicerbara på ingångsgränssnittet till DC/DC-omvandlare är slutsatsen att flera utredningar, tester och simuleringar behöver göras.

In motor vehicles the power and information are distributed by their own separate wiresand the amount of wires over the past decades has increased tremendously due to theever increasing electronics onboard. Solely the average weight of the wires has increasedfrom 4 to 91 kg over the last 50 years and it is therefore clear that a remedy to theever increasing wiring is needed. A possible solution to this could be to introducepower line communication (PLC) onboard a vehicle. The PLC aims at overlaying theinformation on top of the already existing power feed cables and thus eliminating theneed of dedicated wires for communication purposes. The PLC solution would thussimplify the wiring network to a bare minimum, since no additional wires besides thepower cables are needed.During this thesis work the PLC technology was studied as a possible cost and qualityreform of the powertrain sensor network, where it could be used to both reduce the costof wires and increase the system reliability.A theoretical background study was rst performed to investigate the limitations andpossibilities of the PLC implemented in a vehicle, and the PLC technology was alsotested upon the DC-lines of an e6 Volvo FMX truck, between the post catalytic NOxsensor and the ACM with two CAN protocol based PLC modems. The throughput, noiseand the scalar voltage gain was measured in this link with the ignition key at dierentpositions to test dierent modes of operations. It was shown that this particular link hada clear low pass characteristics with severe voltage attenuation without any signicantdierence caused by the dierent modes of operation. The severe characteristics of thelink did result into a fault connement mode of the CAN based PLC modems wheretheir communication capabilities were inhibited, which shows that at least with thisparticular link, reliable communication was not possible with the equipment at hand.Short EMC measurements were also carried out regarding the radiated emissions. Theresults showed that the PLC technology implemented in the existing wiring architecturecould be a possible cause of EMC problems if no counter actions are been taken intoaccount.Some of the economical aspects were also investigated, but most of the results were leftas hypothetical assumptions. A detailed cost saving analysis was nevertheless made onthe EATS-wire harness where the savings were estimated to be 1e. It is the hope thatthese calculations could be used as a sounding board for future PLC wire harness costanalysis.

Thanks to growing environmental concerns, renewable energies take a higher andhigher share of electricity generating portfolios. In Germany particularly, the installedcapacity of wind and solar plants has increased continuously for the past ten years. Given theprinciple of the merit-order dispatch, a greater use of wind and solar power allows theelectricity spot prices to drop significantly. However, wind and sun are both intermittentresources, and this leaves great room for uncertainties on prices. As a consequence, pricesbecome much more dependent on the weather conditions and show greater volatilities,making hedging much more difficult. At the same time, the mechanism of market coupling inthe Central West Europe (France, Germany, Benelux) goes toward a harmonization of prices.As such, the cross-border interconnections play a decisive role in the electricity pricing.This paper deals with the actual influence of the interconnections between France andGermany on electricity spot prices when renewable energies are added to the energy mix. Amodel of a French-German market is made in order to see the impact of an increasingpenetration of renewable energies on spot prices. The wind and solar generations aremodelled using artificial neural networks, ANN. Multiple linear regression is employed tomodel the French and German loads. The cross-border interconnections are modelled basedon the capacity allocations published by RTE (the national French grid operator) and finallythe French and German prices are modelled with a GARCH process to study the volatilities.The study is made for three different scenarios: the reference scenario, with a penetration ofrenewable energies as seen in 2012, a 2020 scenario, with a penetration of renewable energiesas predicted in 2012, and a 2020 scenario with increased interconnection capacities betweenFrance and Germany.Running the models shows that a higher penetration of renewable energies lowers spotprices in average, but introduces price spikes that did not exist beforehand. On short periodsof observation, the volatility seems to decrease, but on longer periods, the spikes increase thevolatility. Also, increasing the interconnection capacities does make the prices converge, butto a certain extent only.Finding fitting hedging strategies becomes more delicate when prices vary with suchuncertainty. The study could be more developed (by extending it to the whole Europeancontinent) in order to get a more accurate vision of how energy markets will look like in a fewyears. However, it must be understood that the future scenarios depend on many variablefactors, and no mathematical model is able to capture all those factors accurately.

This thesis presents an algorithm for finding the minimal interruptioncost associated with the loads.Electric power systems are necessary to transfer electric energy fromproducers to consumers. The power system may lose stability as thesenonlinear systems are subject to contingencies. The loss of stabilitymay result in large costs for the society, by the loss of productivityand worsening standard of living. If the likelihood of instability is low,then it may be that it is not economically motivated to allocate costlyresources necessary to prevent this from happening. For some casesload shedding is the alternative with best economical performance, torestore the stability and ensure that delivery of power is not interrupted.With increasing amounts of renewables in a power system, the planningand scheduling of the electric power production will get more difficultto forecast and control. Therefore the system operators will needto be able to handle more diverse situations than before. Thus thereis a need to find computationally efficient methods to predict systemstability and the minimal load shedding needed.This report uses second-order approximations to the stability boundariesof the system, developed and calculated by Magnus Perninge andCamille Hamon to determine how much and where the load sheddingshould be done to shed the minimal amount of load that restores thestability of the system.Two cases, the IEEE 9-bus system and the IEEE 39-bus system,illustrates the proposed method and compares three different methodsused to determine the load shedding. The results show that the approximationscan be used to minimize the load shedding, and that theamount of load shed is significantly reduced. Time-domain simulationsof the system were necessary to ensure the stability of the system anddetermine of much margin that is needed to the approximations.The methods and approximations used in this report could in thefuture be applied to real power systems, a possible application is tocalculate the severity of contingencies and use the information to minimizethe total costs of the system when considering operation andinvestments. Another possible application is to design automatic loadshedding controllers using wide-area monitoring to increase the systemreliability. / I detta examensarbete presenteras en algoritm för att finna de minimalaavbrottskostnaderna för lasterna i elkraftssystem.Elkraftssystem kallas de system som har till uppgift att möjliggöraöverföring av elektrisk energi från producenter till konsumenter. Dessasystem är icke-linjära och kan under vissa förhållanden bli instabilaoch göra hela eller delar av elnätet strömlöst, vilket medför stor samhälleligpåverkan i form av försämrad levnadsstandard och kostnaderför produktionsbortfall. Dock är det inte alltid ekonomiskt lönsamt attlägga betydande resurser på att förhindra att systemet blir instabilt,om sannolikheten för att detta händer är låg.Att koppla bort last vid kritiska situationer, till exempel vid fel påviktiga kraftledningar, kan därför i vissa fall vara det mest ekonomiskaalternativet för att undvika att systemet blir instabilt. En ökande andelförnybar energi i ett elkraftssystem gör produktion av elektrisk energimer svårprognosticerad och svårstyrd. Därför bör man ta hänsyn till ettbredare urval situationer än tidigare för att kunna bedöma stabilitetenhos systemet. Detta ställer krav på snabba metoder för att bedömasystemets stabilitet och beräkna vilka lastbortkopplingar som krävs.Denna rapport utnyttjar andragradsapproximationer till stabilitetsgränsernaför systemet utvecklade och beräknade av Magnus Perningeoch Camille Hamon för att kunna bestämma var och hur mycket lastsom ska kopplas bort, så att systemet återfår sin stabilitet för en såliten mängd last bortkopplad som möjligt. Genom simuleringar beräknasdärefter hur mycket marginal till stabilitetsgränserna som krävs föratt återge systemet transienta stabilitet.Två fallstudier, ett för IEEEs 9-nods system och ett för IEEEs 39-nods system, illustrerar metoden och jämför den med två andra metoder,för att undersöka metodens prestanda. Resultaten visar hur den föreslagnaalgoritmen minimerar lastbortkopplingen jämfört med de andrametoderna, och att mängden last som blir bortkopplad minskar betydligt.Simuleringar av systemet behövdes för att undersöka systemetsstabilitet och bestämma hur mycket marginal till ytorna som krävs.Metoderna och approximationerna som utnyttjades i denna rapportskulle kunna användas i verkliga elkraftssystem, en tillämpning vore attminimera kostnaderna för systemet genom att ranka hur allvarliga feli systemet är, vilket kan utnyttjas för att minimera kostnader för driftoch investeringar. En annan möjlig tillämpling är automatisk lastbortkopplingför att minimera de kostnader som uppstår om systemet blirinstabilt.

Renewable generation is the fastest growing energy resources in the past decade. Renewable energy sources, particularly wind power, provide clean and environmentally friendly energy to meet the system demand, meanwhile introducing huge levels of uncertainty in the system. On the one hand the deregulated electric power industry and on the other hand the intermittent nature of renewable energy sources cause highly volatile and uncertain electricity prices in different market places. This will create challenges for economical operation and planning of the flexible energy sources, particularly hydropower, which being a flexible energy source is the best option to balance wind power variation. The main purpose of this work is to develop optimal short-term planning models for price taker hydropower producer working in the existing environment. Those models have to deal with the huge level of uncertainties the wind power introduces into the power system. An optimization tool known as stochastic optimization is used to plan hydropower production under uncertainties. The first model, which is used to make sensitivity analysis, is a twostage stochastic linear programming problem. The uncertainties are handled by generating scenarios based on historical data. Profound sensitivity analysis is provided, in terms of volatility in day-ahead market prices and water inflow level as well as in terms of water opportunity cost and initial volume of the reservoir. Based on the comparison of the stochastic and corresponding deterministic problems, the result aims to show the impact of modeling the uncertainties explicitly. The results show that for the short-term hydropower planning problems the effect of considering price uncertainty in the stochastic model is higher compared with considering inflow level uncertainty. The second model used in this work is a two-stage stochastic linear programming problem. The model generates optimal bids to day-ahead market considering real-time market price uncertainties. While simultaneously bidding to both markets, the results for most of the hours suggest two actions; either to bid the available amount of energy to upward regulation market or to bid the maximum capacity to day-ahead market and bring back the whole amount making down regulation. To make the bidding strategies more flexible and robust different approaches are modeled and assessed. Finally one of the approaches is suggested as the most applicable one. / <p>QC 20121109</p>

QC 20111205

Society has become increasingly dependent on electricity, so power system reliability is of crucial importance. However, while underinvestment leads to an unacceptable number of power outages, overinvestment will result in costs that are too high for society. The challenge is to find a socioeconomically adequate level of risk. In this risk assessment, not only the probability of power outages, but also the severity of their consequences should be included.   A risk assessment can be performed from either the perspective of customers or the perspective of the grid owner, depending on whether the consequences faced by customers or the grid owner are considered. Consequences of power outages are usually measured through interruption costs. Examples of interruption costs for the grid owner are customer compensations and loss of goodwill. Examples of interruption costs for customers are retail losses for commercial customers and loss of heating and lighting for residential customers. The aim of this thesis is to develop methods for assessing risks in power distribution systems from the customer-oriented perspective. From this perspective realistic assessments of customer interruption costs are essential.   To perform a customer-oriented risk assessment of a distribution system three different models are required: a customer interruption cost model, a load model and a reliability model. The customer interruption cost model describes the consequences, or costs, of power outages that customers face. The load model predicts the loss of load and the energy not supplied due to power outages. The reliability model describes component failures, which are the root causes of power outages, and the restoration processes that follow. The three models can be used together in a cost-benefit analysis to investigate the consequences for customers due to different investment alternatives.   In this thesis a set of new models is developed that incorporates time dependencies in customer interruption costs, load and component failures. The timing of the outage has an impact on the consequences customers face. Severe weather, which is a main contributor to component failures, is generally more common during certain seasons. These facts imply that there may be a correlation between high customer interruption costs and an increased risk for power outages. In Sweden the frequency of storms is higher during the cold period of the year when the demanded load and customer interruption costs are also high. By taking time dependencies into account, the correlation between high interruption costs and elevated risk for power outages is captured.   Results from the risk assessments of two test distribution systems using the models developed in this thesis show that taking time dependencies into account has a considerable impact on the estimation of customer interruption costs and energy not supplied due to outages. To evaluate the risks of extreme costs, the tools Value-at-Risk and Conditional Value-at-Risk which are commonly used in the finance industry are applied. A conclusion that can be drawn from the simulation results is that taking time dependencies into account is especially important when considering extreme outage events that give rise to extreme costs. / Samhället blir allt mer elberoende och leveranssäkerhet av el är av yttersta vikt. Medan underinvesteringar leder till ett oacceptabelt antal elavbrott medför dock överinvesteringar för höga kostnader för samhället. Utmaningen är därför att hitta en samhällsekonomisk lönsam risknivå. I en riskanalys måste inte bara hänsyn tas till sannolikheten för elavbrott utan också avbrottens konsekvenser.   En riskanalys kan genomföras från antingen kundernas eller nätägarens perspektiv beroende på om det är kundernas konsekvenser eller nätägarnas konsekvenser av elavbrott som tas med i analysen. Konsekvenser av elavbrott mäts oftast i avbrottskostnader. Exempel på avbrottskostnader som drabbar nätägaren är goodwill-förluster och ersättning till kunder som har haft långa elavbrott. Exempel på avbrottskostnader som drabbar kunder är förlorade försäljningsintäkter för handel- och tjänsteföretag och uteblivna möjligheter till uppvärmning och belysning för hushåll. Avhandlingens syfte är att utveckla metoder för riskanalys av eldistributionsnät utifrån kundperspektivet. Centralt i detta perspektiv är realistiska uppskattningar av kundavbrottskostnader.   För att kunna genomföra en riskanalys från kundperspektivet krävs tre modeller: en kundavbrottskostnadsmodell, en belastningsmodell och en tillförlitlighetsmodell. Kundavbrottskostnadsmodellen beskriver konsekvenserna, eller kostnaderna, för kunderna av elavbrott. Belastningsmodellen modellerar icke-levererad energi och effekt på grund av elavbrott. Tillförlitlighetsmodellen beskriver fel- och lagningsprocessen för de olika komponenterna i elnätet. De tre modellerna kan kombineras i en kostnad/nytta-analys för att beskriva konsekvenserna för kunder av olika investeringsalternativ.   I denna avhandling utvecklas tre nya modeller som tar hänsyn till tidsberoenden i kundavbrottskostnader, belastning samt komponenters fel- och lagningsprocess. Tidpunkten för avbrottet har stor betydelse för vilka konsekvenserna blir för kunderna. Vidare är oväder, som ofta orsakar elavbrott, i regel mer koncentrerade till vissa årstider. Dessa fakta medför att det kan finnas en korrelation mellan höga kundavbrottskostnader och en ökad risk för elavbrott. I Sverige är vinterstormar vanligast och på vintern är även belastningen och avbrottskostnaden som högst. Genom att ta hänsyn till tidsberoenden fångas korrelationer mellan höga avbrottskostnader och en ökad haveririsk.   Med hjälp av de tre utvecklade modellerna genomförs riskanalyser av två fiktiva distributionsnät. Resultaten från analyserna visar att det ger en stor inverkan på den uppskattade kundavbrottskostnaden och den icke-levererade energin om hänsyn tas till tidsvariationer. För att utvärdera risken för extrema kostnader används två riskverktyg från finansbranschen: Value-at-risk och Conditional Value-at-risk. En slutsats från tillämpningen av riskverktygen är att tidsberoenden är speciellt viktiga att beakta om fokus ligger på de extrema händelser som ger upphov till extrema kostnader. / QC 20101102

Silicon carbide (SiC) is a semiconductor that provides significant advantages for high-power and high-temperature applications thanks to its wide bandgap, which is several times larger than silicon. The resulting high breakdown field, high thermal conductivity and high intrinsic temperature (well above 600 °C) allow high temperature operation of SiC devices and relaxed cooling requirements. In particular, SiC bipolar junction transistors (BJTs) are suitable for high temperature integrated circuits (ICs), due to the absence of a gate oxide. This work focuses on design, fabrication and characterization of the first 4H-SiC integrated circuits realized at KTH. It deals with basic bipolar ICs suitable for high temperature and low voltage applications. Operation up to 300 °C of low-voltage 4H-SiC NPN bipolar transistors and digital integrated circuits based on emitter coupled logic (ECL) has been demonstrated. In the temperature range 27 - 300 °C stable noise margins of about 1 V have been achieved for a 2-input OR-NOR gate operated on -15 V supply voltage, and an oscillation frequency of about 2 MHz has been observed for a 3-stage ring oscillator. The possibility of realizing PNP transistors and passive devices in the same process technology has also been investigated. / QC 20120131

With recent advances in power electronic technology, High-Voltage Direct Current (HVDC) transmission system has become an alternative for transmitting power especially over long distances. Multi-Terminal HVDC (MTDC) systems are proposed as HVDC systems with more than two terminals. These systems can be geographically wide. While in AC grids, frequency is a global variable, in MTDC systems, DC voltage can be considered as its dual. However, unlike frequency, DC voltage can not be equal across the MTDC system. Control of DC voltage in MTDC systems is one of the important challenges in MTDC systems. Since the dynamic of MTDC system is very fast, DC voltage control methods cannot rely only on remote information. Therefore, they can work based on either local information or a combination of local and remote information. In this thesis, first, the MTDC system is modeled. One of the models presented in this thesis considers only the DC grid, and effects of the AC grids are modeled with DC current sources, while in the other one, the connections of the DC grid to the AC grids are also considered. Next, the proposed methods in the literature for controlling the DC voltage are described and in addition to these methods, some control methods are proposed to control the DC voltage in MTDC system. These control methods include two groups. The first group (such as Multi-Agent Control methods) uses remote and local information, while the second group (such as Sliding Mode Control and H¥ control) uses local information.The proposed multi-agent control uses local information for immediate response, while uses remote information for a better fast response. Application of Multi-Agent Control systems leads to equal deviation of DC voltages from their reference values. Using remote information leads to better results comparing to the case only local information is used. Moreover, the proposed methods can also work in the absence of remote information. When AC grid is considered in the modeling, the MTDC system has anon-linear dynamic. Sliding Mode Control, a non-linear control method with high disturbance rejection capability, which is non-sensitive to the parameter variations, is applied to the MTDC system. It controls the DC voltage very fast and with small or without overshoot. Afterward, a static state feedback H¥ control is applied to the system which minimizes the voltage deviation after a disturbance and keeps the injected power of the terminals within the limits. Finally, some case studies are presented and the effectiveness of the proposed methods are shown. All simulations have been done in MATLAB and SIMULINK. / <p>QC 20140911</p>